7 Oct
2007
7 Oct
'07
10:53 p.m.
Robert Dyck wrote:
I had already tried configuring the UA with the
address of one of the servers
( both IP and domain name ) as well as altering the openser config to force
the address. The peculiar thing there is that the registrar does not
challenge or even respond at all. It would seem that it ignores REGISTER
requests that do not have callcentric.com as the domain name and realm.
Yes, that seems to be the case.
The UA can register with this provider without difficulty when the UA is
configured to use STUN and no outgoing proxy. The UA does not do a second DNS
lookup. It simply uses the same address for both requests.
Ok, the credentials seem to be fine.
When the UA receives the challenge does it not use the
received nonce to
encrypt its credentials? I have to admit my knowledge of that subject is
shakey. And would this not have to be delivered to the same server that sent
the nonce?
You are right, although the nonce is included in the response to a
challenge, the registrar obviously has to make sure that it matches the
one sent in the challenge. Otherwise replay attacks would be easily
possible.
So the problem boils down to the fact that your SIP provider is using
round-robin DNS instead of NAPTR/SRV. This causes your openser to send
the requests to different hosts.
The trace you sent me indicates that you're using a local DNS cache
server. One option would be to configure this server to not to do
round-robin for "callcentric.com". E.g. with BIND this can be achieved
by adding
options {
rrset-order {
name "callcentric.com" order fixed;
};
}
The callcentric.com DNS record has a TTL of 30 minutes, so the target IP
address could potentially change every 30 minutes.
Another option would be to hard-code the target IP address for REGISTER
requests in the openser config, like
if (is_method("REGISTER") && ($rd == "callcentric.com"))
{
t_relay("udp:204.11.192.22:5060");
}
which has the disadvantage that an IP change for callcentric.com would
disable the callcentric registration service.
/Christian
On Saturday 06 October 2007, you wrote:
Robert Dyck wrote:
I am more familiar with ethereal. I hope that is
OK. Also I have not
edited the dumps so I am sending them privately. Attached are brief and
detailed dumps from ethereal.
Your SIP provider is using DNS round-robin which is
why openser is
forwarding the requests to different IP addresses. This is the first
provider I see that is doing DNS RR, this is rather unusual and not what
is described by the SIP RFCs.
Nevertheless, I still believe that your problem is related to wrong
credentials. Both provider registrars should accept your REGISTER with
Proxy-Auth header.
You could also configure your SIP client with 204.11.192.22 instead of
the provider's hostname, this will disable DNS RR and let openser
forward the request always to the same host.
/Christian
> On Saturday 06 October 2007, you wrote:
>> Robert Dyck wrote:
>>> The second registrar does not send an error code, it simply issues its
>>> own challenge. Openser is definitely alternating between registrars. It
>>> does not send the credentials to the same registrar that requested
>>> them.
>>>
>>> I could send a trace if it would be helpful.
>> Yes, that would be helpful, I'd also like to have a look at the DNS
>> traffic. Can you do
>>
>> tcpdump -i any -s 1500 -w /tmp/trace.pcap
>>
>> /Christian