sctp: fix potential panics in the SCTP-AUTH API.

All of the SCTP-AUTH socket options could cause a panic
if the extension is disabled and the API is envoked.

Additionally, there were some additional assumptions that
certain pointers would always be valid which may not
always be the case.

This patch hardens the API and address all of the crash
scenarios.

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

net/sctp/endpointola.c

···
 
 		/* Initialize the CHUNKS parameter */
 		auth_chunks->param_hdr.type = SCTP_PARAM_CHUNKS;
+		auth_chunks->param_hdr.length = htons(sizeof(sctp_paramhdr_t));
 
 		/* If the Add-IP functionality is enabled, we must
 		 * authenticate, ASCONF and ASCONF-ACK chunks
···
 		if (sctp_addip_enable) {
 			auth_chunks->chunks[0] = SCTP_CID_ASCONF;
 			auth_chunks->chunks[1] = SCTP_CID_ASCONF_ACK;
-			auth_chunks->param_hdr.length =
-					htons(sizeof(sctp_paramhdr_t) + 2);
+			auth_chunks->param_hdr.length += htons(2);
 		}
 	}
 

net/sctp/socket.c

···
 {
 	struct sctp_authchunk val;
 
+	if (!sctp_auth_enable)
+		return -EACCES;
+
 	if (optlen != sizeof(struct sctp_authchunk))
 		return -EINVAL;
 	if (copy_from_user(&val, optval, optlen))
···
 {
 	struct sctp_hmacalgo *hmacs;
 	int err;
+
+	if (!sctp_auth_enable)
+		return -EACCES;
 
 	if (optlen < sizeof(struct sctp_hmacalgo))
 		return -EINVAL;
···
 	struct sctp_association *asoc;
 	int ret;
 
+	if (!sctp_auth_enable)
+		return -EACCES;
+
 	if (optlen <= sizeof(struct sctp_authkey))
 		return -EINVAL;
 
···
 	struct sctp_authkeyid val;
 	struct sctp_association *asoc;
 
+	if (!sctp_auth_enable)
+		return -EACCES;
+
 	if (optlen != sizeof(struct sctp_authkeyid))
 		return -EINVAL;
 	if (copy_from_user(&val, optval, optlen))
···
 {
 	struct sctp_authkeyid val;
 	struct sctp_association *asoc;
+
+	if (!sctp_auth_enable)
+		return -EACCES;
 
 	if (optlen != sizeof(struct sctp_authkeyid))
 		return -EINVAL;
···
 static int sctp_getsockopt_hmac_ident(struct sock *sk, int len,
 				    char __user *optval, int __user *optlen)
 {
+	struct sctp_hmacalgo  __user *p = (void __user *)optval;
 	struct sctp_hmac_algo_param *hmacs;
-	__u16 param_len;
+	__u16 data_len = 0;
+	u32 num_idents;
+
+	if (!sctp_auth_enable)
+		return -EACCES;
 
 	hmacs = sctp_sk(sk)->ep->auth_hmacs_list;
-	param_len = ntohs(hmacs->param_hdr.length);
+	data_len = ntohs(hmacs->param_hdr.length) - sizeof(sctp_paramhdr_t);
 
-	if (len < param_len)
+	if (len < sizeof(struct sctp_hmacalgo) + data_len)
 		return -EINVAL;
+
+	len = sizeof(struct sctp_hmacalgo) + data_len;
+	num_idents = data_len / sizeof(u16);
+
 	if (put_user(len, optlen))
 		return -EFAULT;
-	if (copy_to_user(optval, hmacs->hmac_ids, len))
+	if (put_user(num_idents, &p->shmac_num_idents))
 		return -EFAULT;
-
+	if (copy_to_user(p->shmac_idents, hmacs->hmac_ids, data_len))
+		return -EFAULT;
 	return 0;
 }
 
···
 {
 	struct sctp_authkeyid val;
 	struct sctp_association *asoc;
+
+	if (!sctp_auth_enable)
+		return -EACCES;
 
 	if (len < sizeof(struct sctp_authkeyid))
 		return -EINVAL;
···
 	else
 		val.scact_keynumber = sctp_sk(sk)->ep->active_key_id;
 
+	len = sizeof(struct sctp_authkeyid);
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+
 	return 0;
 }
 
···
 	struct sctp_authchunks val;
 	struct sctp_association *asoc;
 	struct sctp_chunks_param *ch;
-	u32    num_chunks;
+	u32    num_chunks = 0;
 	char __user *to;
 
-	if (len <= sizeof(struct sctp_authchunks))
+	if (!sctp_auth_enable)
+		return -EACCES;
+
+	if (len < sizeof(struct sctp_authchunks))
 		return -EINVAL;
 
-	if (copy_from_user(&val, p, sizeof(struct sctp_authchunks)))
+	if (copy_from_user(&val, optval, sizeof(struct sctp_authchunks)))
 		return -EFAULT;
 
 	to = p->gauth_chunks;
···
 		return -EINVAL;
 
 	ch = asoc->peer.peer_chunks;
+	if (!ch)
+		goto num;
 
 	/* See if the user provided enough room for all the data */
 	num_chunks = ntohs(ch->param_hdr.length) - sizeof(sctp_paramhdr_t);
 	if (len < num_chunks)
 		return -EINVAL;
 
-	len = num_chunks;
-	if (put_user(len, optlen))
+	if (copy_to_user(to, ch->chunks, num_chunks))
 		return -EFAULT;
+num:
+	len = sizeof(struct sctp_authchunks) + num_chunks;
+	if (put_user(len, optlen)) return -EFAULT;
 	if (put_user(num_chunks, &p->gauth_number_of_chunks))
 		return -EFAULT;
-	if (copy_to_user(to, ch->chunks, len))
-		return -EFAULT;
-
 	return 0;
 }
 
···
 	struct sctp_authchunks val;
 	struct sctp_association *asoc;
 	struct sctp_chunks_param *ch;
-	u32    num_chunks;
+	u32    num_chunks = 0;
 	char __user *to;
 
-	if (len <= sizeof(struct sctp_authchunks))
+	if (!sctp_auth_enable)
+		return -EACCES;
+
+	if (len < sizeof(struct sctp_authchunks))
 		return -EINVAL;
 
-	if (copy_from_user(&val, p, sizeof(struct sctp_authchunks)))
+	if (copy_from_user(&val, optval, sizeof(struct sctp_authchunks)))
 		return -EFAULT;
 
 	to = p->gauth_chunks;
···
 	else
 		ch = sctp_sk(sk)->ep->auth_chunk_list;
 
+	if (!ch)
+		goto num;
+
 	num_chunks = ntohs(ch->param_hdr.length) - sizeof(sctp_paramhdr_t);
-	if (len < num_chunks)
+	if (len < sizeof(struct sctp_authchunks) + num_chunks)
 		return -EINVAL;
 
-	len = num_chunks;
+	if (copy_to_user(to, ch->chunks, num_chunks))
+		return -EFAULT;
+num:
+	len = sizeof(struct sctp_authchunks) + num_chunks;
 	if (put_user(len, optlen))
 		return -EFAULT;
 	if (put_user(num_chunks, &p->gauth_number_of_chunks))
-		return -EFAULT;
-	if (copy_to_user(to, ch->chunks, len))
 		return -EFAULT;
 
 	return 0;