Revert part of 180714 - the intent was to flatten dist, not to nuke it.

1 files changed, 1105 insertions, 0 deletions

diff --git a/crypto/openssh/ssh_config.5 b/crypto/openssh/ssh_config.5
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+.\"  -*- nroff -*-
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\"                    All rights reserved
+.\"
+.\" As far as I am concerned, the code I have written for this software
+.\" can be used freely for any purpose.  Any derived versions of this
+.\" software must be clearly marked as such, and if the derived work is
+.\" incompatible with the protocol description in the RFC file, it must be
+.\" called by a name other than "ssh" or "Secure Shell".
+.\"
+.\" Copyright (c) 1999,2000 Markus Friedl.  All rights reserved.
+.\" Copyright (c) 1999 Aaron Campbell.  All rights reserved.
+.\" Copyright (c) 1999 Theo de Raadt.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" $OpenBSD: ssh_config.5,v 1.97 2006/07/27 08:00:50 jmc Exp $
+.Dd September 25, 1999
+.Dt SSH_CONFIG 5
+.Os
+.Sh NAME
+.Nm ssh_config
+.Nd OpenSSH SSH client configuration files
+.Sh SYNOPSIS
+.Bl -tag -width Ds -compact
+.It Pa ~/.ssh/config
+.It Pa /etc/ssh/ssh_config
+.El
+.Sh DESCRIPTION
+.Xr ssh 1
+obtains configuration data from the following sources in
+the following order:
+.Pp
+.Bl -enum -offset indent -compact
+.It
+command-line options
+.It
+user's configuration file
+.Pq Pa ~/.ssh/config
+.It
+system-wide configuration file
+.Pq Pa /etc/ssh/ssh_config
+.El
+.Pp
+For each parameter, the first obtained value
+will be used.
+The configuration files contain sections separated by
+.Dq Host
+specifications, and that section is only applied for hosts that
+match one of the patterns given in the specification.
+The matched host name is the one given on the command line.
+.Pp
+Since the first obtained value for each parameter is used, more
+host-specific declarations should be given near the beginning of the
+file, and general defaults at the end.
+.Pp
+The configuration file has the following format:
+.Pp
+Empty lines and lines starting with
+.Ql #
+are comments.
+Otherwise a line is of the format
+.Dq keyword arguments .
+Configuration options may be separated by whitespace or
+optional whitespace and exactly one
+.Ql = ;
+the latter format is useful to avoid the need to quote whitespace
+when specifying configuration options using the
+.Nm ssh ,
+.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
+keywords are case-insensitive and arguments are case-sensitive):
+.Bl -tag -width Ds
+.It Cm Host
+Restricts the following declarations (up to the next
+.Cm Host
+keyword) to be only for those hosts that match one of the patterns
+given after the keyword.
+A single
+.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
+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
+.Dq inet6
+(use IPv6 only).
+.It Cm BatchMode
+If set to
+.Dq yes ,
+passphrase/password querying will be disabled.
+This option is useful in scripts and other batch jobs where no user
+is present to supply the password.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm BindAddress
+Use the specified address on the local machine as the source address of
+the connection.
+Only useful on systems with more than one address.
+Note that this option does not work if
+.Cm UsePrivilegedPort
+is set to
+.Dq yes .
+.It Cm ChallengeResponseAuthentication
+Specifies whether to use challenge-response authentication.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq yes .
+.It Cm CheckHostIP
+If this flag is set to
+.Dq yes ,
+.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.
+If the option is set to
+.Dq no ,
+the check will not be executed.
+The default is
+.Dq yes .
+.It Cm Cipher
+Specifies the cipher to use for encrypting the session
+in protocol version 1.
+Currently,
+.Dq blowfish ,
+.Dq 3des ,
+and
+.Dq des
+are supported.
+.Ar des
+is only supported in the
+.Xr ssh 1
+client for interoperability with legacy protocol 1 implementations
+that do not support the
+.Ar 3des
+cipher.
