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...@gmx.com>
---
contrib/OCSP_check/OCSP_check.sh | 89 ++++++++++++++++++++++++++++++++++++++
openvpn.8 | 7 +++-
ssl.c | 27 ++++++++++-
3 files changed, 119 insertions(+), 4 deletions(-)
create mode 100644 contrib/OCSP_check/OCSP_check.sh
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
diff --git a/openvpn.8 b/openvpn.8
index 45e61fa..a31596a 100644
--- a/openvpn.8
+++ b/openvpn.8
@@ -5321,7 +5321,12 @@ where
is the verification level. Only set for TLS connections. Set prior
to execution of
.B --tls-verify
-script.
+script. This is in the form of a hex string like "37AB46E0", which is
+suitable for doing serial-based OCSP queries (with OpenSSL, you have
+to prepend "0x" to the string). If something goes wrong while reading
+the value from the certificate it will be an empty string, so your
+code should check that.
+See the contrib/OCSP_check/OCSP_check.sh script for an example.
.\"*********************************************************
.TP
.B tun_mtu
diff --git a/ssl.c b/ssl.c
index 1b275af..68a3e3b 100644
--- a/ssl.c
+++ b/ssl.c
@@ -788,9 +788,30 @@ verify_callback (int preverify_ok, X509_STORE_CTX * ctx)
/* export serial number as environmental variable */
{
- const int serial = (int) ASN1_INTEGER_get (X509_get_serialNumber
(ctx->current_cert));
- openvpn_snprintf (envname, sizeof(envname), "tls_serial_%d",
ctx->error_depth);
- setenv_int (opt->es, envname, serial);
+ BIO *bio = NULL;
+ char serial[100];
+ int n1, n2;
+
+ CLEAR (serial);
+ if ((bio = BIO_new (BIO_s_mem ())) == NULL)
+ {
+ msg (M_WARN, "CALLBACK: Cannot create BIO (for tls_serial_%d)",
ctx->error_depth);
+ }
+ else
+ {
+ /* "prints" the serial number onto the BIO and read it back */
+ if ( ! ( ( (n1 = i2a_ASN1_INTEGER(bio, X509_get_serialNumber
(ctx->current_cert))) >= 0 ) &&
+ ( (n2 = BIO_read (bio, serial, sizeof (serial)-1)) >= 0 ) &&
+ ( n1 == n2 ) ) )
+ {
+ msg (M_WARN, "CALLBACK: Error reading/writing BIO (for
tls_serial_%d)", ctx->error_depth);
+ CLEAR (serial); /* empty string */
+ }
+
+ openvpn_snprintf (envname, sizeof(envname), "tls_serial_%d",
ctx->error_depth);
+ setenv_str (opt->es, envname, serial);
+ BIO_free(bio);
+ }
}
/* export current untrusted IP */
--
1.6.5.6
