Ubuntu Manpage: Config::Model::models::Sshd

Provided by: libconfig-model-openssh-perl_1.232-1_all

NAME

       Config::Model::models::Sshd - Configuration class Sshd

DESCRIPTION

       Configuration classes used by Config::Model

       Configuration class used by Config::Model to edit or validate /etc/ssh/sshd_config

Elements

AcceptEnv
Specifies what environment variables sent by the client will be copied into the session's
environ(7).Optional. Type list of uniline.

AddressFamily
Specifies which address family should be used by sshd(8).Optional. Type enum. choice: 'any', 'inet',
'inet6'. upstream_default: 'any'.

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.

ChallengeResponseAuthentication
Specifies whether challenge-response authentication is allowed. All authentication styles from
login.conf(5) are supported.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'yes'.

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.

Ciphers
Specifies the ciphers allowed for protocol version 2. By default, all ciphers are allowed.Optional. Type
check_list. choice: '3des-cbc', 'aes128-cbc', 'aes192-cbc', 'aes256-cbc', 'aes128-ctr', 'aes192-ctr',
'aes256-ctr', 'arcfour128', 'arcfour256', 'arcfour', 'blowfish-cbc', 'cast128-cbc'.

ClientAliveCountMax
Sets the number of client alive messages which may be sent without sshd(8) receiving any messages back
from the client. If this threshold is reached while client alive messages are being sent, sshd will
disconnect the client, terminating the session. It is important to note that the use of client alive
messages is very different from TCPKeepAlive. The client alive messages are sent through the encrypted
channel and therefore will not be spoofable. The TCP keepalive option enabled by TCPKeepAlive is
spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a
connection has become inactive.

The default value is 3. If ClientAliveInterval is set to 15, and ClientAliveCountMax is left at the
default, unresponsive SSH clients will be disconnected after approximately 45 seconds. This option
applies to protocol version 2 only.Optional. Type integer. upstream_default: '3'.

ClientAliveInterval
Optional. Type integer.

Compression
Specifies whether compression is allowed, or delayed until the user has authenticated
successfully.Optional. Type enum. choice: 'yes', 'delayed', 'no'. upstream_default: 'delayed'.

DebianBanner
Specifies whether the distribution-specified extra version suffix is included during initial protocol
handshake.Optional. Type boolean. upstream_default: '1'.

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'.

GSSAPIKeyExchange
Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange doesn't rely on ssh keys
to verify host identity. Note that this option applies to protocol version 2 only.Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'no'.

GSSAPICleanupCredentials
Specifies whether to automatically destroy the user's credentials cache on logout. Note that this option
applies to protocol version 2 only.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.

GSSAPIStrictAcceptorCheck
Determines whether to be strict about the identity of the GSSAPI acceptor a client authenticates
against.This facility is provided to assist with operation on multi homed machines. Note that this option
applies only to protocol version 2 GSSAPI connections, and setting it to "no" may only work with recent
Kerberos GSSAPI libraries.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.

Here are some explanations on the possible values:

'no'
the client may authenticate against any service key stored in the machine's default store

'yes'
the client must authenticate against the host service on the current hostname.

GSSAPIStoreCredentialsOnRekey
Controls whether the user's GSSAPI credentials should be updated following a successful connection
rekeying. This option can be used to accepted renewed or updated credentials from a compatible
client.Optional. Type boolean. upstream_default: '0'.

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

HostCertificate
Specifies a file containing a public host certificate. The certificate's public key must match a private
host key already specified by HostKey. The default behaviour of sshd(8) is not to load any
certificates.Optional. Type uniline.

HostKey
Specifies a file containing a private host key used by SSH. The default is /etc/ssh/ssh_host_key for
protocol version 1, and /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for protocol version 2.
Note that sshd(8) will refuse to use a file if it is group/world-accessible. It is possible to have
multiple host key files. "rsa1" keys are used for version 1 and "dsa" or "rsa" are used for version 2 of
the SSH protocol.Optional. Type list of uniline.

HostKeyAgent
Identifies the UNIX-domain socket used to communicate with an agent that has access to the private host
keys. If "SSH_AUTH_SOCK" is specified, the location of the socket will be read from the SSH_AUTH_SOCK
environment variable.Optional. Type uniline.

IgnoreRhosts
Specifies that .rhosts and .shosts files will not be used in RhostsRSAAuthentication or
HostbasedAuthentication. /etc/hosts.equiv and /etc/ssh/shosts.equiv are still used. Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'yes'.

IgnoreUserKnownHosts
Specifies whether sshd(8) should ignore the user's ~/.ssh/known_hosts during RhostsRSAAuthentication or
HostbasedAuthentication.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.

IPQoS - IPv4 type-of-service or DSCP class for the connection.
Specifies the IPv4 type-of-service or DSCP class for the connection. 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", or a numeric value.
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: 'lowdelay throughput'.

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'.

