[PATCH v7 0/8] IMA: support for measuring kernel integrity critical data

[PATCH v7 0/8] IMA: support for measuring kernel integrity critical data

[Tushar Sugandhi]

IMA measures files and buffer data such as keys, command-line arguments
passed to the kernel on kexec system call, etc. While these measurements
are necessary for monitoring and validating the integrity of the system,
they are not sufficient. Various data structures, policies, and states
stored in kernel memory also impact the integrity of the system.
Several kernel subsystems contain such integrity critical data -
e.g. LSMs like SELinux, AppArmor etc. or device-mapper targets like
dm-crypt, dm-verity, dm-integrity etc. These kernel subsystems help
protect the integrity of a device. Their integrity critical data is not
expected to change frequently during run-time. Some of these structures
cannot be defined as __ro_after_init, because they are initialized later.

For a given device, various external services/infrastructure tools
(including the attestation service) interact with it - both during the
setup and during rest of the device run-time. They share sensitive data
and/or execute critical workload on that device. The external services
may want to verify the current run-time state of the relevant kernel
subsystems before fully trusting the device with business critical
data/workload. For instance, verifying that SELinux is in "enforce" mode
along with the expected policy, disks are encrypted with a certain
configuration, secure boot is enabled etc.

This series provides the necessary IMA functionality for kernel
subsystems to ensure their configuration can be measured:
  - by kernel subsystems themselves,
  - in a tamper resistant way,
  - and re-measured - triggered on state/configuration change.

This patch set:
  - defines a new IMA hook ima_measure_critical_data() to measure
    integrity critical data,
  - limits the critical data being measured based on a label,
  - defines a builtin critical data measurement policy,
  - and includes an SELinux consumer of the new IMA critical data hook.

This series is based on the following repo/branch:

 repo: https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git
 branch: next-integrity
 commit 207cdd565dfc ("ima: Don't modify file descriptor mode on the fly")

Change Log v7:    
Incorporated feedback from Mimi on v6 of this series.
 - Updated cover letter and patch descriptions as per Mimi's feedback.
 - Changed references to variable names and policy documentation from
   plural "data_sources" to singular "data_source".
 - Updated SELinux patch to measure only policy, instead of policy and
   state. The state measurement will be upstreamed through a separate
   patch.
 - Updated admin-guide/kernel-parameters.txt to document support for
   critical_data in builtin policy.

Change Log v6:
Incorporated feedback from Mimi on v5 of this series.
 - Got rid of patch 5 from the v5 of the series.(the allow list for data
   sources)
 - Updated function descriptions, changed variable names etc.
 - Moved the input param event_data_source in ima_measure_critical_data()
   to a new patch. (patch 6/8 of this series)
 - Split patch 4 from v5 of the series into two patches (patch 4/8 and 
   patch 5/8)
 - Updated cover letter and patch descriptions as per feedback.

Change Log v5:
(1) Incorporated feedback from Stephen on the last SeLinux patch.
 SeLinux Patch: https://patchwork.kernel.org/patch/11801585/
 - Freed memory in the reverse order of allocation in 
   selinux_measure_state().
 - Used scnprintf() instead of snprintf() to create the string for
   selinux state.
 - Allocated event name passed to ima_measure_critical_data() before
   gathering selinux state and policy information for measuring.

(2) Incorporated feedback from Mimi on v4 of this series.
 V4 of this Series: https://patchwork.kernel.org/project/linux-integrity/list/?series=354437

 - Removed patch "[v4,2/6] IMA: conditionally allow empty rule data"
 - Reversed the order of following patches.
      [v4,4/6] IMA: add policy to measure critical data from kernel components
      [v4,5/6] IMA: add hook to measure critical data from kernel components
   and renamed them to remove "from kernel components"
 - Added a new patch to this series - 
       IMA: add critical_data to built-in policy rules

 - Added the next version of SeLinux patch (mentioned above) to this
   series 
       selinux: measure state and hash of the policy using IMA

 - Updated cover-letter description to give broader perspective of the
   feature, rearranging paragraphs, removing unnecessary info, clarifying
   terms etc.
 - Got rid of opt_list param from ima_match_rule_data().
 - Updated the documentation to remove sources that don't yet exist.
 - detailed IMA hook description added to ima_measure_critical_data(),
   as well as elaborating terms event_name, event_data_source. 
 - "data_sources:=" is not a mandatory policy option for 
   func=CRITICAL_DATA anymore. If not present, all the data sources
   specified in __ima_supported_kernel_data_sources will be measured.


Lakshmi Ramasubramanian (2):
  IMA: define a builtin critical data measurement policy
  selinux: include a consumer of the new IMA critical data hook

Tushar Sugandhi (6):
  IMA: generalize keyring specific measurement constructs
  IMA: add support to measure buffer data hash
  IMA: define a hook to measure kernel integrity critical data
  IMA: add policy rule to measure critical data
  IMA: limit critical data measurement based on a label
  IMA: extend critical data hook to limit the measurement based on a
    label

 Documentation/ABI/testing/ima_policy          |   5 +-
 .../admin-guide/kernel-parameters.txt         |   5 +-
 include/linux/ima.h                           |   8 ++
 security/integrity/ima/ima.h                  |   8 +-
 security/integrity/ima/ima_api.c              |   8 +-
 security/integrity/ima/ima_appraise.c         |   2 +-
 security/integrity/ima/ima_asymmetric_keys.c  |   2 +-
 security/integrity/ima/ima_main.c             |  81 +++++++++++-
 security/integrity/ima/ima_policy.c           | 122 ++++++++++++++----
 security/integrity/ima/ima_queue_keys.c       |   3 +-
 security/selinux/Makefile                     |   2 +
 security/selinux/include/security.h           |  11 +-
 security/selinux/measure.c                    |  86 ++++++++++++
 security/selinux/ss/services.c                |  71 ++++++++--
 14 files changed, 364 insertions(+), 50 deletions(-)
 create mode 100644 security/selinux/measure.c

-- 
2.17.1

[PATCH v7 1/8] IMA: generalize keyring specific measurement constructs

[Tushar Sugandhi]

IMA functions such as ima_match_keyring(), process_buffer_measurement(),
ima_match_policy() etc. handle data specific to keyrings. Currently,
these constructs are not generic to handle any func specific data.
This makes it harder to extend them without code duplication.

Refactor the keyring specific measurement constructs to be generic and
reusable in other measurement scenarios.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 security/integrity/ima/ima.h        |  6 ++--
 security/integrity/ima/ima_api.c    |  6 ++--
 security/integrity/ima/ima_main.c   |  6 ++--
 security/integrity/ima/ima_policy.c | 49 ++++++++++++++++++-----------
 4 files changed, 40 insertions(+), 27 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 8e8b1e3cb847..e5622ce8cbb1 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -256,7 +256,7 @@ static inline void ima_process_queued_keys(void) {}
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
 		   int mask, enum ima_hooks func, int *pcr,
 		   struct ima_template_desc **template_desc,
-		   const char *keyring);
+		   const char *func_data);
 int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
 int ima_collect_measurement(struct integrity_iint_cache *iint,
 			    struct file *file, void *buf, loff_t size,
@@ -268,7 +268,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   struct ima_template_desc *template_desc);
 void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
-				int pcr, const char *keyring);
+				int pcr, const char *func_data);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct ima_event_data *event_data,
@@ -284,7 +284,7 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
 int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
 		     enum ima_hooks func, int mask, int flags, int *pcr,
 		     struct ima_template_desc **template_desc,
-		     const char *keyring);
+		     const char *func_data);
 void ima_init_policy(void);
 void ima_update_policy(void);
 void ima_update_policy_flag(void);
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 4f39fb93f278..af218babd198 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -170,7 +170,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
  * @func: caller identifier
  * @pcr: pointer filled in if matched measure policy sets pcr=
  * @template_desc: pointer filled in if matched measure policy sets template=
- * @keyring: keyring name used to determine the action
+ * @func_data: private data specific to @func, can be NULL.
  *
  * The policy is defined in terms of keypairs:
  *		subj=, obj=, type=, func=, mask=, fsmagic=
@@ -186,14 +186,14 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
 		   int mask, enum ima_hooks func, int *pcr,
 		   struct ima_template_desc **template_desc,
-		   const char *keyring)
+		   const char *func_data)
 {
 	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
 
 	flags &= ima_policy_flag;
 
 	return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
-				template_desc, keyring);
+				template_desc, func_data);
 }
 
 /*
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 68956e884403..e76ef4bfd0f4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -786,13 +786,13 @@ int ima_post_load_data(char *buf, loff_t size,
  * @eventname: event name to be used for the buffer entry.
  * @func: IMA hook
  * @pcr: pcr to extend the measurement
- * @keyring: keyring name to determine the action to be performed
+ * @func_data: private data specific to @func, can be NULL.
  *
  * Based on policy, the buffer is measured into the ima log.
  */
 void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
-				int pcr, const char *keyring)
+				int pcr, const char *func_data)
 {
 	int ret = 0;
 	const char *audit_cause = "ENOMEM";
@@ -831,7 +831,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 	if (func) {
 		security_task_getsecid(current, &secid);
 		action = ima_get_action(inode, current_cred(), secid, 0, func,
-					&pcr, &template, keyring);
+					&pcr, &template, func_data);
 		if (!(action & IMA_MEASURE))
 			return;
 	}
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 823a0c1379cb..25419c7ff50b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -453,30 +453,44 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 }
 
 /**
- * ima_match_keyring - determine whether the keyring matches the measure rule
- * @rule: a pointer to a rule
- * @keyring: name of the keyring to match against the measure rule
+ * ima_match_rule_data - determine whether the given func_data matches
+ *			 the measure rule data
+ * @rule: IMA policy rule
+ * @func_data: data to match against the measure rule data
  * @cred: a pointer to a credentials structure for user validation
  *
- * Returns true if keyring matches one in the rule, false otherwise.
+ * Returns true if func_data matches one in the rule, false otherwise.
  */
-static bool ima_match_keyring(struct ima_rule_entry *rule,
-			      const char *keyring, const struct cred *cred)
+static bool ima_match_rule_data(struct ima_rule_entry *rule,
+				const char *func_data,
+				const struct cred *cred)
 {
+	const struct ima_rule_opt_list *opt_list = NULL;
 	bool matched = false;
 	size_t i;
 
 	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
 		return false;
 
-	if (!rule->keyrings)
-		return true;
+	switch (rule->func) {
+	case KEY_CHECK:
+		if (!rule->keyrings)
+			return true;
+		else
+			opt_list = rule->keyrings;
+		break;
+	default:
+		break;
+	}
 
-	if (!keyring)
+	if (!func_data)
+		return false;
+
+	if (!opt_list)
 		return false;
 
-	for (i = 0; i < rule->keyrings->count; i++) {
-		if (!strcmp(rule->keyrings->items[i], keyring)) {
+	for (i = 0; i < opt_list->count; i++) {
+		if (!strcmp(opt_list->items[i], func_data)) {
 			matched = true;
 			break;
 		}
@@ -493,20 +507,20 @@ static bool ima_match_keyring(struct ima_rule_entry *rule,
  * @secid: the secid of the task to be validated
  * @func: LIM hook identifier
  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
- * @keyring: keyring name to check in policy for KEY_CHECK func
+ * @func_data: private data specific to @func, can be NULL.
  *
  * Returns true on rule match, false on failure.
  */
 static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 			    const struct cred *cred, u32 secid,
 			    enum ima_hooks func, int mask,
-			    const char *keyring)
+			    const char *func_data)
 {
 	int i;
 
 	if (func == KEY_CHECK) {
 		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
-		       ima_match_keyring(rule, keyring, cred);
+			ima_match_rule_data(rule, func_data, cred);
 	}
 	if ((rule->flags & IMA_FUNC) &&
 	    (rule->func != func && func != POST_SETATTR))
@@ -610,8 +624,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
  * @pcr: set the pcr to extend
  * @template_desc: the template that should be used for this rule
- * @keyring: the keyring name, if given, to be used to check in the policy.
- *           keyring can be NULL if func is anything other than KEY_CHECK.
+ * @func_data: private data specific to @func, can be NULL.
  *
  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
  * conditions.
@@ -623,7 +636,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
 int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
 		     enum ima_hooks func, int mask, int flags, int *pcr,
 		     struct ima_template_desc **template_desc,
-		     const char *keyring)
+		     const char *func_data)
 {
 	struct ima_rule_entry *entry;
 	int action = 0, actmask = flags | (flags << 1);
@@ -638,7 +651,7 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
 			continue;
 
 		if (!ima_match_rules(entry, inode, cred, secid, func, mask,
-				     keyring))
+				     func_data))
 			continue;
 
 		action |= entry->flags & IMA_ACTION_FLAGS;
-- 
2.17.1

[PATCH v7 2/8] IMA: add support to measure buffer data hash

[Tushar Sugandhi]

The original IMA buffer data measurement sizes were small (e.g. boot
command line), but the new buffer data measurement use cases have data 
sizes that are a lot larger.  Just as IMA measures the file data hash,
not the file data, IMA should similarly support the option for measuring 
the hash of the buffer data.

Measuring in-memory buffer-data/buffer-data-hash is different than
measuring file-data/file-data-hash. For the file, IMA stores the
measurements in both measurement log and the file's extended attribute -
which can later be used for appraisal as well. For buffer, the
measurements are only stored in the IMA log, since the buffer has no
extended attributes associated with it.

Introduce a boolean parameter measure_buf_hash to support measuring
hash of a buffer, which would be much smaller, instead of the buffer
itself.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 security/integrity/ima/ima.h                 |  3 +-
 security/integrity/ima/ima_appraise.c        |  2 +-
 security/integrity/ima/ima_asymmetric_keys.c |  2 +-
 security/integrity/ima/ima_main.c            | 36 +++++++++++++++++---
 security/integrity/ima/ima_queue_keys.c      |  3 +-
 5 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e5622ce8cbb1..fa3044a7539f 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   struct ima_template_desc *template_desc);
 void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
-				int pcr, const char *func_data);
+				int pcr, const char *func_data,
+				bool measure_buf_hash);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct ima_event_data *event_data,
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 8361941ee0a1..46ffa38bab12 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
 		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
 			process_buffer_measurement(NULL, digest, digestsize,
 						   "blacklisted-hash", NONE,
-						   pcr, NULL);
+						   pcr, NULL, false);
 	}
 
 	return rc;
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 1c68c500c26f..a74095793936 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 	 */
 	process_buffer_measurement(NULL, payload, payload_len,
 				   keyring->description, KEY_CHECK, 0,
-				   keyring->description);
+				   keyring->description, false);
 }
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index e76ef4bfd0f4..03aad13e9e70 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size,
 }
 
 /*
- * process_buffer_measurement - Measure the buffer to ima log.
+ * process_buffer_measurement - Measure the buffer or the buffer data hash
  * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
  * @buf: pointer to the buffer that needs to be added to the log.
  * @size: size of buffer(in bytes).
@@ -787,12 +787,23 @@ int ima_post_load_data(char *buf, loff_t size,
  * @func: IMA hook
  * @pcr: pcr to extend the measurement
  * @func_data: private data specific to @func, can be NULL.
+ * @measure_buf_hash: measure buffer hash
  *
- * Based on policy, the buffer is measured into the ima log.
+ * Measure the buffer into the IMA log, and extend the @pcr.
+ *
+ * Determine what buffers are allowed to be measured, based on the policy rules
+ * and the IMA hook passed using @func.
+ *
+ * Use @func_data, if provided, to match against the measurement policy rule
+ * data for @func.
+ *
+ * If @measure_buf_hash is set to true - measure hash of the buffer data,
+ * else measure the buffer data itself.
  */
 void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
-				int pcr, const char *func_data)
+				int pcr, const char *func_data,
+				bool measure_buf_hash)
 {
 	int ret = 0;
 	const char *audit_cause = "ENOMEM";
@@ -807,6 +818,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 		struct ima_digest_data hdr;
 		char digest[IMA_MAX_DIGEST_SIZE];
 	} hash = {};
+	char buf_hash[IMA_MAX_DIGEST_SIZE];
+	int buf_hash_len = hash_digest_size[ima_hash_algo];
 	int violation = 0;
 	int action = 0;
 	u32 secid;
@@ -849,6 +862,20 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 		goto out;
 	}
 
+	if (measure_buf_hash) {
+		memcpy(buf_hash, hash.hdr.digest, buf_hash_len);
+
+		ret = ima_calc_buffer_hash(buf_hash, buf_hash_len,
+					   iint.ima_hash);
+		if (ret < 0) {
+			audit_cause = "measure_buf_hash_error";
+			goto out;
+		}
+
+		event_data.buf = buf_hash;
+		event_data.buf_len = buf_hash_len;
+	}
+
 	ret = ima_alloc_init_template(&event_data, &entry, template);
 	if (ret < 0) {
 		audit_cause = "alloc_entry";
@@ -890,7 +917,8 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 		return;
 
 	process_buffer_measurement(file_inode(f.file), buf, size,
-				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
+				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL,
+				   false);
 	fdput(f);
 }
 
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index 69a8626a35c0..c2f2ad34f9b7 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -162,7 +162,8 @@ void ima_process_queued_keys(void)
 						   entry->payload_len,
 						   entry->keyring_name,
 						   KEY_CHECK, 0,
-						   entry->keyring_name);
+						   entry->keyring_name,
+						   false);
 		list_del(&entry->list);
 		ima_free_key_entry(entry);
 	}
-- 
2.17.1

[PATCH v7 3/8] IMA: define a hook to measure kernel integrity critical data

[Tushar Sugandhi]

IMA provides capabilities to measure file data, and in-memory buffer
data. However, various data structures, policies, and states
stored in kernel memory also impact the integrity of the system.
Several kernel subsystems contain such integrity critical data. These
kernel subsystems help protect the integrity of a device. Currently,
IMA does not provide a generic function for kernel subsystems to measure
their integrity critical data.
 
