[SR-Users] Implementation of RFC 5393

[Guillaume]

But why don't you implement this feature after your demo at kamailio world? Do you think it's useless at the end?

And how your script was working with kamailio ?


Thanks for your response


Guillaume

From: oej at edvina.net
Date: Wed, 21 Oct 2015 14:15:43 +0200
To: miconda at gmail.com
CC: sr-users at lists.sip-router.org
Subject: Re: [SR-Users] Implementation of RFC 5393


On 21 Oct 2015, at 14:09, Daniel-Constantin Mierla <miconda at 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,DanielOn 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://www.linkedin.com/in/miconda
Book: SIP Routing With Kamailio - http://www.asipto.com

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