Hi everybody,<br>
<br>
I create a separate thread for the whole &quot;tls improvement, let's create
a module, lets see what to do with it&quot; because for me it was getting a
bit messier. Too many threads all talking about the same :)<br>
<br>
The TLS bussiness, we agree, is ugly and there is no one-fits-all
solution, so we must try to be flexible, even if it means more
development.<br>
Breaking it down, one more summary:<br>
<br>
1) TLS transport layer authentication<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Allow for various levels of verification and peer certificate
requirement. That is, request a cert from the peer or not, what to do
if the certificate provided by the peer is not signed by one of our CAs
(or if there is no peer cert at all), how the verification should be
done (just check against our trusted CAs or do some DNS resolution for
the provided Subject/CN on the ip we receive the connection from), etc.<br>
<br>
2) Lifting the TLS authentication to the SIP layer for SIP
authentication and authorization, according to &quot;whatever&quot; local policy<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
I think here a tls_tools module is what we need. Let's think on what
functions are needed to cover most needs. Proposals up to now include
functions such as: tls_check_from/to( &quot;SubjectName&quot;/&quot;CN&quot;),
tls_is_peer_cert_present(), tls_is_peer_cert_valid(),
tls_is_peer_domain_trusted() as in white/black list, etc.<br>
<br>
3) Incoming requests<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3.1) Single domain<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
This does not present much of a problem. Just present whatever
certificate the proxy is serving. Use the tls_tools module to further
authenticate and authorize the requeset.<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3.2) Multi-domain<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
This present a lot of problems, but there are solutions:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
3.2.a) Use a different ip:port per domain ... good enough if the
domains served are not changing often.<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
3.2.b) Present the host certificate, not one per domain ... usable as a
fall-back scenario if everything else fails.<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
3.2.c) Use TLS Extensions, so the requesting proxy notifies the
receiving proxy of the domain it is requesting. I just found some guys
(i think an initial project from stanford, i don't know now) that
implemented the TLS Servername Extension
(<a href="http://www.edelweb.fr/EdelKey/">http://www.edelweb.fr/EdelKey/</a>). I am still waiting for more answers
on the ssl-users mailing list, hopefully it is already included in the
core, otherwise this solution would mean having to compile openssl
locally :(<br>
<br>
4) Outgoing requests<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4.1) Single domain<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Again, not much of a problem. <br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4.2) Multiple domain<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Solution here is simpler. Provided that the domains are internally
setup, select the desired one when forwarding the request (either
automatically or via some function in tls_tools module). TLS domains
can currently only be set up statically in the config file, thus some
dynamic mechanism to create new ones has to be found (database, serctl?
).<br>
<br>
5) Out-of-the-box setup<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; That
is, ser should allow to work using some very simplistic TLS form just
by compiling it with TLS=1 and turning the tls_disabled=0 parameter. In
this scenario, TLS could work using anonymous ciphers (no need for
certificates) and would accept any incoming request (no verification of
certs against CAs, or come with a generic root CA, but that would be
more complex). In this mode, a huuge warning should be issued.<br>
<br>
Let's try to focus on specifics, so we can get this working as soon as possible. <br>
<br>
Regards,<br>
<br>
Cesc<br>
<br>
<br>
<br>
<br>
<br>