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Network Working Group T. Ylonen
Internet-Draft T. Kivinen
Expires: January 12, 2004 SSH Communications Security Corp
M. Saarinen
University of Jyvaskyla
T. Rinne
S. Lehtinen
SSH Communications Security Corp
July 14, 2003
SSH Connection Protocol
draft-ietf-secsh-connect-17.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 12, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
SSH is a protocol for secure remote login and other secure network
services over an insecure network.
This document describes the SSH Connection Protocol. It provides
interactive login sessions, remote execution of commands,
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forwarded TCP/IP connections, and forwarded X11 connections. All
of these channels are multiplexed into a single encrypted tunnel.
The SSH Connection Protocol has been designed to run on top of the
SSH transport layer and user authentication protocols.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Global Requests . . . . . . . . . . . . . . . . . . . . . . 3
3. Channel Mechanism . . . . . . . . . . . . . . . . . . . . . 3
3.1 Opening a Channel . . . . . . . . . . . . . . . . . . . . . 4
3.2 Data Transfer . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 Closing a Channel . . . . . . . . . . . . . . . . . . . . . 6
3.4 Channel-Specific Requests . . . . . . . . . . . . . . . . . 7
4. Interactive Sessions . . . . . . . . . . . . . . . . . . . . 8
4.1 Opening a Session . . . . . . . . . . . . . . . . . . . . . 8
4.2 Requesting a Pseudo-Terminal . . . . . . . . . . . . . . . . 8
4.3 X11 Forwarding . . . . . . . . . . . . . . . . . . . . . . . 9
4.3.1 Requesting X11 Forwarding . . . . . . . . . . . . . . . . . 9
4.3.2 X11 Channels . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Environment Variable Passing . . . . . . . . . . . . . . . . 10
4.5 Starting a Shell or a Command . . . . . . . . . . . . . . . 10
4.6 Session Data Transfer . . . . . . . . . . . . . . . . . . . 11
4.7 Window Dimension Change Message . . . . . . . . . . . . . . 11
4.8 Local Flow Control . . . . . . . . . . . . . . . . . . . . . 12
4.9 Signals . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.10 Returning Exit Status . . . . . . . . . . . . . . . . . . . 12
5. TCP/IP Port Forwarding . . . . . . . . . . . . . . . . . . . 14
5.1 Requesting Port Forwarding . . . . . . . . . . . . . . . . . 14
5.2 TCP/IP Forwarding Channels . . . . . . . . . . . . . . . . . 15
6. Encoding of Terminal Modes . . . . . . . . . . . . . . . . . 16
7. Summary of Message Numbers . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . 18
9. Intellectual Property . . . . . . . . . . . . . . . . . . . 18
10. Additional Information . . . . . . . . . . . . . . . . . . . 19
References . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20
Full Copyright Statement . . . . . . . . . . . . . . . . . . 22
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1. Introduction
The SSH Connection Protocol has been designed to run on top of the
SSH transport layer and user authentication protocols. It
provides interactive login sessions, remote execution of commands,
forwarded TCP/IP connections, and forwarded X11 connections. The
service name for this protocol (after user authentication) is
"ssh-connection".
This document should be read only after reading the SSH
architecture document [SSH-ARCH]. This document freely uses
terminology and notation from the architecture document without
reference or further explanation.
2. Global Requests
There are several kinds of requests that affect the state of the
remote end "globally", independent of any channels. An example is
a request to start TCP/IP forwarding for a specific port. All
such requests use the following format.
byte SSH_MSG_GLOBAL_REQUEST
string request name (restricted to US-ASCII)
boolean want reply
... request-specific data follows
Request names follow the DNS extensibility naming convention
outlined in [SSH-ARCH].
The recipient will respond to this message with
SSH_MSG_REQUEST_SUCCESS or SSH_MSG_REQUEST_FAILURE if `want reply'
is TRUE.
byte SSH_MSG_REQUEST_SUCCESS
..... response specific data
Usually the response specific data is non-existent.
If the recipient does not recognize or support the request, it
simply responds with SSH_MSG_REQUEST_FAILURE.
byte SSH_MSG_REQUEST_FAILURE
3. Channel Mechanism
All terminal sessions, forwarded connections, etc. are channels.
Either side may open a channel. Multiple channels are multiplexed
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into a single connection.
