890 lines
47 KiB
Plaintext
890 lines
47 KiB
Plaintext
SSH_CONFIG(5) OpenBSD Programmer's Manual SSH_CONFIG(5)
|
|
|
|
NAME
|
|
ssh_config - OpenSSH SSH client configuration files
|
|
|
|
SYNOPSIS
|
|
~/.ssh/config
|
|
/etc/ssh/ssh_config
|
|
|
|
DESCRIPTION
|
|
ssh(1) obtains configuration data from the following sources in the
|
|
following order:
|
|
|
|
1. command-line options
|
|
2. user's configuration file (~/.ssh/config)
|
|
3. system-wide configuration file (/etc/ssh/ssh_config)
|
|
|
|
For each parameter, the first obtained value will be used. The
|
|
configuration files contain sections separated by ``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.
|
|
|
|
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.
|
|
|
|
The configuration file has the following format:
|
|
|
|
Empty lines and lines starting with `#' are comments. Otherwise a line
|
|
is of the format ``keyword arguments''. Configuration options may be
|
|
separated by whitespace or optional whitespace and exactly one `='; the
|
|
latter format is useful to avoid the need to quote whitespace when
|
|
specifying configuration options using the ssh, scp, and sftp -o option.
|
|
Arguments may optionally be enclosed in double quotes (") in order to
|
|
represent arguments containing spaces.
|
|
|
|
The possible keywords and their meanings are as follows (note that
|
|
keywords are case-insensitive and arguments are case-sensitive):
|
|
|
|
Host Restricts the following declarations (up to the next Host or
|
|
Match keyword) to be only for those hosts that match one of the
|
|
patterns given after the keyword. If more than one pattern is
|
|
provided, they should be separated by whitespace. 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).
|
|
|
|
A pattern entry may be negated by prefixing it with an
|
|
exclamation mark (`!'). If a negated entry is matched, then the
|
|
Host entry is ignored, regardless of whether any other patterns
|
|
on the line match. Negated matches are therefore useful to
|
|
provide exceptions for wildcard matches.
|
|
|
|
See PATTERNS for more information on patterns.
|
|
|
|
Match Restricts the following declarations (up to the next Host or
|
|
Match keyword) to be used only when the conditions following the
|
|
Match keyword are satisfied. Match conditions are specified
|
|
using one or more keyword/criteria pairs or the single token all
|
|
which matches all criteria. The available keywords are: exec,
|
|
host, originalhost, user, and localuser.
|
|
|
|
The exec keyword executes the specified command under the user's
|
|
shell. If the command returns a zero exit status then the
|
|
condition is considered true. Commands containing whitespace
|
|
characters must be quoted. The following character sequences in
|
|
the command will be expanded prior to execution: `%L' will be
|
|
substituted by the first component of the local host name, `%l'
|
|
will be substituted by the local host name (including any domain
|
|
name), `%h' will be substituted by the target host name, `%n'
|
|
will be substituted by the original target host name specified on
|
|
the command-line, `%p' the destination port, `%r' by the remote
|
|
login username, and `%u' by the username of the user running
|
|
ssh(1).
|
|
|
|
The other keywords' criteria must be single entries or comma-
|
|
separated lists and may use the wildcard and negation operators
|
|
described in the PATTERNS section. The criteria for the host
|
|
keyword are matched against the target hostname, after any
|
|
substitution by the Hostname option. The originalhost keyword
|
|
matches against the hostname as it was specified on the command-
|
|
line. The user keyword matches against the target username on
|
|
the remote host. The localuser keyword matches against the name
|
|
of the local user running ssh(1) (this keyword may be useful in
|
|
system-wide ssh_config files).
|
|
|
|
AddressFamily
|
|
Specifies which address family to use when connecting. Valid
|
|
arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6''
|
|
(use IPv6 only).
|
|
|
|
BatchMode
|
|
If set to ``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
|
|
``yes'' or ``no''. The default is ``no''.
|
|
|
|
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
|
|
UsePrivilegedPort is set to ``yes''.
|
|
|
|
CanonicalDomains
|
|
When CanonicalizeHostname is enabled, this option specifies the
|
|
list of domain suffixes in which to search for the specified
|
|
destination host.
