IUTF8 Terminal Mode in Secure Shell (SSH)
RFC 8160

Document Type RFC - Proposed Standard (April 2017; No errata)
Last updated 2017-04-19
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Internet Engineering Task Force (IETF)                         S. Tatham
Request for Comments: 8160                                         PuTTY
Category: Standards Track                                      D. Tucker
ISSN: 2070-1721                                                  OpenSSH
                                                              April 2017

               IUTF8 Terminal Mode in Secure Shell (SSH)

Abstract

   This document specifies a new opcode in the Secure Shell terminal
   modes encoding.  The new opcode describes the widely used IUTF8
   terminal mode bit, which indicates that terminal I/O uses UTF-8
   character encoding.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8160.

Copyright Notice

   Copyright (c) 2017 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.

Tatham & Tucker              Standards Track                    [Page 1]
RFC 8160               IUTF8 Terminal Mode in SSH             April 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  New IUTF8 Opcode for Terminal Mode Encoding . . . . . . . . .   2
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   3
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   The Secure Shell (SSH) connection protocol [RFC4254] provides an
   encoding for terminal modes, used in the "pty-req" channel request
   type.

   A commonly used terminal mode is IUTF8, which indicates that the
   terminal driver should assume that terminal I/O uses the UTF-8
   character encoding [RFC3629].  This is typically used by the kernel's
   terminal driver on the server to decide how many bytes of input to
   treat as a single logical character during line editing.

   SSH does not currently provide an encoding for IUTF8.  This document
   specifies one.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  New IUTF8 Opcode for Terminal Mode Encoding

   The opcode value 42 is defined for the IUTF8 terminal mode.

   As specified in Section 8 of [RFC4254], all opcodes in the range 1 to
   159 have a single uint32 argument; therefore, the IUTF8 opcode is
   followed by a single uint32 argument.  The value 0 indicates that the
   IUTF8 mode is disabled, and the value 1 indicates that it is enabled.

   As with all other encoded terminal modes, the client SHOULD transmit
   a value for this mode if it knows about one, and the server MAY
   ignore it.

Tatham & Tucker              Standards Track                    [Page 2]
RFC 8160               IUTF8 Terminal Mode in SSH             April 2017

4.  IANA Considerations

   This document augments the list of "Pseudo-Terminal Encoded Terminal
   Modes" defined in Section 8 of [RFC4254].

   IANA has added the following opcode to the "Pseudo-Terminal Encoded
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