+Its use is strongly discouraged due to cryptographic weaknesses.
+The default is
+.Dq 3des .
+.It Cm Ciphers
+Specifies the ciphers allowed for protocol version 2
+in order of preference.
+Multiple ciphers must be comma-separated.
+The supported ciphers are
+.Dq 3des-cbc ,
+.Dq aes128-cbc ,
+.Dq aes192-cbc ,
+.Dq aes256-cbc ,
+.Dq aes128-ctr ,
+.Dq aes192-ctr ,
+.Dq aes256-ctr ,
+.Dq arcfour128 ,
+.Dq arcfour256 ,
+.Dq arcfour ,
+.Dq blowfish-cbc ,
+and
+.Dq cast128-cbc .
+The default is:
+.Bd -literal -offset 3n
+aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
+arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
+aes192-ctr,aes256-ctr
+.Ed
+.It Cm ClearAllForwardings
+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
+.Xr ssh 1
+command line to clear port forwardings set in
+configuration files, and is automatically set by
+.Xr scp 1
+and
+.Xr sftp 1 .
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm Compression
+Specifies whether to use compression.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm CompressionLevel
+Specifies the compression level to use if compression is enabled.
+The argument must be an integer from 1 (fast) to 9 (slow, best).
+The default level is 6, which is good for most applications.
+The meaning of the values is the same as in
+.Xr gzip 1 .
+Note that this option applies to protocol version 1 only.
+.It Cm ConnectionAttempts
+Specifies the number of tries (one per second) to make before exiting.
+The argument must be an integer.
+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 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 ,
+.Xr ssh 1
+will listen for connections on a control socket specified using the
+.Cm ControlPath
+argument.
+Additional sessions can connect to this socket using the same
+.Cm ControlPath
+with
+.Cm ControlMaster
+set to
+.Dq no
+(the default).
+These sessions will try to reuse the master instance's network connection
+rather than initiating new ones, but will fall back to connecting normally
+if the control socket does not exist, or is not listening.
+.Pp
+Setting this to
+.Dq ask
+will cause ssh
+to listen for control connections, but require confirmation using the
+.Ev SSH_ASKPASS
+program before they are accepted (see
+.Xr ssh-add 1
+for details).
+If the
+.Cm ControlPath
+cannot be opened,
+ssh will continue without connecting to a master instance.
+.Pp
+X11 and
+.Xr ssh-agent 1
+forwarding is supported over these multiplexed connections, however the
+display and agent forwarded will be the one belonging to the master
+connection i.e. it is not possible to forward multiple displays or agents.
+.Pp
+Two additional options allow for opportunistic multiplexing: try to use a
+master connection but fall back to creating a new one if one does not already
+exist.
+These options are:
+.Dq auto
+and
+.Dq autoask .
+The latter requires confirmation like the
+.Dq ask
+option.
+.It Cm ControlPath
+Specify the path to the control socket used for connection sharing as described
+in the
+.Cm ControlMaster
+section above or the string
+.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
+.Ql %r
+by the remote login username.
+It is recommended that any
+.Cm ControlPath
+used for opportunistic connection sharing include
+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
+over the secure channel, and the application
+protocol is then used to determine where to connect to from the
+remote machine.
+.Pp
+The argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port .
+.Sm on
+IPv6 addresses can be specified by enclosing addresses in square brackets or
+by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port .
+By default, the local port is bound in accordance with the
+.Cm GatewayPorts
+setting.
+However, an explicit
+.Ar bind_address
+may be used to bind the connection to a specific address.
+The
+.Ar bind_address
+of
+.Dq localhost
+indicates that the listening port be bound for local use only, while an
+empty address or
+.Sq *
+indicates that the port should be available from all interfaces.
+.Pp
+Currently the SOCKS4 and SOCKS5 protocols are supported, and
+.Xr ssh 1
+will act as a SOCKS server.
+Multiple forwardings may be specified, and
+additional forwardings can be given on the command line.
+Only the superuser can forward privileged ports.
