sshd_config.openssh-7.9-alphabetical

#
# File: sshd_config
#
# Edition: sshd(8) v7.9 compiled-default
#
# Sort Order: Alphabetical by Keywords
#
# Description: OpenSSH server daemon configuration file
#
# The possible keywords and their meanings are as
# follows (note that keywords 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 and SetEnv in ssh_config(5)
# for how to configure the client.  The TERM
# environ ment 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.
#
# NOTE: Debian openssh-server package sets AcceptEnv
# option to 'LANG LC_*' as standard in
# /etc/ssh/sshd_config # which are not the default in
# sshd(8):
AcceptEnv LANG
AcceptEnv LC_*

# AddressFamily specifies which address family should
# be used by sshd(8).  Valid arguments are any (the
# default), inet (use IPv4 only), or inet6 (use IPv6
# only).
AddressFamily any

# AllowAgentForwarding specifies whether ssh-agent(1)
# forwarding is permitted.  The default 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.
AllowAgentForwarding no

# AllowGroups 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.
AllowGroups ssh

# AllowStreamLocalForwarding specifies whether
# StreamLocal (Unix-domain socket) forwarding is
# permitted.  The available options are yes (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: Disabling StreamLocal forwarding does not
# improve security unless users are also denied shell
# access, as they can always install their own
# forwarders.
AllowStreamLocalForwarding yes
######################################################3

# AllowTcpForwarding specifies whether TCP forwarding
# is permitted.  The available options are yes (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: disabling TCP forwarding does not improve
# security unless users are also denied shell access,
# as they can always install their own forwarders.
AllowTcpForwarding no


# AllowUsers 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.  HOST criteria may
# additionally contain addresses to match in CIDR
# address/masklen format.  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 lists of comma-separated
# authentication method names, or by the single string
# any 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 or pam 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".
AuthenticationMethods any


# 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 others and specified by an absolute path.
# Arguments to AuthorizedKeysCommand accept the tokens
# described in the TOKENS section of sshd_config(5)
# man page.  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)).  If a key supplied by
# AuthorizedKeysCommand does not successfully
# authenticate and authorize the user then public key
# authentication continues using the usual
# AuthorizedKeysFile files.  By default, no
# AuthorizedKeysCommand is run.
#
# AuthorizedKeysCommand accepts the tokens %%, %f, %h,
# %k, %t, %U, and %u.
AuthorizedKeysCommand none

# 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.
AuthorizedKeysCommandUser none

# AuthorizedKeysFile specifies the file that contains
# the public keys used for user authentication.  The
# format is described in the AUTHORIZED_KEYS FILE
# FORMAT section of sshd(8).  Arguments to
# AuthorizedKeysFile 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".
#
# AuthorizedKeysFile accepts the tokens %%, %h, %U, and %u.
AuthorizedKeysFile %h/.ssh/authorized_keys

# AuthorizedPrincipalsCommand specifies a program to
# be used to generate the list of allowed certificate
# principals as per AuthorizedPrincipalsFile.  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.
#
# AuthorizedPrincipalsCommand accepts the tokens %%,
# %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.
AuthorizedPrincipalsCommand none


# AuthorizedPrincipalsCommandUser specifies the user
# under whose account the AuthorizedPrincipalsCommand
# 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.
AuthorizedPrincipalsCommanduser none

# 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.
#
# 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).
#
# AuthorizedPrincipalsFile accepts the tokens %%, %h, %U, and %u.
AuthorizedPrincipalsFile none

# Banner sends the contents of the specified file the
# remote user before authentication is allowed.  If
# the argument is none then no banner is displayed.
# By default, no banner is displayed.
Banner /etc/issue.net

# CASignatureAlgorithms specifies which algorithms are
# allowed for signing of certificates by certificate
# authorities (CAs).  The default is:
#
#     ecdsa-sha2-nistp256.ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
#     ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
#
# Certificates signed using other algorithms will not
# be accepted for public key or host-based
# authentication.
CASignatureAlgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa

# ChallengeResponseAuthentication specifies whether
# challenge-response authentication is allowed (e.g.
# via PAM).  The default is yes.
#
# NOTE: Debian openssh-server package sets
# ChallengeResponseAuthentication option to 'no'
# as standard in /etc/ssh/sshd_config # which are
# not the default in sshd(8):
ChallengeResponseAuthentication yes

# ChrootDirectory specifies the pathname of a
# directory to chroot(2) to after authentication.
# At session startup sshd(8) checks that all
# components 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.
# Arguments to ChrootDirectory 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 inprocess
# 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.
#
# ChrootDirectory accepts the tokens %%, %h, %U, and %u.
#
# The default is none, indicating not to chroot(2).
ChrootDirectory none

# 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.  If the specified
# value begins with a ‘-’ character, then the
# specified ciphers (including wildcards) will be
# removed from 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
#     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
#
# The list of available ciphers may also be obtained
# using "ssh -Q cipher".
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com

# 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.
ClientAliveCountMax 2

# 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.
ClientAliveInterval 300

# Compression specifies whether compression is enabled
# after the user has authenticated successfully.  The
# argument must be yes, delayed (a legacy synonym for
# yes) or no.  The default is yes.
Compression no

# DebianBanner specifies whether the distribution-
# specified extra version suffix is included during
# initial protocol handshake.  The default is yes.
DebianBanner no

# DenyGroups 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.
#
DenyGroups root

# DenyUsers 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.  HOST criteria may additionally
# contain addresses to match in CIDR address/masklen
# format.  The allow/deny directives are processed in
# the following order:
#
#     DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.
DenyUsers root

