SYNOPSIS
ssh [-l login_name] [hostname | user@hostname] [command]
ssh [-afgknqtvxACNPTX246] [-c cipher_spec] [-e escape_char]
[-i
identity_file] [-l login_name] [-o option] [-p port] [-L
port:host:hostport] [-R port:host:hostport] [hostname |
user@hostname] [command]
DESCRIPTION
ssh (Secure Shell) 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
two untrust-
ed hosts over an insecure network. X11 connections and ar-
bitrary TCP/IP
ports can also be forwarded over the secure channel.
ssh connects and logs into the specified hostname. The user
must prove
his/her identity to the remote machine using one of several
methods de-
pending on the protocol version used:
SSH protocol version 1
First, if the machine the user logs in from is listed in
/etc/hosts.equiv
or /etc/shosts.equiv on the remote machine, and the user
names are the
same on both sides, the user is immediately permitted to log
in. Second,
if .rhosts or .shosts exists in the user's home directory on
the remote
machine and contains a line containing the name of the
client machine and
the name of the user on that machine, the user is permitted
to log in.
This form of authentication alone is normally not allowed by
the server
because it is not secure.
The second (and primary) authentication method is the rhosts
or
hosts.equiv method combined with RSA-based host authentica-
tion. It means
that if the login would be permitted by $HOME/.rhosts,
$HOME/.shosts,
/etc/hosts.equiv, or /etc/shosts.equiv, and if additionally
the server
thentication.
The scheme is based on public-key cryptography: there are
cryptosystems
where encryption and decryption are done using separate
keys, and it is
not possible to derive the decryption key from the encryp-
tion key. RSA
is one such system. The idea is that each user creates a
public/private
key pair for authentication purposes. The server knows the
public key,
and only the user knows the private key. The file
$HOME/.ssh/authorized_keys lists the public keys that are
permitted for
logging in. When the user logs in, the ssh program tells
the server
which key pair it would like to use for authentication. The
server
checks if this key is permitted, and if so, sends the user
(actually the
ssh program running on behalf of the user) a challenge, a
random number,
encrypted by the user's public key. The challenge can only
be decrypted
using the proper private key. The user's client then de-
crypts the chal-
lenge using the private key, proving that he/she knows the
private key
but without disclosing it to the server.
ssh implements the RSA authentication protocol automatical-
ly. The user
creates his/her RSA key pair by running ssh-keygen(1). This
stores the
private key in $HOME/.ssh/identity and the public key in
$HOME/.ssh/identity.pub in the user's home directory. The
user should
then copy the identity.pub to $HOME/.ssh/authorized_keys in
his/her home
directory on the remote machine (the authorized_keys file
corresponds to
the conventional $HOME/.rhosts file, and has one key per
line, though the
lines can be very long). After this, the user can log in
without giving
the password. RSA authentication is much more secure than
rhosts authen-
tication.
The most convenient way to use RSA authentication may be
with an authen-
tion methods are available: At first, the client attempts to
authenticate
using the public key method. If this method fails password
authentica-
tion is tried.
The public key method is similar to RSA authentication de-
scribed in the
previous section except that the DSA algorithm is used in-
stead of the
patented RSA algorithm. The client uses his private DSA key
$HOME/.ssh/id_dsa to sign the session identifier and sends
the result to
the server. The server checks whether the matching public
key is listed
in $HOME/.ssh/authorized_keys2 and grants access if both the
key is found
and the signature is correct. The session identifier is de-
rived from a
shared Diffie-Hellman value and is only known to the client
and the serv-
er.
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 authen-
tication.
Protocol 2 provides additional mechanisms for confidentiali-
ty (the traf-
fic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
and integrity
(hmac-sha1, hmac-md5). Note that protocol 1 lacks a strong
mechanism for
ensuring the integrity of the connection.
Login session and remote execution
When the user's identity has been accepted by the server,
the server ei-
ther executes the given command, or logs into the machine
and gives the
user a normal shell on the remote machine. All communica-
tion with the
remote command or shell will be automatically encrypted.