+.It Cm EnableSSHKeysign
+Setting this option to
+.Dq yes
+in the global client configuration file
+.Pa /etc/ssh/ssh_config
+enables the use of the helper program
+.Xr ssh-keysign 8
+during
+.Cm HostbasedAuthentication .
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+This option should be placed in the non-hostspecific section.
+See
+.Xr ssh-keysign 8
+for more information.
+.It Cm EscapeChar
+Sets the escape character (default:
+.Ql ~ ) .
+The escape character can also
+be set on the command line.
+The argument should be a single character,
+.Ql ^
+followed by a letter, or
+.Dq none
+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
+or
+.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.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.Pp
+Agent forwarding should be enabled with caution.
+Users with the ability to bypass file permissions on the remote host
+(for the agent's Unix-domain socket)
+can access the local agent through the forwarded connection.
+An attacker cannot obtain key material from the agent,
+however they can perform operations on the keys that enable them to
+authenticate using the identities loaded into the agent.
+.It Cm ForwardX11
+Specifies whether X11 connections will be automatically redirected
+over the secure channel and
+.Ev DISPLAY
+set.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.Pp
+X11 forwarding should be enabled with caution.
+Users with the ability to bypass file permissions on the remote host
+(for the user's X11 authorization database)
+can access the local X11 display through the forwarded connection.
+An attacker may then be able to perform activities such as keystroke monitoring
+if the
+.Cm ForwardX11Trusted
+option is also enabled.
+.It Cm ForwardX11Trusted
+If this option is set to
+.Dq yes ,
+remote X11 clients will have full access to the original X11 display.
+.Pp
+If this option is set to
+.Dq no ,
+remote X11 clients will be considered untrusted and prevented
+from stealing or tampering with data belonging to trusted X11
+clients.
+Furthermore, the
+.Xr xauth 1
+token used for the session will be set to expire after 20 minutes.
+Remote clients will be refused access after this time.
+.Pp
+The default is
+.Dq no .
+.Pp
+See the X11 SECURITY extension specification for full details on
+the restrictions imposed on untrusted clients.
+.It Cm GatewayPorts
+Specifies whether remote hosts are allowed to connect to local
+forwarded ports.
+By default,
+.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 ssh
+should bind local port forwardings to the wildcard address,
+thus allowing remote hosts to connect to forwarded ports.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm GlobalKnownHostsFile
+Specifies a file to use for the global
+host key database instead of
+.Pa /etc/ssh/ssh_known_hosts .
+.It Cm GSSAPIAuthentication
+Specifies whether user authentication based on GSSAPI is allowed.
+The default is
+.Dq no .
+Note that this option applies to protocol version 2 only.
+.It Cm GSSAPIDelegateCredentials
+Forward (delegate) credentials to the server.
+The default is
+.Dq no .
+Note that this option applies to protocol version 2 only.
+.It Cm HashKnownHosts
+Indicates that
+.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
+.Xr ssh 1
+and
+.Xr sshd 8 ,
+but they do not reveal identifying information should the file's contents
+be disclosed.
+The default is
+.Dq no .
+Note that existing names and addresses in known hosts files
+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
+authentication.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+This option applies to protocol version 2 only and
+is similar to
+.Cm RhostsRSAAuthentication .
+.It Cm HostKeyAlgorithms
+Specifies the protocol version 2 host key algorithms
+that the client wants to use in order of preference.
+The default for this option is:
+.Dq ssh-rsa,ssh-dss .
+.It Cm HostKeyAlias
+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
+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.
+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
+.Xr ssh 1
+should only use the authentication identity files configured in the
+.Nm
+files,
+even if
+.Xr ssh-agent 1
+offers more identities.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+This option is intended for situations where ssh-agent
+offers many different identities.
+The default is
+.Dq no .
+.It Cm IdentityFile
+Specifies a file from which the user's RSA or DSA authentication identity
+is read.