|
|
|
|
CanonicalizeFallbackLocal
|
|
Specifies whether to fail with an error when hostname
|
|
canonicalization fails. The default, ``yes'', will attempt to
|
|
look up the unqualified hostname using the system resolver's
|
|
search rules. A value of ``no'' will cause ssh(1) to fail
|
|
instantly if CanonicalizeHostname is enabled and the target
|
|
hostname cannot be found in any of the domains specified by
|
|
CanonicalDomains.
|
|
|
|
CanonicalizeHostname
|
|
Controls whether explicit hostname canonicalization is performed.
|
|
The default, ``no'', is not to perform any name rewriting and let
|
|
the system resolver handle all hostname lookups. If set to
|
|
``yes'' then, for connections that do not use a ProxyCommand,
|
|
ssh(1) will attempt to canonicalize the hostname specified on the
|
|
command line using the CanonicalDomains suffixes and
|
|
CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is
|
|
set to ``always'', then canonicalization is applied to proxied
|
|
connections too.
|
|
|
|
If this option is enabled and canonicalisation results in the
|
|
target hostname changing, then the configuration files are
|
|
processed again using the new target name to pick up any new
|
|
configuration in matching Host stanzas.
|
|
|
|
CanonicalizeMaxDots
|
|
Specifies the maximum number of dot characters in a hostname
|
|
before canonicalization is disabled. The default, ``1'', allows
|
|
a single dot (i.e. hostname.subdomain).
|
|
|
|
CanonicalizePermittedCNAMEs
|
|
Specifies rules to determine whether CNAMEs should be followed
|
|
when canonicalizing hostnames. The rules consist of one or more
|
|
arguments of source_domain_list:target_domain_list, where
|
|
source_domain_list is a pattern-list of domains that may follow
|
|
CNAMEs in canonicalization, and target_domain_list is a pattern-
|
|
list of domains that they may resolve to.
|
|
|
|
For example, ``*.a.example.com:*.b.example.com,*.c.example.com''
|
|
will allow hostnames matching ``*.a.example.com'' to be
|
|
canonicalized to names in the ``*.b.example.com'' or
|
|
``*.c.example.com'' domains.
|
|
|
|
ChallengeResponseAuthentication
|
|
Specifies whether to use challenge-response authentication. The
|
|
argument to this keyword must be ``yes'' or ``no''. The default
|
|
is ``yes''.
|
|
|
|
CheckHostIP
|
|
If this flag is set to ``yes'', ssh(1) will additionally check
|
|
the host IP address in the known_hosts file. This allows ssh to
|
|
detect if a host key changed due to DNS spoofing. If the option
|
|
is set to ``no'', the check will not be executed. The default is
|
|
``yes''.
|
|
|
|
Cipher Specifies the cipher to use for encrypting the session in
|
|
protocol version 1. Currently, ``blowfish'', ``3des'', and
|
|
``des'' are supported. des is only supported in the ssh(1)
|
|
client for interoperability with legacy protocol 1
|
|
implementations that do not support the 3des cipher. Its use is
|
|
strongly discouraged due to cryptographic weaknesses. The
|
|
default is ``3des''.
|
|
|
|
Ciphers
|
|
Specifies the ciphers allowed for protocol version 2 in order of
|
|
preference. Multiple ciphers must be comma-separated. The
|
|
supported ciphers are:
|
|
|
|
``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'', ``aes256-cbc'',
|
|
``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'',
|
|
``aes128-gcm@openssh.com'', ``aes256-gcm@openssh.com'',
|
|
``arcfour128'', ``arcfour256'', ``arcfour'', ``blowfish-cbc'',
|
|
``cast128-cbc'', and ``chacha20-poly1305@openssh.com''.
|
|
|
|
The default is:
|
|
|
|
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
|
|
aes128-gcm@openssh.com,aes256-gcm@openssh.com,
|
|
chacha20-poly1305@openssh.com,
|
|
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
|
|
aes256-cbc,arcfour
|
|
|
|
The list of available ciphers may also be obtained using the -Q
|
|
option of ssh(1).
