The Secure Shell (SSH) Connection Protocol
RFC 4254
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RFC - Proposed Standard
(January 2006; Errata)
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Last updated |
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2015-10-14
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IETF
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plain text
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WG Document
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No shepherd assigned
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IESG state |
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RFC 4254 (Proposed Standard)
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Unknown
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Responsible AD |
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Russ Housley
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Network Working Group T. Ylonen
Request for Comments: 4254 SSH Communications Security Corp
Category: Standards Track C. Lonvick, Ed.
Cisco Systems, Inc.
January 2006
The Secure Shell (SSH) Connection Protocol
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
Secure Shell (SSH) is a protocol for secure remote login and other
secure network services over an insecure network.
This document describes the SSH Connection Protocol. It provides
interactive login sessions, remote execution of commands, forwarded
TCP/IP connections, and forwarded X11 connections. All of these
channels are multiplexed into a single encrypted tunnel.
The SSH Connection Protocol has been designed to run on top of the
SSH transport layer and user authentication protocols.
Ylonen & Lonvick Standards Track [Page 1]
RFC 4254 SSH Connection Protocol January 2006
Table of Contents
1. Introduction ....................................................2
2. Contributors ....................................................3
3. Conventions Used in This Document ...............................3
4. Global Requests .................................................4
5. Channel Mechanism ...............................................5
5.1. Opening a Channel ..........................................5
5.2. Data Transfer ..............................................7
5.3. Closing a Channel ..........................................9
5.4. Channel-Specific Requests ..................................9
6. Interactive Sessions ...........................................10
6.1. Opening a Session .........................................10
6.2. Requesting a Pseudo-Terminal ..............................11
6.3. X11 Forwarding ............................................11
6.3.1. Requesting X11 Forwarding ..........................11
6.3.2. X11 Channels .......................................12
6.4. Environment Variable Passing ..............................12
6.5. Starting a Shell or a Command .............................13
6.6. Session Data Transfer .....................................14
6.7. Window Dimension Change Message ...........................14
6.8. Local Flow Control ........................................14
6.9. Signals ...................................................15
6.10. Returning Exit Status ....................................15
7. TCP/IP Port Forwarding .........................................16
7.1. Requesting Port Forwarding ................................16
7.2. TCP/IP Forwarding Channels ................................18
8. Encoding of Terminal Modes .....................................19
9. Summary of Message Numbers .....................................21
10. IANA Considerations ...........................................21
11. Security Considerations .......................................21
12. References ....................................................22
12.1. Normative References .....................................22
12.2. Informative References ...................................22
Authors' Addresses ................................................23
Trademark Notice ..................................................23
1. Introduction
The SSH Connection Protocol has been designed to run on top of the
SSH transport layer and user authentication protocols ([SSH-TRANS]
and [SSH-USERAUTH]). It provides interactive login sessions, remote
execution of commands, forwarded TCP/IP connections, and forwarded
X11 connections.
The 'service name' for this protocol is "ssh-connection".
Ylonen & Lonvick Standards Track [Page 2]
RFC 4254 SSH Connection Protocol January 2006
This document should be read only after reading the SSH architecture
document [SSH-ARCH]. This document freely uses terminology and
notation from the architecture document without reference or further
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