KerberosGetAFSToken
If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire an AFS token before accessing the
user's home directory.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.

KerberosOrLocalPasswd
If password authentication through Kerberos fails then the password will be validated via any additional
local mechanism such as /etc/passwd.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'yes'.

KerberosTicketCleanup
Specifies whether to automatically destroy the user's ticket cache file on logout.Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'yes'.

KexAlgorithms
Specifies the available KEX (Key Exchange) algorithms.Optional. Type check_list. choice:
'ecdh-sha2-nistp256', 'ecdh-sha2-nistp384', 'ecdh-sha2-nistp521', 'diffie-hellman-group-exchange-sha256',
'diffie-hellman-group-exchange-sha1', 'diffie-hellman-group14-sha1', 'diffie-hellman-group1-sha1'.

KeyRegenerationInterval
In protocol version 1, the ephemeral server key is automatically regenerated after this many seconds (if
it has been used). The purpose of regeneration is to prevent decrypting captured sessions by later
breaking into the machine and stealing the keys. The key is never stored anywhere. If the value is 0, the
key is never regenerated. The default is 3600 (seconds).Optional. Type integer. upstream_default: '3600'.

Port
Specifies the port number that sshd(8) listens on. The default is 22. Multiple options of this type are
permitted. See also ListenAddress.Optional. Type integer. upstream_default: '22'.

ListenAddress
Specifies the local addresses sshd(8) should listen on. The following forms may be used:

host|IPv4_addr|IPv6_addr
host|IPv4_addr:port
[host|IPv6_addr]:port

If port is not specified, sshd will listen on the address and all prior Port options specified. The
default is to listen on all local addresses. Multiple ListenAddress options are permitted. Additionally,
any Port options must precede this option for non-port qualified addresses.Optional. Type list of
uniline.

LoginGraceTime
The server disconnects after this time if the user has not successfully logged in. If the value is 0,
there is no time limit. The default is 120 seconds.Optional. Type integer. upstream_default: '120'.

LogLevel
Optional. Type enum. choice: 'SILENT', 'QUIET', 'FATAL', 'ERROR', 'INFO', 'VERBOSE', 'DEBUG', 'DEBUG1',
'DEBUG2', 'DEBUG3'. upstream_default: 'INFO'.

Here are some explanations on the possible values:

'DEBUG'
Logging with this level violates the privacy of users and is not recommended

'DEBUG1'
Logging with this level violates the privacy of users and is not recommended

'DEBUG2'
Logging with this level violates the privacy of users and is not recommended

'DEBUG3'
Logging with this level violates the privacy of users and is not recommended

MACs
Specifies the available MAC (message authentication code) algorithms. The MAC algorithm is used in
protocol version 2 for data integrity protection.Optional. Type check_list. choice: 'hmac-md5',
'hmac-md5-96', 'hmac-ripemd160', 'hmac-sha1', 'hmac-sha1-96', 'umac-64@openssh.com'.

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'.

MaxStartups
Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional
connections will be dropped until authentication succeeds or the LoginGraceTime expires for a connection.
The default is 10.

Alternatively, random early drop can be enabled by specifying the three colon separated values
"start:rate:full" (e.g. "10:30:60"). sshd(8) will refuse connection attempts with a probability of
"rate/100" (30%) if there are currently "start" (10) unauthenticated connections. The probability
increases linearly and all connection attempts are refused if the number of unauthenticated connections
reaches "full" (60).Optional. Type uniline. upstream_default: '10'.

PasswordAuthentication
Specifies whether password authentication is allowed.Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'yes'.

PermitBlacklistedKeys
Specifies whether sshd(8) should allow keys recorded in its blacklist of known-compromised keys (see
ssh-vulnkey(1)). If "yes", then attempts to authenticate with compromised keys will be logged but
accepted. If "no", then attempts to authenticate with compromised keys will be rejected.Optional. Type
boolean.

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"

PermitUserEnvironment
Specifies whether ~/.ssh/environment and environment= options in ~/.ssh/authorized_keys are processed by
sshd(8). The default is "no". Enabling environment processing may enable users to bypass access
restrictions in some configurations using mechanisms such as LD_PRELOAD.Optional. Type enum. choice:
'no', 'yes'. upstream_default: 'no'.

PidFile
Specifies the file that contains the process ID of the SSH daemon.Optional. Type uniline.
upstream_default: '/var/run/sshd.pid'.

PrintLastLog
Specifies whether sshd(8) should print the date and time of the last user login when a user logs in
interactively.Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'yes'.

PrintMotd
Specifies whether sshd(8) should print /etc/motd when a user logs in interactively. (On some systems it
is also printed by the shell, /etc/profile, or equivalent.)Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'yes'.

Protocol
Specifies the protocol versions sshd(8) supports. Note that the order of the protocol list does not
indicate preference, because the client selects among multiple protocol versions offered by the
server.Optional. Type check_list. choice: '1', '2'.

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'.

