Network Working Group D. Moffat Internet-Draft Sun Microsystems Expires: June 10, 2002 December 10, 2001 SSH Agent Forwarding draft-ietf-secsh-agent-00.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 June 10, 2002. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract SSH is a protocol for secure remote login and other secure network services over an insecure network. One of the common authentication mechanisms used with SSH is public key. This document describes the authentication agent forwarding protocol, which runs as a channel over [SSH-TRANS] it is designed to ensure that the sensitive private keys never leave the users control even when using SSH to login over multiple hops. Moffat Expires June 10, 2002 [Page 1] Internet-Draft SSH Agent Forwarding December 2001 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Agent Operations . . . . . . . . . . . . . . . . . . . . . . . 3 2. Security Considerations . . . . . . . . . . . . . . . . . . . 3 3. Additional Information . . . . . . . . . . . . . . . . . . . . 4 References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 4 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 5 Moffat Expires June 10, 2002 [Page 2] Internet-Draft SSH Agent Forwarding December 2001 1. Introduction This protocol is designed to facilitate an ad hoc secure single sign on mechanism using the SSH protocol. A typical scenario is that a user has their private keys stored on their laptop (host A) and uses the SSH protocol to remotely connect to their corporate VPN (host B) access point. Then uses further SSH connections to reach a specific host (host C) within the enterprise network. Without agent forwarding the user is required to have a copy of their private key on host A and host B so that the connection to host C can be made using public key authentication. The key pairs used for the host A to B and the host B to C connection maybe the same but this is not always the case. This presents a security risk since the users private key(s) must be stored on host B which is likely to be a host the end user is not in control of even though they do trust it. It is likely that the private keys on host A and host B are stored in an encrypted format, this means the user has at least two passwords to enter to make the connection from A to C. Ideally the private keys should remain on a device in the direct control of the end user (host A in this example) and all encryption and signing operations involving the private key should be performed on this device, regardless of the location of the entity requesting the operation. 1.1 Agent Operations The following interactions with the agent are requried: ADD, DELETE, LIST, SIGN. An agent implementation MUST support requests to forward operations using all public key types, defined in [SSH-USERAUTH] even those that the implementation doesn't support natively. 2. Security Considerations This protocol is designed only to run as a channel of the SSH protocol. The goal of this extension is to ensure that the users private keys never leave the machine they are physically at. Ideally the private keys should be stored on a password protected removable media such as a smartcard. Moffat Expires June 10, 2002 [Page 3] Internet-Draft SSH Agent Forwarding December 2001 3. Additional Information The current document editor is: Darren.Moffat@Sun.COM. Comments on this internet draft should be sent to the IETF SECSH working group, details at: http://ietf.org/html.charters/secsh-charter.html References [FIPS-186] Federal Information Processing Standards Publication, ., "FIPS PUB 186, Digital Signature Standard", May 1994. [SSH-ARCH] Ylonen, T., "SSH Protocol Architecture", I-D draft- ietf-architecture-11.txt, July 2001. [SSH-TRANS] Ylonen, T., "SSH Transport Layer Protocol", I-D draft-ietf-transport-11.txt, July 2001. [SSH-USERAUTH] Ylonen, T., "SSH Authentication Protocol", I-D draft- ietf-userauth-13.txt, July 2001. [SSH-CONNECT] Ylonen, T., "SSH Connection Protocol", I-D draft- ietf-connect-14.txt, July 2001. Author's Address Darren J Moffat Sun Microsystems 901 San Antonio Road Palo Alto 94303 USA EMail: Darren.Moffat@Sun.COM Moffat Expires June 10, 2002 [Page 4] Internet-Draft SSH Agent Forwarding December 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. 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