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 v9: Incorporated feedback from Tyler on v8 of this series. - Moved rule->data_source logic from Patch #4 to Patch #5. - Removed unnecessary variable event_name from selinux_event_name() in Patch #8. Change Log v8: Incorporated feedback from Tyler on v7 of this series. - Removed unnecessary 'else' clauses in ima_match_rule_data(). - Fixed ima_store_template() to pass the buffer hash in case the buffer is large. - fixed function description for ima_measure_critical_data(). - Moved some usage of CRITICAL_DATA from Patch #3 to Patch #4. - Moved IMA_DATA_SOURCE from Patch #4 to Patch #5. - Removed unnecessary pr_err() from ima_measure_critical_data() and selinux_event_name(). - Fixed log formatting in selinux_measure_state() to be consistent with other messages in that file. 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 | 118 ++++++++++++++---- security/integrity/ima/ima_queue_keys.c | 3 +- security/selinux/Makefile | 2 + security/selinux/include/security.h | 11 +- security/selinux/measure.c | 79 ++++++++++++ security/selinux/ss/services.c | 71 +++++++++-- 14 files changed, 352 insertions(+), 51 deletions(-) create mode 100644 security/selinux/measure.c -- 2.17.1
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> 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 | 46 ++++++++++++++++++----------- 4 files changed, 37 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..a09d1a41a290 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -453,30 +453,41 @@ 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; + + opt_list = rule->keyrings; + break; + default: + return false; + } - if (!keyring) + if (!func_data) 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 +504,20 @@ 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 +621,7 @@ 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 +633,7 @@ 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 +648,7 @@ 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
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> Reviewed-by: Tyler Hicks <tyhicks@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 | 38 +++++++++++++++++--- security/integrity/ima/ima_queue_keys.c | 3 +- 5 files changed, 39 insertions(+), 9 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..0f8409d77602 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; @@ -849,13 +862,27 @@ 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"; goto out; } - ret = ima_store_template(entry, violation, NULL, buf, pcr); + ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); if (ret < 0) { audit_cause = "store_entry"; ima_free_template_entry(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
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> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> --- include/linux/ima.h | 6 ++++++ security/integrity/ima/ima.h | 1 + security/integrity/ima/ima_api.c | 2 +- security/integrity/ima/ima_main.c | 34 +++++++++++++++++++++++++++++++ 4 files changed, 42 insertions(+), 1 deletion(-) 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 0f8409d77602..dff4bce4fb09 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -922,6 +922,40 @@ 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 various data structures, + * policies, and states stored in kernel memory that can impact the integrity + * of the system. + * + * 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) + 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; -- 2.17.1
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> --- Documentation/ABI/testing/ima_policy | 2 +- security/integrity/ima/ima_policy.c | 29 ++++++++++++++++++++++++---- 2 files changed, 26 insertions(+), 5 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/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index a09d1a41a290..d45c2dbb6d45 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -479,6 +479,8 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule, opt_list = rule->keyrings; break; + case CRITICAL_DATA: + return true; default: return false; } @@ -515,13 +517,19 @@ 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; @@ -1116,6 +1124,17 @@ 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_FUNC | IMA_UID | IMA_PCR)) + return false; + + if (ima_rule_contains_lsm_cond(entry)) + return false; + break; default: return false; @@ -1248,6 +1267,8 @@ 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
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 | 37 +++++++++++++++++++++++++--- 2 files changed, 36 insertions(+), 3 deletions(-) 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 d45c2dbb6d45..fea996a9e26c 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; }; @@ -480,7 +482,11 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule, opt_list = rule->keyrings; break; case CRITICAL_DATA: - return true; + if (!rule->data_source) + return true; + + opt_list = rule->data_source; + break; default: return false; } @@ -925,7 +931,7 @@ 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 = { @@ -962,6 +968,7 @@ 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} }; @@ -1129,7 +1136,8 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) if (entry->action & ~(MEASURE | DONT_MEASURE)) return false; - if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR)) + if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR | + IMA_DATA_SOURCE)) return false; if (ima_rule_contains_lsm_cond(entry)) @@ -1339,6 +1347,23 @@ 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); @@ -1719,6 +1744,12 @@ 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
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> --- 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 dff4bce4fb09..cc828ba00790 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 various data structures, * policies, and states stored in kernel memory that can impact the integrity @@ -944,15 +948,16 @@ 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) 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
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> --- 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 fea996a9e26c..376b625acc72 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 @@ -872,6 +879,11 @@ 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
From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> SELinux stores the active policy in memory, so the changes to this data at runtime would have an impact on the security guarantees provided by SELinux. Measuring in-memory SELinux policy through IMA subsystem provides a secure way for the attestation service to remotely validate the policy contents at runtime. 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> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> --- Documentation/ABI/testing/ima_policy | 3 +- security/selinux/Makefile | 2 + security/selinux/include/security.h | 11 +++- security/selinux/measure.c | 79 ++++++++++++++++++++++++++++ security/selinux/ss/services.c | 71 +++++++++++++++++++++---- 5 files changed, 155 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..b7e24358e11d --- /dev/null +++ b/security/selinux/measure.c @@ -0,0 +1,79 @@ +// 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) +{ + struct timespec64 cur_time; + + ktime_get_real_ts64(&cur_time); + return kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix, + cur_time.tv_sec, cur_time.tv_nsec); +} + +/* + * 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("SELinux: %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("SELinux: %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
