enhance tls-verify possibility

It should be nice to enhance tls-verify check possibilities against peer
cert during a pending TLS connection like :
- OCSP verification
- check any X509 extensions of the peer certificate
- delta CRL verification
- ...

This patch add a new "tls-export-cert" option which allow to get peer
certificate in PEM format and to store it in an openvpn temporary file.
Peer certificate is stored before tls-script execution and deleted after.
The name of the related temporary file is available under tls-verify
script by an environment variable "peer_cert".

The patch was made from OpenVPN svn Beta21 branches.

Here is a very simple exemple of Tls-verify script which provide OCSP
support to OpenVPN (with tls-export-cert option) without any OpenVPN
"core" modification :

X509=$2

openssl ocsp \
      -issuer /etc/openvpn/ssl.crt/RootCA.pem \
      -CAfile /etc/openvpn/ssl.capath/OpenVPNServeur-cafile.pem \
      -cert $peer_cert \
      -url http://your-ocsp-url
      if [ $? -ne 0 ]
      then
          echo "error : OCSP check failed for ${X509}" | logger -t
"tls-verify"
          exit 1
       fi

This has been discussed here:
<http://thread.gmane.org/gmane.network.openvpn.devel/2492>
<http://thread.gmane.org/gmane.network.openvpn.devel/3150>
<http://thread.gmane.org/gmane.network.openvpn.devel/3217>

This patch has been modified by David Sommerseth, by fixing a few issues
which came up to during the code review process.  The man page has been
updated and tmp_file in ssl.c is checked for not being NULL before calling
delete_file().

Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>
Acked-by: Gert Doering <gert@greenie.muc.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/openvpn.8 b/openvpn.8
index 8df9367..0744d44 100644
--- a/openvpn.8
+++ b/openvpn.8
@@ -4288,6 +4288,14 @@ to
 to build a command line which will be passed to the script.
 .\"*********************************************************
 .TP
+.B \-\-tls-export-cert directory
+Store the certificates the clients uses upon connection to this
+directory. This will be done before --tls-verify is called.  The
+certificates will use a temporary name and will be deleted when
+the tls-verify script returns.  The file name used for the certificate
+is available via the peer_cert environment variable.
+.\"*********************************************************
+.TP
 .B \-\-tls-remote name
 Accept connections only from a host with X509 name
 or common name equal to
@@ -5286,6 +5294,11 @@ than their names as denoted on the command line
 or configuration file.
 .\"*********************************************************
 .TP
+.B peer_cert
+Temporary file name containing the client certificate upon
+connection.  Useful in conjunction with --tls-verify
+.\"*********************************************************
+.TP
 .B script_context
 Set to "init" or "restart" prior to up/down script execution.
 For more information, see