focal (3) Config::Model::models::SystemSsh.3pm.gz
NAME
Config::Model::models::SystemSsh - Configuration class SystemSsh
DESCRIPTION
Configuration classes used by Config::Model
Configuration class used by Config::Model to edit or validate /etc/ssh/ssh_config (as root)
Elements
Host
Restricts the following declarations (up to the next Host or Match keyword) to be only for those hosts
that match one of the patterns given after the keyword. If more than one pattern is provided, they should
be separated by whitespace. A single '*' as a pattern can be used to provide global defaults for all
hosts. The host is usually the hostname argument given on the command line (see the CanonicalizeHostname
keyword for exceptions).
A pattern entry may be negated by prefixing it with an exclamation mark ('!'). If a negated entry is
matched, then the Host entry is ignored, regardless of whether any other patterns on the line match.
Negated matches are therefore useful to provide exceptions for wildcard matches.
See PATTERNS for more information on patterns. Optional. Type hash of node of class Ssh::HostElement .
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. The argument must be yes, confirm, ask, or no (the default).
Optional. Type enum. choice: 'yes', 'confirm', 'ask', 'no'.
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, passphrase/password querying 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 supply the password, 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. Optional. Type enum. choice: 'no',
'yes', 'always'.
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.
Optional. Type uniline.
CASignatureAlgorithms
Specifies which algorithms are allowed for signing of certificates by certificate authorities (CAs). The
default is:
ecdsa-sha2-nistp256.ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
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.
Arguments to CertificateFile 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 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.
ChallengeResponseAuthentication
Specifies whether to use challenge-response authentication. The argument to this keyword must be yes (the
default) or no. Optional. Type boolean.
upstream_default value :
yes
CheckHostIP
If set to yes (the default), 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 check will not be executed. Optional. Type boolean.
upstream_default value :
yes
Ciphers
Specifies the ciphers allowed and their order of preference. Multiple ciphers must be comma-separated. If
the specified value begins with a '+' character, then the specified ciphers will be appended to the
default set instead of replacing them. If the specified value begins with a '-' character, then the
specified ciphers (including wildcards) will be removed from the default set instead of replacing them.
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 value is used only when the target is down or really unreachable, not when it
refuses the connection. 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 or the tokens described in the TOKENS 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, 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
ForwardAgent
Specifies whether the connection to the authentication agent (if any) will be forwarded to the remote
machine. The argument must be yes or no (the default).
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-gex-sha1-,gss-group14-sha1-X. This option only applies to protocol version 2
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 reveal identifying
information should the file's contents be disclosed. The default is no. Note that existing names and
addresses in known hosts files will not be converted automatically, but may be manually hashed using
ssh-keygen(1). 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
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
HostbasedKeyTypes
Specifies the key types that will be used for hostbased authentication as a comma-separated list of
patterns. Alternately if the specified value begins with a '+' character, then the specified key types
will be appended to the default set instead of replacing them. If the specified value begins with a '-'
character, then the specified key types (including wildcards) will be removed from the default set
instead of replacing them. The default for this option is:
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com,
ssh-ed25519-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
The -Q option of ssh(1) may be used to list supported key types. Optional. Type uniline.
HostKeyAlgorithms
Specifies the host key algorithms that the client wants to use in order of preference. Alternately if the
specified value begins with a '+' character, then the specified key types will be appended to the default
set instead of replacing them. If the specified value begins with a '-' character, then the specified key
types (including wildcards) will be removed from the default set instead of replacing them. The default
for this option is:
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com,
ssh-ed25519-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
ssh-ed25519,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 key types may also be obtained using "ssh -Q key". 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 authentication identity and certificate files explicitly
configured in the ssh_config files or passed on the ssh(1) command-line, even if ssh-agent(1) or a
PKCS11Provider 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 or the tokens
described in the TOKENS section. Optional. Type uniline.
IdentityFile
Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA authentication identity is read. The
default is ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519 and ~/.ssh/id_rsa. 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. 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,
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. 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.
Alternately if the specified value begins with a '+' character, then the specified methods will be
appended to the default set instead of replacing them. If the specified value begins with a '-'
character, then the specified methods (including wildcards) will be removed from the default set instead
of replacing them. 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, diffie-hellman-group14-sha1
The list of available key exchange algorithms may also be obtained using "ssh -Q kex". 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 must be [
bind_address: ]port and the second argument must be host:hostport. IPv6 addresses can be specified by
enclosing addresses in square brackets. Multiple forwardings may be specified, and additional
forwardings can be given on the command line. Only the superuser can forward privileged ports. By
default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit
bind_address may be used to bind the connection to a specific address. The bind_address of localhost
indicates that the listening port be bound for local use only, while an empty address or '*' indicates
that the port should be available from all interfaces. 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
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 value
begins with a '+' character, then the specified algorithms will be appended to the default set instead of
replacing them. If the specified value begins with a '-' character, then the specified algorithms
(including wildcards) will be removed from the default set instead of replacing them.