On 2020-12-12 10:02:47, 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> This looks nice. Thanks for the changes! Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> Tyler > --- > Documentation/ABI/testing/ima_policy | 2 +- > security/integrity/ima/ima_policy.c | 29 ++++++++++++++++++++++++---- > 2 files changed, 26 insertions(+), 5 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/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c > index a09d1a41a290..d45c2dbb6d45 100644 > --- a/security/integrity/ima/ima_policy.c > +++ b/security/integrity/ima/ima_policy.c > @@ -479,6 +479,8 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule, > > opt_list = rule->keyrings; > break; > + case CRITICAL_DATA: > + return true; > default: > return false; > } > @@ -515,13 +517,19 @@ 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; > @@ -1116,6 +1124,17 @@ 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_FUNC | IMA_UID | IMA_PCR)) > + return false; > + > + if (ima_rule_contains_lsm_cond(entry)) > + return false; > + > break; > default: > return false; > @@ -1248,6 +1267,8 @@ 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 >
On 2020-12-12 10:02:48, 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> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> Tyler > --- > Documentation/ABI/testing/ima_policy | 2 ++ > security/integrity/ima/ima_policy.c | 37 +++++++++++++++++++++++++--- > 2 files changed, 36 insertions(+), 3 deletions(-) > > 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 d45c2dbb6d45..fea996a9e26c 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; > }; > > @@ -480,7 +482,11 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule, > opt_list = rule->keyrings; > break; > case CRITICAL_DATA: > - return true; > + if (!rule->data_source) > + return true; > + > + opt_list = rule->data_source; > + break; > default: > return false; > } > @@ -925,7 +931,7 @@ 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 = { > @@ -962,6 +968,7 @@ 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} > }; > > @@ -1129,7 +1136,8 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) > if (entry->action & ~(MEASURE | DONT_MEASURE)) > return false; > > - if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR)) > + if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR | > + IMA_DATA_SOURCE)) > return false; > > if (ima_rule_contains_lsm_cond(entry)) > @@ -1339,6 +1347,23 @@ 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); > > @@ -1719,6 +1744,12 @@ 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 >
On 2020-12-12 11:20 a.m., Tyler Hicks wrote:
> On 2020-12-12 10:02:47, 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>
>
> This looks nice. Thanks for the changes!
>
> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
>
> Tyler
>
Thanks for the detailed review on this series Tyler.
We really appreciate it.
~Tushar
On 2020-12-12 11:20 a.m., Tyler Hicks wrote:
> On 2020-12-12 10:02:48, 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>
>
> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
>
> Tyler
>
Thanks again Tyler.
~Tushar
On Sat, Dec 12, 2020 at 1:03 PM Tushar Sugandhi <tusharsu@linux.microsoft.com> wrote: > From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> > > SELinux stores the active policy in memory, so the changes to this data > at runtime would have an impact on the security guarantees provided > by SELinux. Measuring in-memory SELinux policy through IMA subsystem > provides a secure way for the attestation service to remotely validate > the policy contents at runtime. > > 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> > Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> > --- > Documentation/ABI/testing/ima_policy | 3 +- > security/selinux/Makefile | 2 + > security/selinux/include/security.h | 11 +++- > security/selinux/measure.c | 79 ++++++++++++++++++++++++++++ > security/selinux/ss/services.c | 71 +++++++++++++++++++++---- > 5 files changed, 155 insertions(+), 11 deletions(-) > create mode 100644 security/selinux/measure.c ... > 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 Naming things is hard, I get that, but I would prefer if we just called this file "ima.c" or something similar. The name "measure.c" implies a level of abstraction or general use which simply doesn't exist here. Let's help make it a bit more obvious what should belong in this file. > 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 If you are going to put the SELinux/IMA function(s) into a separate source file, please put the function declarations into a separate header file too. For example, look at security/selinux/include/{netif,netnode,netport,etc.}.h. > diff --git a/security/selinux/measure.c b/security/selinux/measure.c > new file mode 100644 > index 000000000000..b7e24358e11d > --- /dev/null > +++ b/security/selinux/measure.c > @@ -0,0 +1,79 @@ > +// 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) > +{ > + struct timespec64 cur_time; > + > + ktime_get_real_ts64(&cur_time); > + return kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix, > + cur_time.tv_sec, cur_time.tv_nsec); > +} Why is this a separate function? It's three lines long and only called from selinux_measure_state(). Do you ever see the SELinux/IMA code in this file expanding to the point where this function is nice from a reuse standpoint? Also, I assume you are not concerned about someone circumventing the IMA measurements by manipulating the time? In most systems I would expect the time to be a protected entity, but with many systems getting their time from remote systems I thought it was worth mentioning. > +/* > + * 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) Similar to the name of this source file, let's make it clear this is for IMA. How about calling this selinux_ima_measure_state() or similar? > +{ > + void *policy = NULL; > + char *policy_event_name = NULL; > + size_t policy_len; > + int rc = 0; > + bool initialized = selinux_initialized(state); Why bother with the initialized variable? Unless I'm missing something it is only used once in the code below. > + /* > + * 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("SELinux: %s: event name for policy not allocated.\n", > + __func__); > + rc = -ENOMEM; This function doesn't return an error code, why bother with setting the rc variable here? > + goto out; > + } > + > + rc = security_read_policy_kernel(state, &policy, &policy_len); > + if (rc) { > + pr_err("SELinux: %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) Let's just call this "security_read_policy()". > +{ > + 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)> -- > 2.17.1 > > 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) Let's call this "security_read_state_kernel()". > +{ > + struct selinux_policy *policy; > + int rc = 0; See below, the rc variable is not needed. > - *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; Jumping to the out label is a little silly since it is just a return; do a "return -EINVAL;" here instead. > + } > + > + *len = policy->policydb.len; > + *data = vmalloc(*len); > + if (!*data) { > + rc = -ENOMEM; > + goto out; Same as above, "return -ENOMEM;" please. > + } > > + rc = security_read_selinux_policy(policy, *data, len); You should be able to do "return security_read_selinux_policy(...);" here. > + > +out: > + return rc; > } -- paul moore www.paul-moore.com
