| SSHD_CONFIG(5) | File Formats Manual | SSHD_CONFIG(5) |
sshd_config —
-f on the command line). The file contains
keyword-argument pairs, one per line. Unless noted otherwise, for each
keyword, the first obtained value will be used. Lines starting with
‘#’ and empty lines are interpreted as
comments. Arguments may optionally be enclosed in double quotes (") in
order to represent arguments containing spaces.
The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive):
AcceptEnvSendEnv and SetEnv in
ssh_config(5) for how to
configure the client. The TERM environment
variable is always accepted whenever the client requests a pseudo-terminal
as it is required by the protocol. Variables are specified by name, which
may contain the wildcard characters
‘*’ and
‘?’. Multiple environment variables
may be separated by whitespace or spread across multiple
AcceptEnv directives. Be warned that some
environment variables could be used to bypass restricted user
environments. For this reason, care should be taken in the use of this
directive. The default is not to accept any environment variables.AddressFamilyany (the default), inet
(use IPv4 only), or inet6 (use IPv6 only).AllowAgentForwardingyes. Note that
disabling agent forwarding does not improve security unless users are also
denied shell access, as they can always install their own forwarders.AllowGroupsDenyGroups,
AllowGroups.
See PATTERNS in
ssh_config(5) for more
information on patterns. This keyword may appear multiple times in
sshd_config with each instance appending to the
list.
AllowStreamLocalForwardingyes (the
default) or all to allow StreamLocal forwarding,
no to prevent all StreamLocal forwarding,
local to allow local (from the perspective of
ssh(1)) forwarding only or
remote to allow remote forwarding only. Note that
disabling StreamLocal forwarding does not improve security unless users
are also denied shell access, as they can always install their own
forwarders.AllowTcpForwardingyes (the default) or all
to allow TCP forwarding, no to prevent all TCP
forwarding, local to allow local (from the
perspective of ssh(1))
forwarding only or remote to allow remote
forwarding only. Note that disabling TCP forwarding does not improve
security unless users are also denied shell access, as they can always
install their own forwarders.AllowUsersDenyUsers,
AllowUsers.
See PATTERNS in
ssh_config(5) for more
information on patterns. This keyword may appear multiple times in
sshd_config with each instance appending to the
list.
AuthenticationMethodsany to indicate the default
behaviour of accepting any single authentication method. If the default is
overridden, then successful authentication requires completion of every
method in at least one of these lists.
For example, “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.
If the publickey method is listed more than once, sshd(8) verifies that keys that have been used successfully are not reused for subsequent authentications. For example, “publickey,publickey” requires successful authentication using two different public keys.
Note that each authentication method listed should also be explicitly enabled in the configuration.
The available authentication methods are:
“gssapi-with-mic”, “hostbased”,
“keyboard-interactive”, “none” (used for
access to password-less accounts when
PermitEmptyPasswords is enabled),
“password” and “publickey”.
AuthorizedKeysCommandAuthorizedKeysCommand accept the tokens described
in the TOKENS section. If no arguments
are specified then the username of the target user is used.
The program should produce on standard output zero or more
lines of authorized_keys output (see
AUTHORIZED_KEYS in
sshd(8)).
AuthorizedKeysCommand is tried after the usual
AuthorizedKeysFile files and will not be
executed if a matching key is found there. By default, no
AuthorizedKeysCommand is run.
AuthorizedKeysCommandUserAuthorizedKeysCommand is run. It is recommended to
use a dedicated user that has no other role on the host than running
authorized keys commands. If AuthorizedKeysCommand
is specified but AuthorizedKeysCommandUser is not,
then sshd(8) will refuse to
start.AuthorizedKeysFileAuthorizedKeysFile accept the tokens described
in the TOKENS section. 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. Alternately this option may be set to
none to skip checking for user keys in files. The
default is “.ssh/authorized_keys
.ssh/authorized_keys2”.AuthorizedPrincipalsCommandAuthorizedPrincipalsFile. The
program must be owned by root, not writable by group or others and
specified by an absolute path. Arguments to
AuthorizedPrincipalsCommand accept the tokens
described in the TOKENS section. If no
arguments are specified then the username of the target user is used.
