# PODNAME: Config::Model::models::SystemSsh
# ABSTRACT:  Configuration class SystemSsh

=encoding utf8

=head1 NAME

Config::Model::models::SystemSsh - Configuration class SystemSsh

=head1 DESCRIPTION

Configuration classes used by L<Config::Model>

Configuration class used by L<Config::Model> to edit or 
validate /etc/ssh/ssh_config (as root)


=head1 Elements

=head2 Host

Restricts the
following declarations (up to the next B<Host> or
B<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 I<hostname> argument given on the command
line (see the B<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
B<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
I<PATTERNS> for more information on patterns. I< Optional. Type hash of node of class L<Ssh::HostElement|Config::Model::models::Ssh::HostElement> .  > 

=head2 AddKeysToAgent

Specifies whether keys should
be automatically added to a running L<ssh-agent(1)>. If this
option is set to B<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 L<ssh-add(1)>. If this option is set
to B<ask>, L<ssh(1)> will require confirmation using the
SSH_ASKPASS program before adding a key (see L<ssh-add(1)> for
details). If this option is set to B<confirm>, each use
of the key must be confirmed, as if the B<-c> option was
specified to L<ssh-add(1)>. If this option is set to B<no>,
no keys are added to the agent. Alternately, this option may
be specified as a time interval using the format described
in the I<TIME FORMATS> section of L<sshd_config(5)> to
specify the key's lifetime in L<ssh-agent(1)>, after
which it will automatically be removed. The argument must be
B<no> (the default), B<yes>, B<confirm>
(optionally followed by a time interval), B<ask> or a
time interval. I< Optional. Type enum. choice: 'no', 'yes', 'confirm', 'ask'.  > 

=over 4

=item upstream_default value :

no

=back



=head2 AddressFamily

Specifies which address family
to use when connecting. Valid arguments are B<any> (the
default), B<inet> (use IPv4 only), or B<inet6> (use
IPv6 only). I< Optional. Type enum. choice: 'any', 'inet', 'inet6'.  > 

=over 4

=item upstream_default value :

any

=back



=head2 BatchMode

If set to B<yes>, user
interaction such as password prompts and host key
confirmation requests will be disabled. In addition, the
B<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 L<ssh(1)>, and where it is desirable to detect a
broken network swiftly. The argument must be B<yes> or
B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 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. I< Optional. Type uniline.  > 

=head2 BindInterface

Use the address of the
specified interface on the local machine as the source
address of the connection. I< Optional. Type uniline.  > 

=head2 CanonicalDomains

When
B<CanonicalizeHostname> is enabled, this option
specifies the list of domain suffixes in which to search for
the specified destination host. I< Optional. Type uniline.  > 

=head2 CanonicalizeFallbackLocal

Specifies whether to fail with
an error when hostname canonicalization fails. The default,
B<yes>, will attempt to look up the unqualified hostname
using the system resolver's search rules. A value of
B<no> will cause L<ssh(1)> to fail instantly if
B<CanonicalizeHostname> is enabled and the target
hostname cannot be found in any of the domains specified by
B<CanonicalDomains>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

yes

=back



=head2 CanonicalizeHostname

Controls whether explicit
hostname canonicalization is performed. The default,
B<no>, is not to perform any name rewriting and let the
system resolver handle all hostname lookups. If set to
B<yes> then, for connections that do not use a
B<ProxyCommand> or B<ProxyJump>, L<ssh(1)> will attempt
to canonicalize the hostname specified on the command line
using the B<CanonicalDomains> suffixes and
B<CanonicalizePermittedCNAMEs> rules. If
B<CanonicalizeHostname> is set to B<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 B<Host> and B<Match> stanzas. A value of
B<none> disables the use of a B<ProxyJump> host. I< Optional. Type enum. choice: 'no', 'yes', 'always', 'none'.  > 

=over 4

=item upstream_default value :

no

=back



=head2 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). I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

1

=back



=head2 CanonicalizePermittedCNAMEs

Specifies rules to determine
whether CNAMEs should be followed when canonicalizing
hostnames. The rules consist of one or more arguments of
I<source_domain_list>:I<target_domain_list>, where
I<source_domain_list> is a pattern-list of domains that
may follow CNAMEs in canonicalization, and
I<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. I< Optional. Type uniline.  > 

=head2 CASignatureAlgorithms

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,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
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.

