Add configure option to disable testing key exchange methods

If this is used, the functionality to set a private key/value/seed for
key exchange methods is removed (including from the interface to avoid
accidentally forgetting to wrap implementations and uses of set_seed()).

The set_seed() method is assigned outside the INIT() macro to avoid
potentially undefined behavior (preprocessing directives in macro
arguments).

The test done by the crypto tester is a simple functionality test.

src/libstrongswan/plugins/openssl/openssl_diffie_hellman.c

@@ -180,6 +180,7 @@ METHOD(key_exchange_t, set_public_key, bool,
 	return TRUE;
 }
 
+#ifdef TESTABLE_KE
 #if OPENSSL_VERSION_NUMBER >= 0x30000000L
 
 /**
@@ -273,6 +274,7 @@ METHOD(key_exchange_t, set_seed, bool,
 }
 
 #endif /* OPENSSL_VERSION_NUMBER */
+#endif /* TESTABLE_KE */
 
 METHOD(key_exchange_t, destroy, void,
 	private_openssl_diffie_hellman_t *this)
@@ -304,7 +306,6 @@ openssl_diffie_hellman_t *openssl_diffie_hellman_create(
 				.get_shared_secret = _get_shared_secret,
 				.set_public_key = _set_public_key,
 				.get_public_key = _get_public_key,
-				.set_seed = _set_seed,
 				.get_method = _get_method,
 				.destroy = _destroy,
 			},
@@ -312,6 +313,10 @@ openssl_diffie_hellman_t *openssl_diffie_hellman_create(
 		.group = group,
 	);
 
+#ifdef TESTABLE_KE
+	this->public.ke.set_seed = _set_seed;
+#endif
+
 	if (group == MODP_CUSTOM)
 	{
 		chunk_t g_chunk, p_chunk;

src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.c

@@ -305,6 +305,8 @@ int openssl_ecdh_group_to_nid(key_exchange_method_t group)
 	}
 }
 
+#ifdef TESTABLE_KE
+
 /**
  * Parse the given private key as BIGNUM and calculate the corresponding public
  * key as EC_POINT.
@@ -429,6 +431,7 @@ error:
 }
 
 #endif /* OPENSSL_VERSION_NUMBER */
+#endif /* TESTABLE_KE */
 
 METHOD(key_exchange_t, destroy, void,
 	private_openssl_ec_diffie_hellman_t *this)
@@ -460,7 +463,6 @@ openssl_ec_diffie_hellman_t *openssl_ec_diffie_hellman_create(key_exchange_metho
 				.get_shared_secret = _get_shared_secret,
 				.set_public_key = _set_public_key,
 				.get_public_key = _get_public_key,
-				.set_seed = _set_seed,
 				.get_method = _get_method,
 				.destroy = _destroy,
 			},
@@ -468,6 +470,10 @@ openssl_ec_diffie_hellman_t *openssl_ec_diffie_hellman_create(key_exchange_metho
 		.group = group,
 	);
 
+#ifdef TESTABLE_KE
+	this->public.ke.set_seed = _set_seed;
+#endif
+
 #if OPENSSL_VERSION_NUMBER >= 0x30000000L
 	this->ec_group = EC_GROUP_new_by_curve_name(curve);
 	this->key = EVP_EC_gen(OSSL_EC_curve_nid2name(curve));

src/libstrongswan/plugins/openssl/openssl_kem.c

@@ -324,6 +324,8 @@ METHOD(key_exchange_t, set_public_key, bool, private_key_exchange_t *this,
 	return openssl_kem_encapsulate(this, value);
 }
 
+#ifdef TESTABLE_KE
+
 METHOD(key_exchange_t, set_seed, bool, private_key_exchange_t *this,
 	chunk_t ignore, drbg_t *seed)
 {
@@ -336,6 +338,8 @@ METHOD(key_exchange_t, set_seed, bool, private_key_exchange_t *this,
 	return TRUE;
 }
 
+#endif /* TESTABLE_KE */
+
 METHOD(key_exchange_t, destroy, void, private_key_exchange_t *this)
 {
 	EVP_PKEY_free(this->pkey);
@@ -357,12 +361,16 @@ key_exchange_t *openssl_kem_create(key_exchange_method_t method)
 			.get_shared_secret = _get_shared_secret,
 			.set_public_key = _set_public_key,
 			.get_public_key = _get_public_key,
-			.set_seed = _set_seed,
 			.get_method = _get_method,
 			.destroy = _destroy,
 		},
 		.group = method
 	);
+
+#ifdef TESTABLE_KE
+	this->public.set_seed = _set_seed;
+#endif
+
 	return &this->public;
 }
 #endif /* OPENSSL_IS_AWSLC */

src/libstrongswan/plugins/openssl/openssl_x_diffie_hellman.c

@@ -114,6 +114,8 @@ METHOD(key_exchange_t, get_public_key, bool,
 	return TRUE;
 }
 
+#ifdef TESTABLE_KE
+
 METHOD(key_exchange_t, set_seed, bool,
 	private_key_exchange_t *this, chunk_t value, drbg_t *drbg)
 {
@@ -127,6 +129,8 @@ METHOD(key_exchange_t, set_seed, bool,
 	return TRUE;
 }
 
+#endif /* TESTABLE_KE */
+
 METHOD(key_exchange_t, get_shared_secret, bool,
 	private_key_exchange_t *this, chunk_t *secret)
 {
@@ -193,13 +197,17 @@ key_exchange_t *openssl_x_diffie_hellman_create(key_exchange_method_t ke)
 			.get_shared_secret = _get_shared_secret,
 			.set_public_key = _set_public_key,
 			.get_public_key = _get_public_key,
-			.set_seed = _set_seed,
 			.get_method = _get_method,
 			.destroy = _destroy,
 		},
 		.ke = ke,
 		.key = key,
 	);
+
+#ifdef TESTABLE_KE
+	this->public.set_seed = _set_seed;
+#endif
+
 	return &this->public;
 }