|
|
|
|
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
|
|
ssh(1) command line to clear port forwardings set in
|
|
configuration files, and is automatically set by scp(1) and
|
|
sftp(1). The argument must be ``yes'' or ``no''. The default is
|
|
``no''.
|
|
|
|
Compression
|
|
Specifies whether to use compression. The argument must be
|
|
``yes'' or ``no''. The default is ``no''.
|
|
|
|
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 gzip(1). Note that this
|
|
option applies to protocol version 1 only.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
ControlMaster
|
|
Enables the sharing of multiple sessions over a single network
|
|
connection. When set to ``yes'', ssh(1) will listen for
|
|
connections on a control socket specified using the ControlPath
|
|
argument. Additional sessions can connect to this socket using
|
|
the same ControlPath with ControlMaster set to ``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.
|
|
|
|
Setting this to ``ask'' will cause ssh to listen for control
|
|
connections, but require confirmation using the SSH_ASKPASS
|
|
program before they are accepted (see ssh-add(1) for details).
|
|
If the ControlPath cannot be opened, ssh will continue without
|
|
connecting to a master instance.
|
|
|
|
X11 and 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.
|
|
|
|
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: ``auto'' and
|
|
``autoask''. The latter requires confirmation like the ``ask''
|
|
option.
|
|
|
|
ControlPath
|
|
Specify the path to the control socket used for connection
|
|
sharing as described in the ControlMaster section above or the
|
|
string ``none'' to disable connection sharing. In the path, `%L'
|
|
will be substituted by the first component of the local host
|
|
name, `%l' will be substituted by the local host name (including
|
|
any domain name), `%h' will be substituted by the target host
|
|
name, `%n' will be substituted by the original target host name
|
|
specified on the command line, `%p' the destination port, `%r' by
|
|
the remote login username, and `%u' by the username of the user
|
|
running ssh(1). It is recommended that any ControlPath used for
|
|
opportunistic connection sharing include at least %h, %p, and %r.
|
|
This ensures that shared connections are uniquely identified.
|
|
|
|
ControlPersist
|
|
When used in conjunction with ControlMaster, specifies that the
|
|
master connection should remain open in the background (waiting
|
|
for future client connections) after the initial client
|
|
connection has been closed. If set to ``no'', then the master
|
|
connection will not be placed into the background, and will close
|
|
as soon as the initial client connection is closed. If set to
|
|
``yes'', then the master connection will remain in the background
|
|
indefinitely (until killed or closed via a mechanism such as the
|
|
ssh(1) ``-O exit'' option). If set to a time in seconds, or a
|
|
time in any of the formats documented in sshd_config(5), then the
|
|
backgrounded master connection will automatically terminate after
|
|
it has remained idle (with no client connections) for the
|
|
specified time.
|
|
|
|
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.
|
|
|
|
The argument must be [bind_address:]port. IPv6 addresses can be
|
|
specified by enclosing addresses in square brackets. By default,
|
|
the local port is bound in accordance with the GatewayPorts
|
|
setting. However, an explicit bind_address may be used to bind
|
|
the connection to a specific address. The bind_address of
|
|
``localhost'' indicates that the listening port be bound for
|
|
local use only, while an empty address or `*' indicates that the
|
|
port should be available from all interfaces.
|
|
|
|
Currently the SOCKS4 and SOCKS5 protocols are supported, and
|
|
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.
|
|
|
|
EnableSSHKeysign
|
|
Setting this option to ``yes'' in the global client configuration
|
|
file /etc/ssh/ssh_config enables the use of the helper program
|
|
ssh-keysign(8) during HostbasedAuthentication. The argument must
|
|
be ``yes'' or ``no''. The default is ``no''. This option should
|
|
be placed in the non-hostspecific section. See ssh-keysign(8)
|
|
for more information.
|
|
|
|
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
|
|
disable the escape character entirely (making the connection
|
|
transparent for binary data).
|
|
|
|
ExitOnForwardFailure
|
|
Specifies whether ssh(1) should terminate the connection if it
|
|
cannot set up all requested dynamic, tunnel, local, and remote
|
|
port forwardings. The argument must be ``yes'' or ``no''. The
|
|
default is ``no''.