On Sat, 2020-12-12 at 10:02 -0800, 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. By definition, buffer data is only measured. Nothing new is added by the above paragraph. Please remove 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. Like the patch Subject line use "the buffer data hash" instead of the "hash of a buffer". There's no need to include the boolean parameter name "measure_buf_hash". Please remove it. > > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> > Reviewed-by: Tyler Hicks <tyhicks@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 | 38 +++++++++++++++++--- > security/integrity/ima/ima_queue_keys.c | 3 +- > 5 files changed, 39 insertions(+), 9 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); Please abbreviate the boolean name to "hash". The test would then be "if (hash == true)" or "if (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..0f8409d77602 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 ^@hash: measure buffer data hash > * > - * Based on policy, the buffer is measured into the ima log. > + * Measure the buffer into the IMA log, and extend the @pcr. IMA always measures/appraises files and measures buffer data based on policy. The above sentence succintly summarizes what process_buffer_measurement() does. This patch adds support for measuring the "buffer data hash". The following would be an appropriate change. * Based on policy, either the buffer data or buffer data hash is measured > + * > + * 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. This patch should be limited to adding "buffer data hash" support. These changes don't belong in this patch. Please remove. > */ > 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; > @@ -849,13 +862,27 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size, > goto out; > } > > + if (measure_buf_hash) { ^ if (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"; I don't see a good no reason for defining a new audit cause. Use the existing "hashing_error". thanks, Mimi > + 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"; > goto out; > } > > - ret = ima_store_template(entry, violation, NULL, buf, pcr); > + ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); > if (ret < 0) { > audit_cause = "store_entry"; > ima_free_template_entry(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); > }
On Sat, 2020-12-12 at 10:02 -0800, Tushar Sugandhi wrote: > IMA provides capabilities to measure file data, and in-memory buffer No need for the comma here. Up to this patch set, all the patches refer to "buffer data", not "in- memory buffer data". This patch introduces the concept of measuring "in-memory buffer data". Please remove "in-memory" above. > data. However, various data structures, policies, and states Here and everywhere else, there are two blanks after a period. > 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, ^integrity of the system. > IMA does not provide a generic function for kernel subsystems to measure > their integrity critical data. The emphasis should not be on "kernel subsystems". Simplify to "for measuring kernel integrity critical data". > > Define a new IMA hook - ima_measure_critical_data to measure kernel > integrity critical data. Either "ima_measure_critical_data" is between hyphens or without any hyphens. If not hyphenated, then you could say "named ima_measure_critical_data", but "named" isn't necessary. Or reverse "a new IMA hook" and "ima_measure_critical_data", adding comma's like: Define ima_measure_critical_data, a new IMA hook, to ... Any of the above options work, just not a single hyphen. > > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> > Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> > --- <snip> > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index 0f8409d77602..dff4bce4fb09 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -922,6 +922,40 @@ 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 Why future tense? By "buffer entry" do you mean a record in the IMA measurement list? > + * @buf: pointer to buffer containing data to measure ^pointer to buffer data > + * @buf_len: length of buffer(in bytes) ^length of buffer data (in bytes) > + * @measure_buf_hash: measure buffer hash As requested in 2/8, please abbreviate the boolean name to "hash". Refer to section "4) Naming" in Documentation/process/coding-style.rst for variable naming conventions. ^@hash: measure buffer data 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 various data structures, > + * policies, and states stored in kernel memory that can impact the integrity > + * of the system. > + * > + * 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. The "/**" is the start of kernel-doc. Have you seen anywhere else in the kernel using the @<variable name> in the longer function description? Have you seen this style of longer function description? Refer to Documentation/doc-guide/kernel-doc.rst and other code for examples. > + */ > +void ima_measure_critical_data(const char *event_name, > + const void *buf, int buf_len, As "buf_len" should always be >= 0, it should not be defined as a signed variable. > + bool measure_buf_hash) > +{ > + if (!event_name || !buf || !buf_len) > + return; > + > + process_buffer_measurement(NULL, buf, buf_len, event_name, > + CRITICAL_DATA, 0, NULL, > + measure_buf_hash); ^hash thanks, Mimi > +} > + > static int __init init_ima(void) > { > int error;
On Sat, 2020-12-12 at 10:02 -0800, Tushar Sugandhi wrote: > > 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. This can be simplified to "func specific data, may be NULL". Please update in all places. > * > * 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..a09d1a41a290 100644 > --- a/security/integrity/ima/ima_policy.c > +++ b/security/integrity/ima/ima_policy.c > @@ -453,30 +453,41 @@ 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 After the function_name is a brief description of the function, which should not span multiple lines. Refer to Documentation/doc- guide/kernel-doc.rst for details. Please trim the function description to: determine whether func_data matches the policy rule > + * @rule: IMA policy rule This patch should be limited to renaming "keyring" to "func_data". It shouldn't make other changes, even simple ones like this. > + * @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; > + > + opt_list = rule->keyrings; > + break; > + default: > + return false; > + } > > - if (!keyring) > + if (!func_data) > 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 +504,20 @@ 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. Update as previously suggested. > * > * 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 +621,7 @@ 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. And again here. thanks, Mimi
Hi Tushar,
Please update the Subject line as, "Add policy rule support for
measuring critical data".
