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Network Working Group                                  S. Suehring
Internet-Draft                                         Sentry Insurance
Expires February 8, 2004                               J. Salowey
                                                       Cisco Systems
                                                       August 8, 2003


                        SCP/SFTP/SSH URI Format
                 draft-ietf-secsh-scp-sftp-ssh-uri-00.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet Draft will expire on February 8, 2004.


Copyright Notice

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


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.


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].  This specification shall adopt the definitions "port", "host",
   "scheme", "userinfo", and "authority" from RFC 2396.


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SSH URI

   The SSH scheme shall consist of the protocol acronym followed by a
   colon ":" and a double slash "//" in accordance with RFC 2718 [2].

   The first component of the scheme specific portion MAY include
   credentials (userinfo) consisting of a username and optionally also
   including a password.  Including the password in the URL is NOT
   RECOMMENDED.  The username and password components are separated by
   a single colon ":".

   Following the userinfo, 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, port 22 is assumed.  Following the port
   additional parameters may be specified.  These parameters are
   defined in the connection parameters section.

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

SCP and SFTP URI

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

   Both SCP and SFTP URLs 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.  Including the password in the URL is NOT
   RECOMMENDED.  The username and password components are separated by
   a single colon ":".

   Following the userinfo, if present, the at-sign "@" shall precede
   the authority section of the URL.  Optionally, the authority section
   MAY also include the port preceded by a colon ":".  If the port is
   not included, port 22 is assumed.  Following the port additional
   parameters may be specified.  These parameters are defined in the
   connection parameters section.

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



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Parameters

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 (",").

fingerprint

   The fingerprint parameter contains the fingerprint of the host key
   for the host specified in the URL.  The fingerprint is encoded as
   in [3].  This parameter MUST NOT overwrite a key that is already
   configured for the host.  They 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 for a given URL.

cipher

   The cipher parameter indicates an acceptable encryption mechanism to
   use in making the connection.  The value is the string specifying the
   SSH cipher type. This parameter MUST NOT add a mechanism to a
   configured list of default configured acceptable encryption types.
   If this parameter is not specified then the default configured cipher
   list is used.  There may be more than one cipher parameter.

integrity

   The integrity parameter indicates an acceptable data integrity
   mechanism to use in making the connection. The value is the string
   specifying the SSH data integrity type. This parameter MUST NOT add
   a mechanism to a configured list of default configured acceptable
   data integrity types.  If this parameter is not specified then the
   default configured data integrity list is used. There may be more
   than one integrity parameter.

key-xchg

   The key-xchg parameter indicates an acceptable key exchange mechanism
   to use when making the connection.  The value is the string
   specifying the SSH key exchange type. This parameter MUST NOT add a
   mechanism to a configured list of default configured acceptable key
   exchange types.  If this parameter is not specified then the default
   configured key exchange list is used.  There may be more than one
   key-xchg parameter.





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host-key-alg

   The host-key-alg parameter indicates an host key to use when making
   the connection.  The value is the string specifying the SSH host key
   type.  This parameter MUST NOT add a mechanism to a configured list
   of default configured acceptable host key types.  If this parameter
   is not specified then the default configured host key type list is
   used.  There may be more than one host-key-alg parameter.

user-auth

   The user-auth parameter indicates a user authentication mechanism to
   use when making the connection.  The value is the string specifying
   the SSH user authentication mechanism type. This parameter MUST NOT
   add a mechanism to a configured list of default configured
   acceptable user authentication mechanism types.  If this parameter
   is not specified then the default configured user authentication
   mechanism type list is used.  There may be more than one user-auth
   parameter.

SFTP Parameters

   The SFTP parameters determine how to handle the file transfer
   character translation.

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".

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.


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=c1:b1:30:29:d7:b8:de:6c
          :97:77:10:d7:46:41:63:87,cipher=aes-cbc

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

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


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      sftp://joeuser@example.com:2222;fingerprint=c1:b1:30:29:d7:b8
          :de:6c:97:77:10:d7:46:41:63:87,cipher=
          aes-cbc/pub/docs/test.txt;typecode=a


Security Considerations

   In general, URIs themselves have no security considerations.
   However, since the password for each scheme can optionally be
   included within the URL it should be noted that doing so poses a
   security risk.  Since URLs 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.

   The fingerprint should only be used to validate the host key only if
   the URL can be determined to be authentic from a trusted entity.
   For example, the URL may be received through secure email or HTTPS
   from a trusted and verifiable source.  It is possible that the SSH
   implementation may not be able to determine if the URL is authentic
   in which case it SHOULD prompt the user to either allow or disallow
   the connection based on the information provided.  The SSH
   implementation MUST NOT overwrite a currently configured public key
   based on the URL alone.

   The other connection parameters MUST NOT add any mechanism to the
   list of configured acceptable mechanisms defined in the SSH client.

Normative References

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

   [2] Masinter, L., et. al., "Guidelines for new URL Schemes", RFC
   2718, November 1999.

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

Non-Normative References

   Mealling, M., Denenberg, R., "Report from the Joint 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

   Steve Suehring
   Sentry Insurance
   1800 North Point Dr, G2/61-17
   Stevens Point, WI 54481
   suehring@braingia.com

   Joseph Salowey
   Cisco Systems
   2901 Third Avenue
   Seattle, WA 98121
   E-mail: jsalowey@cisco.com


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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















































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