Channels are identified by numbers at each end. The number
referring to a channel may be different on each side. Requests to
open a channel contain the sender's channel number. Any other
channel-related messages contain the recipient's channel number
for the channel.
Channels are flow-controlled. No data may be sent to a channel
until a message is received to indicate that window space is
available.
3.1 Opening a Channel
When either side wishes to open a new channel, it allocates a
local number for the channel. It then sends the following message
to the other side, and includes the local channel number and
initial window size in the message.
byte SSH_MSG_CHANNEL_OPEN
string channel type (restricted to US-ASCII)
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
... channel type specific data follows
The channel type is a name as described in the SSH architecture
document, with similar extension mechanisms. `sender channel' is
a local identifier for the channel used by the sender of this
message. `initial window size' specifies how many bytes of
channel data can be sent to the sender of this message without
adjusting the window. `Maximum packet size' specifies the maximum
size of an individual data packet that can be sent to the sender
(for example, one might want to use smaller packets for
interactive connections to get better interactive response on slow
links).
The remote side then decides whether it can open the channel, and
responds with either
byte SSH_MSG_CHANNEL_OPEN_CONFIRMATION
uint32 recipient channel
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
... channel type specific data follows
where `recipient channel' is the channel number given in the
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original open request, and `sender channel' is the channel number
allocated by the other side, or
byte SSH_MSG_CHANNEL_OPEN_FAILURE
uint32 recipient channel
uint32 reason code
string additional textual information (ISO-10646 UTF-8 [RFC2279])
string language tag (as defined in [RFC1766])
If the recipient of the SSH_MSG_CHANNEL_OPEN message does not
support the specified channel type, it simply responds with
SSH_MSG_CHANNEL_OPEN_FAILURE. The client MAY show the additional
information to the user. If this is done, the client software
should take the precautions discussed in [SSH-ARCH].
The following reason codes are defined:
#define SSH_OPEN_ADMINISTRATIVELY_PROHIBITED 1
#define SSH_OPEN_CONNECT_FAILED 2
#define SSH_OPEN_UNKNOWN_CHANNEL_TYPE 3
#define SSH_OPEN_RESOURCE_SHORTAGE 4
3.2 Data Transfer
The window size specifies how many bytes the other party can send
before it must wait for the window to be adjusted. Both parties
use the following message to adjust the window.
byte SSH_MSG_CHANNEL_WINDOW_ADJUST
uint32 recipient channel
uint32 bytes to add
After receiving this message, the recipient MAY send the given
number of bytes more than it was previously allowed to send; the
window size is incremented.
Data transfer is done with messages of the following type.
byte SSH_MSG_CHANNEL_DATA
uint32 recipient channel
string data
The maximum amount of data allowed is the current window size.
The window size is decremented by the amount of data sent. Both
parties MAY ignore all extra data sent after the allowed window is
empty.
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Additionally, some channels can transfer several types of data.
An example of this is stderr data from interactive sessions. Such
data can be passed with SSH_MSG_CHANNEL_EXTENDED_DATA messages,
where a separate integer specifies the type of the data. The
available types and their interpretation depend on the type of the
channel.
byte SSH_MSG_CHANNEL_EXTENDED_DATA
uint32 recipient_channel
uint32 data_type_code
string data
Data sent with these messages consumes the same window as ordinary
data.
Currently, only the following type is defined.
#define SSH_EXTENDED_DATA_STDERR 1
3.3 Closing a Channel
When a party will no longer send more data to a channel, it SHOULD
send SSH_MSG_CHANNEL_EOF.
byte SSH_MSG_CHANNEL_EOF
uint32 recipient_channel
No explicit response is sent to this message; however, the
application may send EOF to whatever is at the other end of the
channel. Note that the channel remains open after this message,
and more data may still be sent in the other direction. This
message does not consume window space and can be sent even if no
window space is available.
When either party wishes to terminate the channel, it sends
SSH_MSG_CHANNEL_CLOSE. Upon receiving this message, a party MUST
send back a SSH_MSG_CHANNEL_CLOSE unless it has already sent this
message for the channel. The channel is considered closed for a
party when it has both sent and received SSH_MSG_CHANNEL_CLOSE,
and the party may then reuse the channel number. A party MAY send
SSH_MSG_CHANNEL_CLOSE without having sent or received
SSH_MSG_CHANNEL_EOF.
byte SSH_MSG_CHANNEL_CLOSE
uint32 recipient_channel
This message does not consume window space and can be sent even if
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no window space is available.
