Network Working Group
   Internet Draft                                        S. Suehring
   Document: draft-ietf-secsh-scp-sftp-ssh-uri-        Sentry Insurance
   01.txt
Internet-Draft
Expires: December 16, 2005                                    J. Salowey
                                                           Cisco Systems
   Expires: April 2004                                     October 2003
                                                           June 14, 2005

                        SCP/SFTP/SSH URI Format
                 draft-ietf-secsh-scp-sftp-ssh-uri-01.txt
                draft-ietf-secsh-scp-sftp-ssh-uri-02.txt

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Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved. (2005).

Abstract

   This document describes the Uniform Resource Identifiers used to
   locate resources for the SCP, SFTP, and SSH protocols.  The document
   describes the generic syntax involved in URI definitions as well as
   specific definitions for each protocol.  These specific definitions
   may include user credentials such as username and password and also
   may include other parameters such as fingerprint.  In addition,
   security considerations and examples are also provided within this
   document.

                        SCP/SFTP/SSH URI Format           October 2003

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  General Syntax.................................................2
      1.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1   SSH URI....................................................2
      1.2 URI  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2   SCP and SFTP URI...........................................2
   2. Parameters.....................................................3
      2.1 URI . . . . . . . . . . . . . . . . . . . . .  3
   3.  Parameters . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1   SSH connection parameters..................................3
      2.2 parameters  . . . . . . . . . . . . . . . .  4
     3.2   SFTP Parameters............................................4
   3. Examples.......................................................4 Parameters  . . . . . . . . . . . . . . . . . . . . .  5
   4.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Security Considerations........................................4 Considerations  . . . . . . . . . . . . . . . . . . .  6
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     6.1   Normative References..............................................5
   Non-Normative References..........................................6
   Author Information................................................6 References . . . . . . . . . . . . . . . . . . .  6
     6.2   Informative References . . . . . . . . . . . . . . . . . .  7
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  7
       Intellectual Property and Copyright Statements . . . . . . . .  8

1.  Introduction

   This document describes the Uniform Resource Identifiers (URIs) to be
   used with the SSH, SCP, and SFTP protocols.

2.  General Syntax

   The URI for each protocol shall consist of the scheme and the scheme
   specific portion separated by a colon ":", as discussed in RFC 2396
   [1]. [RFC3986]
   This specification shall adopt the definitions "port", "host",
   "scheme", "userinfo", and "authority" from RFC 2396.

1.1 [RFC3986].

2.1  SSH URI

   The SSH scheme shall consist of the protocol acronym followed by a
   colon ":" and a double slash "//" in accordance with RFC 2718. [RFC2718].

   The first component of the scheme specific portion MAY include
   credentials (userinfo) consisting of a username and optionally also
   including a password. password, separated by a colon ":".  Including the
   password in the URL URI is NOT
   RECOMMENDED.  The username RECOMMENDED and password components is deprecated in
   accordance with [RFC3986]

   One or more optional connection parameters (conn-parameters) may be
   specified within the userinfo section of the URI.  These conn-
   parameters are separated from the credentials by a
   single colon ":". semi-colon ";" and
   from each other by a comma ",".

   Following the userinfo, if present, and the conn-parameters, if
   present the at-sign "@" shall precede the authority section of the
   URI.  Optionally, the authority section MAY also include the port
   preceded by a colon ":".  If the port is not included, the default
   port is assumed.  Following the port additional
   parameters may be specified.  These parameters are defined in the
   connection parameters section.

   ssh_URI = "ssh://" [ userinfo ] [ ";"conn-parameter=value ] [ "@" ]
        host [ ":" port ]
         [;conn-parameter=value]

1.2

2.2  SCP and SFTP URI

   For SCP and SFTP, the scheme portion (scp: or sftp:) is followed by a
   double slash "//".

                        SCP/SFTP/SSH URI Format           October 2003

   Both SCP and SFTP URLs URIs are terminated by a single slash "/" followed
   by the path information to the requested resource.

   The first component of the scheme specific portion MAY include
   credentials (userinfo) consisting of a username and optionally also
   including a password. password, separated by a colon ":".  Including the
   password in the URL URI is NOT
   RECOMMENDED.  The username RECOMMENDED and password components is deprecated in
   accordance with [RFC3986]

   One or more optional connection parameters (conn-parameters) may be
   specified within the userinfo section of the URI.  These conn-
   parameters are separated from the credentials by a
   single colon ":". semi-colon ";" and
   from each other by a comma ",".

