commit 2196c7f81cf9b7903def3c7d34d0bcfc11cf286e
author Andres AG <andres.amayagarcia@arm.com> Thu Dec 15 17:01:16 2016 +0000
committer Simon Butcher <simon.butcher@arm.com> Wed Feb 15 23:26:35 2017 +0200
tree 0dbba82660bdf627f5c144103deec317dd2ec73a
parent 747fceb78536d0e205085e04e5f4aa5158e702b5

Fix renegotiation at incorrect times in DTLS

Fix an incorrect condition in ssl_check_ctr_renegotiate() that compared
64 bits of record counter instead of 48 bits as described in RFC 6347
Section 4.3.1. This would cause the function's return value to be
occasionally incorrect and the renegotiation routines to be triggered
at unexpected times.

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 121c135..abad0b3 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -6482,6 +6482,10 @@
  */
 static int ssl_check_ctr_renegotiate( mbedtls_ssl_context *ssl )
 {
+    size_t ep_len = ssl_ep_len( ssl );
+    int in_ctr_cmp;
+    int out_ctr_cmp;
+
     if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ||
         ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING ||
         ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED )
@@ -6489,8 +6493,12 @@
         return( 0 );
     }
 
-    if( memcmp( ssl->in_ctr,  ssl->conf->renego_period, 8 ) <= 0 &&
-        memcmp( ssl->out_ctr, ssl->conf->renego_period, 8 ) <= 0 )
+    in_ctr_cmp = memcmp( ssl->in_ctr + ep_len,
+                        ssl->conf->renego_period + ep_len, 8 - ep_len );
+    out_ctr_cmp = memcmp( ssl->out_ctr + ep_len,
+                          ssl->conf->renego_period + ep_len, 8 - ep_len );
+
+    if( in_ctr_cmp <= 0 && out_ctr_cmp <= 0 )
     {
         return( 0 );
     }
@@ -7231,8 +7239,8 @@
 
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
     conf->renego_max_records = MBEDTLS_SSL_RENEGO_MAX_RECORDS_DEFAULT;
-    memset( conf->renego_period, 0xFF, 7 );
-    conf->renego_period[7] = 0x00;
+    memset( conf->renego_period,     0x00, 2 );
+    memset( conf->renego_period + 2, 0xFF, 6 );
 #endif
 
 #if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)