On 08/25/2015 10:01 AM, Marcelo Ricardo Leitner wrote:
> On Tue, Aug 25, 2015 at 08:29:24PM +0800, Xin Long wrote:
>> in sctp_process_asconf(), we get address parameter from the beginning of
>> the addip params. but we never check if it's really there. if the addr
>> param is not there, it still can pass sctp_verify_asconf(), then to be
>> handled by sctp_process_asconf(), it will not be safe.
>>
>> so add a code in sctp_verify_asconf() to check the address parameter is in
>> the beginning, or return false to send abort.
>>
>> v1->v2:
>> * put the check behind the params' length verify.
>>
>> Signed-off-by: Xin Long <lucien....@gmail.com>
>> ---
>> net/sctp/sm_make_chunk.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
>> index 06320c8..89a4d1c 100644
>> --- a/net/sctp/sm_make_chunk.c
>> +++ b/net/sctp/sm_make_chunk.c
>> @@ -3166,6 +3166,13 @@ bool sctp_verify_asconf(const struct sctp_association
>> *asoc,
>> return false;
>> if (!addr_param_needed && addr_param_seen)
>> return false;
>> + if (addr_param_needed && addr_param_seen) {
>> + /* Ensure the address parameter is in the beginning */
>> + param.v = chunk->skb->data + sizeof(sctp_addiphdr_t);
>
> Using param.v before the loop made sense but after the loop, it will
> cause all packets that hits here to be reject due to the check below.
>
>> + if (param.p->type != SCTP_PARAM_IPV4_ADDRESS &&
>> + param.p->type != SCTP_PARAM_IPV6_ADDRESS)
>> + return false;
>> + }
>> if (param.v != chunk->chunk_end)
> this one -----^
>
> Maybe it's easier if you put this check inside the loop for each ipv4/6,
> and check if it is the first parameter or not by mimicing the way
> sctp_walk_params() finds the first chunk, it's just a pointer
> derreference and that was already checked and performed to reach there.
>
> (You can have some logic with addr_param_seen so you don't catch the
> multiple parameters in there.)
Exactly!
something like this:
SCTP_PARAM_IPV4_ADDRESS:
if (param.v == addip->addip_hdr.params)
addr_param_seen = true;
Thus making sure that the parameter as seen only when it's at the beginning...
Then later we can do things like:
SCTP_PARAM_IPV4_ADDRESS:
if (addr_param_seen) {
/* peer placed multiple address parameters into the same
* asconf. reject it.
*/
return false;
}
-vlad
>
> Marcelo
>
>> return false;
>>
>> --
>> 2.1.0
>>
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