The program should produce on standard output zero or more
lines of AuthorizedPrincipalsFile output. If
either AuthorizedPrincipalsCommand or
AuthorizedPrincipalsFile is specified, then
certificates offered by the client for authentication must contain a
principal that is listed. By default, no
AuthorizedPrincipalsCommand is run.
AuthorizedPrincipalsCommandUserAuthorizedPrincipalsCommand is run. It is
recommended to use a dedicated user that has no other role on the host
than running authorized principals commands. If
AuthorizedPrincipalsCommand is specified but
AuthorizedPrincipalsCommandUser is not, then
sshd(8) will refuse to
start.AuthorizedPrincipalsFileTrustedUserCAKeys, 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.
Arguments to AuthorizedPrincipalsFile
accept the tokens described in the
TOKENS section. 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).
Bannernone
then no banner is displayed. By default, no banner is displayed.CASignatureAlgorithms
ssh-ed25519,ecdsa-sha2-nistp256,
ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,rsa-sha2-256
If the specified list begins with a ‘+’ character, then the specified algorithms will be appended to the default set instead of replacing them. If the specified list begins with a ‘-’ character, then the specified algorithms (including wildcards) will be removed from the default set instead of replacing them.
Certificates signed using other algorithms will not be accepted for public key or host-based authentication.
ChannelTimeoutThe timeout value “interval” is specified in seconds or may use any of the units documented in the TIME FORMATS section. For example, “session:*=5m” would cause all sessions to terminate after five minutes of inactivity. Specifying a zero value disables the inactivity timeout.
The available channel types include:
agent-connectiondirect-tcpip,
direct-streamlocal@openssh.comLocalForward or
DynamicForward.forwarded-tcpip,
forwarded-streamlocal@openssh.comRemoteForward.session:commandsession:shellsession:subsystem:...session:subsystem:sftp.x11-connectionNote that in all the above cases, terminating an inactive session does not guarantee to remove all resources associated with the session, e.g. shell processes or X11 clients relating to the session may continue to execute.
Moreover, terminating an inactive channel or session does not
necessarily close the SSH connection, nor does it prevent a client from
requesting another channel of the same type. In particular, expiring an
inactive forwarding session does not prevent another identical
forwarding from being subsequently created. See also
UnusedConnectionTimeout, which may be used in
conjunction with this option.
The default is not to expire channels of any type for inactivity.
ChrootDirectoryChrootDirectory accept the tokens described in the
TOKENS section.
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), 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 may require /dev/log
inside the chroot directory on some operating systems (see
sftp-server(8) for
details).
For safety, it is very important that the directory hierarchy be prevented from modification by other processes on the system (especially those outside the jail). Misconfiguration can lead to unsafe environments which sshd(8) cannot detect.
The default is none, indicating not to
chroot(2).
CiphersThe supported ciphers are:
The default is:
chacha20-poly1305@openssh.com,
aes128-ctr,aes192-ctr,aes256-ctr,
aes128-gcm@openssh.com,aes256-gcm@openssh.com
The list of available ciphers may also be obtained using “ssh -Q cipher”.
ClientAliveCountMaxTCPKeepAlive. 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 unresponsive.
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. Setting a zero ClientAliveCountMax
disables connection termination.
ClientAliveIntervalCompressionyes,
delayed (a legacy synonym for
yes) or no. The default is
yes.DenyGroupsDenyGroups,
AllowGroups.
See PATTERNS in
ssh_config(5) for more
information on patterns. This keyword may appear multiple times in
sshd_config with each instance appending to the
list.
DenyUsersDenyUsers, AllowUsers.
See PATTERNS in
ssh_config(5) for more
information on patterns. This keyword may appear multiple times in
sshd_config with each instance appending to the
list.
