Fix certificate serial number export

    contrib/OCSP_check/OCSP_check.sh:
             New barebone script to demonstrate how to use $tls_serial_{n}
             to perform simple OCSP queries using OpenSSL command line
             "openssl ocsp". Minimal sanity checks to fail if user tries to
             use it without customizing.

    openvpn.8:
             Added some notes about $tls_serial_{n} format and usage to the
             existing description.

    ssl.c:
             correctly manage and export serial numbers of any size (as
             parsed by OpenSSL) into the environment. Set to empty string
             in case of errors, as 0 and negative numbers are all possible
             (although illegal) certificate serial numbers. Use an OpenSSL
             BIO object to do the job. Conforms to coding style guidelines.

    See the discussion at

    http://article.gmane.org/gmane.network.openvpn.devel/3588

    for more details.

Signed-off-by: Davide Brini <dave_br@gmx.com>
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>
Acked-by: David Sommerseth <dazo@users.sourceforge.net>

1 files changed, 89 insertions, 0 deletions

diff --git a/contrib/OCSP_check/OCSP_check.sh b/contrib/OCSP_check/OCSP_check.sh
new file mode 100644
index 0000000..2ffe5d6
--- /dev/null
+++ b/contrib/OCSP_check/OCSP_check.sh
@@ -0,0 +1,89 @@
+#!/bin/sh
+
+# Sample script to perform OCSP queries with OpenSSL
+# given a certificate serial number.
+
+# If you run your own CA, you can set up a very simple
+# OCSP server using the -port option to "openssl ocsp".
+
+# Full documentation and examples:
+# http://www.openssl.org/docs/apps/ocsp.html
+
+
+# Edit the following values to suit your needs
+
+# OCSP responder URL (mandatory)
+# YOU MUST UNCOMMENT ONE OF THESE AND SET IT TO A VALID SERVER
+#ocsp_url="http://ocsp.example.com/"
+#ocsp_url="https://ocsp.secure.example.com/"
+
+# Path to issuer certificate (mandatory)
+# YOU MUST SET THIS TO THE PATH TO THE CA CERTIFICATE
+issuer="/path/to/CAcert.crt"
+
+# use a nonce in the query, set to "-no_nonce" to not use it
+nonce="-nonce"
+
+# Verify the response
+# YOU MUST SET THIS TO THE PATH TO THE RESPONSE VERIFICATION CERT
+verify="/path/to/CAcert.crt"
+
+# Depth in the certificate chain where the cert to verify is.
+# Set to -1 to run the verification at every level (NOTE that
+# in that case you need a more complex script as the various
+# parameters for the query will likely be different at each level)
+# "0" is the usual value here, where the client certificate is
+check_depth=0
+
+cur_depth=$1     # this is the *CURRENT* depth
+common_name=$2   # CN in case you need it
+
+# minimal sanity checks
+
+err=0
+if [ -z "$issuer" ] || [ ! -e "$issuer" ]; then
+  echo "Error: issuer certificate undefined or not found!" >&2
+  err=1
+fi
+
+if [ -z "$verify" ] || [ ! -e "$verify" ]; then
+  echo "Error: verification certificate undefined or not found!" >&2
+  err=1
+fi
+
+if [ -z "$ocsp_url" ]; then
+  echo "Error: OCSP server URL not defined!" >&2
+  err=1
+fi
+
+if [ $err -eq 1 ]; then
+  echo "Did you forget to customize the variables in the script?" >&2
+  exit 1
+fi
+
+# begin
+if [ $check_depth -eq -1 ] || [ $cur_depth -eq $check_depth ]; then
+  eval serial="\$tls_serial_${cur_depth}"
+
+  # Check that the serial is not empty
+  if [ -n "$serial" ]; then
+
+    # This is only an example; you are encouraged to run this command (without
+    # redirections) manually against your or your CA's OCSP server to see how
+    # it responds, and adapt accordingly.
+    # Sample output:
+    #
+    # Response verify OK
+    # 0x428740A5: good
+    #      This Update: Apr 24 19:38:49 2010 GMT
+    #      Next Update: May  2 14:23:42 2010 GMT
+
+    openssl ocsp -issuer "$issuer" \
+                 "$nonce" \
+                 -CAfile "$verify" \
+                 -url "$ocsp_url" \
+                 -serial "0x${serial}" >/dev/null 2>&1
+  else
+    exit 1
+  fi
+fi