Network Working Group S. Lehtinen

Network Working Group S. Lehtinen
Request for Comments: 4250 SSH Communications Security Corp
Category: Standards Track C. Lonvick, Ed.
Cisco Systems, Inc.
January 2006

The Secure Shell (SSH) Protocol Assigned Numbers

Status of This Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2006).

Abstract

This document defines the instructions to the IANA and the initial
state of the IANA assigned numbers for the Secure Shell (SSH)
protocol. It is intended only for the initialization of the IANA
registries referenced in the set of SSH documents.

Table of Contents

1. Introduction ....................................................2
2. Contributors ....................................................3
3. Conventions Used in This Document ...............................3
3.1. RFC 2119 Keywords ..........................................3
3.2. RFC 2434 Keywords ..........................................3
3.3. Protocol Fields and Values .................................4
4. IANA Considerations .............................................5
4.1. Message Numbers ............................................5
4.1.1. Conventions .........................................5
4.1.2. Initial Assignments .................................6
4.1.3. Future Assignments ..................................6
4.2. Disconnection Messages Reason Codes and Descriptions .......7
4.2.1. Conventions .........................................7
4.2.2. Initial Assignments .................................7
4.2.3. Future Assignments ..................................8
4.3. Channel Connection Failure Reason Codes and Descriptions ...8
4.3.1. Conventions .........................................8
4.3.2. Initial Assignments .................................8

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4.3.3. Future Assignments ..................................8
4.3.4. Notes about the PRIVATE USE Range ...................9
4.4. Extended Channel Data Transfer data_type_code and Data .....9
4.4.1. Conventions .........................................9
4.4.2. Initial Assignments ................................10
4.4.3. Future Assignments .................................10
4.5. Pseudo-Terminal Encoded Terminal Modes ....................10
4.5.1. Conventions ........................................10
4.5.2. Initial Assignments ................................10
4.5.3. Future Assignments .................................12
4.6. Names .....................................................12
4.6.1. Conventions for Names ..............................13
4.6.2. Future Assignments of Names ........................13
4.7. Service Names .............................................13
4.8. Authentication Method Names ...............................14
4.9. Connection Protocol Assigned Names ........................14
4.9.1. Connection Protocol Channel Types ..................14
4.9.2. Connection Protocol Global Request Names ...........14
4.9.3. Connection Protocol Channel Request Names ..........15
4.9.4. Initial Assignment of Signal Names .................15
4.9.5. Connection Protocol Subsystem Names ................15
4.10. Key Exchange Method Names ................................16
4.11. Assigned Algorithm Names .................................16
4.11.1. Encryption Algorithm Names ........................16
4.11.2. MAC Algorithm Names ...............................17
4.11.3. Public Key Algorithm Names ........................17
4.11.4. Compression Algorithm Names .......................17
5. Security Considerations ........................................17
6. References .....................................................18
6.1. Normative References ......................................18
6.2. Informative References ....................................18
Authors' Addresses ................................................19
Trademark Notice ..................................................19

1. Introduction

This document does not define any new protocols. It is intended only
to create the initial state of the IANA databases for the SSH
protocol and also contains instructions for future assignments.
Except for one HISTORIC algorithm generally regarded as obsolete,
this document does not define any new protocols or number ranges not
already defined in: [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH],
[SSH-CONNECT].

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2. Contributors

The major original contributors of this set of documents have been:
Tatu Ylonen, Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH
Communications Security Corp), and Markku-Juhani O. Saarinen
(University of Jyvaskyla). Darren Moffat was the original editor of
this set of documents and also made very substantial contributions.

Many people contributed to the development of this document over the
years. People who should be acknowledged include Mats Andersson, Ben
Harris, Bill Sommerfeld, Brent McClure, Niels Moller, Damien Miller,
Derek Fawcus, Frank Cusack, Heikki Nousiainen, Jakob Schlyter, Jeff
Van Dyke, Jeffrey Altman, Jeffrey Hutzelman, Jon Bright, Joseph
Galbraith, Ken Hornstein, Markus Friedl, Martin Forssen, Nicolas
Williams, Niels Provos, Perry Metzger, Peter Gutmann, Simon
Josefsson, Simon Tatham, Wei Dai, Denis Bider, der Mouse, and
Tadayoshi Kohno. Listing their names here does not mean that they
endorse this document, but that they have contributed to it.

