Provided by: libconfig-model-openssh-perl_1.237-1_all 
NAME
Config::Model::models::Sshd::MatchElement - Configuration class Sshd::MatchElement
DESCRIPTION
Configuration classes used by Config::Model
Configuration class that represents all parameters available inside a Match block of a sshd
configuration.
Elements
AcceptEnv
Specifies what environment variables sent by the client will be copied into the session's
environ(7).Optional. Type list of uniline.
AllowAgentForwarding
Specifies whether ssh-agent(1) forwarding is permitted. Note that disabling agent forwarding does not
improve security unless users are also denied shell access, as they can always install their own
forwarders.Optional. Type boolean. upstream_default: '1'.
AllowGroups
Login is allowed only for users whose primary group or supplementary group list matches one of the
patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is
allowed for all groups. The allow/deny directives are processed in the following order: DenyUsers,
AllowUsers, DenyGroups, and finally AllowGroups.Optional. Type list of uniline.
AllowUsers
List of user name patterns, separated by spaces. If specified, login is allowed only for user names that
match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default,
login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately
checked, restricting logins to particular users from particular hosts. The allow/deny directives are
processed in the following order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.Optional.
Type list of uniline.
AuthenticationMethods - authentication methods that must be successfully completed for a user to be granted
access
Specifies the authentication methods that must be successfully completed for a user to be granted access.
This option must be followed by one or more comma-separated lists of authentication method names.
Successful authentication requires completion of every method in at least one of these lists.
For example, an argument of "publickey,password publickey,keyboard-interactive" would require the user to
complete public key authentication, followed by either password or keyboard interactive authentication.
Only methods that are next in one or more lists are offered at each stage, so for this example, it would
not be possible to attempt password or keyboard-interactive authentication before public key.
For keyboard interactive authentication it is also possible to restrict authentication to a specific
device by appending a colon followed by the device identifier "bsdauth", "pam", or "skey", depending on
the server configuration. For example, "keyboard-interactive:bsdauth" would restrict keyboard interactive
authentication to the "bsdauth" device.
This option is only available for SSH protocol 2 and will yield a fatal error if enabled if protocol 1 is
also enabled. Note that each authentication method listed should also be explicitly enabled in the
configuration. The default is not to require multiple authentication; successful completion of a single
authentication method is sufficient.Optional. Type uniline.
AuthorizedKeysCommand - program to be used to look up the user's public keys
Specifies a program to be used to look up the user's public keys. The program must be owned by root and
not writable by group or others. It will be invoked with a single argument of the username being
authenticated, and should produce on standard output zero or more lines of authorized_keys output (see
AUTHORIZED_KEYS in sshd(8)). If a key supplied by AuthorizedKeysCommand does not successfully
authenticate and authorize the user then public key authentication continues using the usual
AuthorizedKeysFile files. By default, no AuthorizedKeysCommand is run.Optional. Type uniline.
AuthorizedKeysCommandUser - user under whose account the AuthorizedKeysCommand is run
Specifies the user under whose account the AuthorizedKeysCommand is run. It is recommended to use a
dedicated user that has no other role on the host than running authorized keys commands.Optional. Type
uniline.
AllowTcpForwarding
Specifies whether TCP forwarding is permitted. The default is "yes".Note that disabling TCP forwarding
does not improve security unless users are also denied shell access, as they can always install their own
forwarders.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'yes'.
AuthorizedKeysFile2
Specifies the file that contains the public keys that can be used for user authentication.
AuthorizedKeysFile may contain tokens of the form %T which are substituted during connection
setup.Deprecated Optional. Type list of uniline.
AuthorizedKeysFile
Specifies the file that contains the public keys that can be used for user authentication. The format is
described in the AUTHORIZED_KEYS FILE FORMAT section of sshd(8). AuthorizedKeysFile may contain tokens of
the form %T which are substituted during connection setup. The following tokens are defined: %% is
replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u
is replaced by the username of that user. After expansion, AuthorizedKeysFile is taken to be an absolute
path or one relative to the user's home directory. Multiple files may be listed, separated by whitespace.
The default is ".ssh/authorized_keys .ssh/authorized_keys2".Optional. Type list of uniline.
Note: AuthorizedKeysFile values are migrated from '- AuthorizedKeysFile2'
AuthorizedPrincipalsFile - file that lists principal names that are accepted for certificate authentication
Specifies a file that lists principal names that are accepted for certificate authentication. When using
certificates signed by a key listed in TrustedUserCAKeys, this file lists names, one of which must appear
in the certificate for it to be accepted for authentication. Names are listed one per line preceded by
key options (as described in AUTHORIZED_KEYS FILE FORMAT in sshd(8)). Empty lines and comments starting
with '#' are ignored.
