Merge pull request #8144 from daverodgman/zeroize-stronger
Add more protection to mbedtls_platform_zeroize
diff --git a/library/platform_util.c b/library/platform_util.c
index 63b7c41..09216ed 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -126,6 +126,26 @@
#else
memset_func(buf, 0, len);
#endif
+
+#if defined(__GNUC__)
+ /* For clang and recent gcc, pretend that we have some assembly that reads the
+ * zero'd memory as an additional protection against being optimised away. */
+#if defined(__clang__) || (__GNUC__ >= 10)
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wvla"
+#elif defined(MBEDTLS_COMPILER_IS_GCC)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wvla"
+#endif
+ asm volatile ("" : : "m" (*(char (*)[len]) buf) :);
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#elif defined(MBEDTLS_COMPILER_IS_GCC)
+#pragma GCC diagnostic pop
+#endif
+#endif
+#endif
}
}
#endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */