Test the library when malloc(0) returns NULL

programs/test/selftest.c

@@ -65,6 +65,8 @@
 #else
 #include <stdio.h>
 #include <stdlib.h>
+#define mbedtls_calloc     calloc
+#define mbedtls_free       free
 #define mbedtls_printf     printf
 #define mbedtls_snprintf   snprintf
 #define mbedtls_exit       exit
@@ -77,6 +79,86 @@
 #endif
 
 
+#if defined MBEDTLS_SELF_TEST
+/* Sanity check for malloc. This is not expected to fail, and is rather
+ * intended to display potentially useful information about the platform,
+ * in particular the behavior of malloc(0). */
+static int calloc_self_test( int verbose )
+{
+    int failures = 0;
+    void *empty1 = mbedtls_calloc( 0, 1 );
+    void *empty2 = mbedtls_calloc( 0, 1 );
+    void *buffer1 = mbedtls_calloc( 1, 1 );
+    void *buffer2 = mbedtls_calloc( 1, 1 );
+    uintptr_t old_buffer1;
+
+    if( empty1 == NULL && empty2 == NULL )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(0): passed (NULL)\n" );
+    }
+    else if( empty1 == NULL || empty2 == NULL )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(0): failed (mix of NULL and non-NULL)\n" );
+        ++failures;
+    }
+    else if( empty1 == empty2 )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(0): passed (same non-null)\n" );
+    }
+    else
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(0): passed (distinct non-null)\n" );
+    }
+
+    if( buffer1 == NULL || buffer2 == NULL )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(1): failed (NULL)\n" );
+        ++failures;
+    }
+    else if( buffer1 == buffer2 )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(1): failed (same buffer twice)\n" );
+        ++failures;
+    }
+    else
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(1): passed\n" );
+    }
+
+    old_buffer1 = (uintptr_t) buffer1;
+    mbedtls_free( buffer1 );
+    buffer1 = mbedtls_calloc( 1, 1 );
+    if( buffer1 == NULL )
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(1 again): failed (NULL)\n" );
+        ++failures;
+    }
+    else
+    {
+        if( verbose )
+            mbedtls_printf( "  CALLOC(1 again): passed (%s address)\n",
+                            (uintptr_t) old_buffer1 == (uintptr_t) buffer1 ?
+                            "same" : "different" );
+    }
+
+    if( verbose )
+        mbedtls_printf( "\n" );
+    mbedtls_free( empty1 );
+    mbedtls_free( empty2 );
+    mbedtls_free( buffer1 );
+    mbedtls_free( buffer2 );
+    return( failures );
+}
+#endif /* MBEDTLS_SELF_TEST */
+
 static int test_snprintf( size_t n, const char ref_buf[10], int ref_ret )
 {
     int ret;
@@ -173,6 +255,7 @@ typedef struct
 
 const selftest_t selftests[] =
 {
+    {"calloc", calloc_self_test},
 #if defined(MBEDTLS_MD2_C)
     {"md2", mbedtls_md2_self_test},
 #endif

tests/configs/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 +822,21 @@ 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/configs/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)"
+    # Just the calloc selftest. "make test" ran the others as part of the
+    # test suites.
+    if_build_succeeded 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