On Sat, 2020-12-12 at 10:02 -0800, 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>
This patch does not restrict measuring critical data, but adds policy
rule support for measuring critical data. please update the patch
description accordingly.
Other than that,
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Hi Tushar, On Sat, 2020-12-12 at 10:02 -0800, 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. Restricting which kernel integrity critical data is measured is not only of interest to system administrators. Why single them out? Limiting which critical data is measured is based on a label, making it flexible. In your use case scenario, you're grouping the label based on kernel subsystem, but is that really necessary? In the broader picture, there could be cross subsystem critical data being measured based on a single label. Please think about the broader picture and re-write the patch descirption more generically. > > Add a new IMA policy condition - "data_source:=" to the IMA func What is with "add"? You're "adding support for" or "defining" a new policy condition. Remove the single hyphen, as explained in 3/8. Please replace "data_source" with something more generic (e.g. label). thanks, Mimi > 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>
On Sat, 2020-12-12 at 10:02 -0800, 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". This sentence isn't really necessary. > > 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> Otherwise, Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> thanks, Mimi
On 12/23/20 1:10 PM, Paul Moore wrote: Hi Paul, > ... > >> 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 > > Naming things is hard, I get that, but I would prefer if we just > called this file "ima.c" or something similar. The name "measure.c" > implies a level of abstraction or general use which simply doesn't > exist here. Let's help make it a bit more obvious what should belong > in this file. Agreed - I will rename the file to ima.c > >> 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 > > If you are going to put the SELinux/IMA function(s) into a separate > source file, please put the function declarations into a separate > header file too. For example, look at > security/selinux/include/{netif,netnode,netport,etc.}.h. I will create a new header file "security/selinux/include/ima.h" and move the function declarations for IMA functions to that header. > >> diff --git a/security/selinux/measure.c b/security/selinux/measure.c >> new file mode 100644 >> index 000000000000..b7e24358e11d >> --- /dev/null >> +++ b/security/selinux/measure.c >> @@ -0,0 +1,79 @@ >> +// 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) >> +{ >> + struct timespec64 cur_time; >> + >> + ktime_get_real_ts64(&cur_time); >> + return kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix, >> + cur_time.tv_sec, cur_time.tv_nsec); >> +} > > Why is this a separate function? It's three lines long and only > called from selinux_measure_state(). Do you ever see the SELinux/IMA > code in this file expanding to the point where this function is nice > from a reuse standpoint? Earlier I had two measurements - one for SELinux configuration/state and another for SELinux policy. selinux_event_name() was used to generate event name for each of them. In this patch set I have included only one measurement - for SELinux policy. I plan to add "SELinux configuration/state" measurement in a separate patch - I can reuse selinux_event_name() in that patch. Also, I think the comment in the function header for selinux_event_name() is useful. I prefer to have a separate function, if that's fine by you. > > Also, I assume you are not concerned about someone circumventing the > IMA measurements by manipulating the time? In most systems I would > expect the time to be a protected entity, but with many systems > getting their time from remote systems I thought it was worth > mentioning. I am using time function to generate a unique name for the IMA measurement event, such as, "selinux-policy-hash-1609790281:860232824". This is to ensure that state changes in SELinux data are always measured. If you think time manipulation can be an issue, please let me know a better way to generate unique event names. > >> +/* >> + * 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) > > Similar to the name of this source file, let's make it clear this is > for IMA. How about calling this selinux_ima_measure_state() or > similar? Sure - I will change the function name to selinux_ima_measure_state(). > >> +{ >> + void *policy = NULL; >> + char *policy_event_name = NULL; >> + size_t policy_len; >> + int rc = 0; >> + bool initialized = selinux_initialized(state); > > Why bother with the initialized variable? Unless I'm missing > something it is only used once in the code below. You are right - I will remove "initialized" variable and directly get the state using selinux_initialized(). > >> + /* >> + * 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("SELinux: %s: event name for policy not allocated.\n", >> + __func__); >> + rc = -ENOMEM; > > This function doesn't return an error code, why bother with setting > the rc variable here? Yes - it is not necessary. I will remove the line. > >> + goto out; >> + } >> + >> + rc = security_read_policy_kernel(state, &policy, &policy_len); >> + if (rc) { >> + pr_err("SELinux: %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) > > Let's just call this "security_read_policy()". There is another function in this file with the name security_read_policy(). How about changing the above function name to "read_selinux_policy()" since this is a local/static function. > >> +{ >> + 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)> -- >> 2.17.1 >> > >> 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) > > Let's call this "security_read_state_kernel()". Sure - I will rename the function. > >> +{ >> + struct selinux_policy *policy; >> + int rc = 0; > > See below, the rc variable is not needed. > >> - *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; > > Jumping to the out label is a little silly since it is just a return; > do a "return -EINVAL;" here instead. > >> + } >> + >> + *len = policy->policydb.len; >> + *data = vmalloc(*len); >> + if (!*data) { >> + rc = -ENOMEM; >> + goto out; > > Same as above, "return -ENOMEM;" please. > >> + } >> >> + rc = security_read_selinux_policy(policy, *data, len); > > You should be able to do "return security_read_selinux_policy(...);" here. I will remove the local variable "rc" and make the three changes you've stated above. Thanks for reviewing the changes. -lakshmi > >> + >> +out: >> + return rc; >> } >
