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