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TCP Stealth
draft-kirsch-ietf-tcp-stealth-00

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Last updated: 2014-08-14
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Internet Engineering Task Force                                J. Kirsch
Internet-Draft                                               C. Grothoff
Intended status: Informational                                 TU Munich
Expires: February 16, 2015                                  J. Appelbaum
                                                        Tor Project Inc.
                                                            H. Kenn, Ed.
                                              Microsoft Deutschland GmbH
                                                         August 15, 2014

                              TCP Stealth
                    draft-kirsch-ietf-tcp-stealth-00

Abstract

   TCP servers are visible on the Internet to unauthorized clients, as
   the existence of a TCP server is leaked in the TCP handshake before
   applications have a chance to authenticate the client.

   We present a small modification to the initial TCP handshake that
   allows TCP clients to replace the TCP ISN in the TCP SYN packet with
   an authorization token.  Based on this information, TCP servers may
   then chose to obscure their presence from unauthorized TCP clients.

   This RFC documents the specific method for calculating the
   authorization token to ensure interoperability and to minimize
   interference by middleboxes.  Mandating support for this method in
   operating system TCP/IP implementation will ensure that clients can
   connect to TCP servers protected by this method.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 16, 2015.

Kirsch, et al.          Expires February 16, 2015               [Page 1]
Internet-Draft                 TCP Stealth                   August 2014

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions Used in This Document . . . . . .   3
   3.  Description of the TCP Stealth Option . . . . . . . . . . . .   4
     3.1.  32-bit Access Authorization . . . . . . . . . . . . . . .   4
       3.1.1.  Test Vectors  . . . . . . . . . . . . . . . . . . . .   4
     3.2.  16-bit Access Authorization and 16-bit Payload Protection   5
       3.2.1.  Test Vectors  . . . . . . . . . . . . . . . . . . . .   5
   4.  Timestamps and TCP SYN Retransmits  . . . . . . . . . . . . .   6
   5.  TCP Stealth and TCP SYN Cookies . . . . . . . . . . . . . . .   6
   6.  Integraton with Applications  . . . . . . . . . . . . . . . .   6
   7.  Middlebox Considerations  . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   As it has been shown in [ZMAP], it is feasible today to perform a
   port scan on all Internet hosts in less than an hour and specialized
   search engines perform such port scans regularily.  At the same time,
   security issues in server implementations are exploited by various
   parties for espionage and commercial gain.  Thus, it is increasingly
   important to minimize the visible footprint of services on Internet
   hosts, thereby reducing the attack surface.

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