tree 3e8a4339e57c06791329c3bb98c9d0d3c564b72a
parent 9b82a588cd7ec1fb4d8016020d8022f962d20df9
author Christopher Faulet <cfaulet@haproxy.com> 1501062601 +0200
committer Willy Tarreau <w@1wt.eu> 1501091013 +0200
encoding latin1

BUG/MINOR: ssl: Fix check against SNI during server certificate verification

This patch fixes the commit 2ab8867 ("MINOR: ssl: compare server certificate
names to the SNI on outgoing connections")

When we check the certificate sent by a server, in the verify callback, we get
the SNI from the session (SSL_SESSION object). In OpenSSL, tlsext_hostname value
for this session is copied from the ssl connection (SSL object). But the copy is
done only if the "server_name" extension is found in the server hello
message. This means the server has found a certificate matching the client's
SNI.

When the server returns a default certificate not matching the client's SNI, it
doesn't set any "server_name" extension in the server hello message. So no SNI
is set on the SSL session and SSL_SESSION_get0_hostname always returns NULL.

To fix the problemn, we get the SNI directly from the SSL connection. It is
always defined with the value set by the client.

If the commit 2ab8867 is backported in 1.7 and/or 1.6, this one must be
backported too.

Note: it's worth mentionning that by making the SNI check work, we
      introduce another problem by which failed SNI checks can cause
      long connection retries on the server, and in certain cases the
      SNI value used comes from the client. So this patch series must
      not be backported until this issue is resolved.