3. Conventions Used in This Document

3.1. RFC 2119 Keywords

All documents related to the SSH protocols shall use the keywords
"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" to describe
requirements. These keywords are to be interpreted as described in
[RFC2119].

3.2. RFC 2434 Keywords

The keywords "PRIVATE USE", "HIERARCHICAL ALLOCATION", "FIRST COME
FIRST SERVED", "EXPERT REVIEW", "SPECIFICATION REQUIRED", "IESG
APPROVAL", "IETF CONSENSUS", and "STANDARDS ACTION" that appear in
this document when used to describe namespace allocation are to be
interpreted as described in [RFC2434]. These designations are
repeated in this document for clarity.

PRIVATE USE - For private or local use only, with the type and
purpose defined by the local site. No attempt is made to prevent
multiple sites from using the same value in different (and
incompatible) ways. There is no need for IANA to review such
assignments and assignments are not generally useful for
interoperability.

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HIERARCHICAL ALLOCATION - Delegated managers can assign values
provided they have been given control over that part of the name
space. IANA controls the higher levels of the namespace according to
one of the other policies.

FIRST COME FIRST SERVED - Anyone can obtain an assigned number, so
long as they provide a point of contact and a brief description of
what the value would be used for. For numbers, the exact value is
generally assigned by the IANA; with names, specific names are
usually requested.

EXPERT REVIEW - approval by a Designated Expert is required.

SPECIFICATION REQUIRED - Values and their meaning must be documented
in an RFC or other permanent and readily available reference, in
sufficient detail so that interoperability between independent
implementations is possible.

IESG APPROVAL - New assignments must be approved by the IESG, but
there is no requirement that the request be documented in an RFC
(though the IESG has discretion to request documents or other
supporting materials on a case-by-case basis).

IETF CONSENSUS - New values are assigned through the IETF consensus
process. Specifically, new assignments are made via RFCs approved by
the IESG. Typically, the IESG will seek input on prospective
assignments from appropriate persons (e.g., a relevant Working Group
if one exists).

STANDARDS ACTION - Values are assigned only for Standards Track RFCs
approved by the IESG.

3.3. Protocol Fields and Values

Protocol fields and possible values to fill them are defined in this
set of documents. Protocol fields will be defined in the message
definitions. As an example, SSH_MSG_CHANNEL_DATA is defined as
follows.

byte SSH_MSG_CHANNEL_DATA
uint32 recipient channel
string data

Throughout these documents, when the fields are referenced, they will
appear within single quotes. When values to fill those fields are
referenced, they will appear within double quotes. Using the above
example, possible values for 'data' are "foo" and "bar".

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4. IANA Considerations

This entire document is the IANA considerations for the SSH protocol,
as defined in [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH], [SSH-CONNECT].
This section contains conventions used in naming the namespaces, the
initial state of the registry, and instructions for future
assignments.

4.1. Message Numbers

The Message Number is a byte value that describes the payload of a
packet.

4.1.1. Conventions

Protocol packets have message numbers in the range 1 to 255. These
numbers are allocated as follows:

Transport layer protocol:

1 to 19 Transport layer generic (e.g., disconnect, ignore,
debug, etc.)
20 to 29 Algorithm negotiation
30 to 49 Key exchange method specific (numbers can be reused
for different authentication methods)

User authentication protocol:

50 to 59 User authentication generic
60 to 79 User authentication method specific (numbers can be
reused for different authentication methods)

Connection protocol:

80 to 89 Connection protocol generic
90 to 127 Channel related messages

Reserved for client protocols:

128 to 191 Reserved

Local extensions:

192 to 255 Local extensions

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4.1.2. Initial Assignments

The following table identifies the initial assignments of the Message
ID values.

