===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/ssh/ssh.1,v
retrieving revision 1.64
retrieving revision 1.64.2.8
diff -u -r1.64 -r1.64.2.8
--- src/usr.bin/ssh/ssh.1	2000/10/16 21:46:31	1.64
+++ src/usr.bin/ssh/ssh.1	2002/03/08 17:04:43	1.64.2.8
@@ -10,9 +10,9 @@
 .\" 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.
+.\" 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
@@ -34,27 +34,30 @@
 .\" (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.1,v 1.64 2000/10/16 21:46:31 markus Exp $
+.\" $OpenBSD: ssh.1,v 1.64.2.8 2002/03/08 17:04:43 brad Exp $
 .Dd September 25, 1999
 .Dt SSH 1
 .Os
 .Sh NAME
 .Nm ssh
-.Nd OpenSSH secure shell client (remote login program)
+.Nd OpenSSH SSH client (remote login program)
 .Sh SYNOPSIS
 .Nm ssh
 .Op Fl l Ar login_name
-.Op Ar hostname | user@hostname
+.Ar hostname | user@hostname
 .Op Ar command
 .Pp
 .Nm ssh
-.Op Fl afgknqtvxACNPTX246
+.Op Fl afgknqstvxACNPTX1246
+.Op Fl b Ar bind_address
 .Op Fl c Ar cipher_spec
 .Op Fl e Ar escape_char
 .Op Fl i Ar identity_file
 .Op Fl l Ar login_name
+.Op Fl m Ar mac_spec
 .Op Fl o Ar option
 .Op Fl p Ar port
+.Op Fl F Ar configfile
 .Oo Fl L Xo
 .Sm off
 .Ar port :
@@ -71,11 +74,12 @@
 .Sm on
 .Xc
 .Oc
-.Op Ar hostname | user@hostname
+.Op Fl D Ar port
+.Ar hostname | user@hostname
 .Op Ar command
 .Sh DESCRIPTION
 .Nm
-(Secure Shell) is a program for logging into a remote machine and for
+(SSH client) is a program for logging into a remote machine and for
 executing commands on a remote machine.
 It is intended to replace
 rlogin and rsh, and provide secure encrypted communications between
@@ -109,7 +113,7 @@
 This form of authentication alone is normally not
 allowed by the server because it is not secure.
 .Pp
-The second (and primary) authentication method is the
+The second authentication method is the
 .Pa rhosts
 or
 .Pa hosts.equiv
@@ -203,31 +207,38 @@
 .Pp
 .Ss SSH protocol version 2
 .Pp
-When a user connects using the protocol version 2
-different authentication methods are available:
-At first, the client attempts to authenticate using the public key method.
-If this method fails password authentication is tried.
+When a user connects using protocol version 2
+similar authentication methods are available.
+Using the default values for
+.Cm PreferredAuthentications ,
+the client will try to authenticate first using the hostbased method;
+if this method fails public key authentication is attempted,
+and finally if this method fails keyboard-interactive and
+password authentication are tried.
 .Pp
 The public key method is similar to RSA authentication described
-in the previous section except that the DSA algorithm is used
-instead of the patented RSA algorithm.
-The client uses his private DSA key
+in the previous section and allows the RSA or DSA algorithm to be used:
+The client uses his private key,
 .Pa $HOME/.ssh/id_dsa
+or
+.Pa $HOME/.ssh/id_rsa ,
 to sign the session identifier and sends the result to the server.
 The server checks whether the matching public key is listed in
-.Pa $HOME/.ssh/authorized_keys2
+.Pa $HOME/.ssh/authorized_keys
 and grants access if both the key is found and the signature is correct.
 The session identifier is derived from a shared Diffie-Hellman value
 and is only known to the client and the server.
 .Pp
 If public key authentication fails or is not available a password
 can be sent encrypted to the remote host for proving the user's identity.
-This protocol 2 implementation does not yet support Kerberos or
-S/Key authentication.
 .Pp
+Additionally,
+.Nm
+supports hostbased or challenge response authentication.
+.Pp
 Protocol 2 provides additional mechanisms for confidentiality
 (the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
-and integrity (hmac-sha1, hmac-md5).
+and integrity (hmac-md5, hmac-sha1).
