[PATCH v2] audit: add fields to exclude filter by reusing user filter

[Richard Guy Briggs <rgb@redhat.com>]

RFE: add additional fields for use in audit filter exclude rules
https://github.com/linux-audit/audit-kernel/issues/5

Re-factor and combine audit_filter_type() with audit_filter_user() to
use audit_filter_user_rules() to enable the exclude filter to
additionally filter on PID, UID, GID, AUID, LOGINUID_SET, SUBJ_*.

The process of combining the similar audit_filter_user() and
audit_filter_type() functions, required inverting the meaning and
including the ALWAYS action of the latter.

Keep the check to quit early if the list is empty.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
v2: combine audit_filter_user() and audit_filter_type() into
audit_filter().
---

 include/linux/audit.h |    2 --
 kernel/audit.c        |    4 ++--
 kernel/audit.h        |    2 ++
 kernel/auditfilter.c  |   46 ++++++++++------------------------------------
 4 files changed, 14 insertions(+), 40 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 32cdafb..539c1d9 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -160,8 +160,6 @@ extern void audit_log_task_info(struct audit_buffer *ab,
 extern int		    audit_update_lsm_rules(void);
 
 				/* Private API (for audit.c only) */
-extern int audit_filter_user(int type);
-extern int audit_filter_type(int type);
 extern int audit_rule_change(int type, __u32 portid, int seq,
 				void *data, size_t datasz);
 extern int audit_list_rules_send(struct sk_buff *request_skb, int seq);
diff --git a/kernel/audit.c b/kernel/audit.c
index 384374a..2dfaa19 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -914,7 +914,7 @@ 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(msg_type);
+		err = audit_filter(msg_type, AUDIT_FILTER_USER);
 		if (err == 1) { /* match or error */
 			err = 0;
 			if (msg_type == AUDIT_USER_TTY) {
@@ -1362,7 +1362,7 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 	if (audit_initialized != AUDIT_INITIALIZED)
 		return NULL;
 
-	if (unlikely(audit_filter_type(type)))
+	if (unlikely(!audit_filter(type, AUDIT_FILTER_TYPE)))
 		return NULL;
 
 	if (gfp_mask & __GFP_DIRECT_RECLAIM) {
diff --git a/kernel/audit.h b/kernel/audit.h
index cbbe6bb..1879f02 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -327,6 +327,8 @@ extern pid_t audit_sig_pid;
 extern kuid_t audit_sig_uid;
 extern u32 audit_sig_sid;
 
+extern int audit_filter(int msgtype, unsigned int listtype);
+
 #ifdef CONFIG_AUDITSYSCALL
 extern int __audit_signal_info(int sig, struct task_struct *t);
 static inline int audit_signal_info(int sig, struct task_struct *t)
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 96c9a1b..f90c042 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1349,50 +1349,24 @@ static int audit_filter_user_rules(struct audit_krule *rule, int type,
 	return 1;
 }
 
-int audit_filter_user(int type)
+int audit_filter(int msgtype, unsigned int listtype)
 {
 	enum audit_state state = AUDIT_DISABLED;
 	struct audit_entry *e;
-	int rc, ret;
-
-	ret = 1; /* Audit by default */
+	int rc, result = 1; /* Audit by default */
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
-		rc = audit_filter_user_rules(&e->rule, type, &state);
-		if (rc) {
-			if (rc > 0 && state == AUDIT_DISABLED)
-				ret = 0;
-			break;
-		}
-	}
-	rcu_read_unlock();
-
-	return ret;
-}
-
-int audit_filter_type(int type)
-{
-	struct audit_entry *e;
-	int result = 0;
-
-	rcu_read_lock();
-	if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE]))
+	if (list_empty(&audit_filter_list[listtype]))
 		goto unlock_and_return;
 
-	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE],
-				list) {
-		int i;
-		for (i = 0; i < e->rule.field_count; i++) {
-			struct audit_field *f = &e->rule.fields[i];
-			if (f->type == AUDIT_MSGTYPE) {
-				result = audit_comparator(type, f->op, f->val);
-				if (!result)
-					break;
-			}
+	list_for_each_entry_rcu(e, &audit_filter_list[listtype], list) {
+		rc = audit_filter_user_rules(&e->rule, msgtype, &state);
+		if (rc) {
+			if (rc > 0 && ((state == AUDIT_DISABLED) ||
+			               (listtype == AUDIT_FILTER_TYPE)))
+				result = 0;
+			break;
 		}
-		if (result)
-			goto unlock_and_return;
 	}
 unlock_and_return:
 	rcu_read_unlock();
-- 
1.7.1