Message ID Value Reference
----------- ----- ---------
SSH_MSG_DISCONNECT 1 [SSH-TRANS]
SSH_MSG_IGNORE 2 [SSH-TRANS]
SSH_MSG_UNIMPLEMENTED 3 [SSH-TRANS]
SSH_MSG_DEBUG 4 [SSH-TRANS]
SSH_MSG_SERVICE_REQUEST 5 [SSH-TRANS]
SSH_MSG_SERVICE_ACCEPT 6 [SSH-TRANS]
SSH_MSG_KEXINIT 20 [SSH-TRANS]
SSH_MSG_NEWKEYS 21 [SSH-TRANS]
SSH_MSG_USERAUTH_REQUEST 50 [SSH-USERAUTH]
SSH_MSG_USERAUTH_FAILURE 51 [SSH-USERAUTH]
SSH_MSG_USERAUTH_SUCCESS 52 [SSH-USERAUTH]
SSH_MSG_USERAUTH_BANNER 53 [SSH-USERAUTH]
SSH_MSG_GLOBAL_REQUEST 80 [SSH-CONNECT]
SSH_MSG_REQUEST_SUCCESS 81 [SSH-CONNECT]
SSH_MSG_REQUEST_FAILURE 82 [SSH-CONNECT]
SSH_MSG_CHANNEL_OPEN 90 [SSH-CONNECT]
SSH_MSG_CHANNEL_OPEN_CONFIRMATION 91 [SSH-CONNECT]
SSH_MSG_CHANNEL_OPEN_FAILURE 92 [SSH-CONNECT]
SSH_MSG_CHANNEL_WINDOW_ADJUST 93 [SSH-CONNECT]
SSH_MSG_CHANNEL_DATA 94 [SSH-CONNECT]
SSH_MSG_CHANNEL_EXTENDED_DATA 95 [SSH-CONNECT]
SSH_MSG_CHANNEL_EOF 96 [SSH-CONNECT]
SSH_MSG_CHANNEL_CLOSE 97 [SSH-CONNECT]
SSH_MSG_CHANNEL_REQUEST 98 [SSH-CONNECT]
SSH_MSG_CHANNEL_SUCCESS 99 [SSH-CONNECT]
SSH_MSG_CHANNEL_FAILURE 100 [SSH-CONNECT]

4.1.3. Future Assignments

Requests for assignments of new message numbers in the range of 1 to
29, 50 to 59, and 80 to 127 MUST be done through the STANDARDS ACTION
method, as described in [RFC2434].

The meanings of message numbers in the range of 30 to 49 are specific
to the key exchange method in use, and their meaning will be
specified by the definition of that method.

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The meanings of message numbers in the range of 60 to 79 are specific
to the user authentication method in use, and their meaning will be
specified by the definition of that method.

Requests for assignments of new message numbers in the range of 128
to 191 MUST be done through the IETF CONSENSUS method, as described
in [RFC2434].

The IANA will not control the message numbers in the range of 192
through 255. This range will be left for PRIVATE USE.

4.2. Disconnection Messages Reason Codes and Descriptions

The Disconnection Message 'reason code' is a uint32 value. The
associated Disconnection Message 'description' is a human-readable
message that describes the disconnect reason.

4.2.1. Conventions

Protocol packets containing the SSH_MSG_DISCONNECT message MUST have
Disconnection Message 'reason code' values in the range of 0x00000001
to 0xFFFFFFFF. These are described in [SSH-TRANS].

4.2.2. Initial Assignments

The following table identifies the initial assignments of the
SSH_MSG_DISCONNECT 'description' and 'reason code' values.

