Config::Model::models::SystemSsh - Configuration class SystemSsh
Configuration classes used by Config::Model
Configuration class used by Config::Model to edit or validate
/etc/ssh/ssh_config (as root)
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 usually the
hostname argument given on the
command line (see the
CanonicalizeHostname keyword for exceptions).
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.
Optional. Type hash of
node of class Ssh::HostElement .
Specifies whether keys should be automatically added to a running
ssh-agent(1). If this option is set to
yes and a key is loaded
from a file, the key and its passphrase are added to the agent with the
default lifetime, as if by
ssh-add(1). If this option is set to
ask,
ssh(1) will require confirmation using the SSH_ASKPASS
program before adding a key (see
ssh-add(1) for details). If this
option is set to
confirm, each use of the key must be confirmed, as if
the
-c option was specified to
ssh-add(1). If this option is set
to
no, no keys are added to the agent. Alternately, this option may be
specified as a time interval using the format described in the
TIME
FORMATS section of
sshd_config(5) to specify the key's lifetime in
ssh-agent(1), after which it will automatically be removed. The
argument must be
no (the default),
yes,
confirm
(optionally followed by a time interval),
ask or a time interval.
Optional. Type enum. choice: 'no', 'yes', 'confirm', 'ask'.
- upstream_default value :
- no
Specifies which address family to use when connecting. Valid arguments are
any (the default),
inet (use IPv4 only), or
inet6 (use
IPv6 only).
Optional. Type enum. choice: 'any', 'inet', 'inet6'.
- upstream_default value :
- any
If set to
yes, user interaction such as password prompts and host key
confirmation requests will be disabled. In addition, the
ServerAliveInterval option will be set to 300 seconds by default
(Debian-specific). This option is useful in scripts and other batch jobs where
no user is present to interact with
ssh(1), and where it is desirable
to detect a broken network swiftly. The argument must be
yes or
no (the default).
Optional. Type boolean.
- upstream_default value :
- no
Use the specified address on the local machine as the source address of the
connection. Only useful on systems with more than one address.
Optional.
Type uniline.
Use the address of the specified interface on the local machine as the source
address of the connection.
Optional. Type uniline.
When
CanonicalizeHostname is enabled, this option specifies the list of
domain suffixes in which to search for the specified destination host.
Optional. Type uniline.
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.
Optional. Type boolean.
- upstream_default value :
- yes
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 or
ProxyJump,
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, then the configuration files are processed again
using the new target name to pick up any new configuration in matching
Host and
Match stanzas. A value of
none disables the use
of a
ProxyJump host.
Optional. Type enum. choice: 'no', 'yes',
'always', 'none'.
- upstream_default value :
- no
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).
Optional. Type integer.
- upstream_default value :
- 1
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.
A single argument of "none" causes no CNAMEs to be considered for
canonicalization. This is the default behaviour.
Optional. Type uniline.
Specifies which algorithms are allowed for signing of certificates by
certificate authorities (CAs). The default is:
ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
[email protected],
[email protected], rsa-sha2-512,
rsa-sha2-256
If the specified list begins with a '+' character, then the specified algorithms
will be appended to the default set instead of replacing them. If the
specified list begins with a '-' character, then the specified algorithms
(including wildcards) will be removed from the default set instead of
replacing them.
ssh(1) will not accept host certificates signed using algorithms other
than those specified.
Optional. Type uniline.
Specifies a file from which the user's certificate is read. A corresponding
private key must be provided separately in order to use this certificate
either from an
IdentityFile directive or
-i flag to
ssh(1), via
ssh-agent(1), or via a
PKCS11Provider or
SecurityKeyProvider.
Arguments to
CertificateFile may use the tilde syntax to refer to a
user's home directory, the tokens described in the
TOKENS section and
environment variables as described in the
ENVIRONMENT VARIABLES
section.
It is possible to have multiple certificate files specified in configuration
files; these certificates will be tried in sequence. Multiple
CertificateFile directives will add to the list of certificates used
for authentication.
Optional. Type uniline.
If set to
yes,
ssh(1) will additionally check the host IP address
in the
known_hosts file. This allows it to detect if a host key changed
due to DNS spoofing and will add addresses of destination hosts to
~/.ssh/known_hosts in the process, regardless of the setting of
StrictHostKeyChecking. If the option is set to
no (the default),
the check will not be executed.
