Provided by: libconfig-model-openssh-perl_2.9.0.2-1_all 
NAME
Config::Model::models::Ssh::HostElement - Configuration class Ssh::HostElement
DESCRIPTION
Configuration classes used by Config::Model
This configuration class was generated from ssh_system documentation. by parse-man.pl
<https://github.com/dod38fr/config-model-openssh/contrib/parse-man.pl>
Elements
AddKeysToAgent
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
AddressFamily
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
BatchMode
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
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. Optional. Type uniline.
BindInterface
Use the address of the specified interface on the local machine as the source address of
the connection. Optional. Type uniline.
CanonicalDomains
When CanonicalizeHostname is enabled, this option specifies the list of domain suffixes in
which to search for the specified destination host. Optional. Type uniline.
CanonicalizeFallbackLocal
Specifies whether to fail with an error when hostname canonicalization fails. The default,
yes, will attempt to look up the unqualified hostname using the system resolver's search
rules. A value of no will cause ssh(1) to fail instantly if CanonicalizeHostname is
enabled and the target hostname cannot be found in any of the domains specified by
CanonicalDomains. Optional. Type boolean.
upstream_default value :
yes
CanonicalizeHostname
Controls whether explicit hostname canonicalization is performed. The default, no, is not
to perform any name rewriting and let the system resolver handle all hostname lookups. If
set to yes then, for connections that do not use a ProxyCommand 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
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). Optional. Type
integer.
upstream_default value :
1
CanonicalizePermittedCNAMEs
Specifies rules to determine whether CNAMEs should be followed when canonicalizing
hostnames. The rules consist of one or more arguments of
source_domain_list:target_domain_list, where source_domain_list is a pattern-list of
domains that may follow CNAMEs in canonicalization, and target_domain_list is a pattern-
list of domains that they may resolve to.
For example, "*.a.example.com:*.b.example.com,*.c.example.com" will allow hostnames
matching "*.a.example.com" to be canonicalized to names in the "*.b.example.com" or
"*.c.example.com" domains.
A single argument of "none" causes no CNAMEs to be considered for canonicalization. This
is the default behaviour. Optional. Type uniline.
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.
ssh(1) will not accept host certificates signed using algorithms other than those
specified. Optional. Type uniline.
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 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.
CheckHostIP
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
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". Optional. Type
uniline.
ClearAllForwardings
Specifies that all local, remote, and dynamic port forwardings specified in the
configuration files or on the command line be cleared. This option is primarily useful
when used from the ssh(1) command line to clear port forwardings set in configuration
files, and is automatically set by scp(1) and sftp(1). The argument must be yes or no (the
default). Optional. Type boolean.
upstream_default value :
no
Compression
Specifies whether to use compression. The argument must be yes or no (the default).
Optional. Type boolean.
upstream_default value :
no
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. Optional. Type integer.
upstream_default value :
1
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.
Optional. Type integer.
ControlMaster
Enables the sharing of multiple sessions over a single network connection. When set to
yes, ssh(1) will listen for connections on a control socket specified using the
ControlPath argument. Additional sessions can connect to this socket using the same
ControlPath with ControlMaster set to no (the default). These sessions will try to reuse
the master instance's network connection rather than initiating new ones, but will fall
back to connecting normally if the control socket does not exist, or is not listening.
Setting this to ask will cause ssh(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
ControlPath
Specify the path to the control socket used for connection sharing as described in the
ControlMaster section above or the string none to disable connection sharing. 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.
ControlPersist
When used in conjunction with ControlMaster, specifies that the master connection should
remain open in the background (waiting for future client connections) after the initial
client connection has been closed. If set to no (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.
DynamicForward
Specifies that a TCP port on the local machine be forwarded over the secure channel, and
the application protocol is then used to determine where to connect to from the remote
machine.
The argument must be [
bind_address: ]port. IPv6 addresses can be specified by enclosing addresses in square
brackets. By default, the local port is bound in accordance with the GatewayPorts setting.
However, an explicit bind_address may be used to bind the connection to a specific
address. The bind_address of localhost indicates that the listening port be bound for
local use only, while an empty address or '*' indicates that the port should be available
from all interfaces.
Currently the SOCKS4 and SOCKS5 protocols are supported, and ssh(1) will act as a SOCKS
server. Multiple forwardings may be specified, and additional forwardings can be given on
the command line. Only the superuser can forward privileged ports. Optional. Type list of
uniline.
