Add MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
This option allows to test the constant-flow nature of selected code, using
MemSan and the fundamental observation behind ctgrind that the set of
operations allowed on undefined memory by dynamic analysers is the same as the
set of operations allowed on secret data to avoid leaking it to a local
attacker via side channels, namely, any operation except branching and
dereferencing.
(This isn't the full story, as on some CPUs some instructions have variable
execution depending on the inputs, most notably division and on some cores
multiplication. However, testing that no branch or memory access depends on
secret data is already a good start.)
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index f2148a8..15cc21b 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 e00c546..124c597 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1907,6 +1907,19 @@
//#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
*
* Enable features for invasive testing such as introspection functions and