[PATCH] Fix audit control message checks

The audit control messages are sent over netlink.  Permission checks are
done on the process receiving the message, which may not be the same as the
process sending the message.  This patch switches the netlink_send security
hooks to calculate the effective capabilities based on the sender.  Then
audit_receive_msg performs capability checks based on that.

It also introduces the CAP_AUDIT_WRITE and CAP_AUDIT_CONTROL capabilities,
and replaces the previous CAP_SYS_ADMIN checks in audit code with the
appropriate checks.

- Simplified dummy_netlink_send given that dummy now keeps track of
  capabilities.

- Many fixes based on feedback from <linux-audit@redhat.com> list.

- Removed the netlink_msg_type helper function.

- Switch to using CAP_AUDIT_WRITE and CAP_AUDIT_CONTROL.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Stephen Smalley <sds@epoch.ncsc.mil>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 44 insertions, 9 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index e21f947bacf2..5deb43753406 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -300,21 +300,55 @@ nlmsg_failure:			/* Used by NLMSG_PUT */
 		kfree_skb(skb);
 }
 
+/*
+ * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
+ * control messages.
+ */
+static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
+{
+	int err = 0;
+
+	switch (msg_type) {
+	case AUDIT_GET:
+	case AUDIT_LIST:
+	case AUDIT_SET:
+	case AUDIT_LOGIN:
+	case AUDIT_ADD:
+	case AUDIT_DEL:
+		if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
+			err = -EPERM;
+		break;
+	case AUDIT_USER:
+		if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
+			err = -EPERM;
+		break;
+	default:  /* bad msg */
+		err = -EINVAL;
+	}
+
+	return err;
+}
+
 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	u32			uid, pid, seq;
 	void			*data;
 	struct audit_status	*status_get, status_set;
 	struct audit_login	*login;
-	int			err = 0;
+	int			err;
 	struct audit_buffer	*ab;
+	u16			msg_type = nlh->nlmsg_type;
+
+	err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
+	if (err)
+		return err;
 
 	pid  = NETLINK_CREDS(skb)->pid;
 	uid  = NETLINK_CREDS(skb)->uid;
 	seq  = nlh->nlmsg_seq;
 	data = NLMSG_DATA(nlh);
 
-	switch (nlh->nlmsg_type) {
+	switch (msg_type) {
 	case AUDIT_GET:
 		status_set.enabled	 = audit_enabled;
 		status_set.failure	 = audit_failure;
@@ -327,8 +361,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 				 &status_set, sizeof(status_set));
 		break;
 	case AUDIT_SET:
-		if (!capable(CAP_SYS_ADMIN))
-			return -EPERM;
+		if (nlh->nlmsg_len < sizeof(struct audit_status))
+			return -EINVAL;
 		status_get   = (struct audit_status *)data;
 		if (status_get->mask & AUDIT_STATUS_ENABLED) {
 			err = audit_set_enabled(status_get->enabled);
@@ -364,8 +398,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		audit_log_end(ab);
 		break;
 	case AUDIT_LOGIN:
-		if (!capable(CAP_SYS_ADMIN))
-			return -EPERM;
+		if (nlh->nlmsg_len < sizeof(struct audit_login))
+			return -EINVAL;
 		login = (struct audit_login *)data;
 		ab = audit_log_start(NULL);
 		if (ab) {
@@ -384,9 +418,12 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 					 login->loginuid);
 #endif
 		break;
-	case AUDIT_LIST:
 	case AUDIT_ADD:
 	case AUDIT_DEL:
+		if (nlh->nlmsg_len < sizeof(struct audit_rule))
+			return -EINVAL;
+		/* fallthrough */
+	case AUDIT_LIST:
 #ifdef CONFIG_AUDITSYSCALL
 		err = audit_receive_filter(nlh->nlmsg_type, pid, uid, seq,
 					   data);
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index aa617bbe49b0..5efa31c1dc83 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -250,8 +250,6 @@ int audit_receive_filter(int type, int pid, int uid, int seq, void *data)
 		audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
 		break;
 	case AUDIT_ADD:
-		if (!capable(CAP_SYS_ADMIN))
-			return -EPERM;
 		if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
 			return -ENOMEM;
 		if (audit_copy_rule(&entry->rule, data)) {