diff mbox

[2/2] IMA: Support using new creds in appraisal policy

Message ID 20171019231433.11723-2-mjg59@google.com
State New, archived
Headers show

Commit Message

Matthew Garrett Oct. 19, 2017, 11:14 p.m. UTC
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@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Eric Paris <eparis@parisplace.org>
Cc: selinux@tycho.nsa.gov
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-security-module@vger.kernel.org
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: linux-integrity@vger.kernel.org
---
 V2: Fix the IMA_CRED_CHECK defines
 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 mbox

Patch

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 a53e7e4ab06c..45ba0e4501d6 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	0x00010000
+#define IMA_CREDS_APPRAISED	0x00020000
 #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,
@@ -108,6 +112,7 @@  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;
 };