L<ssh(1)> will not
accept host certificates signed using algorithms other than
those specified. I< Optional. Type uniline.  > 

=head2 CertificateFile

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 B<IdentityFile> directive or
B<-i> flag to L<ssh(1)>, via L<ssh-agent(1)>, or via a
B<PKCS11Provider> or B<SecurityKeyProvider>.

Arguments to
B<CertificateFile> may use the tilde syntax to refer to
a user's home directory, the tokens described in the
I<TOKENS> section and environment variables as described
in the I<ENVIRONMENT VARIABLES> section.

It is possible
to have multiple certificate files specified in
configuration files; these certificates will be tried in
sequence. Multiple B<CertificateFile> directives will
add to the list of certificates used for authentication. I< Optional. Type uniline.  > 

=head2 CheckHostIP

If set to B<yes> L<ssh(1)>
will additionally check the host IP address in the
I<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 I<~/.ssh/known_hosts> in the
process, regardless of the setting of
B<StrictHostKeyChecking>. If the option is set to
B<no> (the default), the check will not be executed. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 Ciphers

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
aes128-gcm@openssh.com
aes256-gcm@openssh.com
chacha20-poly1305@openssh.com

The default
is:

chacha20-poly1305@openssh.com,
aes128-ctr, aes192-ctr, aes256-ctr,
aes128-gcm@openssh.com, aes256-gcm@openssh.com

The list of
available ciphers may also be obtained using "ssh -Q
cipher". I< Optional. Type uniline.  > 

=head2 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 L<ssh(1)> command
line to clear port forwardings set in configuration files,
and is automatically set by L<scp(1)> and L<sftp(1)>. The argument
must be B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 Compression

Specifies whether to use
compression. The argument must be B<yes> or B<no>
(the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 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. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

1

=back



=head2 ConnectTimeout

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. I< Optional. Type integer.  > 

=head2 ControlMaster

Enables the sharing of multiple
sessions over a single network connection. When set to
B<yes>, L<ssh(1)> will listen for connections on a control
socket specified using the B<ControlPath> argument.
Additional sessions can connect to this socket using the
same B<ControlPath> with B<ControlMaster> set to
B<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
B<ask> will cause L<ssh(1)> to listen for control
connections, but require confirmation using L<ssh-askpass(1)>.
If the B<ControlPath> cannot be opened, L<ssh(1)> will
continue without connecting to a master instance.

X11 and
L<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: B<auto> and
B<autoask>. The latter requires confirmation like the
B<ask> option. I< Optional. Type enum. choice: 'auto', 'autoask', 'yes', 'no', 'ask'.  > 

=over 4

=item upstream_default value :

no

=back



=head2 ControlPath

Specify the path to the control
socket used for connection sharing as described in the
B<ControlMaster> section above or the string B<none>
to disable connection sharing. Arguments to
B<ControlPath> may use the tilde syntax to refer to a
user's home directory, the tokens described in the
I<TOKENS> section and environment variables as described
in the I<ENVIRONMENT VARIABLES> section. It is
recommended that any B<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. I< Optional. Type uniline.  > 

=head2 ControlPersist

When used in conjunction with
B<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 B<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 B<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 L<sshd_config(5)>, then the
backgrounded master connection will automatically terminate
after it has remained idle (with no client connections) for
the specified time. I< Optional. Type uniline.  > 

=head2 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 [

I<bind_address>: ]I<port>. IPv6 addresses can be
specified by enclosing addresses in square brackets. By
default, the local port is bound in accordance with the
B<GatewayPorts> setting. However, an explicit
I<bind_address> may be used to bind the connection to a
specific address. The I<bind_address> of
B<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 L<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. I< Optional. Type list of uniline.  > 

=head2 EnableSSHKeysign

Setting this option to
B<yes> in the global client configuration file
I</etc/ssh/ssh_config> enables the use of the helper
program L<ssh-keysign(8)> during
B<HostbasedAuthentication>. The argument must be
B<yes> or B<no> (the default). This option should be
placed in the non-hostspecific section. See L<ssh-keysign(8)>
for more information. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 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
B<none> to disable the escape character entirely (making
the connection transparent for binary data). I< Optional. Type uniline.  > 

=head2 ExitOnForwardFailure

Specifies whether L<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 B<ExitOnForwardFailure> does not apply
to connections made over port forwardings and will not, for
example, cause L<ssh(1)> to exit if TCP connections to the
ultimate forwarding destination fail. The argument must be
B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 FingerprintHash

Specifies the hash algorithm
used when displaying key fingerprints. Valid options are:
B<md5> and B<sha256> (the default). I< Optional. Type enum. choice: 'md5', 'sha256'.  > 

=over 4

=item upstream_default value :

sha256

=back



=head2 ForkAfterAuthentication

Requests B<ssh> to go to
background just before command execution. This is useful if
B<ssh> is going to ask for passwords or passphrases, but
the user wants it in the background. This implies the
B<StdinNull> configuration option being set to
B<yes>. The recommended way to start X11 programs
at a remote site is with something like B<ssh -f host
xterm>, which is the same as B<ssh host xterm> if the
B<ForkAfterAuthentication> configuration option is set
to B<yes>.

