The Secure Shell (SSH) Connection Protocol
RFC 4254
Document | Type |
RFC - Proposed Standard
(January 2006; Errata)
Updated by RFC 8308
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Authors | Chris Lonvick , Tatu Ylonen | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4254 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Russ Housley | ||
Send notices to | (None) |
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 explanation. 2. Contributors The major original contributors of this set of documents have been: Tatu Ylonen, Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH Communications Security Corp), and Markku-Juhani O. SaarinenShow full document text