Secure Shell Working Group J. Galbraith Internet-Draft VanDyke Software Expires: February 17, 2004 P. Remaker Cisco Systems, Inc August 19, 2003 # 訳者 春山征吾 haruyama@unixuser.org # 英語が酷いよ Session Channel Break Extension draft-ietf-secsh-break-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 17, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract The Session Channel Break Extension provides a means to send a BREAK signal [2] over an SSH terminal session [5]. Galbraith & Remaker Expires February 17, 2004 [Page 1] Internet-Draft Session Channel Break Extension August 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. The Break Request . . . . . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 Normative References . . . . . . . . . . . . . . . . . . . . . . 7 Informative References . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . 9 Galbraith & Remaker Expires February 17, 2004 [Page 2] Internet-Draft Session Channel Break Extension August 2003 1. Introduction 1. イントロダクション The SSH session channel provides a mechanism for the client-user to interactively enter commands and receive output from a remote host while taking advantage of the SSH transport's privacy and integrity features. SSH is increasingly being used to replace telnet for terminal access applications. SSH セッションチャンネルは クライアント-ユーザが SSH トランスポートの秘密性と完全性の特徴を利用しながら インタラクティブにコマンドを入力したりリモートホストからの出力を受けとる メカニズムを提供する. SSH は ターミナルアクセスアプリケーションとして telnet を置き換えてますます利用されている. A common application of the telnet protocol is the "Console Server" [2] whereby a telnet NVT can be connected to a physical RS-232/V.24 asynchronous port, making the telnet NVT appear as a locally attached terminal to that port, and making that physical port appear as a network addressable device. A number of major computer equipment vendors provide high level administrative functions through an asynchronous serial port and generally expect the attached terminal to be capable of send a BREAK signal. telnet プロトコルの共通アプリケーションに telnet NVT を物理的な RS-232/V.24 非同期ポートに接続させて telnet NVT をそのポートにローカルに結びつけたターミナルのように みせ, その物理的なポートをネットワーク的に指定可能なデバイスとして みせる "Console Server"[2] がある. 多数のメジャーな計算機機器ベンダが 非同期のシリアルポートを通した高レベルの管理機能を提供しており 一般的に結びつけたターミナルに BREAK シグナルを送ることが可能であると 期待している. A BREAK signal is defined as the TxD signal being held in a SPACE ("0") state for a time greater than a whole character time. In practice, a BREAK signal is typically 250 to 500 ms in length. BREAK シグナルとは 全体のキャラクタ時間よりも長い時間 SPACE ("0") 状態を保持させる TxD シグナルとして定義されている. 実際には BREAK シグナルは典型的に長さにして 250 から 500 ms である. ###http://www.linux.or.jp/JM/html/LDP_man-pages/man3/termios.3.html tcsendbreak () は端末が非同期のシリアルデータ転送を用いている場合に, 連続した 0 のビット列を一定間隔で転送する. duration が 0 の場合は, 0 のビットを 0.25 秒以上, 0.5 秒以下の間隔で転送する. duration が 0 でない場合は, 0 のビットを実装依存の時間間隔で送る. ### The telnet protocol furnishes a means to send a "BREAK" signal, which RFC0854 defines as a "a signal outside the USASCII set which is currently given local meaning within many systems." [1] Console Server vendors interpret the TELNET BREAK signal as a physical BREAK signal, which can then allow access to the full range of adminisrative functions available on an asynchronous serial console port. telnet プロトコルは, RFC0854 が次のように定義している,"多くのシステムで現在ローカルな意味を 与えられている USASCII セットの外にあるシグナル", "BREAK" シグナルを送る手段を備えている. コンソールサーバベンダは TELNET BREAK シグナルを物理的な BREAK シグナルだと解釈する. 物理的な BREAK シグナルは非同期のシリアルコンソールポートで 管理機能のすべての範囲を有効にする アクセスを許すことができる. The lack of a similar facility in the SSH session channel has forced users to continue the use of telnet for the "Console Server" function. SSH セッションチャンネルで同様な機能が欠如していることは, "Console Server" 機能のためにユーザに telnet を使用することを強いている. Galbraith & Remaker Expires February 17, 2004 [Page 3] Internet-Draft Session Channel Break Extension August 2003 2. The Break Request 2. Break 要求 The following following channel specific request can be sent to request that the remote host perform a BREAK operation. 次のチャンネル特有のリクエストは リモートホストで BREAK 操作を 実行するのに送られる. byte SSH_MSG_CHANNEL_REQUEST uint32 recipient channel string "break" boolean want_reply uint32 break-length in milliseconds If the BREAK length cannot be controlled by the application receiving this request, the BREAK length parameter SHOULD be ignored and the default BREAK signal length of the chipset or underlying chipset driver SHOULD be sent. BREAK length がこのリクエストを受けとるアプリケーションで 制御されない場合, BREAK length パラメータは無視される必要があり チップセットや下にあるチップセットドライバのデフォルトの BREAK signal length が送られる必要がある. If the application receiving this request can control the BREAK-length, the following suggestions are made regarding BREAK duration. If a BREAK duration request of greater than 3000ms is received, it SHOULD be processed as a 3000ms BREAK, in order to prevent an unreasonably long BREAK request causing the port to become unavailable for as long as 49.7 days while executing the BREAK. Applications that require a longer BREAK may choose to ignore this requirement. If BREAK duration request of less than 500ms, is requested a BREAK of 500ms SHOULD be sent since most devices will recognize a BREAK of that length. In the event that an application needs a shorter BREAK, this suggestion can be ignored. If the BREAK-length parameter is 0, the BREAK SHOULD be sent as 500ms or the default BREAK signal length of the chipset or underlying chipset driver. このリクエストを受けとったアプリケーションが BREAK-length を制御できるなら BREAK の存続時間に関する以下の示唆が役に立つ. 