+The default is
+.Pa ~/.ssh/identity
+for protocol version 1, and
+.Pa ~/.ssh/id_rsa
+and
+.Pa ~/.ssh/id_dsa
+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 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.
+.It Cm KbdInteractiveDevices
+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.
+The command string extends to the end of the line, and is executed with
+.Pa /bin/sh .
+This directive is ignored unless
+.Cm PermitLocalCommand
+has been enabled.
+.It Cm LocalForward
+Specifies that a TCP port on the local machine be forwarded over
+the secure channel to the specified host and port from the remote machine.
+The first argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port
+.Sm on
+and the second argument must be
+.Ar host : Ns Ar hostport .
+IPv6 addresses can be specified by enclosing addresses in square brackets or
+by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port
+and
+.Ar host Ns / Ns Ar hostport .
+Multiple forwardings may be specified, and additional forwardings can be
+given on the command line.
+Only the superuser can forward privileged ports.
+By default, the local port is bound in accordance with the
+.Cm GatewayPorts
+setting.
+However, an explicit
+.Ar bind_address
+may be used to bind the connection to a specific address.
+The
+.Ar bind_address
+of
+.Dq localhost
+indicates that the listening port be bound for local use only, while an
+empty address or
+.Sq *
+indicates that the port should be available from all interfaces.
+.It Cm LogLevel
+Gives the verbosity level that is used when logging messages from
+.Xr ssh 1 .
+The possible values are:
+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.
+.It Cm MACs
+Specifies the MAC (message authentication code) algorithms
+in order of preference.
+The MAC algorithm is used in protocol version 2
+for data integrity protection.
+Multiple algorithms must be comma-separated.
+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.
+In this case localhost will refer to a different machine on each of
+the machines and the user will get many warnings about changed host keys.
+However, this option disables host authentication for localhost.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+The default is to check the host key for localhost.
+.It Cm NumberOfPasswordPrompts
+Specifies the number of password prompts before giving up.
+The argument to this keyword must be an integer.
+The default is 3.
+.It Cm PasswordAuthentication
+Specifies whether to use password authentication.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq yes .
+.It Cm PermitLocalCommand
+Allow local command execution via the
+.Ic LocalCommand
+option or using the
+.Ic !\& Ns Ar command
+escape sequence in
+.Xr ssh 1 .
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm Port
+Specifies the port number to connect on the remote host.
+The default is 22.
+.It Cm PreferredAuthentications
+Specifies the order in which the client should try protocol 2
+authentication methods.
+This allows a client to prefer one method (e.g.\&
+.Cm keyboard-interactive )
+over another method (e.g.\&
+.Cm password )
+The default for this option is:
+.Do gssapi-with-mic ,
+hostbased,
+publickey,
+keyboard-interactive,
+password
+.Dc .
+.It Cm Protocol
+Specifies the protocol versions
+.Xr ssh 1
+should support in order of preference.
+The possible values are
+.Sq 1
+and
+.Sq 2 .
+Multiple versions must be comma-separated.
+The default is
+.Dq 2,1 .
+This means that ssh
+tries version 2 and falls back to version 1
+if version 2 is not available.
+.It Cm ProxyCommand
+Specifies the command to use to connect to the server.
+The command
+string extends to the end of the line, and is executed with
+.Pa /bin/sh .
+In the command string,
+.Ql %h
+will be substituted by the host name to
+connect and
+.Ql %p
+by the port.
+The command can be basically anything,
+and should read from its standard input and write to its standard output.
+It should eventually connect an
+.Xr sshd 8
+server running on some machine, or execute
+.Ic sshd -i
+somewhere.
+Host key management will be done using the
+HostName of the host being connected (defaulting to the name typed by
+the user).
+Setting the command to
+.Dq none
+disables this option entirely.
+Note that
+.Cm CheckHostIP
+is not available for connects with a proxy command.
+.Pp
+This directive is useful in conjunction with
+.Xr nc 1
+and its proxy support.
