[SR-Users] Mutual TLS with Skype for Business 2015
Frank Carmickle
frank at carmickle.com
Wed Oct 25 17:00:35 CEST 2017
> On Oct 25, 2017, at 9:27 AM, Francisco Valentin Vinagrero <francisco.valentin.vinagrero at cern.ch> wrote:
>
> Hello Daniel,
>
> Thanks for your answer.
>
> I don’t see much in the debug logs. Except the SSL verification error, the rest looks like the normal SSL handshake and the TCP connection setup:
>
> DEBUG: <core> [io_wait.h:598]: io_watch_del(): DBG: io_watch_del (0xa7edc0, 8, -1, 0x10) fd_no=2 called
> DEBUG: <core> [tcp_read.c:1490]: release_tcpconn(): releasing con 0x7f9191b1ade0, state -2, fd=8, id=8 ([<SfB IP1>]:56267 -> [<SfB IP1>]:5061)
> DEBUG: <core> [tcp_read.c:1491]: release_tcpconn(): extra_data 0x7f9191b39318
> DEBUG: <core> [tcp_main.c:3243]: handle_tcp_child(): reader response= 7f9191b1ade0, -2 from 0
> DEBUG: tls [tls_server.c:663]: tls_h_close(): Closing SSL connection 0x7f9191b39318
> DEBUG: <core> [ip_addr.c:229]: print_ip(): tcpconn_new: new tcp connection: <SfB IP1>
> DEBUG: <core> [tcp_main.c:985]: tcpconn_new(): on port 56269, type 3
> DEBUG: <core> [tcp_main.c:1295]: tcpconn_add(): hashes: 3769:3996:3198, 9
> DEBUG: <core> [io_wait.h:376]: io_watch_add(): DBG: io_watch_add(0xa25be0, 30, 2, 0x7f9191b1ade0), fd_no=20
> DEBUG: <core> [io_wait.h:598]: io_watch_del(): DBG: io_watch_del (0xa25be0, 30, -1, 0x0) fd_no=21 called
> DEBUG: <core> [tcp_main.c:4131]: handle_tcpconn_ev(): sending to child, events 1
> DEBUG: <core> [tcp_main.c:3813]: send2child(): selected tcp worker 1 12(4808) for activity on [tls:<LOCAL IP>:5061], 0x7f9191b1ade0
> DEBUG: <core> [tcp_read.c:1566]: handle_io(): received n=8 con=0x7f9191b1ade0, fd=8
> DEBUG: tls [tls_server.c:197]: tls_complete_init(): completing tls connection initialization
> DEBUG: tls [tls_server.c:226]: tls_complete_init(): Using initial TLS domain TLSs<default> (dom 0x7f9191861e98 ctx 0x7f9191887a10 sn [])
> DEBUG: tls [tls_domain.c:703]: sr_ssl_ctx_info_callback(): SSL handshake started
> DEBUG: <core> [tcp_main.c:2430]: tcpconn_do_send(): sending...
> DEBUG: <core> [tcp_main.c:2464]: tcpconn_do_send(): after real write: c= 0x7f9191b1ade0 n=6692 fd=8
> DEBUG: <core> [tcp_main.c:2465]: tcpconn_do_send(): buf=#012#026#003#003
> DEBUG: <core> [io_wait.h:376]: io_watch_add(): DBG: io_watch_add(0xa7edc0, 8, 2, 0x7f9191b1ade0), fd_no=1
> DEBUG: <core> [tcp_main.c:2430]: tcpconn_do_send(): sending...
> DEBUG: <core> [tcp_main.c:2464]: tcpconn_do_send(): after real write: c= 0x7f9191b1ade0 n=7 fd=8
> DEBUG: <core> [tcp_main.c:2465]: tcpconn_do_send(): buf=#012#025#003#003
> ERROR: tls [tls_util.h:42]: tls_err_ret(): TLS accept:error:14089086:SSL routines:ssl3_get_client_certificate:certificate verify failed
> ERROR: <core> [tcp_read.c:1330]: tcp_read_req(): ERROR: tcp_read_req: error reading
>
> Maybe you can see some hint there that I don’t see?
