[SR-Users] Retrieving cert details from tls peer

[Daniel-Constantin Mierla]

Hello,

On 03.07.20 11:12, Mark Boyce wrote:
> Hi Daniel
>
> Ah, that’s the bit I misunderstood. I thought that require_certificate
> would trigger mutual auth / mTLS rather than enforcing its presence.

well, the server indicates it wants to see client certificate during the
handshake, but it has no control in forcing the client to do so. From
Kamailio point of view, all this is done by underlying libssl used by
tls module. The result after handshake, based on the error message, is
that client didn't present any certificate.

Typically the clients do not present their certificate by default, there
has to be some configuration for that. From my experience, the
hardphones have certificates only for provisioning/management APIs.

For SIP, there has an option of uploading the client side certificate,
because it has to match somehow the SIP user and SIP service to be able
to do proper mutual TLS authentication.

Cheers,
Daniel

>
> No sign of a setting on the Yealink to send it’s certificate. Will go
> unpack a Cisco and see what that offers.
>
> Thanks
> Mark, 
>
>> On 3 Jul 2020, at 09:09, Daniel-Constantin Mierla <miconda at gmail.com
>> <mailto:miconda at gmail.com>> wrote:
>>
>> Hello,
>>
>> the client has to be configured to present a certificate, and it
>> doesn't do it based on kamailio log message:
>>
>> INFO: tls [tls_server.c:445]: tls_accept(): tls_accept: client did
>> not present a certificate
>>
>> Check the phone config to see if you can set such option. Kamailio
>> can just see if a certificate is sent and if not reject the
>> connection, if you have require_certificate = yes in the server
>> profile of tls.cfg
>>
>> You can eventually test with 'openssl s_client ...' to see details of
>> client side certs in kamailio -- iirc, it has the options to specify
>> client side certificate with -cert ... -key ...
>>
>> Cheers,
>> Daniel
>>
>> On 03.07.20 09:52, Mark Boyce wrote:
>>> Hi Daniel
>>>
>>> I’m testing with a Yealink T57W. It comes with a factory install
>>> certificate which will probably fail validation as the common name
>>> is the MAC. Â 
>>>
>>> I'm not trying validate the client device’s certificate just get it
>>> to offer what it has so I can check the details.
>>>
>>> Thanks
>>> Mark
>>>
>>>> On 3 Jul 2020, at 08:38, Daniel-Constantin Mierla
>>>> <miconda at gmail.com <mailto:miconda at gmail.com>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> what is the SIP client app you used? Is it configured to use its
>>>> own tls certificate when connecting to the SIP server?
>>>>
>>>> Cheers,
>>>> Daniel
>>>>
>>>> On 02.07.20 18:51, Mark Boyce wrote:
>>>>> Hi all
>>>>>
>>>>> Been trying to grab the TLS cert details from incoming
>>>>> connections, but failing :-(
>>>>>
>>>>> So with lines just before AUTH is called like this;
>>>>>
>>>>> Â  Â  Â  Â  if (proto == TLS) {
>>>>>         xlog("L_INFO", "TLSDUMP $ci  peer_subject        :
>>>>> $tls_peer_subject\n");
>>>>>
>>>>> Gets met with a log line line this;
>>>>>
>>>>> INFO: tls [tls_server.c:431]: tls_accept(): tls_accept: new
>>>>> connection from 1.2.3.4:11797 using TLSv1.2
>>>>> ECDHE-RSA-AES256-GCM-SHA384 256
>>>>> INFO: tls [tls_server.c:434]: tls_accept(): tls_accept: local
>>>>> socket: 5.6.7.8:5061
