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SSHD_CONFIG(5)		    BSD	File Formats Manual		SSHD_CONFIG(5)

NAME
     sshd_config -- OpenSSH SSH	daemon configuration file

SYNOPSIS
     /etc/ssh/sshd_config

DESCRIPTION
     sshd(8) reads configuration data from /etc/ssh/sshd_config	(or the	file
     specified with -f on the command line).  The file contains	keyword-argu-
     ment pairs, one per line.	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	key-
     words are case-insensitive	and arguments are case-sensitive):

     AcceptEnv
	     Specifies what environment	variables sent by the client will be
	     copied into the session's environ(7).  See	SendEnv	in
	     ssh_config(5) for how to configure	the client.  The TERM environ-
	     ment variable is always sent 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.

     AddressFamily
	     Specifies which address family should be used by sshd(8).	Valid
	     arguments are "any", "inet" (use IPv4 only), or "inet6" (use IPv6
	     only).  The default is "any".

     AllowAgentForwarding
	     Specifies whether ssh-agent(1) forwarding is permitted.  The de-
	     fault is "yes".  Note that	disabling agent	forwarding does	not
	     improve security unless users are also denied shell access, as
	     they can always install their own forwarders.

     AllowGroups
	     This keyword can be followed by a list of group name patterns,
	     separated by spaces.  If specified, 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.

	     See PATTERNS in ssh_config(5) for more information	on patterns.

     AllowTcpForwarding
	     Specifies whether TCP forwarding is permitted.  The available op-
	     tions are "yes" 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.  The	default	is "yes".  Note	that disabling TCP forwarding
	     does not improve security unless users are	also denied shell ac-
	     cess, as they can always install their own	forwarders.

     AllowStreamLocalForwarding
	     Specifies whether StreamLocal (Unix-domain	socket)	forwarding is
	     permitted.	 The available options are "yes" or "all" to allow
	     StreamLocal forwarding, "no" to prevent all StreamLocal forward-
	     ing, "local" to allow local (from the perspective of ssh(1)) for-
	     warding only or "remote" to allow remote forwarding only.	The
	     default is	"yes".	Note that disabling StreamLocal	forwarding
	     does not improve security unless users are	also denied shell ac-
	     cess, as they can always install their own	forwarders.

     AllowUsers
	     This keyword can be followed by a 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.

	     See PATTERNS in ssh_config(5) for more information	on patterns.

     AuthenticationMethods
	     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 com-
	     plete 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 exam-
	     ple, it would not be possible to attempt password or keyboard-in-
	     teractive 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 interac-
	     tive authentication to the	"bsdauth" device.

	     If	the "publickey"	method is listed more than once, sshd(8) veri-
	     fies that keys that have been used	successfully are not reused
	     for subsequent authentications.  For example, an
	     AuthenticationMethods of "publickey,publickey" will require suc-
	     cessful authentication using two different	public keys.

	     This option 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.

     AuthorizedKeysCommand
	     Specifies a program to be used to look up the user's public keys.
	     The program must be owned by root,	not writable by	group or oth-
	     ers and specified by an absolute path.

	     Arguments to AuthorizedKeysCommand	may be provided	using the fol-
	     lowing tokens, which will be expanded at runtime: %% is replaced
	     by	a literal '%', %u is replaced by the username being authenti-
	     cated, %h is replaced by the home directory of the	user being au-
	     thenticated, %t is	replaced with the key type offered for authen-
	     tication, %f is replaced with the fingerprint of the key, and %k
	     is	replaced with the key being offered for	authentication.	 If no
	     arguments are specified then the username of the target user will
	     be	supplied.

	     The program 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 au-
	     thenticate	and authorize the user then public key authentication
	     continues using the usual AuthorizedKeysFile files.  By default,
	     no	AuthorizedKeysCommand is run.

     AuthorizedKeysCommandUser
	     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.  If
	     AuthorizedKeysCommand is specified	but AuthorizedKeysCommandUser
	     is	not, then sshd(8) will refuse to start.

