* [PATCH v1 1/3] ima: define ima_trusted_for hook
@ 2021-10-14 13:01 Mimi Zohar
2021-10-14 13:01 ` [PATCH v1 2/3] fs: extend the trusted_for syscall to call IMA Mimi Zohar
2021-10-14 13:01 ` [PATCH v1 3/3] security: define a trusted_for hook Mimi Zohar
0 siblings, 2 replies; 3+ messages in thread
From: Mimi Zohar @ 2021-10-14 13:01 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Mimi Zohar, Al Viro, Andrew Morton, linux-integrity,
linux-kernel, linux-security-module, Casey Schaufler
A major interpreter integrity gap exists which allows files read by
the interpreter to be executed without measuring the file or verifying
the file's signature.
The kernel has no knowledge about the file being read by the interpreter.
Only the interpreter knows the context(eg. data, execute) and must be
trusted to provide that information accurately.
To close this integrity gap, define an ima_trusted_for hook to allow
IMA to measure the file and verify the file's signature based on policy.
Sample policy rules:
measure func=TRUSTED_FOR_CHECK
appraise func=TRUSTED_FOR_CHECK appraise_type=imasig
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
Documentation/ABI/testing/ima_policy | 2 +-
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_main.c | 23 +++++++++++++++++++++++
security/integrity/ima/ima_policy.c | 3 +++
4 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index e1a04bd3b9e5..85618e726801 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -34,7 +34,7 @@ Description:
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
- [SETXATTR_CHECK]
+ [SETXATTR_CHECK] [TRUSTED_FOR_CHECK]
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
[[^]MAY_EXEC]
fsmagic:= hex value
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index be965a8715e4..827236dbbefb 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -202,6 +202,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
hook(KEY_CHECK, key) \
hook(CRITICAL_DATA, critical_data) \
hook(SETXATTR_CHECK, setxattr_check) \
+ hook(TRUSTED_FOR_CHECK, trusted_for_check) \
hook(MAX_CHECK, none)
#define __ima_hook_enumify(ENUM, str) ENUM,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 465865412100..e09054ac3352 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -26,6 +26,7 @@
#include <linux/ima.h>
#include <linux/iversion.h>
#include <linux/fs.h>
+#include <uapi/linux/trusted-for.h>
#include "ima.h"
@@ -519,6 +520,28 @@ int ima_file_check(struct file *file, int mask)
}
EXPORT_SYMBOL_GPL(ima_file_check);
+/**
+ * ima_trusted_for - based on policy, measure/appraise/audit measurement
+ * @file: pointer to the file to be measured/appraised/audit
+ * @usage: limit enumeration to TRUSTED_FOR_EXECUTION
+ *
+ * Measure/appraise/audit files being executed by an interpreter.
+ *
+ * On success return 0. On integrity appraisal error, assuming the file
+ * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
+ */
+int ima_trusted_for(struct file *file, const enum trusted_for_usage usage)
+{
+ u32 secid;
+
+ if (usage != TRUSTED_FOR_EXECUTION)
+ return 0;
+
+ security_task_getsecid_subj(current, &secid);
+ return process_measurement(file, current_cred(), secid, NULL,
+ 0, MAY_EXEC, TRUSTED_FOR_CHECK);
+}
+
static int __ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
{
struct integrity_iint_cache *iint;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 320ca80aacab..847803a24201 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1210,6 +1210,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
case POST_SETATTR:
case FIRMWARE_CHECK:
case POLICY_CHECK:
+ case TRUSTED_FOR_CHECK:
if (entry->flags & ~(IMA_FUNC | IMA_MASK | IMA_FSMAGIC |
IMA_UID | IMA_FOWNER | IMA_FSUUID |
IMA_INMASK | IMA_EUID | IMA_PCR |
@@ -1423,6 +1424,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
/* PATH_CHECK is for backwards compat */
else if (strcmp(args[0].from, "PATH_CHECK") == 0)
entry->func = FILE_CHECK;
+ else if (strcmp(args[0].from, "TRUSTED_FOR_CHECK") == 0)
+ entry->func = TRUSTED_FOR_CHECK;
else if (strcmp(args[0].from, "MODULE_CHECK") == 0)
entry->func = MODULE_CHECK;
else if (strcmp(args[0].from, "FIRMWARE_CHECK") == 0)
--
2.27.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v1 2/3] fs: extend the trusted_for syscall to call IMA
2021-10-14 13:01 [PATCH v1 1/3] ima: define ima_trusted_for hook Mimi Zohar
@ 2021-10-14 13:01 ` Mimi Zohar
2021-10-14 13:01 ` [PATCH v1 3/3] security: define a trusted_for hook Mimi Zohar
1 sibling, 0 replies; 3+ messages in thread
From: Mimi Zohar @ 2021-10-14 13:01 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Mimi Zohar, Al Viro, Andrew Morton, linux-integrity,
linux-kernel, linux-security-module, Casey Schaufler
Extend the trusted_for syscall to call the newly defined
ima_trusted_for hook.
