src/usr.bin/ssh/ssh_config.5 - diff

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Diff for /src/usr.bin/ssh/ssh_config.5 between version 1.83 and 1.84

version 1.83, 2006/02/24 20:31:31

version 1.84, 2006/02/24 23:20:07

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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

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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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.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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.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

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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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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

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

.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

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.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.

.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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The argument must be

.Dq yes ,

.Dq point-to-point ,

.Dq ethernet

.Dq ethernet ,

.Dq no .

The default is

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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