     AuthorizedKeysFile
	     Specifies the file	that contains the public keys that can be used
	     for user authentication.  The format is described in the AUTHO-
	     RIZED_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	re-
	     placed 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.  Alter-
	     nately this option	may be set to "none" to	skip checking for user
	     keys in files.  The default is ".ssh/authorized_keys
	     .ssh/authorized_keys2".

     AuthorizedPrincipalsCommand
	     Specifies a program to be used to generate	the list of allowed
	     certificate principals as per AuthorizedPrincipalsFile.  The pro-
	     gram must be owned	by root, not writable by group or others and
	     specified by an absolute path.

	     Arguments to AuthorizedPrincipalsCommand may be provided using
	     the following tokens, which will be expanded at runtime: %% is
	     replaced by a literal '%',	%u is replaced by the username being
	     authenticated and %h is replaced by the home directory of the
	     user being	authenticated.

	     The program should	produce	on standard output zero	or more	lines
	     of	AuthorizedPrincipalsFile output.  If either
	     AuthorizedPrincipalsCommand or AuthorizedPrincipalsFile is	speci-
	     fied, then	certificates offered by	the client for authentication
	     must contain a principal that is listed.  By default, no Autho-
	     rizedPrincipalsCommand is run.

     AuthorizedPrincipalsCommandUser
	     Specifies the user	under whose account the	AuthorizedPrinci-
	     palsCommand is run.  It is	recommended to use a dedicated user
	     that has no other role on the host	than running authorized	prin-
	     cipals commands.  If AuthorizedPrincipalsCommand is specified but
	     AuthorizedPrincipalsCommandUser is	not, then sshd(8) will refuse
	     to	start.

     AuthorizedPrincipalsFile
	     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 re-
	     placed 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 certifi-
	     cate's principals list for	it to be accepted.  Note that
	     AuthorizedPrincipalsFile is only used when	authentication pro-
	     ceeds 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).

     Banner  The contents of the specified file	are sent to the	remote user
	     before authentication is allowed.	If the argument	is "none" then
	     no	banner is displayed.  By default, no banner is displayed.

     ChallengeResponseAuthentication
	     Specifies whether challenge-response authentication is allowed
	     (e.g. via PAM or through authentication styles supported in
	     login.conf(5)) The	default	is "yes".

     ChrootDirectory
	     Specifies the pathname of a directory to chroot(2)	to after au-
	     thentication.  At session startup sshd(8) checks that all compo-
	     nents of the pathname are root-owned directories which 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	user-
	     name of that user.

	     The ChrootDirectory must contain the necessary files and directo-
	     ries 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 operat-
	     ing 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 (es-
	     pecially those outside the	jail).	Misconfiguration can lead to
	     unsafe environments which sshd(8) cannot detect.

	     The default is "none", indicating not to chroot(2).

     Ciphers
	     Specifies the ciphers allowed.  Multiple ciphers must be comma-
	     separated.	 If the	specified value	begins with a `+' character,
	     then the specified	ciphers	will be	appended to the	default	set
	     instead of	replacing them.

	     The supported ciphers are:

		   3des-cbc
		   aes128-cbc
		   aes192-cbc
		   aes256-cbc
		   aes128-ctr
		   aes192-ctr
		   aes256-ctr
		   aes128-gcm@openssh.com
		   aes256-gcm@openssh.com
		   arcfour
		   arcfour128
		   arcfour256
		   blowfish-cbc
		   cast128-cbc
		   chacha20-poly1305@openssh.com

	     The default is:

		   chacha20-poly1305@openssh.com,
		   aes128-ctr,aes192-ctr,aes256-ctr,
		   aes128-gcm@openssh.com,aes256-gcm@openssh.com,
		   aes128-cbc,aes192-cbc,aes256-cbc

	     The list of available ciphers may also be obtained	using the -Q
	     option of ssh(1) with an argument of "cipher".

     ClientAliveCountMax
	     Sets the number of	client alive messages (see below) which	may be
	     sent without sshd(8) receiving any	messages back from the client.
	     If	this threshold is reached while	client alive messages are be-
	     ing sent, sshd will disconnect the	client,	terminating the	ses-
	     sion.  It is important to note that the use of client alive mes-
	     sages is very different from TCPKeepAlive (below).	 The client
	     alive messages are	sent through the encrypted channel and there-
	     fore will not be spoofable.  The TCP keepalive option enabled by
	     TCPKeepAlive is spoofable.	 The client alive mechanism is valu-
	     able when the client or server depend on knowing when a connec-
	     tion has become inactive.