EnableSSHKeysign
Setting this option to yes in the global client configuration file /etc/ssh/ssh_config
enables the use of the helper program ssh-keysign(8) during HostbasedAuthentication. The
argument must be yes or no (the default). This option should be placed in the non-
hostspecific section. See ssh-keysign(8) for more information. Optional. Type boolean.
upstream_default value :
no
EscapeChar
Sets the escape character (default: '~'). The escape character can also be set on the
command line. The argument should be a single character, '^' followed by a letter, or none
to disable the escape character entirely (making the connection transparent for binary
data). Optional. Type uniline.
ExitOnForwardFailure
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
FingerprintHash
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
ForkAfterAuthentication
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
ForwardAgent
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
ForwardX11
Specifies whether X11 connections will be automatically redirected over the secure channel
and DISPLAY set. The argument must be yes or no (the default).
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
ForwardX11Timeout
Specify a timeout for untrusted X11 forwarding using the format described in the TIME
FORMATS section of sshd_config(5). X11 connections received by ssh(1) after this time will
be refused. 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.
ForwardX11Trusted
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.
GatewayPorts
Specifies whether remote hosts are allowed to connect to local forwarded ports. By
default, ssh(1) binds local port forwardings to the loopback address. This prevents other
remote hosts from connecting to forwarded ports. GatewayPorts can be used to specify that
ssh should bind local port forwardings to the wildcard address, thus allowing remote hosts
to connect to forwarded ports. The argument must be yes or no (the default). Optional.
Type boolean.
upstream_default value :
no
GlobalKnownHostsFile
Specifies one or more files to use for the global host key database, separated by
whitespace. The default is /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2. Optional.
Type uniline.
upstream_default value :
/etc/ssh/ssh_known_hosts
GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed. The default is no.
Optional. Type boolean.
upstream_default value :
no
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.
Optional. Type uniline.
GSSAPIDelegateCredentials
Forward (delegate) credentials to the server. The default is no. Optional. Type boolean.
upstream_default value :
no
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 no. Optional. Type boolean.
upstream_default value :
no
GSSAPIRenewalForcesRekey
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
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. Optional. Type uniline.
GSSAPITrustDns
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
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 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.
HashKnownHosts
Indicates that ssh(1) should hash host names and addresses when they are added to
~/.ssh/known_hosts. These hashed names may be used normally by ssh(1) and sshd(8), but
they do not 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
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-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
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"
HostbasedAuthentication
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
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-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
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.
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. Optional. Type uniline.
Hostname
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.
IdentitiesOnly
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
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 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.
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
~/.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.
IgnoreUnknown
Specifies a pattern-list of unknown options to be ignored if they are encountered in
configuration parsing. This may be used to suppress errors if ssh_config contains options
that are unrecognised by ssh(1). It is recommended that IgnoreUnknown be listed early in
the configuration file as it will not be applied to unknown options that appear before it.
Optional. Type uniline.
Include
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.
IPQoS
Specifies the IPv4 type-of-service or DSCP class for connections. Accepted values are
af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43, cs0, cs1, cs2,
cs3, cs4, cs5, cs6, cs7, ef, 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
KbdInteractiveAuthentication
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
KbdInteractiveDevices
Specifies the list of methods to use in keyboard-interactive authentication. Multiple
method names must be comma-separated. The default is to use the server specified list. The
methods available vary depending on what the server supports. For an OpenSSH server, it
may be zero or more of: bsdauth and pam. Optional. Type list of uniline.
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
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:
sntrup761x25519-sha512@openssh.com, 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".
Optional. Type uniline.
KnownHostsCommand
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.
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 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.
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 [
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 .
LogLevel
Gives the verbosity level that is used when logging messages from ssh(1). The possible
values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The
default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher
levels of verbose output. Optional. Type enum. choice: 'QUIET', 'FATAL', 'ERROR', 'INFO',
'VERBOSE', 'DEBUG', 'DEBUG1', 'DEBUG2', 'DEBUG3'.
upstream_default value :
INFO
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 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.
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". Optional.
Type uniline.
NoHostAuthenticationForLocalhost
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
NumberOfPasswordPrompts
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
PasswordAuthentication
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
PermitLocalCommand
Allow local command execution via the LocalCommand option or using the !command escape
sequence in ssh(1). The argument must be yes or no (the default). Optional. Type boolean.
upstream_default value :
no
PermitRemoteOpen
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.
PKCS11Provider
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.
