Vulnerability Development mailing list archives
TCP segments reordering and covert channels
From: Kototama <kototamo () gmail com>
Date: Sat, 05 May 2007 17:57:35 +0200
Hello, The thesis "Covert Channel Analysis and Data Hiding in TCP/IP" (KamranAhsan, 2002) introduced a new covert channel technique for IPsec. Packets sorting is used to convey information. For instance the sequence packet1 packet2 would code 0 while the sequence packet2 packet1 would code 1. The original sequence of the packets is guessed by the receiver with the sequence number of ESP or AH.
The author says that this technique is not applicable to IP or TCP because "the sequence number field and acknowledgement number field point to the number of octets of data and are not directly related to the packet number". In my view, TCP segments can also be reordered. According to RFC 793, a TCP segment is accepted if "RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND"Thus it seems that this technique is also available for TCP. We can guess the original order since sequence numbers are always increasing.
I don't have the time yet to make a POC and I would like your advices. Am I wrong ?
Current thread:
- TCP segments reordering and covert channels Kototama (May 05)
- Re: TCP segments reordering and covert channels Valdis . Kletnieks (May 07)
- Re: TCP segments reordering and covert channels Kototama (May 07)
- Re: TCP segments reordering and covert channels Valdis . Kletnieks (May 07)