[PATCH 2/2] IMA: Support using new creds in appraisal policy
Matthew Garrett
mjg59 at google.com
Mon Oct 16 20:37:09 UTC 2017
The existing BPRM_CHECK functionality in IMA validates against the
credentials of the existing process, not any new credentials that the
child process may transition to. Add an additional CREDS_CHECK target
and refactor IMA to pass the appropriate creds structure. In
ima_bprm_check(), check with both the existing process credentials and
the credentials that will be committed when the new process is started.
Signed-off-by: Matthew Garrett <mjg59 at google.com>
Cc: Paul Moore <paul at paul-moore.com>
Cc: Stephen Smalley <sds at tycho.nsa.gov>
Cc: Eric Paris <eparis at parisplace.org>
Cc: selinux at tycho.nsa.gov
Cc: Casey Schaufler <casey at schaufler-ca.com>
Cc: linux-security-module at vger.kernel.org
Cc: Mimi Zohar <zohar at linux.vnet.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin at gmail.com>
Cc: linux-integrity at vger.kernel.org
---
Documentation/ABI/testing/ima_policy | 2 +-
security/integrity/iint.c | 1 +
security/integrity/ima/ima.h | 7 ++++---
security/integrity/ima/ima_api.c | 8 +++++---
security/integrity/ima/ima_appraise.c | 10 +++++++++-
security/integrity/ima/ima_main.c | 26 +++++++++++++++++---------
security/integrity/ima/ima_policy.c | 19 ++++++++++++-------
security/integrity/integrity.h | 9 +++++++--
8 files changed, 56 insertions(+), 26 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index e76432b9954d..5dc9eed035fb 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -25,7 +25,7 @@ Description:
[obj_user=] [obj_role=] [obj_type=]]
option: [[appraise_type=]] [permit_directio]
- base: func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
+ base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index 6fc888ca468e..ad30094a58b4 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -78,6 +78,7 @@ static void iint_free(struct integrity_iint_cache *iint)
iint->ima_mmap_status = INTEGRITY_UNKNOWN;
iint->ima_bprm_status = INTEGRITY_UNKNOWN;
iint->ima_read_status = INTEGRITY_UNKNOWN;
+ iint->ima_creds_status = INTEGRITY_UNKNOWN;
iint->evm_status = INTEGRITY_UNKNOWN;
iint->measured_pcrs = 0;
kmem_cache_free(iint_cache, iint);
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d52b487ad259..0703a96072b5 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -177,6 +177,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
hook(FILE_CHECK) \
hook(MMAP_CHECK) \
hook(BPRM_CHECK) \
+ hook(CREDS_CHECK) \
hook(POST_SETATTR) \
hook(MODULE_CHECK) \
hook(FIRMWARE_CHECK) \
@@ -191,7 +192,7 @@ enum ima_hooks {
};
/* LIM API function definitions */
-int ima_get_action(struct inode *inode, int mask,
+int ima_get_action(struct inode *inode, const struct cred *cred, int mask,
enum ima_hooks func, int *pcr);
int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
int ima_collect_measurement(struct integrity_iint_cache *iint,
@@ -212,8 +213,8 @@ void ima_free_template_entry(struct ima_template_entry *entry);
const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
/* IMA policy related functions */
-int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
- int flags, int *pcr);
+int ima_match_policy(struct inode *inode, const struct cred *cred,
+ enum ima_hooks func, int mask, int flags, int *pcr);
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 c2edba8de35e..ff33b7e65a07 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -157,6 +157,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
/**
* ima_get_action - appraise & measure decision based on policy.
* @inode: pointer to inode to measure
+ * @cred: pointer to credentials structure to validate
* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
* MAY_APPEND)
* @func: caller identifier
@@ -165,20 +166,21 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
* The policy is defined in terms of keypairs:
* subj=, obj=, type=, func=, mask=, fsmagic=
* subj,obj, and type: are LSM specific.
- * func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
+ * func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
* mask: contains the permission mask
* fsmagic: hex value
*
* Returns IMA_MEASURE, IMA_APPRAISE mask.
