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Diff for /src/usr.bin/ssh/ssh_config.5 between version 1.61.2.1 and 1.61.2.2

version 1.61.2.1, 2006/02/03 03:01:58

version 1.61.2.2, 2006/10/06 03:19:33

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.It Pa /etc/ssh/ssh_config

.El

.Sh DESCRIPTION

.Nm ssh

.Xr ssh 1

obtains configuration data from the following sources in

the following order:

.Pp

.Bl -enum -offset indent -compact

.It

command-line options

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Empty lines and lines starting with

.Ql #

are comments.

.Pp

Otherwise a line is of the format

.Dq keyword arguments .

Configuration options may be separated by whitespace or

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the latter format is useful to avoid the need to quote whitespace

when specifying configuration options using the

.Nm ssh ,

.Nm scp

.Nm scp ,

and

.Nm sftp

.Fl o

option.

Arguments may optionally be enclosed in double quotes

.Pq \&"

in order to represent arguments containing spaces.

.Pp

The possible

keywords and their meanings are as follows (note that

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.Cm Host

keyword) to be only for those hosts that match one of the patterns

given after the keyword.

.Ql \&*

and

.Ql \&?

can be used as wildcards in the

patterns.

A single

.Ql \&*

.Ql *

as a pattern can be used to provide global

defaults for all hosts.

The host is the

.Ar hostname

argument given on the command line (i.e., the name is not converted to

argument given on the command line (i.e. the name is not converted to

a canonicalized host name before matching).

.Pp

See

.Sx PATTERNS

for more information on patterns.

.It Cm AddressFamily

Specifies which address family to use when connecting.

Valid arguments are

.Dq any ,

.Dq inet

(use IPv4 only) or

(use IPv4 only), or

.Dq inet6

(use IPv6 only).

.It Cm BatchMode

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is set to

.Dq yes .

.It Cm ChallengeResponseAuthentication

Specifies whether to use challenge response authentication.

Specifies whether to use challenge-response authentication.

The argument to this keyword must be

.Dq yes

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.It Cm CheckHostIP

If this flag is set to

.Dq yes ,

ssh will additionally check the host IP address in the

.Xr ssh 1

will additionally check the host IP address in the

.Pa known_hosts

file.

This allows ssh to detect if a host key changed due to DNS spoofing.

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are supported.

.Ar des

is only supported in the

.Nm ssh

.Xr ssh 1

client for interoperability with legacy protocol 1 implementations

that do not support the

.Ar 3des

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.Dq blowfish-cbc ,

and

.Dq cast128-cbc .

The default is

The default is:

.Bd -literal

.Bd -literal -offset 3n

``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,

aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,

arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,

aes192-ctr,aes256-ctr''

aes192-ctr,aes256-ctr

.Ed

.It Cm ClearAllForwardings

Specifies that all local, remote and dynamic port forwardings

Specifies that all local, remote, and dynamic port forwardings

specified in the configuration files or on the command line be

cleared.

This option is primarily useful when used from the

.Nm ssh

.Xr ssh 1

command line to clear port forwardings set in

configuration files, and is automatically set by

.Xr scp 1

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This may be useful in scripts if the connection sometimes fails.

The default is 1.

.It Cm ConnectTimeout

Specifies the timeout (in seconds) used when connecting to the ssh

Specifies the timeout (in seconds) used when connecting to the

server, instead of using the default system TCP timeout.

SSH server, instead of using the default system TCP timeout.

This value is used only when the target is down or really unreachable,

not when it refuses the connection.

.It Cm ControlMaster

Enables the sharing of multiple sessions over a single network connection.

When set to

.Dq yes

.Dq yes ,

.Nm ssh

.Xr ssh 1

will listen for connections on a control socket specified using the

.Cm ControlPath

argument.

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.Pp

Setting this to

.Dq ask

will cause

will cause ssh

.Nm ssh

to listen for control connections, but require confirmation using the

.Ev SSH_ASKPASS

program before they are accepted (see

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for details).

