diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index f2148a8b5..15cc21b64 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -186,6 +186,16 @@
 #error "MBEDTLS_ENTROPY_FORCE_SHA256 defined, but not all prerequisites"
 #endif
 
+#if defined(__has_feature)
+#if __has_feature(memory_sanitizer)
+#define MBEDTLS_HAS_MEMSAN
+#endif
+#endif
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN) &&  !defined(MBEDTLS_HAS_MEMSAN)
+#error "MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN requires building with MemorySanitizer"
+#endif
+#undef MBEDTLS_HAS_MEMSAN
+
 #if defined(MBEDTLS_TEST_NULL_ENTROPY) && \
     ( !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES) )
 #error "MBEDTLS_TEST_NULL_ENTROPY defined, but not all prerequisites"
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index e00c546e5..124c597b6 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1906,6 +1906,19 @@
  */
 //#define MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
 
+/**
+ * \def MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
+ *
+ * Enable testing of the constant-flow nature of some sensitive functions with
+ * clang's MemorySanitizer. This causes some existing tests to also test
+ * non-functional properties of the code under test.
+ *
+ * This setting requires compiling with clang -fsanitize=memory.
+ *
+ * Uncomment to enable testing of the constant-flow nature of seletected code.
+ */
+//#define MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
+
 /**
  * \def MBEDTLS_TEST_HOOKS
  *
diff --git a/library/version_features.c b/library/version_features.c
index 64e9e86db..2470d8d1d 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -557,6 +557,9 @@ static const char * const features[] = {
 #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH)
     "MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH",
 #endif /* MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH */
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
+    "MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN",
+#endif /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
 #if defined(MBEDTLS_TEST_HOOKS)
     "MBEDTLS_TEST_HOOKS",
 #endif /* MBEDTLS_TEST_HOOKS */
diff --git a/programs/test/query_config.c b/programs/test/query_config.c
index 98b065bfe..23dc51512 100644
--- a/programs/test/query_config.c
+++ b/programs/test/query_config.c
@@ -1538,6 +1538,14 @@ int query_config( const char *config )
     }
 #endif /* MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH */
 
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
+    if( strcmp( "MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN", config ) == 0 )
+    {
+        MACRO_EXPANSION_TO_STR( MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN );
+        return( 0 );
+    }
+#endif /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
+
 #if defined(MBEDTLS_TEST_HOOKS)
     if( strcmp( "MBEDTLS_TEST_HOOKS", config ) == 0 )
     {
diff --git a/scripts/config.py b/scripts/config.py
index 3d297dc3d..793e9dfa7 100755
--- a/scripts/config.py
+++ b/scripts/config.py
@@ -194,6 +194,7 @@ EXCLUDE_FROM_FULL = frozenset([
     'MBEDTLS_RSA_NO_CRT', # influences the use of RSA in X.509 and TLS
     'MBEDTLS_SHA512_NO_SHA384', # removes a feature
     'MBEDTLS_SSL_HW_RECORD_ACCEL', # build dependency (hook functions)
+    'MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN', # build dependency (clang+memsan)
     'MBEDTLS_TEST_NULL_ENTROPY', # removes a feature
     'MBEDTLS_X509_ALLOW_UNSUPPORTED_CRITICAL_EXTENSION', # influences the use of X.509 in TLS
     'MBEDTLS_ZLIB_SUPPORT', # build dependency (libz)
diff --git a/tests/include/test/constant_flow.h b/tests/include/test/constant_flow.h
new file mode 100644
index 000000000..98bee7e48
--- /dev/null
+++ b/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 */
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index ec61d1962..9c9247f8f 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1074,6 +1074,18 @@ 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 () {
+    msg "build: cmake memsan, 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 (memsan constant flow)"
+    make test
+}
+
 component_test_default_no_deprecated () {
     # Test that removing the deprecated features from the default
     # configuration leaves something consistent.
diff --git a/visualc/VS2010/mbedTLS.vcxproj b/visualc/VS2010/mbedTLS.vcxproj
index 15eb6b583..578289f17 100644
--- a/visualc/VS2010/mbedTLS.vcxproj
+++ b/visualc/VS2010/mbedTLS.vcxproj
@@ -232,6 +232,7 @@
     <ClInclude Include="..\..\include\psa\crypto_struct.h" />
     <ClInclude Include="..\..\include\psa\crypto_types.h" />
     <ClInclude Include="..\..\include\psa\crypto_values.h" />
+    <ClInclude Include="..\..\tests\include\test\constant_flow.h" />
     <ClInclude Include="..\..\tests\include\test\helpers.h" />
     <ClInclude Include="..\..\tests\include\test\macros.h" />
     <ClInclude Include="..\..\tests\include\test\psa_crypto_helpers.h" />