21 Oct
2015
21 Oct
'15
3:15 p.m.
On 21 Oct 2015, at 14:09, Daniel-Constantin Mierla
<miconda(a)gmail.com> wrote:
Hello,
checking the IP in the Via headers can be done in config file using a while loop:
$var(i) = 0;
while($(hdr(Via)[$var(i)])!=$null) {
# use transformations to extract the IP in $(hdr(Via)[$var(i)]) and test it against
$Ri
...
$var(i) = $var(i) + 1;
}
Also, checking the max-breadth should be possible in config file -- iirc, Olle played
with it at one of the SIPit events I attended, maybe he can add more details here. I
haven't read the RFC 5393 to be able to provide an example here.
I have a
kind-of working solution in script, that I used in the Dangerous Demos at kamailio world.
If someone wants to add a module to simplify the config, he/she is welcome to do it.
:-)
I think it needs to have hooks into tm.
/O
Cheers,
Daniel
On 21/10/15 10:35, Guillaume wrote:
Hi guys,
What do you think about the RFC 5393 on loop detection and amplification attack
protection?
The RFC is short and still a proposed standard but don't you think it could be useful
to prevent loop and amplification attack? Because even if the max-forward field reduces
the loop to ~70 hosts (in most cases) with some techniques we could fork the message up to
2^70 messages (as described in the RFC) to crash the servers.
Basically the server has to do 2 things:
* check if it is not already in the via of the message
* the previous check is not enough as a B2BUA could have replace the via headers, so the
RFC introduces a new field called max-breadth to limit the forking.
I have not seen a lot of implementation of this RFC on the free SIP software and I think
it could be a good way to improve kamailio making a module for it (the easier way to
implement this feature I think).
In fact I'm in a research internship about VoIP security and I have time to develop
such a module for kamailio if you think it's a good idea (I'm looking for some
security improvements in free software solutions so if you have other idea don't
hesitate to tell me).
Cheers,
Tetram
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--
Daniel-Constantin Mierla
http://twitter.com/#!/miconda <http://twitter.com/#!/miconda> -
http://www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda>
Book: SIP Routing With Kamailio - http://www.asipto.com <http://www.asipto.com/>