DisableForwardingExposeAuthInfoSSH_USER_AUTH environment variable. The default is
no.FingerprintHashmd5 and
sha256. The default is
sha256.ForceCommandForceCommand, ignoring any command supplied by the
client and ~/.ssh/rc if present. 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.
Specifying a command of internal-sftp will force
the use of an in-process SFTP server that requires no support files when
used with ChrootDirectory. The default is
none.GatewayPortsGatewayPorts can be
used to specify that sshd should allow remote port forwardings to bind to
non-loopback addresses, thus allowing other hosts to connect. The argument
may be no to force remote port forwardings to be
available to the local host only, yes to force
remote port forwardings to bind to the wildcard address, or
clientspecified to allow the client to select the
address to which the forwarding is bound. The default is
no.GSSAPIAuthenticationno.GSSAPICleanupCredentialsyes.GSSAPIStrictAcceptorCheckyes then
the client must authenticate against the host service on the current
hostname. If set to no then the client may
authenticate against any service key stored in the machine's default
store. This facility is provided to assist with operation on multi homed
machines. The default is yes.HostbasedAcceptedAlgorithms
ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,rsa-sha2-256
The list of available signature algorithms may also be obtained using “ssh -Q HostbasedAcceptedAlgorithms”. This was formerly named HostbasedAcceptedKeyTypes.
HostbasedAuthenticationno.HostbasedUsesNameFromPacketOnlyHostbasedAuthentication. A setting of
yes means that
sshd(8) uses the name supplied
by the client rather than attempting to resolve the name from the TCP
connection itself. The default is no.HostCertificateHostKey. The default behaviour of
sshd(8) is not to load any
certificates.HostKeyNote that sshd(8)
will refuse to use a file if it is group/world-accessible and that the
HostKeyAlgorithms option restricts which of the
keys are actually used by
sshd(8).
It is possible to have multiple host key files. It is also possible to specify public host key files instead. In this case operations on the private key will be delegated to an ssh-agent(1).
HostKeyAgentSSH_AUTH_SOCK environment
variable.HostKeyAlgorithms
ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,rsa-sha2-256
The list of available signature algorithms may also be obtained using “ssh -Q HostKeyAlgorithms”.
IgnoreRhostsHostbasedAuthentication. The system-wide
/etc/hosts.equiv and
/etc/shosts.equiv are still used regardless of
this setting.
Accepted values are yes (the default)
to ignore all per-user files, shosts-only to
allow the use of .shosts but to ignore
.rhosts or no to allow
both .shosts and
rhosts.
IgnoreUserKnownHostsHostbasedAuthentication and use only the
system-wide known hosts file
/etc/ssh/ssh_known_hosts. The default is
“no”.IncludeInclude directive may appear inside a
Match block to perform conditional inclusion.IPQoSaf11,
af12, af13,
af21, af22,
af23, af31,
af32, af33,
af41, af42,
af43, cs0,
cs1, cs2,
cs3, cs4,
cs5, cs6,
cs7, ef,
le, lowdelay,
throughput, reliability, a
numeric value, or none to use the operating system
default. 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 af21 (Low-Latency Data)
for interactive sessions and cs1 (Lower Effort)
for non-interactive sessions.KbdInteractiveAuthenticationyes. The argument to
this keyword must be yes or
no.
ChallengeResponseAuthentication is a deprecated
alias for this.KerberosAuthenticationPasswordAuthentication 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.KerberosGetAFSTokenno.KerberosOrLocalPasswdyes.KerberosTicketCleanupyes.KexAlgorithmsThe default is:
sntrup761x25519-sha512@openssh.com,
curve25519-sha256,curve25519-sha256@libssh.org,
ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
diffie-hellman-group-exchange-sha256,
diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,
diffie-hellman-group14-sha256
The list of available key exchange algorithms may also be obtained using “ssh -Q KexAlgorithms”.