AuthorizedPrincipalsFile may contain tokens of the form %T which are substituted during connection setup.
The following tokens are defined: %% is replaced by a literal '%', %h is replaced by the home directory
of the user being authenticated, and %u is replaced by the username of that user. After expansion,
AuthorizedPrincipalsFile is taken to be an absolute path or one relative to the user's home directory.
The default is "none", i.e. not to use a principals file - in this case, the username of the user must
appear in a certificate's principals list for it to be accepted. Note that AuthorizedPrincipalsFile is
only used when authentication proceeds using a CA listed in TrustedUserCAKeys and is not consulted for
certification authorities trusted via ~/.ssh/authorized_keys, though the principals= key option offers a
similar facility (see sshd(8) for details).Optional. Type uniline.
Banner
In some jurisdictions, sending a warning message before authentication may be relevant for getting legal
protection. The contents of the specified file are sent to the remote user before authentication is
allowed. This option is only available for protocol version 2. By default, no banner is
displayed.Optional. Type uniline.
ChrootDirectory - pathname of a directory to chroot to after authentication
Specifies the pathname of a directory to chroot(2) to after authentication. All components of the
pathname must be root owned directories that are not writable by any other user or group. After the
chroot, sshd(8) changes the working directory to the user's home directory.
The pathname may contain the following tokens that are expanded at runtime once the connecting user has
been authenticated: %% is replaced by a literal '%', %h is replaced by the home directory of the user
being authenticated, and %u is replaced by the username of that user.
The ChrootDirectory must contain the necessary files and directories to support the user's session. For
an interactive session this requires at least a shell, typically sh(1), and basic /dev nodes such as
null(4), zero(4), stdin(4), stdout(4), stderr(4), arandom(4) and tty(4) devices. For file transfer
sessions using "sftp", no additional configuration of the environment is necessary if the in-process sftp
server is used, though sessions which use logging do require /dev/log inside the chroot directory (see
sftp-server(8) for details).
The default is not to chroot(2).Optional. Type uniline.
DenyGroups
This keyword can be followed by a list of group name patterns, separated by spaces. Login is disallowed
for users whose primary group or supplementary group list matches one of the patterns. Only group names
are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The
allow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and
finally AllowGroups.Optional. Type list of uniline.
DenyUSers
This keyword can be followed by a list of user name patterns, separated by spaces. Login is disallowed
for user names that match one of the patterns. Only user names are valid; a numerical user ID is not
recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER
and HOST are separately checked, restricting logins to particular users from particular hosts. The
allow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and
finally AllowGroups.Optional. Type list of uniline.
ForceCommand
Forces the execution of the command specified by ForceCommand, ignoring any command supplied by the
client. The command is invoked by using the user's login shell with the -c option. This applies to shell,
command, or subsystem execution. It is most useful inside a Match block. The command originally supplied
by the client is available in the SSH_ORIGINAL_COMMAND environment variable.Optional. Type uniline.
GatewayPorts
Specifies whether remote hosts are allowed to connect to ports forwarded for the client. By default,
sshd(8) binds remote port forwardings to the loopback address. This prevents other remote hosts from
connecting to forwarded ports. GatewayPorts can be used to specify that sshd should allow remote port
forwardings to bind to non-loopback addresses, thus allowing other hosts to connect.Optional. Type enum.
choice: 'yes', 'clientspecified', 'no'. upstream_default: 'no'.
Here are some explanations on the possible values:
'clientspecified'
allow the client to select the address to which the forwarding is bound
'no'
No port forwarding
'yes'
force remote port forwardings to bind to the wildcard address
GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed. Note that this option applies to
protocol version 2 only.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.
HostbasedAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication together with successful public key client
host authentication is allowed (host-based authentication). This option is similar to
RhostsRSAAuthentication and applies to protocol version 2 only.Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'no'.
HostbasedUsesNameFromPacketOnly
Specifies whether or not the server will attempt to perform a reverse name lookup when matching the name
in the ~/.shosts, ~/.rhosts, and /etc/hosts.equiv files during HostbasedAuthentication.Optional. Type
enum. choice: 'no', 'yes'. upstream_default: 'no'.
Here are some explanations on the possible values:
'no'
sshd(8) attempts to resolve the name from the TCP connection itself.