Optional. Type boolean.
- upstream_default value :
- no
Specifies the ciphers allowed and their order of preference. Multiple ciphers
must be comma-separated. If the specified list begins with a '+' character,
then the specified ciphers will be appended to the default set instead of
replacing them. If the specified list begins with a '-' character, then the
specified ciphers (including wildcards) will be removed from the default set
instead of replacing them. If the specified list begins with a '^' character,
then the specified ciphers will be placed at the head of the default set.
The supported ciphers are:
3des-cbc aes128-cbc aes192-cbc aes256-cbc aes128-ctr aes192-ctr aes256-ctr
[email protected] [email protected] [email protected]
The default is:
[email protected], aes128-ctr, aes192-ctr, aes256-ctr,
[email protected],
[email protected]
The list of available ciphers may also be obtained using "ssh -Q
cipher".
Optional. Type uniline.
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).
Optional. Type boolean.
- upstream_default value :
- no
Specifies whether to use compression. The argument must be
yes or
no (the default).
Optional. Type boolean.
- upstream_default value :
- no
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.
Optional. Type integer.
- upstream_default value :
- 1
Specifies the timeout (in seconds) used when connecting to the SSH server,
instead of using the default system TCP timeout. This timeout is applied both
to establishing the connection and to performing the initial SSH protocol
handshake and key exchange.
Optional. Type integer.
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(1) to listen for control
connections, but require confirmation using
ssh-askpass(1). If the
ControlPath cannot be opened,
ssh(1) 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.
Optional. Type enum. choice:
'auto', 'autoask', 'yes', 'no', 'ask'.
- upstream_default value :
- no
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. Arguments to
ControlPath may use the tilde syntax
to refer to a user's home directory, the tokens described in the
TOKENS
section and environment variables as described in the
ENVIRONMENT
VARIABLES section. It is recommended that any
ControlPath used for
opportunistic connection sharing include at least %h, %p, and %r (or
alternatively %C) and be placed in a directory that is not writable by other
users. This ensures that shared connections are uniquely identified.
Optional. Type uniline.
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 (the default), 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 or 0, then the master connection will remain in
the background indefinitely (until killed or closed via a mechanism such as
the "ssh -O exit"). 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.
Optional. Type uniline.
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.
Optional. Type list of uniline.
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). This option should be placed in the
non-hostspecific section. See
ssh-keysign(8) for more information.
Optional. Type boolean.
- upstream_default value :
- no
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).
Optional. Type uniline.
Specifies whether
ssh(1) should terminate the connection if it cannot set
up all requested dynamic, tunnel, local, and remote port forwardings, (e.g. if
either end is unable to bind and listen on a specified port). Note that
ExitOnForwardFailure does not apply to connections made over port
forwardings and will not, for example, cause
ssh(1) to exit if TCP
connections to the ultimate forwarding destination fail. The argument must be
yes or
no (the default).
Optional. Type boolean.
- upstream_default value :
- no
Specifies the hash algorithm used when displaying key fingerprints. Valid
options are:
md5 and
sha256 (the default).
Optional. Type
enum. choice: 'md5', 'sha256'.
- upstream_default value :
- sha256
Requests
ssh to go to background just before command execution. This is
useful if
ssh is going to ask for passwords or passphrases, but the
user wants it in the background. This implies the
StdinNull
configuration option being set to
yes. The recommended way to start X11
programs at a remote site is with something like
ssh -f host
xterm, which is the same as
ssh host xterm if the
ForkAfterAuthentication configuration option is set to
yes.
If the
ExitOnForwardFailure configuration option is set to
yes,
then a client started with the
ForkAfterAuthentication configuration
option being set to
yes will wait for all remote port forwards to be
successfully established before placing itself in the background. The argument
to this keyword must be
yes (same as the
-f option) or
no
(the default).
Optional. Type boolean.
- upstream_default value :
- no
Specifies whether the connection to the authentication agent (if any) will be
forwarded to the remote machine. The argument may be
yes,
no
(the default), an explicit path to an agent socket or the name of an
environment variable (beginning with '$') in which to find the path.