|
|
|
|
ForwardAgent
|
|
Specifies whether the connection to the authentication agent (if
|
|
any) will be forwarded to the remote machine. The argument must
|
|
be ``yes'' or ``no''. The default is ``no''.
|
|
|
|
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.
|
|
|
|
ForwardX11
|
|
Specifies whether X11 connections will be automatically
|
|
redirected over the secure channel and DISPLAY set. The argument
|
|
must be ``yes'' or ``no''. The default is ``no''.
|
|
|
|
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
|
|
ForwardX11Trusted option is also enabled.
|
|
|
|
ForwardX11Timeout
|
|
Specify a timeout for untrusted X11 forwarding using the format
|
|
described in the TIME FORMATS section of sshd_config(5). X11
|
|
connections received by ssh(1) after this time will be refused.
|
|
The default is to disable untrusted X11 forwarding after twenty
|
|
minutes has elapsed.
|
|
|
|
ForwardX11Trusted
|
|
If this option is set to ``yes'', remote X11 clients will have
|
|
full access to the original X11 display.
|
|
|
|
If this option is set to ``no'', remote X11 clients will be
|
|
considered untrusted and prevented from stealing or tampering
|
|
with data belonging to trusted X11 clients. Furthermore, the
|
|
xauth(1) token used for the session will be set to expire after
|
|
20 minutes. Remote clients will be refused access after this
|
|
time.
|
|
|
|
The default is ``no''.
|
|
|
|
See the X11 SECURITY extension specification for full details on
|
|
the restrictions imposed on untrusted clients.
|
|
|
|
GatewayPorts
|
|
Specifies whether remote hosts are allowed to connect to local
|
|
forwarded ports. By default, ssh(1) binds local port forwardings
|
|
to the loopback address. This prevents other remote hosts from
|
|
connecting to forwarded ports. 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 ``yes'' or ``no''. The
|
|
default is ``no''.
|
|
|
|
GlobalKnownHostsFile
|
|
Specifies one or more files to use for the global host key
|
|
database, separated by whitespace. The default is
|
|
/etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2.
|
|
|
|
GSSAPIAuthentication
|
|
Specifies whether user authentication based on GSSAPI is allowed.
|
|
The default is ``no''. Note that this option applies to protocol
|
|
version 2 only.
|
|
|
|
GSSAPIDelegateCredentials
|
|
Forward (delegate) credentials to the server. The default is
|
|
``no''. Note that this option applies to protocol version 2
|
|
only.
|
|
|
|
HashKnownHosts
|
|
Indicates that ssh(1) should hash host names and addresses when
|
|
they are added to ~/.ssh/known_hosts. These hashed names may be
|
|
used normally by ssh(1) and sshd(8), but they do not reveal
|
|
identifying information should the file's contents be disclosed.
|
|
The default is ``no''. Note that existing names and addresses in
|
|
known hosts files will not be converted automatically, but may be
|
|
manually hashed using ssh-keygen(1).
|
|
|
|
HostbasedAuthentication
|
|
Specifies whether to try rhosts based authentication with public
|
|
key authentication. The argument must be ``yes'' or ``no''. The
|
|
default is ``no''. This option applies to protocol version 2
|
|
only and is similar to RhostsRSAAuthentication.
|
|
|
|
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:
|
|
|
|
ecdsa-sha2-nistp256-cert-v01@openssh.com,
|
|
ecdsa-sha2-nistp384-cert-v01@openssh.com,
|
|
ecdsa-sha2-nistp521-cert-v01@openssh.com,
|
|
ssh-ed25519-cert-v01@openssh.com,
|
|
ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,
|
|
ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,
|
|
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
|
|
ssh-ed25519,ssh-rsa,ssh-dss
|
|
|
|
If hostkeys are known for the destination host then this default
|
|
is modified to prefer their algorithms.
|
|
|
|
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.