RevokedKeys - Revoked keys file
Specifies revoked public keys. Keys listed in this file will be refused for public key authentication.
Note that if this file is not readable, then public key authentication will be refused for all users.
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.

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'.

ServerKeyBits
Defines the number of bits in the ephemeral protocol version 1 server key. The minimum value is 512, and
the default is 768.Optional. Type integer. upstream_default: '768'.

StrictModes
Specifies whether sshd(8) should check file modes and ownership of the user's files and home directory
before accepting login. This is normally desirable because novices sometimes accidentally leave their
directory or files world-writable. The default is "yes". Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'yes'.

Subsystem
Configures an external subsystem (e.g. file transfer daemon). Keys of the hash should be a subsystem name
and hash value a command (with optional arguments) to execute upon subsystem request. The command
sftp-server(8) implements the "sftp" file transfer subsystem. By default no subsystems are defined. Note
that this option applies to protocol version 2 only.Optional. Type hash of uniline.

SyslogFacility
Gives the facility code that is used when logging messages from sshd(8). The default is AUTH.Optional.
Type enum. choice: 'DAEMON', 'USER', 'AUTH', 'LOCAL0', 'LOCAL1', 'LOCAL2', 'LOCAL3', 'LOCAL4', 'LOCAL5',
'LOCAL6', 'LOCAL7'. upstream_default: 'AUTH'.

KeepAlive
Deprecated Optional. Type enum. choice: 'no', 'yes'.

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. However, this means
that connections will die if the route is down temporarily, and some people find it annoying. On the
other hand, if TCP keepalives are not sent, sessions may hang indefinitely on the server, leaving "ghost"
users and consuming server resources. This option was formerly called KeepAlive.Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'yes'.

Here are some explanations on the possible values:

'no'
disable TCP keepalive messages

'yes'
Send TCP keepalive messages. The server will notice if the network goes down or the client host
crashes. This avoids infinitely hanging sessions.

Note: TCPKeepAlive is migrated with '$keep_alive' and with $keep_alive => ""- KeepAlive""

TrustedUserCAKeys
Specifies a file containing public keys of certificate authorities that are trusted to sign user
certificates for authentication. Keys are listed one per line; empty lines and comments starting with
'#' are allowed. If a certificate is presented for authentication and has its signing CA key listed in
this file, then it may be used for authentication for any user listed in the certificate's principals
list. Note that certificates that lack a list of principals will not be permitted for authentication
using TrustedUserCAKeys. For more details on certificates, see the CERTIFICATES section in
ssh-keygen(1).Optional. Type uniline.

UseDNS
Specifies whether sshd(8) should look up the remote host name and check that the resolved host name for
the remote IP address maps back to the very same IP address. The default is "yes"Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'yes'.

UseLogin
Specifies whether login(1) is used for interactive login sessions. The default is "no". Note that
login(1) is never used for remote command execution. Note also, that if this is enabled, X11Forwarding
will be disabled because login(1) does not know how to handle xauth(1) cookies. If UsePrivilegeSeparation
is specified, it will be disabled after authentication. Optional. Type enum. choice: 'no', 'yes'.
upstream_default: 'no'.

UsePAM
Enables the Pluggable Authentication Module interface. If set to "yes" this will enable PAM
authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM
account and session module processing for all authentication types.

Because PAM challenge-response authentication usually serves an equivalent role to password
authentication, you should disable either PasswordAuthentication or ChallengeResponseAuthentication.

If UsePAM is enabled, you will not be able to run sshd(8) as a non-root user. The default is
"no".Optional. Type enum. choice: 'no', 'yes'. upstream_default: 'no'.

UsePrivilegeSeparation
Specifies whether sshd(8) separates privileges by creating an unprivileged child process to deal with
incoming network traffic. After successful authentication, another process will be created that has the
privilege of the authenticated user. The goal of privilege separation is to prevent privilege escalation
by containing any corruption within the unprivileged processes. The default is "yes".Optional. Type enum.
choice: 'no', 'yes'. upstream_default: 'yes'.

VersionAddendum
Optionally specifies additional text to append to the SSH protocol banner sent by the server upon
connection. Optional. Type uniline.

XAuthLocation
Specifies the full pathname of the xauth(1) program.Optional. Type uniline. upstream_default:
'/usr/bin/X11/xauth'.

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'.

Match
Specifies a match block. The criteria User, Group Host and Address can contain patterns. When all these
criteria are satisfied (i.e. all patterns match the incoming connection), the parameters set in the block
element will override the general settings.Optional. Type list of node of class Sshd::MatchBlock .

AUTHOR

       Dominique Dumont

COPYRIGHT

       2009-2011 Dominique Dumont

LICENSE

       LGPL2

perl v5.18.1                                       2013-12-29                   Config::Model::models::Sshd(3pm)

NAME

DESCRIPTION

Elements

SEE ALSO

AUTHOR

COPYRIGHT

LICENSE