Define a new IMA hook - ima_measure_critical_data to measure kernel
integrity critical data.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 Documentation/ABI/testing/ima_policy |  2 +-
 include/linux/ima.h                  |  6 +++++
 security/integrity/ima/ima.h         |  1 +
 security/integrity/ima/ima_api.c     |  2 +-
 security/integrity/ima/ima_main.c    | 36 ++++++++++++++++++++++++++++
 security/integrity/ima/ima_policy.c  |  2 ++
 6 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index e35263f97fc1..6ec7daa87cba 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -32,7 +32,7 @@ Description:
 			func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK]MODULE_CHECK]
 			        [FIRMWARE_CHECK]
 				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
-				[KEXEC_CMDLINE] [KEY_CHECK]
+				[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
 			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
 			       [[^]MAY_EXEC]
 			fsmagic:= hex value
diff --git a/include/linux/ima.h b/include/linux/ima.h
index ac3d82f962f2..675f54db6264 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -30,6 +30,9 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 extern void ima_post_path_mknod(struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
+extern void ima_measure_critical_data(const char *event_name,
+				      const void *buf, int buf_len,
+				      bool measure_buf_hash);
 
 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
 extern void ima_appraise_parse_cmdline(void);
@@ -122,6 +125,9 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
 }
 
 static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
+static inline void ima_measure_critical_data(const char *event_name,
+					     const void *buf, int buf_len,
+					     bool measure_buf_hash) {}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index fa3044a7539f..7d9deda6a8b3 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -201,6 +201,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
 	hook(POLICY_CHECK, policy)			\
 	hook(KEXEC_CMDLINE, kexec_cmdline)		\
 	hook(KEY_CHECK, key)				\
+	hook(CRITICAL_DATA, critical_data)		\
 	hook(MAX_CHECK, none)
 
 #define __ima_hook_enumify(ENUM, str)	ENUM,
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index af218babd198..9917e1730cb6 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -176,7 +176,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
  *		subj=, obj=, type=, func=, mask=, fsmagic=
  *	subj,obj, and type: are LSM specific.
  *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
- *	| KEXEC_CMDLINE | KEY_CHECK
+ *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
  *	mask: contains the permission mask
  *	fsmagic: hex value
  *
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 03aad13e9e70..ae59f4a4dd70 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -922,6 +922,42 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 	fdput(f);
 }
 
+/**
+ * ima_measure_critical_data - measure kernel integrity critical data
+ * @event_name: event name to be used for the buffer entry
+ * @buf: pointer to buffer containing data to measure
+ * @buf_len: length of buffer(in bytes)
+ * @measure_buf_hash: measure buffer hash
+ *
+ * Measure the kernel subsystem data, critical to the integrity of the kernel,
+ * into the IMA log and extend the @pcr.
+ *
+ * Use @event_name to describe the state/buffer data change.
+ * Examples of critical data (buf) could be kernel in-memory r/o structures,
+ * hash of the memory structures, or data that represents subsystem state
+ * change.
+ *
+ * If @measure_buf_hash is set to true - measure hash of the buffer data,
+ * else measure the buffer data itself.
+ * measure_buf_hash can be used to save space, if the data being measured
+ * is too large.
+ *
+ * The data (buf) can only be measured, not appraised.
+ */
+void ima_measure_critical_data(const char *event_name,
+			       const void *buf, int buf_len,
+			       bool measure_buf_hash)
+{
+	if (!event_name || !buf || !buf_len) {
+		pr_err("Invalid arguments passed to %s().\n", __func__);
+		return;
+	}
+
+	process_buffer_measurement(NULL, buf, buf_len, event_name,
+				   CRITICAL_DATA, 0, NULL,
+				   measure_buf_hash);
+}
+
 static int __init init_ima(void)
 {
 	int error;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 25419c7ff50b..2a0c0603626e 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1251,6 +1251,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) &&
 				 strcmp(args[0].from, "KEY_CHECK") == 0)
 				entry->func = KEY_CHECK;
+			else if (strcmp(args[0].from, "CRITICAL_DATA") == 0)
+				entry->func = CRITICAL_DATA;
 			else
 				result = -EINVAL;
 			if (!result)
-- 
2.17.1

[PATCH v7 4/8] IMA: add policy rule to measure critical data

[Tushar Sugandhi]

A new IMA policy rule is needed for the IMA hook
ima_measure_critical_data() and the corresponding func CRITICAL_DATA for
measuring the input buffer. The policy rule should ensure the buffer
would get measured only when the policy rule allows the action. The
policy rule should also support the necessary constraints (flags etc.)
for integrity critical buffer data measurements.

Add a policy rule to define the constraints for restricting integrity
critical data measurements.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 security/integrity/ima/ima_policy.c | 35 +++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 2a0c0603626e..9a8ee80a3128 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -34,6 +34,7 @@
 #define IMA_PCR		0x0100
 #define IMA_FSNAME	0x0200
 #define IMA_KEYRINGS	0x0400
+#define IMA_DATA_SOURCE	0x0800
 
 #define UNKNOWN		0
 #define MEASURE		0x0001	/* same as IMA_MEASURE */
@@ -85,6 +86,7 @@ struct ima_rule_entry {
 	} lsm[MAX_LSM_RULES];
 	char *fsname;
 	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
+	struct ima_rule_opt_list *data_source; /* Measure data from this source */
 	struct ima_template_desc *template;
 };
 
@@ -479,6 +481,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
 		else
 			opt_list = rule->keyrings;
 		break;
+	case CRITICAL_DATA:
+		if (!rule->data_source)
+			return true;
+		else
+			opt_list = rule->data_source;
+		break;
 	default:
 		break;
 	}
@@ -518,13 +526,19 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 {
 	int i;
 
-	if (func == KEY_CHECK) {
-		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
-			ima_match_rule_data(rule, func_data, cred);
-	}
 	if ((rule->flags & IMA_FUNC) &&
 	    (rule->func != func && func != POST_SETATTR))
 		return false;
+
+	switch (func) {
+	case KEY_CHECK:
+	case CRITICAL_DATA:
+		return ((rule->func == func) &&
+			ima_match_rule_data(rule, func_data, cred));
+	default:
+		break;
+	}
+
 	if ((rule->flags & IMA_MASK) &&
 	    (rule->mask != mask && func != POST_SETATTR))
 		return false;
@@ -1119,6 +1133,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 		if (ima_rule_contains_lsm_cond(entry))
 			return false;
 
+		break;
+	case CRITICAL_DATA:
+		if (entry->action & ~(MEASURE | DONT_MEASURE))
+			return false;
+
+		if (!(entry->flags & IMA_DATA_SOURCE) ||
+		    (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
+		    IMA_DATA_SOURCE)))
+			return false;
+
+		if (ima_rule_contains_lsm_cond(entry))
+			return false;
+
 		break;
 	default:
 		return false;
-- 
2.17.1

[PATCH v7 5/8] IMA: limit critical data measurement based on a label

[Tushar Sugandhi]

System administrators should be able to limit which kernel subsystems
they want to measure the critical data for. To enable that, an IMA policy
condition to choose specific kernel subsystems is needed. This policy
condition would constrain the measurement of the critical data based on
a label for the given subsystems.

Add a new IMA policy condition - "data_source:=" to the IMA func
CRITICAL_DATA to allow measurement of various kernel subsystems. This
policy condition would enable the system administrators to restrict the
measurement to the labels listed in "data_source:=".

Limit the measurement to the labels that are specified in the IMA
policy - CRITICAL_DATA+"data_source:=". If "data_sources:=" is not
provided with the func CRITICAL_DATA, the data from all the
supported kernel subsystems is measured.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 Documentation/ABI/testing/ima_policy |  2 ++
 security/integrity/ima/ima_policy.c  | 26 +++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 6ec7daa87cba..0f4ee9e0a455 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -52,6 +52,8 @@ Description:
 			template:= name of a defined IMA template type
 			(eg, ima-ng). Only valid when action is "measure".
 			pcr:= decimal value
+			data_source:= [label]
+			label:= a unique string used for grouping and limiting critical data.
 
 		  default policy:
 			# PROC_SUPER_MAGIC
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 9a8ee80a3128..7486d09a3f60 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -934,7 +934,7 @@ enum {
 	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
 	Opt_appraise_type, Opt_appraise_flag,
 	Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
-	Opt_err
+	Opt_data_source, Opt_err
 };
 
 static const match_table_t policy_tokens = {
@@ -971,6 +971,7 @@ static const match_table_t policy_tokens = {
 	{Opt_pcr, "pcr=%s"},
 	{Opt_template, "template=%s"},
 	{Opt_keyrings, "keyrings=%s"},
+	{Opt_data_source, "data_source=%s"},
 	{Opt_err, NULL}
 };
 
@@ -1350,6 +1351,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 
 			entry->flags |= IMA_KEYRINGS;
 			break;
+		case Opt_data_source:
+			ima_log_string(ab, "data_source", args[0].from);
+
+			if (entry->data_source) {
+				result = -EINVAL;
+				break;
+			}
+
+			entry->data_source = ima_alloc_rule_opt_list(args);
+			if (IS_ERR(entry->data_source)) {
+				result = PTR_ERR(entry->data_source);
+				entry->data_source = NULL;
+				break;
+			}
+
+			entry->flags |= IMA_DATA_SOURCE;
+			break;
 		case Opt_fsuuid:
 			ima_log_string(ab, "fsuuid", args[0].from);
 
@@ -1730,6 +1748,12 @@ int ima_policy_show(struct seq_file *m, void *v)
 		seq_puts(m, " ");
 	}
 
+	if (entry->flags & IMA_DATA_SOURCE) {
+		seq_puts(m, "data_source=");
+		ima_show_rule_opt_list(m, entry->data_source);
+		seq_puts(m, " ");
+	}
+
 	if (entry->flags & IMA_PCR) {
 		snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
 		seq_printf(m, pt(Opt_pcr), tbuf);
-- 
2.17.1

[PATCH v7 6/8] IMA: extend critical data hook to limit the measurement based on a label

[Tushar Sugandhi]

The IMA hook ima_measure_critical_data() does not support a way to
specify the source of the critical data provider. Thus, the data
measurement cannot be constrained based on the data source label
in the IMA policy.

Extend the IMA hook ima_measure_critical_data() to support passing 
the data source label as an input parameter, so that the policy rule can
be used to limit the measurements based on the label.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 include/linux/ima.h               |  6 ++++--
 security/integrity/ima/ima_main.c | 11 ++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 675f54db6264..6434287a81cd 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -30,7 +30,8 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 extern void ima_post_path_mknod(struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
-extern void ima_measure_critical_data(const char *event_name,
+extern void ima_measure_critical_data(const char *event_data_source,
+				      const char *event_name,
 				      const void *buf, int buf_len,
 				      bool measure_buf_hash);
 
@@ -125,7 +126,8 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
 }
 
 static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
-static inline void ima_measure_critical_data(const char *event_name,
+static inline void ima_measure_critical_data(const char *event_data_source,
+					     const char *event_name,
 					     const void *buf, int buf_len,
 					     bool measure_buf_hash) {}
 #endif /* CONFIG_IMA */
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index ae59f4a4dd70..7c633901f441 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -924,6 +924,7 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 
 /**
  * ima_measure_critical_data - measure kernel integrity critical data
+ * @event_data_source: kernel data source being measured
  * @event_name: event name to be used for the buffer entry
  * @buf: pointer to buffer containing data to measure
  * @buf_len: length of buffer(in bytes)
@@ -932,6 +933,9 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
  * Measure the kernel subsystem data, critical to the integrity of the kernel,
  * into the IMA log and extend the @pcr.
  *
+ * Use @event_data_source to describe the kernel data source for the buffer
+ * being measured.
+ *
  * Use @event_name to describe the state/buffer data change.
  * Examples of critical data (buf) could be kernel in-memory r/o structures,
  * hash of the memory structures, or data that represents subsystem state
@@ -944,17 +948,18 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
  *
  * The data (buf) can only be measured, not appraised.
  */
-void ima_measure_critical_data(const char *event_name,
+void ima_measure_critical_data(const char *event_data_source,
+			       const char *event_name,
 			       const void *buf, int buf_len,
 			       bool measure_buf_hash)
 {
-	if (!event_name || !buf || !buf_len) {
+	if (!event_name || !event_data_source || !buf || !buf_len) {
 		pr_err("Invalid arguments passed to %s().\n", __func__);
 		return;
 	}
 
 	process_buffer_measurement(NULL, buf, buf_len, event_name,
-				   CRITICAL_DATA, 0, NULL,
+				   CRITICAL_DATA, 0, event_data_source,
 				   measure_buf_hash);
 }
 
-- 
2.17.1

[PATCH v7 7/8] IMA: define a builtin critical data measurement policy

[Tushar Sugandhi]

From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Define a new critical data builtin policy to allow measuring
early kernel integrity critical data before a custom IMA policy
is loaded.

Add critical data to built-in IMA rules if the kernel command line
contains "ima_policy=critical_data".

Update the documentation on kernel parameters to document
the new critical data builtin policy.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  5 ++++-
 security/integrity/ima/ima_policy.c             | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..6034d75c3ca0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1746,7 +1746,7 @@
 	ima_policy=	[IMA]
 			The builtin policies to load during IMA setup.
 			Format: "tcb | appraise_tcb | secure_boot |
-				 fail_securely"
+				 fail_securely | critical_data"
 
 			The "tcb" policy measures all programs exec'd, files
 			mmap'd for exec, and all files opened with the read
@@ -1765,6 +1765,9 @@
 			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
 			flag.
 
