draft-ietf-secsh-scp-sftp-ssh-uri-00.txt   draft-ietf-secsh-scp-sftp-ssh-uri-01.txt 
Network Working Group S. Suehring
Internet-Draft Sentry Insurance Network Working Group
Expires February 8, 2004 J. Salowey Internet Draft S. Suehring
Document: draft-ietf-secsh-scp-sftp-ssh-uri- Sentry Insurance
01.txt J. Salowey
Cisco Systems Cisco Systems
August 8, 2003 Expires: April 2004 October 2003
SCP/SFTP/SSH URI Format SCP/SFTP/SSH URI Format
draft-ietf-secsh-scp-sftp-ssh-uri-00.txt draft-ietf-secsh-scp-sftp-ssh-uri-01.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026. of Section 10 of RFC2026.
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Copyright Notice Copyright Notice
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This document describes the Uniform Resource Identifiers used to This document describes the Uniform Resource Identifiers used to
locate resources for the SCP, SFTP, and SSH protocols. The document locate resources for the SCP, SFTP, and SSH protocols. The document
describes the generic syntax involved in URI definitions as well as describes the generic syntax involved in URI definitions as well as
specific definitions for each protocol. These specific definitions specific definitions for each protocol. These specific definitions
may include user credentials such as username and password and also may include user credentials such as username and password and also
may include other parameters such as fingerprint. In addition, may include other parameters such as fingerprint. In addition,
security considerations and examples are also provided within this security considerations and examples are also provided within this
document. document.
General Syntax SCP/SFTP/SSH URI Format October 2003
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 The URI for each protocol shall consist of the scheme and the scheme
specific portion separated by a colon ":", as discussed in RFC 2396 specific portion separated by a colon ":", as discussed in RFC 2396
[1]. This specification shall adopt the definitions "port", "host", [1]. This specification shall adopt the definitions "port", "host",
"scheme", "userinfo", and "authority" from RFC 2396. "scheme", "userinfo", and "authority" from RFC 2396.
SSH URI 1.1 SSH URI
The SSH scheme shall consist of the protocol acronym followed by a The SSH scheme shall consist of the protocol acronym followed by a
colon ":" and a double slash "//" in accordance with RFC 2718 [2]. colon ":" and a double slash "//" in accordance with RFC 2718.
The first component of the scheme specific portion MAY include The first component of the scheme specific portion MAY include
credentials (userinfo) consisting of a username and optionally also credentials (userinfo) consisting of a username and optionally also
including a password. Including the password in the URL is NOT including a password. Including the password in the URL is NOT
RECOMMENDED. The username and password components are separated by RECOMMENDED. The username and password components are separated by a
a single colon ":". single colon ":".
Following the userinfo, if present, the at-sign "@" shall Following the userinfo, if present, the at-sign "@" shall precede the
precede the authority section of the URI. Optionally, the authority section of the URI. Optionally, the authority section MAY
authority section MAY also include the port preceded by a colon ":". also include the port preceded by a colon ":". If the port is not
If the port is not included, port 22 is assumed. Following the port included, the default port is assumed. Following the port additional
additional parameters may be specified. These parameters are parameters may be specified. These parameters are defined in the
defined in the connection parameters section. connection parameters section.
ssh_URI = "ssh://" [ userinfo "@" ] host [ ":" port ] ssh_URI = "ssh://" [ userinfo "@" ] host [ ":" port ]
[;conn-parameter=value] [;conn-parameter=value]
SCP and SFTP URI 1.2 SCP and SFTP URI
For SCP and SFTP, the scheme portion (scp: or sftp:) is followed by For SCP and SFTP, the scheme portion (scp: or sftp:) is followed by a
a double slash "//". double slash "//".
SCP/SFTP/SSH URI Format October 2003
Both SCP and SFTP URLs are terminated by a single slash "/" followed Both SCP and SFTP URLs are terminated by a single slash "/" followed
by the path information to the requested resource. by the path information to the requested resource.