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.
Optional. Type boolean.
- upstream_default value :
- no
Specifies whether X11 connections will be automatically redirected over the
secure channel and DISPLAY set. The argument must be
yes or
no
(the default).
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.
Optional. Type boolean.
- upstream_default value :
- no
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. Setting
ForwardX11Timeout to zero will disable the timeout and permit X11
forwarding for the life of the connection. The default is to disable untrusted
X11 forwarding after twenty minutes has elapsed.
Optional. Type integer.
If this option is set to
yes, (the Debian-specific default), remote X11
clients will have full access to the original X11 display.
If this option is set to
no (the upstream default), 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.
See the X11 SECURITY extension specification for full details on the
restrictions imposed on untrusted clients.
Optional. Type boolean.
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).
Optional. Type boolean.
- upstream_default value :
- no
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.
Optional. Type uniline.
- upstream_default value :
- /etc/ssh/ssh_known_hosts
Specifies whether user authentication based on GSSAPI is allowed. The default is
no.
Optional. Type boolean.
- upstream_default value :
- no
If set, specifies the GSSAPI client identity that ssh should use when connecting
to the server. The default is unset, which means that the default identity
will be used.
Optional. Type uniline.
Forward (delegate) credentials to the server. The default is
no.
Optional. Type boolean.
- upstream_default value :
- no
Specifies whether key exchange based on GSSAPI may be used. When using GSSAPI
key exchange the server need not have a host key. The default is
no.
Optional. Type boolean.
- upstream_default value :
- no
If set to
yes then renewal of the client's GSSAPI credentials will force
the rekeying of the ssh connection. With a compatible server, this will
delegate the renewed credentials to a session on the server.
Checks are made to ensure that credentials are only propagated when the new
credentials match the old ones on the originating client and where the
receiving server still has the old set in its cache.
The default is
no.
For this to work
GSSAPIKeyExchange needs to be enabled in the server and
also used by the client.
Optional. Type boolean.
- upstream_default value :
- no
If set, specifies the GSSAPI server identity that ssh should expect when
connecting to the server. The default is unset, which means that the expected
GSSAPI server identity will be determined from the target hostname.
Optional. Type uniline.
Set to
yes to indicate that the DNS is trusted to securely canonicalize
the name of the host being connected to. If
no, the hostname entered on
the command line will be passed untouched to the GSSAPI library. The default
is
no.
Optional. Type boolean.
- upstream_default value :
- no
The list of key exchange algorithms that are offered for GSSAPI key exchange.
Possible values are
gss-gex-sha1-, gss-group1-sha1-, gss-group14-sha1-, gss-group14-sha256-,
gss-group16-sha512-, gss-nistp256-sha256-, gss-curve25519-sha256-
The default is Xgss-group14-sha256-, gss-group16-sha512-, gss-nistp256-sha256-,
gss-curve25519-sha256-, gss-gex-sha1-, gss-group14-sha1-X. This option only
applies to connections using GSSAPI.
Optional. Type uniline.
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 visually reveal identifying
information if the file's contents are 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). Use of this option may break facilities such as
tab-completion that rely on being able to read unhashed host names from
~/.ssh/known_hosts.
Optional. Type boolean.
- upstream_default value :
- no
Specifies the signature algorithms that will be used for hostbased
authentication as a comma-separated list of patterns. Alternately if the
specified list begins with a '+' character, then the specified signature
algorithms will be appended to the default set instead of replacing them. If
the specified list begins with a '-' character, then the specified signature
algorithms (including wildcards) will be removed from the default set instead
of replacing them. If the specified list begins with a '^' character, then the
specified signature algorithms will be placed at the head of the default set.
The default for this option is:
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
[email protected],
[email protected], rsa-sha2-512,
rsa-sha2-256
The
-Q option of
ssh(1) may be used to list supported signature
algorithms. This was formerly named HostbasedKeyTypes.
Optional. Type
uniline.
Note: HostbasedAcceptedAlgorithms is migrated with '$old' and with:
- •
- $old => "- HostbasedKeyTypes"
Specifies whether to try rhosts based authentication with public key
authentication. The argument must be
yes or
no (the default).
Optional. Type boolean.