ListenAddressListenAddress
hostname|address
[rdomain domain]ListenAddress
hostname:port
[rdomain domain]ListenAddress
IPv4_address:port
[rdomain domain]ListenAddress
[hostname|address]:port
[rdomain domain]The optional rdomain qualifier
requests sshd(8) listen in
an explicit routing domain. If port is not
specified, sshd will listen on the address and all
Port options specified. The default is to listen
on all local addresses on the current default routing domain. Multiple
ListenAddress options are permitted. For more
information on routing domains, see
rdomain(4).
LoginGraceTimeLogLevelLogVerbose
kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*
would enable detailed logging for line 1000 of
kex.c, everything in the
kex_exchange_identification() function, and all
code in the packet.c file. This option is
intended for debugging and no overrides are enabled by default.
MACsThe algorithms that contain “-etm” calculate the MAC after encryption (encrypt-then-mac). These are considered safer and their use recommended. The supported MACs are:
The default is:
umac-64-etm@openssh.com,umac-128-etm@openssh.com,
hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
hmac-sha1-etm@openssh.com,
umac-64@openssh.com,umac-128@openssh.com,
hmac-sha2-256,hmac-sha2-512,hmac-sha1
The list of available MAC algorithms may also be obtained using “ssh -Q mac”.
MatchMatch line are satisfied, the keywords on the
following lines override those set in the global section of the config
file, until either another Match line or the end
of the file. If a keyword appears in multiple
Match blocks that are satisfied, only the first
instance of the keyword is applied.
The arguments to Match are one or more
criteria-pattern pairs or the single token All
which matches all criteria. The available criteria are
User, Group,
Host, LocalAddress,
LocalPort, RDomain, and
Address (with RDomain
representing the
rdomain(4) on which the
connection was received).
The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNS section of ssh_config(5).
The patterns in an Address criteria
may additionally contain addresses to match in CIDR address/masklen
format, such as 192.0.2.0/24 or 2001:db8::/32. Note that the mask length
provided must be consistent with the address - it is an error to specify
a mask length that is too long for the address or one with bits set in
this host portion of the address. For example, 192.0.2.0/33 and
192.0.2.0/8, respectively.
Only a subset of keywords may be used on the lines following a
Match keyword. Available keywords are
AcceptEnv,
AllowAgentForwarding,
AllowGroups,
AllowStreamLocalForwarding,
AllowTcpForwarding,
AllowUsers,
AuthenticationMethods,
AuthorizedKeysCommand,
AuthorizedKeysCommandUser,
AuthorizedKeysFile,
AuthorizedPrincipalsCommand,
AuthorizedPrincipalsCommandUser,
AuthorizedPrincipalsFile,
Banner,
CASignatureAlgorithms,
ChannelTimeout,
ChrootDirectory,
ClientAliveCountMax,
ClientAliveInterval,
DenyGroups, DenyUsers,
DisableForwarding,
ExposeAuthInfo,
ForceCommand,
GatewayPorts,
GSSAPIAuthentication,
HostbasedAcceptedAlgorithms,
HostbasedAuthentication,
HostbasedUsesNameFromPacketOnly,
IgnoreRhosts, Include,
IPQoS,
KbdInteractiveAuthentication,
KerberosAuthentication,
LogLevel, MaxAuthTries,
MaxSessions,
PasswordAuthentication,
PermitEmptyPasswords,
PermitListen,
PermitOpen,
PermitRootLogin,
PermitTTY, PermitTunnel,
PermitUserRC,
PubkeyAcceptedAlgorithms,
PubkeyAuthentication,
PubkeyAuthOptions,
RekeyLimit, RevokedKeys,
RDomain, SetEnv,
StreamLocalBindMask,
StreamLocalBindUnlink,
TrustedUserCAKeys,
UnusedConnectionTimeout,
X11DisplayOffset,
X11Forwarding and
X11UseLocalhost.
MaxAuthTriesMaxSessionsMaxSessions to 1 will effectively disable session
multiplexing, whereas setting it to 0 will prevent all shell, login and
subsystem sessions while still permitting forwarding. The default is
10.MaxStartupsLoginGraceTime
expires for a connection. The default is 10:30:100.