If the
B<ExitOnForwardFailure> configuration option is set to
B<yes>, then a client started with the
B<ForkAfterAuthentication> configuration option being
set to B<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 B<yes> (same as the B<-f> option) or B<no>
(the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 ForwardAgent

Specifies whether the
connection to the authentication agent (if any) will be
forwarded to the remote machine. The argument may be
B<yes>, B<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. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 ForwardX11

Specifies whether X11
connections will be automatically redirected over the secure
channel and DISPLAY set. The argument must be B<yes> or
B<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 B<ForwardX11Trusted> option
is also enabled. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 ForwardX11Timeout

Specify a timeout for untrusted
X11 forwarding using the format described in the I<TIME
FORMATS> section of L<sshd_config(5)>. X11 connections
received by L<ssh(1)> after this time will be refused. Setting
B<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. I< Optional. Type integer.  > 

=head2 ForwardX11Trusted

If this option is set to
B<yes>, (the Debian-specific default), remote X11
clients will have full access to the original X11
display.

If this option
is set to B<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 L<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. I< Optional. Type boolean.  > 

=head2 GatewayPorts

Specifies whether remote hosts
are allowed to connect to local forwarded ports. By default,
L<ssh(1)> binds local port forwardings to the loopback address.
This prevents other remote hosts from connecting to
forwarded ports. B<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 B<yes> or B<no> (the
default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GlobalKnownHostsFile

Specifies one or more files to
use for the global host key database, separated by
whitespace. The default is I</etc/ssh/ssh_known_hosts>,
I</etc/ssh/ssh_known_hosts2>. I< Optional. Type uniline.  > 

=over 4

=item upstream_default value :

/etc/ssh/ssh_known_hosts

=back



=head2 GSSAPIAuthentication

Specifies whether user
authentication based on GSSAPI is allowed. The default is
B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GSSAPIClientIdentity

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. I< Optional. Type uniline.  > 

=head2 GSSAPIDelegateCredentials

Forward (delegate) credentials
to the server. The default is B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GSSAPIKeyExchange

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
B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GSSAPIRenewalForcesRekey

If set to B<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
B<no>.

For this to
work B<GSSAPIKeyExchange> needs to be enabled in the
server and also used by the client. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GSSAPIServerIdentity

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. I< Optional. Type uniline.  > 

=head2 GSSAPITrustDns

Set to B<yes> to
indicate that the DNS is trusted to securely canonicalize
the name of the host being connected to. If
B<no>, the hostname entered on the command line
will be passed untouched to the GSSAPI library. The default
is B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 GSSAPIKexAlgorithms

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
“gss-group14-sha256-, gss-group16-sha512-, gss-nistp256-sha256-, gss-curve25519-sha256-, gss-gex-sha1-, gss-group14-sha1-”.
This option only applies to connections using GSSAPI. I< Optional. Type uniline.  > 

=head2 HashKnownHosts

Indicates that L<ssh(1)> should
hash host names and addresses when they are added to
I<~/.ssh/known_hosts>. These hashed names may be used
normally by L<ssh(1)> and L<sshd(8)>, but they do not visually
reveal identifying information if the file's contents
are disclosed. The default is B<no>. Note that existing
names and addresses in known hosts files will not be
converted automatically, but may be manually hashed using
L<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 I<~/.ssh/known_hosts>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 HostbasedAcceptedAlgorithms

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:

ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512, rsa-sha2-256, ssh-rsa

The B<-Q>
option of L<ssh(1)> may be used to list supported signature
algorithms. This was formerly named HostbasedKeyTypes. I< Optional. Type uniline.  > 

Note: HostbasedAcceptedAlgorithms is migrated with 'C<$old>' and with: 

=over

=item *

C<$old> => C<- HostbasedKeyTypes>

=back



=head2 HostbasedAuthentication

Specifies whether to try rhosts
based authentication with public key authentication. The
argument must be B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 HostKeyAlgorithms