- upstream_default value :
- no
Specifies the host key signature algorithms that the client wants to use in
order of preference. Alternately if the specified list begins with a '+'
character, then the specified signature algorithms will be appended to the
default set instead of replacing them. If the specified list begins with a '-'
character, then the specified signature algorithms (including wildcards) will
be removed from the default set instead of replacing them. If the specified
list begins with a '^' character, then the specified signature algorithms will
be placed at the head of the default set. The default for this option is:
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
[email protected],
[email protected], rsa-sha2-512,
rsa-sha2-256
If hostkeys are known for the destination host then this default is modified to
prefer their algorithms.
The list of available signature algorithms may also be obtained using "ssh
-Q HostKeyAlgorithms".
Optional. Type uniline.
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 and when
validating host certificates. This option is useful for tunneling SSH
connections or for multiple servers running on a single host.
Optional.
Type uniline.
Specifies the real host name to log into. This can be used to specify nicknames
or abbreviations for hosts. Arguments to
Hostname accept the tokens
described in the
TOKENS section. Numeric IP addresses are also
permitted (both on the command line and in
Hostname specifications).
The default is the name given on the command line.
Optional. Type uniline.
Specifies that
ssh(1) should only use the configured authentication
identity and certificate files (either the default files, or those explicitly
configured in the
ssh_config files or passed on the
ssh(1)
command-line), even if
ssh-agent(1) or a
PKCS11Provider or
SecurityKeyProvider offers more identities. The argument to this
keyword must be
yes or
no (the default). This option is intended
for situations where ssh-agent offers many different identities.
Optional.
Type boolean.
- upstream_default value :
- no
Specifies the UNIX-domain socket used to communicate with the authentication
agent.
This option overrides the SSH_AUTH_SOCK environment variable and can be used to
select a specific agent. Setting the socket name to
none disables the
use of an authentication agent. If the string "SSH_AUTH_SOCK" is
specified, the location of the socket will be read from the SSH_AUTH_SOCK
environment variable. Otherwise if the specified value begins with a '$'
character, then it will be treated as an environment variable containing the
location of the socket.
Arguments to
IdentityAgent may use the tilde syntax to refer to a user's
home directory, the tokens described in the
TOKENS section and
environment variables as described in the
ENVIRONMENT VARIABLES
section.
Optional. Type uniline.
Specifies a file from which the user's DSA, ECDSA, authenticator-hosted ECDSA,
Ed25519, authenticator-hosted Ed25519 or RSA authentication identity is read.
The default is
~/.ssh/id_rsa,
~/.ssh/id_ecdsa,
~/.ssh/id_ecdsa_sk,
~/.ssh/id_ed25519,
~/.ssh/id_ed25519_sk and
~/.ssh/id_dsa. Additionally, any
identities represented by the authentication agent will be used for
authentication unless
IdentitiesOnly is set. If no certificates have
been explicitly specified by
CertificateFile,
ssh(1) will try to
load certificate information from the filename obtained by appending
-cert.pub to the path of a specified
IdentityFile.
Arguments to
IdentityFile may use the tilde syntax to refer to a user's
home directory or the tokens described in the
TOKENS section.
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.
IdentityFile may also be used in conjunction with
CertificateFile in order to provide any certificate also needed for
authentication with the identity.
Optional. Type list of uniline.
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.
Optional. Type uniline.
Include the specified configuration file(s). Multiple pathnames may be specified
and each pathname may contain
glob(7) wildcards and, for user
configurations, shell-like '~' references to user home directories. Wildcards
will be expanded and processed in lexical order. Files without absolute paths
are assumed to be in
~/.ssh if included in a user configuration file or
/etc/ssh if included from the system configuration file.
Include
directive may appear inside a
Match or
Host block to perform
conditional inclusion.
Optional. Type list of uniline.
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,
le,
lowdelay,
throughput,
reliability, a numeric value, or
none to use
the operating system default. 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.
Optional.
Type uniline.
- upstream_default value :
- af21 cs1
Specifies whether to use keyboard-interactive authentication. The argument to
this keyword must be
yes (the default) or
no.
ChallengeResponseAuthentication is a deprecated alias for this.
Optional. Type boolean.
- upstream_default value :
- yes
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 and
pam.
Optional. Type list of uniline.