	     The default value is 3.  If ClientAliveInterval (see below) is
	     set to 15,	and ClientAliveCountMax	is left	at the default,	unre-
	     sponsive SSH clients will be disconnected after approximately 45
	     seconds.

     ClientAliveInterval
	     Sets a timeout interval in	seconds	after which if no data has
	     been received from	the client, sshd(8) will send a	message
	     through the encrypted channel to request a	response from the
	     client.  The default is 0,	indicating that	these messages will
	     not be sent to the	client.

     Compression
	     Specifies whether compression is allowed, or delayed until	the
	     user has authenticated successfully.  The argument	must be	"yes",
	     "delayed",	or "no".  The default is "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 recog-
	     nized.  By	default, login is allowed for all groups.  The al-
	     low/deny directives are processed in the following	order:
	     DenyUsers,	AllowUsers, DenyGroups,	and finally AllowGroups.

	     See PATTERNS in ssh_config(5) for more information	on patterns.

     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 numeri-
	     cal 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 pro-
	     cessed in the following order: DenyUsers, AllowUsers, DenyGroups,
	     and finally AllowGroups.

	     See PATTERNS in ssh_config(5) for more information	on patterns.

     FingerprintHash
	     Specifies the hash	algorithm used when logging key	fingerprints.
	     Valid options are:	"md5" and "sha256".  The default is "sha256".

     ForceCommand
	     Forces the	execution of the command specified by ForceCommand,
	     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".

     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 con-
	     nect.  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".

     GSSAPIAuthentication
	     Specifies whether user authentication based on GSSAPI is allowed.
	     The default is "no".

     GSSAPICleanupCredentials
	     Specifies whether to automatically	destroy	the user's credentials
	     cache on logout.  The default is "yes".

     GSSAPIStrictAcceptorCheck
	     Determines	whether	to be strict about the identity	of the GSSAPI
	     acceptor a	client authenticates against.  If set to "yes" then
	     the client	must authenticate against the host service on the cur-
	     rent 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".

     HostbasedAcceptedKeyTypes
	     Specifies the key types that will be accepted for hostbased au-
	     thentication as a comma-separated pattern list.  Alternately if
	     the specified value begins	with a `+' character, then the speci-
	     fied key types will be appended to	the default set	instead	of re-
	     placing them.  The	default	for this option	is:

		ecdsa-sha2-nistp256-cert-v01@openssh.com,
		ecdsa-sha2-nistp384-cert-v01@openssh.com,
		ecdsa-sha2-nistp521-cert-v01@openssh.com,
		ssh-ed25519-cert-v01@openssh.com,
		ssh-rsa-cert-v01@openssh.com,
		ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
		ssh-ed25519,ssh-rsa

	     The -Q option of ssh(1) may be used to list supported key types.

     HostbasedAuthentication
	     Specifies whether rhosts or /etc/hosts.equiv authentication to-
	     gether with successful public key client host authentication is
	     allowed (host-based authentication).  The default is "no".

     HostbasedUsesNameFromPacketOnly
	     Specifies whether or not the server will attempt to perform a re-
	     verse name	lookup when matching the name in the ~/.shosts,
	     ~/.rhosts,	and /etc/hosts.equiv files during
	     HostbasedAuthentication.  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".

     HostCertificate
	     Specifies a file containing a public host certificate.  The cer-
	     tificate's	public key must	match a	private	host key already spec-
	     ified by HostKey.	The default behaviour of sshd(8) is not	to
	     load any certificates.

     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_dsa_key,	/etc/ssh/ssh_host_ecdsa_key,
	     /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key for
	     protocol version 2.

	     Note 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.  "rsa1" keys are
	     used for version 1	and "dsa", "ecdsa", "ed25519" or "rsa" are
	     used for version 2	of the SSH protocol.  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).

     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.