 Note that protocol 1 lacks a strong mechanism for ensuring the
 integrity of the connection.
 .Pp
@@ -240,31 +251,8 @@
 the remote command or shell will be automatically encrypted.
 .Pp
 If a pseudo-terminal has been allocated (normal login session), the
-user can disconnect with
-.Ic ~. ,
-and suspend
-.Nm
-with
-.Ic ~^Z .
-All forwarded connections can be listed with
-.Ic ~#
-and if
-the session blocks waiting for forwarded X11 or TCP/IP
-connections to terminate, it can be backgrounded with
-.Ic ~&
-(this should not be used while the user shell is active, as it can cause the
-shell to hang).
-All available escapes can be listed with
-.Ic ~? .
+user may use the escape characters noted below.
 .Pp
-A single tilde character can be sent as
-.Ic ~~
-(or by following the tilde by a character other than those described above).
-The escape character must always follow a newline to be interpreted as
-special.
-The escape character can be changed in configuration files
-or on the command line.
-.Pp
 If no pseudo tty has been allocated, the
 session is transparent and can be used to reliably transfer binary
 data.
@@ -272,15 +260,60 @@
 .Dq none
 will also make the session transparent even if a tty is used.
 .Pp
-The session terminates when the command or shell in on the remote
-machine exists and all X11 and TCP/IP connections have been closed.
+The session terminates when the command or shell on the remote
+machine exits and all X11 and TCP/IP connections have been closed.
 The exit status of the remote program is returned as the exit status
 of
 .Nm ssh .
 .Pp
+.Ss Escape Characters
+.Pp
+When a pseudo terminal has been requested, ssh supports a number of functions
+through the use of an escape character.
+.Pp
+A single tilde character can be sent as
+.Ic ~~
+or by following the tilde by a character other than those described below.
+The escape character must always follow a newline to be interpreted as
+special.
+The escape character can be changed in configuration files using the
+.Cm EscapeChar
+configuration directive or on the command line by the
+.Fl e
+option.
+.Pp
+The supported escapes (assuming the default
+.Ql ~ )
+are:
+.Bl -tag -width Ds
+.It Cm ~.
+Disconnect
+.It Cm ~^Z
+Background ssh
+.It Cm ~#
+List forwarded connections
+.It Cm ~&
+Background ssh at logout when waiting for forwarded connection / X11 sessions
+to terminate
+.It Cm ~?
+Display a list of escape characters
+.It Cm ~R
+Request rekeying of the connection (only useful for SSH protocol version 2
+and if the peer supports it)
+.El
+.Pp
 .Ss X11 and TCP forwarding
 .Pp
-If the user is using X11 (the
+If the
+.Cm ForwardX11
+variable is set to
+.Dq yes
+(or, see the description of the
+.Fl X
+and
+.Fl x
+options described later)
+and the user is using X11 (the
 .Ev DISPLAY
 environment variable is set), the connection to the X11 display is
 automatically forwarded to the remote side in such a way that any X11
@@ -316,29 +349,24 @@
 .Pp
 If the user is using an authentication agent, the connection to the agent
 is automatically forwarded to the remote side unless disabled on
-command line or in a configuration file.
+the command line or in a configuration file.
 .Pp
 Forwarding of arbitrary TCP/IP connections over the secure channel can
-be specified either on command line or in a configuration file.
+be specified either on the command line or in a configuration file.
 One possible application of TCP/IP forwarding is a secure connection to an
-electronic purse; another is going trough firewalls.
+electronic purse; another is going through firewalls.
 .Pp
 .Ss Server authentication
 .Pp
 .Nm
 automatically maintains and checks a database containing
 identifications for all hosts it has ever been used with.
-RSA host keys are stored in
+Host keys are stored in
 .Pa $HOME/.ssh/known_hosts
-and
-DSA host keys are stored in
-.Pa $HOME/.ssh/known_hosts2
 in the user's home directory.
-Additionally, the files
+Additionally, the file
 .Pa /etc/ssh_known_hosts
-and
-.Pa /etc/ssh_known_hosts2
-are automatically checked for known hosts.
+is automatically checked for known hosts.
 Any new hosts are automatically added to the user's file.
