Config::Model::models::Sshd(3pm) User Contributed Perl Documentation Config::Model::models::Sshd(3pm)
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'.
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.
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. AuthorizedKeysFile may contain tokens of the
form %T which are substituted during connection setup.Optional. Type list of uniline.
Note: AuthorizedKeysFile values are migrated from '- AuthorizedKeysFile2'
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'.
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'.
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.
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
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.
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'.
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'.
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'.
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'.
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'.
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'.
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'.
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""
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'.
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.
SEE ALSO
o cme
o Config::Model::models::Sshd::MatchBlock
AUTHOR
Dominique Dumont
COPYRIGHT
2009-2011 Dominique Dumont
LICENSE
LGPL2
perl v5.14.2 2012-10-29 Config::Model::models::Sshd(3pm)