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:

ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
sk-ecdsa-sha2-nistp256@openssh.com,
sk-ssh-ed25519@openssh.com,
rsa-sha2-512, rsa-sha2-256, ssh-rsa

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". I< Optional. Type uniline.  > 

=head2 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 and when
validating host certificates. This option is useful for
tunneling SSH connections or for multiple servers running on
a single host. I< Optional. Type uniline.  > 

=head2 Hostname

Specifies the real host name to
log into. This can be used to specify nicknames or
abbreviations for hosts. Arguments to B<Hostname> accept
the tokens described in the I<TOKENS> section. Numeric
IP addresses are also permitted (both on the command line
and in B<Hostname> specifications). The default is the
name given on the command line. I< Optional. Type uniline.  > 

=head2 IdentitiesOnly

Specifies that L<ssh(1)> should
only use the configured authentication identity and
certificate files (either the default files, or those
explicitly configured in the B<ssh_config> files or
passed on the L<ssh(1)> command-line), even if L<ssh-agent(1)> or
a B<PKCS11Provider> or B<SecurityKeyProvider> offers
more identities. The argument to this keyword must be
B<yes> or B<no> (the default). This option is
intended for situations where ssh-agent offers many
different identities. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 IdentityAgent

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
B<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
B<IdentityAgent> may use the tilde syntax to refer to a
user's home directory, the tokens described in the
I<TOKENS> section and environment variables as described
in the I<ENVIRONMENT VARIABLES> section. I< Optional. Type uniline.  > 

=head2 IdentityFile

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 I<~/.ssh/id_dsa>,
I<~/.ssh/id_ecdsa>, I<~/.ssh/id_ecdsa_sk>,
I<~/.ssh/id_ed25519>, I<~/.ssh/id_ed25519_sk> and
I<~/.ssh/id_rsa>. Additionally, any identities
represented by the authentication agent will be used for
authentication unless B<IdentitiesOnly> is set. If no
certificates have been explicitly specified by
B<CertificateFile>, L<ssh(1)> will try to load certificate
information from the filename obtained by appending
I<-cert.pub> to the path of a specified
B<IdentityFile>.

Arguments to
B<IdentityFile> may use the tilde syntax to refer to a
user's home directory or the tokens described in the
I<TOKENS> section.

It is possible
to have multiple identity files specified in configuration
files; all these identities will be tried in sequence.
Multiple B<IdentityFile> directives will add to the list
of identities tried (this behaviour differs from that of
other configuration directives).

B<IdentityFile>
may be used in conjunction with B<IdentitiesOnly> to
select which identities in an agent are offered during
authentication. B<IdentityFile> may also be used in
conjunction with B<CertificateFile> in order to provide
any certificate also needed for authentication with the
identity. I< Optional. Type list of uniline.  > 

=head2 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 B<ssh_config> contains options that are unrecognised
by L<ssh(1)>. It is recommended that B<IgnoreUnknown> be
listed early in the configuration file as it will not be
applied to unknown options that appear before it. I< Optional. Type uniline.  > 

=head2 Include

Include the specified
configuration file(s). Multiple pathnames may be specified
and each pathname may contain L<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 I<~/.ssh> if included in a user
configuration file or I</etc/ssh> if included from the
system configuration file. B<Include> directive may
appear inside a B<Match> or B<Host> block to perform
conditional inclusion. I< Optional. Type list of uniline.  > 

=head2 IPQoS

Specifies the
IPv4 type-of-service or DSCP class for connections. Accepted
values are B<af11>, B<af12>, B<af13>,
B<af21>, B<af22>, B<af23>, B<af31>,
B<af32>, B<af33>, B<af41>, B<af42>,
B<af43>, B<cs0>, B<cs1>, B<cs2>, B<cs3>,
B<cs4>, B<cs5>, B<cs6>, B<cs7>, B<ef>,
B<le>, B<lowdelay>, B<throughput>,
B<reliability>, a numeric value, or B<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 B<lowdelay> for
interactive sessions and B<throughput> for
non-interactive sessions. I< Optional. Type uniline.  > 

=over 4

=item upstream_default value :

af21 cs1

=back



=head2 KbdInteractiveAuthentication

Specifies whether to use
keyboard-interactive authentication. The argument to this
keyword must be B<yes> (the default) or B<no>.
B<ChallengeResponseAuthentication> is a deprecated alias
for this. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

yes

=back



=head2 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: B<bsdauth> and
B<pam>. I< Optional. Type list of uniline.  > 