Symbolic Name reason code
------------- -----------
SSH_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT 1
SSH_DISCONNECT_PROTOCOL_ERROR 2
SSH_DISCONNECT_KEY_EXCHANGE_FAILED 3
SSH_DISCONNECT_RESERVED 4
SSH_DISCONNECT_MAC_ERROR 5
SSH_DISCONNECT_COMPRESSION_ERROR 6
SSH_DISCONNECT_SERVICE_NOT_AVAILABLE 7
SSH_DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED 8
SSH_DISCONNECT_HOST_KEY_NOT_VERIFIABLE 9
SSH_DISCONNECT_CONNECTION_LOST 10
SSH_DISCONNECT_BY_APPLICATION 11
SSH_DISCONNECT_TOO_MANY_CONNECTIONS 12
SSH_DISCONNECT_AUTH_CANCELLED_BY_USER 13
SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE 14
SSH_DISCONNECT_ILLEGAL_USER_NAME 15

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4.2.3. Future Assignments

Disconnection Message 'reason code' values MUST be assigned
sequentially. Requests for assignments of new Disconnection Message
'reason code' values, and their associated Disconnection Message
'description' text, in the range of 0x00000010 through 0xFDFFFFFF,
MUST be done through the IETF CONSENSUS method, as described in
[RFC2434]. The IANA will not assign Disconnection Message 'reason
code' values in the range of 0xFE000000 through 0xFFFFFFFF.
Disconnection Message 'reason code' values in that range are left for
PRIVATE USE, as described in [RFC2434].

4.3. Channel Connection Failure Reason Codes and Descriptions

The Channel Connection Failure 'reason code' is a uint32 value. The
associated Channel Connection Failure 'description' text is a human-
readable message that describes the channel connection failure
reason. This is described in [SSH-CONNECT].

4.3.1. Conventions

Protocol packets containing the SSH_MSG_CHANNEL_OPEN_FAILURE message
MUST have Channel Connection Failure 'reason code' values in the
range of 0x00000001 to 0xFFFFFFFF.

4.3.2. Initial Assignments

The initial assignments for the 'reason code' values and
'description' values are given in the table below. Note that the
values for the 'reason code' are given in decimal format for
readability, but they are actually uint32 values.

Symbolic Name reason code
------------- -----------
SSH_OPEN_ADMINISTRATIVELY_PROHIBITED 1
SSH_OPEN_CONNECT_FAILED 2
SSH_OPEN_UNKNOWN_CHANNEL_TYPE 3
SSH_OPEN_RESOURCE_SHORTAGE 4

4.3.3. Future Assignments

Channel Connection Failure 'reason code' values MUST be assigned
sequentially. Requests for assignments of new Channel Connection
Failure 'reason code' values, and their associated Channel Connection
Failure 'description string', in the range of 0x00000005 to
0xFDFFFFFF MUST be done through the IETF CONSENSUS method, as
described in [RFC2434]. The IANA will not assign Channel Connection

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Failure 'reason code' values in the range of 0xFE000000 to
0xFFFFFFFF. Channel Connection Failure 'reason code' values in that
range are left for PRIVATE USE, as described in [RFC2434].

4.3.4. Notes about the PRIVATE USE Range

While it is understood that the IANA will have no control over the
range of 0xFE000000 to 0xFFFFFFFF, this range will be split in two
parts and administered by the following conventions.

o The range of 0xFE000000 to 0xFEFFFFFF is to be used in conjunction
with locally assigned channels. For example, if a channel is
proposed with a 'channel type' of "[email protected]"
but fails, then the server will respond with either a 'reason
code' assigned by the IANA (as listed above and in the range of
0x00000001 to 0xFDFFFFFF), or with a locally assigned value in the
range of 0xFE000000 to 0xFEFFFFFF. Naturally, if the server does
not understand the proposed 'channel type', even if it is a
locally defined 'channel type', then the 'reason code' MUST be
0x00000003, as described above. If the server does understand the
'channel type', but the channel still fails to open, then the
server SHOULD respond with a locally assigned 'reason code' value
that is consistent with the proposed local 'channel type'. It is
assumed that practitioners will first attempt to use the IANA-
assigned 'reason code' values and then document their locally
assigned 'reason code' values.

o There are no restrictions or suggestions for the range starting
with 0xFF. No interoperability is expected for anything used in
this range. Essentially, it is for experimentation.

