audit: allow checking the type of audit message in the user filter

When userspace sends messages to the audit system it includes a type.
We want to be able to filter messages based on that type without have to
do the all or nothing option currently available on the
AUDIT_FILTER_TYPE filter list.  Instead we should be able to use the
AUDIT_FILTER_USER filter list and just use the message type as one part
of the matching decision.

Signed-off-by: Eric Paris <eparis@redhat.com>

include/linux/audit.h

@@ -438,7 +438,7 @@ static inline void	    audit_log_secctx(struct audit_buffer *ab, u32 secid)
 extern int		    audit_update_lsm_rules(void);
 
 				/* Private API (for audit.c only) */
-extern int audit_filter_user(void);
+extern int audit_filter_user(int type);
 extern int audit_filter_type(int type);
 extern int  audit_receive_filter(int type, int pid, int seq,
 				void *data, size_t datasz, kuid_t loginuid,

kernel/audit.c

@@ -737,7 +737,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 			return 0;
 
-		err = audit_filter_user();
+		err = audit_filter_user(msg_type);
 		if (err == 1) {
 			err = 0;
 			if (msg_type == AUDIT_USER_TTY) {

kernel/auditfilter.c

@@ -310,6 +310,18 @@ static u32 audit_to_op(u32 op)
 	return n;
 }
 
+/* check if a field is valid for a given list */
+static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
+{
+	switch(f->type) {
+	case AUDIT_MSGTYPE:
+		if (entry->rule.listnr != AUDIT_FILTER_TYPE &&
+		    entry->rule.listnr != AUDIT_FILTER_USER)
+			return -EINVAL;
+		break;
+	};
+	return 0;
+}
 
 /* Translate struct audit_rule to kernel's rule respresentation.
  * Exists for backward compatibility with userspace. */
@@ -459,6 +471,13 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 		f->gid = INVALID_GID;
 		f->lsm_str = NULL;
 		f->lsm_rule = NULL;
+
+		err = audit_field_valid(entry, f);
+		if (err)
+			goto exit_free;
+
+		err = -EINVAL;
+
 		switch(f->type) {
 		case AUDIT_UID:
 		case AUDIT_EUID:
@@ -1354,7 +1373,7 @@ int audit_compare_dname_path(const char *dname, const char *path, int parentlen)
 	return strncmp(p, dname, dlen);
 }
 
-static int audit_filter_user_rules(struct audit_krule *rule,
+static int audit_filter_user_rules(struct audit_krule *rule, int type,
 				   enum audit_state *state)
 {
 	int i;
@@ -1378,6 +1397,9 @@ static int audit_filter_user_rules(struct audit_krule *rule,
 			result = audit_uid_comparator(audit_get_loginuid(current),
 						  f->op, f->uid);
 			break;
+		case AUDIT_MSGTYPE:
+			result = audit_comparator(type, f->op, f->val);
+			break;
 		case AUDIT_SUBJ_USER:
 		case AUDIT_SUBJ_ROLE:
 		case AUDIT_SUBJ_TYPE:
@@ -1404,7 +1426,7 @@ static int audit_filter_user_rules(struct audit_krule *rule,
 	return 1;
 }
 
-int audit_filter_user(void)
+int audit_filter_user(int type)
 {
 	enum audit_state state = AUDIT_DISABLED;
 	struct audit_entry *e;
@@ -1412,7 +1434,7 @@ int audit_filter_user(void)
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
-		if (audit_filter_user_rules(&e->rule, &state)) {
+		if (audit_filter_user_rules(&e->rule, type, &state)) {
 			if (state == AUDIT_DISABLED)
 				ret = 0;
 			break;