[PATCH net] sctp: validate embedded INIT chunk and address list lengths in cookie

sctp_unpack_cookie() only checked that the embedded INIT chunk length
did not exceed the remaining cookie payload, but did not ensure that the
INIT chunk is large enough to contain a complete INIT header.

A malformed COOKIE_ECHO can therefore carry a truncated INIT chunk whose
length field is smaller than sizeof(struct sctp_init_chunk).  Later,
sctp_process_init() accesses INIT parameters unconditionally, which may
lead to out-of-bounds reads.

In addition, raw_addr_list_len is not fully validated against the
remaining cookie payload. When cookie authentication is disabled, an
attacker can supply an oversized raw_addr_list_len and cause
sctp_raw_to_bind_addrs() to read beyond the end of the cookie. The
address parser also lacks sufficient bounds checks for parameter headers
and lengths, allowing malformed address parameters to trigger
out-of-bounds reads.

Fix this by:

- requiring the embedded INIT chunk length to be at least sizeof(struct
  sctp_init_chunk);
- validating that the INIT chunk and raw address list together fit
  within the cookie payload;
- verifying sufficient data exists for each address parameter header and
  payload before parsing it.

Note that sctp_verify_init() must be called after sctp_unpack_cookie()
and before sctp_process_init() when cookie authentication is disabled.
This will be addressed in a separate patch.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Sashiko <[email protected]>
Signed-off-by: Xin Long <[email protected]>
---
 net/sctp/bind_addr.c     | 11 ++++++++++-
 net/sctp/sm_make_chunk.c |  9 +++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index 75e3e61d494e..31737f144c7f 100644
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c
@@ -275,6 +275,16 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
 		param = (struct sctp_paramhdr *)raw_addr_list;
 		rawaddr = (union sctp_addr_param *)raw_addr_list;
 
+		if (addrs_len < sizeof(*param)) {
+			retval = -EINVAL;
+			goto out_err;
+		}
+		len = ntohs(param->length);
+		if (addrs_len < len) {
+			retval = -EINVAL;
+			goto out_err;
+		}
+
 		af = sctp_get_af_specific(param_type2af(param->type));
 		if (unlikely(!af) ||
 		    !af->from_addr_param(&addr, rawaddr, htons(port), 0)) {
@@ -291,7 +301,6 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
 			goto out_err;
 
 next:
-		len = ntohs(param->length);
 		addrs_len -= len;
 		raw_addr_list += len;
 	}
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 85264862fb6b..1741a9f33d8c 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1731,8 +1731,8 @@ struct sctp_association *sctp_unpack_cookie(
 	struct sk_buff *skb = chunk->skb;
 	struct sctp_cookie *bear_cookie;
 	struct sctp_chunkhdr *ch;
+	unsigned int len, chlen;
 	enum sctp_scope scope;
-	unsigned int len;
 	ktime_t kt;
 
 	/* Header size is static data prior to the actual cookie, including
@@ -1761,7 +1761,12 @@ struct sctp_association *sctp_unpack_cookie(
 	bear_cookie = &cookie->c;
 
 	ch = (struct sctp_chunkhdr *)(bear_cookie + 1);
-	if (ntohs(ch->length) > len - fixed_size)
+	chlen = ntohs(ch->length);
+	if (chlen < sizeof(struct sctp_init_chunk))
+		goto malformed;
+	if (chlen > len - fixed_size)
+		goto malformed;
+	if (bear_cookie->raw_addr_list_len > len - fixed_size - chlen)
 		goto malformed;
 
 	/* Verify the cookie's MAC, if cookie authentication is enabled. */
-- 
2.47.1