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
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.
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
PubkeyAcceptedKeyTypes
Specifies the key types that will be used for public key authentication as a comma-separated list of
patterns. Alternately if the specified value begins with a '+' character, then the key types after it
will be appended to the default instead of replacing it. If the specified value begins with a '-'
character, then the specified key types (including wildcards) will be removed from the default set
instead of replacing them. The default for this option is:
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com,
ssh-ed25519-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
The list of available key types may also be obtained using "ssh -Q key". Optional. Type uniline.
PubkeyAuthentication
Specifies whether to try public key authentication. The argument to this keyword must be yes (the
default) or no. Optional. Type boolean.
upstream_default value :
yes
RekeyLimit
Specifies the maximum amount of data that may be transmitted before the session key is renegotiated,
optionally followed a maximum amount of time that may pass before the session key is renegotiated. The
first argument is specified in bytes and may have a suffix of 'K', 'M', or 'G' to indicate Kilobytes,
Megabytes, or Gigabytes, respectively. The default is between '1G' and '4G', depending on the cipher.
The optional second value is specified in seconds and may use any of the units documented in the TIME
FORMATS section of sshd_config(5). The default value for RekeyLimit is default none, which means that
rekeying is performed after the cipher's default amount of data has been sent or received and no time
based rekeying is done. 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 must be [
bind_address: ]port If forwarding to a specific destination then the second argument must be
host:hostport, otherwise if no destination argument is specified then the remote forwarding will be
established as a SOCKS proxy.
IPv6 addresses can be specified by enclosing addresses in square brackets. Multiple forwardings may be
specified, and additional forwardings can be given on the command line. Privileged ports can be forwarded
only when logging in as root on the remote machine.
If the port argument is 0, the listen port will be dynamically allocated on the server and reported to
the client at run time.
If the bind_address is not specified, the default is to only bind to loopback addresses. If the
bind_address is '*' or an empty string, then the forwarding is requested to listen on all interfaces.
Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see
sshd_config(5)). 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.
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 inactive.
The default value is 3. If, for example, ServerAliveInterval (see below) is set to 15 and
ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after
approximately 45 seconds. 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
SetEnv
Directly specify one or more environment variables and their contents to be sent to the server. Similarly
to SendEnv, the server must be prepared to accept the environment variable. Optional. Type uniline.
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 Xaccept-newX then ssh will automatically add new host keys to the user known hosts
files, 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 (the
default) or ask. Enabling 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. 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'.
upstream_default value :
no
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. 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.
UseRsh
This parameter is now ignored by Ssh. Deprecated Optional. Type uniline.
Match
Restricts the following declarations (up to the next Host or Match keyword) to be used only when the
conditions following the Match keyword are satisfied. Match conditions are specified using one or more
criteria or the single token all which always matches. The available criteria keywords are: canonical,
final, exec, host, originalhost, user, and localuser. The all criteria must appear alone or immediately
after canonical or final. Other criteria may be combined arbitrarily. All criteria but all, canonical,
and final require an argument. Criteria may be negated by prepending an exclamation mark ('!').
The canonical keyword matches only when the configuration file is being re-parsed after hostname
canonicalization (see the CanonicalizeHostname option). This may be useful to specify conditions that
work with canonical host names only.
The final keyword requests that the configuration be re-parsed (regardless of whether
CanonicalizeHostname is enabled), and matches only during this final pass. If CanonicalizeHostname is
enabled, then canonical and final match during the same pass.
The exec keyword executes the specified command under the user's shell. If the command returns a zero
exit status then the condition is considered true. Commands containing whitespace characters must be
quoted. Arguments to exec accept the tokens described in the TOKENS section.
The other keywords' criteria must be single entries or comma-separated lists and may use the wildcard and
negation operators described in the PATTERNS section. The criteria for the host keyword are matched
against the target hostname, after any substitution by the Hostname or CanonicalizeHostname options. The
originalhost keyword matches against the hostname as it was specified on the command-line. The user
keyword matches against the target username on the remote host. The localuser keyword matches against the
name of the local user running ssh(1) (this keyword may be useful in system-wide ssh_config files).
Optional. Type hash of node of class Ssh::HostElement .
SEE ALSO
• cme
• Config::Model::models::Ssh::HostElement
• Config::Model::models::Ssh::PortForward
AUTHOR
Dominique Dumont
COPYRIGHT
2013 Dominique Dumont
LICENSE
LGPL2