=head2 KexAlgorithms

Specifies the available KEX
(Key Exchange) algorithms. Multiple algorithms must be
comma-separated. If the specified list begins with a
'+' character, then the specified methods will
be appended to the default set instead of replacing them. If
the specified list begins with a '-' character,
then the specified methods (including wildcards) will be
removed from the default set instead of replacing them. If
the specified list begins with a '^' character,
then the specified methods will be placed at the head of the
default set. The default is:

curve25519-sha256, curve25519-sha256@libssh.org,
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". I< Optional. Type uniline.  > 

=head2 KnownHostsCommand

Specifies a command to use to
obtain a list of host keys, in addition to those listed in
B<UserKnownHostsFile> and B<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 I<VERIFYING
HOST KEYS> section in L<ssh(1)>). Arguments to
B<KnownHostsCommand> accept the tokens described in the
I<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 B<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. I< Optional. Type uniline.  > 

=head2 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. Arguments to
B<LocalCommand> accept the tokens described in the
I<TOKENS> section.

The command is
run synchronously and does not have access to the session of
the L<ssh(1)> that spawned it. It should not be used for
interactive commands.

This directive
is ignored unless B<PermitLocalCommand> has been
enabled. I< Optional. Type uniline.  > 

=head2 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 specifies the listener and may be [

I<bind_address>: ]I<port> or a Unix domain
socket path. The second argument is the destination and may
be I<host>:I<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
B<GatewayPorts> setting. However, an explicit
I<bind_address> may be used to bind the connection to a
specific address. The I<bind_address> of
B<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 I<TOKENS> section and
environment variables as described in the I<ENVIRONMENT
VARIABLES> section. I< Optional. Type list of node of class L<Ssh::PortForward|Config::Model::models::Ssh::PortForward> .  > 

=head2 LogLevel

Gives the verbosity level that
is used when logging messages from L<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. I< Optional. Type enum. choice: 'QUIET', 'FATAL', 'ERROR', 'INFO', 'VERBOSE', 'DEBUG', 'DEBUG1', 'DEBUG2', 'DEBUG3'.  > 

=over 4

=item upstream_default value :

INFO

=back



=head2 LogVerbose

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 I<kex.c>, everything
in the B<kex_exchange_identification>() function, and
all code in the I<packet.c> file. This option is
intended for debugging and no overrides are enabled by
default. I< Optional. Type uniline.  > 

=head2 MACs

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:

umac-64-etm@openssh.com, umac-128-etm@openssh.com,
hmac-sha2-256-etm@openssh.com, hmac-sha2-512-etm@openssh.com,
hmac-sha1-etm@openssh.com,
umac-64@openssh.com, umac-128@openssh.com,
hmac-sha2-256, hmac-sha2-512, hmac-sha1

The list of
available MAC algorithms may also be obtained using
"ssh -Q mac". I< Optional. Type uniline.  > 

=head2 NoHostAuthenticationForLocalhost

Disable host authentication for
localhost (loopback addresses). The argument to this keyword
must be B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 NumberOfPasswordPrompts

Specifies the number of
password prompts before giving up. The argument to this
keyword must be an integer. The default is 3. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

3

=back



=head2 PasswordAuthentication

Specifies whether to use
password authentication. The argument to this keyword must
be B<yes> (the default) or B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

yes

=back



=head2 PermitLocalCommand

Allow local command execution
via the B<LocalCommand> option or using the
B<!>I<command> escape sequence in L<ssh(1)>. The
argument must be B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 PermitRemoteOpen

Specifies the destinations to
which remote TCP port forwarding is permitted when
B<RemoteForward> is used as a SOCKS proxy. The
forwarding specification must be one of the following
forms:

B<PermitRemoteOpen>I<host>:I<port> B<
PermitRemoteOpen> I<IPv4_addr>:I<port> B<
PermitRemoteOpen> I<[IPv6_addr]>:I<port>

Multiple
forwards may be specified by separating them with
whitespace. An argument of B<any> can be used to remove
all restrictions and permit any forwarding requests. An
argument of B<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. I< Optional. Type list of uniline.  > 

=head2 PKCS11Provider

Specifies which PKCS#11
provider to use or B<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 L<ssh(1)> should use to
communicate with a PKCS#11 token providing keys for user
authentication. I< Optional. Type uniline.  > 

=head2 Port

Specifies the
port number to connect on the remote host. The default is
22. I< Optional. Type uniline.  > 

