commit 312da33ef121dcbaad3dee049f7b34243aead792
author Paul Bakker <p.j.bakker@polarssl.org> Fri Jun 13 17:20:13 2014 +0200
committer Paul Bakker <p.j.bakker@polarssl.org> Tue Jul 08 18:28:52 2014 +0200
tree 5b864d1aaca37ffff03d3e46ef10557b701ed8cf
parent 1b08bd9525e9c880dd05873831b38844d0d8c8d6

Introduce polarssl_zeroize() instead of memset() for zeroization

library/gcm.c

diff --git a/library/gcm.c b/library/gcm.c
index ba42fd0..e9c37fe 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -54,6 +54,11 @@
 }
 #endif
 
+/* Implementation that should never be optimized out by the compiler */
+static void polarssl_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
 static void gcm_gen_table( gcm_context *ctx )
 {
     int i, j;
@@ -322,7 +327,7 @@
     if( memcmp( check_tag, tag, tag_len ) == 0 )
         return( 0 );
 
-    memset( output, 0, length );
+    polarssl_zeroize( output, length );
 
     return( POLARSSL_ERR_GCM_AUTH_FAILED );
 }