3000mx よりも 大きい BREAK の存続時間要求を受けとったら, 3000ms の BREAK が実行される 必要がある. これは 合理的でない長い BREAK 要求が BREAK を実行する間に 49.7 日間ポートを利用不可能にさせるのを防ぐためだ. より長い BREAK を必要とするアプリケーションはこの要求を無視することを 選んでもよい. 500ms よりも短かい BREAK の存続期間が要求されたなら, 500ms の BREAK が送られるべきである. 多くのデバイスが BREAK の長さだと認識しているからだ. アプリケーションが より短かい BREAK を必要としている場合, この示唆は無視されるだろう. BREAK-length パラメータが 0 なら BREAK は 500ms ないし チップセットや下にあるチップセットドライバのデフォルトの BREAK signal length が送られる必要がある. If the SSH connection does not terminate on a physical serial port, the BREAK indication SHOULD be handled in an implementation-defined manner consistent with the general use of BREAK as an attention/ interrupt signal; for instance, a service processor could use some other out-of-band facility to get the attention of a system it manages. SSH の接続が物理的なシリアルポートで終了されない場合, BREAK の指示は 注意/割込みのシグナルである BREAK の一般的な使用と 矛盾しない実装定義のマナーで処理される必要がある.例えば サービスプロセッサは, それが管理するシステムの注意をするために 他の別の帯域外の設備を使う可能性がある. In a case where an SSH connection cascades to another connection, the BREAK SHOULD be passed along the cascaded connection. For example, a telnet session from an SSH shell should carry along an SSH initiated BREAK and an SSH client initited from a telnet connection SHOULD pass a BREAK indication from the telnet connection. SSH の接続が他の接続とカスケードしている場合, BREAK は カスケードされた接続を通す必要がある. 例えば, SSH シェルからの telnet セッションは SSH 起源の BREAK を運ぶべきで, telnet 接続から始められた SSH クライアントは telnet 接続からの BREAK 指示を通すべきである. If the want_reply boolean is set, the server MUST reply using SSH_MSG_CHANNEL_SUCCESS or SSH_MSG_CHANNEL_FAILURE [5] messages. If a BREAK of any kind was preformed, SSH_MSG_CHANNEL_SUCCESS MUST be sent. If no BREAK was preformed, SSH_MSG_CHANNEL_FAILURE MUST be Galbraith & Remaker Expires February 17, 2004 [Page 4] Internet-Draft Session Channel Break Extension August 2003 sent. This operation SHOULD be supported by any general purpose SSH client. want_reply ブーリアンがセットされている場合, サーバは SSH_MSG_CHANNEL_SUCCESS or SSH_MSG_CHANNEL_FAILURE [5] メッセージを 使って返答する必要がある.どんな種類の BREAK でも実行されたなら SSH_MSG_CHANNEL_SUCCESS MUST が送られなければならない. BREAK が実行されなかったら, SSH_MSG_CHANNEL_FAILURE が送られなければ ならない Galbraith & Remaker Expires February 17, 2004 [Page 5] Internet-Draft Session Channel Break Extension August 2003 3. Security Considerations 3. セキュリティに関する考察 Many computer systems treat serial consoles as local and secured, and interpret a BREAK signal as an instruction to halt execution of the operating system or to enter priviliged configuration modes. Because of this, extra care should be taken to ensure that SSH access to BREAK-enabled ports are limited to users with appropriate priviliges to execute such functions. Alternatively, support for the BREAK facility MAY be imlemented configurable or a per port or per server basis. 多くの計算機システムはシリアルコンソールをローカルで安全なものとして 扱い, OS の実行を止める ないし 特権を持つ 設定モードへ入る命令として BREAK シグナルを解釈する. このため, BREAK が有効なポートへの SSH のアクセスはそのような機能を 実行する適当な特権を持つユーザに制限されていることを保証する 特別な配慮が払われなければならない. いいかえれば, BREAK 機能のサポートは, 設定可能に ないし ポート単位ないしサーバ単位で 実装してもよい. Implementations that literally intepret the BREAK length parameter without imposing the suggested BREAK time limit may cause a denial of service to or unexpected results from attached devices receiving the very long BREAK signal. 示唆された BREAK 時間の制限を課すことなく BREAK length パラメータ をそのまま解釈する実装は 非常に長い BREAK シグナルを受けとった 結びつけられたデバイスのサービス拒否やデバイスからの期待されない 結果を引き起こすかもしれない. Galbraith & Remaker Expires February 17, 2004 [Page 6] Internet-Draft Session Channel Break Extension August 2003 Normative References [1] Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD 8, RFC 854, May 1983. Galbraith & Remaker Expires February 17, 2004 [Page 7] Internet-Draft Session Channel Break Extension August 2003 Informative References [2] Harris, D., "Greater Scroll of Console Knowledge", April 2003. [3] Rinne, T., Ylonen, T., Kivinen, T. and S. Lehtinen, "SSH Protocol Architecture", draft-ietf-secsh-architecture-14 (work in progress), July 2003. [4] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. Lehtinen, "SSH Transport Layer Protocol", draft-ietf-secsh-transport-16 (work in progress), July 2003. [5] Rinne, T., Ylonen, T., Kivinen, T. and S. Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-17 (work in progress), July 2003. Authors' Addresses Joseph Galbraith VanDyke Software 4848 Tramway Ridge Blvd Suite 101 Albuquerque, NM 87111 US Phone: +1 505 332 5700 EMail: galb-list@vandyke.com Phillip Remaker Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95120 US EMail: remaker@cisco.com Galbraith & Remaker Expires February 17, 2004 [Page 8] Internet-Draft Session Channel Break Extension August 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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