One document matched: draft-ietf-secsh-scp-sftp-ssh-uri-01.txt
Differences from draft-ietf-secsh-scp-sftp-ssh-uri-00.txt
Network Working Group
Internet Draft S. Suehring
Document: draft-ietf-secsh-scp-sftp-ssh-uri- Sentry Insurance
01.txt J. Salowey
Cisco Systems
Expires: April 2004 October 2003
SCP/SFTP/SSH URI Format
draft-ietf-secsh-scp-sftp-ssh-uri-01.txt
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026.
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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.
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Table of Contents
1. General Syntax.................................................2
1.1 SSH URI....................................................2
1.2 SCP and SFTP URI...........................................2
2. Parameters.....................................................3
2.1 SSH connection parameters..................................3
2.2 SFTP Parameters............................................4
3. Examples.......................................................4
4. Security Considerations........................................4
Normative References..............................................5
Non-Normative References..........................................6
Author Information................................................6
1. 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.
1.1 SSH URI
The SSH scheme shall consist of the protocol acronym followed by a
colon ":" and a double slash "//" in accordance with RFC 2718.
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, 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 "@" ] host [ ":" port ]
[;conn-parameter=value]
1.2 SCP and SFTP URI
For SCP and SFTP, the scheme portion (scp: or sftp:) is followed by a
double slash "//".
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SCP/SFTP/SSH URI Format October 2003
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, 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 "@" ] 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]
The URIs for SFTP and SCP are hierarcical URIs where each component
of the abs_path consists of path elements separated by a '/'. This is
the same format as used in the FTP URL described in section 2.2.2 of
[5].
2. Parameters
2.1 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 (",").
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 is host public key algorithm
defined [4] and the fingerprint format is defined in [2].
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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 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.
3. 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
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. Security Considerations
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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.
Care must also be taken in handling fingerprints associated with URLs
because URLs transmitted or stored without protection may be modified
by an attacker. In general an implementation cannot determine the
source of a URL so a fingerprint received in a URL 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. 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 for external validation before allowing
a connection based on this information. If the client chooses to make
a connection based on the URL information and it finds that the
public key in the URL 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 and 8.2.4 of [3] provide a good
discussion of handling public keys received in the SSH protocol.
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] Ylonen, T., "SSH Protocol Architecture",
http://www.ietf.org/internet-drafts/draft-ietf-secsh-architecture-
14.txt, work in progreess
[4] Ylonen, T., "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 in progress
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Non-Normative References
Masinter, L., et. al., "Guidelines for new URL Schemes", RFC 2718,
November 1999.
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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