'yes'
sshd(8) uses the name supplied by the client
KbdInteractiveAuthentication
No doc found in sshd documentation. Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.
KerberosAuthentication
Specifies whether the password provided by the user for PasswordAuthentication will be validated through
the Kerberos KDC. To use this option, the server needs a Kerberos servtab which allows the verification
of the KDC's identity. The default is "no".Optional. Type enum. choice: 'no', 'yes'. upstream_default:
'no'.
MaxAuthTries
Specifies the maximum number of authentication attempts permitted per connection. Once the number of
failures reaches half this value, additional failures are logged.Optional. Type integer.
upstream_default: '6'.
MaxSessions - Specifies the maximum number of open sessions permitted per network connection
Optional. Type integer. upstream_default: '10'.
PasswordAuthentication
Specifies whether password authentication is allowed.Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'yes'.
PermitEmptyPasswords
When password authentication is allowed, it specifies whether the server allows login to accounts with
empty password strings. The default is "no".Optional. Type enum. choice: 'no', 'yes'. upstream_default:
'no'.
Here are some explanations on the possible values:
'yes'
So, you want your machine to be part of a botnet ? ;-)
PermitOpen
Specifies the destinations to which TCP port forwarding is permitted. The forwarding specification must
be one of the following forms: "host:port" or "IPv4_addr:port" or "[IPv6_addr]:port". An argument of
"any" can be used to remove all restrictions and permit any forwarding requests. By default all port
forwarding requests are permitted.Optional. Type list of uniline.
PermitRootLogin
Specifies whether root can log in using ssh(1).Optional. Type enum. choice: 'yes', 'without-password',
'forced-commands-only', 'no'. upstream_default: 'yes'.
Here are some explanations on the possible values:
'forced-commands-only'
root login with public key authentication will be allowed, but only if the command option has been
specified (which may be useful for taking remote backups even if root login is normally not allowed).
All other authentication methods are disabled for root.
'no'
root is not allowed to log in
'without-password'
password authentication is disabled for root
PermitTunnel
Specifies whether tun(4) device forwarding is allowed. The argument must be "yes", "point-to-point"
(layer 3), "ethernet" (layer 2), or "no". Specifying "yes" permits both "point-to-point" and
"ethernet".Optional. Type enum. choice: 'yes', 'point-to-point', 'ethernet', 'no'. upstream_default:
'no'.
Here are some explanations on the possible values:
'yes'
permits both "point-to-point" and "ethernet"
PubkeyAuthentication
Specifies whether public key authentication is allowed. The default is "yes". Note that this option
applies to protocol version 2 only.Optional. Type enum. choice: 'no', 'yes'. upstream_default: '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. The default value for RekeyLimit is "default none", which means that rekeying is
performed after the cipher's default amount of data has been sent or received and no time based rekeying
is done. This option applies to protocol version 2 only.Optional. Type uniline. upstream_default:
'default none'.
RhostsRSAAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication together with successful RSA host
authentication is allowed. The default is "no". This option applies to protocol version 1 only.Optional.
Type enum. choice: 'no', 'yes'. upstream_default: 'no'.
RSAAuthentication
Specifies whether pure RSA authentication is allowed. This option applies to protocol version 1
only.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'yes'.
X11DisplayOffset
Specifies the first display number available for sshd(8)'s X11 forwarding. This prevents sshd from
interfering with real X11 servers.Optional. Type integer. upstream_default: '10'.
X11Forwarding
Specifies whether X11 forwarding is permitted. Note that disabling X11 forwarding does not prevent users
from forwarding X11 traffic, as users can always install their own forwarders. X11 forwarding is
automatically disabled if UseLogin is enabled.Optional. Type enum. choice: 'yes', 'no'. upstream_default:
'no'.
X11UseLocalhost
Specifies whether sshd(8) should bind the X11 forwarding server to the loopback address or to the
wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the
hostname part of the DISPLAY environment variable to "localhost". This prevents remote hosts from
connecting to the proxy display. However, some older X11 clients may not function with this
configuration. X11UseLocalhost may be set to "no" to specify that the forwarding server should be bound
to the wildcard address.Optional. Type enum. choice: 'yes', 'no'. upstream_default: 'yes'.
SEE ALSO
• cme
AUTHOR
Dominique Dumont
COPYRIGHT
2009-2011 Dominique Dumont
LICENSE
LGPL2
perl v5.22.1 2016-03-07 Config::Model:...d::MatchElement(3pm)