+			The "critical_data" policy measures kernel integrity
+			critical data.
+
 	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
 			Load a policy which meets the needs of the Trusted
 			Computing Base.  This means IMA will measure all
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 7486d09a3f60..37ca16a9e65f 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -206,6 +206,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
 	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
 };
 
+static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
+	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
+};
+
 /* An array of architecture specific rules */
 static struct ima_rule_entry *arch_policy_entry __ro_after_init;
 
@@ -228,6 +232,7 @@ __setup("ima_tcb", default_measure_policy_setup);
 
 static bool ima_use_appraise_tcb __initdata;
 static bool ima_use_secure_boot __initdata;
+static bool ima_use_critical_data __initdata;
 static bool ima_fail_unverifiable_sigs __ro_after_init;
 static int __init policy_setup(char *str)
 {
@@ -242,6 +247,8 @@ static int __init policy_setup(char *str)
 			ima_use_appraise_tcb = true;
 		else if (strcmp(p, "secure_boot") == 0)
 			ima_use_secure_boot = true;
+		else if (strcmp(p, "critical_data") == 0)
+			ima_use_critical_data = true;
 		else if (strcmp(p, "fail_securely") == 0)
 			ima_fail_unverifiable_sigs = true;
 		else
@@ -875,6 +882,11 @@ void __init ima_init_policy(void)
 			  ARRAY_SIZE(default_appraise_rules),
 			  IMA_DEFAULT_POLICY);
 
+	if (ima_use_critical_data)
+		add_rules(critical_data_rules,
+			  ARRAY_SIZE(critical_data_rules),
+			  IMA_DEFAULT_POLICY);
+
 	ima_update_policy_flag();
 }
 
-- 
2.17.1

[PATCH v7 8/8] selinux: include a consumer of the new IMA critical data hook

[Tushar Sugandhi]

From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

IMA measures files and buffer data such as keys, command line arguments
passed to the kernel on kexec system call, etc. While these measurements
enable monitoring and validating the integrity of the system, it is not
sufficient. Various data structures, policies and states stored in kernel
memory also impact the integrity of the system. Updates to these data
structures would have an impact on the security functionalities.
For example, SELinux stores the active policy in memory. Changes to this
data at runtime would have an impact on the security guarantees provided
by SELinux. Measuring such in-memory data structures through IMA
subsystem provides a secure way for a remote attestation service to
know the state of the system and also the runtime changes in the state
of the system.

SELinux policy is a critical data for this security module that needs
to be measured. This measurement can be used by an attestation service,
for instance, to verify if the policy has been setup correctly and that
it hasn't been tampered at run-time.

Measure the hash of the loaded policy by calling the IMA hook
ima_measure_critical_data(). Since the size of the loaded policy can
be large (several MB), measure the hash of the policy instead of
the entire policy to avoid bloating the IMA log entry.

Add "selinux" to the list of supported data sources maintained by IMA
to enable measuring SELinux data.

To enable SELinux data measurement, the following steps are required:

1, Add "ima_policy=critical_data" to the kernel command line arguments
   to enable measuring SELinux data at boot time.
For example,
  BOOT_IMAGE=/boot/vmlinuz-5.10.0-rc1+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset security=selinux ima_policy=critical_data

2, Add the following rule to /etc/ima/ima-policy
   measure func=CRITICAL_DATA data_source=selinux

Sample measurement of the hash of SELinux policy:

To verify the measured data with the current SELinux policy run
the following commands and verify the output hash values match.

  sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1

  grep "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | tail -1 | cut -d' ' -f 6

Note that the actual verification of SELinux policy would require loading
the expected policy into an identical kernel on a pristine/known-safe
system and run the sha256sum /sys/kernel/selinux/policy there to get
the expected hash.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
---
 Documentation/ABI/testing/ima_policy |  3 +-
 security/selinux/Makefile            |  2 +
 security/selinux/include/security.h  | 11 +++-
 security/selinux/measure.c           | 86 ++++++++++++++++++++++++++++
 security/selinux/ss/services.c       | 71 ++++++++++++++++++++---
 5 files changed, 162 insertions(+), 11 deletions(-)
 create mode 100644 security/selinux/measure.c

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 0f4ee9e0a455..7c7023f7986b 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -52,8 +52,9 @@ Description:
 			template:= name of a defined IMA template type
 			(eg, ima-ng). Only valid when action is "measure".
 			pcr:= decimal value
-			data_source:= [label]
+			data_source:= [selinux]|[label]
 			label:= a unique string used for grouping and limiting critical data.
+			For example, "selinux" to measure critical data for SELinux.
 
 		  default policy:
 			# PROC_SUPER_MAGIC
diff --git a/security/selinux/Makefile b/security/selinux/Makefile
index 4d8e0e8adf0b..83d512116341 100644
--- a/security/selinux/Makefile
+++ b/security/selinux/Makefile
@@ -16,6 +16,8 @@ selinux-$(CONFIG_NETLABEL) += netlabel.o
 
 selinux-$(CONFIG_SECURITY_INFINIBAND) += ibpkey.o
 
+selinux-$(CONFIG_IMA) += measure.o
+
 ccflags-y := -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include
 
 $(addprefix $(obj)/,$(selinux-y)): $(obj)/flask.h
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 3cc8bab31ea8..18ee65c98446 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -229,7 +229,8 @@ void selinux_policy_cancel(struct selinux_state *state,
 			struct selinux_policy *policy);
 int security_read_policy(struct selinux_state *state,
 			 void **data, size_t *len);
-
+int security_read_policy_kernel(struct selinux_state *state,
+				void **data, size_t *len);
 int security_policycap_supported(struct selinux_state *state,
 				 unsigned int req_cap);
 
@@ -446,4 +447,12 @@ extern void ebitmap_cache_init(void);
 extern void hashtab_cache_init(void);
 extern int security_sidtab_hash_stats(struct selinux_state *state, char *page);
 
+#ifdef CONFIG_IMA
+extern void selinux_measure_state(struct selinux_state *selinux_state);
+#else
+static inline void selinux_measure_state(struct selinux_state *selinux_state)
+{
+}
+#endif
+
 #endif /* _SELINUX_SECURITY_H_ */
diff --git a/security/selinux/measure.c b/security/selinux/measure.c
new file mode 100644
index 000000000000..c409ada6ea39
--- /dev/null
+++ b/security/selinux/measure.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Measure SELinux state using IMA subsystem.
+ */
+#include <linux/vmalloc.h>
+#include <linux/ktime.h>
+#include <linux/ima.h>
+#include "security.h"
+
+/*
+ * This function creates a unique name by appending the timestamp to
+ * the given string. This string is passed as "event_name" to the IMA
+ * hook to measure the given SELinux data.
+ *
+ * The data provided by SELinux to the IMA subsystem for measuring may have
+ * already been measured (for instance the same state existed earlier).
+ * But for SELinux the current data represents a state change and hence
+ * needs to be measured again. To enable this, pass a unique "event_name"
+ * to the IMA hook so that IMA subsystem will always measure the given data.
+ *
+ * For example,
+ * At time T0 SELinux data to be measured is "foo". IMA measures it.
+ * At time T1 the data is changed to "bar". IMA measures it.
+ * At time T2 the data is changed to "foo" again. IMA will not measure it
+ * (since it was already measured) unless the event_name, for instance,
+ * is different in this call.
+ */
+static char *selinux_event_name(const char *name_prefix)
+{
+	char *event_name = NULL;
+	struct timespec64 cur_time;
+
+	ktime_get_real_ts64(&cur_time);
+	event_name = kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix,
+			       cur_time.tv_sec, cur_time.tv_nsec);
+	if (!event_name) {
+		pr_err("%s: event name not allocated.\n", __func__);
+		return NULL;
+	}
+
+	return event_name;
+}
+
+/*
+ * selinux_measure_state - Measure hash of the SELinux policy
+ *
+ * @state: selinux state struct
+ *
+ * NOTE: This function must be called with policy_mutex held.
+ */
+void selinux_measure_state(struct selinux_state *state)
+{
+	void *policy = NULL;
+	char *policy_event_name = NULL;
+	size_t policy_len;
+	int rc = 0;
+	bool initialized = selinux_initialized(state);
+
+	/*
+	 * Measure SELinux policy only after initialization is completed.
+	 */
+	if (!initialized)
+		goto out;
+
+	policy_event_name = selinux_event_name("selinux-policy-hash");
+	if (!policy_event_name) {
+		pr_err("%s: Event name for policy not allocated.\n",
+		       __func__);
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	rc = security_read_policy_kernel(state, &policy, &policy_len);
+	if (rc) {
+		pr_err("%s: Failed to read policy %d.\n", __func__, rc);
+		goto out;
+	}
+
+	ima_measure_critical_data("selinux", policy_event_name,
+				  policy, policy_len, true);
+
+	vfree(policy);
+
+out:
+	kfree(policy_event_name);
+}
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 9704c8a32303..dfa2e00894ae 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2180,6 +2180,7 @@ static void selinux_notify_policy_change(struct selinux_state *state,
 	selinux_status_update_policyload(state, seqno);
 	selinux_netlbl_cache_invalidate();
 	selinux_xfrm_notify_policyload();
+	selinux_measure_state(state);
 }
 
 void selinux_policy_commit(struct selinux_state *state,
@@ -3875,8 +3876,33 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state,
 }
 #endif /* CONFIG_NETLABEL */
 
+/**
+ * security_read_selinux_policy - read the policy.
+ * @policy: SELinux policy
+ * @data: binary policy data
+ * @len: length of data in bytes
+ *
+ */
+static int security_read_selinux_policy(struct selinux_policy *policy,
+					void *data, size_t *len)
+{
+	int rc;
+	struct policy_file fp;
+
+	fp.data = data;
+	fp.len = *len;
+
+	rc = policydb_write(&policy->policydb, &fp);
+	if (rc)
+		return rc;
+
+	*len = (unsigned long)fp.data - (unsigned long)data;
+	return 0;
+}
+
 /**
  * security_read_policy - read the policy.
+ * @state: selinux_state
  * @data: binary policy data
  * @len: length of data in bytes
  *
@@ -3885,8 +3911,6 @@ int security_read_policy(struct selinux_state *state,
 			 void **data, size_t *len)
 {
 	struct selinux_policy *policy;
-	int rc;
-	struct policy_file fp;
 
 	policy = rcu_dereference_protected(
 			state->policy, lockdep_is_held(&state->policy_mutex));
@@ -3898,14 +3922,43 @@ int security_read_policy(struct selinux_state *state,
 	if (!*data)
 		return -ENOMEM;
 
-	fp.data = *data;
-	fp.len = *len;
+	return security_read_selinux_policy(policy, *data, len);
+}
 
-	rc = policydb_write(&policy->policydb, &fp);
-	if (rc)
-		return rc;
+/**
+ * security_read_policy_kernel - read the policy.
+ * @state: selinux_state
+ * @data: binary policy data
+ * @len: length of data in bytes
+ *
+ * Allocates kernel memory for reading SELinux policy.
+ * This function is for internal use only and should not
+ * be used for returning data to user space.
+ *
+ * This function must be called with policy_mutex held.
+ */
+int security_read_policy_kernel(struct selinux_state *state,
+				void **data, size_t *len)
+{
+	struct selinux_policy *policy;
+	int rc = 0;
 
-	*len = (unsigned long)fp.data - (unsigned long)*data;
-	return 0;
+	policy = rcu_dereference_protected(
+			state->policy, lockdep_is_held(&state->policy_mutex));
+	if (!policy) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	*len = policy->policydb.len;
+	*data = vmalloc(*len);
+	if (!*data) {
+		rc = -ENOMEM;
+		goto out;
+	}
 
+	rc = security_read_selinux_policy(policy, *data, len);
+
+out:
+	return rc;
 }
-- 
2.17.1

Re: [PATCH v7 1/8] IMA: generalize keyring specific measurement constructs

[Tyler Hicks]

On 2020-12-09 11:42:05, Tushar Sugandhi wrote:
> IMA functions such as ima_match_keyring(), process_buffer_measurement(),
> ima_match_policy() etc. handle data specific to keyrings. Currently,
> these constructs are not generic to handle any func specific data.
> This makes it harder to extend them without code duplication.
> 
> Refactor the keyring specific measurement constructs to be generic and
> reusable in other measurement scenarios.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>

I've got a few code cleanup suggestions to ima_match_rule_data() below
but the current patch is fine:

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

> ---
>  security/integrity/ima/ima.h        |  6 ++--
>  security/integrity/ima/ima_api.c    |  6 ++--
>  security/integrity/ima/ima_main.c   |  6 ++--
>  security/integrity/ima/ima_policy.c | 49 ++++++++++++++++++-----------
>  4 files changed, 40 insertions(+), 27 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 8e8b1e3cb847..e5622ce8cbb1 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -256,7 +256,7 @@ static inline void ima_process_queued_keys(void) {}
>  int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>  		   int mask, enum ima_hooks func, int *pcr,
>  		   struct ima_template_desc **template_desc,
> -		   const char *keyring);
> +		   const char *func_data);
>  int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
>  int ima_collect_measurement(struct integrity_iint_cache *iint,
>  			    struct file *file, void *buf, loff_t size,
> @@ -268,7 +268,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>  			   struct ima_template_desc *template_desc);
>  void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *keyring);
> +				int pcr, const char *func_data);
>  void ima_audit_measurement(struct integrity_iint_cache *iint,
>  			   const unsigned char *filename);
>  int ima_alloc_init_template(struct ima_event_data *event_data,
> @@ -284,7 +284,7 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
>  int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>  		     enum ima_hooks func, int mask, int flags, int *pcr,
>  		     struct ima_template_desc **template_desc,
> -		     const char *keyring);
> +		     const char *func_data);
>  void ima_init_policy(void);
>  void ima_update_policy(void);
>  void ima_update_policy_flag(void);
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 4f39fb93f278..af218babd198 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -170,7 +170,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>   * @func: caller identifier
>   * @pcr: pointer filled in if matched measure policy sets pcr=
>   * @template_desc: pointer filled in if matched measure policy sets template=
> - * @keyring: keyring name used to determine the action
> + * @func_data: private data specific to @func, can be NULL.
>   *
>   * The policy is defined in terms of keypairs:
>   *		subj=, obj=, type=, func=, mask=, fsmagic=
> @@ -186,14 +186,14 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>  int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>  		   int mask, enum ima_hooks func, int *pcr,
>  		   struct ima_template_desc **template_desc,
> -		   const char *keyring)
> +		   const char *func_data)
>  {
>  	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
>  
>  	flags &= ima_policy_flag;
>  
>  	return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
> -				template_desc, keyring);
> +				template_desc, func_data);
>  }
>  
>  /*
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 68956e884403..e76ef4bfd0f4 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -786,13 +786,13 @@ int ima_post_load_data(char *buf, loff_t size,
>   * @eventname: event name to be used for the buffer entry.
>   * @func: IMA hook
>   * @pcr: pcr to extend the measurement
> - * @keyring: keyring name to determine the action to be performed
> + * @func_data: private data specific to @func, can be NULL.
>   *
>   * Based on policy, the buffer is measured into the ima log.
>   */
>  void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *keyring)
> +				int pcr, const char *func_data)
>  {
>  	int ret = 0;
>  	const char *audit_cause = "ENOMEM";
> @@ -831,7 +831,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  	if (func) {
>  		security_task_getsecid(current, &secid);
>  		action = ima_get_action(inode, current_cred(), secid, 0, func,
> -					&pcr, &template, keyring);
> +					&pcr, &template, func_data);
>  		if (!(action & IMA_MEASURE))
>  			return;
>  	}
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 823a0c1379cb..25419c7ff50b 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -453,30 +453,44 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
>  }
>  
>  /**
> - * ima_match_keyring - determine whether the keyring matches the measure rule
> - * @rule: a pointer to a rule
> - * @keyring: name of the keyring to match against the measure rule
> + * ima_match_rule_data - determine whether the given func_data matches
> + *			 the measure rule data
> + * @rule: IMA policy rule
> + * @func_data: data to match against the measure rule data
>   * @cred: a pointer to a credentials structure for user validation
>   *
> - * Returns true if keyring matches one in the rule, false otherwise.
> + * Returns true if func_data matches one in the rule, false otherwise.
>   */
> -static bool ima_match_keyring(struct ima_rule_entry *rule,
> -			      const char *keyring, const struct cred *cred)
> +static bool ima_match_rule_data(struct ima_rule_entry *rule,
> +				const char *func_data,
> +				const struct cred *cred)
>  {
> +	const struct ima_rule_opt_list *opt_list = NULL;
>  	bool matched = false;
>  	size_t i;
>  
>  	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
>  		return false;
>  
> -	if (!rule->keyrings)
> -		return true;
> +	switch (rule->func) {
> +	case KEY_CHECK:
> +		if (!rule->keyrings)
> +			return true;
> +		else
> +			opt_list = rule->keyrings;

You return if rule->keyrings is NULL so drop this else and simply make
the opt_list assignment.