On Mon, Jan 4, 2021 at 6:30 PM Lakshmi Ramasubramanian <nramas@linux.microsoft.com> wrote: > On 12/23/20 1:10 PM, Paul Moore wrote: > Hi Paul, Hello. > >> diff --git a/security/selinux/measure.c b/security/selinux/measure.c > >> new file mode 100644 > >> index 000000000000..b7e24358e11d > >> --- /dev/null > >> +++ b/security/selinux/measure.c > >> @@ -0,0 +1,79 @@ > >> +// 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) > >> +{ > >> + struct timespec64 cur_time; > >> + > >> + ktime_get_real_ts64(&cur_time); > >> + return kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix, > >> + cur_time.tv_sec, cur_time.tv_nsec); > >> +} > > > > Why is this a separate function? It's three lines long and only > > called from selinux_measure_state(). Do you ever see the SELinux/IMA > > code in this file expanding to the point where this function is nice > > from a reuse standpoint? > > Earlier I had two measurements - one for SELinux configuration/state and > another for SELinux policy. selinux_event_name() was used to generate > event name for each of them. > > In this patch set I have included only one measurement - for SELinux > policy. I plan to add "SELinux configuration/state" measurement in a > separate patch - I can reuse selinux_event_name() in that patch. I'm curious about this second measurement. My apologies if you posted it previously, this patchset has gone through several iterations and simply can't recall all the different versions without digging through the list archives. Is there a reason why the second measurement isn't included in this patch? Or this patchset if it is too big to be a single patch? > Also, I think the comment in the function header for > selinux_event_name() is useful. > > I prefer to have a separate function, if that's fine by you. Given just this patch I would prefer if you folded selinux_event_name() into selinux_measure_state(). However, I agree with you that the comments in the selinux_event_name() header block is useful, I would suggest moving those into the body of selinux_measure_state() directly above the calls to ktime_get_real_ts64() and kasprintf(). > > Also, I assume you are not concerned about someone circumventing the > > IMA measurements by manipulating the time? In most systems I would > > expect the time to be a protected entity, but with many systems > > getting their time from remote systems I thought it was worth > > mentioning. > > I am using time function to generate a unique name for the IMA > measurement event, such as, "selinux-policy-hash-1609790281:860232824". > This is to ensure that state changes in SELinux data are always measured. > > If you think time manipulation can be an issue, please let me know a > better way to generate unique event names. Yes, I understand that you are using the time value as a way of ensuring you always have a different event name and hence a new measurement. However, I was wondering if you would be okay if the time was adjusted such that an event name was duplicated and a measurement missed? Is that a problem for you? It seems like it might be an issue, but you and Mimi know IMA better than I do. > >> 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 > >> @@ -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) > > > > Let's just call this "security_read_policy()". > There is another function in this file with the name security_read_policy(). > > How about changing the above function name to "read_selinux_policy()" > since this is a local/static function. Ooops, sorry about that! I'm not sure what I was thinking there :) How about "__security_read_policy()"? -- paul moore www.paul-moore.com
On 1/4/21 6:13 PM, Paul Moore wrote: > On Mon, Jan 4, 2021 at 6:30 PM Lakshmi Ramasubramanian > <nramas@linux.microsoft.com> wrote: >> On 12/23/20 1:10 PM, Paul Moore wrote: >> Hi Paul, > > Hello. > >>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c >>>> new file mode 100644 >>>> index 000000000000..b7e24358e11d >>>> --- /dev/null >>>> +++ b/security/selinux/measure.c >>>> @@ -0,0 +1,79 @@ >>>> +// 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) >>>> +{ >>>> + struct timespec64 cur_time; >>>> + >>>> + ktime_get_real_ts64(&cur_time); >>>> + return kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix, >>>> + cur_time.tv_sec, cur_time.tv_nsec); >>>> +} >>> >>> Why is this a separate function? It's three lines long and only >>> called from selinux_measure_state(). Do you ever see the SELinux/IMA >>> code in this file expanding to the point where this function is nice >>> from a reuse standpoint? >> >> Earlier I had two measurements - one for SELinux configuration/state and >> another for SELinux policy. selinux_event_name() was used to generate >> event name for each of them. >> >> In this patch set I have included only one measurement - for SELinux >> policy. I plan to add "SELinux configuration/state" measurement in a >> separate patch - I can reuse selinux_event_name() in that patch. > > I'm curious about this second measurement. My apologies if you posted > it previously, this patchset has gone through several iterations and > simply can't recall all the different versions without digging through > the list archives. > The 2nd measurement is for SELinux state data such as "enforcing", "checkreqprot", policycap[__POLICYDB_CAPABILITY_MAX], etc. > Is there a reason why the second measurement isn't included in this > patch? Or this patchset if it is too big to be a single patch? > For illustrating the use of the new IMA hook, that my colleague Tushar has added for measuring kernel critical data, we have included only one SELinux measurement in this patch set - the measurement of SELinux policy. This also helped in keeping this patch smaller. When this patch set is merged, I'll post a separate patch to add measurement of SELinux state data I have mentioned above. >> Also, I think the comment in the function header for >> selinux_event_name() is useful. >> >> I prefer to have a separate function, if that's fine by you. > > Given just this patch I would prefer if you folded > selinux_event_name() into selinux_measure_state(). However, I agree > with you that the comments in the selinux_event_name() header block is > useful, I would suggest moving those into the body of > selinux_measure_state() directly above the calls to > ktime_get_real_ts64() and kasprintf(). Sure - I will make that change. > >>> Also, I assume you are not concerned about someone circumventing the >>> IMA measurements by manipulating the time? In most systems I would >>> expect the time to be a protected entity, but with many systems >>> getting their time from remote systems I thought it was worth >>> mentioning. >> >> I am using time function to generate a unique name for the IMA >> measurement event, such as, "selinux-policy-hash-1609790281:860232824". >> This is to ensure that state changes in SELinux data are always measured. >> >> If you think time manipulation can be an issue, please let me know a >> better way to generate unique event names. > > Yes, I understand that you are using the time value as a way of > ensuring you always have a different event name and hence a new > measurement. However, I was wondering if you would be okay if the > time was adjusted such that an event name was duplicated and a > measurement missed? Is that a problem for you? It seems like it > might be an issue, but you and Mimi know IMA better than I do. If the system time was adjusted such that the event name is duplicated, we could miss measurements - this is not okay. For example: #1 Say, at time T1 SELinux state being measured is "foo" - IMA will measure it. #2 at time T2, the state changes to "bar" - IMA will measure it #3 at time T3, the state changes from "bar" to "foo" again. Unless the "event name" passed in the measurement call is different from what was passed in step #1, IMA will not measure it and hence we'll miss the state change. If system time can be manipulated to return the same "timer tick" on every call to ktime_get_real_ts64(), we will lose measurement in Step #3 above. But given that we are using ktime_get_real_ts64() to get the timer tick, is it possible to manipulate the system time without compromising the overall functioning of the rest of the system? If yes, then it is an issue - I mean, there is a possibility of losing some measurements. > >>>> 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 >>>> @@ -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) >>> >>> Let's just call this "security_read_policy()". >> There is another function in this file with the name security_read_policy(). >> >> How about changing the above function name to "read_selinux_policy()" >> since this is a local/static function. > > Ooops, sorry about that! I'm not sure what I was thinking there :) > > How about "__security_read_policy()"? > Sure - I will change the function name to "__security_read_policy()". thanks, -lakshmi
Hello Mimi, Sorry for the late response. I was on vacation last week. On 2020-12-24 5:06 a.m., Mimi Zohar wrote: > On Sat, 2020-12-12 at 10:02 -0800, Tushar Sugandhi wrote: >> >> 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. > > This can be simplified to "func specific data, may be NULL". Please > update in all places. > Ok, will do. >> * >> * 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..a09d1a41a290 100644 >> --- a/security/integrity/ima/ima_policy.c >> +++ b/security/integrity/ima/ima_policy.c >> @@ -453,30 +453,41 @@ 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 > > After the function_name is a brief description of the function, which > should not span multiple lines. Refer to Documentation/doc- > guide/kernel-doc.rst for details. > > Please trim the function description to: > determine whether func_data matches the policy rule > Thanks, will do. >> + * @rule: IMA policy rule > > This patch should be limited to renaming "keyring" to "func_data". It > shouldn't make other changes, even simple ones like this. > Agreed. I will revert the rule description to the old one. >> + * @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; >> + >> + opt_list = rule->keyrings; >> + break; >> + default: >> + return false; >> + } >> >> - if (!keyring) >> + if (!func_data) >> 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 +504,20 @@ 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. > > Update as previously suggested. > Yes. >> * >> * 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 +621,7 @@ 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. > > And again here. > Yes. > thanks, > > Mimi > Thanks, Tushar
On 2020-12-23 4:03 p.m., Mimi Zohar wrote: > On Sat, 2020-12-12 at 10:02 -0800, 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. > > By definition, buffer data is only measured. Nothing new is added by > the above paragraph. Please remove it. > Sure. Will remove. >> >> Introduce a boolean parameter measure_buf_hash to support measuring >> hash of a buffer, which would be much smaller, instead of the buffer >> itself. > > Like the patch Subject line use "the buffer data hash" instead of the > "hash of a buffer". > Will do. > There's no need to include the boolean parameter name > "measure_buf_hash". Please remove it. > Will do. >> >> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> >> Reviewed-by: Tyler Hicks <tyhicks@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 | 38 +++++++++++++++++--- >> security/integrity/ima/ima_queue_keys.c | 3 +- >> 5 files changed, 39 insertions(+), 9 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); > > Please abbreviate the boolean name to "hash". The test would then be > "if (hash == true)" or "if (hash)". > Will do. >> 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..0f8409d77602 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 > > ^@hash: measure buffer data hash > Agreed. Will fix. >> * >> - * Based on policy, the buffer is measured into the ima log. >> + * Measure the buffer into the IMA log, and extend the @pcr. > > IMA always measures/appraises files and measures buffer data based on > policy. The above sentence succintly summarizes what > process_buffer_measurement() does. This patch adds support for > measuring the "buffer data hash". The following would be an > appropriate change. > > * Based on policy, either the buffer data or buffer data hash is > measured > Sounds good. Will update. >> + * >> + * 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. > > This patch should be limited to adding "buffer data hash" support. > These changes don't belong in this patch. Please remove. > Agreed. Will remove. >> */ >> 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; >> @@ -849,13 +862,27 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size, >> goto out; >> } >> >> + if (measure_buf_hash) { > > ^ if (hash) { Yes. >> + 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"; > > I don't see a good no reason for defining a new audit cause. Use the > existing "hashing_error". > > thanks, > > Mimi > Thanks, Tushar >> + 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"; >> goto out; >> } >> >> - ret = ima_store_template(entry, violation, NULL, buf, pcr); >> + ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); >> if (ret < 0) { >> audit_cause = "store_entry"; >> ima_free_template_entry(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); >> } >