+For example, the following directive would connect via an HTTP proxy at
+192.0.2.0:
+.Bd -literal -offset 3n
+ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
+.Ed
+.It Cm PubkeyAuthentication
+Specifies whether to try public key authentication.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq yes .
+This option applies to protocol version 2 only.
+.It Cm RekeyLimit
+Specifies the maximum amount of data that may be transmitted before the
+session key is renegotiated.
+The argument is the number of bytes, with an optional suffix of
+.Sq K ,
+.Sq M ,
+or
+.Sq G
+to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
+The default is between
+.Sq 1G
+and
+.Sq 4G ,
+depending on the cipher.
+This option applies to protocol version 2 only.
+.It Cm RemoteForward
+Specifies that a TCP port on the remote machine be forwarded over
+the secure channel to the specified host and port from the local machine.
+The first argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port
+.Sm on
+and the second argument must be
+.Ar host : Ns Ar hostport .
+IPv6 addresses can be specified by enclosing addresses in square brackets
+or by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port
+and
+.Ar host Ns / Ns Ar hostport .
+Multiple forwardings may be specified, and additional
+forwardings can be given on the command line.
+Only the superuser can forward privileged ports.
+.Pp
+If the
+.Ar bind_address
+is not specified, the default is to only bind to loopback addresses.
+If the
+.Ar bind_address
+is
+.Ql *
+or an empty string, then the forwarding is requested to listen on all
+interfaces.
+Specifying a remote
+.Ar bind_address
+will only succeed if the server's
+.Cm GatewayPorts
+option is enabled (see
+.Xr sshd_config 5 ) .
+.It Cm RhostsRSAAuthentication
+Specifies whether to try rhosts based authentication with RSA host
+authentication.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+This option applies to protocol version 1 only and requires
+.Xr ssh 1
+to be setuid root.
+.It Cm RSAAuthentication
+Specifies whether to try RSA authentication.
+The argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+RSA authentication will only be
+attempted if the identity file exists, or an authentication agent is
+running.
+The default is
+.Dq yes .
+Note that this option applies to protocol version 1 only.
+.It Cm SendEnv
+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 server must also support it, and the server must be configured to
+accept these environment variables.
+Refer to
+.Cm AcceptEnv
+in
+.Xr sshd_config 5
+for how to configure the server.
+Variables are specified by name, which may contain wildcard characters.
+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
+.Xr ssh 1
+receiving any messages back from the server.
+If this threshold is reached while server alive messages are being sent,
+ssh 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
+(below).
+The server alive messages are sent through the encrypted channel
+and therefore will not be spoofable.
+The TCP keepalive option enabled by
+.Cm TCPKeepAlive
+is spoofable.
+The server alive mechanism is valuable when the client or
+server depend on knowing when a connection has become inactive.
+.Pp
+The default value is 3.
+If, for example,
+.Cm ServerAliveInterval
+(see below) is set to 15 and
+.Cm ServerAliveCountMax
+is left at the default, if the server becomes unresponsive,
+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,
+.Xr ssh 1
+will send a message through the encrypted
+channel to request a response from the server.
+The default
+is 0, indicating that these messages will not be sent to the server.
+This option applies to protocol version 2 only.
+.It Cm SmartcardDevice
+Specifies which smartcard device to use.
+The argument to this keyword is the device
+.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 ,
+.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,
+though it can be annoying when the
+.Pa /etc/ssh/ssh_known_hosts
+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 ,
+ssh 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
+ssh 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 ,
+or
+.Dq ask .
+The default is
+.Dq ask .
+.It Cm TCPKeepAlive
+Specifies whether the system should send TCP keepalive messages to the
+other side.
+If they are sent, death of the connection or crash of one
+of the machines will be properly noticed.
+However, this means that
+connections will die if the route is down temporarily, and some people
+find it annoying.
+.Pp
+The default is
+.Dq yes
+(to send TCP keepalive messages), and the client will notice
+if the network goes down or the remote host dies.
+This is important in scripts, and many users want it too.
+.Pp
+To disable TCP keepalive messages, the value should be set to
+.Dq no .
