Detect unusable ciphers on patched OpenSSL of RHEL/Centos

OpenSSL on RHEL 8 and CentOS 8 system when these system are put into
FIPS mode need extra code to figure out if a specific cipher algorithm
is usable on these system. This is particularly problem in data-ciphers
as the errors might occur much later when a client connects and as these
cipher are not caught during config initialisation.

This also prepares for adding Chacha20-Poly1305 when available to
data-ciphers by making the detection logic used to check if
cipher_kt_get returns non-NULL work on these systems.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: David Sommerseth <davids@openvpn.net>
Message-Id: <20210818213354.687736-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22746.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/src/openvpn/crypto.c b/src/openvpn/crypto.c
index b9c95225a612b33b13bedbc1914e4d3af18ebcc4..1dfc760f906dc46b9b310528b2915e93a1ee15bf 100644 (file)
--- a/src/openvpn/crypto.c
+++ b/src/openvpn/crypto.c
@@ -1806,6 +1806,12 @@ print_cipher(const cipher_kt_t *cipher)
     {
         printf(", TLS client/server mode only");
     }
+#ifdef OPENSSL_FIPS
+    if (FIPS_mode() && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_FIPS))
+    {
+        printf(", disabled by FIPS mode");
+    }
+#endif
 
     printf(")\n");
 }

diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
index b55d32b2ce0416721a83d3a2c2697be36e60a31a..419265a51adaa448571fb51948acfeb5a4253a37 100644 (file)
--- a/src/openvpn/crypto_openssl.c
+++ b/src/openvpn/crypto_openssl.c
@@ -599,7 +599,17 @@ cipher_kt_get(const char *ciphername)
         return NULL;
     }
 
+#ifdef OPENSSL_FIPS
+    /* Rhel 8/CentOS 8 have a patched OpenSSL version that return a cipher
+     * here that is actually not usable if in FIPS mode */
 
+    if (FIPS_mode() && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_FIPS))
+    {
+        msg(D_LOW, "Cipher algorithm '%s' is known by OpenSSL library but "
+                    "currently disabled by running in FIPS mode.", ciphername);
+        return NULL;
+    }
+#endif
     if (EVP_CIPHER_key_length(cipher) > MAX_CIPHER_KEY_LENGTH)
     {
         msg(D_LOW, "Cipher algorithm '%s' uses a default key size (%d bytes) "