[SR-Users] Retrieving cert details from tls peer

Mark Boyce mark at darkorigins.com
Tue Jul 7 09:26:12 CEST 2020 

Hi

That sounds hopeful.  Where I was vaguely going was being able to capture the certificate details at http provisioning, or first sip interaction.  This should then give a secure way to validate that individual device.

From my experience with Yealink devices; The older devices all come with a common device certificate.  Current generation also have an individual unique certificate.  The cutoff appears to be those devices which were factory shipped with firmware version v72

https://tinyurl.com/ybtfxvnj <https://tinyurl.com/ybtfxvnj>

"Using Security Certificates on Yealink IP Phones” 
It’s not completely clear but the Yealink security document says;

"If “Mutual TLS Authentication Required” is enabled on your server, the IP phone should send its certificate to the server as well”

However even though the doc mentions SIPs and HTTPS all examples talk about HTTPS and provisioning.

Mark

> On 7 Jul 2020, at 07:28, Daniel-Constantin Mierla <miconda at gmail.com> wrote:
> 
> Hello,
> 
> as said, from my experience if it is a preloaded certificate on the device, then it is mainly used for the https management interface.
> 
> However, searching the web about snom phones and ssl certificates, it seems that their latest models use the certificate even for sip:
> 
>   - https://service.snom.com/display/wiki/TLS+Support <https://service.snom.com/display/wiki/TLS+Support>
> I haven't tested it, but I plan to do it when I get a chance. I could not see anything in docs about uploading a new set of certs, so I would be interested to learn what sip hard phones allow that.
> Cheers,
> Daniel
> On 03.07.20 14:12, Mark Boyce wrote:
>> Hi
>> 
>> Looking at the libssl docs it looks like the require/verify setting triggers the client cert request to be sent. When set to ‘verify none' no request is sent.
>> 
>> Either way the Yealink seems to be ignoring the request.
>> 
>> As always, thanks for your assistance
>> 
>> Mark
>> 
>>> On 3 Jul 2020, at 11:38, Daniel-Constantin Mierla <miconda at gmail.com <mailto:miconda at gmail.com>> wrote:
>>> 
>>> 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.  
>>>>>> 
>>>>>> 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;
>>>>>>>> 
>>>>>>>>         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 <http://www.asipto.com/>
>>> www.twitter.com/miconda <http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda>
>>> Funding: https://www.paypal.me/dcmierla <https://www.paypal.me/dcmierla>
>> Best regards
>> Mark
>> -- 
>> Mark Boyce
>> Dark Origins Ltd
>> e: mark at darkorigins.com <mailto:mark at darkorigins.com>
>> 
>> 
> -- 
> Daniel-Constantin Mierla -- www.asipto.com <http://www.asipto.com/>
> www.twitter.com/miconda <http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda>
> Funding: https://www.paypal.me/dcmierla <https://www.paypal.me/dcmierla>
Mark
-- 
Mark Boyce
Dark Origins Ltd

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