*
*/
-int ima_get_action(struct inode *inode, int mask, enum ima_hooks func, int *pcr)
+int ima_get_action(struct inode *inode, const struct cred *cred, int mask,
+ enum ima_hooks func, int *pcr)
{
int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
flags &= ima_policy_flag;
- return ima_match_policy(inode, func, mask, flags, pcr);
+ return ima_match_policy(inode, cred, func, mask, flags, pcr);
}
/*
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 809ba70fbbbf..137b8d1708c6 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -53,7 +53,8 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
if (!ima_appraise)
return 0;
- return ima_match_policy(inode, func, mask, IMA_APPRAISE, NULL);
+ return ima_match_policy(inode, current_cred(), func, mask,
+ IMA_APPRAISE, NULL);
}
static int ima_fix_xattr(struct dentry *dentry,
@@ -86,6 +87,8 @@ enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
return iint->ima_mmap_status;
case BPRM_CHECK:
return iint->ima_bprm_status;
+ case CREDS_CHECK:
+ return iint->ima_creds_status;
case FILE_CHECK:
case POST_SETATTR:
return iint->ima_file_status;
@@ -106,6 +109,8 @@ static void ima_set_cache_status(struct integrity_iint_cache *iint,
case BPRM_CHECK:
iint->ima_bprm_status = status;
break;
+ case CREDS_CHECK:
+ iint->ima_creds_status = status;
case FILE_CHECK:
case POST_SETATTR:
iint->ima_file_status = status;
@@ -127,6 +132,9 @@ static void ima_cache_flags(struct integrity_iint_cache *iint,
case BPRM_CHECK:
iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
break;
+ case CREDS_CHECK:
+ iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
+ break;
case FILE_CHECK:
case POST_SETATTR:
iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 2aebb7984437..f41aa427792b 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -155,8 +155,9 @@ void ima_file_free(struct file *file)
ima_check_last_writer(iint, inode, file);
}
-static int process_measurement(struct file *file, char *buf, loff_t size,
- int mask, enum ima_hooks func, int opened)
+static int process_measurement(struct file *file, const struct cred *cred,
+ char *buf, loff_t size, int mask,
+ enum ima_hooks func, int opened)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
@@ -178,7 +179,7 @@ static int process_measurement(struct file *file, char *buf, loff_t size,
* bitmask based on the appraise/audit/measurement policy.
* Included is the appraise submask.
*/
- action = ima_get_action(inode, mask, func, &pcr);
+ action = ima_get_action(inode, cred, mask, func, &pcr);
violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
(ima_policy_flag & IMA_MEASURE));
if (!action && !violation_check)
@@ -282,8 +283,8 @@ static int process_measurement(struct file *file, char *buf, loff_t size,
int ima_file_mmap(struct file *file, unsigned long prot)
{
if (file && (prot & PROT_EXEC))
- return process_measurement(file, NULL, 0, MAY_EXEC,
- MMAP_CHECK, 0);
+ return process_measurement(file, current_cred(), NULL, 0,
+ MAY_EXEC, MMAP_CHECK, 0);
return 0;
}
@@ -302,8 +303,14 @@ int ima_file_mmap(struct file *file, unsigned long prot)
*/
int ima_bprm_check(struct linux_binprm *bprm)
{
- return process_measurement(bprm->file, NULL, 0, MAY_EXEC,
- BPRM_CHECK, 0);
+ int ret;
+
+ ret = process_measurement(bprm->file, current_cred(), NULL, 0,
+ MAY_EXEC, BPRM_CHECK, 0);
+ if (ret)
+ return ret;
+ return process_measurement(bprm->file, bprm->cred, NULL, 0,
+ MAY_EXEC, CREDS_CHECK, 0);
}
/**
@@ -318,7 +325,7 @@ int ima_bprm_check(struct linux_binprm *bprm)
*/
int ima_file_check(struct file *file, int mask, int opened)
{
- return process_measurement(file, NULL, 0,
+ return process_measurement(file, current_cred(), NULL, 0,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
MAY_APPEND), FILE_CHECK, opened);
}
@@ -413,7 +420,8 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
}
func = read_idmap[read_id] ?: FILE_CHECK;
- return process_measurement(file, buf, size, MAY_READ, func, 0);
+ return process_measurement(file, current_cred(), buf, size, MAY_READ,
+ func, 0);
}
static int __init init_ima(void)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 95209a5f8595..c9d5735711eb 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -247,10 +247,9 @@ static void ima_lsm_update_rules(void)
* Returns true on rule match, false on failure.