|
|
|
|
HostName
|
|
Specifies the real host name to log into. This can be used to
|
|
specify nicknames or abbreviations for hosts. If the hostname
|
|
contains the character sequence `%h', then this will be replaced
|
|
with the host name specified on the command line (this is useful
|
|
for manipulating unqualified names). The default is the name
|
|
given on the command line. Numeric IP addresses are also
|
|
permitted (both on the command line and in HostName
|
|
specifications).
|
|
|
|
IdentitiesOnly
|
|
Specifies that ssh(1) should only use the authentication identity
|
|
files configured in the ssh_config files, even if ssh-agent(1) or
|
|
a PKCS11Provider offers more identities. The argument to this
|
|
keyword must be ``yes'' or ``no''. This option is intended for
|
|
situations where ssh-agent offers many different identities. The
|
|
default is ``no''.
|
|
|
|
IdentityFile
|
|
Specifies a file from which the user's DSA, ECDSA, ED25519 or RSA
|
|
authentication identity is read. The default is ~/.ssh/identity
|
|
for protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa,
|
|
~/.ssh/id_ed25519 and ~/.ssh/id_rsa for protocol version 2.
|
|
Additionally, any identities represented by the authentication
|
|
agent will be used for authentication unless IdentitiesOnly is
|
|
set. ssh(1) will try to load certificate information from the
|
|
filename obtained by appending -cert.pub to the path of a
|
|
specified IdentityFile.
|
|
|
|
The file name may use the tilde syntax to refer to a user's home
|
|
directory or one of the following escape characters: `%d' (local
|
|
user's home directory), `%u' (local user name), `%l' (local host
|
|
name), `%h' (remote host name) or `%r' (remote user name).
|
|
|
|
It is possible to have multiple identity files specified in
|
|
configuration files; all these identities will be tried in
|
|
sequence. Multiple IdentityFile directives will add to the list
|
|
of identities tried (this behaviour differs from that of other
|
|
configuration directives).
|
|
|
|
IdentityFile may be used in conjunction with IdentitiesOnly to
|
|
select which identities in an agent are offered during
|
|
authentication.
|
|
|
|
IgnoreUnknown
|
|
Specifies a pattern-list of unknown options to be ignored if they
|
|
are encountered in configuration parsing. This may be used to
|
|
suppress errors if ssh_config contains options that are
|
|
unrecognised by ssh(1). It is recommended that IgnoreUnknown be
|
|
listed early in the configuration file as it will not be applied
|
|
to unknown options that appear before it.
|
|
|
|
IPQoS Specifies the IPv4 type-of-service or DSCP class for connections.
|
|
Accepted values are ``af11'', ``af12'', ``af13'', ``af21'',
|
|
``af22'', ``af23'', ``af31'', ``af32'', ``af33'', ``af41'',
|
|
``af42'', ``af43'', ``cs0'', ``cs1'', ``cs2'', ``cs3'', ``cs4'',
|
|
``cs5'', ``cs6'', ``cs7'', ``ef'', ``lowdelay'', ``throughput'',
|
|
``reliability'', or a numeric value. This option may take one or
|
|
two arguments, separated by whitespace. If one argument is
|
|
specified, it is used as the packet class unconditionally. If
|
|
two values are specified, the first is automatically selected for
|
|
interactive sessions and the second for non-interactive sessions.
|
|
The default is ``lowdelay'' for interactive sessions and
|
|
``throughput'' for non-interactive sessions.
|
|
|
|
KbdInteractiveAuthentication
|
|
Specifies whether to use keyboard-interactive authentication.
|
|
The argument to this keyword must be ``yes'' or ``no''. The
|
|
default is ``yes''.
|
|
|
|
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: ``bsdauth'', ``pam'',
|
|
and ``skey''.
|
|
|
|
KexAlgorithms
|
|
Specifies the available KEX (Key Exchange) algorithms. Multiple
|
|
algorithms must be comma-separated. The default is:
|
|
|
|
curve25519-sha256@libssh.org,
|
|
ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
|
|
diffie-hellman-group-exchange-sha256,
|
|
diffie-hellman-group-exchange-sha1,
|
|
diffie-hellman-group14-sha1,
|
|
diffie-hellman-group1-sha1
|
|
|
|
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 the user's
|
|
shell. The following escape character substitutions will be
|
|
performed: `%d' (local user's home directory), `%h' (remote host
|
|
name), `%l' (local host name), `%n' (host name as provided on the
|
|
command line), `%p' (remote port), `%r' (remote user name) or
|
|
`%u' (local user name).
