sctp: add verification checks to SCTP_AUTH_KEY option

The structure used for SCTP_AUTH_KEY option contains a
length that needs to be verfied to prevent buffer overflow
conditions. Spoted by Eugene Teo <[e-mail]>.

Signed-off-by: Vlad Yasevich <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/sctp/auth.c

···
 {
 	struct sctp_auth_bytes *key;
 
+	/* Verify that we are not going to overflow INT_MAX */
+	if ((INT_MAX - key_len) < sizeof(struct sctp_auth_bytes))
+		return NULL;
+
 	/* Allocate the shared key */
 	key = kmalloc(sizeof(struct sctp_auth_bytes) + key_len, gfp);
 	if (!key)

net/sctp/socket.c

···
 		goto out;
 	}
 
+	if (authkey->sca_keylength > optlen) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	asoc = sctp_id2assoc(sk, authkey->sca_assoc_id);
 	if (!asoc && authkey->sca_assoc_id && sctp_style(sk, UDP)) {
 		ret = -EINVAL;