Fixes for MSVC warnings
Also added a couple of missing comment blocks.
@@ -65,6 +65,9 @@ static const unsigned char base64_dec_map[128] =
#define BASE64_SIZE_T_MAX ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
+/*
+ * Constant flow conditional assignment
+*/
static void mbedtls_base64_cond_assign(unsigned char * dest, const unsigned char * const src,
unsigned char condition)
{
@@ -75,19 +78,31 @@ static void mbedtls_base64_cond_assign(unsigned char * dest, const unsigned char
}
/*
- * Constant time check for equality
+ * Constant flow check for equality
*/
-static unsigned char mbedtls_base64_eq(uint32_t in_a, uint32_t in_b)
+static unsigned char mbedtls_base64_eq(size_t in_a, size_t in_b)
{
uint32_t difference = in_a ^ in_b;
+ /* MSVC has a warning about unary minus on unsigned integer types,
+ * but this is well-defined and precisely what we want to do here. */
+#if defined(_MSC_VER)
+#pragma warning( push )
+#pragma warning( disable : 4146 )
+#endif
+
difference |= -difference;
+
+#if defined(_MSC_VER)
+#pragma warning( pop )
+#endif
+
difference >>= 31;
return (unsigned char) ( 1 ^ difference );
}
/*
- * Constant time lookup into table.
+ * Constant flow lookup into table.
*/
static unsigned char mbedtls_base64_table_lookup(const unsigned char * const table,
const size_t table_size, const size_t table_index)