> +		break;
> +	default:
> +		break;

I would like to see the 'return false;' happen immediately here instead
of waiting for the opt_list check below.

> +	}
>  
> -	if (!keyring)
> +	if (!func_data)
> +		return false;
> +
> +	if (!opt_list)
>  		return false;

If you return false in the 'default:' case above, you can just remove this
entire conditional because you'll be assigning opt_list in all of the
valid cases of the switch statement.

Tyler

>  
> -	for (i = 0; i < rule->keyrings->count; i++) {
> -		if (!strcmp(rule->keyrings->items[i], keyring)) {
> +	for (i = 0; i < opt_list->count; i++) {
> +		if (!strcmp(opt_list->items[i], func_data)) {
>  			matched = true;
>  			break;
>  		}
> @@ -493,20 +507,20 @@ static bool ima_match_keyring(struct ima_rule_entry *rule,
>   * @secid: the secid of the task to be validated
>   * @func: LIM hook identifier
>   * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
> - * @keyring: keyring name to check in policy for KEY_CHECK func
> + * @func_data: private data specific to @func, can be NULL.
>   *
>   * Returns true on rule match, false on failure.
>   */
>  static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>  			    const struct cred *cred, u32 secid,
>  			    enum ima_hooks func, int mask,
> -			    const char *keyring)
> +			    const char *func_data)
>  {
>  	int i;
>  
>  	if (func == KEY_CHECK) {
>  		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
> -		       ima_match_keyring(rule, keyring, cred);
> +			ima_match_rule_data(rule, func_data, cred);
>  	}
>  	if ((rule->flags & IMA_FUNC) &&
>  	    (rule->func != func && func != POST_SETATTR))
> @@ -610,8 +624,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>   * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
>   * @pcr: set the pcr to extend
>   * @template_desc: the template that should be used for this rule
> - * @keyring: the keyring name, if given, to be used to check in the policy.
> - *           keyring can be NULL if func is anything other than KEY_CHECK.
> + * @func_data: private data specific to @func, can be NULL.
>   *
>   * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
>   * conditions.
> @@ -623,7 +636,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>  int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>  		     enum ima_hooks func, int mask, int flags, int *pcr,
>  		     struct ima_template_desc **template_desc,
> -		     const char *keyring)
> +		     const char *func_data)
>  {
>  	struct ima_rule_entry *entry;
>  	int action = 0, actmask = flags | (flags << 1);
> @@ -638,7 +651,7 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>  			continue;
>  
>  		if (!ima_match_rules(entry, inode, cred, secid, func, mask,
> -				     keyring))
> +				     func_data))
>  			continue;
>  
>  		action |= entry->flags & IMA_ACTION_FLAGS;
> -- 
> 2.17.1
> 

Re: [PATCH v7 2/8] IMA: add support to measure buffer data hash

[Tyler Hicks]

On 2020-12-09 11:42:06, Tushar Sugandhi wrote:
> The original IMA buffer data measurement sizes were small (e.g. boot
> command line), but the new buffer data measurement use cases have data 
> sizes that are a lot larger.  Just as IMA measures the file data hash,
> not the file data, IMA should similarly support the option for measuring 
> the hash of the buffer data.
> 
> Measuring in-memory buffer-data/buffer-data-hash is different than
> measuring file-data/file-data-hash. For the file, IMA stores the
> measurements in both measurement log and the file's extended attribute -
> which can later be used for appraisal as well. For buffer, the
> measurements are only stored in the IMA log, since the buffer has no
> extended attributes associated with it.
> 
> Introduce a boolean parameter measure_buf_hash to support measuring
> hash of a buffer, which would be much smaller, instead of the buffer
> itself.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> ---
>  security/integrity/ima/ima.h                 |  3 +-
>  security/integrity/ima/ima_appraise.c        |  2 +-
>  security/integrity/ima/ima_asymmetric_keys.c |  2 +-
>  security/integrity/ima/ima_main.c            | 36 +++++++++++++++++---
>  security/integrity/ima/ima_queue_keys.c      |  3 +-
>  5 files changed, 38 insertions(+), 8 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index e5622ce8cbb1..fa3044a7539f 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>  			   struct ima_template_desc *template_desc);
>  void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *func_data);
> +				int pcr, const char *func_data,
> +				bool measure_buf_hash);
>  void ima_audit_measurement(struct integrity_iint_cache *iint,
>  			   const unsigned char *filename);
>  int ima_alloc_init_template(struct ima_event_data *event_data,
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 8361941ee0a1..46ffa38bab12 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
>  		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
>  			process_buffer_measurement(NULL, digest, digestsize,
>  						   "blacklisted-hash", NONE,
> -						   pcr, NULL);
> +						   pcr, NULL, false);
>  	}
>  
>  	return rc;
> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
> index 1c68c500c26f..a74095793936 100644
> --- a/security/integrity/ima/ima_asymmetric_keys.c
> +++ b/security/integrity/ima/ima_asymmetric_keys.c
> @@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>  	 */
>  	process_buffer_measurement(NULL, payload, payload_len,
>  				   keyring->description, KEY_CHECK, 0,
> -				   keyring->description);
> +				   keyring->description, false);
>  }
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index e76ef4bfd0f4..03aad13e9e70 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size,
>  }
>  
>  /*
> - * process_buffer_measurement - Measure the buffer to ima log.
> + * process_buffer_measurement - Measure the buffer or the buffer data hash
>   * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
>   * @buf: pointer to the buffer that needs to be added to the log.
>   * @size: size of buffer(in bytes).
> @@ -787,12 +787,23 @@ int ima_post_load_data(char *buf, loff_t size,
>   * @func: IMA hook
>   * @pcr: pcr to extend the measurement
>   * @func_data: private data specific to @func, can be NULL.
> + * @measure_buf_hash: measure buffer hash
>   *
> - * Based on policy, the buffer is measured into the ima log.
> + * Measure the buffer into the IMA log, and extend the @pcr.
> + *
> + * Determine what buffers are allowed to be measured, based on the policy rules
> + * and the IMA hook passed using @func.
> + *
> + * Use @func_data, if provided, to match against the measurement policy rule
> + * data for @func.
> + *
> + * If @measure_buf_hash is set to true - measure hash of the buffer data,
> + * else measure the buffer data itself.
>   */
>  void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  				const char *eventname, enum ima_hooks func,
> -				int pcr, const char *func_data)
> +				int pcr, const char *func_data,
> +				bool measure_buf_hash)
>  {
>  	int ret = 0;
>  	const char *audit_cause = "ENOMEM";
> @@ -807,6 +818,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  		struct ima_digest_data hdr;
>  		char digest[IMA_MAX_DIGEST_SIZE];
>  	} hash = {};
> +	char buf_hash[IMA_MAX_DIGEST_SIZE];
> +	int buf_hash_len = hash_digest_size[ima_hash_algo];
>  	int violation = 0;
>  	int action = 0;
>  	u32 secid;
> @@ -849,6 +862,20 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>  		goto out;
>  	}
>  
> +	if (measure_buf_hash) {
> +		memcpy(buf_hash, hash.hdr.digest, buf_hash_len);
> +
> +		ret = ima_calc_buffer_hash(buf_hash, buf_hash_len,
> +					   iint.ima_hash);
> +		if (ret < 0) {
> +			audit_cause = "measure_buf_hash_error";
> +			goto out;
> +		}
> +
> +		event_data.buf = buf_hash;
> +		event_data.buf_len = buf_hash_len;
> +	}
> +
>  	ret = ima_alloc_init_template(&event_data, &entry, template);
>  	if (ret < 0) {
>  		audit_cause = "alloc_entry";

A few more lines below, not present in this context, is a call to
ima_store_template() with buf as the fourth parameter passed in. That
parameter eventually makes its way to integrity_audit_message() and ends
up as part of an audit message as the value of the "name=" field. This
is usually a filename, the name of a key, or a kexec cmdline. In the
case of measuring SELinux policy, do we want the entire buf to be
included in the audit message?

Tyler

> @@ -890,7 +917,8 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>  		return;
>  
>  	process_buffer_measurement(file_inode(f.file), buf, size,
> -				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
> +				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL,
> +				   false);
>  	fdput(f);
>  }
>  
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> index 69a8626a35c0..c2f2ad34f9b7 100644
> --- a/security/integrity/ima/ima_queue_keys.c
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -162,7 +162,8 @@ void ima_process_queued_keys(void)
>  						   entry->payload_len,
>  						   entry->keyring_name,
>  						   KEY_CHECK, 0,
> -						   entry->keyring_name);
> +						   entry->keyring_name,
> +						   false);
>  		list_del(&entry->list);
>  		ima_free_key_entry(entry);
>  	}
> -- 
> 2.17.1
> 

Re: [PATCH v7 3/8] IMA: define a hook to measure kernel integrity critical data

[Tyler Hicks]

On 2020-12-09 11:42:07, Tushar Sugandhi wrote:
> IMA provides capabilities to measure file data, and in-memory buffer
> data. However, various data structures, policies, and states
> stored in kernel memory also impact the integrity of the system.
> Several kernel subsystems contain such integrity critical data. These
> kernel subsystems help protect the integrity of a device. Currently,
> IMA does not provide a generic function for kernel subsystems to measure
> their integrity critical data.
>  
> Define a new IMA hook - ima_measure_critical_data to measure kernel
> integrity critical data.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> ---
>  Documentation/ABI/testing/ima_policy |  2 +-
>  include/linux/ima.h                  |  6 +++++
>  security/integrity/ima/ima.h         |  1 +
>  security/integrity/ima/ima_api.c     |  2 +-
>  security/integrity/ima/ima_main.c    | 36 ++++++++++++++++++++++++++++
>  security/integrity/ima/ima_policy.c  |  2 ++
>  6 files changed, 47 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index e35263f97fc1..6ec7daa87cba 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -32,7 +32,7 @@ Description:
>  			func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK]MODULE_CHECK]
>  			        [FIRMWARE_CHECK]
>  				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
> -				[KEXEC_CMDLINE] [KEY_CHECK]
> +				[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
>  			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
>  			       [[^]MAY_EXEC]
>  			fsmagic:= hex value
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index ac3d82f962f2..675f54db6264 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -30,6 +30,9 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
>  extern void ima_post_path_mknod(struct dentry *dentry);
>  extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
>  extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
> +extern void ima_measure_critical_data(const char *event_name,
> +				      const void *buf, int buf_len,
> +				      bool measure_buf_hash);
>  
>  #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
>  extern void ima_appraise_parse_cmdline(void);
> @@ -122,6 +125,9 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
>  }
>  
>  static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
> +static inline void ima_measure_critical_data(const char *event_name,
> +					     const void *buf, int buf_len,
> +					     bool measure_buf_hash) {}
>  #endif /* CONFIG_IMA */
>  
>  #ifndef CONFIG_IMA_KEXEC
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index fa3044a7539f..7d9deda6a8b3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -201,6 +201,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
>  	hook(POLICY_CHECK, policy)			\
>  	hook(KEXEC_CMDLINE, kexec_cmdline)		\
>  	hook(KEY_CHECK, key)				\
> +	hook(CRITICAL_DATA, critical_data)		\
>  	hook(MAX_CHECK, none)
>  
>  #define __ima_hook_enumify(ENUM, str)	ENUM,
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index af218babd198..9917e1730cb6 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -176,7 +176,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>   *		subj=, obj=, type=, func=, mask=, fsmagic=
>   *	subj,obj, and type: are LSM specific.
>   *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
> - *	| KEXEC_CMDLINE | KEY_CHECK
> + *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
>   *	mask: contains the permission mask
>   *	fsmagic: hex value
>   *
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 03aad13e9e70..ae59f4a4dd70 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -922,6 +922,42 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>  	fdput(f);
>  }
>  
> +/**
> + * ima_measure_critical_data - measure kernel integrity critical data
> + * @event_name: event name to be used for the buffer entry
> + * @buf: pointer to buffer containing data to measure
> + * @buf_len: length of buffer(in bytes)
> + * @measure_buf_hash: measure buffer hash
> + *
> + * Measure the kernel subsystem data, critical to the integrity of the kernel,
> + * into the IMA log and extend the @pcr.
> + *
> + * Use @event_name to describe the state/buffer data change.
> + * Examples of critical data (buf) could be kernel in-memory r/o structures,
                                 ^
				 @buf

> + * hash of the memory structures, or data that represents subsystem state
> + * change.
> + *
> + * If @measure_buf_hash is set to true - measure hash of the buffer data,
> + * else measure the buffer data itself.
> + * measure_buf_hash can be used to save space, if the data being measured
      ^
      @measure_buf_hash

> + * is too large.
> + *
> + * The data (buf) can only be measured, not appraised.
                ^
		@buf

> + */
> +void ima_measure_critical_data(const char *event_name,
> +			       const void *buf, int buf_len,
> +			       bool measure_buf_hash)
> +{
> +	if (!event_name || !buf || !buf_len) {
> +		pr_err("Invalid arguments passed to %s().\n", __func__);

This is a problem for the developer making use of the
ima_measure_critical_data() API and shouldn't be logged, IMO, because a
user/admin can do nothing about it. I think the error message should be
dropped.

> +		return;
> +	}
> +
> +	process_buffer_measurement(NULL, buf, buf_len, event_name,
> +				   CRITICAL_DATA, 0, NULL,
> +				   measure_buf_hash);
> +}
> +
>  static int __init init_ima(void)
>  {
>  	int error;
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 25419c7ff50b..2a0c0603626e 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1251,6 +1251,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  			else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) &&
>  				 strcmp(args[0].from, "KEY_CHECK") == 0)
>  				entry->func = KEY_CHECK;
> +			else if (strcmp(args[0].from, "CRITICAL_DATA") == 0)
> +				entry->func = CRITICAL_DATA;
>  			else
>  				result = -EINVAL;
>  			if (!result)

This hunk and the above change to Documentation/ABI/testing/ima_policy
need to be moved to the next patch when you introduce the policy
changes.

Tyler

> -- 
> 2.17.1
> 

Re: [PATCH v7 4/8] IMA: add policy rule to measure critical data

[Tyler Hicks]

On 2020-12-09 11:42:08, Tushar Sugandhi wrote:
> A new IMA policy rule is needed for the IMA hook
> ima_measure_critical_data() and the corresponding func CRITICAL_DATA for
> measuring the input buffer. The policy rule should ensure the buffer
> would get measured only when the policy rule allows the action. The
> policy rule should also support the necessary constraints (flags etc.)
> for integrity critical buffer data measurements.
> 
> Add a policy rule to define the constraints for restricting integrity
> critical data measurements.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> ---
>  security/integrity/ima/ima_policy.c | 35 +++++++++++++++++++++++++----
>  1 file changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 2a0c0603626e..9a8ee80a3128 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -34,6 +34,7 @@
>  #define IMA_PCR		0x0100
>  #define IMA_FSNAME	0x0200
>  #define IMA_KEYRINGS	0x0400
> +#define IMA_DATA_SOURCE	0x0800

You introduce data_source= in the next patch. This macro shouldn't be
added until the next patch.

>  
>  #define UNKNOWN		0
>  #define MEASURE		0x0001	/* same as IMA_MEASURE */
> @@ -85,6 +86,7 @@ struct ima_rule_entry {
>  	} lsm[MAX_LSM_RULES];
>  	char *fsname;
>  	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
> +	struct ima_rule_opt_list *data_source; /* Measure data from this source */
>  	struct ima_template_desc *template;
>  };
>  
> @@ -479,6 +481,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
>  		else
>  			opt_list = rule->keyrings;
>  		break;
> +	case CRITICAL_DATA:
> +		if (!rule->data_source)
> +			return true;
> +		else
> +			opt_list = rule->data_source;

If you take my suggestions on patch #1, remove the else and simply
assign opt_list here, too.

> +		break;
>  	default:
>  		break;
>  	}
> @@ -518,13 +526,19 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>  {
>  	int i;
>  
> -	if (func == KEY_CHECK) {
> -		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
> -			ima_match_rule_data(rule, func_data, cred);
> -	}
>  	if ((rule->flags & IMA_FUNC) &&
>  	    (rule->func != func && func != POST_SETATTR))
>  		return false;
> +
> +	switch (func) {
> +	case KEY_CHECK:
> +	case CRITICAL_DATA:
> +		return ((rule->func == func) &&
> +			ima_match_rule_data(rule, func_data, cred));
> +	default:
> +		break;
> +	}
> +
>  	if ((rule->flags & IMA_MASK) &&
>  	    (rule->mask != mask && func != POST_SETATTR))
>  		return false;
> @@ -1119,6 +1133,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
>  		if (ima_rule_contains_lsm_cond(entry))
>  			return false;
>  
> +		break;
> +	case CRITICAL_DATA:
> +		if (entry->action & ~(MEASURE | DONT_MEASURE))
> +			return false;
> +
> +		if (!(entry->flags & IMA_DATA_SOURCE) ||
> +		    (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
> +		    IMA_DATA_SOURCE)))

IMA_DATA_SOURCE shouldn't exist in this patch. This isn't the right
indentation, either. See how IMA_KEYRINGS is indented in the KEY_CHECK
case above.

Tyler

> +			return false;
> +
> +		if (ima_rule_contains_lsm_cond(entry))
> +			return false;
> +
>  		break;
>  	default:
>  		return false;
> -- 
> 2.17.1
> 

Re: [PATCH v7 5/8] IMA: limit critical data measurement based on a label

[Tyler Hicks]

On 2020-12-09 11:42:09, Tushar Sugandhi wrote:
> System administrators should be able to limit which kernel subsystems
> they want to measure the critical data for. To enable that, an IMA policy
> condition to choose specific kernel subsystems is needed. This policy
> condition would constrain the measurement of the critical data based on
> a label for the given subsystems.
> 
> Add a new IMA policy condition - "data_source:=" to the IMA func
> CRITICAL_DATA to allow measurement of various kernel subsystems. This
> policy condition would enable the system administrators to restrict the
> measurement to the labels listed in "data_source:=".
> 
> Limit the measurement to the labels that are specified in the IMA
> policy - CRITICAL_DATA+"data_source:=". If "data_sources:=" is not
> provided with the func CRITICAL_DATA, the data from all the
> supported kernel subsystems is measured.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>

This patch will look good once all the IMA_DATA_SOURCE stuff is moved
over from patch #4.

Tyler

> ---
>  Documentation/ABI/testing/ima_policy |  2 ++
>  security/integrity/ima/ima_policy.c  | 26 +++++++++++++++++++++++++-
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index 6ec7daa87cba..0f4ee9e0a455 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -52,6 +52,8 @@ Description:
>  			template:= name of a defined IMA template type
>  			(eg, ima-ng). Only valid when action is "measure".
>  			pcr:= decimal value
> +			data_source:= [label]
> +			label:= a unique string used for grouping and limiting critical data.
>  
>  		  default policy:
>  			# PROC_SUPER_MAGIC
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 9a8ee80a3128..7486d09a3f60 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -934,7 +934,7 @@ enum {
>  	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
>  	Opt_appraise_type, Opt_appraise_flag,
>  	Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
> -	Opt_err
> +	Opt_data_source, Opt_err
>  };
>  
>  static const match_table_t policy_tokens = {
> @@ -971,6 +971,7 @@ static const match_table_t policy_tokens = {
>  	{Opt_pcr, "pcr=%s"},
>  	{Opt_template, "template=%s"},
>  	{Opt_keyrings, "keyrings=%s"},
> +	{Opt_data_source, "data_source=%s"},
>  	{Opt_err, NULL}
>  };
>  
> @@ -1350,6 +1351,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  
>  			entry->flags |= IMA_KEYRINGS;
>  			break;
> +		case Opt_data_source:
> +			ima_log_string(ab, "data_source", args[0].from);
> +
> +			if (entry->data_source) {
> +				result = -EINVAL;
> +				break;
> +			}
> +
> +			entry->data_source = ima_alloc_rule_opt_list(args);
> +			if (IS_ERR(entry->data_source)) {
> +				result = PTR_ERR(entry->data_source);
> +				entry->data_source = NULL;
> +				break;
> +			}
> +
> +			entry->flags |= IMA_DATA_SOURCE;
> +			break;
>  		case Opt_fsuuid:
>  			ima_log_string(ab, "fsuuid", args[0].from);
>  
> @@ -1730,6 +1748,12 @@ int ima_policy_show(struct seq_file *m, void *v)
>  		seq_puts(m, " ");
>  	}
>  
> +	if (entry->flags & IMA_DATA_SOURCE) {
> +		seq_puts(m, "data_source=");
> +		ima_show_rule_opt_list(m, entry->data_source);
> +		seq_puts(m, " ");
> +	}
> +
>  	if (entry->flags & IMA_PCR) {
>  		snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
>  		seq_printf(m, pt(Opt_pcr), tbuf);
> -- 
> 2.17.1
> 

Re: [PATCH v7 6/8] IMA: extend critical data hook to limit the measurement based on a label

[Tyler Hicks]

On 2020-12-09 11:42:10, Tushar Sugandhi wrote:
> The IMA hook ima_measure_critical_data() does not support a way to
> specify the source of the critical data provider. Thus, the data
> measurement cannot be constrained based on the data source label
> in the IMA policy.
> 
> Extend the IMA hook ima_measure_critical_data() to support passing 
> the data source label as an input parameter, so that the policy rule can
> be used to limit the measurements based on the label.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

Tyler

> ---
>  include/linux/ima.h               |  6 ++++--
>  security/integrity/ima/ima_main.c | 11 ++++++++---
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 675f54db6264..6434287a81cd 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -30,7 +30,8 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
>  extern void ima_post_path_mknod(struct dentry *dentry);
>  extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
>  extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
> -extern void ima_measure_critical_data(const char *event_name,
> +extern void ima_measure_critical_data(const char *event_data_source,
> +				      const char *event_name,
>  				      const void *buf, int buf_len,
>  				      bool measure_buf_hash);
>  
> @@ -125,7 +126,8 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
>  }
>  
>  static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
> -static inline void ima_measure_critical_data(const char *event_name,
> +static inline void ima_measure_critical_data(const char *event_data_source,
> +					     const char *event_name,
>  					     const void *buf, int buf_len,
>  					     bool measure_buf_hash) {}
>  #endif /* CONFIG_IMA */
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index ae59f4a4dd70..7c633901f441 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -924,6 +924,7 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>  
>  /**
>   * ima_measure_critical_data - measure kernel integrity critical data
> + * @event_data_source: kernel data source being measured
>   * @event_name: event name to be used for the buffer entry
>   * @buf: pointer to buffer containing data to measure
>   * @buf_len: length of buffer(in bytes)
> @@ -932,6 +933,9 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>   * Measure the kernel subsystem data, critical to the integrity of the kernel,
>   * into the IMA log and extend the @pcr.
>   *
> + * Use @event_data_source to describe the kernel data source for the buffer
> + * being measured.
> + *
>   * Use @event_name to describe the state/buffer data change.
>   * Examples of critical data (buf) could be kernel in-memory r/o structures,
>   * hash of the memory structures, or data that represents subsystem state
> @@ -944,17 +948,18 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>   *
>   * The data (buf) can only be measured, not appraised.
>   */
> -void ima_measure_critical_data(const char *event_name,
> +void ima_measure_critical_data(const char *event_data_source,
> +			       const char *event_name,
>  			       const void *buf, int buf_len,
>  			       bool measure_buf_hash)
>  {
> -	if (!event_name || !buf || !buf_len) {
> +	if (!event_name || !event_data_source || !buf || !buf_len) {
>  		pr_err("Invalid arguments passed to %s().\n", __func__);
>  		return;
>  	}
>  
>  	process_buffer_measurement(NULL, buf, buf_len, event_name,
> -				   CRITICAL_DATA, 0, NULL,
> +				   CRITICAL_DATA, 0, event_data_source,
>  				   measure_buf_hash);
>  }
>  
> -- 
> 2.17.1
> 

Re: [PATCH v7 7/8] IMA: define a builtin critical data measurement policy

[Tyler Hicks]

On 2020-12-09 11:42:11, Tushar Sugandhi wrote:
> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> 
> Define a new critical data builtin policy to allow measuring
> early kernel integrity critical data before a custom IMA policy
> is loaded.
> 
> Add critical data to built-in IMA rules if the kernel command line
> contains "ima_policy=critical_data".
> 
> Update the documentation on kernel parameters to document
> the new critical data builtin policy.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

Tyler

> ---
>  Documentation/admin-guide/kernel-parameters.txt |  5 ++++-
>  security/integrity/ima/ima_policy.c             | 12 ++++++++++++
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 526d65d8573a..6034d75c3ca0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1746,7 +1746,7 @@
>  	ima_policy=	[IMA]
>  			The builtin policies to load during IMA setup.
>  			Format: "tcb | appraise_tcb | secure_boot |
> -				 fail_securely"
> +				 fail_securely | critical_data"
>  
>  			The "tcb" policy measures all programs exec'd, files
>  			mmap'd for exec, and all files opened with the read
> @@ -1765,6 +1765,9 @@
>  			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
>  			flag.
>  
> +			The "critical_data" policy measures kernel integrity
> +			critical data.
> +
>  	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
>  			Load a policy which meets the needs of the Trusted
>  			Computing Base.  This means IMA will measure all
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 7486d09a3f60..37ca16a9e65f 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -206,6 +206,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
>  	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
>  };
>  
> +static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
> +	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
> +};
> +
>  /* An array of architecture specific rules */
>  static struct ima_rule_entry *arch_policy_entry __ro_after_init;
>  
> @@ -228,6 +232,7 @@ __setup("ima_tcb", default_measure_policy_setup);
>  
>  static bool ima_use_appraise_tcb __initdata;
>  static bool ima_use_secure_boot __initdata;
> +static bool ima_use_critical_data __initdata;
>  static bool ima_fail_unverifiable_sigs __ro_after_init;
>  static int __init policy_setup(char *str)
>  {
> @@ -242,6 +247,8 @@ static int __init policy_setup(char *str)
>  			ima_use_appraise_tcb = true;
>  		else if (strcmp(p, "secure_boot") == 0)
>  			ima_use_secure_boot = true;
> +		else if (strcmp(p, "critical_data") == 0)
> +			ima_use_critical_data = true;
>  		else if (strcmp(p, "fail_securely") == 0)
>  			ima_fail_unverifiable_sigs = true;
>  		else
> @@ -875,6 +882,11 @@ void __init ima_init_policy(void)
>  			  ARRAY_SIZE(default_appraise_rules),
>  			  IMA_DEFAULT_POLICY);
>  
> +	if (ima_use_critical_data)
> +		add_rules(critical_data_rules,
> +			  ARRAY_SIZE(critical_data_rules),
> +			  IMA_DEFAULT_POLICY);
> +
>  	ima_update_policy_flag();
>  }
>  
> -- 
> 2.17.1
> 

Re: [PATCH v7 1/8] IMA: generalize keyring specific measurement constructs

[Tushar Sugandhi]

