On 06/30/2012 08:17 PM, Dan Carpenter wrote:
> In 555d3d5d "SCTP: Fix chunk acceptance when no authenticated chunks
> were listed.", we added a check for if (param->param_hdr.length == 0).
> Shouldn't that check be a check for if
> (param->param_hdr.length < sizeos(sizeof(sctp_paramhdr_t)))? Otherwise,
> when we do the substraction on the next line we would unintentionally
> end up with a high positive number.
>
> I had a similar question about sctp_auth_ep_add_chunkid():
>
> net/sctp/auth.c
> 770 /* Check if we can add this chunk to the array */
> 771 param_len = ntohs(p->param_hdr.length);
> 772 nchunks = param_len - sizeof(sctp_paramhdr_t);
> 773 if (nchunks == SCTP_NUM_CHUNK_TYPES)
> 774 return -EINVAL;
> 775
> 776 p->chunks[nchunks] = chunk_id;
>
> If param_len is less than sizeof(sctp_paramhdr_t) we could write past
> the end of the array. There are a couple other places with this same
> subtraction as well.
This will not happen because that p which means ep->auth_chunk_list
is maintained by the endpoint itself, and the default value is
sizeof(sctp_paramhdr_t) or sizeof(sctp_paramhdr_t) + 2.
Instead, I found that if user enable AUTH after the endpoint is
created, set the AUTH chunk may cause panic, because the
ep->auth_chunk_list is NULL.
I think we should introduce a help function to check whether the
AUTH is enabled instead only check sctp_auth_enable, may like:
bool sctp_auth_ep_enabled(struct sctp_endpoint *ep)
{
if (!sctp_auth_enable)
return false;
if (!ep->auth_chunk_list || !ep->auth_hmacs_list)
return false;
return true;
}
Regards
Yongjun Wei
>
> regards,
> dan carpenter
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