 If a host's identification
 ever changes,
@@ -352,32 +380,41 @@
 .Cm StrictHostKeyChecking
 option (see below) can be used to prevent logins to machines whose
 host key is not known or has changed.
-.Sh OPTIONS
+.Pp
+The options are as follows:
 .Bl -tag -width Ds
 .It Fl a
 Disables forwarding of the authentication agent connection.
 .It Fl A
 Enables forwarding of the authentication agent connection.
 This can also be specified on a per-host basis in a configuration file.
-.It Fl c Ar blowfish|3des
+.It Fl b Ar bind_address
+Specify the interface to transmit from on machines with multiple
+interfaces or aliased addresses.
+.It Fl c Ar blowfish|3des|des
 Selects the cipher to use for encrypting the session.
 .Ar 3des
 is used by default.
 It is believed to be secure.
 .Ar 3des
 (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
-It is presumably more secure than the
-.Ar des
-cipher which is no longer fully supported in
-.Nm ssh .
 .Ar blowfish
 is a fast block cipher, it appears very secure and is much faster than
 .Ar 3des .
-.It Fl c Ar "3des-cbc,blowfish-cbc,arcfour,cast128-cbc"
+.Ar des
+is only supported in the
+.Nm
+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.
+.It Fl c Ar cipher_spec
 Additionally, for protocol version 2 a comma-separated list of ciphers can
 be specified in order of preference.
-Protocol version 2 supports 3DES, Blowfish, and CAST128 in CBC mode
-and Arcfour.
+See
+.Cm Ciphers
+for more information.
 .It Fl e Ar ch|^ch|none
 Sets the escape character for sessions with a pty (default:
 .Ql ~ ) .
@@ -406,23 +443,40 @@
 .It Fl g
 Allows remote hosts to connect to local forwarded ports.
 .It Fl i Ar identity_file
-Selects the file from which the identity (private key) for
-RSA authentication is read.
-Default is
+Selects a file from which the identity (private key) for
+RSA or DSA authentication is read.
+The default is
 .Pa $HOME/.ssh/identity
-in the user's home directory.
+for protocol version 1, and
+.Pa $HOME/.ssh/id_rsa
+and
+.Pa $HOME/.ssh/id_dsa
+for protocol version 2.
 Identity files may also be specified on
 a per-host basis in the configuration file.
 It is possible to have multiple
 .Fl i
 options (and multiple identities specified in
 configuration files).
+.It Fl I Ar smartcard_device
+Specifies which smartcard device to use. The argument is
+the device
+.Nm
+should use to communicate with a smartcard used for storing the user's
+private RSA key.
 .It Fl k
 Disables forwarding of Kerberos tickets and AFS tokens.
 This may also be specified on a per-host basis in the configuration file.
 .It Fl l Ar login_name
 Specifies the user to log in as on the remote machine.
 This also may be specified on a per-host basis in the configuration file.
+.It Fl m Ar mac_spec
+Additionally, for protocol version 2 a comma-separated list of MAC
+(message authentication code) algorithms can
+be specified in order of preference.
+See the
+.Cm MACs
+keyword for more information.
 .It Fl n
 Redirects stdin from
 .Pa /dev/null
@@ -445,36 +499,44 @@
 option.)
 .It Fl N
 Do not execute a remote command.
-This is usefull if you just want to forward ports
+This is useful for just forwarding ports
 (protocol version 2 only).
 .It Fl o Ar option
-Can be used to give options in the format used in the config file.
+Can be used to give options in the format used in the configuration file.
 This is useful for specifying options for which there is no separate
 command-line flag.
-The option has the same format as a line in the configuration file.
 .It Fl p Ar port
 Port to connect to on the remote host.
 This can be specified on a
 per-host basis in the configuration file.
 .It Fl P
 Use a non-privileged port for outgoing connections.
-This can be used if your firewall does
+This can be used if a firewall does
 not permit connections from privileged ports.
 Note that this option turns off
 .Cm RhostsAuthentication
 and
-.Cm RhostsRSAAuthentication .
+.Cm RhostsRSAAuthentication
+for older servers.
 .It Fl q
 Quiet mode.
 Causes all warning and diagnostic messages to be suppressed.
-Only fatal errors are displayed.