On 2020-12-10 2:14 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:05, Tushar Sugandhi wrote:
>> IMA functions such as ima_match_keyring(), process_buffer_measurement(),
>> ima_match_policy() etc. handle data specific to keyrings. Currently,
>> these constructs are not generic to handle any func specific data.
>> This makes it harder to extend them without code duplication.
>>
>> Refactor the keyring specific measurement constructs to be generic and
>> reusable in other measurement scenarios.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> 
> I've got a few code cleanup suggestions to ima_match_rule_data() below
> but the current patch is fine:
> 
> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> 
>> ---
>>   security/integrity/ima/ima.h        |  6 ++--
>>   security/integrity/ima/ima_api.c    |  6 ++--
>>   security/integrity/ima/ima_main.c   |  6 ++--
>>   security/integrity/ima/ima_policy.c | 49 ++++++++++++++++++-----------
>>   4 files changed, 40 insertions(+), 27 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index 8e8b1e3cb847..e5622ce8cbb1 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -256,7 +256,7 @@ static inline void ima_process_queued_keys(void) {}
>>   int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>>   		   int mask, enum ima_hooks func, int *pcr,
>>   		   struct ima_template_desc **template_desc,
>> -		   const char *keyring);
>> +		   const char *func_data);
>>   int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
>>   int ima_collect_measurement(struct integrity_iint_cache *iint,
>>   			    struct file *file, void *buf, loff_t size,
>> @@ -268,7 +268,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>>   			   struct ima_template_desc *template_desc);
>>   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   				const char *eventname, enum ima_hooks func,
>> -				int pcr, const char *keyring);
>> +				int pcr, const char *func_data);
>>   void ima_audit_measurement(struct integrity_iint_cache *iint,
>>   			   const unsigned char *filename);
>>   int ima_alloc_init_template(struct ima_event_data *event_data,
>> @@ -284,7 +284,7 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
>>   int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>>   		     enum ima_hooks func, int mask, int flags, int *pcr,
>>   		     struct ima_template_desc **template_desc,
>> -		     const char *keyring);
>> +		     const char *func_data);
>>   void ima_init_policy(void);
>>   void ima_update_policy(void);
>>   void ima_update_policy_flag(void);
>> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
>> index 4f39fb93f278..af218babd198 100644
>> --- a/security/integrity/ima/ima_api.c
>> +++ b/security/integrity/ima/ima_api.c
>> @@ -170,7 +170,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>>    * @func: caller identifier
>>    * @pcr: pointer filled in if matched measure policy sets pcr=
>>    * @template_desc: pointer filled in if matched measure policy sets template=
>> - * @keyring: keyring name used to determine the action
>> + * @func_data: private data specific to @func, can be NULL.
>>    *
>>    * The policy is defined in terms of keypairs:
>>    *		subj=, obj=, type=, func=, mask=, fsmagic=
>> @@ -186,14 +186,14 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>>   int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>>   		   int mask, enum ima_hooks func, int *pcr,
>>   		   struct ima_template_desc **template_desc,
>> -		   const char *keyring)
>> +		   const char *func_data)
>>   {
>>   	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
>>   
>>   	flags &= ima_policy_flag;
>>   
>>   	return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
>> -				template_desc, keyring);
>> +				template_desc, func_data);
>>   }
>>   
>>   /*
>> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
>> index 68956e884403..e76ef4bfd0f4 100644
>> --- a/security/integrity/ima/ima_main.c
>> +++ b/security/integrity/ima/ima_main.c
>> @@ -786,13 +786,13 @@ int ima_post_load_data(char *buf, loff_t size,
>>    * @eventname: event name to be used for the buffer entry.
>>    * @func: IMA hook
>>    * @pcr: pcr to extend the measurement
>> - * @keyring: keyring name to determine the action to be performed
>> + * @func_data: private data specific to @func, can be NULL.
>>    *
>>    * Based on policy, the buffer is measured into the ima log.
>>    */
>>   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   				const char *eventname, enum ima_hooks func,
>> -				int pcr, const char *keyring)
>> +				int pcr, const char *func_data)
>>   {
>>   	int ret = 0;
>>   	const char *audit_cause = "ENOMEM";
>> @@ -831,7 +831,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   	if (func) {
>>   		security_task_getsecid(current, &secid);
>>   		action = ima_get_action(inode, current_cred(), secid, 0, func,
>> -					&pcr, &template, keyring);
>> +					&pcr, &template, func_data);
>>   		if (!(action & IMA_MEASURE))
>>   			return;
>>   	}
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 823a0c1379cb..25419c7ff50b 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -453,30 +453,44 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
>>   }
>>   
>>   /**
>> - * ima_match_keyring - determine whether the keyring matches the measure rule
>> - * @rule: a pointer to a rule
>> - * @keyring: name of the keyring to match against the measure rule
>> + * ima_match_rule_data - determine whether the given func_data matches
>> + *			 the measure rule data
>> + * @rule: IMA policy rule
>> + * @func_data: data to match against the measure rule data
>>    * @cred: a pointer to a credentials structure for user validation
>>    *
>> - * Returns true if keyring matches one in the rule, false otherwise.
>> + * Returns true if func_data matches one in the rule, false otherwise.
>>    */
>> -static bool ima_match_keyring(struct ima_rule_entry *rule,
>> -			      const char *keyring, const struct cred *cred)
>> +static bool ima_match_rule_data(struct ima_rule_entry *rule,
>> +				const char *func_data,
>> +				const struct cred *cred)
>>   {
>> +	const struct ima_rule_opt_list *opt_list = NULL;
>>   	bool matched = false;
>>   	size_t i;
>>   
>>   	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
>>   		return false;
>>   
>> -	if (!rule->keyrings)
>> -		return true;
>> +	switch (rule->func) {
>> +	case KEY_CHECK:
>> +		if (!rule->keyrings)
>> +			return true;
>> +		else
>> +			opt_list = rule->keyrings;
> 
> You return if rule->keyrings is NULL so drop this else and simply make
> the opt_list assignment.
> 
Will do.
>> +		break;
>> +	default:
>> +		break;
> 
> I would like to see the 'return false;' happen immediately here instead
> of waiting for the opt_list check below.
Will do.
> 
>> +	}
>>   
>> -	if (!keyring)
>> +	if (!func_data)
>> +		return false;
>> +
>> +	if (!opt_list)
>>   		return false;
> 
> If you return false in the 'default:' case above, you can just remove this
> entire conditional because you'll be assigning opt_list in all of the
> valid cases of the switch statement.
> 
Yup. Agreed. Will do.
~Tushar
> Tyler
> 
>>   
>> -	for (i = 0; i < rule->keyrings->count; i++) {
>> -		if (!strcmp(rule->keyrings->items[i], keyring)) {
>> +	for (i = 0; i < opt_list->count; i++) {
>> +		if (!strcmp(opt_list->items[i], func_data)) {
>>   			matched = true;
>>   			break;
>>   		}
>> @@ -493,20 +507,20 @@ static bool ima_match_keyring(struct ima_rule_entry *rule,
>>    * @secid: the secid of the task to be validated
>>    * @func: LIM hook identifier
>>    * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
>> - * @keyring: keyring name to check in policy for KEY_CHECK func
>> + * @func_data: private data specific to @func, can be NULL.
>>    *
>>    * Returns true on rule match, false on failure.
>>    */
>>   static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>>   			    const struct cred *cred, u32 secid,
>>   			    enum ima_hooks func, int mask,
>> -			    const char *keyring)
>> +			    const char *func_data)
>>   {
>>   	int i;
>>   
>>   	if (func == KEY_CHECK) {
>>   		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
>> -		       ima_match_keyring(rule, keyring, cred);
>> +			ima_match_rule_data(rule, func_data, cred);
>>   	}
>>   	if ((rule->flags & IMA_FUNC) &&
>>   	    (rule->func != func && func != POST_SETATTR))
>> @@ -610,8 +624,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>>    * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
>>    * @pcr: set the pcr to extend
>>    * @template_desc: the template that should be used for this rule
>> - * @keyring: the keyring name, if given, to be used to check in the policy.
>> - *           keyring can be NULL if func is anything other than KEY_CHECK.
>> + * @func_data: private data specific to @func, can be NULL.
>>    *
>>    * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
>>    * conditions.
>> @@ -623,7 +636,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>>   int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>>   		     enum ima_hooks func, int mask, int flags, int *pcr,
>>   		     struct ima_template_desc **template_desc,
>> -		     const char *keyring)
>> +		     const char *func_data)
>>   {
>>   	struct ima_rule_entry *entry;
>>   	int action = 0, actmask = flags | (flags << 1);
>> @@ -638,7 +651,7 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>>   			continue;
>>   
>>   		if (!ima_match_rules(entry, inode, cred, secid, func, mask,
>> -				     keyring))
>> +				     func_data))
>>   			continue;
>>   
>>   		action |= entry->flags & IMA_ACTION_FLAGS;
>> -- 
>> 2.17.1
>>

Re: [PATCH v7 2/8] IMA: add support to measure buffer data hash

[Tushar Sugandhi]

On 2020-12-10 2:38 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:06, Tushar Sugandhi wrote:
>> The original IMA buffer data measurement sizes were small (e.g. boot
>> command line), but the new buffer data measurement use cases have data
>> sizes that are a lot larger.  Just as IMA measures the file data hash,
>> not the file data, IMA should similarly support the option for measuring
>> the hash of the buffer data.
>>
>> Measuring in-memory buffer-data/buffer-data-hash is different than
>> measuring file-data/file-data-hash. For the file, IMA stores the
>> measurements in both measurement log and the file's extended attribute -
>> which can later be used for appraisal as well. For buffer, the
>> measurements are only stored in the IMA log, since the buffer has no
>> extended attributes associated with it.
>>
>> Introduce a boolean parameter measure_buf_hash to support measuring
>> hash of a buffer, which would be much smaller, instead of the buffer
>> itself.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>> ---
>>   security/integrity/ima/ima.h                 |  3 +-
>>   security/integrity/ima/ima_appraise.c        |  2 +-
>>   security/integrity/ima/ima_asymmetric_keys.c |  2 +-
>>   security/integrity/ima/ima_main.c            | 36 +++++++++++++++++---
>>   security/integrity/ima/ima_queue_keys.c      |  3 +-
>>   5 files changed, 38 insertions(+), 8 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index e5622ce8cbb1..fa3044a7539f 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>>   			   struct ima_template_desc *template_desc);
>>   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   				const char *eventname, enum ima_hooks func,
>> -				int pcr, const char *func_data);
>> +				int pcr, const char *func_data,
>> +				bool measure_buf_hash);
>>   void ima_audit_measurement(struct integrity_iint_cache *iint,
>>   			   const unsigned char *filename);
>>   int ima_alloc_init_template(struct ima_event_data *event_data,
>> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
>> index 8361941ee0a1..46ffa38bab12 100644
>> --- a/security/integrity/ima/ima_appraise.c
>> +++ b/security/integrity/ima/ima_appraise.c
>> @@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
>>   		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
>>   			process_buffer_measurement(NULL, digest, digestsize,
>>   						   "blacklisted-hash", NONE,
>> -						   pcr, NULL);
>> +						   pcr, NULL, false);
>>   	}
>>   
>>   	return rc;
>> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
>> index 1c68c500c26f..a74095793936 100644
>> --- a/security/integrity/ima/ima_asymmetric_keys.c
>> +++ b/security/integrity/ima/ima_asymmetric_keys.c
>> @@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>>   	 */
>>   	process_buffer_measurement(NULL, payload, payload_len,
>>   				   keyring->description, KEY_CHECK, 0,
>> -				   keyring->description);
>> +				   keyring->description, false);
>>   }
>> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
>> index e76ef4bfd0f4..03aad13e9e70 100644
>> --- a/security/integrity/ima/ima_main.c
>> +++ b/security/integrity/ima/ima_main.c
>> @@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size,
>>   }
>>   
>>   /*
>> - * process_buffer_measurement - Measure the buffer to ima log.
>> + * process_buffer_measurement - Measure the buffer or the buffer data hash
>>    * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
>>    * @buf: pointer to the buffer that needs to be added to the log.
>>    * @size: size of buffer(in bytes).
>> @@ -787,12 +787,23 @@ int ima_post_load_data(char *buf, loff_t size,
>>    * @func: IMA hook
>>    * @pcr: pcr to extend the measurement
>>    * @func_data: private data specific to @func, can be NULL.
>> + * @measure_buf_hash: measure buffer hash
>>    *
>> - * Based on policy, the buffer is measured into the ima log.
>> + * Measure the buffer into the IMA log, and extend the @pcr.
>> + *
>> + * Determine what buffers are allowed to be measured, based on the policy rules
>> + * and the IMA hook passed using @func.
>> + *
>> + * Use @func_data, if provided, to match against the measurement policy rule
>> + * data for @func.
>> + *
>> + * If @measure_buf_hash is set to true - measure hash of the buffer data,
>> + * else measure the buffer data itself.
>>    */
>>   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   				const char *eventname, enum ima_hooks func,
>> -				int pcr, const char *func_data)
>> +				int pcr, const char *func_data,
>> +				bool measure_buf_hash)
>>   {
>>   	int ret = 0;
>>   	const char *audit_cause = "ENOMEM";
>> @@ -807,6 +818,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   		struct ima_digest_data hdr;
>>   		char digest[IMA_MAX_DIGEST_SIZE];
>>   	} hash = {};
>> +	char buf_hash[IMA_MAX_DIGEST_SIZE];
>> +	int buf_hash_len = hash_digest_size[ima_hash_algo];
>>   	int violation = 0;
>>   	int action = 0;
>>   	u32 secid;
>> @@ -849,6 +862,20 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>>   		goto out;
>>   	}
>>   
>> +	if (measure_buf_hash) {
>> +		memcpy(buf_hash, hash.hdr.digest, buf_hash_len);
>> +
>> +		ret = ima_calc_buffer_hash(buf_hash, buf_hash_len,
>> +					   iint.ima_hash);
>> +		if (ret < 0) {
>> +			audit_cause = "measure_buf_hash_error";
>> +			goto out;
>> +		}
>> +
>> +		event_data.buf = buf_hash;
>> +		event_data.buf_len = buf_hash_len;
>> +	}
>> +
>>   	ret = ima_alloc_init_template(&event_data, &entry, template);
>>   	if (ret < 0) {
>>   		audit_cause = "alloc_entry";
> 
> A few more lines below, not present in this context, is a call to
> ima_store_template() with buf as the fourth parameter passed in. That
> parameter eventually makes its way to integrity_audit_message() and ends
> up as part of an audit message as the value of the "name=" field. This
> is usually a filename, the name of a key, or a kexec cmdline. In the
> case of measuring SELinux policy, do we want the entire buf to be
> included in the audit message?
> 
> Tyler
> 
Great catch.
We obviously don't want to include the entire buf in the audit message,
especially when the measure_buf_hash is set to true. (the buffer being
measured is expected to be large in that case)

How about the following? Does it look ok to you? Mimi?

if (measure_buf_hash)
     ret = ima_store_template(entry, violation, NULL, buf_hash, pcr);
else
     ret = ima_store_template(entry, violation, NULL, buf, pcr);

~Tushar

Re: [PATCH v7 6/8] IMA: extend critical data hook to limit the measurement based on a label

[Tushar Sugandhi]

On 2020-12-10 3:19 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:10, Tushar Sugandhi wrote:
>> The IMA hook ima_measure_critical_data() does not support a way to
>> specify the source of the critical data provider. Thus, the data
>> measurement cannot be constrained based on the data source label
>> in the IMA policy.
>>
>> Extend the IMA hook ima_measure_critical_data() to support passing
>> the data source label as an input parameter, so that the policy rule can
>> be used to limit the measurements based on the label.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> 
> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> 
> Tyler
> 
Thanks for the review.
~Tushar

Re: [PATCH v7 7/8] IMA: define a builtin critical data measurement policy

[Tushar Sugandhi]

On 2020-12-10 3:22 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:11, Tushar Sugandhi wrote:
>> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>>
>> Define a new critical data builtin policy to allow measuring
>> early kernel integrity critical data before a custom IMA policy
>> is loaded.
>>
>> Add critical data to built-in IMA rules if the kernel command line
>> contains "ima_policy=critical_data".
>>
>> Update the documentation on kernel parameters to document
>> the new critical data builtin policy.
>>
>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> 
> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> 
> Tyler
> 
Thanks for the review.

~Tushar

Re: [PATCH v7 2/8] IMA: add support to measure buffer data hash

[Tyler Hicks]

On 2020-12-10 17:21:19, Tushar Sugandhi wrote:
> 
> 
> On 2020-12-10 2:38 p.m., Tyler Hicks wrote:
> > On 2020-12-09 11:42:06, Tushar Sugandhi wrote:
> > > The original IMA buffer data measurement sizes were small (e.g. boot
> > > command line), but the new buffer data measurement use cases have data
> > > sizes that are a lot larger.  Just as IMA measures the file data hash,
> > > not the file data, IMA should similarly support the option for measuring
> > > the hash of the buffer data.
> > > 
> > > Measuring in-memory buffer-data/buffer-data-hash is different than
> > > measuring file-data/file-data-hash. For the file, IMA stores the
> > > measurements in both measurement log and the file's extended attribute -
> > > which can later be used for appraisal as well. For buffer, the
> > > measurements are only stored in the IMA log, since the buffer has no
> > > extended attributes associated with it.
> > > 
> > > Introduce a boolean parameter measure_buf_hash to support measuring
> > > hash of a buffer, which would be much smaller, instead of the buffer
> > > itself.
> > > 
> > > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> > > ---
> > >   security/integrity/ima/ima.h                 |  3 +-
> > >   security/integrity/ima/ima_appraise.c        |  2 +-
> > >   security/integrity/ima/ima_asymmetric_keys.c |  2 +-
> > >   security/integrity/ima/ima_main.c            | 36 +++++++++++++++++---
> > >   security/integrity/ima/ima_queue_keys.c      |  3 +-
> > >   5 files changed, 38 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> > > index e5622ce8cbb1..fa3044a7539f 100644
> > > --- a/security/integrity/ima/ima.h
> > > +++ b/security/integrity/ima/ima.h
> > > @@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
> > >   			   struct ima_template_desc *template_desc);
> > >   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
> > >   				const char *eventname, enum ima_hooks func,
> > > -				int pcr, const char *func_data);
> > > +				int pcr, const char *func_data,
> > > +				bool measure_buf_hash);
> > >   void ima_audit_measurement(struct integrity_iint_cache *iint,
> > >   			   const unsigned char *filename);
> > >   int ima_alloc_init_template(struct ima_event_data *event_data,
> > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> > > index 8361941ee0a1..46ffa38bab12 100644
> > > --- a/security/integrity/ima/ima_appraise.c
> > > +++ b/security/integrity/ima/ima_appraise.c
> > > @@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
> > >   		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
> > >   			process_buffer_measurement(NULL, digest, digestsize,
> > >   						   "blacklisted-hash", NONE,
> > > -						   pcr, NULL);
> > > +						   pcr, NULL, false);
> > >   	}
> > >   	return rc;
> > > diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
> > > index 1c68c500c26f..a74095793936 100644
> > > --- a/security/integrity/ima/ima_asymmetric_keys.c
> > > +++ b/security/integrity/ima/ima_asymmetric_keys.c
> > > @@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
> > >   	 */
> > >   	process_buffer_measurement(NULL, payload, payload_len,
> > >   				   keyring->description, KEY_CHECK, 0,
> > > -				   keyring->description);
> > > +				   keyring->description, false);
> > >   }
> > > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> > > index e76ef4bfd0f4..03aad13e9e70 100644
> > > --- a/security/integrity/ima/ima_main.c
> > > +++ b/security/integrity/ima/ima_main.c
> > > @@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size,
> > >   }
> > >   /*
> > > - * process_buffer_measurement - Measure the buffer to ima log.
> > > + * process_buffer_measurement - Measure the buffer or the buffer data hash
> > >    * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
> > >    * @buf: pointer to the buffer that needs to be added to the log.
> > >    * @size: size of buffer(in bytes).
> > > @@ -787,12 +787,23 @@ int ima_post_load_data(char *buf, loff_t size,
> > >    * @func: IMA hook
> > >    * @pcr: pcr to extend the measurement
> > >    * @func_data: private data specific to @func, can be NULL.
> > > + * @measure_buf_hash: measure buffer hash
> > >    *
> > > - * Based on policy, the buffer is measured into the ima log.
> > > + * Measure the buffer into the IMA log, and extend the @pcr.
> > > + *
> > > + * Determine what buffers are allowed to be measured, based on the policy rules
> > > + * and the IMA hook passed using @func.
> > > + *
> > > + * Use @func_data, if provided, to match against the measurement policy rule
> > > + * data for @func.
> > > + *
> > > + * If @measure_buf_hash is set to true - measure hash of the buffer data,
> > > + * else measure the buffer data itself.
> > >    */
> > >   void process_buffer_measurement(struct inode *inode, const void *buf, int size,
> > >   				const char *eventname, enum ima_hooks func,
> > > -				int pcr, const char *func_data)
> > > +				int pcr, const char *func_data,
> > > +				bool measure_buf_hash)
> > >   {
> > >   	int ret = 0;
> > >   	const char *audit_cause = "ENOMEM";
> > > @@ -807,6 +818,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
> > >   		struct ima_digest_data hdr;
> > >   		char digest[IMA_MAX_DIGEST_SIZE];
> > >   	} hash = {};
> > > +	char buf_hash[IMA_MAX_DIGEST_SIZE];
> > > +	int buf_hash_len = hash_digest_size[ima_hash_algo];
> > >   	int violation = 0;
> > >   	int action = 0;
> > >   	u32 secid;
> > > @@ -849,6 +862,20 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
> > >   		goto out;
> > >   	}
> > > +	if (measure_buf_hash) {
> > > +		memcpy(buf_hash, hash.hdr.digest, buf_hash_len);
> > > +
> > > +		ret = ima_calc_buffer_hash(buf_hash, buf_hash_len,
> > > +					   iint.ima_hash);
> > > +		if (ret < 0) {
> > > +			audit_cause = "measure_buf_hash_error";
> > > +			goto out;
> > > +		}
> > > +
> > > +		event_data.buf = buf_hash;
> > > +		event_data.buf_len = buf_hash_len;
> > > +	}
> > > +
> > >   	ret = ima_alloc_init_template(&event_data, &entry, template);
> > >   	if (ret < 0) {
> > >   		audit_cause = "alloc_entry";
> > 
> > A few more lines below, not present in this context, is a call to
> > ima_store_template() with buf as the fourth parameter passed in. That
> > parameter eventually makes its way to integrity_audit_message() and ends
> > up as part of an audit message as the value of the "name=" field. This
> > is usually a filename, the name of a key, or a kexec cmdline. In the
> > case of measuring SELinux policy, do we want the entire buf to be
> > included in the audit message?
> > 
> > Tyler
> > 
> Great catch.
> We obviously don't want to include the entire buf in the audit message,
> especially when the measure_buf_hash is set to true. (the buffer being
> measured is expected to be large in that case)
> 
> How about the following? Does it look ok to you? Mimi?
> 
> if (measure_buf_hash)
>     ret = ima_store_template(entry, violation, NULL, buf_hash, pcr);
> else
>     ret = ima_store_template(entry, violation, NULL, buf, pcr);

