Add a test component with malloc(0) returning NULL

Exercise the library functions with malloc(0) returning NULL. Make
this a separte job with UBSan (and ASan) to detect potential. Other
test components jobs either use the system malloc which returns
non-NULL on Linux and FreeBSD, or the memory_buffer_alloc malloc which
returns NULL but does not give as useful feedback with ASan (because
the whole heap is a single C object).

Author: gilles-peskine-arm

tests/config-wrapper-malloc-0-null.h

@@ -0,0 +1,39 @@
+/* config.h wrapper that forces calloc(0) to return NULL.
+ * Used for testing.
+ */
+/*
+ *  Copyright (C) 2019, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed 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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#ifndef MBEDTLS_CONFIG_H
+/* Don't #define MBEDTLS_CONFIG_H, let config.h do it. */
+
+#include "mbedtls/config.h"
+
+#include <stdlib.h>
+static inline void *custom_calloc( size_t nmemb, size_t size )
+{
+    if( nmemb == 0 || size == 0 )
+        return( NULL );
+    return( calloc( nmemb, size ) );
+}
+
+#define MBEDTLS_PLATFORM_MEMORY
+#define MBEDTLS_PLATFORM_STD_CALLOC custom_calloc
+
+#endif /* MBEDTLS_CONFIG_H */

tests/scripts/all.sh

@@ -822,6 +822,22 @@ component_test_platform_calloc_macro () {
     make test
 }
 
+component_test_malloc_0_null () {
+    msg "build: malloc(0) returns NULL (ASan+UBSan build)"
+    scripts/config.pl full
+    scripts/config.pl unset MBEDTLS_MEMORY_BUFFER_ALLOC_C
+    make CC=gcc CFLAGS="'-DMBEDTLS_CONFIG_FILE=\"$PWD/tests/config-wrapper-malloc-0-null.h\"' -O -Werror -Wall -Wextra -fsanitize=address,undefined" LDFLAGS='-fsanitize=address,undefined'
+
+    msg "test: malloc(0) returns NULL (ASan+UBSan build)"
+    make test
+
+    msg "selftest: malloc(0) returns NULL (ASan+UBSan build)"
+    # By default ASan terminates the process if called with a size that's
+    # insanely large. We do this deliberately in selftest, so disable this
+    # behavior.
+    if_build_succeeded env ASAN_OPTIONS='allocator_may_return_null=1' programs/test/selftest calloc
+}
+
 component_test_aes_fewer_tables () {
     msg "build: default config with AES_FEWER_TABLES enabled"
     scripts/config.pl set MBEDTLS_AES_FEWER_TABLES