4.4. Extended Channel Data Transfer data_type_code and Data

The Extended Channel Data Transfer 'data_type_code' is a uint32
value. The associated Extended Channel Data Transfer 'data' is a
human-readable message that describes the type of data allowed to be
transferred in the channel.

4.4.1. Conventions

Protocol packets containing the SSH_MSG_CHANNEL_EXTENDED_DATA message
MUST have Extended Channel Data Transfer 'data_type_code' values in
the range of 0x00000001 to 0xFFFFFFFF. This is described in
[SSH-CONNECT].

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4.4.2. Initial Assignments

The initial assignments for the 'data_type_code' values and 'data'
values are given in the table below. Note that the value for the
'data_type_code' is given in decimal format for readability, but the
values are actually uint32 values.

Symbolic name data_type_code
------------- --------------
SSH_EXTENDED_DATA_STDERR 1

4.4.3. Future Assignments

Extended Channel Data Transfer 'data_type_code' values MUST be
assigned sequentially. Requests for assignments of new Extended
Channel Data Transfer 'data_type_code' values, and their associated
Extended Channel Data Transfer 'data' strings, in the range of
0x00000002 to 0xFDFFFFFF, MUST be done through the IETF CONSENSUS
method, as described in [RFC2434]. The IANA will not assign Extended
Channel Data Transfer 'data_type_code' values in the range of
0xFE000000 to 0xFFFFFFFF. Extended Channel Data Transfer
'data_type_code' values in that range are left for PRIVATE USE, as
described in [RFC2434].

4.5. Pseudo-Terminal Encoded Terminal Modes

SSH_MSG_CHANNEL_REQUEST messages with a "pty-req" string MUST contain
'encoded terminal modes'. The 'encoded terminal modes' value is a
byte stream of opcode-argument pairs.

4.5.1. Conventions

Protocol packets containing the SSH_MSG_CHANNEL_REQUEST message with
a "pty-req" string MUST contain an 'encoded terminal modes' value.
The opcode values consist of a single byte and are in the range of 1
to 255. Opcodes 1 to 159 have a uint32 argument. Opcodes 160 to 255
are not yet defined.

4.5.2. Initial Assignments

The following table identifies the initial assignments of the opcode
values that are used in the 'encoded terminal modes' value.

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opcode mnemonic description
------ -------- -----------
0 TTY_OP_END Indicates end of options.
1 VINTR Interrupt character; 255 if none. Similarly
for the other characters. Not all of these
characters are supported on all systems.
2 VQUIT The quit character (sends SIGQUIT signal on
POSIX systems).
3 VERASE Erase the character to left of the cursor.
4 VKILL Kill the current input line.
5 VEOF End-of-file character (sends EOF from the
terminal).
6 VEOL End-of-line character in addition to
carriage return and/or linefeed.
7 VEOL2 Additional end-of-line character.
8 VSTART Continues paused output (normally
control-Q).
9 VSTOP Pauses output (normally control-S).
10 VSUSP Suspends the current program.
11 VDSUSP Another suspend character.
12 VREPRINT Reprints the current input line.
13 VWERASE Erases a word left of cursor.
14 VLNEXT Enter the next character typed literally,
even if it is a special character
15 VFLUSH Character to flush output.
16 VSWTCH Switch to a different shell layer.
17 VSTATUS Prints system status line (load, command,
pid, etc).
18 VDISCARD Toggles the flushing of terminal output.
30 IGNPAR The ignore parity flag. The parameter
SHOULD be 0 if this flag is FALSE,
and 1 if it is TRUE.
31 PARMRK Mark parity and framing errors.
32 INPCK Enable checking of parity errors.
33 ISTRIP Strip 8th bit off characters.
34 INLCR Map NL into CR on input.
35 IGNCR Ignore CR on input.
36 ICRNL Map CR to NL on input.
37 IUCLC Translate uppercase characters to
lowercase.
38 IXON Enable output flow control.
39 IXANY Any char will restart after stop.
40 IXOFF Enable input flow control.
41 IMAXBEL Ring bell on input queue full.
50 ISIG Enable signals INTR, QUIT, [D]SUSP.
51 ICANON Canonicalize input lines.