+.It Fl s
+May be used to request invocation of a subsystem on the remote system. Subsystems are a feature of the SSH2 protocol which facilitate the use
+of SSH as a secure transport for other applications (eg. sftp). The
+subsystem is specified as the remote command.
 .It Fl t
 Force pseudo-tty allocation.
 This can be used to execute arbitrary
 screen-based programs on a remote machine, which can be very useful,
 e.g., when implementing menu services.
+Multiple
+.Fl t
+options force tty allocation, even if
+.Nm
+has no local tty.
 .It Fl T
-Disable pseudo-tty allocation (protocol version 2 only).
+Disable pseudo-tty allocation.
 .It Fl v
 Verbose mode.
 Causes
@@ -482,10 +544,9 @@
 to print debugging messages about its progress.
 This is helpful in
 debugging connection, authentication, and configuration problems.
-The verbose mode is also used to display
-.Xr skey 1
-challenges, if the user entered "s/key" as password.
-Multiple -v options increases the verbosity.
+Multiple
+.Fl v
+options increases the verbosity.
 Maximum is 3.
 .It Fl x
 Disables X11 forwarding.
@@ -506,8 +567,16 @@
 slow connections, but will only slow down things on fast networks.
 The default value can be set on a host-by-host basis in the
 configuration files; see the
-.Cm Compress
+.Cm Compression
 option below.
+.It Fl F Ar configfile
+Specifies an alternative per-user configuration file.
+If a configuration file is given on the command line,
+the system-wide configuration file
+.Pq Pa /etc/ssh_config
+will be ignored.
+The default for the per-user configuration file is
+.Pa $HOME/.ssh/config .
 .It Fl L Ar port:host:hostport
 Specifies that the given port on the local (client) host is to be
 forwarded to the given host and port on the remote side.
@@ -539,6 +608,26 @@
 Port forwardings can also be specified in the configuration file.
 Privileged ports can be forwarded only when
 logging in as root on the remote machine.
+IPv6 addresses can be specified with an alternative syntax:
+.Ar port/host/hostport
+.It Fl D Ar port
+Specifies a local
+.Dq dynamic
+application-level port forwarding.
+This works by allocating a socket to listen to
+.Ar port
+on the local side, and whenever a connection is made to this port, the
+connection is forwarded over the secure channel, and the application
+protocol is then used to determine where to connect to from the
+remote machine.  Currently the SOCKS4 protocol is supported, and
+.Nm
+will act as a SOCKS4 server.
+Only root can forward privileged ports.
+Dynamic port forwardings can also be specified in the configuration file.
+.It Fl 1
+Forces
+.Nm
+to try protocol version 1 only.
 .It Fl 2
 Forces
 .Nm
@@ -554,7 +643,8 @@
 .El
 .Sh CONFIGURATION FILES
 .Nm
-obtains configuration data from the following sources (in this order):
+obtains configuration data from the following sources in
+the following order:
 command line options, user's configuration file
 .Pq Pa $HOME/.ssh/config ,
 and system-wide configuration file
@@ -579,9 +669,21 @@
 .Pp
 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.
+.Pp
 The possible
-keywords and their meanings are as follows (note that the
-configuration files are case-sensitive):
+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
@@ -607,34 +709,55 @@
 .Dq yes
 or
 .Dq no .
+This option applies to protocol version 1 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 you have no
-user to supply the password.
+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
+Specify the interface to transmit from on machines with multiple
+interfaces or aliased addresses.
+Note that this option does not work if
+.Cm UsePrivilegedPort
+is set to
+.Dq yes .
 .It Cm CheckHostIP
 If this flag is set to
 .Dq yes ,
-ssh will additionally check the host ip address in the
+ssh 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 blowfish ,
+.Dq 3des ,
 and
-.Dq 3des
+.Dq des
 are supported.
+.Ar des
+is only supported in the
+.Nm
+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
@@ -642,33 +765,59 @@
 in order of preference.
 Multiple ciphers must be comma-separated.
 The default is
-.Dq 3des-cbc,blowfish-cbc,cast128-cbc,arcfour .
+.Pp
+.Bd -literal
+  ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
+    aes192-cbc,aes256-cbc''
+.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
+.Nm
+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 enable.