     HostKeyAlgorithms
	     Specifies the host	key algorithms that the	server offers.	The
	     default for this option is:

		ecdsa-sha2-nistp256-cert-v01@openssh.com,
		ecdsa-sha2-nistp384-cert-v01@openssh.com,
		ecdsa-sha2-nistp521-cert-v01@openssh.com,
		ssh-ed25519-cert-v01@openssh.com,
		ssh-rsa-cert-v01@openssh.com,
		ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
		ssh-ed25519,ssh-rsa

	     The list of available key types may also be obtained using	the -Q
	     option of ssh(1) with an argument of "key".

     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.	 The
	     default is	"yes".

     IgnoreUserKnownHosts
	     Specifies whether sshd(8) should ignore the user's
	     ~/.ssh/known_hosts	during RhostsRSAAuthentication or
	     HostbasedAuthentication.  The default is "no".

     IPQoS   Specifies the IPv4	type-of-service	or DSCP	class for the connec-
	     tion.  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 white-
	     space.  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 in-
	     teractive sessions	and "throughput" for non-interactive sessions.

     KbdInteractiveAuthentication
	     Specifies whether to allow	keyboard-interactive authentication.
	     The argument to this keyword must be "yes"	or "no".  The default
	     is	to use whatever	value ChallengeResponseAuthentication is set
	     to	(by default "yes").

     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".

     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.
	     The default is "no".

     KerberosOrLocalPasswd
	     If	password authentication	through	Kerberos fails then the	pass-
	     word will be validated via	any additional local mechanism such as
	     /etc/passwd.  The default is "yes".

     KerberosTicketCleanup
	     Specifies whether to automatically	destroy	the user's ticket
	     cache file	on logout.  The	default	is "yes".

     KexAlgorithms
	     Specifies the available KEX (Key Exchange)	algorithms.  Multiple
	     algorithms	must be	comma-separated.  Alternately if the specified
	     value begins with a `+' character,	then the specified methods
	     will be appended to the default set instead of replacing them.
	     The supported algorithms are:

		   curve25519-sha256@libssh.org
		   diffie-hellman-group1-sha1
		   diffie-hellman-group14-sha1
		   diffie-hellman-group-exchange-sha1
		   diffie-hellman-group-exchange-sha256
		   ecdh-sha2-nistp256
		   ecdh-sha2-nistp384
		   ecdh-sha2-nistp521

	     The default is:

		   curve25519-sha256@libssh.org,
		   ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
		   diffie-hellman-group-exchange-sha256,
		   diffie-hellman-group14-sha1

	     The list of available key exchange	algorithms may also be ob-
	     tained using the -Q option	of ssh(1) with an argument of "kex".

     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 ses-
	     sions 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).

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

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

	     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.	 Multiple ListenAddress	options	are permitted.

     LoginGraceTime
	     The server	disconnects after this time if the user	has not	suc-
	     cessfully logged in.  If the value	is 0, there is no time limit.
	     The default is 120	seconds.

     LogLevel
	     Gives the verbosity level that is used when logging messages from
	     sshd(8).  The possible values are:	QUIET, FATAL, ERROR, INFO,
	     VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.  The default is INFO.
	     DEBUG and DEBUG1 are equivalent.  DEBUG2 and DEBUG3 each specify
	     higher levels of debugging	output.	 Logging with a	DEBUG level
	     violates the privacy of users and is not recommended.

     MACs    Specifies the available MAC (message authentication code) algo-
	     rithms.  The MAC algorithm	is used	for data integrity protection.
	     Multiple algorithms must be comma-separated.  If the specified
	     value begins with a `+' character,	then the specified algorithms
	     will be appended to the default set instead of replacing them.

	     The algorithms that contain "-etm"	calculate the MAC after	en-
	     cryption (encrypt-then-mac).  These are considered	safer and
	     their use recommended.  The supported MACs	are:

		   hmac-md5
		   hmac-md5-96
		   hmac-ripemd160
		   hmac-sha1
		   hmac-sha1-96
		   hmac-sha2-256
		   hmac-sha2-512
		   umac-64@openssh.com
		   umac-128@openssh.com
		   hmac-md5-etm@openssh.com
		   hmac-md5-96-etm@openssh.com
		   hmac-ripemd160-etm@openssh.com
		   hmac-sha1-etm@openssh.com
		   hmac-sha1-96-etm@openssh.com
		   hmac-sha2-256-etm@openssh.com
		   hmac-sha2-512-etm@openssh.com
		   umac-64-etm@openssh.com
		   umac-128-etm@openssh.com

	     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
	     the -Q option of ssh(1) with an argument of "mac".