It is recommended that any data sent before this message is
delivered to the actual destination, if possible.
3.4 Channel-Specific Requests
Many channel types have extensions that are specific to that
particular channel type. An example is requesting a pty (pseudo
terminal) for an interactive session.
All channel-specific requests use the following format.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string request type (restricted to US-ASCII)
boolean want reply
... type-specific data
If want reply is FALSE, no response will be sent to the request.
Otherwise, the recipient responds with either
SSH_MSG_CHANNEL_SUCCESS or SSH_MSG_CHANNEL_FAILURE, or request-
specific continuation messages. If the request is not recognized
or is not supported for the channel, SSH_MSG_CHANNEL_FAILURE is
returned.
This message does not consume window space and can be sent even if
no window space is available. Request types are local to each
channel type.
The client is allowed to send further messages without waiting for
the response to the request.
request type names follow the DNS extensibility naming convention
outlined in [SSH-ARCH]
byte SSH_MSG_CHANNEL_SUCCESS
uint32 recipient_channel
byte SSH_MSG_CHANNEL_FAILURE
uint32 recipient_channel
These messages do not consume window space and can be sent even if
no window space is available.
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4. Interactive Sessions
A session is a remote execution of a program. The program may be
a shell, an application, a system command, or some built-in
subsystem. It may or may not have a tty, and may or may not
involve X11 forwarding. Multiple sessions can be active
simultaneously.
4.1 Opening a Session
A session is started by sending the following message.
byte SSH_MSG_CHANNEL_OPEN
string "session"
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
Client implementations SHOULD reject any session channel open
requests to make it more difficult for a corrupt server to attack
the client.
4.2 Requesting a Pseudo-Terminal
A pseudo-terminal can be allocated for the session by sending the
following message.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient_channel
string "pty-req"
boolean want_reply
string TERM environment variable value (e.g., vt100)
uint32 terminal width, characters (e.g., 80)
uint32 terminal height, rows (e.g., 24)
uint32 terminal width, pixels (e.g., 640)
uint32 terminal height, pixels (e.g., 480)
string encoded terminal modes
The encoding of terminal modes is described in Section Encoding of
Terminal Modes (Section 6). Zero dimension parameters MUST be
ignored. The character/row dimensions override the pixel
dimensions (when nonzero). Pixel dimensions refer to the drawable
area of the window.
The dimension parameters are only informational.
The client SHOULD ignore pty requests.
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4.3 X11 Forwarding
4.3.1 Requesting X11 Forwarding
X11 forwarding may be requested for a session by sending
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "x11-req"
boolean want reply
boolean single connection
string x11 authentication protocol
string x11 authentication cookie
uint32 x11 screen number
It is recommended that the authentication cookie that is sent be a
fake, random cookie, and that the cookie is checked and replaced
by the real cookie when a connection request is received.
X11 connection forwarding should stop when the session channel is
closed; however, already opened forwardings should not be
automatically closed when the session channel is closed.
If `single connection' is TRUE, only a single connection should be
forwarded. No more connections will be forwarded after the first,
or after the session channel has been closed.
The `x11 authentication protocol' is the name of the X11
authentication method used, e.g. "MIT-MAGIC-COOKIE-1".
The x11 authentication cookie MUST be hexadecimal encoded.
X Protocol is documented in [SCHEIFLER].
4.3.2 X11 Channels
X11 channels are opened with a channel open request. The
resulting channels are independent of the session, and closing the
session channel does not close the forwarded X11 channels.
byte SSH_MSG_CHANNEL_OPEN
string "x11"
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
string originator address (e.g. "192.168.7.38")
uint32 originator port
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The recipient should respond with
SSH_MSG_CHANNEL_OPEN_CONFIRMATION or SSH_MSG_CHANNEL_OPEN_FAILURE.
Implementations MUST reject any X11 channel open requests if they
have not requested X11 forwarding.