+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 falling
 back to rsh or exiting.
 The argument must be an integer.
 This may be useful in scripts if the connection sometimes fails.
-.It Cm DSAAuthentication
-Specifies whether to try DSA authentication.
-The argument to this keyword must be
-.Dq yes
-or
-.Dq no .
-DSA authentication will only be
-attempted if a DSA identity file exists.
-Note that this option applies to protocol version 2 only.
+The default is 1.
+.It Cm DynamicForward
+Specifies that a TCP/IP 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.  The argument must be a port number.
+Currently the SOCKS4 protocol is supported, and
+.Nm
+will act as a SOCKS4 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 EscapeChar
 Sets the escape character (default:
 .Ql ~ ) .
@@ -694,6 +843,8 @@
 .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.
@@ -717,6 +868,15 @@
 .It Cm GatewayPorts
 Specifies whether remote hosts are allowed to connect to local
 forwarded ports.
+By default,
+.Nm
+binds local port forwardings to the loopback addresss.  This
+prevents other remote hosts from connecting to forwarded ports.
+.Cm GatewayPorts
+can be used to specify that
+.Nm
+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
@@ -724,8 +884,32 @@
 The default is
 .Dq no .
 .It Cm GlobalKnownHostsFile
-Specifies a file to use instead of
+Specifies a file to use for the global
+host key database instead of
 .Pa /etc/ssh_known_hosts .
+.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.
@@ -734,10 +918,14 @@
 .Cm HostName
 specifications).
 .It Cm IdentityFile
-Specifies the file from which the user's RSA authentication identity
-is read (default
+Specifies a file from which the user's RSA or DSA authentication identity
+is read. The default is
 .Pa $HOME/.ssh/identity
-in the user's home directory).
+for protocol version 1, and
+.Pa $HOME/.ssh/id_rsa
+and
+.Pa $HOME/.ssh/id_dsa
+for protocol version 2.
 Additionally, any identities represented by the authentication agent
 will be used for authentication.
 The file name may use the tilde
@@ -745,18 +933,8 @@
 It is possible to have
 multiple identity files specified in configuration files; all these
 identities will be tried in sequence.
-.It Cm IdentityFile2
-Specifies the file from which the user's DSA authentication identity
-is read (default
-.Pa $HOME/.ssh/id_dsa
-in the user's home directory).
-The file name may use the tilde
-syntax to refer to a user's home directory.
-It is possible to have
-multiple identity files specified in configuration files; all these
-identities will be tried in sequence.
 .It Cm KeepAlive
-Specifies whether the system should send keepalive messages to the
+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.
@@ -771,8 +949,7 @@
 This is important in scripts, and many users want it too.
 .Pp
 To disable keepalives, the value should be set to
-.Dq no
-in both the server and the client configuration files.
+.Dq no .
 .It Cm KerberosAuthentication
 Specifies whether Kerberos authentication will be used.
 The argument to this keyword must be
@@ -788,9 +965,11 @@
 .Dq no .
 .It Cm LocalForward
 Specifies that a TCP/IP port on the local machine be forwarded over
-the secure channel to given host:port from the remote machine.
+the secure channel to the specified host and port from the remote machine.
 The first argument must be a port number, and the second must be
-host:port.
+.Ar host:port .
+IPv6 addresses can be specified with an alternative syntax:
+.Ar host/port .
 Multiple forwardings may be specified, and additional
 forwardings can be given on the command line.
 Only the superuser can forward privileged ports.
@@ -798,8 +977,27 @@
 Gives the verbosity level that is used when logging messages from
 .Nm ssh .
 The possible values are:
-QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG.
-The default is INFO.
+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.
@@ -810,10 +1008,19 @@
 .Dq yes
 or
 .Dq no .
-Note that this option applies to both protocol version 1 and 2.
+The default is
+.Dq yes .
 .It Cm Port
 Specifies the port number to connect on the remote host.
 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:
+.Dq hostbased,publickey,keyboard-interactive,password .
 .It Cm Protocol
 Specifies the protocol versions
 .Nm
@@ -824,11 +1031,11 @@
 .Dq 2 .
 Multiple versions must be comma-separated.
 The default is
-.Dq 1,2 .