If a pseudo-terminal has been allocated (normal login ses-
sion), the user
can disconnect with ~., and suspend ssh with ~^Z. All for-
character must
always follow a newline to be interpreted as special. The
escape charac-
ter can be changed in configuration files or on the command
line.
If no pseudo tty has been allocated, the session is trans-
parent and can
be used to reliably transfer binary data. On most systems,
setting the
escape character to ``none'' will also make the session
transparent even
if a tty is used.
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 exit
status of the remote program is returned as the exit status
of ssh.
X11 and TCP forwarding
If the user is using X11 (the 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 programs started from the
shell (or com-
mand) will go through the encrypted channel, and the connec-
tion to the
real X server will be made from the local machine. The user
should not
manually set DISPLAY. Forwarding of X11 connections can be
configured on
the command line or in configuration files.
The DISPLAY value set by ssh will point to the server ma-
chine, but with a
display number greater than zero. This is normal, and hap-
pens because
ssh creates a ``proxy'' X server on the server machine for
forwarding the
connections over the encrypted channel.
ssh will also automatically set up Xauthority data on the
server machine.
For this purpose, it will generate a random authorization
cookie, store
it in Xauthority on the server, and verify that any forward-
ed connections
specified either on command line or in a configuration file.
One possi-
ble application of TCP/IP forwarding is a secure connection
to an elec-
tronic purse; another is going trough firewalls.
Server authentication
ssh automatically maintains and checks a database containing
identifica-
tions for all hosts it has ever been used with. RSA host
keys are stored
in $HOME/.ssh/known_hosts and DSA host keys are stored in
$HOME/.ssh/known_hosts2 in the user's home directory. Addi-
tionally, the
files /etc/ssh_known_hosts and /etc/ssh_known_hosts2 are au-
tomatically
checked for known hosts. Any new hosts are automatically
added to the
user's file. If a host's identification ever changes, ssh
warns about
this and disables password authentication to prevent a tro-
jan horse from
getting the user's password. Another purpose of this mecha-
nism is to
prevent man-in-the-middle attacks which could otherwise be
used to cir-
cumvent the encryption. The StrictHostKeyChecking option
(see below) can
be used to prevent logins to machines whose host key is not
known or has
changed.
OPTIONS
-a Disables forwarding of the authentication agent con-
nection.
-A Enables forwarding of the authentication agent con-
nection. This
can also be specified on a per-host basis in a con-
figuration
file.
-c blowfish|3des
Selects the cipher to use for encrypting the ses-
sion. 3des is
used by default. It is believed to be secure. 3des
(triple-des)
is an encrypt-decrypt-encrypt triple with three dif-
ferent keys.
It is presumably more secure than the des cipher
which is no
Sets the escape character for sessions with a pty
(default: `~').
The escape character is only recognized at the be-
ginning of a
line. The escape character followed by a dot (`.')
closes the
connection, followed by control-Z suspends the con-
nection, and
followed by itself sends the escape character once.
Setting the
character to ``none'' disables any escapes and makes
the session
fully transparent.
-f Requests ssh to go to background just before command
execution.
This is useful if ssh is going to ask for passwords
or passphras-
es, but the user wants it in the background. This
implies -n.
The recommended way to start X11 programs at a re-
mote site is
with something like ssh -f host xterm.
-g Allows remote hosts to connect to local forwarded
ports.
-i identity_file
Selects the file from which the identity (private
key) for RSA
authentication is read. Default is $HOME/.ssh/iden-
tity in the
user's home directory. Identity files may also be
specified on a
per-host basis in the configuration file. It is
possible to have
multiple -i options (and multiple identities speci-
fied in config-
uration files).
-k Disables forwarding of Kerberos tickets and AFS to-
kens. This may
also be specified on a per-host basis in the config-
uration file.
