The branch master has been updated
via bb83c8796b9e708a881f7c49a2af7921e73b2298 (commit)
from dae9e15d74df2f216b277c8887afe2976cba9c6e (commit)
- Log -----------------------------------------------------------------
commit bb83c8796b9e708a881f7c49a2af7921e73b2298
Author: Andy Polyakov <[email protected]>
Date: Thu May 26 21:40:09 2016 +0200
bn/bn_exp.c: explain 'volatile' in MOD_EXP_CTIME_COPY_FROM_PREBUF.
Reviewed-by: Tim Hudson <[email protected]>
-----------------------------------------------------------------------
Summary of changes:
crypto/bn/bn_exp.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 25c05fa..d334cf7 100644
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -527,6 +527,14 @@ static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int
top,
{
int i, j;
int width = 1 << window;
+ /*
+ * We declare table 'volatile' in order to discourage compiler
+ * from reordering loads from the table. Concern is that if
+ * reordered in specific manner loads might give away the
+ * information we are trying to conceal. Some would argue that
+ * compiler can reorder them anyway, but it can as well be
+ * argued that doing so would be violation of standard...
+ */
volatile BN_ULONG *table = (volatile BN_ULONG *)buf;
if (bn_wexpand(b, top) == NULL)
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