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).
ModuliFilePasswordAuthenticationyes.PermitEmptyPasswordsno.PermitListenPermitListen
portPermitListen
host:portMultiple permissions may be specified by separating them with
whitespace. An argument of any can be used to
remove all restrictions and permit any listen requests. An argument of
none can be used to prohibit all listen
requests. The host name may contain wildcards as described in the
PATTERNS section in
ssh_config(5). The
wildcard ‘*’ can also be used in place of a port number to
allow all ports. By default all port forwarding listen requests are
permitted. Note that the GatewayPorts option may
further restrict which addresses may be listened on. Note also that
ssh(1) will request a listen
host of “localhost” if no listen host was specifically
requested, and this name is treated differently to explicit localhost
addresses of “127.0.0.1” and “::1”.
PermitOpenPermitOpen
host:portPermitOpen
IPv4_addr:portPermitOpen
[IPv6_addr]:portMultiple forwards may be specified by separating them with
whitespace. An argument of any can be used to
remove all restrictions and permit any forwarding requests. An argument
of none can be used to prohibit all forwarding
requests. The wildcard ‘*’ can be used for host or port to
allow all hosts or ports respectively. Otherwise, no pattern matching or
address lookups are performed on supplied names. By default all port
forwarding requests are permitted.
PermitRootLoginyes, prohibit-password,
forced-commands-only, or
no. The default is
prohibit-password.
If this option is set to
prohibit-password (or its deprecated alias,
without-password), password and
keyboard-interactive authentication are disabled for root.
If this option is set to
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.
If this option is set to no, root is
not allowed to log in.
PermitTTYyes.PermitTunnelyes,
point-to-point (layer 3),
ethernet (layer 2), or no.
Specifying yes permits both
point-to-point and
ethernet. The default is
no.
Independent of this setting, the permissions of the selected tun(4) device must allow access to the user.
PermitUserEnvironmentenvironment= options in
~/.ssh/authorized_keys are processed by
sshd(8). Valid options are
yes, no or a pattern-list
specifying which environment variable names to accept (for example
“LANG,LC_*”). The default is no.
Enabling environment processing may enable users to bypass access
restrictions in some configurations using mechanisms such as
LD_PRELOAD.PermitUserRCyes.PerSourceMaxStartupsMaxStartups, whichever
is lower. The default is none.PerSourceNetBlockSize32:128, which means each address is considered
individually.PidFilenone to not write one. The default is
/var/run/sshd.pid.PortListenAddress.PrintLastLogyes.PrintMotdyes.PubkeyAcceptedAlgorithms
ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,rsa-sha2-256
The list of available signature algorithms may also be obtained using “ssh -Q PubkeyAcceptedAlgorithms”.
PubkeyAuthOptionsnone (the default; indicating no additional
options are enabled), touch-required and
verify-required.
The touch-required option causes
public key authentication using a FIDO authenticator algorithm (i.e.
ecdsa-sk or ed25519-sk)
to always require the signature to attest that a physically present user
explicitly confirmed the authentication (usually by touching the
authenticator). By default,
sshd(8) requires user
presence unless overridden with an authorized_keys option. The
touch-required flag disables this override.
The verify-required option requires a
FIDO key signature attest that the user was verified, e.g. via a
PIN.
Neither the touch-required or
verify-required options have any effect for
other, non-FIDO, public key types.
PubkeyAuthenticationyes.RekeyLimitRekeyLimit 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.RequiredRSASize1024 bits. Note that this limit may
only be raised from the default.RevokedKeysnone to not
use one. 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).RDomain%D, then the domain in which the
incoming connection was received will be applied.SecurityKeyProviderSetEnvSetEnv override the default environment and any
variables specified by the user via AcceptEnv or
PermitUserEnvironment.StreamLocalBindMaskThe default value is 0177, which creates a Unix-domain socket file that is readable and writable only by the owner. Note that not all operating systems honor the file mode on Unix-domain socket files.
