Don't exit daemon if opening or parsing the CRL fails.

As requested in trac ticket #83, the daemon should not exit if opening the
CRL file during a connection attempt fails; OpenVPN should merely deny the
connection.

CRL files need to be periodically updated. When users update their CRL in
place and a connection attempt takes place simultaneously, the CRL file
might temporarily not be available, or not be in a consistent state.
Previously, that would result in the daemon exiting. With this patch, that
results in one (or possibly a few) failed connection attempts, but service
will restore automatically as soon as the CRL is again available in a valid
state.

Note that on startup OpenVPN still checks the existence and accessibility
of the CRL file, and will refuse to start on error.

While I was touching the code, I improved error reporting for the PolarSSL
code a bit. The polar code opens and parses the CRL in a single call, so
on error retrieve details from polarssl and report those to the user.

Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <53BED57C.7070300@fox-it.com>
Signed-off-by: Gert Doering <gert@greenie.muc.de>

2 files changed, 7 insertions, 4 deletions

diff --git a/src/openvpn/ssl_verify_openssl.c b/src/openvpn/ssl_verify_openssl.c
index 2482eaa..cbcff02 100644
--- a/src/openvpn/ssl_verify_openssl.c
+++ b/src/openvpn/ssl_verify_openssl.c
@@ -591,12 +591,12 @@ x509_verify_crl(const char *crl_file, X509 *peer_cert, const char *subject)
   in = BIO_new_file (crl_file, "r");
 
   if (in == NULL) {
-    msg (M_ERR, "CRL: cannot read: %s", crl_file);
+    msg (M_WARN, "CRL: cannot read: %s", crl_file);
     goto end;
   }
   crl=PEM_read_bio_X509_CRL(in,NULL,NULL,NULL);
   if (crl == NULL) {
-    msg (M_ERR, "CRL: cannot read CRL from file %s", crl_file);
+    msg (M_WARN, "CRL: cannot read CRL from file %s", crl_file);
     goto end;
   }
 
diff --git a/src/openvpn/ssl_verify_polarssl.c b/src/openvpn/ssl_verify_polarssl.c
index 7e8b517..2b7c214 100644
--- a/src/openvpn/ssl_verify_polarssl.c
+++ b/src/openvpn/ssl_verify_polarssl.c
@@ -371,9 +371,12 @@ x509_verify_crl(const char *crl_file, x509_crt *cert, const char *subject)
   result_t retval = FAILURE;
   x509_crl crl = {0};
 
-  if (x509_crl_parse_file(&crl, crl_file) != 0)
+  int polar_retval = x509_crl_parse_file(&crl, crl_file);
+  if (polar_retval != 0)
     {
-      msg (M_ERR, "CRL: cannot read CRL from file %s", crl_file);
+      char errstr[128];
+      polarssl_strerror(polar_retval, errstr, sizeof(errstr));
+      msg (M_WARN, "CRL: cannot read CRL from file %s (%s)", crl_file, errstr);
       goto end;
     }