Merge pull request #716 from mpg/ct-varlen-hmac

Add constant-flow variable-length HMAC function

tests/include/test/constant_flow.h

@@ -0,0 +1,51 @@
+/**
+ * \file constant_flow.h
+ *
+ * \brief   This file contains tools to ensure tested code has constant flow.
+ */
+
+/*
+ *  Copyright (C) 2020, 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 TEST_CONSTANT_FLOW_H
+#define TEST_CONSTANT_FLOW_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
+#include <sanitizer/msan_interface.h>
+
+/* Use macros to avoid messing up with origin tracking */
+#define TEST_CF_SECRET  __msan_allocated_memory
+// void __msan_allocated_memory(const volatile void* data, size_t size);
+#define TEST_CF_PUBLIC  __msan_unpoison
+// void __msan_unpoison(const volatile void *a, size_t size);
+
+#else /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
+
+#define TEST_CF_SECRET(ptr, size)
+#define TEST_CF_PUBLIC(ptr, size)
+
+#endif /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
+
+#endif /* TEST_CONSTANT_FLOW_H */

tests/scripts/all.sh

@@ -1074,6 +1074,24 @@ component_test_full_cmake_clang () {
     if_build_succeeded env OPENSSL_CMD="$OPENSSL_NEXT" tests/compat.sh -e '^$' -f 'ARIA\|CHACHA'
 }
 
+component_test_memsan_constant_flow () {
+    # This tests both (1) accesses to undefined memory, and (2) branches or
+    # memory access depending on secret values. To distinguish between those:
+    # - unset MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN - does the failure persist?
+    # - or alternatively, change the build type to MemSanDbg, which enables
+    # origin tracking and nicer stack traces (which are useful for debugging
+    # anyway), and check if the origin was TEST_CF_SECRET() or something else.
+    msg "build: cmake MSan (clang), full config with constant flow testing"
+    scripts/config.py full
+    scripts/config.py set MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
+    scripts/config.py unset MBEDTLS_AESNI_C # memsan doesn't grok asm
+    CC=clang cmake -D CMAKE_BUILD_TYPE:String=MemSan .
+    make
+
+    msg "test: main suites (Msan + constant flow)"
+    make test
+}
+
 component_test_default_no_deprecated () {
     # Test that removing the deprecated features from the default
     # configuration leaves something consistent.

tests/scripts/check-names.sh

@@ -98,6 +98,7 @@ done
 printf "Likely typos: "
 sort -u actual-macros enum-consts > _caps
 HEADERS=$( ls include/mbedtls/*.h include/psa/*.h | egrep -v 'compat-1\.3\.h' )
+HEADERS="$HEADERS library/*.h"
 HEADERS="$HEADERS 3rdparty/everest/include/everest/everest.h 3rdparty/everest/include/everest/x25519.h"
 LIBRARY="$( ls library/*.c )"
 LIBRARY="$LIBRARY 3rdparty/everest/library/everest.c 3rdparty/everest/library/x25519.c"

tests/scripts/list-macros.sh

@@ -25,6 +25,7 @@ if [ -d include/mbedtls ]; then :; else
 fi
 
 HEADERS=$( ls include/mbedtls/*.h include/psa/*.h | egrep -v 'compat-1\.3\.h' )
+HEADERS="$HEADERS library/*.h"
 HEADERS="$HEADERS 3rdparty/everest/include/everest/everest.h 3rdparty/everest/include/everest/x25519.h"
 
 sed -n -e 's/.*#define \([a-zA-Z0-9_]*\).*/\1/p' $HEADERS \

tests/suites/test_suite_ssl.data

@@ -10529,3 +10529,19 @@ ssl_serialize_session_load_buf_size:42:"data_files/server5.crt"
 Session serialization, load buffer size: large ticket, cert
 depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialize_session_load_buf_size:1023:"data_files/server5.crt"
+
+Constant-flow HMAC: MD5
+depends_on:MBEDTLS_MD5_C
+ssl_cf_hmac:MBEDTLS_MD_MD5
+
+Constant-flow HMAC: SHA1
+depends_on:MBEDTLS_SHA1_C
+ssl_cf_hmac:MBEDTLS_MD_SHA1
+
+Constant-flow HMAC: SHA256
+depends_on:MBEDTLS_SHA256_C
+ssl_cf_hmac:MBEDTLS_MD_SHA256
+
+Constant-flow HMAC: SHA384
+depends_on:MBEDTLS_SHA512_C:!MBEDTLS_SHA512_NO_SHA384
+ssl_cf_hmac:MBEDTLS_MD_SHA384

