From 3ffd13465ac1eec00fcaabe80b9b8d5498d3f3c6 Mon Sep 17 00:00:00 2001 From: Paul Elliott Date: Wed, 3 Mar 2021 17:11:32 +0000 Subject: [PATCH] Fix constant flow mask maths Signed-off-by: Paul Elliott --- library/base64.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/library/base64.c b/library/base64.c index f2ae49b412..267dcc2276 100644 --- a/library/base64.c +++ b/library/base64.c @@ -79,7 +79,9 @@ static void mbedtls_base64_cond_assign_uchar(unsigned char * dest, const unsigne #endif /* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */ - unsigned char mask = -( unsigned char )( ( condition | -condition ) >> 7 ); + unsigned char mask = ( condition | -condition ); + mask >>= 7; + mask = -mask; #if defined(_MSC_VER) #pragma warning( pop ) @@ -102,7 +104,9 @@ static void mbedtls_base64_cond_assign_uint32(uint32_t * dest, const uint32_t sr #endif /* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */ - uint32_t mask = -( uint32_t )( ( condition | -condition ) >> 31 ); + uint32_t mask = ( condition | -condition ); + mask >>= 31; + mask = -mask; #if defined(_MSC_VER) #pragma warning( pop ) @@ -111,7 +115,6 @@ static void mbedtls_base64_cond_assign_uint32(uint32_t * dest, const uint32_t sr *dest = ( src & mask ) | ( ( *dest ) & ~mask ); } - /* * Constant flow check for equality */