On 2020-12-24 5:04 a.m., Mimi Zohar wrote: > On Sat, 2020-12-12 at 10:02 -0800, Tushar Sugandhi wrote: >> IMA provides capabilities to measure file data, and in-memory buffer > > No need for the comma here. > > Up to this patch set, all the patches refer to "buffer data", not "in- > memory buffer data". This patch introduces the concept of measuring > "in-memory buffer data". Please remove "in-memory" above. > Will update the description accordingly. >> data. However, various data structures, policies, and states > > Here and everywhere else, there are two blanks after a period. > I checked this patch file in multiple text editors, but couldn’t find any instance of period followed by two spaces. I will double check again all the patches for multiple spaces, and remove them if any. >> 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, > > ^integrity of the system. > Will do. >> IMA does not provide a generic function for kernel subsystems to measure >> their integrity critical data. > > The emphasis should not be on "kernel subsystems". Simplify to "for > measuring kernel integrity critical data". > Will do. >> >> Define a new IMA hook - ima_measure_critical_data to measure kernel >> integrity critical data. > > Either "ima_measure_critical_data" is between hyphens or without any > hyphens. If not hyphenated, then you could say "named > ima_measure_critical_data", but "named" isn't necessary. Or reverse "a > new IMA hook" and "ima_measure_critical_data", adding comma's like: > Define ima_measure_critical_data, a new IMA hook, to ... > > Any of the above options work, just not a single hyphen. > Thanks for the suggestion. I will use “Define ima_measure_critical_data, a new IMA hook, to ...” >> >> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> >> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> >> --- > > <snip> > >> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c >> index 0f8409d77602..dff4bce4fb09 100644 >> --- a/security/integrity/ima/ima_main.c >> +++ b/security/integrity/ima/ima_main.c >> @@ -922,6 +922,40 @@ 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 > > Why future tense? I simply used the description from p_b_m() * @eventname: event name to be used for the buffer entry. By "buffer entry" do you mean a record in the IMA > measurement list? > Yes, a record in the IMA measurement list. Will remove the future tense and reword it to something like: * @event_name: event name for the buffer measurement entry -or- * @event_name: event name for the record in the IMA measurement list >> + * @buf: pointer to buffer containing data to measure > > ^pointer to buffer data > will do. >> + * @buf_len: length of buffer(in bytes) > > ^length of buffer data (in bytes) > will do. >> + * @measure_buf_hash: measure buffer hash > > As requested in 2/8, please abbreviate the boolean name to "hash". > Refer to section "4) Naming" in Documentation/process/coding-style.rst > for variable naming conventions. > > ^@hash: measure buffer data hash > Sounds good. Will do. >> + * >> + * 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 various data structures, >> + * policies, and states stored in kernel memory that can impact the integrity >> + * of the system. >> + * >> + * 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. > > The "/**" is the start of kernel-doc. Have you seen anywhere else in My impression was the hooks in ima_main.c e.g. ima_file_free() ima_file_mmap() required the double-asterisk ("/**"), and internal functions like ima_rdwr_violation_check() require a single-asterisk ("/*") kernel-doc.rst suggest the double-asterisk ("/**") for function comment as well. Function documentation ---------------------- The general format of a function and function-like macro kernel-doc comment is:: /** * function_name() - Brief description of function. Please let me know if you still want me to remove the double-asterisk ("/**") here. > the kernel using the @<variable name> in the longer function > description? Have you seen this style of longer function > description? Refer to Documentation/doc-guide/kernel-doc.rst and other > code for examples. > Thanks. I will remove the prefix "@" from <variable name> in the longer function description. >> + */ >> +void ima_measure_critical_data(const char *event_name, >> + const void *buf, int buf_len, > > As "buf_len" should always be >= 0, it should not be defined as a > signed variable. > Good point. I will switch to either size_t or unsigned int. >> + bool measure_buf_hash) >> +{ >> + if (!event_name || !buf || !buf_len) >> + return; >> + >> + process_buffer_measurement(NULL, buf, buf_len, event_name, >> + CRITICAL_DATA, 0, NULL, >> + measure_buf_hash); > > ^hash > Will do. > thanks, > > Mimi > Thanks, Tushar >> +} >> + >> static int __init init_ima(void) >> { >> int error; >
On 2020-12-24 5:48 a.m., Mimi Zohar wrote: > Hi Tushar, > > Please update the Subject line as, "Add policy rule support for > measuring critical data". > > On Sat, 2020-12-12 at 10:02 -0800, 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> > > This patch does not restrict measuring critical data, but adds policy > rule support for measuring critical data. please update the patch > description accordingly. > Will do. Will update the patch description accordingly. > Other than that, > > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > Thanks a lot for the Reviewed-by tag. :)