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
fs/open.c | 3 +++
include/linux/ima.h | 9 +++++++++
2 files changed, 12 insertions(+)
diff --git a/fs/open.c b/fs/open.c
index c79c138a638c..4d54e2a727e1 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -585,6 +585,9 @@ SYSCALL_DEFINE3(trusted_for, const int, fd, const enum trusted_for_usage, usage,
err = inode_permission(file_mnt_user_ns(f.file), inode,
mask | MAY_ACCESS);
+ if (!err)
+ err = ima_trusted_for(f.file, usage);
+
out_fd:
fdput(f);
return err;
diff --git a/include/linux/ima.h b/include/linux/ima.h
index b6ab66a546ae..603df9932817 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -12,12 +12,15 @@
#include <linux/security.h>
#include <linux/kexec.h>
#include <crypto/hash_info.h>
+#include <uapi/linux/trusted-for.h>
struct linux_binprm;
#ifdef CONFIG_IMA
extern enum hash_algo ima_get_current_hash_algo(void);
extern int ima_bprm_check(struct linux_binprm *bprm);
extern int ima_file_check(struct file *file, int mask);
+extern int ima_trusted_for(struct file *file,
+ const enum trusted_for_usage usage);
extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
struct inode *inode);
extern void ima_file_free(struct file *file);
@@ -81,6 +84,12 @@ static inline int ima_file_check(struct file *file, int mask)
return 0;
}
+static inline int ima_trusted_for(struct file *file,
+ const enum trusted_for_usage usage)
+{
+ return 0;
+}
+
static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
struct inode *inode)
{
--
2.27.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v1 3/3] security: define a trusted_for hook
2021-10-14 13:01 [PATCH v1 1/3] ima: define ima_trusted_for hook Mimi Zohar
2021-10-14 13:01 ` [PATCH v1 2/3] fs: extend the trusted_for syscall to call IMA Mimi Zohar
@ 2021-10-14 13:01 ` Mimi Zohar
1 sibling, 0 replies; 3+ messages in thread
From: Mimi Zohar @ 2021-10-14 13:01 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Mimi Zohar, Al Viro, Andrew Morton, linux-integrity,
linux-kernel, linux-security-module, Casey Schaufler
Extend the trusted_for syscall to call the security_trusted_for hook,
which calls registered LSMs and IMA, instead of calling IMA directly.
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
Mickaël, Casey, assuming there is a need...
fs/open.c | 2 +-
include/linux/lsm_hook_defs.h | 3 +++
include/linux/lsm_hooks.h | 6 ++++++
include/linux/security.h | 12 ++++++++++++
security/security.c | 10 ++++++++++
5 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/fs/open.c b/fs/open.c
index 4d54e2a727e1..75336ca7020d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -586,7 +586,7 @@ SYSCALL_DEFINE3(trusted_for, const int, fd, const enum trusted_for_usage, usage,
mask | MAY_ACCESS);
if (!err)
- err = ima_trusted_for(f.file, usage);
+ err = security_trusted_for(f.file, usage);
out_fd:
fdput(f);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 2adeea44c0d5..f847fc0fd030 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -402,3 +402,6 @@ LSM_HOOK(void, LSM_RET_VOID, perf_event_free, struct perf_event *event)
LSM_HOOK(int, 0, perf_event_read, struct perf_event *event)
LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
#endif /* CONFIG_PERF_EVENTS */
+
+LSM_HOOK(int, 0, trusted_for, struct file *file,
+ const enum trusted_for_usage usage)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 5c4c5c0602cb..88e4f08f01ca 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1557,6 +1557,12 @@
* Read perf_event security info if allowed.
* @perf_event_write:
* Write perf_event security info if allowed.
+ *
+ * Security hooks for trusted applications (e.g. interpreters)
+ *
+ * @trusted_for:
+ * Return kernel file integrity status to trusted application
+ *
*/
union security_list_options {
#define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__);
diff --git a/include/linux/security.h b/include/linux/security.h
index 5b7288521300..b067e22c8903 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -31,6 +31,7 @@
#include <linux/err.h>
#include <linux/string.h>
#include <linux/mm.h>
+#include <uapi/linux/trusted-for.h>
struct linux_binprm;
struct cred;
@@ -2038,4 +2039,15 @@ static inline int security_perf_event_write(struct perf_event *event)
#endif /* CONFIG_SECURITY */
#endif /* CONFIG_PERF_EVENTS */
+#ifdef CONFIG_SECURITY
+extern int security_trusted_for(struct file *file,
+ const enum trusted_for_usage usage);
+#else
+static int security_trusted_for(struct file *file,
+ const enum trusted_for_usage usage)
+{
+ return 0;
+}
+#endif /* CONFIG_SECURITY */
+
#endif /* ! __LINUX_SECURITY_H */
diff --git a/security/security.c b/security/security.c
index 9ffa9e9c5c55..f8e2a131d5cd 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2625,3 +2625,13 @@ int security_perf_event_write(struct perf_event *event)
return call_int_hook(perf_event_write, 0, event);
}
#endif /* CONFIG_PERF_EVENTS */
+
+int security_trusted_for(struct file *file, const enum trusted_for_usage usage)
+{
+ int ret;
+
+ ret = call_int_hook(trusted_for, 0, file, usage);
+ if (ret)
+ return ret;
+ return ima_trusted_for(file, usage);
+}
--
2.27.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-10-14 13:04 UTC | newest]
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