openssl: Only announce ECDH groups actually supported by OpenSSL

Determined by whether the library provides curves for it or not.
For instance, in the OpenSSL 3 FIPS provider the Brainpool curves are
not included.  And in the Fedora package several weak curves are
explicitly patched out and the Brainpool curves are omitted even in
non-FIPS mode.

diff --git a/src/libstrongswan/plugins/openssl/openssl_plugin.c b/src/libstrongswan/plugins/openssl/openssl_plugin.c
index a989b1da6c397328508a4dddd630342045e0bb4f..49b77f8acdbb6861ad4c589fd319dbac09abaf6d 100644 (file)
--- a/src/libstrongswan/plugins/openssl/openssl_plugin.c
+++ b/src/libstrongswan/plugins/openssl/openssl_plugin.c
@@ -28,6 +28,9 @@
 #ifndef OPENSSL_NO_ENGINE
 #include <openssl/engine.h>
 #endif
+#ifndef OPENSSL_NO_ECDH
+#include <openssl/ec.h>
+#endif
 
 #include "openssl_plugin.h"
 #include "openssl_util.h"
@@ -486,10 +489,55 @@ METHOD(plugin_t, get_name, char*,
        return "openssl";
 }
 
+#ifndef OPENSSL_NO_ECDH
+/**
+ * Check if the given DH group is in the list of supported curves.
+ */
+static bool ecdh_group_supported(EC_builtin_curve *curves, size_t num_curves,
+                                                                diffie_hellman_group_t group)
+{
+       int j;
+
+       for (j = 0; j < num_curves; j++)
+       {
+               if (curves[j].nid == openssl_ecdh_group_to_nid(group))
+               {
+                       return TRUE;
+               }
+       }
+       return FALSE;
+}
+
+/**
+ * Only add features for ECDH groups that are actually supported.
+ */
+static void add_ecdh_features(plugin_feature_t *features,
+                                                         plugin_feature_t *to_add, int count, int *pos)
+{
+       size_t num_curves;
+       int i;
+
+       num_curves = EC_get_builtin_curves(NULL, 0);
+
+       EC_builtin_curve curves[num_curves];
+
+       num_curves = EC_get_builtin_curves(curves, num_curves);
+
+       for (i = 0; i < count; i++)
+       {
+               if (to_add[i].kind != FEATURE_PROVIDE ||
+                       ecdh_group_supported(curves, num_curves, to_add[i].arg.dh_group))
+               {
+                       features[(*pos)++] = to_add[i];
+               }
+       }
+}
+#endif /* OPENSSL_NO_ECDH */
+
 METHOD(plugin_t, get_features, int,
        private_openssl_plugin_t *this, plugin_feature_t *features[])
 {
-       static plugin_feature_t f[] = {
+       static plugin_feature_t f_base[] = {
                /* we provide OpenSSL threading callbacks */
                PLUGIN_PROVIDE(CUSTOM, "openssl-threading"),
                /* crypters */
@@ -635,21 +683,6 @@ METHOD(plugin_t, get_features, int,
                        PLUGIN_PROVIDE(AEAD, ENCR_CHACHA20_POLY1305, 32),
 #endif /* OPENSSL_NO_CHACHA */
 #endif /* OPENSSL_VERSION_NUMBER */
-#ifndef OPENSSL_NO_ECDH
-               /* EC DH groups */
-               PLUGIN_REGISTER(DH, openssl_ec_diffie_hellman_create),
-                       PLUGIN_PROVIDE(DH, ECP_256_BIT),
-                       PLUGIN_PROVIDE(DH, ECP_384_BIT),
-                       PLUGIN_PROVIDE(DH, ECP_521_BIT),
-                       PLUGIN_PROVIDE(DH, ECP_224_BIT),
-                       PLUGIN_PROVIDE(DH, ECP_192_BIT),
-#if OPENSSL_VERSION_NUMBER >= 0x10002000L
-                       PLUGIN_PROVIDE(DH, ECP_256_BP),
-                       PLUGIN_PROVIDE(DH, ECP_384_BP),
-                       PLUGIN_PROVIDE(DH, ECP_512_BP),
-                       PLUGIN_PROVIDE(DH, ECP_224_BP),
-#endif /* OPENSSL_VERSION_NUMBER */
-#endif /* OPENSSL_NO_ECDH */
 #ifndef OPENSSL_NO_DH
                /* MODP DH groups */
                PLUGIN_REGISTER(DH, openssl_diffie_hellman_create),
@@ -809,6 +842,33 @@ METHOD(plugin_t, get_features, int,
                        PLUGIN_PROVIDE(RNG, RNG_STRONG),
                        PLUGIN_PROVIDE(RNG, RNG_WEAK),
        };
+       static plugin_feature_t f_ecdh[] = {
+#ifndef OPENSSL_NO_ECDH
+               /* EC DH groups */
+               PLUGIN_REGISTER(DH, openssl_ec_diffie_hellman_create),
+                       PLUGIN_PROVIDE(DH, ECP_256_BIT),
+                       PLUGIN_PROVIDE(DH, ECP_384_BIT),
+                       PLUGIN_PROVIDE(DH, ECP_521_BIT),
+                       PLUGIN_PROVIDE(DH, ECP_224_BIT),
+                       PLUGIN_PROVIDE(DH, ECP_192_BIT),
+#if OPENSSL_VERSION_NUMBER >= 0x10002000L
+                       PLUGIN_PROVIDE(DH, ECP_256_BP),
+                       PLUGIN_PROVIDE(DH, ECP_384_BP),
+                       PLUGIN_PROVIDE(DH, ECP_512_BP),
+                       PLUGIN_PROVIDE(DH, ECP_224_BP),
+#endif /* OPENSSL_VERSION_NUMBER */
+#endif /* OPENSSL_NO_ECDH */
+       };
+       static plugin_feature_t f[countof(f_base) + countof(f_ecdh)] = {};
+       static int count = 0;
+
+       if (!count)
+       {
+               plugin_features_add(f, f_base, countof(f_base), &count);
+#ifndef OPENSSL_NO_ECDH
+               add_ecdh_features(f, f_ecdh, countof(f_ecdh), &count);
+#endif
+       }
        *features = f;
        return countof(f);
 }