Specifies the available KEX (Key Exchange) algorithms. Multiple algorithms must
be comma-separated. If the specified list begins with a '+' character, then
the specified algorithms will be appended to the default set instead of
replacing them. If the specified list begins with a '-' character, then the
specified algorithms (including wildcards) will be removed from the default
set instead of replacing them. If the specified list begins with a '^'
character, then the specified algorithms will be placed at the head of the
default set. The default is:
[email protected], curve25519-sha256,
[email protected], ecdh-sha2-nistp256, ecdh-sha2-nistp384,
ecdh-sha2-nistp521, diffie-hellman-group-exchange-sha256,
diffie-hellman-group16-sha512, diffie-hellman-group18-sha512,
diffie-hellman-group14-sha256
The list of available key exchange algorithms may also be obtained using
"ssh -Q kex".
Optional. Type uniline.
Specifies a command to use to obtain a list of host keys, in addition to those
listed in
UserKnownHostsFile and
GlobalKnownHostsFile. This
command is executed after the files have been read. It may write host key
lines to standard output in identical format to the usual files (described in
the
VERIFYING HOST KEYS section in
ssh(1)). Arguments to
KnownHostsCommand accept the tokens described in the
TOKENS
section. The command may be invoked multiple times per connection: once when
preparing the preference list of host key algorithms to use, again to obtain
the host key for the requested host name and, if
CheckHostIP is
enabled, one more time to obtain the host key matching the server's address.
If the command exits abnormally or returns a non-zero exit status then the
connection is terminated.
Optional. Type uniline.
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. Arguments to
LocalCommand accept
the tokens described in the
TOKENS section.
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.
Optional. Type uniline.
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 specifies the listener and may be [
bind_address: ]
port or a Unix domain socket path. The second
argument is the destination and may be
host:
hostport or a Unix
domain socket path if the remote host supports it.
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. Unix domain socket paths may use the tokens described in the
TOKENS section and environment variables as described in the
ENVIRONMENT VARIABLES section.
Optional. Type list of node
of class Ssh::PortForward .
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.
Optional.
Type enum. choice: 'QUIET', 'FATAL', 'ERROR', 'INFO', 'VERBOSE', 'DEBUG',
'DEBUG1', 'DEBUG2', 'DEBUG3'.
- upstream_default value :
- INFO
Specify one or more overrides to LogLevel. An override consists of a pattern
lists that matches the source file, function and line number to force detailed
logging for. For example, an override pattern of:
kex.c:*:1000,*:
kex_exchange_identification():*, packet.c:*
would enable detailed logging for line 1000 of
kex.c, everything in the
kex_exchange_identification() function, and all code in the
packet.c file. This option is intended for debugging and no overrides
are enabled by default.
Optional. Type uniline.
Specifies the MAC (message authentication code) algorithms in order of
preference. The MAC algorithm is used for data integrity protection. Multiple
algorithms must be comma-separated. If the specified list begins with a '+'
character, then the specified algorithms will be appended to the default set
instead of replacing them. If the specified list begins with a '-' character,
then the specified algorithms (including wildcards) will be removed from the
default set instead of replacing them. If the specified list begins with a '^'
character, then the specified algorithms will be placed at the head of the
default set.
The algorithms that contain "-etm" calculate the MAC after encryption
(encrypt-then-mac). These are considered safer and their use recommended.
The default is:
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
hmac-sha2-256, hmac-sha2-512, hmac-sha1
The list of available MAC algorithms may also be obtained using "ssh -Q
mac".
Optional. Type uniline.
Disable host authentication for localhost (loopback addresses). The argument to
this keyword must be
yes or
no (the default).
Optional. Type
boolean.
- upstream_default value :
- no
Specifies the number of password prompts before giving up. The argument to this
keyword must be an integer. The default is 3.
Optional. Type integer.
- upstream_default value :
- 3
Specifies whether to use password authentication. The argument to this keyword
must be
yes (the default) or
no.
Optional. Type boolean.
- upstream_default value :
- yes
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).
Optional. Type boolean.
