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diff --git a/sample/sample-scripts/verify-cn b/sample/sample-scripts/verify-cn
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+#!/usr/bin/perl
+
+# verify-cn -- a sample OpenVPN tls-verify script
+#
+# Return 0 if cn matches the common name component of
+# subject, 1 otherwise.
+#
+# For example in OpenVPN, you could use the directive:
+#
+#   tls-verify "./verify-cn /etc/openvpn/allowed_clients"
+#
+# This would cause the connection to be dropped unless
+# the client common name is listed on a line in the
+# allowed_clients file.
+
+die "usage: verify-cn cnfile certificate_depth subject" if (@ARGV != 3);
+
+# Parse out arguments:
+#   cnfile -- The file containing the list of common names, one per
+#             line, which the client is required to have,
+#             taken from the argument to the tls-verify directive
+#             in the OpenVPN config file.
+#             The file can have blank lines and comment lines that begin
+#             with the # character.
+#   depth  -- The current certificate chain depth.  In a typical
+#             bi-level chain, the root certificate will be at level
+#             1 and the client certificate will be at level 0.
+#             This script will be called separately for each level.
+#   x509   -- the X509 subject string as extracted by OpenVPN from
+#             the client's provided certificate.
+($cnfile, $depth, $x509) = @ARGV;
+
+if ($depth == 0) {
+    # If depth is zero, we know that this is the final
+    # certificate in the chain (i.e. the client certificate),
+    # and the one we are interested in examining.
+    # If so, parse out the common name substring in
+    # the X509 subject string.
+
+    if ($x509 =~ / CN=([^,]+)/) {
+        $cn = $1;
+	# Accept the connection if the X509 common name
+	# string matches the passed cn argument.
+	open(FH, '<', $cnfile) or exit 1; # can't open, nobody authenticates!
+        while (defined($line = <FH>)) {
+	    if ($line !~ /^[[:space:]]*(#|$)/o) {
+		chop($line);
+		if ($line eq $cn) {
+		    exit 0;
+		}
+	    }
+	}
+	close(FH);
+    }
+
+    # Authentication failed -- Either we could not parse
+    # the X509 subject string, or the common name in the
+    # subject string didn't match the passed cn argument.
+    exit 1;
+}
+
+# If depth is nonzero, tell OpenVPN to continue processing
+# the certificate chain.
+exit 0;