     Match   Introduces	a conditional block.  If all of	the criteria on	the
	     Match line	are satisfied, the keywords on the following lines
	     override those set	in the global section of the config file, un-
	     til either	another	Match line or the end of the file.  If a key-
	     word 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, and
	     Address.  The match patterns may consist of single	entries	or
	     comma-separated lists and may use the wildcard and	negation oper-
	     ators described in	the PATTERNS section of	ssh_config(5).

	     The patterns in an	Address	criteria may additionally contain ad-
	     dresses to	match in CIDR address/masklen format, e.g.
	     "192.0.2.0/24" or "3ffe:ffff::/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, ChrootDirectory, DenyGroups, DenyUsers, ForceCommand,
	     GatewayPorts, GSSAPIAuthentication, HostbasedAcceptedKeyTypes,
	     HostbasedAuthentication, HostbasedUsesNameFromPacketOnly, IPQoS,
	     KbdInteractiveAuthentication, KerberosAuthentication,
	     MaxAuthTries, MaxSessions,	PasswordAuthentication,
	     PermitEmptyPasswords, PermitOpen, PermitRootLogin,	PermitTTY,
	     PermitTunnel, PermitUserRC, PubkeyAcceptedKeyTypes,
	     PubkeyAuthentication, RekeyLimit, RevokedKeys,
	     RhostsRSAAuthentication, RSAAuthentication, StreamLocalBindMask,
	     StreamLocalBindUnlink, TrustedUserCAKeys, X11DisplayOffset,
	     X11Forwarding and X11UseLocalHost.

     MaxAuthTries
	     Specifies the maximum number of authentication attempts permitted
	     per connection.  Once the number of failures reaches half this
	     value, additional failures	are logged.  The default is 6.

     MaxSessions
	     Specifies the maximum number of open shell, login or subsystem
	     (e.g. sftp) sessions permitted per	network	connection.  Multiple
	     sessions may be established by clients that support connection
	     multiplexing.  Setting MaxSessions	to 1 will effectively disable
	     session multiplexing, whereas setting it to 0 will	prevent	all
	     shell, login and subsystem	sessions while still permitting	for-
	     warding.  The default is 10.

     MaxStartups
	     Specifies the maximum number of concurrent	unauthenticated	con-
	     nections to the SSH daemon.  Additional connections will be
	     dropped until authentication succeeds or the LoginGraceTime ex-
	     pires 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) unauthenti-
	     cated connections.	 The probability increases linearly and	all
	     connection	attempts are refused if	the number of unauthenticated
	     connections reaches "full"	(60).

     PasswordAuthentication
	     Specifies whether password	authentication is allowed.  See	also
	     UsePAM.  The default is "no".

     PermitEmptyPasswords
	     When password authentication is allowed, it specifies whether the
	     server allows login to accounts with empty	password strings.  The
	     default is	"no".

     PermitOpen
	     Specifies the destinations	to which TCP port forwarding is	per-
	     mitted.  The forwarding specification must	be one of the follow-
	     ing forms:

		   PermitOpen host:port
		   PermitOpen IPv4_addr:port
		   PermitOpen [IPv6_addr]:port

	     Multiple forwards may be specified	by separating them with	white-
	     space.  An	argument of "any" can be used to remove	all restric-
	     tions and permit any forwarding requests.	An argument of "none"
	     can be used to prohibit all forwarding requests.  By default all
	     port forwarding requests are permitted.

     PermitRootLogin
	     Specifies whether root can	log in using ssh(1).  The argument
	     must be "yes", "prohibit-password", "without-password",
	     "forced-commands-only", or	"no".  The default is "no".  Note that
	     if	ChallengeResponseAuthentication	is "yes", the root user	may be
	     allowed in	with its password even if PermitRootLogin is set to
	     "without-password".