+.Dq 2,1 .
 This means that
 .Nm
-tries version 1 and falls back to version 2
-if version 1 is not available.
+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
@@ -854,11 +1061,22 @@
 .Cm CheckHostIP
 is not available for connects with a proxy command.
 .Pp
+.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 RemoteForward
 Specifies that a TCP/IP port on the remote machine be forwarded over
-the secure channel to given host:port from the local machine.
+the secure channel to the specified host and port from the local machine.
 The first argument must be a port number, and the second must be
-host:port.
+.Ar host:port .
+IPv6 addresses can be specified with an alternative syntax:
+.Ar host/port .
 Multiple forwardings may be specified, and additional
 forwardings can be given on the command line.
 Only the superuser can forward privileged ports.
@@ -871,19 +1089,25 @@
 authentication time on slow connections when rhosts authentication is
 not used.
 Most servers do not permit RhostsAuthentication because it
-is not secure (see RhostsRSAAuthentication).
+is not secure (see
+.Cm RhostsRSAAuthentication ) .
 The argument to this keyword must be
 .Dq yes
 or
 .Dq no .
+The default is
+.Dq yes .
+This option applies to protocol version 1 only.
 .It Cm RhostsRSAAuthentication
 Specifies whether to try rhosts based authentication with RSA host
 authentication.
-This is the primary authentication method for most sites.
 The argument must be
 .Dq yes
 or
 .Dq no .
+The default is
+.Dq yes .
+This option applies to protocol version 1 only.
 .It Cm RSAAuthentication
 Specifies whether to try RSA authentication.
 The argument to this keyword must be
@@ -893,43 +1117,59 @@
 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 SkeyAuthentication
-Specifies whether to use
-.Xr skey 1
-authentication.
+.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 no .
+.Dq yes .
+.It Cm SmartcardDevice
+Specifies which smartcard device to use. The argument to this keyword is
+the device
+.Nm
+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 will never automatically add host keys to the
+will never automatically add host keys to the
 .Pa $HOME/.ssh/known_hosts
-and
-.Pa $HOME/.ssh/known_hosts2
-files, and refuses to connect hosts whose host key has changed.
-This provides maximum protection against trojan horse attacks.
-However, it can be somewhat annoying if you don't have good
+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
 .Pa /etc/ssh_known_hosts
-and
-.Pa /etc/ssh_known_hosts2
-files installed and frequently
-connect new hosts.
-Basically this option forces the user to manually
-add any new hosts.
-Normally this option is disabled, and new hosts
-will automatically be added to the known host files.
+file is poorly maintained, or 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
+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
+will refuse to connect to hosts whose host key has changed.
 The host keys of
-known hosts will be verified automatically in either case.
+known hosts will be verified automatically in all cases.
 The argument must be
-.Dq yes
+.Dq yes ,
+.Dq no
 or
-.Dq no .
+.Dq ask .
+The default is
+.Dq ask .
 .It Cm UsePrivilegedPort
 Specifies whether to use a privileged port for outgoing connections.
 The argument must be
@@ -937,20 +1177,22 @@
 or
 .Dq no .
 The default is
-.Dq yes .
-Note that setting this option to
-.Dq no
-turns off
+.Dq no .
+Note that this option must be set to
+.Dq yes
+if
 .Cm RhostsAuthentication
 and
-.Cm RhostsRSAAuthentication .
+.Cm RhostsRSAAuthentication
+authentications are needed with older servers.
 .It Cm User
 Specifies the user to log in as.
-This can be useful if you have a different user name on different machines.
+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 instead of
+Specifies a file to use for the user
+host key database instead of
 .Pa $HOME/.ssh/known_hosts .
 .It Cm UseRsh
 Specifies that rlogin/rsh should be used for this host.
@@ -992,7 +1234,9 @@
 .Nm
 uses this special value to forward X11 connections over the secure
 channel.
-The user should normally not set DISPLAY explicitly, as that
+The user should normally not set
+.Ev DISPLAY
+explicitly, as that
 will render the X11 connection insecure (and will require the user to
 manually copy any required authorization cookies).
 .It Ev HOME
@@ -1002,20 +1246,47 @@
 .Ev USER ;
 set for compatibility with systems that use this variable.