|
|
|
|
The command is run synchronously and does not have access to the
|
|
session of the ssh(1) that spawned it. It should not be used for
|
|
interactive commands.
|
|
|
|
This directive is ignored unless PermitLocalCommand has been
|
|
enabled.
|
|
|
|
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 [bind_address:]port and the
|
|
second argument must be host:hostport. IPv6 addresses can be
|
|
specified by enclosing addresses in square brackets. 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 GatewayPorts setting. However, an explicit
|
|
bind_address may be used to bind the connection to a specific
|
|
address. The bind_address of ``localhost'' indicates that the
|
|
listening port be bound for local use only, while an empty
|
|
address or `*' indicates that the port should be available from
|
|
all interfaces.
|
|
|
|
LogLevel
|
|
Gives the verbosity level that is used when logging messages from
|
|
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.
|
|
|
|
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 algorithms that contain ``-etm''
|
|
calculate the MAC after encryption (encrypt-then-mac). These are
|
|
considered safer and their use recommended. The default is:
|
|
|
|
hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,
|
|
umac-64-etm@openssh.com,umac-128-etm@openssh.com,
|
|
hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
|
|
hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,
|
|
hmac-md5-96-etm@openssh.com,
|
|
hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,
|
|
hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
|
|
hmac-sha1-96,hmac-md5-96
|
|
|
|
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 ``yes'' or ``no''. The default is to check the host key
|
|
for localhost.
|
|
|
|
NumberOfPasswordPrompts
|
|
Specifies the number of password prompts before giving up. The
|
|
argument to this keyword must be an integer. The default is 3.
|
|
|
|
PasswordAuthentication
|
|
Specifies whether to use password authentication. The argument
|
|
to this keyword must be ``yes'' or ``no''. The default is
|
|
``yes''.
|
|
|
|
PermitLocalCommand
|
|
Allow local command execution via the LocalCommand option or
|
|
using the !command escape sequence in ssh(1). The argument must
|
|
be ``yes'' or ``no''. The default is ``no''.
|
|
|
|
PKCS11Provider
|
|
Specifies which PKCS#11 provider to use. The argument to this
|
|
keyword is the PKCS#11 shared library ssh(1) should use to
|
|
communicate with a PKCS#11 token providing the user's private RSA
|
|
key.
|
|
|
|
Port Specifies the port number to connect on the remote host. The
|
|
default is 22.
|
|
|
|
PreferredAuthentications
|
|
Specifies the order in which the client should try protocol 2
|
|
authentication methods. This allows a client to prefer one
|
|
method (e.g. keyboard-interactive) over another method (e.g.
|
|
password). The default is:
|
|
|
|
gssapi-with-mic,hostbased,publickey,
|
|
keyboard-interactive,password
|
|
|
|
Protocol
|
|
Specifies the protocol versions ssh(1) should support in order of
|
|
preference. The possible values are `1' and `2'. Multiple
|
|
versions must be comma-separated. When this option is set to
|
|
``2,1'' ssh will try version 2 and fall back to version 1 if
|
|
version 2 is not available. The default is `2'.
|
|
|
|
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 the user's shell. In the command string, any occurrence of
|
|
`%h' will be substituted by the host name to connect, `%p' by the
|
|
port, and `%r' by the remote user name. The command can be
|
|
basically anything, and should read from its standard input and
|
|
write to its standard output. It should eventually connect an
|
|
sshd(8) server running on some machine, or execute 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 ``none'' disables this option
|
|
entirely. Note that CheckHostIP is not available for connects
|
|
with a proxy command.
|
|
|
|
This directive is useful in conjunction with nc(1) and its proxy
|
|
support. For example, the following directive would connect via
|
|
an HTTP proxy at 192.0.2.0:
|
|
|
|
ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
|
|
|
|
ProxyUseFdpass
|
|
Specifies that ProxyCommand will pass a connected file descriptor
|
|
back to ssh(1) instead of continuing to execute and pass data.