- upstream_default value :
- no
Specifies the destinations to which remote TCP port forwarding is permitted when
RemoteForward is used as a SOCKS proxy. The forwarding specification
must be one of the following forms:
PermitRemoteOpenhost:
port PermitRemoteOpen
IPv4_addr:
port PermitRemoteOpen
[IPv6_addr]:
port
Multiple forwards may be specified by separating them with whitespace. An
argument of
any can be used to remove all restrictions and permit any
forwarding requests. An argument of
none can be used to prohibit all
forwarding requests. The wildcard '*' can be used for host or port to allow
all hosts or ports respectively. Otherwise, no pattern matching or address
lookups are performed on supplied names.
Optional. Type list of uniline.
Specifies which PKCS#11 provider to use or
none to indicate that no
provider should be used (the default). The argument to this keyword is a path
to the PKCS#11 shared library
ssh(1) should use to communicate with a
PKCS#11 token providing keys for user authentication.
Optional. Type
uniline.
Specifies the port number to connect on the remote host. The default is 22.
Optional. Type uniline.
Specifies the order in which the client should try 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.
Optional. Type list of uniline.
Specifies the command to use to connect to the server. The command string
extends to the end of the line, and is executed using the user's shell 'exec'
directive to avoid a lingering shell process.
Arguments to
ProxyCommand accept the tokens described in the
TOKENS section. 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.
Optional. Type
uniline.
Specifies one or more jump proxies as either
[
user@]
host[:
port] or an ssh URI . Multiple proxies may be
separated by comma characters and will be visited sequentially. Setting this
option will cause
ssh(1) to connect to the target host by first making
a
ssh(1) connection to the specified
ProxyJump host and then
establishing a TCP forwarding to the ultimate target from there. Setting the
host to
none disables this option entirely.
Note that this option will compete with the
ProxyCommand option -
whichever is specified first will prevent later instances of the other from
taking effect.
Note also that the configuration for the destination host (either supplied via
the command-line or the configuration file) is not generally applied to jump
hosts.
~/.ssh/config should be used if specific configuration is
required for jump hosts.
Optional. Type list of uniline.
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.
Optional. Type boolean.
- upstream_default value :
- no
Specifies the signature algorithms that will be used for public key
authentication as a comma-separated list of patterns. If the specified list
begins with a '+' character, then the algorithms after it will be appended to
the default instead of replacing it. If the specified list begins with a '-'
character, then the specified algorithms (including wildcards) will be removed
from the default set instead of replacing them. If the specified list begins
with a '^' character, then the specified algorithms will be placed at the head
of the default set. The default for this option is:
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
[email protected],
ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
[email protected],
[email protected], rsa-sha2-512,
rsa-sha2-256
The list of available signature algorithms may also be obtained using "ssh
-Q PubkeyAcceptedAlgorithms".
Optional. Type uniline.
Note: PubkeyAcceptedAlgorithms is migrated with '$old' and with:
- •
- $old => "- PubkeyAcceptedKeyTypes"
Specifies whether to try public key authentication. The argument to this keyword
must be
yes (the default),
no,
unbound or
host-bound. The final two options enable public key authentication
while respectively disabling or enabling the OpenSSH host-bound authentication
protocol extension required for restricted
ssh-agent(1) forwarding.
Optional. Type enum. choice: 'yes', 'no', 'unbound', 'host-bound'.
- upstream_default value :
- yes
Specifies the maximum amount of data that may be transmitted before the session
key is renegotiated, optionally followed by 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.
Optional. Type uniline.
Specifies a command to execute on the remote 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. Arguments to
RemoteCommand
accept the tokens described in the
TOKENS section.
Optional. Type
uniline.
Specifies that a TCP port on the remote machine be forwarded over the secure
channel. The remote port may either be forwarded to a specified host and port
from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
client to connect to arbitrary destinations from the local machine. The first
argument is the listening specification and may be [
bind_address: ]
port or, if the remote host supports it, a Unix
domain socket path. If forwarding to a specific destination then the second
argument must be
host:
hostport or a Unix domain socket path,
otherwise if no destination argument is specified then the remote forwarding
will be established as a SOCKS proxy. When acting as a SOCKS proxy, the
destination of the connection can be restricted by
PermitRemoteOpen.
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. Unix domain socket paths may use the tokens
described in the
TOKENS section and environment variables as described
in the
ENVIRONMENT VARIABLES section.