tests/suites/test_suite_ssl.function

@@ -7,6 +7,10 @@
 #include <mbedtls/timing.h>
 #include <mbedtls/debug.h>
 
+#include <ssl_invasive.h>
+
+#include <test/constant_flow.h>
+
 typedef struct log_pattern
 {
     const char *pattern;
@@ -4263,3 +4267,97 @@ void resize_buffers_renegotiate_mfl( int mfl, int legacy_renegotiation,
     goto exit;
 }
 /* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC:MBEDTLS_TEST_HOOKS */
+void ssl_cf_hmac( int hash )
+{
+    /*
+     * Test the function mbedtls_ssl_cf_hmac() against a reference
+     * implementation.
+     */
+    mbedtls_md_context_t ctx, ref_ctx;
+    const mbedtls_md_info_t *md_info;
+    size_t out_len, block_size;
+    size_t min_in_len, in_len, max_in_len, i;
+    /* TLS additional data is 13 bytes (hence the "lucky 13" name) */
+    unsigned char add_data[13];
+    unsigned char ref_out[MBEDTLS_MD_MAX_SIZE];
+    unsigned char *data = NULL;
+    unsigned char *out = NULL;
+    unsigned char rec_num = 0;
+
+    mbedtls_md_init( &ctx );
+    mbedtls_md_init( &ref_ctx );
+
+    md_info = mbedtls_md_info_from_type( hash );
+    TEST_ASSERT( md_info != NULL );
+    out_len = mbedtls_md_get_size( md_info );
+    TEST_ASSERT( out_len != 0 );
+    block_size = hash == MBEDTLS_MD_SHA384 ? 128 : 64;
+
+    /* Use allocated out buffer to catch overwrites */
+    ASSERT_ALLOC( out, out_len );
+
+    /* Set up contexts with the given hash and a dummy key */
+    TEST_EQUAL( 0, mbedtls_md_setup( &ctx, md_info, 1 ) );
+    TEST_EQUAL( 0, mbedtls_md_setup( &ref_ctx, md_info, 1 ) );
+    memset( ref_out, 42, sizeof( ref_out ) );
+    TEST_EQUAL( 0, mbedtls_md_hmac_starts( &ctx, ref_out, out_len ) );
+    TEST_EQUAL( 0, mbedtls_md_hmac_starts( &ref_ctx, ref_out, out_len ) );
+    memset( ref_out, 0, sizeof( ref_out ) );
+
+    /*
+     * Test all possible lengths up to a point. The difference between
+     * max_in_len and min_in_len is at most 255, and make sure they both vary
+     * by at least one block size.
+     */
+    for( max_in_len = 0; max_in_len <= 255 + block_size; max_in_len++ )
+    {
+        test_set_step( max_in_len * 10000 );
+
+        /* Use allocated in buffer to catch overreads */
+        ASSERT_ALLOC( data, max_in_len );
+
+        min_in_len = max_in_len > 255 ? max_in_len - 255 : 0;
+        for( in_len = min_in_len; in_len <= max_in_len; in_len++ )
+        {
+            test_set_step( max_in_len * 10000 + in_len );
+
+            /* Set up dummy data and add_data */
+            rec_num++;
+            memset( add_data, rec_num, sizeof( add_data ) );
+            for( i = 0; i < in_len; i++ )
+                data[i] = ( i & 0xff ) ^ rec_num;
+
+            /* Get the function's result */
+            TEST_CF_SECRET( &in_len, sizeof( in_len ) );
+            TEST_EQUAL( 0, mbedtls_ssl_cf_hmac( &ctx, add_data, sizeof( add_data ),
+                                                data, in_len,
+                                                min_in_len, max_in_len,
+                                                out ) );
+            TEST_CF_PUBLIC( &in_len, sizeof( in_len ) );
+            TEST_CF_PUBLIC( out, out_len );
+
+            /* Compute the reference result */
+            TEST_EQUAL( 0, mbedtls_md_hmac_update( &ref_ctx, add_data,
+                                                   sizeof( add_data ) ) );
+            TEST_EQUAL( 0, mbedtls_md_hmac_update( &ref_ctx, data, in_len ) );
+            TEST_EQUAL( 0, mbedtls_md_hmac_finish( &ref_ctx, ref_out ) );
+            TEST_EQUAL( 0, mbedtls_md_hmac_reset( &ref_ctx ) );
+
+            /* Compare */
+            ASSERT_COMPARE( out, out_len, ref_out, out_len );
+        }
+
+        mbedtls_free( data );
+        data = NULL;
+    }
+
+exit:
+    mbedtls_md_free( &ref_ctx );
+    mbedtls_md_free( &ctx );
+
+    mbedtls_free( data );
+    mbedtls_free( out );
+}
+/* END_CASE */