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52 XCASE Enable input and output of uppercase
characters by preceding their lowercase
equivalents with "\".
53 ECHO Enable echoing.
54 ECHOE Visually erase chars.
55 ECHOK Kill character discards current line.
56 ECHONL Echo NL even if ECHO is off.
57 NOFLSH Don't flush after interrupt.
58 TOSTOP Stop background jobs from output.
59 IEXTEN Enable extensions.
60 ECHOCTL Echo control characters as ^(Char).
61 ECHOKE Visual erase for line kill.
62 PENDIN Retype pending input.
70 OPOST Enable output processing.
71 OLCUC Convert lowercase to uppercase.
72 ONLCR Map NL to CR-NL.
73 OCRNL Translate carriage return to newline
(output).
74 ONOCR Translate newline to carriage
return-newline (output).
75 ONLRET Newline performs a carriage return
(output).
90 CS7 7 bit mode.
91 CS8 8 bit mode.
92 PARENB Parity enable.
93 PARODD Odd parity, else even.

128 TTY_OP_ISPEED Specifies the input baud rate in
bits per second.
129 TTY_OP_OSPEED Specifies the output baud rate in
bits per second.

4.5.3. Future Assignments

Requests for assignments of new opcodes and their associated
arguments MUST be done through the IETF CONSENSUS method, as
described in [RFC2434].

4.6. Names

In the following sections, the values for the name spaces are
textual. The conventions and instructions to the IANA for future
assignments are given in this section. The initial assignments are
given in their respective sections.

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4.6.1. Conventions for Names

All names registered by the IANA in the following sections MUST be
printable US-ASCII strings, and MUST NOT contain the characters at-
sign ("@"), comma (","), whitespace, control characters (ASCII codes
32 or less), or the ASCII code 127 (DEL). Names are case-sensitive,
and MUST NOT be longer than 64 characters.

A provision is made here for locally extensible names. The IANA will
not register, and will not control, names with the at-sign in them.

Names with the at-sign in them will have the format of
"name@domainname" (without the double quotes) where the part
preceding the at-sign is the name. The format of the part preceding
the at-sign is not specified; however, these names MUST be printable
US-ASCII strings, and MUST NOT contain the comma character (","),
whitespace, control characters (ASCII codes 32 or less), or the ASCII
code 127 (DEL). They MUST have only a single at-sign in them. The
part following the at-sign MUST be a valid, fully qualified internet
domain name [RFC1034] controlled by the person or organization
defining the name. Names are case-sensitive, and MUST NOT be longer
than 64 characters. It is up to each domain how it manages its local
namespace. It has been noted that these names resemble STD 11
[RFC0822] email addresses. This is purely coincidental and has
nothing to do with STD 11 [RFC0822]. An example of a locally defined
name is "[email protected]" (without the double quotes).

4.6.2. Future Assignments of Names

Requests for assignments of new names MUST be done through the IETF
CONSENSUS method, as described in [RFC2434].

4.7. Service Names

The 'service name' is used to describe a protocol layer. The
following table lists the initial assignments of the 'service name'
values.

Service Name Reference
------------- ---------
ssh-userauth [SSH-USERAUTH]
ssh-connection [SSH-CONNECT]

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4.8. Authentication Method Names

The Authentication Method Name is used to describe an authentication
method for the "ssh-userauth" service [SSH-USERAUTH]. The following
table identifies the initial assignments of the Authentication Method
Names.

Method Name Reference
------------ ---------
publickey [SSH-USERAUTH, Section 7]
password [SSH-USERAUTH, Section 8]
hostbased [SSH-USERAUTH, Section 9]
none [SSH-USERAUTH, Section 5.2]

4.9. Connection Protocol Assigned Names

The following table lists the initial assignments to the Connection
Protocol Type and Request names.