+.It Cm Tunnel
+Request
+.Xr tun 4
+device forwarding between the client and the server.
+The argument must be
+.Dq yes ,
+.Dq point-to-point
+(layer 3),
+.Dq ethernet
+(layer 2),
+or
+.Dq no .
+Specifying
+.Dq yes
+requests the default tunnel mode, which is
+.Dq point-to-point .
+The default is
+.Dq no .
+.It Cm TunnelDevice
+Specifies the
+.Xr tun 4
+devices to open on the client
+.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.
+If
+.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
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+If set to
+.Dq yes ,
+.Xr ssh 1
+must be setuid root.
+Note that this option must be set to
+.Dq yes
+for
+.Cm RhostsRSAAuthentication
+with older servers.
+.It Cm User
+Specifies the user to log in as.
+This can be useful when a different user name is used on different machines.
+This saves the trouble of
+having to remember to give the user name on the command line.
+.It Cm UserKnownHostsFile
+Specifies a file to use for the user
+host key database instead of
+.Pa ~/.ssh/known_hosts .
+.It Cm VerifyHostKeyDNS
+Specifies whether to verify the remote key using DNS and SSHFP resource
+records.
+If this option is set to
+.Dq yes ,
+the client will implicitly trust keys that match a secure fingerprint
+from DNS.
+Insecure fingerprints will be handled as if this option was set to
+.Dq ask .
+If this option is set to
+.Dq ask ,
+information on fingerprint match will be displayed, but the user will still
+need to confirm new host keys according to the
+.Cm StrictHostKeyChecking
+option.
+The argument must be
+.Dq yes ,
+.Dq no ,
+or
+.Dq ask .
+The default is
+.Dq no .
+Note that this option applies to protocol version 2 only.
+.Pp
+See also
+.Sx VERIFYING HOST KEYS
+in
+.Xr ssh 1 .
+.It Cm XAuthLocation
+Specifies the full pathname of the
+.Xr xauth 1
+program.
+The default is
+.Pa /usr/X11R6/bin/xauth .
+.El
+.Sh PATTERNS
+A
+.Em pattern
+consists of zero or more non-whitespace characters,
+.Sq *
+(a wildcard that matches zero or more characters),
+or
+.Sq ?\&
+(a wildcard that matches exactly one character).
+For example, to specify a set of declarations for any host in the
+.Dq .co.uk
+set of domains,
+the following pattern could be used:
+.Pp
+.Dl Host *.co.uk
+.Pp
+The following pattern
+would match any host in the 192.168.0.[0-9] network range:
+.Pp
+.Dl Host 192.168.0.?
+.Pp
+A
+.Em pattern-list
+is a comma-separated list of patterns.
+Patterns within pattern-lists may be negated
+by preceding them with an exclamation mark
+.Pq Sq !\& .
+For example,
+to allow a key to be used from anywhere within an organisation
+except from the
+.Dq dialup
+pool,
+the following entry (in authorized_keys) could be used:
+.Pp
+.Dl from=\&"!*.dialup.example.com,*.example.com\&"
+.Sh FILES
+.Bl -tag -width Ds
+.It Pa ~/.ssh/config
+This is the per-user configuration file.
+The format of this file is described above.
+This file is used by the SSH client.
+Because of the potential for abuse, this file must have strict permissions:
+read/write for the user, and not accessible by others.
+.It Pa /etc/ssh/ssh_config
+Systemwide configuration file.
+This file provides defaults for those
+values that are not specified in the user's configuration file, and
+for those users who do not have a configuration file.
+This file must be world-readable.
+.El
+.Sh SEE ALSO
+.Xr ssh 1
+.Sh AUTHORS
+OpenSSH is a derivative of the original and free
+ssh 1.2.12 release by Tatu Ylonen.
+Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
+Theo de Raadt and Dug Song
+removed many bugs, re-added newer features and
+created OpenSSH.
+Markus Friedl contributed the support for SSH
+protocol versions 1.5 and 2.0.