   Following the userinfo, if present, and the conn-parameters, if
   present the at-sign "@" shall precede the authority section of the URL.
   URI.  Optionally, the authority section MAY also include the port
   preceded by a colon ":".  If the port is not included, the default
   port is assumed.  Following the port additional
   parameters may be specified.  These parameters are defined in the
   connection parameters section.

   scp_URI = "scp://" [userinfo ] [ ";"conn-parameter=value ] [ userinfo "@" ]
        host [ ":" port ]
         [ ; parameter = value ] [ abs_path [abs_path ]

   Following the port additional parameters may be specified.  These
   parameters are defined in the connection parameters section.
   Following the path additional sftp specific parameters may be
   specified.

   sftp_URI = "sftp://" [ userinfo ] [ ";"conn-parameter=value] [ "@" ]
        host [ ":" port ]
         [;conn-parameter=value] [ abs_path ] [;sftp-parameter=value] [ ";"sftp-parameter=value ]

   The URIs for SFTP and SCP are hierarcical hierarchical URIs where each component
   of the abs_path consists of path elements separated by a '/'.  This
   formatting is meant to represent the same format path information as used in the FTP URL described in section 2.2.2 Section 5
   of
   [5].

2. [I-D.ietf-secsh-filexfer].

3.  Parameters

2.1

3.1   SSH connection parameters

   The following parameters are associated with an SSH connection and
   are applicable to SSH, SFTP and SCP.  All parameters are optional and
   MUST NOT overwrite configured defaults.  Individual parameters are
   separated by a comma (",").  Additional parameters MAY be used.

   fingerprint

      The fingerprint parameter contains the fingerprint of the host key
      for the host specified in the URL.  The fingerprint is encoded as
   host-key-alg:fingerprint.
      host-key-alg-fingerprint.  Host-key-alg is host public key
      algorithm defined [4] in [I-D.ietf-secsh-transport] and the
      fingerprint format is defined [I-D.ietf-secsh-publickeyfile].  For use in
      a URI, the fingerprint shall use a single dash "-" as a separator
      instead of the colon ":" as described in [2].

                        SCP/SFTP/SSH URI Format           October 2003 [I-D.ietf-secsh-
      publickeyfile].  This parameter MUST NOT overwrite a key that is
      already configured for the host.  The fingerprint MAY be used to
      validate the authenticity of the host key if the URL was obtained
      from an authenticated source with its integrity protected.  If
      this parameter is not included then the validity of the host key
      is validated using another method.  See Security Considerations
      section for additional considerations.  There MUST be only one
      fingerprint parameter per host-key-alg for a given URL.

2.2

3.2  SFTP Parameters

   The SFTP parameters determine how to handle the file transfer
   character translation.  Additional parameters MAY be used.

   newline

      The newline parameter determines how the server translates new
      line indicators.  The possible choices are usually "\r" or "\n" or "\r\n".
   The default is "\r\n". CRLF and implemented in
      accordance with Section 4.3 of [I-D.ietf-secsh-filexfer].

   typecode

      The typecode identifies the type of file which determines how it
      will be treated.  Possible values are "i" for binary files, "a"
      for text files, and "d" for directory listings.

3.

4.  Examples

   The following section shows basic examples of URLs for each protocol.
   This section should not be considered to include all possible
   combinations of URLs for each protocol.

   ssh://user@host

   ssh://user@host:2222

         ssh://joeuser@example.com;fingerprint=ssh-dss:c1:b1:30:29:d7:b8
             :de:6c:97:77:10:d7:46:41:63:87

         scp://user:password@host/file.txt

   ssh://user;fingerprint=ssh-dss-c1-b1-30-29-d7-b8-de-6c-97-
        77-10-d7-46-41-63-87@example.com

   scp://user@host.example.com/file.txt

   sftp://user@host/dir/path/file.txt

         sftp://joeuser@example.com:2222;fingerprint=ssh-dss:c1:b1:30
             :29:d7:b8:de:6c:97:77:10:d7:46:41:63:87,

4.

   sftp://user;newline=CR,fingerprint=ssh-dss-c1-b1-30-29-d7-b8-de
        -6c-97-77-10-d7-46-41-63-87@example.com:2222/

5.  Security Considerations

                        SCP/SFTP/SSH URI Format           October 2003

   In general, URIs themselves have no security considerations.
   However, since the password for each scheme can optionally be
   included within the URL URI it should be noted that doing so poses a
   security risk.  Since URLs URIs are usually sent in the clear with no
   encryption or other security, any password or other credentials
   (userinfo) included could be seen by a potential attacker.