4.4 Environment Variable Passing
Environment variables may be passed to the shell/command to be
started later. Uncontrolled setting of environment variables in a
privileged process can be a security hazard. It is recommended
that implementations either maintain a list of allowable variable
names or only set environment variables after the server process
has dropped sufficient privileges.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "env"
boolean want reply
string variable name
string variable value
4.5 Starting a Shell or a Command
Once the session has been set up, a program is started at the
remote end. The program can be a shell, an application program or
a subsystem with a host-independent name. Only one of these
requests can succeed per channel.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "shell"
boolean want reply
This message will request the user's default shell (typically
defined in /etc/passwd in UNIX systems) to be started at the other
end.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "exec"
boolean want reply
string command
This message will request the server to start the execution of the
given command. The command string may contain a path. Normal
precautions MUST be taken to prevent the execution of unauthorized
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commands.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "subsystem"
boolean want reply
string subsystem name
This last form executes a predefined subsystem. It is expected
that these will include a general file transfer mechanism, and
possibly other features. Implementations may also allow
configuring more such mechanisms. As the user's shell is usually
used to execute the subsystem, it is advisable for the subsystem
protocol to have a "magic cookie" at the beginning of the protocol
transaction to distinguish it from arbitrary output generated by
shell initialization scripts etc. This spurious output from the
shell may be filtered out either at the server or at the client.
The server SHOULD not halt the execution of the protocol stack
when starting a shell or a program. All input and output from
these SHOULD be redirected to the channel or to the encrypted
tunnel.
It is RECOMMENDED to request and check the reply for these
messages. The client SHOULD ignore these messages.
Subsystem names follow the DNS extensibility naming convention
outlined in [SSH-ARCH].
4.6 Session Data Transfer
Data transfer for a session is done using SSH_MSG_CHANNEL_DATA and
SSH_MSG_CHANNEL_EXTENDED_DATA packets and the window mechanism.
The extended data type SSH_EXTENDED_DATA_STDERR has been defined
for stderr data.
4.7 Window Dimension Change Message
When the window (terminal) size changes on the client side, it MAY
send a message to the other side to inform it of the new
dimensions.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient_channel
string "window-change"
boolean FALSE
uint32 terminal width, columns
uint32 terminal height, rows
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uint32 terminal width, pixels
uint32 terminal height, pixels
No response SHOULD be sent to this message.
4.8 Local Flow Control
On many systems, it is possible to determine if a pseudo-terminal
is using control-S/control-Q flow control. When flow control is
allowed, it is often desirable to do the flow control at the
client end to speed up responses to user requests. This is
facilitated by the following notification. Initially, the server
is responsible for flow control. (Here, again, client means the
side originating the session, and server means the other side.)
The message below is used by the server to inform the client when
it can or cannot perform flow control (control-S/control-Q
processing). If `client can do' is TRUE, the client is allowed to
do flow control using control-S and control-Q. The client MAY
ignore this message.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "xon-xoff"
boolean FALSE
boolean client can do
No response is sent to this message.
4.9 Signals
A signal can be delivered to the remote process/service using the
following message. Some systems may not implement signals, in
which case they SHOULD ignore this message.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "signal"
boolean FALSE
string signal name without the "SIG" prefix.
Signal names will be encoded as discussed in the "exit-signal"
SSH_MSG_CHANNEL_REQUEST.
4.10 Returning Exit Status
When the command running at the other end terminates, the
following message can be sent to return the exit status of the
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command. Returning the status is RECOMMENDED. No acknowledgment
is sent for this message. The channel needs to be closed with
SSH_MSG_CHANNEL_CLOSE after this message.
The client MAY ignore these messages.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient_channel
string "exit-status"
boolean FALSE
uint32 exit_status
The remote command may also terminate violently due to a signal.
Such a condition can be indicated by the following message. A
zero exit_status usually means that the command terminated
successfully.
byte SSH_MSG_CHANNEL_REQUEST
uint32 recipient channel
string "exit-signal"
boolean FALSE
string signal name without the "SIG" prefix.
boolean core dumped
string error message (ISO-10646 UTF-8)
string language tag (as defined in [RFC1766])
The signal name is one of the following (these are from [POSIX])
ABRT
ALRM
FPE
HUP
ILL
INT
KILL
PIPE
QUIT
SEGV
TERM
USR1
USR2
Additional signal names MAY be sent in the format "sig-name@xyz",
where `sig-name' and `xyz' may be anything a particular
implementor wants (except the `@' sign). However, it is suggested
that if a `configure' script is used, the non-standard signal
names it finds be encoded as "SIG@xyz.config.guess", where `SIG'
is the signal name without the "SIG" prefix, and `xyz' be the host
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type, as determined by `config.guess'.
