From 156bd0676312e36f0ec04e943744e8604e78ec8c Mon Sep 17 00:00:00 2001
From: Werner Dittmann <wernerd@java.net>
Date: Wed, 4 Feb 2009 13:32:48 +0000
Subject: [PATCH] Fix handling of roll-over-counter. Sequence numbers are
 unsigned short, thus store them as unsigned short (mask with 0xffff). Add
 missing code to handle replay checks.

---
 .../media/transform/srtp/SRTPCryptoContext.java | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/net/java/sip/communicator/impl/media/transform/srtp/SRTPCryptoContext.java b/src/net/java/sip/communicator/impl/media/transform/srtp/SRTPCryptoContext.java
index 8648e37cd..146595d0b 100755
--- a/src/net/java/sip/communicator/impl/media/transform/srtp/SRTPCryptoContext.java
+++ b/src/net/java/sip/communicator/impl/media/transform/srtp/SRTPCryptoContext.java
@@ -561,7 +561,7 @@ boolean checkReplay(int seqNum)
         }
 
         long guessedIndex = guessIndex( seqNum );
-        long localIndex = (((long)this.roc) << 16 & 0xFFFF) | this.seqNum;
+        long localIndex = ((long)this.roc) << 16 | this.seqNum;
 
         long delta = guessedIndex - localIndex;
         if (delta > 0)
@@ -751,16 +751,25 @@ private long guessIndex(int seqNum)
      */
     private void update(int seqNum)
     {
-        guessIndex(seqNum);
+        long delta = guessIndex(seqNum) - (((long) this.roc) << 16 | this.seqNum);
+
+        /* update the replay bit mask */
+        if( delta > 0 ){
+          replayWindow = replayWindow << delta;
+          replayWindow |= 1;
+        }
+        else {
+          replayWindow |= ( 1 << delta );
+        }
 
         if (seqNum > this.seqNum)
         {
-            this.seqNum = seqNum;
+            this.seqNum = seqNum & 0xffff;  // make short
         }
         if (this.guessedROC > this.roc)
         {
             this.roc = this.guessedROC;
-            this.seqNum = seqNum;
+            this.seqNum = seqNum & 0xffff;  // make short
         }
     }