Test and fix anti-replay functions
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 31be3ca..d48ccf5 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2697,10 +2697,12 @@
/*
* DTLS anti-replay: RFC 6347 4.1.2.6
*
- * - in_window_top is the highest record sequence number seen
- * - the lsb of in_window is set iff in_window_top - 1 has been seen
- * ...
- * the msb of in_window is set iff in_window_top - 64 has been seen
+ * in_window is a field of bits numbered from 0 (lsb) to 63 (msb).
+ * Bit n is set iff record number in_window_top - n has been seen.
+ *
+ * Usually, in_window_top is the last record number seen and the lsb of
+ * in_window is set. The only exception is the initial state (record number 0
+ * not seen yet).
*/
#if defined(POLARSSL_SSL_DTLS_ANTI_REPLAY)
static void ssl_dtls_replay_reset( ssl_context *ssl )
@@ -2730,10 +2732,7 @@
if( rec_seqnum > ssl->in_window_top )
return( 0 );
- if( rec_seqnum == ssl->in_window_top )
- return( -1 );
-
- bit = ssl->in_window_top - rec_seqnum - 1;
+ bit = ssl->in_window_top - rec_seqnum;
if( bit >= 64 )
return( -1 );
@@ -2757,20 +2756,19 @@
uint64_t shift = rec_seqnum - ssl->in_window_top;
if( shift >= 64 )
- ssl->in_window = 0;
+ ssl->in_window = 1;
else
+ {
ssl->in_window <<= shift;
+ ssl->in_window |= 1;
+ }
ssl->in_window_top = rec_seqnum;
}
- else if( rec_seqnum == ssl->in_window_top )
- {
- ; /* Can't happen, but anyway, nothing to do if it happened */
- }
else
{
/* Mark that number as seen in the current window */
- uint64_t bit = ssl->in_window_top - rec_seqnum - 1;
+ uint64_t bit = ssl->in_window_top - rec_seqnum;
if( bit < 64 ) /* Always true, but be extra sure */
ssl->in_window |= (uint64_t) 1 << bit;