The first component of the scheme specific portion MAY include The first component of the scheme specific portion MAY include
credentials (userinfo) consisting of a username and optionally also credentials (userinfo) consisting of a username and optionally also
including a password. Including the password in the URL is NOT including a password. Including the password in the URL is NOT
RECOMMENDED. The username and password components are separated by RECOMMENDED. The username and password components are separated by a
a single colon ":". single colon ":".
Following the userinfo, if present, the at-sign "@" shall precede Following the userinfo, if present, the at-sign "@" shall precede the
the authority section of the URL. Optionally, the authority section authority section of the URL. Optionally, the authority section MAY
MAY also include the port preceded by a colon ":". If the port is also include the port preceded by a colon ":". If the port is not
not included, port 22 is assumed. Following the port additional included, the default port is assumed. Following the port additional
parameters may be specified. These parameters are defined in the parameters may be specified. These parameters are defined in the
connection parameters section. connection parameters section.
scp_URI = "scp://" [ userinfo "@" ] host [ ":" port ] scp_URI = "scp://" [ userinfo "@" ] host [ ":" port ]
[ ; parameter = value ] [ abs_path ] [ ; parameter = value ] [ abs_path ]
Following the port additional parameters may be specified. These Following the port additional parameters may be specified. These
parameters are defined in the connection parameters section. parameters are defined in the connection parameters section.
Following the path additional sftp specific parameters may be Following the path additional sftp specific parameters may be
specified. specified.
sftp_URI = "sftp://" [ userinfo "@" ] host [ ":" port ] sftp_URI = "sftp://" [ userinfo "@" ] host [ ":" port ]
[;conn-parameter=value] [ abs_path ] [;sftp-parameter=value] [;conn-parameter=value] [ abs_path ] [;sftp-parameter=value]
Parameters 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].
SSH connection parameters 2. Parameters
2.1 SSH connection parameters
The following parameters are associated with an SSH connection and The following parameters are associated with an SSH connection and
are applicable to SSH, SFTP and SCP. All parameters are optional are applicable to SSH, SFTP and SCP. All parameters are optional and
and MUST NOT overwrite configured defaults. Individual parameters MUST NOT overwrite configured defaults. Individual parameters are
are separated by a comma (","). separated by a comma (",").
fingerprint fingerprint
The fingerprint parameter contains the fingerprint of the host key The fingerprint parameter contains the fingerprint of the host key
for the host specified in the URL. The fingerprint is encoded as for the host specified in the URL. The fingerprint is encoded as
in [3]. This parameter MUST NOT overwrite a key that is already host-key-alg:fingerprint. Host-key-alg is host public key algorithm
configured for the host. They fingerprint MAY be used to validate defined [4] and the fingerprint format is defined in [2].
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.
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 SCP/SFTP/SSH URI Format October 2003
The user-auth parameter indicates a user authentication mechanism to This parameter MUST NOT overwrite a key that is already configured
use when making the connection. The value is the string specifying for the host. The fingerprint MAY be used to validate the
the SSH user authentication mechanism type. This parameter MUST NOT authenticity of the host key if the URL was obtained from an
add a mechanism to a configured list of default configured authenticated source with its integrity protected. If this parameter
acceptable user authentication mechanism types. If this parameter is not included then the validity of the host key is validated using
is not specified then the default configured user authentication another method. See Security Considerations section for additional
mechanism type list is used. There may be more than one user-auth considerations. There MUST be only one fingerprint parameter per
parameter. host-key-alg for a given URL.
SFTP Parameters 2.2 SFTP Parameters
The SFTP parameters determine how to handle the file transfer The SFTP parameters determine how to handle the file transfer
character translation. character translation.
newline newline
The newline parameter determines how the server translates new line The newline parameter determines how the server translates new line
indicators. The possible choices are usually "\r" or "\n" or "\r\n". indicators. The possible choices are usually "\r" or "\n" or "\r\n".
The default is "\r\n". The default is "\r\n".
typecode typecode
The typecode identifies the type of file which determines how it The typecode identifies the type of file which determines how it will
will be treated. Possible values are "i" for binary files, "a" for be treated. Possible values are "i" for binary files, "a" for text
text files, and "d" for directory listings. files, and "d" for directory listings.