StreamLocalBindUnlinkStreamLocalBindUnlink is not
enabled, sshd will be unable to forward the port
to the Unix-domain socket file. This option is only used for port
forwarding to a Unix-domain socket file.
The argument must be yes or
no. The default is
no.
StrictModesyes. Note that this
does not apply to ChrootDirectory, whose
permissions and ownership are checked unconditionally.SubsystemThe command sftp-server implements the
SFTP file transfer subsystem.
Alternately the name internal-sftp
implements an in-process SFTP server. This may simplify configurations
using ChrootDirectory to force a different
filesystem root on clients.
By default no subsystems are defined.
SyslogFacilityTCPKeepAliveThe default is yes (to send TCP
keepalive messages), and the server will notice if the network goes down
or the client host crashes. This avoids infinitely hanging sessions.
To disable TCP keepalive messages, the value should be set to
no.
TrustedUserCAKeysnone to not use one. 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).UnusedConnectionTimeout-R flag, are not considered as open channels and
do not prevent the timeout. The timeout value is specified in seconds or
may use any of the units documented in the
TIME FORMATS section.
Note that this timeout starts when the client connection completes user authentication but before the client has an opportunity to open any channels. Caution should be used when using short timeout values, as they may not provide sufficient time for the client to request and open its channels before terminating the connection.
The default none is to never expire
connections for having no open channels. This option may be useful in
conjunction with ChannelTimeout.
UseDNSIf this option is set to no (the
default) then only addresses and not host names may be used in
~/.ssh/authorized_keys
from and sshd_config
Match Host
directives.
VersionAddendumnone.X11DisplayOffsetX11Forwardingyes or no. The default is
no.
When X11 forwarding is enabled, there may be additional
exposure to the server and to client displays if the
sshd(8) proxy display is
configured to listen on the wildcard address (see
X11UseLocalhost), though this is not the
default. Additionally, the authentication spoofing and authentication
data verification and substitution occur on the client side. The
security risk of using X11 forwarding is that the client's X11 display
server may be exposed to attack when the SSH client requests forwarding
(see the warnings for ForwardX11 in
ssh_config(5)). A
system administrator may have a stance in which they want to protect
clients that may expose themselves to attack by unwittingly requesting
X11 forwarding, which can warrant a no
setting.
Note that disabling X11 forwarding does not prevent users from forwarding X11 traffic, as users can always install their own forwarders.
X11UseLocalhostDISPLAY 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. The argument must be
yes or no. The default is
yes.XAuthLocationnone to not use one. The default is
/usr/X11R6/bin/xauth.UseLPKLpkLdapConfLpkServersLpkServers ldaps://127.0.0.1 ldap://127.0.0.2 ldap://127.0.0.3
LpkUserDNLpkUserDN ou=users,dc=phear,dc=org
LpkGroupDNLpkGroupDN ou=groups,dc=phear,dc=org
LpkBindDNLpkBindDN cn=Manager,dc=phear,dc=org
LpkBindPwLpkBindPw secret
LpkServerGroupLpkServerGroup unix mail prod
LpkFilterLpkFilter (hostAccess=master.phear.org)
LpkForceTLSLpkSearchTimelimitLpkSearchTimelimit 3
LpkBindTimelimitLpkBindTimelimit 3
Each member of the sequence is added together to calculate the total time value.
Time format examples:
AuthorizedKeysCommand accepts the tokens
%%, %C, %D, %f, %h, %k, %t, %U, and %u.
AuthorizedKeysFile accepts the tokens %%,
%h, %U, and %u.
AuthorizedPrincipalsCommand accepts the
tokens %%, %C, %D, %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.
AuthorizedPrincipalsFile accepts the
tokens %%, %h, %U, and %u.
ChrootDirectory accepts the tokens %%, %h,
%U, and %u.
RoutingDomain accepts the token %D.
| July 28 2023 | NetBSD 9.4 |