 .It Ev MAIL
-Set to point the user's mailbox.
+Set to the path of the user's mailbox.
 .It Ev PATH
 Set to the default
 .Ev PATH ,
 as specified when compiling
 .Nm ssh .
+.It Ev SSH_ASKPASS
+If
+.Nm
+needs a passphrase, it will read the passphrase from the current
+terminal if it was run from a terminal.
+If
+.Nm
+does not have a terminal associated with it but
+.Ev DISPLAY
+and
+.Ev SSH_ASKPASS
+are set, it will execute the program specified by
+.Ev SSH_ASKPASS
+and open an X11 window to read the passphrase.
+This is particularly useful when calling
+.Nm
+from a
+.Pa .Xsession
+or related script.
+(Note that on some machines it
+may be necessary to redirect the input from
+.Pa /dev/null
+to make this work.)
 .It Ev SSH_AUTH_SOCK
-indicates the path of a unix-domain socket used to communicate with the
+Identifies the path of a unix-domain socket used to communicate with the
 agent.
 .It Ev SSH_CLIENT
 Identifies the client end of the connection.
 The variable contains
 three space-separated values: client ip-address, client port number,
 and server port number.
+.It Ev SSH_ORIGINAL_COMMAND
+The variable contains the original command line if a forced command
+is executed.
+It can be used to extract the original arguments.
 .It Ev SSH_TTY
 This is set to the name of the tty (path to the device) associated
 with the current shell or command.
@@ -1039,13 +1310,14 @@
 .Sh FILES
 .Bl -tag -width Ds
 .It Pa $HOME/.ssh/known_hosts
-Records host keys for all hosts the user has logged into (that are not
+Records host keys for all hosts the user has logged into that are not
 in
-.Pa /etc/ssh_known_hosts ) .
+.Pa /etc/ssh_known_hosts .
 See
 .Xr sshd 8 .
-.It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa
-Contains the RSA and the DSA authentication identity of the user.
+.It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
+Contains the authentication identity of the user.
+They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
 These files
 contain sensitive data and should be readable by the user but not
 accessible by others (read/write/execute).
@@ -1055,7 +1327,7 @@
 It is possible to specify a passphrase when
 generating the key; the passphrase will be used to encrypt the
 sensitive part of this file using 3DES.
-.It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub
+.It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
 Contains the public key for authentication (public part of the
 identity file in human-readable form).
 The contents of the
@@ -1063,17 +1335,19 @@
 file should be added to
 .Pa $HOME/.ssh/authorized_keys
 on all machines
-where you wish to log in using RSA authentication.
+where the user wishes to log in using protocol version 1 RSA authentication.
 The contents of the
 .Pa $HOME/.ssh/id_dsa.pub
+and
+.Pa $HOME/.ssh/id_rsa.pub
 file should be added to
-.Pa $HOME/.ssh/authorized_keys2
+.Pa $HOME/.ssh/authorized_keys
 on all machines
-where you wish to log in using DSA authentication.
+where the user wishes to log in using protocol version 2 DSA/RSA authentication.
 These files are not
 sensitive and can (but need not) be readable by anyone.
 These files are
-never used automatically and are not necessary; they is only provided for
+never used automatically and are not necessary; they are only provided for
 the convenience of the user.
 .It Pa $HOME/.ssh/config
 This is the per-user configuration file.
@@ -1085,34 +1359,23 @@
 but the recommended permissions are read/write for the user, and not
 accessible by others.
 .It Pa $HOME/.ssh/authorized_keys
-Lists the RSA keys that can be used for logging in as this user.
+Lists the public keys (RSA/DSA) that can be used for logging in as this user.
 The format of this file is described in the
 .Xr sshd 8
 manual page.
 In the simplest form the format is the same as the .pub
-identity files (that is, each line contains the number of bits in
-modulus, public exponent, modulus, and comment fields, separated by
-spaces).
+identity files.
 This file is not highly sensitive, but the recommended
 permissions are read/write for the user, and not accessible by others.
-.It Pa $HOME/.ssh/authorized_keys2
-Lists the DSA keys that can be used for logging in as this user.
-This file is not highly sensitive, but the recommended
-permissions are read/write for the user, and not accessible by others.