=head2 PreferredAuthentications

Specifies the order in which
the client should try authentication methods. This allows a
client to prefer one method (e.g.
B<keyboard-interactive>) over another method (e.g.
B<password>). The default is:

gssapi-with-mic, hostbased, publickey,
keyboard-interactive, password. I< Optional. Type list of uniline.  > 

=head2 ProxyCommand

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
B<ProxyCommand> accept the tokens described in the
I<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
L<sshd(8)> server running on some machine, or execute B<sshd
-i> somewhere. Host key management will be done using the
B<Hostname> of the host being connected (defaulting to
the name typed by the user). Setting the command to
B<none> disables this option entirely. Note that
B<CheckHostIP> is not available for connects with a
proxy command.

This directive
is useful in conjunction with L<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. I< Optional. Type uniline.  > 

=head2 ProxyJump

Specifies one or more jump
proxies as either

[I<user>@]I<host>[:I<port>] or an ssh URI .
Multiple proxies may be separated by comma characters and
will be visited sequentially. Setting this option will cause
L<ssh(1)> to connect to the target host by first making a
L<ssh(1)> connection to the specified B<ProxyJump> host and
then establishing a TCP forwarding to the ultimate target
from there. Setting the host to B<none> disables this
option entirely.

Note that this
option will compete with the B<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. I<~/.ssh/config> should
be used if specific configuration is required for jump
hosts. I< Optional. Type list of uniline.  > 

=head2 ProxyUseFdpass

Specifies that
B<ProxyCommand> will pass a connected file descriptor
back to L<ssh(1)> instead of continuing to execute and pass
data. The default is B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 PubkeyAcceptedAlgorithms

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:

ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512, rsa-sha2-256, ssh-rsa

The list of
available signature algorithms may also be obtained using
"ssh -Q PubkeyAcceptedAlgorithms". I< Optional. Type uniline.  > 

Note: PubkeyAcceptedAlgorithms is migrated with 'C<$old>' and with: 

=over

=item *

C<$old> => C<- PubkeyAcceptedKeyTypes>

=back



=head2 PubkeyAuthentication

Specifies whether to try public
key authentication. The argument to this keyword must be
B<yes> (the default) or B<no>. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

yes

=back



=head2 RekeyLimit

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 L<sshd_config(5)>. The default value for
B<RekeyLimit> is B<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. I< Optional. Type uniline.  > 

=head2 RemoteCommand

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
B<RemoteCommand> accept the tokens described in the
I<TOKENS> section. I< Optional. Type uniline.  > 

=head2 RemoteForward

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 [

I<bind_address>: ]I<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
I<host>:I<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 B<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 I<TOKENS> section and environment
variables as described in the I<ENVIRONMENT VARIABLES>
section.

If the
I<port> argument is 0, the listen port will be
dynamically allocated on the server and reported to the
client at run time.

If the
I<bind_address> is not specified, the default is to only
bind to loopback addresses. If the I<bind_address> is
'*' or an empty string, then the forwarding is
requested to listen on all interfaces. Specifying a remote
I<bind_address> will only succeed if the server's
B<GatewayPorts> option is enabled (see
L<sshd_config(5)>). I< Optional. Type list of node of class L<Ssh::PortForward|Config::Model::models::Ssh::PortForward> .  > 

=head2 RequestTTY

Specifies whether to request a
pseudo-tty for the session. The argument may be one of:
B<no> (never request a TTY), B<yes> (always request
a TTY when standard input is a TTY), B<force> (always
request a TTY) or B<auto> (request a TTY when opening a
login session). This option mirrors the B<-t> and
B<-T> flags for L<ssh(1)>. I< Optional. Type enum. choice: 'no', 'yes', 'force', 'auto'.  > 

=head2 RevokedHostKeys

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 L<ssh-keygen(1)>. For more information on
KRLs, see the KEY REVOCATION LISTS section in
L<ssh-keygen(1)>. I< Optional. Type uniline.  > 

=head2 SecurityKeyProvider

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. I< Optional. Type uniline.  > 

=head2 SendEnv

Specifies what variables from
the local L<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 B<AcceptEnv> in L<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 B<SendEnv> directives.

See
I<PATTERNS> for more information on patterns.

