commit 79f1ff84edc219a6b3506df93763583086322e5e
author Manuel Pégourié-Gonnard <mpg@elzevir.fr> Mon Oct 28 12:51:32 2013 +0100
committer Paul Bakker <p.j.bakker@polarssl.org> Mon Jul 07 14:07:23 2014 +0200
tree ae97cc48fcf30d743bd7430f12091b574da9e757
parent 2a8c2881f4158b018011eaa77ab8cfb8761389a5

Make all hash checking in programs constant-time

programs/hash/sha1sum.c

diff --git a/programs/hash/sha1sum.c b/programs/hash/sha1sum.c
index 92f8406..c20323d 100644
--- a/programs/hash/sha1sum.c
+++ b/programs/hash/sha1sum.c
@@ -81,6 +81,7 @@
     int nb_tot1, nb_tot2;
     unsigned char sum[20];
     char buf[41], line[1024];
+    char diff;
 
     if( ( f = fopen( filename, "rb" ) ) == NULL )
     {
@@ -121,7 +122,12 @@
         for( i = 0; i < 20; i++ )
             sprintf( buf + i * 2, "%02x", sum[i] );
 
-        if( memcmp( line, buf, 40 ) != 0 )
+        /* Use constant-time buffer comparison */
+        diff = 0;
+        for( i = 0; i < 40; i++ )
+            diff |= line[i] ^ buf[i];
+
+        if( diff != 0 )
         {
             nb_err2++;
             fprintf( stderr, "wrong checksum: %s\n", line + 42 );