	     If	this option is set to "prohibit-password" or
	     "without-password", password and keyboard-interactive authentica-
	     tion 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.

     PermitTunnel
	     Specifies whether tun(4) device forwarding	is allowed.  The argu-
	     ment must be "yes", "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.

     PermitTTY
	     Specifies whether pty(4) allocation is permitted.	The default is
	     "yes".

     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.

     PermitUserRC
	     Specifies whether any ~/.ssh/rc file is executed.	The default is
	     "yes".

     PidFile
	     Specifies the file	that contains the process ID of	the SSH	dae-
	     mon, or "none" to not write one.  The default is
	     /var/run/sshd.pid.

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

     PrintLastLog
	     Specifies whether sshd(8) should print the	date and time of the
	     last user login when a user logs in interactively.	 The default
	     is	"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.)  The default is "yes".

     Protocol
	     Specifies the protocol versions sshd(8) supports.	The possible
	     values are	`1' and	`2'.  Multiple versions	must be	comma-sepa-
	     rated.  The default is `2'.  Protocol 1 suffers from a number of
	     cryptographic weaknesses and should not be	used.  It is only of-
	     fered to support legacy devices.

	     Note that the order of the	protocol list does not indicate	pref-
	     erence, because the client	selects	among multiple protocol	ver-
	     sions offered by the server.  Specifying "2,1" is identical to
	     "1,2".

     PubkeyAcceptedKeyTypes
	     Specifies the key types that will be accepted for public key au-
	     thentication as a comma-separated pattern list.  Alternately if
	     the specified value begins	with a `+' character, then the speci-
	     fied key types will be appended to	the default set	instead	of re-
	     placing them.  The	default	for this option	is:

		ecdsa-sha2-nistp256-cert-v01@openssh.com,
		ecdsa-sha2-nistp384-cert-v01@openssh.com,
		ecdsa-sha2-nistp521-cert-v01@openssh.com,
		ssh-ed25519-cert-v01@openssh.com,
		ssh-rsa-cert-v01@openssh.com,
		ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
		ssh-ed25519,ssh-rsa

	     The -Q option of ssh(1) may be used to list supported key types.

     PubkeyAuthentication
	     Specifies whether public key authentication is allowed.  The de-
	     fault is "yes".

     RekeyLimit
	     Specifies the maximum amount of data that may be transmitted be-
	     fore the session key is renegotiated, optionally followed a maxi-
	     mum amount	of time	that may pass before the session key is	rene-
	     gotiated.	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.

     RevokedKeys
	     Specifies revoked public keys file, or "none" to not use one.
	     Keys listed in this file will be refused for public key authenti-
	     cation.  Note that	if this	file is	not readable, then public key
	     authentication will be refused for	all users.  Keys may be	speci-
	     fied 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	sec-
	     tion in ssh-keygen(1).

     RhostsRSAAuthentication
	     Specifies whether rhosts or /etc/hosts.equiv authentication to-
	     gether with successful RSA	host authentication is allowed.	 The
	     default is	"no".  This option applies to protocol version 1 only.

     RSAAuthentication
	     Specifies whether pure RSA	authentication is allowed.  The	de-
	     fault is "yes".  This option applies to protocol version 1	only.

     ServerKeyBits
	     Defines the number	of bits	in the ephemeral protocol version 1
	     server key.  The default and minimum value	is 1024.

     StreamLocalBindMask
	     Sets the octal file creation mode mask (umask) used when creating
	     a Unix-domain socket file for local or remote port	forwarding.
	     This option is only used for port forwarding to a Unix-domain
	     socket file.

	     The 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.

     StreamLocalBindUnlink
	     Specifies whether to remove an existing Unix-domain socket	file
	     for local or remote port forwarding before	creating a new one.
	     If	the socket file	already	exists and StreamLocalBindUnlink 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".

     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".  Note that this does not apply to ChrootDirectory, whose
	     permissions and ownership are checked unconditionally.

     Subsystem
	     Configures	an external subsystem (e.g. file transfer daemon).
	     Arguments should be a subsystem name and a	command	(with optional
	     arguments)	to execute upon	subsystem request.