It is possible
to clear previously set B<SendEnv> variable names by
prefixing patterns with I<->. The default is not to send
any environment variables. I< Optional. Type list of uniline.  > 

=head2 ServerAliveCountMax

Sets the number of server alive
messages (see below) which may be sent without L<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 B<TCPKeepAlive>
(below). The server alive messages are sent through the
encrypted channel and therefore will not be spoofable. The
TCP keepalive option enabled by B<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, B<ServerAliveInterval> (see
below) is set to 15 and B<ServerAliveCountMax> is left
at the default, if the server becomes unresponsive, ssh will
disconnect after approximately 45 seconds. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

3

=back



=head2 ServerAliveInterval

Sets a timeout interval in
seconds after which if no data has been received from the
server, L<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 B<BatchMode> option is set
(Debian-specific). B<ProtocolKeepAlives> and
B<SetupTimeOut> are Debian-specific compatibility
aliases for this option. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

0

=back



=head2 SessionType

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 B<none> (same as the B<-N> option),
B<subsystem> (same as the B<-s> option) or
B<default> (shell or command execution). I< Optional. Type enum. choice: 'none', 'subsystem', 'default'.  > 

=head2 SetEnv

Directly
specify one or more environment variables and their contents
to be sent to the server. Similarly to B<SendEnv>, with
the exception of the TERM variable, the server must be
prepared to accept the environment variable. I< Optional. Type uniline.  > 

=head2 StdinNull

Redirects stdin from
I</dev/null> (actually, prevents reading from stdin).
Either this or the equivalent B<-n> option must be used
when B<ssh> is run in the background. The argument to
this keyword must be B<yes> (same as the B<-n>
option) or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 StreamLocalBindMask

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. I< Optional. Type uniline.  > 

=head2 StreamLocalBindUnlink

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 B<StreamLocalBindUnlink> is not
enabled, B<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 B<yes> or B<no> (the default). I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

no

=back



=head2 StrictHostKeyChecking

If this flag is set to
B<yes>, L<ssh(1)> will never automatically add host keys to
the I<~/.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 I</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 I<known_hosts>
file, but will not permit connections to hosts with changed
host keys. If this flag is set to B<no> or
B<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 B<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. I< Optional. Type enum. choice: 'yes', 'accept-new', 'no', 'off', 'ask'.  > 

=over 4

=item upstream_default value :

ask

=back



=head2 SyslogFacility

Gives the facility code that is
used when logging messages from L<ssh(1)>. The possible values
are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3,
LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is USER. I< Optional. Type enum. choice: 'DAEMON', 'USER', 'AUTH', 'LOCAL0', 'LOCAL1', 'LOCAL2', 'LOCAL3', 'LOCAL4', 'LOCAL5', 'LOCAL6', 'LOCAL7'.  > 

=over 4

=item upstream_default value :

USER

=back



=head2 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. 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 B<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
B<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 B<no>.
See also B<ServerAliveInterval> for protocol-level
keepalives. I< Optional. Type boolean.  > 

=over 4

=item upstream_default value :

yes

=back



=head2 Tunnel

Request L<tun(4)>
device forwarding between the client and the server. The
argument must be B<yes>, B<point-to-point> (layer
3), B<ethernet> (layer 2), or B<no> (the default).
Specifying B<yes> requests the default tunnel mode,
which is B<point-to-point>. I< Optional. Type enum. choice: 'yes', 'point-to-point', 'ethernet', 'no'.  > 

=over 4

=item upstream_default value :

no

=back



=head2 TunnelDevice

Specifies the L<tun(4)> devices to
open on the client (I<local_tun>) and the server
(I<remote_tun>).

The argument
must be I<local_tun>[:I<remote_tun>]. The devices
may be specified by numerical ID or the keyword B<any>,
which uses the next available tunnel device. If
I<remote_tun> is not specified, it defaults to
B<any>. The default is B<any:any>. I< Optional. Type uniline.  > 

=over 4

=item upstream_default value :

any:any

=back



=head2 UpdateHostKeys

Specifies whether L<ssh(1)> should
accept notifications of additional hostkeys from the server
sent after authentication has completed and add them to
B<UserKnownHostsFile>. The argument must be B<yes>,
B<no> or B<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
B<UserKnownHostsFile> (i.e. not
B<GlobalKnownHostsFile>) and the host was authenticated
using a plain key and not a certificate.

B<UpdateHostKeys>
is enabled by default if the user has not overridden the
default B<UserKnownHostsFile> setting and has not
enabled B<VerifyHostKeyDNS>, otherwise
B<UpdateHostKeys> will be set to B<no>.