I think that looks fine. You could also just pass event_data.buf to
ima_store_template().

Tyler

> 
> ~Tushar
> 

Re: [PATCH v7 3/8] IMA: define a hook to measure kernel integrity critical data

[Tushar Sugandhi]

On 2020-12-10 3:02 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:07, Tushar Sugandhi wrote:
>> IMA provides capabilities to measure file data, and in-memory buffer
>> data. However, various data structures, policies, and states
>> stored in kernel memory also impact the integrity of the system.
>> Several kernel subsystems contain such integrity critical data. These
>> kernel subsystems help protect the integrity of a device. Currently,
>> IMA does not provide a generic function for kernel subsystems to measure
>> their integrity critical data.
>>   
>> Define a new IMA hook - ima_measure_critical_data to measure kernel
>> integrity critical data.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>> ---
>>   Documentation/ABI/testing/ima_policy |  2 +-
>>   include/linux/ima.h                  |  6 +++++
>>   security/integrity/ima/ima.h         |  1 +
>>   security/integrity/ima/ima_api.c     |  2 +-
>>   security/integrity/ima/ima_main.c    | 36 ++++++++++++++++++++++++++++
>>   security/integrity/ima/ima_policy.c  |  2 ++
>>   6 files changed, 47 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
>> index e35263f97fc1..6ec7daa87cba 100644
>> --- a/Documentation/ABI/testing/ima_policy
>> +++ b/Documentation/ABI/testing/ima_policy
>> @@ -32,7 +32,7 @@ Description:
>>   			func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK]MODULE_CHECK]
>>   			        [FIRMWARE_CHECK]
>>   				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
>> -				[KEXEC_CMDLINE] [KEY_CHECK]
>> +				[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
>>   			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
>>   			       [[^]MAY_EXEC]
>>   			fsmagic:= hex value
>> diff --git a/include/linux/ima.h b/include/linux/ima.h
>> index ac3d82f962f2..675f54db6264 100644
>> --- a/include/linux/ima.h
>> +++ b/include/linux/ima.h
>> @@ -30,6 +30,9 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
>>   extern void ima_post_path_mknod(struct dentry *dentry);
>>   extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
>>   extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
>> +extern void ima_measure_critical_data(const char *event_name,
>> +				      const void *buf, int buf_len,
>> +				      bool measure_buf_hash);
>>   
>>   #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
>>   extern void ima_appraise_parse_cmdline(void);
>> @@ -122,6 +125,9 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
>>   }
>>   
>>   static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
>> +static inline void ima_measure_critical_data(const char *event_name,
>> +					     const void *buf, int buf_len,
>> +					     bool measure_buf_hash) {}
>>   #endif /* CONFIG_IMA */
>>   
>>   #ifndef CONFIG_IMA_KEXEC
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index fa3044a7539f..7d9deda6a8b3 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -201,6 +201,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
>>   	hook(POLICY_CHECK, policy)			\
>>   	hook(KEXEC_CMDLINE, kexec_cmdline)		\
>>   	hook(KEY_CHECK, key)				\
>> +	hook(CRITICAL_DATA, critical_data)		\
>>   	hook(MAX_CHECK, none)
>>   
>>   #define __ima_hook_enumify(ENUM, str)	ENUM,
>> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
>> index af218babd198..9917e1730cb6 100644
>> --- a/security/integrity/ima/ima_api.c
>> +++ b/security/integrity/ima/ima_api.c
>> @@ -176,7 +176,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>>    *		subj=, obj=, type=, func=, mask=, fsmagic=
>>    *	subj,obj, and type: are LSM specific.
>>    *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
>> - *	| KEXEC_CMDLINE | KEY_CHECK
>> + *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
>>    *	mask: contains the permission mask
>>    *	fsmagic: hex value
>>    *
>> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
>> index 03aad13e9e70..ae59f4a4dd70 100644
>> --- a/security/integrity/ima/ima_main.c
>> +++ b/security/integrity/ima/ima_main.c
>> @@ -922,6 +922,42 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>>   	fdput(f);
>>   }
>>   
>> +/**
>> + * ima_measure_critical_data - measure kernel integrity critical data
>> + * @event_name: event name to be used for the buffer entry
>> + * @buf: pointer to buffer containing data to measure
>> + * @buf_len: length of buffer(in bytes)
>> + * @measure_buf_hash: measure buffer hash
>> + *
>> + * Measure the kernel subsystem data, critical to the integrity of the kernel,
>> + * into the IMA log and extend the @pcr.
>> + *
>> + * Use @event_name to describe the state/buffer data change.
>> + * Examples of critical data (buf) could be kernel in-memory r/o structures,
>                                   ^
> 				 @buf
> 
Will do.
>> + * hash of the memory structures, or data that represents subsystem state
>> + * change.
>> + *
>> + * If @measure_buf_hash is set to true - measure hash of the buffer data,
>> + * else measure the buffer data itself.
>> + * measure_buf_hash can be used to save space, if the data being measured
>        ^
>        @measure_buf_hash
> 
>> + * is too large.
>> + *
>> + * The data (buf) can only be measured, not appraised.
>                  ^
> 		@buf
> 
Will do.
>> + */
>> +void ima_measure_critical_data(const char *event_name,
>> +			       const void *buf, int buf_len,
>> +			       bool measure_buf_hash)
>> +{
>> +	if (!event_name || !buf || !buf_len) {
>> +		pr_err("Invalid arguments passed to %s().\n", __func__);
> 
> This is a problem for the developer making use of the
> ima_measure_critical_data() API and shouldn't be logged, IMO, because a
> user/admin can do nothing about it. I think the error message should be
> dropped.
> 
>> +		return;
>> +	}
>> +
>> +	process_buffer_measurement(NULL, buf, buf_len, event_name,
>> +				   CRITICAL_DATA, 0, NULL,
>> +				   measure_buf_hash);
>> +}
>> +
>>   static int __init init_ima(void)
>>   {
>>   	int error;
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 25419c7ff50b..2a0c0603626e 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -1251,6 +1251,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>>   			else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) &&
>>   				 strcmp(args[0].from, "KEY_CHECK") == 0)
>>   				entry->func = KEY_CHECK;
>> +			else if (strcmp(args[0].from, "CRITICAL_DATA") == 0)
>> +				entry->func = CRITICAL_DATA;
>>   			else
>>   				result = -EINVAL;
>>   			if (!result)
> 
> This hunk and the above change to Documentation/ABI/testing/ima_policy
> need to be moved to the next patch when you introduce the policy
> changes.
> 
Will do.
~Tushar
> Tyler
> 
>> -- 
>> 2.17.1
>>

Re: [PATCH v7 4/8] IMA: add policy rule to measure critical data

[Tushar Sugandhi]

On 2020-12-10 3:10 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:08, Tushar Sugandhi wrote:
>> A new IMA policy rule is needed for the IMA hook
>> ima_measure_critical_data() and the corresponding func CRITICAL_DATA for
>> measuring the input buffer. The policy rule should ensure the buffer
>> would get measured only when the policy rule allows the action. The
>> policy rule should also support the necessary constraints (flags etc.)
>> for integrity critical buffer data measurements.
>>
>> Add a policy rule to define the constraints for restricting integrity
>> critical data measurements.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>> ---
>>   security/integrity/ima/ima_policy.c | 35 +++++++++++++++++++++++++----
>>   1 file changed, 31 insertions(+), 4 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 2a0c0603626e..9a8ee80a3128 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -34,6 +34,7 @@
>>   #define IMA_PCR		0x0100
>>   #define IMA_FSNAME	0x0200
>>   #define IMA_KEYRINGS	0x0400
>> +#define IMA_DATA_SOURCE	0x0800
> 
> You introduce data_source= in the next patch. This macro shouldn't be
> added until the next patch.
> 
Ok I will move IMA_DATA_SOURCE to the next patch.

>>   
>>   #define UNKNOWN		0
>>   #define MEASURE		0x0001	/* same as IMA_MEASURE */
>> @@ -85,6 +86,7 @@ struct ima_rule_entry {
>>   	} lsm[MAX_LSM_RULES];
>>   	char *fsname;
>>   	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
>> +	struct ima_rule_opt_list *data_source; /* Measure data from this source */
>>   	struct ima_template_desc *template;
>>   };
>>   
>> @@ -479,6 +481,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
>>   		else
>>   			opt_list = rule->keyrings;
>>   		break;
>> +	case CRITICAL_DATA:
>> +		if (!rule->data_source)
>> +			return true;
>> +		else
>> +			opt_list = rule->data_source;
> 
> If you take my suggestions on patch #1, remove the else and simply
> assign opt_list here, too.
> 
Yup. Will do.
>> +		break;
>>   	default:
>>   		break;
>>   	}
>> @@ -518,13 +526,19 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>>   {
>>   	int i;
>>   
>> -	if (func == KEY_CHECK) {
>> -		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
>> -			ima_match_rule_data(rule, func_data, cred);
>> -	}
>>   	if ((rule->flags & IMA_FUNC) &&
>>   	    (rule->func != func && func != POST_SETATTR))
>>   		return false;
>> +
>> +	switch (func) {
>> +	case KEY_CHECK:
>> +	case CRITICAL_DATA:
>> +		return ((rule->func == func) &&
>> +			ima_match_rule_data(rule, func_data, cred));
>> +	default:
>> +		break;
>> +	}
>> +
>>   	if ((rule->flags & IMA_MASK) &&
>>   	    (rule->mask != mask && func != POST_SETATTR))
>>   		return false;
>> @@ -1119,6 +1133,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
>>   		if (ima_rule_contains_lsm_cond(entry))
>>   			return false;
>>   
>> +		break;
>> +	case CRITICAL_DATA:
>> +		if (entry->action & ~(MEASURE | DONT_MEASURE))
>> +			return false;
>> +
>> +		if (!(entry->flags & IMA_DATA_SOURCE) ||
>> +		    (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
>> +		    IMA_DATA_SOURCE)))
> 
> IMA_DATA_SOURCE shouldn't exist in this patch. This isn't the right
> indentation, either. See how IMA_KEYRINGS is indented in the KEY_CHECK
> case above.
> 
Will do.
~Tushar
> Tyler
> 
>> +			return false;
>> +
>> +		if (ima_rule_contains_lsm_cond(entry))
>> +			return false;
>> +
>>   		break;
>>   	default:
>>   		return false;
>> -- 
>> 2.17.1
>>

Re: [PATCH v7 5/8] IMA: limit critical data measurement based on a label

[Tushar Sugandhi]

On 2020-12-10 3:15 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:09, Tushar Sugandhi wrote:
>> System administrators should be able to limit which kernel subsystems
>> they want to measure the critical data for. To enable that, an IMA policy
>> condition to choose specific kernel subsystems is needed. This policy
>> condition would constrain the measurement of the critical data based on
>> a label for the given subsystems.
>>
>> Add a new IMA policy condition - "data_source:=" to the IMA func
>> CRITICAL_DATA to allow measurement of various kernel subsystems. This
>> policy condition would enable the system administrators to restrict the
>> measurement to the labels listed in "data_source:=".
>>
>> Limit the measurement to the labels that are specified in the IMA
>> policy - CRITICAL_DATA+"data_source:=". If "data_sources:=" is not
>> provided with the func CRITICAL_DATA, the data from all the
>> supported kernel subsystems is measured.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> 
> This patch will look good once all the IMA_DATA_SOURCE stuff is moved
> over from patch #4.
> 
> Tyler
> 
Sounds good. Will do.
~Tushar

>> ---
>>   Documentation/ABI/testing/ima_policy |  2 ++
>>   security/integrity/ima/ima_policy.c  | 26 +++++++++++++++++++++++++-
>>   2 files changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
>> index 6ec7daa87cba..0f4ee9e0a455 100644
>> --- a/Documentation/ABI/testing/ima_policy
>> +++ b/Documentation/ABI/testing/ima_policy
>> @@ -52,6 +52,8 @@ Description:
>>   			template:= name of a defined IMA template type
>>   			(eg, ima-ng). Only valid when action is "measure".
>>   			pcr:= decimal value
>> +			data_source:= [label]
>> +			label:= a unique string used for grouping and limiting critical data.
>>   
>>   		  default policy:
>>   			# PROC_SUPER_MAGIC
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 9a8ee80a3128..7486d09a3f60 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -934,7 +934,7 @@ enum {
>>   	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
>>   	Opt_appraise_type, Opt_appraise_flag,
>>   	Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
>> -	Opt_err
>> +	Opt_data_source, Opt_err
>>   };
>>   
>>   static const match_table_t policy_tokens = {
>> @@ -971,6 +971,7 @@ static const match_table_t policy_tokens = {
>>   	{Opt_pcr, "pcr=%s"},
>>   	{Opt_template, "template=%s"},
>>   	{Opt_keyrings, "keyrings=%s"},
>> +	{Opt_data_source, "data_source=%s"},
>>   	{Opt_err, NULL}
>>   };
>>   
>> @@ -1350,6 +1351,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>>   
>>   			entry->flags |= IMA_KEYRINGS;
>>   			break;
>> +		case Opt_data_source:
>> +			ima_log_string(ab, "data_source", args[0].from);
>> +
>> +			if (entry->data_source) {
>> +				result = -EINVAL;
>> +				break;
>> +			}
>> +
>> +			entry->data_source = ima_alloc_rule_opt_list(args);
>> +			if (IS_ERR(entry->data_source)) {
>> +				result = PTR_ERR(entry->data_source);
>> +				entry->data_source = NULL;
>> +				break;
>> +			}
>> +
>> +			entry->flags |= IMA_DATA_SOURCE;
>> +			break;
>>   		case Opt_fsuuid:
>>   			ima_log_string(ab, "fsuuid", args[0].from);
>>   
>> @@ -1730,6 +1748,12 @@ int ima_policy_show(struct seq_file *m, void *v)
>>   		seq_puts(m, " ");
>>   	}
>>   
>> +	if (entry->flags & IMA_DATA_SOURCE) {
>> +		seq_puts(m, "data_source=");
>> +		ima_show_rule_opt_list(m, entry->data_source);
>> +		seq_puts(m, " ");
>> +	}
>> +
>>   	if (entry->flags & IMA_PCR) {
>>   		snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
>>   		seq_printf(m, pt(Opt_pcr), tbuf);
>> -- 
>> 2.17.1
>>

Re: [PATCH v7 8/8] selinux: include a consumer of the new IMA critical data hook

[Tyler Hicks]

On 2020-12-09 11:42:12, Tushar Sugandhi wrote:
> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> 
> IMA measures files and buffer data such as keys, command line arguments
> passed to the kernel on kexec system call, etc. While these measurements
> enable monitoring and validating the integrity of the system, it is not
> sufficient. Various data structures, policies and states stored in kernel
> memory also impact the integrity of the system. Updates to these data
> structures would have an impact on the security functionalities.

