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Check HMAC in constant-time in crypt_and_hash

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This commit is contained in:
Paul Bakker 2013-10-31 14:22:08 +01:00
parent 0d7702c3ee
commit 424cd6943c
1 changed files with 7 additions and 1 deletions
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8
programs/aes/crypt_and_hash.c
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@ -76,6 +76,7 @@ int main( int argc, char *argv[] )
unsigned char digest[POLARSSL_MD_MAX_SIZE]; unsigned char digest[POLARSSL_MD_MAX_SIZE];
unsigned char buffer[1024]; unsigned char buffer[1024];
unsigned char output[1024]; unsigned char output[1024];
unsigned char diff;
const cipher_info_t *cipher_info; const cipher_info_t *cipher_info;
const md_info_t *md_info; const md_info_t *md_info;
@ -476,7 +477,12 @@ int main( int argc, char *argv[] )
goto exit; goto exit;
} }
if( memcmp( digest, buffer, md_get_size( md_info ) ) != 0 ) /* Use constant-time buffer comparison */
diff = 0;
for( i = 0; i < md_get_size( md_info ); i++ )
diff |= digest[i] ^ buffer[i];
if( diff != 0 )
{ {
fprintf( stderr, "HMAC check failed: wrong key, " fprintf( stderr, "HMAC check failed: wrong key, "
"or file corrupted.\n" ); "or file corrupted.\n" );