If
B<UpdateHostKeys> is set to B<ask>, then the user is
asked to confirm the modifications to the known_hosts file.
Confirmation is currently incompatible with
B<ControlPersist>, and will be disabled if it is
enabled.

Presently, only
L<sshd(8)> from OpenSSH 6.8 and greater support the
"hostkeys@openssh.com" protocol extension used to
inform the client of all the server's hostkeys. I< Optional. Type enum. choice: 'yes', 'no', 'ask'.  > 

=head2 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. I< Optional. Type uniline.  > 

=head2 UserKnownHostsFile

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
I<TOKENS> section and environment variables as described
in the I<ENVIRONMENT VARIABLES> section. The default is
I<~/.ssh/known_hosts>, I<~/.ssh/known_hosts2>. I< Optional. Type uniline.  > 

=head2 VerifyHostKeyDNS

Specifies whether to verify the
remote key using DNS and SSHFP resource records. If this
option is set to B<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 B<ask>. If this option is set to B<ask>,
information on fingerprint match will be displayed, but the
user will still need to confirm new host keys according to
the B<StrictHostKeyChecking> option. The default is
B<no>.

See also
I<VERIFYING HOST KEYS> in L<ssh(1)>. I< Optional. Type enum. choice: 'yes', 'ask', 'no'.  > 

=over 4

=item upstream_default value :

no

=back



=head2 VisualHostKey

If this flag is set to
B<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 B<no> (the default), no fingerprint strings are
printed at login and only the fingerprint string will be
printed for unknown host keys. I< Optional. Type uniline.  > 

=over 4

=item upstream_default value :

no

=back



=head2 XAuthLocation

Specifies the full pathname of
the L<xauth(1)> program. The default is
I</usr/bin/xauth>. I< Optional. Type uniline.  > 

=over 4

=item upstream_default value :

/usr/bin/xauth

=back



=head2 FallBackToRsh

This parameter is now ignored by Ssh. B<Deprecated> I< Optional. Type uniline.  > 

=head2 HostbasedKeyTypes

This parameter is now ignored by Ssh. B<Deprecated> I< Optional. Type uniline.  > 

=head2 PubkeyAcceptedKeyTypes

This parameter is now ignored by Ssh. B<Deprecated> I< Optional. Type uniline.  > 

=head2 UseRsh

This parameter is now ignored by Ssh. B<Deprecated> I< Optional. Type uniline.  > 

=head2 Match

Restricts the
following declarations (up to the next B<Host> or
B<Match> keyword) to be used only when the conditions
following the B<Match> keyword are satisfied. Match
conditions are specified using one or more criteria or the
single token B<all> which always matches. The available
criteria keywords are: B<canonical>, B<final>,
B<exec>, B<host>, B<originalhost>, B<user>,
and B<localuser>. The B<all> criteria must appear
alone or immediately after B<canonical> or B<final>.
Other criteria may be combined arbitrarily. All criteria but
B<all>, B<canonical>, and B<final> require an
argument. Criteria may be negated by prepending an
exclamation mark ('!').

The
B<canonical> keyword matches only when the configuration
file is being re-parsed after hostname canonicalization (see
the B<CanonicalizeHostname> option). This may be useful
to specify conditions that work with canonical host names
only.

The
B<final> keyword requests that the configuration be
re-parsed (regardless of whether B<CanonicalizeHostname>
is enabled), and matches only during this final pass. If
B<CanonicalizeHostname> is enabled, then
B<canonical> and B<final> match during the same
pass.

The B<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 B<exec> accept the tokens described in the
I<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 I<PATTERNS> section. The
criteria for the B<host> keyword are matched against the
target hostname, after any substitution by the
B<Hostname> or B<CanonicalizeHostname> options. The
B<originalhost> keyword matches against the hostname as
it was specified on the command-line. The B<user>
keyword matches against the target username on the remote
host. The B<localuser> keyword matches against the name
of the local user running L<ssh(1)> (this keyword may be useful
in system-wide B<ssh_config> files). I< Optional. Type hash of node of class L<Ssh::HostElement|Config::Model::models::Ssh::HostElement> .  > 

=head1 SEE ALSO

=over

=item *

L<cme>

=item *

L<Config::Model::models::Ssh::HostElement>

=item *

L<Config::Model::models::Ssh::PortForward>

=back

=head1 AUTHOR

=over

=item Dominique Dumont


=back

=head1 COPYRIGHT

=over

=item 2013 Dominique Dumont


=back

=head1 LICENSE

=over

=item LGPL2


=back

=cut