   Care must also be taken in handling fingerprints associated with URLs URIs
   because URLs URIs transmitted or stored without protection may be modified
   by an attacker.  In general an implementation cannot determine the
   source of a URL URI so a fingerprint received in a URL URI should have no
   more trust associated with it than a raw public key received in the
   SSH protocol itself.  If a locally configured key exists for the
   server already it MUST NOT be automatically overwritten with
   information from the URL. URI.  If the host is unknown then the
   implementation should treat the fingerprint received with the same
   caution that it does with any unknown public key.  The client MAY
   offer the fingerprint and URL URI for external validation before allowing
   a connection based on this information.  If the client chooses to
   make a connection based on the URL URI information and it finds that the
   public key in the URL URI and the public key offered by the server do not
   match then it SHOULD provide a warning and provide a means to abort
   the connection.  Sections 3.1 4.1 and 8.2.4 9.2.4 of [3] [I-D.ietf-secsh-
   architecture] provide a good discussion of handling public keys
   received in the SSH protocol.

6.  References

6.1  Normative References

   [1] Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource
      Identifiers (URI): Generic Syntax", RFC 2396, August 1998.

   [2] Markus Friedl, "SSH Fingerprint Format",
   http://www.ietf.org/internet-drafts/draft-ietf-secsh-fingerprint-
   01.txt, work in progress

   [3]

   [I-D.ietf-secsh-architecture]
              Ylonen, T., T. and C. Lonvick, "SSH Protocol Architecture",
   http://www.ietf.org/internet-drafts/draft-ietf-secsh-architecture-
   14.txt, work
              draft-ietf-secsh-architecture-22 (work in progreess

   [4] Ylonen, T., progress),
              March 2005.

   [I-D.ietf-secsh-filexfer]
              Galbraith, J., "SSH File Transfer Protocol",
              draft-ietf-secsh-filexfer-09 (work in progress),
              June 2005.

   [I-D.ietf-secsh-publickeyfile]
              Galbraith, J. and R. Thayer, "SSH Public Key File Format",
              draft-ietf-secsh-publickeyfile-08 (work in progress),
              April 2005.

   [I-D.ietf-secsh-transport]
              Lonvick, C., "SSH Transport Layer Protocol",
   http://www.ietf.org/internet-drafts/draft-ietf-secsh-transport-
   16.txt, work in progress

   [5] Hoffman, P., Definitions of Early URI Schemes",
   http://www.ietf.org/internet-drafts/draft-hoffman-rfc1738bis-00.txt,
    work
              draft-ietf-secsh-transport-24 (work in progress

                        SCP/SFTP/SSH URI Format           October 2003

Non-Normative References progress),
              March 2005.

   [RFC2718]  Masinter, L., et. al., Alvestrand, H., Zigmond, D., and R. Petke,
              "Guidelines for new URL Schemes", RFC 2718, November 1999.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

6.2  Informative References

   [RFC3305]  Mealling, M., M. and R. Denenberg, R., "Report from the Joint W3C/IETF W3C/
              IETF URI Planning Interest Group: Uniform Resource
              Identifiers (URIs), URLs, and Uniform Resource Names
              (URNs): Clarifications and Recommendations", RFC 3305,
              August 2002.

Author Information

Authors' Addresses

   Steve Suehring
   Sentry Insurance
   1800 North Point Dr, G2/61-17
   PO BOX 1033
   Stevens Point, WI  54481
   US

   Email: suehring@braingia.com

   Joseph Salowey
   Cisco Systems
   2901 Third Avenue 3rd Ave
   Seattle, WA  98121
   E-mail:
   US

   Email: jsalowey@cisco.com

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                        SCP/SFTP/SSH URI Format           October 2003

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