4.9.1. Connection Protocol Channel Types

The following table lists the initial assignments of the Connection
Protocol Channel Types.

Channel type Reference
------------ ---------
session [SSH-CONNECT, Section 6.1]
x11 [SSH-CONNECT, Section 6.3.2]
forwarded-tcpip [SSH-CONNECT, Section 7.2]
direct-tcpip [SSH-CONNECT, Section 7.2]

4.9.2. Connection Protocol Global Request Names

The following table lists the initial assignments of the Connection
Protocol Global Request Names.

Request type Reference
------------ ---------
tcpip-forward [SSH-CONNECT, Section 7.1]
cancel-tcpip-forward [SSH-CONNECT, Section 7.1]

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4.9.3. Connection Protocol Channel Request Names

The following table lists the initial assignments of the Connection
Protocol Channel Request Names.

Request type Reference
------------ ---------
pty-req [SSH-CONNECT, Section 6.2]
x11-req [SSH-CONNECT, Section 6.3.1]
env [SSH-CONNECT, Section 6.4]
shell [SSH-CONNECT, Section 6.5]
exec [SSH-CONNECT, Section 6.5]
subsystem [SSH-CONNECT, Section 6.5]
window-change [SSH-CONNECT, Section 6.7]
xon-xoff [SSH-CONNECT, Section 6.8]
signal [SSH-CONNECT, Section 6.9]
exit-status [SSH-CONNECT, Section 6.10]
exit-signal [SSH-CONNECT, Section 6.10]

4.9.4. Initial Assignment of Signal Names

The following table lists the initial assignments of the Signal
Names.

Signal Reference
------ ---------
ABRT [SSH-CONNECT]
ALRM [SSH-CONNECT]
FPE [SSH-CONNECT]
HUP [SSH-CONNECT]
ILL [SSH-CONNECT]
INT [SSH-CONNECT]
KILL [SSH-CONNECT]
PIPE [SSH-CONNECT]
QUIT [SSH-CONNECT]
SEGV [SSH-CONNECT]
TERM [SSH-CONNECT]
USR1 [SSH-CONNECT]
USR2 [SSH-CONNECT]

4.9.5. Connection Protocol Subsystem Names

There are no initial assignments of the Connection Protocol Subsystem
Names.

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4.10. Key Exchange Method Names

The name "diffie-hellman-group1-sha1" is used for a key exchange
method using an Oakley group, as defined in [RFC2409]. SSH maintains
its own group identifier space, which is logically distinct from
Oakley [RFC2412] and IKE; however, for one additional group, the
Working Group adopted the number assigned by [RFC3526], using
"diffie-hellman-group14-sha1" for the name of the second defined
group. Implementations should treat these names as opaque
identifiers and should not assume any relationship between the groups
used by SSH and the groups defined for IKE.

The following table identifies the initial assignments of the key
exchange methods.

Method name Reference
------------ ---------
diffie-hellman-group1-sha1 [SSH-TRANS, Section 8.1]
diffie-hellman-group14-sha1 [SSH-TRANS, Section 8.2]

4.11. Assigned Algorithm Names

4.11.1. Encryption Algorithm Names

The following table identifies the initial assignment of the
Encryption Algorithm Names.

Encryption Algorithm Name Reference
------------------------- ---------
3des-cbc [SSH-TRANS, Section 6.3]
blowfish-cbc [SSH-TRANS, Section 6.3]
twofish256-cbc [SSH-TRANS, Section 6.3]
twofish-cbc [SSH-TRANS, Section 6.3]
twofish192-cbc [SSH-TRANS, Section 6.3]
twofish128-cbc [SSH-TRANS, Section 6.3]
aes256-cbc [SSH-TRANS, Section 6.3]
aes192-cbc [SSH-TRANS, Section 6.3]
aes128-cbc [SSH-TRANS, Section 6.3]
serpent256-cbc [SSH-TRANS, Section 6.3]
serpent192-cbc [SSH-TRANS, Section 6.3]
serpent128-cbc [SSH-TRANS, Section 6.3]
arcfour [SSH-TRANS, Section 6.3]
idea-cbc [SSH-TRANS, Section 6.3]
cast128-cbc [SSH-TRANS, Section 6.3]
none [SSH-TRANS, Section 6.3]
des-cbc [FIPS-46-3] HISTORIC; See
page 4 of [FIPS-46-3]