If the

.Cm ControlPath

can not be opened,

cannot be opened,

.Nm ssh

ssh will continue without connecting to a master instance.

will continue without connecting to a master instance.

.Pp

X11 and

.Xr ssh-agent 1

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.Dq none

to disable connection sharing.

In the path,

.Ql %l

will be substituted by the local host name,

.Ql %h

will be substituted by the target host name,

.Ql %p

the port and

the port, and

.Ql %r

by the remote login username.

It is recommended that any

.Cm ControlPath

used for opportunistic connection sharing include

all three of these escape sequences.

at least %h, %p, and %r.

This ensures that shared connections are uniquely identified.

.It Cm DynamicForward

Specifies that a TCP port on the local machine be forwarded

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indicates that the port should be available from all interfaces.

.Pp

Currently the SOCKS4 and SOCKS5 protocols are supported, and

.Nm ssh

.Xr ssh 1

will act as a SOCKS server.

Multiple forwardings may be specified, and

additional forwardings can be given on the command line.

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to disable the escape

character entirely (making the connection transparent for binary

data).

.It Cm ExitOnForwardFailure

Specifies whether

.Xr ssh 1

should terminate the connection if it cannot set up all requested

dynamic, local, and remote port forwardings.

The argument must be

.Dq yes

.Dq no .

The default is

.Dq no .

.It Cm ForwardAgent

Specifies whether the connection to the authentication agent (if any)

will be forwarded to the remote machine.

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option is also enabled.

.It Cm ForwardX11Trusted

If this option is set to

.Dq yes

.Dq yes ,

then remote X11 clients will have full access to the original X11 display.

remote X11 clients will have full access to the original X11 display.

.Pp

If this option is set to

.Dq no

.Dq no ,

then remote X11 clients will be considered untrusted and prevented

remote X11 clients will be considered untrusted and prevented

from stealing or tampering with data belonging to trusted X11

clients.

Furthermore, the

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Specifies whether remote hosts are allowed to connect to local

forwarded ports.

By default,

.Nm ssh

.Xr ssh 1

binds local port forwardings to the loopback address.

This prevents other remote hosts from connecting to forwarded ports.

.Cm GatewayPorts

can be used to specify that

can be used to specify that ssh

.Nm ssh

should bind local port forwardings to the wildcard address,

thus allowing remote hosts to connect to forwarded ports.

The argument must be

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Note that this option applies to protocol version 2 only.

.It Cm HashKnownHosts

Indicates that

.Nm ssh

.Xr ssh 1

should hash host names and addresses when they are added to

.Pa ~/.ssh/known_hosts .

These hashed names may be used normally by

.Nm ssh

.Xr ssh 1

and

.Nm sshd ,

.Xr sshd 8 ,

but they do not reveal identifying information should the file's contents

be disclosed.

The default is

.Dq no .

Note that hashing of names and addresses will not be retrospectively applied

Note that existing names and addresses in known hosts files

to existing known hosts files, but these may be manually hashed using

will not be converted automatically,

but may be manually hashed using

.Xr ssh-keygen 1 .

.It Cm HostbasedAuthentication

Specifies whether to try rhosts based authentication with public key

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Specifies an alias that should be used instead of the

real host name when looking up or saving the host key

in the host key database files.

This option is useful for tunneling ssh connections

This option is useful for tunneling SSH connections

or for multiple servers running on a single host.

.It Cm HostName

Specifies the real host name to log into.

This can be used to specify nicknames or abbreviations for hosts.

Default is the name given on the command line.

The default is the name given on the command line.

Numeric IP addresses are also permitted (both on the command line and in

.Cm HostName

specifications).

.It Cm IdentitiesOnly

Specifies that

.Nm ssh

.Xr ssh 1

should only use the authentication identity files configured in the

.Nm

files,

even if the

even if

.Nm ssh-agent

.Xr ssh-agent 1

offers more identities.

The argument to this keyword must be

.Dq yes

.Dq no .

This option is intended for situations where

This option is intended for situations where ssh-agent

.Nm ssh-agent

offers many different identities.

