GUACAMOLE-1669: Prefer FIPS compliant ciphers and algorithms when FIPS mode is enabled.

src/common-ssh/ssh.c

@@ -22,6 +22,7 @@
 #include "common-ssh/user.h"
 
 #include <guacamole/client.h>
+#include <guacamole/fips.h>
 #include <libssh2.h>
 
 #ifdef LIBSSH2_USES_GCRYPT
@@ -46,6 +47,17 @@
 GCRY_THREAD_OPTION_PTHREAD_IMPL;
 #endif
 
+/**
+ * A list of all key exchange algorithms that are both FIPS-compliant, and
+ * OpenSSL-supported.
+ */
+#define FIPS_COMPLIANT_KEX_ALGORITHMS "diffie-hellman-group-exchange-sha256"
+
+/**
+ * A list of ciphers that are both FIPS-compliant, and OpenSSL-supported.
+ */
+#define FIPS_COMPLIANT_CIPHERS "aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,aes192-cbc,aes256-cbc"
+
 #ifdef OPENSSL_REQUIRES_THREADING_CALLBACKS
 /**
  * Array of mutexes, used by OpenSSL.
@@ -486,6 +498,17 @@ guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
         return NULL;
     }
 
+    /*
+     * If FIPS mode is enabled, prefer only FIPS-compatible algorithms and
+     * ciphers that are also supported by libssh2. For more info, see:
+     * https://csrc.nist.gov/CSRC/media/projects/cryptographic-module-validation-program/documents/security-policies/140sp2906.pdf
+     */
+    if (guac_fips_enabled()) {
+        libssh2_session_method_pref(session, LIBSSH2_METHOD_KEX, FIPS_COMPLIANT_KEX_ALGORITHMS);
+        libssh2_session_method_pref(session, LIBSSH2_METHOD_CRYPT_CS, FIPS_COMPLIANT_CIPHERS);
+        libssh2_session_method_pref(session, LIBSSH2_METHOD_CRYPT_SC, FIPS_COMPLIANT_CIPHERS);
+    }
+
     /* Perform handshake */
     if (libssh2_session_handshake(session, fd)) {
         guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR,

src/libguac/Makefile.am

@@ -44,6 +44,7 @@ libguacinc_HEADERS =                  \
     guacamole/client-types.h          \
     guacamole/error.h                 \
     guacamole/error-types.h           \
+    guacamole/fips.h                  \
     guacamole/hash.h                  \
     guacamole/layer.h                 \
     guacamole/layer-types.h           \
@@ -93,6 +94,7 @@ libguac_la_SOURCES =   \
     encode-jpeg.c      \
     encode-png.c       \
     error.c            \
+    fips.c             \
     hash.c             \
     id.c               \
     palette.c          \

src/libguac/fips.c

@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include "config.h"
+#include "guacamole/fips.h"
+
+/* If OpenSSL is available, include header for version numbers */
+#ifdef ENABLE_SSL
+    #include <openssl/opensslv.h>
+
+    /* OpenSSL versions prior to 0.9.7e did not have FIPS support */
+    #if !defined(OPENSSL_VERSION_NUMBER) || (OPENSSL_VERSION_NUMBER < 0x00090705f)
+    #define GUAC_FIPS_ENABLED 0
+
+    /* OpenSSL 3+ uses EVP_default_properties_is_fips_enabled() */
+    #elif defined(OPENSSL_VERSION_MAJOR) && (OPENSSL_VERSION_MAJOR >= 3)
+    #include <openssl/evp.h>
+    #define GUAC_FIPS_ENABLED EVP_default_properties_is_fips_enabled(NULL)
+
+    /* For OpenSSL versions between 0.9.7e and 3.0, use FIPS_mode() */
+    #else
+    #include <openssl/crypto.h>
+    #define GUAC_FIPS_ENABLED FIPS_mode()
+    #endif
+
+/* FIPS support does not exist if OpenSSL is not available. */
+#else
+#define GUAC_FIPS_ENABLED 0
+#endif
+
+int guac_fips_enabled() {
+
+    return GUAC_FIPS_ENABLED;
+
+}

src/libguac/guacamole/fips.h

@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef GUAC_FIPS_H
+#define GUAC_FIPS_H
+
+/**
+ * Returns a non-zero value if FIPS mode is enabled, or zero if FIPS mode
+ * is not enabled.
+ *
+ * @return
+ *      A non-zero value if FIPS mode is enabled, or zero if FIPS mode is
+ *      not enabled.
+ */
+int guac_fips_enabled();
+
+#endif