This is repetitive when looking at the entire series. I think it can be
dropped.

> For example, SELinux stores the active policy in memory. Changes to this

Start here and drop the "For example, ":

 SELinux stores the active policy in memory and changes to this data ...

> data at runtime would have an impact on the security guarantees provided
> by SELinux. Measuring such in-memory data structures through IMA
> subsystem provides a secure way for a remote attestation service to
> know the state of the system and also the runtime changes in the state
> of the system.
> 
> SELinux policy is a critical data for this security module that needs

 SELinux policy is critical data and should be measured. This measurement ...

> to be measured. This measurement can be used by an attestation service,
> for instance, to verify if the policy has been setup correctly and that
> it hasn't been tampered at run-time.
> 
> Measure the hash of the loaded policy by calling the IMA hook
> ima_measure_critical_data(). Since the size of the loaded policy can
> be large (several MB), measure the hash of the policy instead of
> the entire policy to avoid bloating the IMA log entry.
> 
> Add "selinux" to the list of supported data sources maintained by IMA
> to enable measuring SELinux data.
> 
> To enable SELinux data measurement, the following steps are required:
> 
> 1, Add "ima_policy=critical_data" to the kernel command line arguments
>    to enable measuring SELinux data at boot time.
> For example,
>   BOOT_IMAGE=/boot/vmlinuz-5.10.0-rc1+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset security=selinux ima_policy=critical_data
> 
> 2, Add the following rule to /etc/ima/ima-policy
>    measure func=CRITICAL_DATA data_source=selinux
> 
> Sample measurement of the hash of SELinux policy:
> 
> To verify the measured data with the current SELinux policy run
> the following commands and verify the output hash values match.
> 
>   sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1
> 
>   grep "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | tail -1 | cut -d' ' -f 6
> 
> Note that the actual verification of SELinux policy would require loading
> the expected policy into an identical kernel on a pristine/known-safe
> system and run the sha256sum /sys/kernel/selinux/policy there to get
> the expected hash.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
> ---
>  Documentation/ABI/testing/ima_policy |  3 +-
>  security/selinux/Makefile            |  2 +
>  security/selinux/include/security.h  | 11 +++-
>  security/selinux/measure.c           | 86 ++++++++++++++++++++++++++++
>  security/selinux/ss/services.c       | 71 ++++++++++++++++++++---
>  5 files changed, 162 insertions(+), 11 deletions(-)
>  create mode 100644 security/selinux/measure.c
> 
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index 0f4ee9e0a455..7c7023f7986b 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -52,8 +52,9 @@ Description:
>  			template:= name of a defined IMA template type
>  			(eg, ima-ng). Only valid when action is "measure".
>  			pcr:= decimal value
> -			data_source:= [label]
> +			data_source:= [selinux]|[label]
>  			label:= a unique string used for grouping and limiting critical data.
> +			For example, "selinux" to measure critical data for SELinux.
>  
>  		  default policy:
>  			# PROC_SUPER_MAGIC
> diff --git a/security/selinux/Makefile b/security/selinux/Makefile
> index 4d8e0e8adf0b..83d512116341 100644
> --- a/security/selinux/Makefile
> +++ b/security/selinux/Makefile
> @@ -16,6 +16,8 @@ selinux-$(CONFIG_NETLABEL) += netlabel.o
>  
>  selinux-$(CONFIG_SECURITY_INFINIBAND) += ibpkey.o
>  
> +selinux-$(CONFIG_IMA) += measure.o
> +
>  ccflags-y := -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include
>  
>  $(addprefix $(obj)/,$(selinux-y)): $(obj)/flask.h
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index 3cc8bab31ea8..18ee65c98446 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -229,7 +229,8 @@ void selinux_policy_cancel(struct selinux_state *state,
>  			struct selinux_policy *policy);
>  int security_read_policy(struct selinux_state *state,
>  			 void **data, size_t *len);
> -
> +int security_read_policy_kernel(struct selinux_state *state,
> +				void **data, size_t *len);
>  int security_policycap_supported(struct selinux_state *state,
>  				 unsigned int req_cap);
>  
> @@ -446,4 +447,12 @@ extern void ebitmap_cache_init(void);
>  extern void hashtab_cache_init(void);
>  extern int security_sidtab_hash_stats(struct selinux_state *state, char *page);
>  
> +#ifdef CONFIG_IMA
> +extern void selinux_measure_state(struct selinux_state *selinux_state);
> +#else
> +static inline void selinux_measure_state(struct selinux_state *selinux_state)
> +{
> +}
> +#endif
> +
>  #endif /* _SELINUX_SECURITY_H_ */
> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> new file mode 100644
> index 000000000000..c409ada6ea39
> --- /dev/null
> +++ b/security/selinux/measure.c
> @@ -0,0 +1,86 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Measure SELinux state using IMA subsystem.
> + */
> +#include <linux/vmalloc.h>
> +#include <linux/ktime.h>
> +#include <linux/ima.h>
> +#include "security.h"
> +
> +/*
> + * This function creates a unique name by appending the timestamp to
> + * the given string. This string is passed as "event_name" to the IMA
> + * hook to measure the given SELinux data.
> + *
> + * The data provided by SELinux to the IMA subsystem for measuring may have
> + * already been measured (for instance the same state existed earlier).
> + * But for SELinux the current data represents a state change and hence
> + * needs to be measured again. To enable this, pass a unique "event_name"
> + * to the IMA hook so that IMA subsystem will always measure the given data.
> + *
> + * For example,
> + * At time T0 SELinux data to be measured is "foo". IMA measures it.
> + * At time T1 the data is changed to "bar". IMA measures it.
> + * At time T2 the data is changed to "foo" again. IMA will not measure it
> + * (since it was already measured) unless the event_name, for instance,
> + * is different in this call.
> + */
> +static char *selinux_event_name(const char *name_prefix)
> +{
> +	char *event_name = NULL;
> +	struct timespec64 cur_time;
> +
> +	ktime_get_real_ts64(&cur_time);
> +	event_name = kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix,
> +			       cur_time.tv_sec, cur_time.tv_nsec);
> +	if (!event_name) {
> +		pr_err("%s: event name not allocated.\n", __func__);
> +		return NULL;
> +	}
> +
> +	return event_name;
> +}
> +
> +/*
> + * selinux_measure_state - Measure hash of the SELinux policy
> + *
> + * @state: selinux state struct
> + *
> + * NOTE: This function must be called with policy_mutex held.
> + */
> +void selinux_measure_state(struct selinux_state *state)
> +{
> +	void *policy = NULL;
> +	char *policy_event_name = NULL;
> +	size_t policy_len;
> +	int rc = 0;
> +	bool initialized = selinux_initialized(state);
> +
> +	/*
> +	 * Measure SELinux policy only after initialization is completed.
> +	 */
> +	if (!initialized)
> +		goto out;
> +
> +	policy_event_name = selinux_event_name("selinux-policy-hash");
> +	if (!policy_event_name) {
> +		pr_err("%s: Event name for policy not allocated.\n",
> +		       __func__);

If the kasprintf() in selinux_event_name() fails, we'll get two similar
error messages saying that the event name could not be allocated. One of
these error messages can be removed.

> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	rc = security_read_policy_kernel(state, &policy, &policy_len);
> +	if (rc) {
> +		pr_err("%s: Failed to read policy %d.\n", __func__, rc);

The calls to pr_err() in this aren't quite following the style of the
other error SELinux error messages.

 $ git grep pr_err security/selinux
 security/selinux/hooks.c:               pr_err("SELinux:  out of range capability %d\n", cap);
 security/selinux/hooks.c:               pr_err("SELinux:  unable to map context to SID"
 security/selinux/netlink.c:     pr_err("SELinux:  OOM in %s\n", __func__);
 security/selinux/selinuxfs.c:   pr_err("SELinux:  Runtime disable is deprecated, use selinux=0 on the kernel cmdline.\n");
 security/selinux/selinuxfs.c:           pr_err("SELinux: failed to load policy booleans\n");
 security/selinux/selinuxfs.c:           pr_err("SELinux: failed to load policy classes\n");
 ...
 security/selinux/ss/services.c:         pr_err("SELinux: %s:  unrecognized SID %d\n",
 security/selinux/ss/services.c:         pr_err("SELinux: %s:  unrecognized SID %d\n",
 security/selinux/ss/services.c:         pr_err("SELinux: %s:  unrecognized SID %d\n",
 security/selinux/ss/services.c:         pr_err("SELinux: %s:  unrecognized SID %d\n",
 security/selinux/ss/services.c:         pr_err("SELinux: %s:  unrecognized class %s\n",

Prepending your error message strings with "SELinux: " and lowercasing the
first character after "%s: " ought to do it.


All the other code changes in this patch look correct to me.

Tyler


> +		goto out;
> +	}
> +
> +	ima_measure_critical_data("selinux", policy_event_name,
> +				  policy, policy_len, true);
> +
> +	vfree(policy);
> +
> +out:
> +	kfree(policy_event_name);
> +}
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 9704c8a32303..dfa2e00894ae 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -2180,6 +2180,7 @@ static void selinux_notify_policy_change(struct selinux_state *state,
>  	selinux_status_update_policyload(state, seqno);
>  	selinux_netlbl_cache_invalidate();
>  	selinux_xfrm_notify_policyload();
> +	selinux_measure_state(state);
>  }
>  
>  void selinux_policy_commit(struct selinux_state *state,
> @@ -3875,8 +3876,33 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state,
>  }
>  #endif /* CONFIG_NETLABEL */
>  
> +/**
> + * security_read_selinux_policy - read the policy.
> + * @policy: SELinux policy
> + * @data: binary policy data
> + * @len: length of data in bytes
> + *
> + */
> +static int security_read_selinux_policy(struct selinux_policy *policy,
> +					void *data, size_t *len)
> +{
> +	int rc;
> +	struct policy_file fp;
> +
> +	fp.data = data;
> +	fp.len = *len;
> +
> +	rc = policydb_write(&policy->policydb, &fp);
> +	if (rc)
> +		return rc;
> +
> +	*len = (unsigned long)fp.data - (unsigned long)data;
> +	return 0;
> +}
> +
>  /**
>   * security_read_policy - read the policy.
> + * @state: selinux_state
>   * @data: binary policy data
>   * @len: length of data in bytes
>   *
> @@ -3885,8 +3911,6 @@ int security_read_policy(struct selinux_state *state,
>  			 void **data, size_t *len)
>  {
>  	struct selinux_policy *policy;
> -	int rc;
> -	struct policy_file fp;
>  
>  	policy = rcu_dereference_protected(
>  			state->policy, lockdep_is_held(&state->policy_mutex));
> @@ -3898,14 +3922,43 @@ int security_read_policy(struct selinux_state *state,
>  	if (!*data)
>  		return -ENOMEM;
>  
> -	fp.data = *data;
> -	fp.len = *len;
> +	return security_read_selinux_policy(policy, *data, len);
> +}
>  
> -	rc = policydb_write(&policy->policydb, &fp);
> -	if (rc)
> -		return rc;
> +/**
> + * security_read_policy_kernel - read the policy.
> + * @state: selinux_state
> + * @data: binary policy data
> + * @len: length of data in bytes
> + *
> + * Allocates kernel memory for reading SELinux policy.
> + * This function is for internal use only and should not
> + * be used for returning data to user space.
> + *
> + * This function must be called with policy_mutex held.
> + */
> +int security_read_policy_kernel(struct selinux_state *state,
> +				void **data, size_t *len)
> +{
> +	struct selinux_policy *policy;
> +	int rc = 0;
>  
> -	*len = (unsigned long)fp.data - (unsigned long)*data;
> -	return 0;
> +	policy = rcu_dereference_protected(
> +			state->policy, lockdep_is_held(&state->policy_mutex));
> +	if (!policy) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
> +
> +	*len = policy->policydb.len;
> +	*data = vmalloc(*len);
> +	if (!*data) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
>  
> +	rc = security_read_selinux_policy(policy, *data, len);
> +
> +out:
> +	return rc;
>  }
> -- 
> 2.17.1
> 

Re: [PATCH v7 8/8] selinux: include a consumer of the new IMA critical data hook

[Tyler Hicks]

On 2020-12-11 09:36:30, Tyler Hicks wrote:
> The calls to pr_err() in this aren't quite following the style of the
> other error SELinux error messages.

Sorry, I left out a word. I meant to say that the calls to pr_err() in
this *file* aren't quite following the right style. Please adjust all of
them.

Thanks!

Tyler

Re: [PATCH v7 8/8] selinux: include a consumer of the new IMA critical data hook

[Lakshmi Ramasubramanian]

On 12/11/20 7:41 AM, Tyler Hicks wrote:
> On 2020-12-11 09:36:30, Tyler Hicks wrote:
>> The calls to pr_err() in this aren't quite following the style of the
>> other error SELinux error messages.
> 
> Sorry, I left out a word. I meant to say that the calls to pr_err() in
> this *file* aren't quite following the right style. Please adjust all of
> them.
> 
> Thanks!
> 

Thanks for reviewing the patch Tyler. I'll make the changes per your 
comments.

  -lakshmi

Re: [PATCH v7 3/8] IMA: define a hook to measure kernel integrity critical data

[Tushar Sugandhi]

<snip>

>> + */
>> +void ima_measure_critical_data(const char *event_name,
>> +			       const void *buf, int buf_len,
>> +			       bool measure_buf_hash)
>> +{
>> +	if (!event_name || !buf || !buf_len) {
>> +		pr_err("Invalid arguments passed to %s().\n", __func__);
> 
> This is a problem for the developer making use of the
> ima_measure_critical_data() API and shouldn't be logged, IMO, because a
> user/admin can do nothing about it. I think the error message should be
> dropped.
> 
Thanks Tyler.
Will drop the message.