- Enable ECDHE for servers. Where available, use

SSL_CTX_set_ecdh_auto() for TLS-wrapped server configurations to
  enable ECDHE.  Otherwise, manually offer curve p256.
  Client connections should automatically use ECDHE when available.
  (thanks Daniel Kahn Gillmor)


git-svn-id: file:///svn/unbound/trunk@3452 be551aaa-1e26-0410-a405-d3ace91eadb9

config.h.in

@@ -327,6 +327,9 @@
 /* Define if you have the SSL libraries installed. */
 #undef HAVE_SSL
 
+/* Define to 1 if you have the `SSL_CTX_set_ecdh_auto' function. */
+#undef HAVE_SSL_CTX_SET_ECDH_AUTO
+
 /* Define to 1 if you have the <stdarg.h> header file. */
 #undef HAVE_STDARG_H
 

configure

@@ -16773,7 +16773,7 @@ fi
 
 done
 
-for ac_func in OPENSSL_config EVP_sha1 EVP_sha256 EVP_sha512 FIPS_mode
+for ac_func in OPENSSL_config EVP_sha1 EVP_sha256 EVP_sha512 FIPS_mode SSL_CTX_set_ecdh_auto
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"

configure.ac

@@ -577,7 +577,7 @@ else
 fi
 AC_CHECK_HEADERS([openssl/conf.h],,, [AC_INCLUDES_DEFAULT])
 AC_CHECK_HEADERS([openssl/engine.h],,, [AC_INCLUDES_DEFAULT])
-AC_CHECK_FUNCS([OPENSSL_config EVP_sha1 EVP_sha256 EVP_sha512 FIPS_mode])
+AC_CHECK_FUNCS([OPENSSL_config EVP_sha1 EVP_sha256 EVP_sha512 FIPS_mode SSL_CTX_set_ecdh_auto])
 AC_CHECK_DECLS([SSL_COMP_get_compression_methods,sk_SSL_COMP_pop_free], [], [], [
 AC_INCLUDES_DEFAULT
 #ifdef HAVE_OPENSSL_ERR_H

daemon/remote.c

@@ -258,6 +258,23 @@ daemon_remote_create(struct config_file* cfg)
 		log_crypto_err("Error in SSL_CTX check_private_key");
 		goto setup_error;
 	}
+#ifdef SSL_CTX_SET_ECDH_AUTO
+	if(!SSL_CTX_set_ecdh_auto(rc->ctx,1)) {
+		log_crypto_err("Error in SSL_CTX_ecdh_auto, not enabling ECDHE");
+	}
+#elif defined(USE_ECDSA)
+	if(1) {
+		EC_KEY *ecdh = EC_KEY_new_by_curve_name (NID_X9_62_prime256v1);
+		if (!ecdh) {
+			log_crypto_err("could not find p256, not enabling ECDHE");
+		} else {
+			if (1 != SSL_CTX_set_tmp_ecdh (rc->ctx, ecdh)) {
+				log_crypto_err("Error in SSL_CTX_set_tmp_ecdh, not enabling ECDHE");
+			}
+			EC_KEY_free (ecdh);
+		}
+	}
+#endif
 	if(!SSL_CTX_load_verify_locations(rc->ctx, s_cert, NULL)) {
 		log_crypto_err("Error setting up SSL_CTX verify locations");
 	setup_error:

doc/Changelog

@@ -1,3 +1,10 @@
+20 July 2015: Wouter
+	- Enable ECDHE for servers.  Where available, use
+	  SSL_CTX_set_ecdh_auto() for TLS-wrapped server configurations to
+	  enable ECDHE.  Otherwise, manually offer curve p256.
+	  Client connections should automatically use ECDHE when available.
+	  (thanks Daniel Kahn Gillmor)
+
 18 July 2015: Willem
 	- Allow certificate chain files to allow for intermediate certificates.
 	  (thanks Daniel Kahn Gillmor)

testcode/petal.c

@@ -242,6 +242,22 @@ setup_ctx(char* key, char* cert)
 		print_exit("cannot read key");
 	if(!SSL_CTX_check_private_key(ctx))
 		print_exit("private key is not correct");
+#ifdef SSL_CTX_SET_ECDH_AUTO
+	if (!SSL_CTX_set_ecdh_auto(ctx,1))
+		if(verb>=1) printf("failed to set_ecdh_auto, not enabling ECDHE\n");
+#elif defined(USE_ECDSA)
+	if(1) {
+		EC_KEY *ecdh = EC_KEY_new_by_curve_name (NID_X9_62_prime256v1);
+		if (!ecdh) {
+			if(verb>=1) printf("could not find p256, not enabling ECDHE\n");
+		} else {
+			if (1 != SSL_CTX_set_tmp_ecdh (ctx, ecdh)) {
+				if(verb>=1) printf("Error in SSL_CTX_set_tmp_ecdh, not enabling ECDHE\n");
+			}
+			EC_KEY_free(ecdh);
+		}
+	}
+#endif
 	if(!SSL_CTX_load_verify_locations(ctx, cert, NULL))
 		print_exit("cannot load cert verify locations");
 	return ctx;

util/net_help.c

@@ -647,6 +647,23 @@ void* listen_sslctx_create(char* key, char* pem, char* verifypem)
 		SSL_CTX_free(ctx);
 		return NULL;
 	}
+#ifdef SSL_CTX_SET_ECDH_AUTO
+	if(!SSL_CTX_set_ecdh_auto(ctx,1)) {
+		log_crypto_err("Error in SSL_CTX_ecdh_auto, not enabling ECDHE");
+	}
+#elif defined(USE_ECDSA)
+	if(1) {
+		EC_KEY *ecdh = EC_KEY_new_by_curve_name (NID_X9_62_prime256v1);
+		if (!ecdh) {
+			log_crypto_err("could not find p256, not enabling ECDHE");
+		} else {
+			if (1 != SSL_CTX_set_tmp_ecdh (ctx, ecdh)) {
+				log_crypto_err("Error in SSL_CTX_set_tmp_ecdh, not enabling ECDHE");
+			}
+			EC_KEY_free (ecdh);
+		}
+	}
+#endif
 
 	if(verifypem && verifypem[0]) {
 		if(!SSL_CTX_load_verify_locations(ctx, verifypem, NULL)) {