>>>>> INFO: tls [tls_server.c:445]: tls_accept(): tls_accept: client did
>>>>> not present a certificate
>>>>> ...
>>>>> INFO: tls [tls_select.c:168]: get_cert(): Unable to retrieve peer
>>>>> TLS certificate from SSL structure
>>>>>
>>>>> This is with verify_certificate and require_certificate set to no
>>>>> in tls.cfg
>>>>>
>>>>> If I try and set the following in tls.cfg
>>>>>
>>>>> [server:default]
>>>>> method = TLSv1.2+
>>>>> verify_certificate = no
>>>>> require_certificate = yes
>>>>>
>>>>> I see in the logs;
>>>>>
>>>>> INFO: tls [tls_domain.c:303]: ksr_tls_fill_missing():
>>>>> TLSs<default>: tls_method=22
>>>>> INFO: tls [tls_domain.c:315]: ksr_tls_fill_missing():
>>>>> TLSs<default>: certificate='/etc/kamailio/tls-certs/cert.pem'
>>>>> INFO: tls [tls_domain.c:322]: ksr_tls_fill_missing():
>>>>> TLSs<default>: ca_list='(null)'
>>>>> INFO: tls [tls_domain.c:329]: ksr_tls_fill_missing():
>>>>> TLSs<default>: crl='(null)'
>>>>> INFO: tls [tls_domain.c:333]: ksr_tls_fill_missing():
>>>>> TLSs<default>: *require_certificate=1*
>>>>> INFO: tls [tls_domain.c:340]: ksr_tls_fill_missing():
>>>>> TLSs<default>: cipher_list='(null)'
>>>>> INFO: tls [tls_domain.c:347]: ksr_tls_fill_missing():
>>>>> TLSs<default>: private_key='/etc/kamailio/tls-certs/privkey.pem'
>>>>> INFO: tls [tls_domain.c:351]: ksr_tls_fill_missing():
>>>>> TLSs<default>: *verify_certificate=0*
>>>>> INFO: tls [tls_domain.c:354]: ksr_tls_fill_missing():
>>>>> TLSs<default>: verify_depth=9
>>>>> NOTICE: tls [tls_domain.c:1095]: ksr_tls_fix_domain(): registered
>>>>> server_name callback handler for socket [:0],
>>>>> server_name='<default>' ...
>>>>> INFO: tls [tls_domain.c:692]: set_verification():
>>>>> TLSs<default>:*Client MUST present valid certificate*
>>>>> INFO: tls [tls_domain.c:303]: ksr_tls_fill_missing():
>>>>> TLSc<default>: tls_method=20
>>>>> INFO: tls [tls_domain.c:315]: ksr_tls_fill_missing():
>>>>> TLSc<default>: certificate='(null)'
>>>>> INFO: tls [tls_domain.c:322]: ksr_tls_fill_missing():
>>>>> TLSc<default>: ca_list='(null)'
>>>>> INFO: tls [tls_domain.c:329]: ksr_tls_fill_missing():
>>>>> TLSc<default>: crl='(null)'
>>>>> INFO: tls [tls_domain.c:333]: ksr_tls_fill_missing():
>>>>> TLSc<default>: *require_certificate=1*
>>>>> INFO: tls [tls_domain.c:340]: ksr_tls_fill_missing():
>>>>> TLSc<default>: cipher_list='(null)'
>>>>> INFO: tls [tls_domain.c:347]: ksr_tls_fill_missing():
>>>>> TLSc<default>: private_key='(null)'
>>>>> INFO: tls [tls_domain.c:351]: ksr_tls_fill_missing():
>>>>> TLSc<default>: *verify_certificate=1*
>>>>> INFO: tls [tls_domain.c:354]: ksr_tls_fill_missing():
>>>>> TLSc<default>: verify_depth=9
>>>>> INFO: tls [tls_domain.c:692]: set_verification(): TLSc<default>:
>>>>> *Server MUST present valid certificate*
>>>>> ...
>>>>> ERROR: tls [tls_util.h:42]: tls_err_ret(): TLS
>>>>> accept:error:1417C086:SSL
>>>>> routines:tls_process_client_certificate:certificate verify failed
>>>>>
>>>>> Which looks like verification is being enabled when I add require?
>>>>>
>>>>>
>>>>>
>>>>> Would someone be kind enough to point out what I am missing
>>>>> please? (Assuming it’s not a bug :-)
>>>>>
>>>>>
>
-- 
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Funding: https://www.paypal.me/dcmierla

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