The default is

.Dq no .

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for protocol version 2.

Additionally, any identities represented by the authentication agent

will be used for authentication.

.Pp

The file name may use the tilde

syntax to refer to a user's home directory.

syntax to refer to a user's home directory or one of the following

escape characters:

.Ql %d

(local user's home directory),

.Ql %u

(local user name),

.Ql %l

(local host name),

.Ql %h

(remote host name) or

.Ql %r

(remote user name).

.Pp

It is possible to have

multiple identity files specified in configuration files; all these

identities will be tried in sequence.

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Specifies the list of methods to use in keyboard-interactive authentication.

Multiple method names must be comma-separated.

The default is to use the server specified list.

The methods available vary depending on what the server supports.

For an OpenSSH server,

it may be zero or more of:

.Dq bsdauth ,

.Dq pam ,

and

.Dq skey .

.It Cm LocalCommand

Specifies a command to execute on the local machine after successfully

connecting to the server.

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indicates that the port should be available from all interfaces.

.It Cm LogLevel

Gives the verbosity level that is used when logging messages from

.Nm ssh .

.Xr ssh 1 .

The possible values are:

QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.

QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.

The default is INFO.

DEBUG and DEBUG1 are equivalent.

DEBUG2 and DEBUG3 each specify higher levels of verbose output.

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The MAC algorithm is used in protocol version 2

for data integrity protection.

Multiple algorithms must be comma-separated.

The default is

The default is:

.Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .

.It Cm NoHostAuthenticationForLocalhost

This option can be used if the home directory is shared across machines.

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.It Cm NumberOfPasswordPrompts

Specifies the number of password prompts before giving up.

The argument to this keyword must be an integer.

Default is 3.

The default is 3.

.It Cm PasswordAuthentication

Specifies whether to use password authentication.

The argument to this keyword must be

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.Dq no .

.It Cm Port

Specifies the port number to connect on the remote host.

Default is 22.

The default is 22.

.It Cm PreferredAuthentications

Specifies the order in which the client should try protocol 2

authentication methods.

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over another method (e.g.\&

.Cm password )

The default for this option is:

.Dq hostbased,publickey,keyboard-interactive,password .

.Do gssapi-with-mic ,

hostbased,

publickey,

keyboard-interactive,

password

.Dc .

.It Cm Protocol

Specifies the protocol versions

.Nm ssh

.Xr ssh 1

should support in order of preference.

The possible values are

.Dq 1

.Sq 1

and

.Dq 2 .

.Sq 2 .

Multiple versions must be comma-separated.

The default is

.Dq 2,1 .

This means that

This means that ssh

.Nm ssh

tries version 2 and falls back to version 1

if version 2 is not available.

.It Cm ProxyCommand

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.Sq G

to indicate Kilobytes, Megabytes, or Gigabytes, respectively.

The default is between

.Dq 1G

.Sq 1G

and

.Dq 4G ,

.Sq 4G ,

depending on the cipher.

This option applies to protocol version 2 only.

.It Cm RemoteForward

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The default is

.Dq no .

This option applies to protocol version 1 only and requires

.Nm ssh

.Xr ssh 1

to be setuid root.

.It Cm RSAAuthentication

Specifies whether to try RSA authentication.

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Specifies what variables from the local

.Xr environ 7

should be sent to the server.

Note that environment passing is only supported for protocol 2, the

Note that environment passing is only supported for protocol 2.

server must also support it, and the server must be configured to

The server must also support it, and the server must be configured to

accept these environment variables.

Refer to

.Cm AcceptEnv

.Xr sshd_config 5

for how to configure the server.

Variables are specified by name, which may contain the wildcard characters

Variables are specified by name, which may contain wildcard characters.

.Ql \&*

and

.Ql \&? .

Multiple environment variables may be separated by whitespace or spread

across multiple

.Cm SendEnv

directives.

The default is not to send any environment variables.

.Pp

See

.Sx PATTERNS

for more information on patterns.