	     The command sftp-server(8)	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.

     SyslogFacility
	     Gives the facility	code that is used when logging messages	from
	     sshd(8).  The possible values are:	DAEMON,	USER, AUTH, LOCAL0,
	     LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.  The de-
	     fault is AUTH.

     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 tempo-
	     rarily, 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.

	     The 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".

     TrustedUserCAKeys
	     Specifies a file containing public	keys of	certificate authori-
	     ties that are trusted to sign user	certificates for authentica-
	     tion, or "none" 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 authentica-
	     tion 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).

     UseBlacklist
	     Specifies whether sshd(8) attempts	to send	authentication success
	     and failure messages to the blacklistd(8) daemon.	The default is
	     "no".

     UseDNS  Specifies whether sshd(8) should look up the remote host name,
	     and to check that the resolved host name for the remote IP	ad-
	     dress maps	back to	the very same IP address.

	     If	this option is set to "no", then only addresses	and not	host
	     names may be used in ~/.ssh/known_hosts from and sshd_config
	     Match Host	directives.  The default is "yes".

     UseLogin
	     Specifies whether login(1)	is used	for interactive	login ses-
	     sions.  The default is "no".  Note	that login(1) is never used
	     for remote	command	execution.  Note also, that if this is en-
	     abled, 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.

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

     UsePrivilegeSeparation
	     Specifies whether sshd(8) separates privileges by creating	an un-
	     privileged	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	con-
	     taining any corruption within the unprivileged processes.	The
	     argument must be "yes", "no", or "sandbox".  If
	     UsePrivilegeSeparation is set to "sandbox"	then the pre-authenti-
	     cation unprivileged process is subject to additional restric-
	     tions.  The default is "sandbox".

     VersionAddendum
	     Optionally	specifies additional text to append to the SSH proto-
	     col banner	sent by	the server upon	connection.  The default is
	     "FreeBSD-20161230".  The value "none" may be used to disable
	     this.

     X11DisplayOffset
	     Specifies the first display number	available for sshd(8)'s	X11
	     forwarding.  This prevents	sshd from interfering with real	X11
	     servers.  The default is 10.

     X11Forwarding
	     Specifies whether X11 forwarding is permitted.  The argument must
	     be	"yes" or "no".	The default is "yes".

	     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 below), though this is not	the default.  Addi-
	     tionally, the authentication spoofing and authentication data
	     verification and substitution occur on the	client side.  The se-
	     curity risk of using X11 forwarding is that the client's X11 dis-
	     play 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 pro-
	     tect 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.  X11 forwarding is automatically disabled if UseLogin
	     is	enabled.

     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 wild-
	     card address.  The	argument must be "yes" or "no".	 The default
	     is	"yes".

     XAuthLocation
	     Specifies the full	pathname of the	xauth(1) program, or "none" to
	     not use one.  The default is /usr/local/bin/xauth.

TIME FORMATS
     sshd(8) command-line arguments and	configuration file options that	spec-
     ify time may be expressed using a sequence	of the form: time[qualifier],
     where time	is a positive integer value and	qualifier is one of the	fol-
     lowing:

	   <none>  seconds
	   s | S   seconds
	   m | M   minutes
	   h | H   hours
	   d | D   days
	   w | W   weeks

     Each member of the	sequence is added together to calculate	the total time
     value.

     Time format examples:

	   600	   600 seconds (10 minutes)
	   10m	   10 minutes
	   1h30m   1 hour 30 minutes (90 minutes)

FILES
     /etc/ssh/sshd_config
	     Contains configuration data for sshd(8).  This file should	be
	     writable by root only, but	it is recommended (though not neces-
	     sary) that	it be world-readable.

SEE ALSO
     sshd(8)

AUTHORS
     OpenSSH is	a derivative of	the original and free ssh 1.2.12 release by
     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
     de	Raadt and Dug Song removed many	bugs, re-added newer features and cre-
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.  Niels Provos and Markus Friedl contributed support
     for privilege separation.

BSD			       February	17, 2016			   BSD

NAME | SYNOPSIS | DESCRIPTION | TIME FORMATS | FILES | SEE ALSO | AUTHORS

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