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)).
Optional. Type list of node
of class Ssh::PortForward .
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).
Optional. Type enum.
choice: 'no', 'yes', 'force', 'auto'.
Specifies revoked host public keys. Keys listed in this file will be refused for
host authentication. Note that if this file does not exist or is not readable,
then host authentication will be refused for all hosts. Keys may be specified
as a text file, listing one public key per line, or as an OpenSSH Key
Revocation List (KRL) as generated by
ssh-keygen(1). For more
information on KRLs, see the KEY REVOCATION LISTS section in
ssh-keygen(1).
Optional. Type uniline.
Specifies a path to a library that will be used when loading any FIDO
authenticator-hosted keys, overriding the default of using the built-in USB
HID support.
If the specified value begins with a '$' character, then it will be treated as
an environment variable containing the path to the library.
Optional. Type
uniline.
Specifies what variables from the local
environ(7) should be sent to the
server. The server must also support it, and the server must be configured to
accept these environment variables. Note that the TERM environment variable is
always sent whenever a pseudo-terminal is requested as it is required by the
protocol. 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.
See
PATTERNS for more information on patterns.
It is possible to clear previously set
SendEnv variable names by
prefixing patterns with
-. The default is not to send any environment
variables.
Optional. Type list of uniline.
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 unresponsive.
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.
Optional. Type integer.
- upstream_default value :
- 3
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, or 300 if the
BatchMode option
is set (Debian-specific).
ProtocolKeepAlives and
SetupTimeOut
are Debian-specific compatibility aliases for this option.
Optional. Type
integer.
- upstream_default value :
- 0
May be used to either request invocation of a subsystem on the remote system, or
to prevent the execution of a remote command at all. The latter is useful for
just forwarding ports. The argument to this keyword must be
none (same
as the
-N option),
subsystem (same as the
-s option) or
default (shell or command execution).
Optional. Type enum. choice:
'none', 'subsystem', 'default'.
Directly specify one or more environment variables and their contents to be sent
to the server. Similarly to
SendEnv, with the exception of the TERM
variable, the server must be prepared to accept the environment variable.
Optional. Type uniline.
Redirects stdin from
/dev/null (actually, prevents reading from stdin).
Either this or the equivalent
-n option must be used when
ssh is
run in the background. The argument to this keyword must be
yes (same
as the
-n option) or
no (the default).
Optional. Type
boolean.
- upstream_default value :
- no
Sets the octal file creation mode mask (umask) used when creating a Unix-domain
socket file for local or remote port forwarding. This option is only used for
port forwarding to a Unix-domain socket file.
The default value is 0177, which creates a Unix-domain socket file that is
readable and writable only by the owner. Note that not all operating systems
honor the file mode on Unix-domain socket files.
Optional. Type uniline.
Specifies whether to remove an existing Unix-domain socket file for local or
remote port forwarding before creating a new one. If the socket file already
exists and
StreamLocalBindUnlink is not enabled,
ssh will be
unable to forward the port to the Unix-domain socket file. This option is only
used for port forwarding to a Unix-domain socket file.
The argument must be
yes or
no (the default).
Optional. Type
boolean.
- upstream_default value :
- no
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
man-in-the-middle (MITM) 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
accept-new then ssh will automatically add new
host keys to the user's
known_hosts file, but will not permit
connections to hosts with changed host keys. If this flag is set to
no
or
off, ssh will automatically add new host keys to the user known
hosts files and allow connections to hosts with changed hostkeys to proceed,
subject to some restrictions. If this flag is set to
ask (the default),
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.
Optional. Type enum. choice:
'yes', 'accept-new', 'no', 'off', 'ask'.
- upstream_default value :
- ask
Gives the facility code that is used when logging messages from
ssh(1).
The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3,
LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is USER.
Optional. Type enum.
choice: 'DAEMON', 'USER', 'AUTH', 'LOCAL0', 'LOCAL1', 'LOCAL2', 'LOCAL3',
'LOCAL4', 'LOCAL5', 'LOCAL6', 'LOCAL7'.
- upstream_default value :
- USER
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. This option only uses TCP keepalives (as
opposed to using ssh level keepalives), so takes a long time to notice when
the connection dies. As such, you probably want the
ServerAliveInterval
option as well. 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. See
also
ServerAliveInterval for protocol-level keepalives.