The `error message' contains an additional explanation of the
error message. The message may consist of multiple lines. The
client software MAY display this message to the user. If this is
done, the client software should take the precautions discussed in
[SSH-ARCH].
5. TCP/IP Port Forwarding
5.1 Requesting Port Forwarding
A party need not explicitly request forwardings from its own end
to the other direction. However, if it wishes that connections to
a port on the other side be forwarded to the local side, it must
explicitly request this.
byte SSH_MSG_GLOBAL_REQUEST
string "tcpip-forward"
boolean want reply
string address to bind (e.g. "0.0.0.0")
uint32 port number to bind
`Address to bind' and `port number to bind' specify the IP address
and port to which the socket to be listened is bound. The address
should be "0.0.0.0" if connections are allowed from anywhere.
(Note that the client can still filter connections based on
information passed in the open request.)
Implementations should only allow forwarding privileged ports if
the user has been authenticated as a privileged user.
Client implementations SHOULD reject these messages; they are
normally only sent by the client.
If a client passes 0 as port number to bind and has want reply
TRUE then the server allocates the next available unprivileged
port number and replies with the following message, otherwise
there is no response specific data.
byte SSH_MSG_GLOBAL_REQUEST_SUCCESS
uint32 port that was bound on the server
A port forwarding can be cancelled with the following message.
Note that channel open requests may be received until a reply to
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this message is received.
byte SSH_MSG_GLOBAL_REQUEST
string "cancel-tcpip-forward"
boolean want reply
string address_to_bind (e.g. "127.0.0.1")
uint32 port number to bind
Client implementations SHOULD reject these messages; they are
normally only sent by the client.
5.2 TCP/IP Forwarding Channels
When a connection comes to a port for which remote forwarding has
been requested, a channel is opened to forward the port to the
other side.
byte SSH_MSG_CHANNEL_OPEN
string "forwarded-tcpip"
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
string address that was connected
uint32 port that was connected
string originator IP address
uint32 originator port
Implementations MUST reject these messages unless they have
previously requested a remote TCP/IP port forwarding with the
given port number.
When a connection comes to a locally forwarded TCP/IP port, the
following packet is sent to the other side. Note that these
messages MAY be sent also for ports for which no forwarding has
been explicitly requested. The receiving side must decide whether
to allow the forwarding.
byte SSH_MSG_CHANNEL_OPEN
string "direct-tcpip"
uint32 sender channel
uint32 initial window size
uint32 maximum packet size
string host to connect
uint32 port to connect
string originator IP address
uint32 originator port
`Host to connect' and `port to connect' specify the TCP/IP host
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and port where the recipient should connect the channel. `Host to
connect' may be either a domain name or a numeric IP address.
`Originator IP address' is the numeric IP address of the machine
where the connection request comes from, and `originator port' is
the port on the originator host from where the connection came
from.
Forwarded TCP/IP channels are independent of any sessions, and
closing a session channel does not in any way imply that forwarded
connections should be closed.
Client implementations SHOULD reject direct TCP/IP open requests
for security reasons.
6. Encoding of Terminal Modes
Terminal modes (as passed in a pty request) are encoded into a
byte stream. It is intended that the coding be portable across
different environments.
The tty mode description is a stream of bytes. The stream
consists of opcode-argument pairs. It is terminated by opcode
TTY_OP_END (0). Opcodes 1 to 159 have a single uint32 argument.
Opcodes 160 to 255 are not yet defined, and cause parsing to stop
(they should only be used after any other data).
The client SHOULD put in the stream any modes it knows about, and
the server MAY ignore any modes it does not know about. This
allows some degree of machine-independence, at least between
systems that use a POSIX-like tty interface. The protocol can
support other systems as well, but the client may need to fill
reasonable values for a number of parameters so the server pty
gets set to a reasonable mode (the server leaves all unspecified
mode bits in their default values, and only some combinations make
sense).
The following opcodes have been defined. The naming of opcodes
mostly follows the POSIX terminal mode flags.
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.
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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 set, 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.
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
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(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.