*/
static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
- enum ima_hooks func, int mask)
+ const struct cred *cred, enum ima_hooks func,
+ int mask)
{
- struct task_struct *tsk = current;
- const struct cred *cred = current_cred();
int i;
if ((rule->flags & IMA_FUNC) &&
@@ -305,7 +304,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
case LSM_SUBJ_USER:
case LSM_SUBJ_ROLE:
case LSM_SUBJ_TYPE:
- security_task_getsecid(tsk, &sid);
+ security_cred_getsecid(cred, &sid);
rc = security_filter_rule_match(sid,
rule->lsm[i].type,
Audit_equal,
@@ -339,6 +338,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
return IMA_MMAP_APPRAISE;
case BPRM_CHECK:
return IMA_BPRM_APPRAISE;
+ case CREDS_CHECK:
+ return IMA_CREDS_APPRAISE;
case FILE_CHECK:
case POST_SETATTR:
return IMA_FILE_APPRAISE;
@@ -351,6 +352,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
/**
* ima_match_policy - decision based on LSM and other conditions
* @inode: pointer to an inode for which the policy decision is being made
+ * @cred: pointer to a credentials structure for which the policy decision is
+ * being made
* @func: IMA hook identifier
* @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
* @pcr: set the pcr to extend
@@ -362,8 +365,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
* list when walking it. Reads are many orders of magnitude more numerous
* than writes so ima_match_policy() is classical RCU candidate.
*/
-int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
- int flags, int *pcr)
+int ima_match_policy(struct inode *inode, const struct cred *cred,
+ enum ima_hooks func, int mask, int flags, int *pcr)
{
struct ima_rule_entry *entry;
int action = 0, actmask = flags | (flags << 1);
@@ -374,7 +377,7 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
if (!(entry->action & actmask))
continue;
- if (!ima_match_rules(entry, inode, func, mask))
+ if (!ima_match_rules(entry, inode, cred, func, mask))
continue;
action |= entry->flags & IMA_ACTION_FLAGS;
@@ -691,6 +694,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
entry->func = MMAP_CHECK;
else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
entry->func = BPRM_CHECK;
+ else if (strcmp(args[0].from, "CREDS_CHECK") == 0)
+ entry->func = CREDS_CHECK;
else if (strcmp(args[0].from, "KEXEC_KERNEL_CHECK") ==
0)
entry->func = KEXEC_KERNEL_CHECK;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 0a721c110e92..8d532c3557b5 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -48,10 +48,14 @@
#define IMA_BPRM_APPRAISED 0x00002000
#define IMA_READ_APPRAISE 0x00004000
#define IMA_READ_APPRAISED 0x00008000
+#define IMA_CREDS_APPRAISE 0x00004000
+#define IMA_CREDS_APPRAISED 0x00008000
#define IMA_APPRAISE_SUBMASK (IMA_FILE_APPRAISE | IMA_MMAP_APPRAISE | \
- IMA_BPRM_APPRAISE | IMA_READ_APPRAISE)
+ IMA_BPRM_APPRAISE | IMA_READ_APPRAISE | \
+ IMA_CREDS_APPRAISE)
#define IMA_APPRAISED_SUBMASK (IMA_FILE_APPRAISED | IMA_MMAP_APPRAISED | \
- IMA_BPRM_APPRAISED | IMA_READ_APPRAISED)
+ IMA_BPRM_APPRAISED | IMA_READ_APPRAISED | \
+ IMA_CREDS_APPRAISED)
enum evm_ima_xattr_type {
IMA_XATTR_DIGEST = 0x01,
@@ -109,6 +113,7 @@ struct integrity_iint_cache {
enum integrity_status ima_mmap_status:4;
enum integrity_status ima_bprm_status:4;
enum integrity_status ima_read_status:4;
+ enum integrity_status ima_creds_status:4;
enum integrity_status evm_status:4;
struct ima_digest_data *ima_hash;
};
--
2.15.0.rc0.271.g36b669edcc-goog
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