.It Cm ServerAliveCountMax

Sets the number of server alive messages (see below) which may be

sent without

.Nm ssh

.Xr ssh 1

receiving any messages back from the server.

If this threshold is reached while server alive messages are being sent,

.Nm ssh

ssh will disconnect from the server, terminating the session.

will disconnect from the server, terminating the session.

It is important to note that the use of server alive messages is very

different from

.Cm TCPKeepAlive

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The default value is 3.

If, for example,

.Cm ServerAliveInterval

(see below) is set to 15, and

(see below) is set to 15 and

.Cm ServerAliveCountMax

is left at the default, if the server becomes unresponsive ssh

is left at the default, if the server becomes unresponsive,

will disconnect after approximately 45 seconds.

ssh will disconnect after approximately 45 seconds.

This option applies to protocol version 2 only.

.It Cm ServerAliveInterval

Sets a timeout interval in seconds after which if no data has been received

from the server,

.Nm ssh

.Xr ssh 1

will send a message through the encrypted

channel to request a response from the server.

The default

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.It Cm SmartcardDevice

Specifies which smartcard device to use.

The argument to this keyword is the device

.Nm ssh

.Xr ssh 1

should use to communicate with a smartcard used for storing the user's

private RSA key.

By default, no device is specified and smartcard support is not activated.

.It Cm StrictHostKeyChecking

If this flag is set to

.Dq yes ,

.Nm ssh

.Xr ssh 1

will never automatically add host keys to the

.Pa ~/.ssh/known_hosts

file, and refuses to connect to hosts whose host key has changed.

This provides maximum protection against trojan horse attacks,

however, can be annoying when the

though it can be annoying when the

.Pa /etc/ssh/ssh_known_hosts

file is poorly maintained, or connections to new hosts are

file is poorly maintained or when connections to new hosts are

frequently made.

This option forces the user to manually

add all new hosts.

If this flag is set to

.Dq no ,

.Nm ssh

ssh will automatically add new host keys to the

will automatically add new host keys to the

user known hosts files.

If this flag is set to

.Dq ask ,

new host keys

will be added to the user known host files only after the user

has confirmed that is what they really want to do, and

.Nm ssh

ssh will refuse to connect to hosts whose host key has changed.

will refuse to connect to hosts whose host key has changed.

The host keys of

known hosts will be verified automatically in all cases.

The argument must be

.Dq yes ,

.Dq no

.Dq no ,

.Dq ask .

The default is

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To disable TCP keepalive messages, the value should be set to

.Dq no .

.It Cm Tunnel

Request starting

Request

.Xr tun 4

device forwarding between the client and the server.

This option also allows requesting layer 2 (ethernet)

instead of layer 3 (point-to-point) tunneling from the server.

The argument must be

.Dq yes ,

.Dq point-to-point ,

.Dq point-to-point

(layer 3),

.Dq ethernet

(layer 2),

.Dq no .

Specifying

.Dq yes

requests the default tunnel mode, which is

.Dq point-to-point .

The default is

.Dq no .

.It Cm TunnelDevice

Force a specified

Specifies the

.Xr tun 4

device on the client.

devices to open on the client

Without this option, the next available device will be used.

.Pq Ar local_tun

and the server

.Pq Ar remote_tun .

.Pp

The argument must be

.Sm off

.Ar local_tun Op : Ar remote_tun .

.Sm on

The devices may be specified by numerical ID or the keyword

.Dq any ,

which uses the next available tunnel device.

.Ar remote_tun

is not specified, it defaults to

.Dq any .

The default is

.Dq any:any .

.It Cm UsePrivilegedPort

Specifies whether to use a privileged port for outgoing connections.

The argument must be

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The default is

.Dq no .

If set to

.Dq yes

.Dq yes ,

.Nm ssh

.Xr ssh 1

must be setuid root.

Note that this option must be set to

.Dq yes

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option.

The argument must be

.Dq yes ,

.Dq no

.Dq no ,

.Dq ask .

The default is

.Dq no .

Note that this option applies to protocol version 2 only.

.Pp