|
|
The default is ``no''.
|
|
|
|
PubkeyAuthentication
|
|
Specifies whether to try public key authentication. The argument
|
|
to this keyword must be ``yes'' or ``no''. The default is
|
|
``yes''. This option applies to protocol version 2 only.
|
|
|
|
RekeyLimit
|
|
Specifies the maximum amount of data that may be transmitted
|
|
before the session key is renegotiated, optionally followed a
|
|
maximum amount of time that may pass before the session key is
|
|
renegotiated. The first argument is specified in bytes and may
|
|
have a suffix of `K', `M', or `G' to indicate Kilobytes,
|
|
Megabytes, or Gigabytes, respectively. The default is between
|
|
`1G' and `4G', depending on the cipher. The optional second
|
|
value is specified in seconds and may use any of the units
|
|
documented in the TIME FORMATS section of sshd_config(5). The
|
|
default value for RekeyLimit is ``default none'', which means
|
|
that rekeying is performed after the cipher's default amount of
|
|
data has been sent or received and no time based rekeying is
|
|
done. This option applies to protocol version 2 only.
|
|
|
|
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 [bind_address:]port and the
|
|
second argument must be host:hostport. IPv6 addresses can be
|
|
specified by enclosing addresses in square brackets. Multiple
|
|
forwardings may be specified, and additional forwardings can be
|
|
given on the command line. Privileged ports can be forwarded
|
|
only when logging in as root on the remote machine.
|
|
|
|
If the port argument is `0', the listen port will be dynamically
|
|
allocated on the server and reported to the client at run time.
|
|
|
|
If the bind_address is not specified, the default is to only bind
|
|
to loopback addresses. If the bind_address is `*' or an empty
|
|
string, then the forwarding is requested to listen on all
|
|
interfaces. Specifying a remote bind_address will only succeed
|
|
if the server's GatewayPorts option is enabled (see
|
|
sshd_config(5)).
|
|
|
|
RequestTTY
|
|
Specifies whether to request a pseudo-tty for the session. The
|
|
argument may be one of: ``no'' (never request a TTY), ``yes''
|
|
(always request a TTY when standard input is a TTY), ``force''
|
|
(always request a TTY) or ``auto'' (request a TTY when opening a
|
|
login session). This option mirrors the -t and -T flags for
|
|
ssh(1).
|
|
|
|
RhostsRSAAuthentication
|
|
Specifies whether to try rhosts based authentication with RSA
|
|
host authentication. The argument must be ``yes'' or ``no''.
|
|
The default is ``no''. This option applies to protocol version 1
|
|
only and requires ssh(1) to be setuid root.
|
|
|
|
RSAAuthentication
|
|
Specifies whether to try RSA authentication. The argument to
|
|
this keyword must be ``yes'' or ``no''. RSA authentication will
|
|
only be attempted if the identity file exists, or an
|
|
authentication agent is running. The default is ``yes''. Note
|
|
that this option applies to protocol version 1 only.
|
|
|
|
SendEnv
|
|
Specifies what variables from the local 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 AcceptEnv in 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 SendEnv directives. The
|
|
default is not to send any environment variables.
|
|
|
|
See PATTERNS for more information on patterns.
|
|
|
|
ServerAliveCountMax
|
|
Sets the number of server alive messages (see below) which may be
|
|
sent without 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 TCPKeepAlive (below). The server
|
|
alive messages are sent through the encrypted channel and
|
|
therefore will not be spoofable. The TCP keepalive option
|
|
enabled by TCPKeepAlive is spoofable. The server alive mechanism
|
|
is valuable when the client or server depend on knowing when a
|
|
connection has become inactive.
|
|
|
|
The default value is 3. If, for example, ServerAliveInterval
|
|
(see below) is set to 15 and 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.
|
|
|
|
ServerAliveInterval
|
|
Sets a timeout interval in seconds after which if no data has
|
|
been received from the server, 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.
