ima: audit log hashes

This adds an 'audit' policy action which audit logs file measurements.

Changelog v6:
 - use new action flag handling (Dmitry Kasatkin).
 - removed whitespace (Mimi)

Changelog v5:
 - use audit_log_untrustedstring.

Changelog v4:
 - cleanup digest -> hash conversion.
 - use filename rather than d_path in ima_audit_measurement.

Changelog v3:
 - Use newly exported audit_log_task_info for logging pid/ppid/uid/etc.
 - Update the ima_policy ABI documentation.

Changelog v2:
 - Use 'audit' action rather than 'measure_and_audit' to permit
 auditing in the absence of measuring..

Changelog v1:
 - Initial posting.

Signed-off-by: Peter Moody <pmoody@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Documentation/ABI/testing/ima_policy

@@ -17,7 +17,7 @@ Description:
 
 		rule format: action [condition ...]
 
-		action: measure | dont_measure | appraise | dont_appraise
+		action: measure | dont_measure | appraise | dont_appraise | audit
 		condition:= base | lsm
 			base:	[[func=] [mask=] [fsmagic=] [uid=] [fowner]]
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]

security/integrity/ima/ima.h

@@ -114,6 +114,8 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 			    struct file *file);
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   const unsigned char *filename);
+void ima_audit_measurement(struct integrity_iint_cache *iint,
+			   const unsigned char *filename);
 int ima_store_template(struct ima_template_entry *entry, int violation,
 		       struct inode *inode);
 void ima_template_show(struct seq_file *m, void *e, enum ima_show_type show);

security/integrity/ima/ima_api.c

@@ -114,7 +114,7 @@ err_out:
  */
 int ima_get_action(struct inode *inode, int mask, int function)
 {
-	int flags = IMA_MEASURE | IMA_APPRAISE;
+	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
 
 	if (!ima_appraise)
 		flags &= ~IMA_APPRAISE;
@@ -207,3 +207,33 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
 	if (result < 0)
 		kfree(entry);
 }
+
+void ima_audit_measurement(struct integrity_iint_cache *iint,
+			   const unsigned char *filename)
+{
+	struct audit_buffer *ab;
+	char hash[(IMA_DIGEST_SIZE * 2) + 1];
+	int i;
+
+	if (iint->flags & IMA_AUDITED)
+		return;
+
+	for (i = 0; i < IMA_DIGEST_SIZE; i++)
+		hex_byte_pack(hash + (i * 2), iint->ima_xattr.digest[i]);
+	hash[i * 2] = '\0';
+
+	ab = audit_log_start(current->audit_context, GFP_KERNEL,
+			     AUDIT_INTEGRITY_RULE);
+	if (!ab)
+		return;
+
+	audit_log_format(ab, "file=");
+	audit_log_untrustedstring(ab, filename);
+	audit_log_format(ab, " hash=");
+	audit_log_untrustedstring(ab, hash);
+
+	audit_log_task_info(ab, current);
+	audit_log_end(ab);
+
+	iint->flags |= IMA_AUDITED;
+}

security/integrity/ima/ima_main.c

@@ -156,8 +156,8 @@ static int process_measurement(struct file *file, const unsigned char *filename,
 	if (!ima_initialized || !S_ISREG(inode->i_mode))
 		return 0;
 
-	/* Determine if in appraise/measurement policy,
-	 * returns IMA_MEASURE, IMA_APPRAISE bitmask.  */
+	/* Determine if in appraise/audit/measurement policy,
+	 * returns IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT bitmask.  */
 	action = ima_get_action(inode, mask, function);
 	if (!action)
 		return 0;
@@ -171,7 +171,8 @@ static int process_measurement(struct file *file, const unsigned char *filename,
 		goto out;
 
 	/* Determine if already appraised/measured based on bitmask
-	 * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED) */
+	 * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED,
+	 *  IMA_AUDIT, IMA_AUDITED) */
 	iint->flags |= action;
 	action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 
@@ -202,6 +203,8 @@ static int process_measurement(struct file *file, const unsigned char *filename,
 	if (action & IMA_APPRAISE)
 		rc = ima_appraise_measurement(iint, file,
 					      !pathname ? filename : pathname);
+	if (action & IMA_AUDIT)
+		ima_audit_measurement(iint, !pathname ? filename : pathname);
 	kfree(pathbuf);
 out:
 	mutex_unlock(&inode->i_mutex);

security/integrity/ima/ima_policy.c

@@ -31,6 +31,7 @@
 #define DONT_MEASURE	0x0002
 #define APPRAISE	0x0004	/* same as IMA_APPRAISE */
 #define DONT_APPRAISE	0x0008
+#define AUDIT		0x0040
 
 #define MAX_LSM_RULES 6
 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
@@ -277,6 +278,7 @@ enum {
 	Opt_err = -1,
 	Opt_measure = 1, Opt_dont_measure,
 	Opt_appraise, Opt_dont_appraise,
+	Opt_audit,
 	Opt_obj_user, Opt_obj_role, Opt_obj_type,
 	Opt_subj_user, Opt_subj_role, Opt_subj_type,
 	Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner
@@ -287,6 +289,7 @@ static match_table_t policy_tokens = {
 	{Opt_dont_measure, "dont_measure"},
 	{Opt_appraise, "appraise"},
 	{Opt_dont_appraise, "dont_appraise"},
+	{Opt_audit, "audit"},
 	{Opt_obj_user, "obj_user=%s"},
 	{Opt_obj_role, "obj_role=%s"},
 	{Opt_obj_type, "obj_type=%s"},
@@ -379,6 +382,14 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 
 			entry->action = DONT_APPRAISE;
 			break;
+		case Opt_audit:
+			ima_log_string(ab, "action", "audit");
+
+			if (entry->action != UNKNOWN)
+				result = -EINVAL;
+
+			entry->action = AUDIT;
+			break;
 		case Opt_func:
 			ima_log_string(ab, "func", args[0].from);
 

security/integrity/integrity.h

@@ -22,12 +22,15 @@
 #define IMA_APPRAISED		0x0008
 /*#define IMA_COLLECT		0x0010  do not use this flag */
 #define IMA_COLLECTED		0x0020
+#define IMA_AUDIT		0x0040
+#define IMA_AUDITED		0x0080
 
 /* iint cache flags */
 #define IMA_DIGSIG		0x0100
 
-#define IMA_DO_MASK		(IMA_MEASURE | IMA_APPRAISE)
-#define IMA_DONE_MASK		(IMA_MEASURED | IMA_APPRAISED | IMA_COLLECTED)
+#define IMA_DO_MASK		(IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT)
+#define IMA_DONE_MASK		(IMA_MEASURED | IMA_APPRAISED | IMA_AUDITED \
+				 | IMA_COLLECTED)
 
 enum evm_ima_xattr_type {
 	IMA_XATTR_DIGEST = 0x01,