-l login_name
Specifies the user to log in as on the remote ma-
chine. This also
may be specified on a per-host basis in the configu-
ration file.
-n Redirects stdin from /dev/null (actually, prevents
option.)
-N Do not execute a remote command. This is usefull if
you just
want to forward ports (protocol version 2 only).
-o option
Can be used to give options in the format used in
the config
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.
-p port
Port to connect to on the remote host. This can be
specified on
a per-host basis in the configuration file.
-P Use a non-privileged port for outgoing connections.
This can be
used if your firewall does not permit connections
from privileged
ports. Note that this option turns off Rhost-
sAuthentication and
RhostsRSAAuthentication.
-q Quiet mode. Causes all warning and diagnostic mes-
sages to be
suppressed. Only fatal errors are displayed.
-t Force pseudo-tty allocation. This can be used to
execute arbi-
trary screen-based programs on a remote machine,
which can be
very useful, e.g., when implementing menu services.
-T Disable pseudo-tty allocation (protocol version 2
only).
-v Verbose mode. Causes ssh to print debugging mes-
sages about its
progress. This is helpful in debugging connection,
authentica-
tion, and configuration problems. The verbose mode
is also used
to display skey(1) challenges, if the user entered
"s/key" as
password. Multiple -v options increases the ver-
and the
``level'' can be controlled by the CompressionLevel
option (see
below). Compression is desirable on modem lines and
other 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 con-
figuration files; see the Compress option below.
-L 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. This
works by allocating a socket to listen to port on
the local side,
and whenever a connection is made to this port, the
connection is
forwarded over the secure channel, and a connection
is made to
host port hostport from the remote machine. Port
forwardings can
also be specified in the configuration file. Only
root can for-
ward privileged ports. IPv6 addresses can be speci-
fied with an
alternative syntax: port/host/hostport
-R port:host:hostport
Specifies that the given port on the remote (server)
host is to
be forwarded to the given host and port on the local
side. This
works by allocating a socket to listen to port on
the remote
side, and whenever a connection is made to this
port, the connec-
tion is forwarded over the secure channel, and a
connection is
made to host port hostport from the local machine.
Port forward-
ings can also be specified in the configuration
file. Privileged
ports can be forwarded only when logging in as root
on the remote
machine.
-2 Forces ssh to try protocol version 2 only.
-4 Forces ssh to use IPv4 addresses only.
of the patterns given in the specification. The matched
host name is the
one given on the command line.
Since the first obtained value for each parameter is used,
more host-spe-
cific declarations should be given near the beginning of the
file, and
general defaults at the end.
The configuration file has the following format:
Empty lines and lines starting with `#' are comments.
Otherwise a line is of the format ``keyword arguments''. The
possible
keywords and their meanings are as follows (note that the
configuration
files are case-sensitive):
Host Restricts the following declarations (up to the next
Host key-
word) to be only for those hosts that match one of
the patterns
given after the keyword. `*' and `?' can be used as
wildcards in
the patterns. A single `*' as a pattern can be used
to provide
global defaults for all hosts. The host is the
hostname argument
given on the command line (i.e., the name is not
converted to a
canonicalized host name before matching).
AFSTokenPassing
Specifies whether to pass AFS tokens to remote host.
The argu-
ment to this keyword must be ``yes'' or ``no''.
BatchMode
If set to ``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. The argument
must be
``yes'' or ``no''.
CheckHostIP
If this flag is set to ``yes'', ssh will additional-
ly check the
host ip address in the known_hosts file. This al-
preference. Multiple ciphers must be comma-separat-
ed. The de-
fault is ``3des-cbc,blowfish-cbc,cast128-cbc,arc-
four''.
Compression
Specifies whether to use compression. The argument
must be
``yes'' or ``no''.
CompressionLevel
Specifies the compression level to use if compres-
sion is enable.
The argument must be an integer from 1 (fast) to 9
(slow, best).
The default level is 6, which is good for most ap-
plications. The
meaning of the values is the same as in gzip(1).
