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¶
- •
- cme
- •
- Config::Model::models::Sshd::MatchBlock
AUTHOR¶
- Dominique Dumont
COPYRIGHT¶
- 2009-2011 Dominique Dumont
LICENSE¶
- LGPL2