Optional.
Type boolean.
- upstream_default value :
- yes
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 (the default). Specifying
yes requests the
default tunnel mode, which is
point-to-point.
Optional. Type enum.
choice: 'yes', 'point-to-point', 'ethernet', 'no'.
- upstream_default value :
- no
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.
Optional. Type uniline.
- upstream_default value :
- any:any
Specifies whether
ssh(1) should accept notifications of additional
hostkeys from the server sent after authentication has completed and add them
to
UserKnownHostsFile. The argument must be
yes,
no or
ask. This option allows learning alternate hostkeys for a server and
supports graceful key rotation by allowing a server to send replacement public
keys before old ones are removed.
Additional hostkeys are only accepted if the key used to authenticate the host
was already trusted or explicitly accepted by the user, the host was
authenticated via
UserKnownHostsFile (i.e. not
GlobalKnownHostsFile) and the host was authenticated using a plain key
and not a certificate.
UpdateHostKeys is enabled by default if the user has not overridden the
default
UserKnownHostsFile setting and has not enabled
VerifyHostKeyDNS, otherwise
UpdateHostKeys will be set to
no.
If
UpdateHostKeys is set to
ask, then the user is asked to confirm
the modifications to the known_hosts file. Confirmation is currently
incompatible with
ControlPersist, and will be disabled if it is
enabled.
Presently, only
sshd(8) from OpenSSH 6.8 and greater support the
"
[email protected]" protocol extension used to inform the client
of all the server's hostkeys.
Optional. Type enum. choice: 'yes', 'no',
'ask'.
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.
Optional. Type uniline.
Specifies one or more files to use for the user host key database, separated by
whitespace. Each filename may use tilde notation to refer to the user's home
directory, the tokens described in the
TOKENS section and environment
variables as described in the
ENVIRONMENT VARIABLES section. The
default is
~/.ssh/known_hosts,
~/.ssh/known_hosts2.
Optional. Type uniline.
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 default is
no.
See also
VERIFYING HOST KEYS in
ssh(1).
Optional. Type enum.
choice: 'yes', 'ask', 'no'.
- upstream_default value :
- no
If this flag is set to
yes, an ASCII art representation of the remote
host key fingerprint is printed in addition to the fingerprint string at login
and for unknown host keys. If this flag is set to
no (the default), no
fingerprint strings are printed at login and only the fingerprint string will
be printed for unknown host keys.
Optional. Type uniline.
- upstream_default value :
- no
Specifies the full pathname of the
xauth(1) program. The default is
/usr/bin/xauth.
Optional. Type uniline.
- upstream_default value :
- /usr/bin/xauth
This parameter is now ignored by Ssh.
Deprecated Optional. Type
uniline.
This parameter is now ignored by Ssh.
Deprecated Optional. Type
uniline.
This parameter is now ignored by Ssh.
Deprecated Optional. Type
uniline.
This parameter is now ignored by Ssh.
Deprecated Optional. Type
uniline.
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
criteria or the single token
all which always matches. The available
criteria keywords are:
canonical,
final,
exec,
host,
originalhost,
user, and
localuser. The
all criteria must appear alone or immediately after
canonical or
final. Other criteria may be combined arbitrarily. All criteria but
all,
canonical, and
final require an argument. Criteria
may be negated by prepending an exclamation mark ('!').
The
canonical keyword matches only when the configuration file is being
re-parsed after hostname canonicalization (see the
CanonicalizeHostname
option). This may be useful to specify conditions that work with canonical
host names only.
The
final keyword requests that the configuration be re-parsed
(regardless of whether
CanonicalizeHostname is enabled), and matches
only during this final pass. If
CanonicalizeHostname is enabled, then
canonical and
final match during the same pass.
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. Arguments to
exec accept the tokens described in the
TOKENS section.
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 or
CanonicalizeHostname options. 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).
Optional. Type hash of node of class Ssh::HostElement .
- •
- cme
- •
- Config::Model::models::Ssh::HostElement
- •
- Config::Model::models::Ssh::PortForward
- Dominique Dumont
- 2013 Dominique Dumont
- LGPL2