-.It Pa /etc/ssh_known_hosts, /etc/ssh_known_hosts2
+.It Pa /etc/ssh_known_hosts
 Systemwide list of known host keys.
-.Pa /etc/ssh_known_hosts
-contains RSA and
-.Pa /etc/ssh_known_hosts2
-contains DSA keys.
-These files should be prepared by the
+This file should be prepared by the
 system administrator to contain the public host keys of all machines in the
 organization.
 This file should be world-readable.
 This file contains
 public keys, one per line, in the following format (fields separated
-by spaces): system name, number of bits in modulus, public exponent,
-modulus, and optional comment field.
+by spaces): system name, public key and optional comment field.
 When different names are used
 for the same machine, all such names should be listed, separated by
 commas.
@@ -1133,6 +1396,15 @@
 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.
+.It Pa /etc/ssh_host_key, /etc/ssh_host_dsa_key, /etc/ssh_host_rsa_key
+These three files contain the private parts of the host keys
+and are used for
+.Cm RhostsRSAAuthentication
+and
+.Cm HostbasedAuthentication .
+Since they are readable only by root
+.Nm
+must be setuid root if these authentication methods are desired.
 .It Pa $HOME/.rhosts
 This file is used in
 .Pa \&.rhosts
@@ -1143,7 +1415,7 @@
 Each line of the file contains a host name (in the canonical form
 returned by name servers), and then a user name on that host,
 separated by a space.
-One some machines this file may need to be
+On some machines this file may need to be
 world-readable if the user's home directory is on a NFS partition,
 because
 .Xr sshd 8
@@ -1158,9 +1430,9 @@
 .Xr sshd 8
 will be installed so that it requires successful RSA host
 authentication before permitting \s+2.\s0rhosts authentication.
-If your server machine does not have the client's host key in
+If the server machine does not have the client's host key in
 .Pa /etc/ssh_known_hosts ,
-you can store it in
+it can be stored in
 .Pa $HOME/.ssh/known_hosts .
 The easiest way to do this is to
 connect back to the client from the server machine using ssh; this
@@ -1215,49 +1487,38 @@
 Contains additional definitions for environment variables, see section
 .Sx ENVIRONMENT
 above.
-.It Pa libcrypto.so.X.1
-A version of this library which includes support for the RSA algorithm
-is required for proper operation.
 .El
-.Sh AUTHOR
-OpenSSH
-is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen,
-but with bugs removed and newer features re-added.
-Rapidly after the
-1.2.12 release, newer versions of the original ssh bore successively
-more restrictive licenses, and thus demand for a free version was born.
-.Pp
-This version of OpenSSH
-.Bl -bullet
-.It
-has all components of a restrictive nature (i.e., patents, see
-.Xr ssl 8 )
-directly removed from the source code; any licensed or patented components
-are chosen from
-external libraries.
-.It
-has been updated to support SSH protocol 1.5 and 2, making it compatible with
-all other SSH clients and servers.
-.It
-contains added support for
-.Xr kerberos 8
-authentication and ticket passing.
-.It
-supports one-time password authentication with
-.Xr skey 1 .
-.El
-.Pp
-OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl,
-Niels Provos, Theo de Raadt, and Dug Song.
-.Pp
-The support for SSH protocol 2 was written by Markus Friedl.
+.Sh DIAGNOSTICS
+.Nm
+exits with the exit status of the remote command or with 255
+if an error occurred.
+.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.
 .Sh SEE ALSO
 .Xr rlogin 1 ,
 .Xr rsh 1 ,
 .Xr scp 1 ,
+.Xr sftp 1 ,
 .Xr ssh-add 1 ,
 .Xr ssh-agent 1 ,
 .Xr ssh-keygen 1 ,
 .Xr telnet 1 ,
-.Xr sshd 8 ,
-.Xr ssl 8
+.Xr sshd 8
+.Rs
+.%A T. Ylonen
+.%A T. Kivinen
+.%A M. Saarinen
+.%A T. Rinne
+.%A S. Lehtinen
+.%T "SSH Protocol Architecture"
+.%N draft-ietf-secsh-architecture-09.txt
+.%D July 2001
+.%O work in progress material
+.Re