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.
DSAAuthentication
Specifies whether to try DSA authentication. The
argument to
this keyword must be ``yes'' or ``no''. DSA authen-
tication will
only be attempted if a DSA identity file exists.
Note that this
option applies to protocol version 2 only.
EscapeChar
Sets the escape character (default: `~'). The escape
character
can also be set on the command line. The argument
should be a
single character, `^' followed by a letter, or
``none'' to dis-
able the escape character entirely (making the con-
nection trans-
parent for binary data).
FallBackToRsh
Specifies that if connecting via ssh fails due to a
connection
refused error (there is no sshd(8) listening on the
remote host),
Specifies whether X11 connections will be automati-
cally redirect-
ed over the secure channel and DISPLAY set. The ar-
gument must be
``yes'' or ``no''. The default is ``no''.
GatewayPorts
Specifies whether remote hosts are allowed to con-
nect to local
forwarded ports. The argument must be ``yes'' or
``no''. The de-
fault is ``no''.
GlobalKnownHostsFile
Specifies a file to use instead of
/etc/ssh_known_hosts.
HostName
Specifies the real host name to log into. This can
be used to
specify nicknames or abbreviations for hosts. De-
fault is the
name given on the command line. Numeric IP address-
es are also
permitted (both on the command line and in HostName
specifica-
tions).
IdentityFile
Specifies the file from which the user's RSA authen-
tication iden-
tity is read (default $HOME/.ssh/identity in the us-
er's home di-
rectory). Additionally, any identities represented
by the au-
thentication agent will be used for authentication.
The file
name may use the tilde syntax to refer to a user's
home directo-
ry. It is possible to have multiple identity files
specified in
configuration files; all these identities will be
tried in se-
quence.
IdentityFile2
Specifies the file from which the user's DSA authen-
tication iden-
tity is read (default $HOME/.ssh/id_dsa in the us-
er's home direc-
tory). The file name may use the tilde syntax to
refer to a us-
ticed. However,
this means that connections will die if the route is
down tem-
porarily, and some people find it annoying.
The default is ``yes'' (to send keepalives), 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.
To disable keepalives, the value should be set to
``no'' in both
the server and the client configuration files.
KerberosAuthentication
Specifies whether Kerberos authentication will be
used. The ar-
gument to this keyword must be ``yes'' or ``no''.
KerberosTgtPassing
Specifies whether a Kerberos TGT will be forwarded
to the server.
This will only work if the Kerberos server is actu-
ally an AFS
kaserver. The argument to this keyword must be
``yes'' or
``no''.
LocalForward
Specifies that a TCP/IP port on the local machine be
forwarded
over the secure channel to given host:port from the
remote ma-
chine. The first argument must be a port number,
and the second
must be host:port. Multiple forwardings may be
specified, and
additional forwardings can be given on the command
line. Only
the superuser can forward privileged ports.
LogLevel
Gives the verbosity level that is used when logging
messages from
ssh. The possible values are: QUIET, FATAL, ERROR,
INFO, VERBOSE
and DEBUG. The default is INFO.
NumberOfPasswordPrompts
Specifies the number of password prompts before giv-
ing up. The
Protocol
Specifies the protocol versions ssh should support
in order of
preference. The possible values are ``1'' and
``2''. Multiple
versions must be comma-separated. The default is
``1,2''. This
means that ssh tries version 1 and falls back to
version 2 if
version 1 is not available.
ProxyCommand
Specifies the command to use to connect to the serv-
er. The com-
mand string extends to the end of the line, and is
executed with
/bin/sh. In the command string, `%h' will be substi-
tuted by the
host name to connect and `%p' by the port. The com-
mand can be
basically anything, and should read from its stan-
dard input and
write to its standard output. It should eventually
connect an
sshd(8) server running on some machine, or execute
sshd -i some-
where. Host key management will be done using the
HostName of
the host being connected (defaulting to the name
typed by the us-
er). Note that CheckHostIP is not available for
connects with a
proxy command.