|
|
|
|
StrictHostKeyChecking
|
|
If this flag is set to ``yes'', ssh(1) will never automatically
|
|
add host keys to the ~/.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 /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 ``no'', ssh will automatically add new host
|
|
keys to the user known hosts files. If this flag is set to
|
|
``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 ``yes'',
|
|
``no'', or ``ask''. The default is ``ask''.
|
|
|
|
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.
|
|
|
|
The default is ``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.
|
|
|
|
To disable TCP keepalive messages, the value should be set to
|
|
``no''.
|
|
|
|
Tunnel Request tun(4) device forwarding between the client and the
|
|
server. The argument must be ``yes'', ``point-to-point'' (layer
|
|
3), ``ethernet'' (layer 2), or ``no''. Specifying ``yes''
|
|
requests the default tunnel mode, which is ``point-to-point''.
|
|
The default is ``no''.
|
|
|
|
TunnelDevice
|
|
Specifies the tun(4) devices to open on the client (local_tun)
|
|
and the server (remote_tun).
|
|
|
|
The argument must be local_tun[:remote_tun]. The devices may be
|
|
specified by numerical ID or the keyword ``any'', which uses the
|
|
next available tunnel device. If remote_tun is not specified, it
|
|
defaults to ``any''. The default is ``any:any''.
|
|
|
|
UsePrivilegedPort
|
|
Specifies whether to use a privileged port for outgoing
|
|
connections. The argument must be ``yes'' or ``no''. The
|
|
default is ``no''. If set to ``yes'', ssh(1) must be setuid
|
|
root. Note that this option must be set to ``yes'' for
|
|
RhostsRSAAuthentication with older servers.
|
|
|
|
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.
|
|
|
|
UserKnownHostsFile
|
|
Specifies one or more files to use for the user host key
|
|
database, separated by whitespace. The default is
|
|
~/.ssh/known_hosts, ~/.ssh/known_hosts2.
|
|
|
|
VerifyHostKeyDNS
|
|
Specifies whether to verify the remote key using DNS and SSHFP
|
|
resource records. If this option is set to ``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 ``ask''. If this option is set to ``ask'', information on
|
|
fingerprint match will be displayed, but the user will still need
|
|
to confirm new host keys according to the StrictHostKeyChecking
|
|
option. The argument must be ``yes'', ``no'', or ``ask''. The
|
|
default is ``no''. Note that this option applies to protocol
|
|
version 2 only.
|
|
|
|
See also VERIFYING HOST KEYS in ssh(1).
|
|
|
|
VisualHostKey
|
|
If this flag is set to ``yes'', an ASCII art representation of
|
|
the remote host key fingerprint is printed in addition to the hex
|
|
fingerprint string at login and for unknown host keys. If this
|
|
flag is set to ``no'', no fingerprint strings are printed at
|
|
login and only the hex fingerprint string will be printed for
|
|
unknown host keys. The default is ``no''.
|
|
|
|
XAuthLocation
|
|
Specifies the full pathname of the xauth(1) program. The default
|
|
is /usr/X11R6/bin/xauth.
|
|
|
|
PATTERNS
|
|
A pattern consists of zero or more non-whitespace characters, `*' (a
|
|
wildcard that matches zero or more characters), or `?' (a wildcard that
|
|
matches exactly one character). For example, to specify a set of
|
|
declarations for any host in the ``.co.uk'' set of domains, the following
|
|
pattern could be used:
|
|
|
|
Host *.co.uk
|
|
|
|
The following pattern would match any host in the 192.168.0.[0-9] network
|
|
range:
|
|
|
|
Host 192.168.0.?
|
|
|
|
A pattern-list is a comma-separated list of patterns. Patterns within
|
|
pattern-lists may be negated by preceding them with an exclamation mark
|
|
(`!'). For example, to allow a key to be used from anywhere within an
|
|
organization except from the ``dialup'' pool, the following entry (in
|
|
authorized_keys) could be used:
|
|
|
|
from="!*.dialup.example.com,*.example.com"
|
|
|
|
FILES
|
|
~/.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.
|
|
|
|
/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.
|
|
|
|
SEE ALSO
|
|
ssh(1)
|
|
|
|
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.
|
|
|
|
OpenBSD 5.5 February 23, 2014 OpenBSD 5.5
|