Don't report an error for a non-multiple-of-4 chunk length.

To quote RFC 4960:

Chunk Length: 16 bits (unsigned integer)

      This value represents the size of the chunk in bytes, including
      the Chunk Type, Chunk Flags, Chunk Length, and Chunk Value fields.
      Therefore, if the Chunk Value field is zero-length, the Length
      field will be set to 4.  *The Chunk Length field does not count any
      chunk padding.*

      Chunks (including Type, Length, and Value fields) are padded out
      by the sender with all zero bytes to be a multiple of 4 bytes
      long.  This padding MUST NOT be more than 3 bytes in total.  The
      Chunk Length value does not include terminating padding of the
      chunk.  However, it does include padding of any variable-length
      parameter except the last parameter in the chunk.  The receiver
      MUST ignore the padding.

      Note: A robust implementation should accept the chunk whether or
      not the final padding has been included in the Chunk Length.

so the the chunk is *not* required to include the length of the final
padding in the chunk, although any padding *between* variable-length
parameters in the chunk must be included in the length (obviously, as
it's part of the chunk data).

Change-Id: I99d64fdd907c41229aa9ad10a230fff4bcdfa5f4
Reviewed-on: https://code.wireshark.org/review/12664
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 0 insertions, 2 deletions

diff --git a/epan/dissectors/packet-sctp.c b/epan/dissectors/packet-sctp.c
index 293760c100..bd8afaec73 100644
--- a/epan/dissectors/packet-sctp.c
+++ b/epan/dissectors/packet-sctp.c
@@ -4320,8 +4320,6 @@ dissect_sctp_chunk(tvbuff_t *chunk_tvb,
   chunk_tree   = proto_tree_add_subtree_format(sctp_tree, chunk_tvb, CHUNK_HEADER_OFFSET, reported_length,
                     ett_sctp_chunk, &chunk_item, "%s chunk",
                     val_to_str_const(type, chunk_type_values, "RESERVED"));
-  if (reported_length % 4)
-    expert_add_info_format(pinfo, chunk_item, &ei_sctp_chunk_length_bad, "Chunk length is not padded to a multiple of 4 bytes (length=%d).", reported_length);
 
   if (tree) {
     /* then insert the chunk header components into the protocol tree */