RemoteForward
Specifies that a TCP/IP port on the remote machine
be forwarded
over the secure channel to given host:port from the
local ma-
chine. The first argument must be a port number,
and the second
must be host:port. Multiple forwardings may be
specified, and
additional forwardings can be given on the command
line. Only
the superuser can forward privileged ports.
RhostsAuthentication
Specifies whether to try rhosts based authentica-
tion. Note that
this declaration only affects the client side and
has no effect
host authentication. This is the primary authenti-
cation method
for most sites. The argument must be ``yes'' or
``no''.
RSAAuthentication
Specifies whether to try RSA authentication. The
argument to
this keyword must be ``yes'' or ``no''. RSA authen-
tication will
only be attempted if the identity file exists, or an
authentica-
tion agent is running. Note that this option ap-
plies to protocol
version 1 only.
SkeyAuthentication
Specifies whether to use skey(1) authentication.
The argument to
this keyword must be ``yes'' or ``no''. The default
is ``no''.
StrictHostKeyChecking
If this flag is set to ``yes'', ssh ssh will never
automatically
add host keys to the $HOME/.ssh/known_hosts and
$HOME/.ssh/known_hosts2 files, and refuses to con-
nect hosts whose
host key has changed. This provides maximum protec-
tion against
trojan horse attacks. However, it can be somewhat
annoying if
you don't have good /etc/ssh_known_hosts and
/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. The
host keys of
known hosts will be verified automatically in either
case. The
argument must be ``yes'' or ``no''.
UsePrivilegedPort
Specifies whether to use a privileged port for out-
going connec-
tions. The argument must be ``yes'' or ``no''. The
default is
``yes''. Note that setting this option to ``no''
turns off
$HOME/.ssh/known_hosts.
UseRsh Specifies that rlogin/rsh should be used for this
host. It is
possible that the host does not at all support the
ssh protocol.
This causes ssh to immediately execute rsh(1). All
other options
(except HostName) are ignored if this has been spec-
ified. The
argument must be ``yes'' or ``no''.
XAuthLocation
Specifies the location of the xauth(1) program. The
default is
/usr/X11R6/bin/xauth.
ENVIRONMENT
ssh will normally set the following environment variables:
DISPLAY
The DISPLAY variable indicates the location of the
X11 server.
It is automatically set by ssh to point to a value
of the form
``hostname:n'' where hostname indicates the host
where the shell
runs, and n is an integer >= 1. ssh uses this spe-
cial value to
forward X11 connections over the secure channel.
The user should
normally not set DISPLAY explicitly, as that will
render the X11
connection insecure (and will require the user to
manually copy
any required authorization cookies).
HOME Set to the path of the user's home directory.
LOGNAME
Synonym for USER; set for compatibility with systems
that use
this variable.
MAIL Set to point the user's mailbox.
PATH Set to the default PATH, as specified when compiling
ssh.
SSH_AUTH_SOCK
indicates the path of a unix-domain socket used to
communicate
no tty, this variable is not set.
TZ The timezone variable is set to indicate the present
timezone if
it was set when the daemon was started (i.e., the
daemon passes
the value on to new connections).
USER Set to the name of the user logging in.
Additionally, ssh reads $HOME/.ssh/environment, and adds
lines of the
format ``VARNAME=value'' to the environment.
FILES
$HOME/.ssh/known_hosts
Records host keys for all hosts the user has logged
into (that
are not in /etc/ssh_known_hosts). See sshd(8).
$HOME/.ssh/identity, $HOME/.ssh/id_dsa
Contains the RSA and the DSA authentication identity
of the user.
These files contain sensitive data and should be
readable by the
user but not accessible by others (read/write/exe-
cute). Note
that ssh ignores a private key file if it is acces-
sible by oth-
ers. It is possible to specify a passphrase when
generating the
key; the passphrase will be used to encrypt the sen-
sitive part of
this file using 3DES.
$HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub
Contains the public key for authentication (public
part of the
identity file in human-readable form). The contents
of the
$HOME/.ssh/identity.pub file should be added to
$HOME/.ssh/authorized_keys on all machines where you
wish to log
in using RSA authentication. The contents of the
$HOME/.ssh/id_dsa.pub file should be added to
$HOME/.ssh/authorized_keys2 on all machines where
you wish to log
in using DSA 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
$HOME/.ssh/authorized_keys
Lists the RSA keys that can be used for logging in
as this user.
The format of this file is described in the 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, sepa-
rated by
spaces). This file is not highly sensitive, but the
recommended
permissions are read/write for the user, and not ac-
cessible by
others.
$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 recom-
mended permis-
sions are read/write for the user, and not accessi-
ble by others.
/etc/ssh_known_hosts, /etc/ssh_known_hosts2
Systemwide list of known host keys.
/etc/ssh_known_hosts con-
tains RSA and /etc/ssh_known_hosts2 contains DSA
keys. These
files should be prepared by the system administrator
to contain
the public host keys of all machines in the organi-
zation. This
file should be world-readable. This file contains
public keys,
one per line, in the following format (fields sepa-
rated by
spaces): system name, number of bits in modulus,
public exponent,
modulus, and optional comment field. When different
names are
used for the same machine, all such names should be
listed, sepa-
rated by commas. The format is described on the
sshd(8) manual
page.
The canonical system name (as returned by name
servers) is used
by sshd(8) to verify the client host when logging
in; other names
ration file.
This file must be world-readable.
$HOME/.rhosts
This file is used in .rhosts authentication to list
the host/user
pairs that are permitted to log in. (Note that this
file is also
used by rlogin and rsh, which makes using this file
insecure.)
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
world-readable if the user's home directory is on a
NFS parti-
tion, because sshd(8) reads it as root. Additional-
ly, this file
must be owned by the user, and must not have write
permissions
for anyone else. The recommended permission for
most machines is
read/write for the user, and not accessible by oth-
ers.
Note that by default sshd(8) will be installed so
that it re-
quires successful RSA host authentication before
permitting
.rhosts authentication. If your server machine does
not have the
client's host key in /etc/ssh_known_hosts, you can
store it in
$HOME/.ssh/known_hosts. The easiest way to do this
is to connect
back to the client from the server machine using
ssh; this will
automatically add the host key to
$HOME/.ssh/known_hosts.
$HOME/.shosts
This file is used exactly the same way as .rhosts.
The purpose
for having this file is to be able to use rhosts au-
thentication
with ssh without permitting login with rlogin(1) or
rsh(1).
/etc/hosts.equiv
/etc/shosts.equiv
This file is processed exactly as /etc/hosts.equiv.
This file may
be useful to permit logins using ssh but not using
rsh/rlogin.
/etc/sshrc
Commands in this file are executed by ssh when the
user logs in
just before the user's shell (or command) is start-
ed. See the
sshd(8) manual page for more information.
$HOME/.ssh/rc
Commands in this file are executed by ssh when the
user logs in
just before the user's shell (or command) is start-
ed. See the
sshd(8) manual page for more information.
$HOME/.ssh/environment
Contains additional definitions for environment
variables, see
section ENVIRONMENT above.
libcrypto.so.X.1
A version of this library which includes support for
the RSA al-
gorithm is required for proper operation.
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 ver-
sion was born.
This version of OpenSSH
o has all components of a restrictive nature (i.e.,
patents, see
crypto(3)) directly removed from the source code; any
licensed or
patented components are chosen from external libraries.
o has been updated to support SSH protocol 1.5 and 2, mak-
ing it compat-
SEE ALSO
rlogin(1), rsh(1), scp(1), ssh-add(1), ssh-agent(1),
ssh-keygen(1),
telnet(1), sshd(8), crypto(3)
BSD Experimental September 25, 1999
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