[PATCH] audit: watching subtrees

New kind of audit rule predicates: "object is visible in given subtree".
The part that can be sanely implemented, that is.  Limitations:
	* if you have hardlink from outside of tree, you'd better watch
it too (or just watch the object itself, obviously)
	* if you mount something under a watched tree, tell audit
that new chunk should be added to watched subtrees
	* if you umount something in a watched tree and it's still mounted
elsewhere, you will get matches on events happening there.  New command
tells audit to recalculate the trees, trimming such sources of false
positives.

Note that it's _not_ about path - if something mounted in several places
(multiple mount, bindings, different namespaces, etc.), the match does
_not_ depend on which one we are using for access.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 87 insertions, 0 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 6977ea5..f93c271 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -468,6 +468,21 @@ int audit_send_list(void *_dest)
 	return 0;
 }
 
+#ifdef CONFIG_AUDIT_TREE
+static int prune_tree_thread(void *unused)
+{
+	mutex_lock(&audit_cmd_mutex);
+	audit_prune_trees();
+	mutex_unlock(&audit_cmd_mutex);
+	return 0;
+}
+
+void audit_schedule_prune(void)
+{
+	kthread_run(prune_tree_thread, NULL, "audit_prune_tree");
+}
+#endif
+
 struct sk_buff *audit_make_reply(int pid, int seq, int type, int done,
 				 int multi, void *payload, int size)
 {
@@ -540,6 +555,8 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
 	case AUDIT_SIGNAL_INFO:
 	case AUDIT_TTY_GET:
 	case AUDIT_TTY_SET:
+	case AUDIT_TRIM:
+	case AUDIT_MAKE_EQUIV:
 		if (security_netlink_recv(skb, CAP_AUDIT_CONTROL))
 			err = -EPERM;
 		break;
@@ -756,6 +773,76 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 					   uid, seq, data, nlmsg_len(nlh),
 					   loginuid, sid);
 		break;
+	case AUDIT_TRIM:
+		audit_trim_trees();
+		ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
+		if (!ab)
+			break;
+		audit_log_format(ab, "auid=%u", loginuid);
+		if (sid) {
+			u32 len;
+			ctx = NULL;
+			if (selinux_sid_to_string(sid, &ctx, &len))
+				audit_log_format(ab, " ssid=%u", sid);
+			else
+				audit_log_format(ab, " subj=%s", ctx);
+			kfree(ctx);
+		}
+		audit_log_format(ab, " op=trim res=1");
+		audit_log_end(ab);
+		break;
+	case AUDIT_MAKE_EQUIV: {
+		void *bufp = data;
+		u32 sizes[2];
+		size_t len = nlmsg_len(nlh);
+		char *old, *new;
+
+		err = -EINVAL;
+		if (len < 2 * sizeof(u32))
+			break;
+		memcpy(sizes, bufp, 2 * sizeof(u32));
+		bufp += 2 * sizeof(u32);
+		len -= 2 * sizeof(u32);
+		old = audit_unpack_string(&bufp, &len, sizes[0]);
+		if (IS_ERR(old)) {
+			err = PTR_ERR(old);
+			break;
+		}
+		new = audit_unpack_string(&bufp, &len, sizes[1]);
+		if (IS_ERR(new)) {
+			err = PTR_ERR(new);
+			kfree(old);
+			break;
+		}
+		/* OK, here comes... */
+		err = audit_tag_tree(old, new);
+
+		ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
+		if (!ab) {
+			kfree(old);
+			kfree(new);
+			break;
+		}
+		audit_log_format(ab, "auid=%u", loginuid);
+		if (sid) {
+			u32 len;
+			ctx = NULL;
+			if (selinux_sid_to_string(sid, &ctx, &len))
+				audit_log_format(ab, " ssid=%u", sid);
+			else
+				audit_log_format(ab, " subj=%s", ctx);
+			kfree(ctx);
+		}
+		audit_log_format(ab, " op=make_equiv old=");
+		audit_log_untrustedstring(ab, old);
+		audit_log_format(ab, " new=");
+		audit_log_untrustedstring(ab, new);
+		audit_log_format(ab, " res=%d", !err);
+		audit_log_end(ab);
+		kfree(old);
+		kfree(new);
+		break;
+	}
 	case AUDIT_SIGNAL_INFO:
 		err = selinux_sid_to_string(audit_sig_sid, &ctx, &len);
 		if (err)