Port
Specifies the port number to connect on the remote host. The default is 22. Optional.
Type uniline.
PreferredAuthentications
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.
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 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.
ProxyJump
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.
ProxyUseFdpass
Specifies that ProxyCommand will pass a connected file descriptor back to ssh(1) instead
of continuing to execute and pass data. The default is no. Optional. Type boolean.
upstream_default value :
no
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-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
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"
PubkeyAuthentication
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
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 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.
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 RemoteCommand accept the tokens described in the TOKENS section.
Optional. Type uniline.
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 [
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 .
RequestTTY
Specifies whether to request a pseudo-tty for the session. The argument may be one of: no
(never request a TTY), yes (always request a TTY when standard input is a TTY), force
(always request a TTY) or auto (request a TTY when opening a login session). This option
mirrors the -t and -T flags for ssh(1). Optional. Type enum. choice: 'no', 'yes',
'force', 'auto'.
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 ssh-keygen(1). For more information on KRLs, see the KEY REVOCATION LISTS section in
ssh-keygen(1). Optional. Type uniline.
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. Optional. Type uniline.
SendEnv
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.
ServerAliveCountMax
Sets the number of server alive messages (see below) which may be sent without ssh(1)
receiving any messages back from the server. If this threshold is reached while server
alive messages are being sent, ssh will disconnect from the server, terminating the
session. It is important to note that the use of server alive messages is very different
from TCPKeepAlive (below). The server alive messages are sent through the encrypted
channel and therefore will not be spoofable. The TCP keepalive option enabled by
TCPKeepAlive is spoofable. The server alive mechanism is valuable when the client or
server depend on knowing when a connection has become 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
ServerAliveInterval
Sets a timeout interval in seconds after which if no data has been received from the
server, ssh(1) will send a message through the encrypted channel to request a response
from the server. The default is 0, indicating that these messages will not be sent to the
server, 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
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 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'.
SetEnv
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.
StdinNull
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
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. Optional. Type uniline.
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
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
StrictHostKeyChecking
If this flag is set to yes, ssh(1) will never automatically add host keys to the
~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This
provides maximum protection against 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
SyslogFacility
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
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
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
Tunnel
Request tun(4) device forwarding between the client and the server. The argument must be
yes, point-to-point (layer 3), ethernet (layer 2), or no (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
TunnelDevice
Specifies the tun(4) devices to open on the client (local_tun) and the server
(remote_tun).
The argument must be local_tun[:remote_tun]. The devices may be specified by numerical ID
or the keyword any, which uses the next available tunnel device. If remote_tun is not
specified, it defaults to any. The default is any:any. Optional. Type uniline.
upstream_default value :
any:any
UpdateHostKeys
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 "hostkeys@openssh.com"
protocol extension used to inform the client of all the server's hostkeys. Optional. Type
enum. choice: 'yes', 'no', 'ask'.
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. Optional. Type uniline.
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 TOKENS section and environment variables as described in the
ENVIRONMENT VARIABLES section. The default is ~/.ssh/known_hosts, ~/.ssh/known_hosts2.
Optional. Type uniline.
VerifyHostKeyDNS
Specifies whether to verify the remote key using DNS and SSHFP resource records. If this
option is set to yes, the client will implicitly trust keys that match a secure
fingerprint from DNS. Insecure fingerprints will be handled as if this option was set to
ask. If this option is set to ask, information on fingerprint match will be displayed, but
the user will still need to confirm new host keys according to the StrictHostKeyChecking
option. The default is no.
See also VERIFYING HOST KEYS in ssh(1). Optional. Type enum. choice: 'yes', 'ask', 'no'.
upstream_default value :
no
VisualHostKey
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
XAuthLocation
Specifies the full pathname of the xauth(1) program. The default is /usr/bin/xauth.
Optional. Type uniline.
upstream_default value :
/usr/bin/xauth
FallBackToRsh
This parameter is now ignored by Ssh. Deprecated Optional. Type uniline.
HostbasedKeyTypes
This parameter is now ignored by Ssh. Deprecated Optional. Type uniline.
PubkeyAcceptedKeyTypes
This parameter is now ignored by Ssh. Deprecated Optional. Type uniline.
UseRsh
This parameter is now ignored by Ssh. Deprecated Optional. Type uniline.
SEE ALSO
• cme
• Config::Model::models::Ssh::PortForward
LICENSE
LGPL2
perl v5.34.0 2022-08-0Config::Model::models::Ssh::HostElement(3pm)