Examples 3. Examples
The following section shows basic examples of URLs for each The following section shows basic examples of URLs for each protocol.
protocol. This section should not be considered to include all This section should not be considered to include all possible
possible combinations of URLs for each protocol. combinations of URLs for each protocol.
ssh://user@host ssh://user@host
ssh://user@host:2222 ssh://user@host:2222
ssh://joeuser@example.com;fingerprint=c1:b1:30:29:d7:b8:de:6c ssh://joeuser@example.com;fingerprint=ssh-dss:c1:b1:30:29:d7:b8
:97:77:10:d7:46:41:63:87,cipher=aes-cbc :de:6c:97:77:10:d7:46:41:63:87
scp://user:password@host/file.txt scp://user:password@host/file.txt
sftp://user@host/dir/path/file.txt sftp://user@host/dir/path/file.txt
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 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
SCP/SFTP/SSH URI Format October 2003
In general, URIs themselves have no security considerations. In general, URIs themselves have no security considerations.
However, since the password for each scheme can optionally be However, since the password for each scheme can optionally be
included within the URL it should be noted that doing so poses a 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 security risk. Since URLs are usually sent in the clear with no
encryption or other security, any password or other credentials encryption or other security, any password or other credentials
(userinfo) included could be seen by a potential attacker. (userinfo) included could be seen by a potential attacker.
The fingerprint should only be used to validate the host key only if Care must also be taken in handling fingerprints associated with URLs
the URL can be determined to be authentic from a trusted entity. because URLs transmitted or stored without protection may be modified
For example, the URL may be received through secure email or HTTPS by an attacker. In general an implementation cannot determine the
from a trusted and verifiable source. It is possible that the SSH source of a URL so a fingerprint received in a URL should have no
implementation may not be able to determine if the URL is authentic more trust associated with it than a raw public key received in the
in which case it SHOULD prompt the user to either allow or disallow SSH protocol itself. If a locally configured key exists for the
the connection based on the information provided. The SSH server already it MUST NOT be automatically overwritten with
implementation MUST NOT overwrite a currently configured public key information from the URL. If the host is unknown then the
based on the URL alone. implementation should treat the fingerprint received with the same
caution that it does with any unknown public key. The client MAY
The other connection parameters MUST NOT add any mechanism to the offer the fingerprint and URL for external validation before allowing
list of configured acceptable mechanisms defined in the SSH client. 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 Normative References
[1] Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource [1] Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[2] Masinter, L., et. al., "Guidelines for new URL Schemes", RFC [2] Markus Friedl, "SSH Fingerprint Format",
2718, November 1999. http://www.ietf.org/internet-drafts/draft-ietf-secsh-fingerprint-
01.txt, work in progress
[3] Markus Friedl, "SSH Fingerprint Format", [3] Ylonen, T., "SSH Protocol Architecture",
http://www.ietf.org/internet-drafts/ http://www.ietf.org/internet-drafts/draft-ietf-secsh-architecture-
draft-ietf-secsh-fingerprint-01.txt, 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 work in progress
SCP/SFTP/SSH URI Format October 2003
Non-Normative References 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 Mealling, M., Denenberg, R., "Report from the Joint W3C/IETF URI
Planning Interest Group: Uniform Resource Identifiers (URIs), URLs, Planning Interest Group: Uniform Resource Identifiers (URIs), URLs,
and Uniform Resource Names (URNs): Clarifications and and Uniform Resource Names (URNs): Clarifications and
Recommendations", RFC 3305, August 2002. Recommendations", RFC 3305, August 2002.
Author Information Author Information
Steve Suehring Steve Suehring
Sentry Insurance Sentry Insurance
1800 North Point Dr, G2/61-17 1800 North Point Dr, G2/61-17
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proprietary rights by implementors or users of this specification can proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
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this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
Full Copyright Statement Full Copyright Statement
SCP/SFTP/SSH URI Format October 2003
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
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