>
> Cheers, Francisco.
>
>
> From: Daniel-Constantin Mierla [mailto:miconda at gmail.com <mailto:miconda at gmail.com>]
> Sent: Wednesday, October 25, 2017 14:50
> To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org <mailto:sr-users at lists.kamailio.org>>; Francisco Valentin Vinagrero <francisco.valentin.vinagrero at cern.ch <mailto:francisco.valentin.vinagrero at cern.ch>>
> Subject: Re: [SR-Users] Mutual TLS with Skype for Business 2015
>
> Hello,
>
>
> On 25.10.17 11:32, Francisco Valentin Vinagrero wrote:
> Hello,
>
> I’m trying to replace two old Audiocodes gateways (used to interconnect our Skype for Business infrastructure to the PSTN) with a new Kamailio cluster.
>
> I am having some trouble to get the TLS mutual authentication working with Kamailio. For the moment, I’m just trying to receive the incoming OPTIONS from SfB, but I get all the time certificate verification errors:
>
> ERROR: tls [tls_util.h:42]: tls_err_ret(): TLS accept:error:14089086:SSL routines:ssl3_get_client_certificate:certificate verify failed
> ERROR: <core> [tcp_read.c:1330]: tcp_read_req(): ERROR: tcp_read_req: error reading
>
> My tls.cfg is quite simple, with the same config for client and server (and one single listen=tls:<my IP>:5061 in the Kamailio.cfg file)
>
> [server:default]
> method = TLSv1+
> verify_certificate = yes
> require_certificate = yes
> private_key = /usr/local/etc/kamailio/tls/key_gw_sfb.pem
> certificate = /usr/local/etc/kamailio/tls/cert_gw_sfb.pem # => This certificate’s Subject is the DNS alias for the cluster, with all the kamailios in the cluster as Subject Alternative Names
> ca_list = /usr/local/etc/kamailio/tls/myca_and_sfbca.pem # => Kamailio and Skype for Business are signed by different CAs, so here I concatenated all intermediate and root CAs
>
> [client:default]
> method = TLSv1+
> verify_certificate = yes
> require_certificate = yes
> private_key = /usr/local/etc/kamailio/tls/key_gw_sfb.pem
> certificate = /usr/local/etc/kamailio/tls/cert_gw_sfb.pem
> ca_list = /usr/local/etc/kamailio/tls/myca_and_sfbca.pem
>
>
> When I run Kamailio, I can see incoming OPTIONS from Microsoft Exchange Unified Messaging (UM), whose certificate I verify without any issues. UM presents a certificate issued for a single machine, so no Subject Alternative Names (SANs) are involved.
You’ve verified this by using s_client? Getting a TLS session established with s_client first will likely shed light on a possible misconfiguration.
--FC
>
> The problem comes with the TLS handshake for the Skype Mediation pool. They have a certificate with Subject = DNS alias and all the physical machines that are behind the alias appear listed as Subject Alternative Names (SANs) in the certificate.
>
> As the only difference between UM and Skype’s Mediation is the certificate’s Subject, I think I am missing something on my configuration to validate the SANs instead of the subject. Is the TLS module doing any reverse DNS lookup to verify this?
>
> afaik, the certificate validation is done by the libssl, kamailio is not doing much in this respect and no dns query inside kamailio tls module. Maybe some parameters must be set when asking for validation.
>
> If you run with debug=3 inside kamailio.cfg, do you see any log messages that can help in identifying why it fails?
>
> Cheers,
> Daniel
>
> --
> Daniel-Constantin Mierla
> www.twitter.com/miconda <http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda>
> Kamailio Advanced Training, Nov 13-15, 2017, in Berlin - www.asipto.com <http://www.asipto.com/>
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