7. Summary of Message Numbers
#define SSH_MSG_GLOBAL_REQUEST 80
#define SSH_MSG_REQUEST_SUCCESS 81
#define SSH_MSG_REQUEST_FAILURE 82
#define SSH_MSG_CHANNEL_OPEN 90
#define SSH_MSG_CHANNEL_OPEN_CONFIRMATION 91
#define SSH_MSG_CHANNEL_OPEN_FAILURE 92
#define SSH_MSG_CHANNEL_WINDOW_ADJUST 93
#define SSH_MSG_CHANNEL_DATA 94
#define SSH_MSG_CHANNEL_EXTENDED_DATA 95
#define SSH_MSG_CHANNEL_EOF 96
#define SSH_MSG_CHANNEL_CLOSE 97
#define SSH_MSG_CHANNEL_REQUEST 98
#define SSH_MSG_CHANNEL_SUCCESS 99
#define SSH_MSG_CHANNEL_FAILURE 100
8. Security Considerations
This protocol is assumed to run on top of a secure, authenticated
transport. User authentication and protection against network-
level attacks are assumed to be provided by the underlying
protocols.
It is RECOMMENDED that implementations disable all the potentially
dangerous features (e.g. agent forwarding, X11 forwarding, and
TCP/IP forwarding) if the host key has changed.
Full security considerations for this protocol are provided in
Section 8 of [SSH-ARCH]
9. Intellectual Property
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described
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in this document or the extent to which any license under such
rights might or might not be available; neither does it represent
that it has made any effort to identify any such rights.
Information on the IETF's procedures with respect to rights in
standards-track and standards-related documentation can be found
in BCP-11. Copies of claims of rights made available for
publication and any assurances of licenses to be made available,
or the result of an attempt made to obtain a general license or
permission for the use of such proprietary rights by implementers
or users of this specification can be obtained from the IETF
Secretariat.
The IETF has been notified of intellectual property rights claimed
in regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights.
10. Additional Information
The current document editor is: Darren.Moffat@Sun.COM. Comments
on this internet draft should be sent to the IETF SECSH working
group, details at: http://ietf.org/html.charters/secsh-
charter.html
References
[RFC1766] Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766, March 1995.
[RFC1884] Hinden, R., Deering, S. and Editors, "IP Version 6
Addressing Architecture", RFC 1884, December 1995.
[RFC2279] Yergeau, F., "UTF-8, a transformation format of
ISO 10646", RFC 2279, January 1998.
[SCHEIFLER] Scheifler, R., "X Window System : The Complete
Reference to Xlib, X Protocol, Icccm, Xlfd, 3rd
edition.", Digital Press ISBN 1555580882, Feburary
1992.
[POSIX] ISO/IEC, 9945-1., "Information technology --
Portable Operating System Interface (POSIX)-Part
1: System Application Program Interface (API) C
Language", ANSI/IEE Std 1003.1, July 1996.
[SSH-ARCH] Ylonen, T., "SSH Protocol Architecture", I-D
draft-ietf-architecture-14.txt, July 2003.
Ylonen, et. al. Expires January 12, 2004 [Page 19]
Internet-Draft SSH Connection Protocol July 2003
[SSH-TRANS] Ylonen, T., "SSH Transport Layer Protocol", I-D
draft-ietf-transport-16.txt, July 2003.
[SSH-USERAUTH] Ylonen, T., "SSH Authentication Protocol", I-D
draft-ietf-userauth-17.txt, July 2003.
[SSH-CONNECT] Ylonen, T., "SSH Connection Protocol", I-D draft-
ietf-connect-17.txt, July 2003.
[SSH-NUMBERS] Lehtinen, S. and D. Moffat, "SSH Protocol Assigned
Numbers", I-D draft-ietf-secsh-assignednumbers-
03.txt, July 2003.
Authors' Addresses
Tatu Ylonen
SSH Communications Security Corp
Fredrikinkatu 42
HELSINKI FIN-00100
Finland
EMail: ylo@ssh.com
Tero Kivinen
SSH Communications Security Corp
Fredrikinkatu 42
HELSINKI FIN-00100
Finland
EMail: kivinen@ssh.com
Markku-Juhani O. Saarinen
University of Jyvaskyla
Timo J. Rinne
SSH Communications Security Corp
Fredrikinkatu 42
HELSINKI FIN-00100
Finland
EMail: tri@ssh.com
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Sami Lehtinen
SSH Communications Security Corp
Fredrikinkatu 42
HELSINKI FIN-00100
Finland
EMail: sjl@ssh.com
Ylonen, et. al. Expires January 12, 2004 [Page 21]
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Ylonen, et. al. Expires January 12, 2004 [Page 22]
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