Lehtinen & Lonvick Standards Track [Page 16]

RFC 4250 SSH Protocol Assigned Numbers January 2006

4.11.2. MAC Algorithm Names

The following table identifies the initial assignments of the MAC
Algorithm Names.

MAC Algorithm Name Reference
------------------ ---------
hmac-sha1 [SSH-TRANS, Section 6.4]
hmac-sha1-96 [SSH-TRANS, Section 6.4]
hmac-md5 [SSH-TRANS, Section 6.4]
hmac-md5-96 [SSH-TRANS, Section 6.4]
none [SSH-TRANS, Section 6.4]

4.11.3. Public Key Algorithm Names

The following table identifies the initial assignments of the Public
Key Algorithm names.

Public Key Algorithm Name Reference
------------------------- ---------
ssh-dss [SSH-TRANS, Section 6.6]
ssh-rsa [SSH-TRANS, Section 6.6]
pgp-sign-rsa [SSH-TRANS, Section 6.6]
pgp-sign-dss [SSH-TRANS, Section 6.6]

4.11.4. Compression Algorithm Names

The following table identifies the initial assignments of the
Compression Algorithm names.

Compression Algorithm Name Reference
-------------------------- ---------
none [SSH-TRANS, Section 6.2]
zlib [SSH-TRANS, Section 6.2]

5. Security Considerations

This protocol provides a secure encrypted channel over an insecure
network.

Full security considerations for this protocol are provided in
[SSH-ARCH].

Lehtinen & Lonvick Standards Track [Page 17]

RFC 4250 SSH Protocol Assigned Numbers January 2006

6. References

6.1. Normative References

[SSH-ARCH] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Protocol Architecture", RFC 4251, January 2006.

[SSH-TRANS] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Transport Layer Protocol", RFC 4253, January
2006.

[SSH-USERAUTH] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Authentication Protocol", RFC 4252, January
2006.

[SSH-CONNECT] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Connection Protocol", RFC 4254, January 2006.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.

[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26, RFC
2434, October 1998.

[RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential
(MODP) Diffie-Hellman groups for Internet Key Exchange
(IKE)", RFC 3526, May 2003.

6.2. Informative References

[RFC0822] Crocker, D., "Standard for the format of ARPA Internet
text messages", STD 11, RFC 822, August 1982.

[RFC1034] Mockapetris, P., "Domain names - concepts and
facilities", STD 13, RFC 1034, November 1987.

[RFC2412] Orman, H., "The OAKLEY Key Determination Protocol",
RFC 2412, November 1998.

[FIPS-46-3] US National Institute of Standards and Technology,
"Data Encryption Standard (DES)", Federal Information
Processing Standards Publication 46-3, October 1999.

Lehtinen & Lonvick Standards Track [Page 18]

RFC 4250 SSH Protocol Assigned Numbers January 2006

Authors' Addresses

Sami Lehtinen
SSH Communications Security Corp
Valimotie 17
00380 Helsinki
Finland

EMail: [email protected]

Chris Lonvick (editor)
Cisco Systems, Inc.
12515 Research Blvd.
Austin 78759
USA

EMail: [email protected]

Trademark Notice

"ssh" is a registered trademark in the United States and/or other
countries.

Lehtinen & Lonvick Standards Track [Page 19]

RFC 4250 SSH Protocol Assigned Numbers January 2006

Full Copyright Statement

Copyright (C) The Internet Society (2006).

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Lehtinen & Lonvick Standards Track [Page 20]