On Tue, 2021-01-05 at 12:01 -0800, Tushar Sugandhi wrote: > > >> data. However, various data structures, policies, and states > > > > Here and everywhere else, there are two blanks after a period. > > > I checked this patch file in multiple text editors, but couldn’t find > any instance of period followed by two spaces. I will double check again > all the patches for multiple spaces, and remove them if any. There should be two blanks after a period, not one blank. <snip> > >> + * > >> + * 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 various data structures, > >> + * policies, and states stored in kernel memory that can impact the integrity > >> + * of the system. > >> + * > >> + * 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. > > > > The "/**" is the start of kernel-doc. Have you seen anywhere else in > My impression was the hooks in ima_main.c e.g. ima_file_free() > ima_file_mmap() required the double-asterisk ("/**"), and internal > functions like ima_rdwr_violation_check() require a single-asterisk > ("/*") > > kernel-doc.rst suggest the double-asterisk ("/**") for function comment > as well. > > Function documentation > ---------------------- > > The general format of a function and function-like macro kernel-doc > comment is:: > > /** > * function_name() - Brief description of function. > > Please let me know if you still want me to remove the double-asterisk > ("/**") here. Yes, of course this needs to be kernel-doc and requires "/**" > > > the kernel using the @<variable name> in the longer function > > description? Have you seen this style of longer function > > description? Refer to Documentation/doc-guide/kernel-doc.rst and other > > code for examples. > > > Thanks. I will remove the prefix "@" from <variable name> in the longer > function description. Removing the @<variable name> isn't sufficient. Please look at other examples of longer function definitions before reposting. thanks, Mimi
On 2021-01-05 12:16 p.m., Mimi Zohar wrote: > On Tue, 2021-01-05 at 12:01 -0800, Tushar Sugandhi wrote: >> >>>> data. However, various data structures, policies, and states >>> >>> Here and everywhere else, there are two blanks after a period. >>> >> I checked this patch file in multiple text editors, but couldn’t find >> any instance of period followed by two spaces. I will double check again >> all the patches for multiple spaces, and remove them if any. > > There should be two blanks after a period, not one blank. > > <snip> > >>>> + * >>>> + * 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 various data structures, >>>> + * policies, and states stored in kernel memory that can impact the integrity >>>> + * of the system. >>>> + * >>>> + * 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. >>> >>> The "/**" is the start of kernel-doc. Have you seen anywhere else in >> My impression was the hooks in ima_main.c e.g. ima_file_free() >> ima_file_mmap() required the double-asterisk ("/**"), and internal >> functions like ima_rdwr_violation_check() require a single-asterisk >> ("/*") >> >> kernel-doc.rst suggest the double-asterisk ("/**") for function comment >> as well. >> >> Function documentation >> ---------------------- >> >> The general format of a function and function-like macro kernel-doc >> comment is:: >> >> /** >> * function_name() - Brief description of function. >> >> Please let me know if you still want me to remove the double-asterisk >> ("/**") here. > > Yes, of course this needs to be kernel-doc and requires "/**" > Thanks for confirming. >> >>> the kernel using the @<variable name> in the longer function >>> description? Have you seen this style of longer function >>> description? Refer to Documentation/doc-guide/kernel-doc.rst and other >>> code for examples. >>> >> Thanks. I will remove the prefix "@" from <variable name> in the longer >> function description. > > Removing the @<variable name> isn't sufficient. Please look at other > examples of longer function definitions before reposting. > Yes. Agreed. I will go as per the guidance in kernel-doc.rst Thanks again, Tushar > thanks, > > Mimi >
On 2020-12-24 6:29 a.m., Mimi Zohar wrote: > Hi Tushar, > > On Sat, 2020-12-12 at 10:02 -0800, 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. > > Restricting which kernel integrity critical data is measured is not > only of interest to system administrators. Why single them out? > system administrators are usually responsible for system policies/configurations.They own modifications in the config files like ima-policy. That's why we wanted to address them to begin with. But you are correct. This is not only of interest to sysadmins. I will make the description more generic. > Limiting which critical data is measured is based on a label, making it > flexible. In your use case scenario, you're grouping the label based > on kernel subsystem, but is that really necessary? In the broader > picture, there could be cross subsystem critical data being measured > based on a single label. > > Please think about the broader picture and re-write the patch > descirption more generically. > Makes sense. Will make the patch description more generic. >> >> Add a new IMA policy condition - "data_source:=" to the IMA func > > What is with "add"? You're "adding support for" or "defining" a new > policy condition. Remove the single hyphen, as explained in 3/8. > > Please replace "data_source" with something more generic (e.g. label). > Sounds good. Would you prefer "label" or something else like "data_label"? In the policy file the "label" looks logical and more generic than "data_label". measure func=CRITICAL_DATA label=selinux For the time being, I will stick with "label", please let me know if you prefer something else. Thanks, Tushar > thanks, > > Mimi > >> 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>
On 2020-12-24 6:41 a.m., Mimi Zohar wrote: > On Sat, 2020-12-12 at 10:02 -0800, 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". > > This sentence isn't really necessary. > Will remove. >> >> 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> > > Otherwise, > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Thanks again for the "Reviewed-by" tag. Thanks, Tushar > > thanks, > > Mimi >
<snip> >>> 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); >> >> Please abbreviate the boolean name to "hash". The test would then be >> "if (hash == true)" or "if (hash)". >> > Will do. <snip> >>> - * 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 >> >> ^@hash: measure buffer data hash >> > Agreed. Will fix. <snip> >>> 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; >>> @@ -849,13 +862,27 @@ void process_buffer_measurement(struct inode >>> *inode, const void *buf, int size, >>> goto out; >>> } >>> + if (measure_buf_hash) { >> >> ^ if (hash) { > Yes. >>> + 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"; Hi Mimi, There already exist a local struct variable named "hash" in p_b_m(). I was thinking of using "buf_hash", but that one is taken too. Maybe I should use "buf_hash" for the input bool, and rename the existing "buf_hash" local variable to "digest_hash"? Does it sound ok? Thanks, Tushar <snip>