[SR-Users] sip invite proxy-authorization

[Dave & Hazel]

Nope, I’m not calling a registered user. Actually, there are no registered users. The function of the Kamailio service in this case is to relay WebRTC calls to a conferencing bridge. The problem is that whoever set it up did so without considering the security implications. And, in fact, it was malevolent SIP traffic hitting the bridge that lead me to looking more closely at the Kamailio solution.

 

There appears to be some custom configuration around routing. I’m not sure if route(RELAY) on its own is meant to challenge for authorisation.

 

#!ifdef WITH_CONFERENCEBRIDGE

     if(is_method("INVITE") && (!route(FROMBRIDGE))) {

           # if new call from out there - 

           # - non-INVITE request are routed directly by Kamailio

           # - traffic from is routed also directy by Kamailio

           

           route(TOBRIDGE);

           exit;

     }

#!endif

 

#!ifdef WITH_CONFERENCEBRIDGE

# Send to bridge

route[TOBRIDGE] {

     $du = "sip:" + $sel(cfg_get.bridge.bindip) + ":"

                + $sel(cfg_get.bridge.bindport);

     route(RELAY);

     exit;

}

 

#!endif

 

As I short term solution to filter unwanted traffic, I’ve updated the configuration to only relay calls using a definitive DDI.

 

#!ifdef WITH_CONFERENCEBRIDGE

# Send to bridge

route[TOBRIDGE] {

 

     if($rU != "8835100xxxxx")

           return -1;

 

     $du = "sip:" + $sel(cfg_get.bridge.bindip) + ":"

                + $sel(cfg_get.bridge.bindport);

     route(RELAY);

     exit;

}

 

#!endif

 

Thanks guys for your help.

 

From: sr-users [mailto:sr-users-bounces at lists.kamailio.org] On Behalf Of David Villasmil
Sent: Saturday, January 20, 2018 1:06 AM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] sip invite proxy-authorization

 

Again, are you calling a local registeted user?

 

On Fri, Jan 19, 2018, 17:28 Dave & Hazel <dogbark at indigo.ie <mailto:dogbark at indigo.ie> > wrote:

Cheers Alex for your insight.

My problem still remains in that my invites are not being challenged even though AUTH is defined.

On 19 Jan 2018, at 15:57, Alex Balashov <abalashov at evaristesys.com <mailto:abalashov at evaristesys.com> > wrote:

Hi,

> On Fri, Jan 19, 2018 at 03:38:24PM -0000, Dave & Hazel wrote:
>
> preforming a SIP INVITE without first registering with the Kamailio
> service (SJ-Phone speak). I am dialling in remotely via NAT and my
> call is being relayed successfully.

Although many people are led to believe that there is some intrinsic
connection between registration and outbound calling by the way phone
UIs present these concepts, there is in fact no such connection
whatsoever.

Registration is an inbound concept, not an outbound concept. You can
make calls without being registered. You can make outbound calls using
different AAA mechanisms. Being registered in no way implies being able
to make outbound calls. They're just completely unrelated.

There is a common authentication mechanism used in both scenarios:
digest challenge authentication. As a practical matter, Kamailio sends a
407 proxy challenge for requests it is meant to relay (e.g. INVITEs) and
a 401 Unauthorized challenge for requests of which it is the logical
destination (e.g. REGISTER), and both draw on the same set of
authentication credentials and otherwise work the same way. The AUTH
route covers both of these cases.

-- Alex

--
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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