# DisableForwarding disables all forwarding features,
# including X11, ssh-agent(1), TCP and StreamLocal.
# This option overrides all other forwarding-related
# options and may simplify restricted configurations.
DisableForwarding no

# ExposeAuthInfo writes a temporary file containing a
# list of authentication methods and public
# credentials (e.g. keys) used to authenticate the
# user.  The location of the file is exposed to the
# user session through the SSH_USER_AUTH environment
# variable.  The default is no.
ExposeAuthInfo no

# FingerprintHash specifies the hash algorithm used
# when logging key fingerprints.  Valid options are:
# md5 and sha256.  The default is sha256.
FingerprintHash 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.
ForceCommand 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
# 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.
GatewayPorts no

# GSSAPIAuthentication specifies whether user
# authentication based on GSSAPI is allowed.
# The default is no.
GSSApiAuthentication no

# GSSAPICleanupCredentials specifies whether to
# automatically destroy the user's credentials cache
# on logout.  The default is yes.
GSSApiCleanupCredentials yes

# GSSAPIKeyExchange specifies whether key exchange
# based on GSSAPI is allowed. GSSAPI key exchange
# doesn't rely on ssh keys to verify host identity.
# The default is no.
GSSApiKeyExchange no

# 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 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.
GSSApiStrictAcceptorCheck yes

# GSSAPIStoreCredentialsOnRekey controls whether
# the user's GSSAPI credentials should be updated
# following a successful connection rekeying. This
# option can be used to accepted renewed or updated
# credentials from a compatible client.
# The default is no.
GSSApiStoreCredentialsOnRekey no

# HostbasedAcceptedKeyTypes specifies the key types
# that will be accepted for hostbased authentication
# as a list of comma-separated patterns.  Alternately
# if the specified value begins with a ‘+’ character,
# then the specified key types will be appended to
# the default set instead of replacing them.  If the
# specified value begins with a ‘-’ character, then
# the specified key types (including wildcards) will
# be removed from the default set instead of
# replacing 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,
#     rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
#     ssh-rsa-cert-v01@openssh.com,
#     ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
#     ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
#
# The list of available key types may also be obtained
# using "ssh -Q key".
HostbasedAcceptedKeyTypes 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,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa

# HostbasedAuthentication specifies whether rhosts or
# /etc/hosts.equiv authentication together with
# successful public key client host authentication is
# allowed (host-based authentication).  The default
# is no.
HostbasedAuthentication 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.  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.
HostbasedUsesNameFromPacketOnly no

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

# HostKey specifies a file containing a private host
# key used by SSH.  The defaults are
#     /etc/ssh/ssh_host_ecdsa_key,
#     /etc/ssh/ssh_host_ed25519_key and
#     /etc/ssh/ssh_host_rsa_key.
# NOTE: 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).
HostKey /etc/ssh/ssh_host_ed25519_key
HostKey /etc/ssh/ssh_host_rsa_key

# HostKeyAgent identifies the UNIX-domain socket used
# to communicate with an agent that has access to the
# private host keys.  If the string "SSH_AUTH_SOCK" is
# specified, the location of the socket will be read
# from the SSH_AUTH_SOCK environment variable.
HostKeyAgent none

# 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,
#     rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
#     ssh-rsa-cert-v01@openssh.com,
#     ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
#     ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
#
# The list of available key types may also be obtained
# using "ssh -Q key".
HostKeyAlgorithms 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,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa

# IgnoreRhosts specifies that .rhosts and .shosts
# files will not be used in HostbasedAuthentication.
#
# /etc/hosts.equiv and /etc/ssh/shosts.equiv are still
# used.  The default is yes.
IgnoreRHosts yes

# IgnoreUserKnownHosts specifies whether sshd(8)
# should ignore the user's ~/.ssh/known_hosts during
# HostbasedAuthentication and use only the system-wide
# known hosts file /etc/ssh/known_hosts.  The default
# is no.
IgnoreUserKnownHosts no

# IPQoS specifies the IPv4 type-of-service or DSCP
# class for the connection.  Accepted values are af11,
# af12, af13, af21, af22, af23, af31, af32, af33,
# af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5, cs6,
# cs7, ef, lowdelay, throughput, reliability, 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 lowdelay for interactive
# sessions and throughput for non-interactive sessions.
IPQoS lowdelay throughput

# 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).
KbdInteractiveAuthentication 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.
KerberosAuthentication 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.
KerberosOrLocalPasswd yes

     KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache file on logout.  The default is yes.
KerberosTicketCleanup 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.  If the specified value begins
# with a ‘-’ character, then the specified methods
# (including wildcards) will be removed from the
# default set instead of replacing them.  The
# supported algorithms are:
#
#     curve25519-sha256
#     curve25519-sha256@libssh.org
#     diffie-hellman-group1-sha1
#     diffie-hellman-group14-sha1
#     diffie-hellman-group14-sha256
#     diffie-hellman-group16-sha512
#     diffie-hellman-group18-sha512
#     diffie-hellman-group-exchange-sha1
#     diffie-hellman-group-exchange-sha256
#     ecdh-sha2-nistp256
#     ecdh-sha2-nistp384
#     ecdh-sha2-nistp521
#
# The default is:
#
#     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,diffie-hellman-group14-sha1
#
# The list of available key exchange algorithms may
# also be obtained using "ssh -Q kex".
#
# Need to execute the following commands for a safer KexAlgorithms
#     ssh-keygen -G moduli-2048.candidates -b 2048
#     ssh-keygen -T moduli-2048 -f moduli-2048.candidates
#
KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group14-sha256

# ListenAddress specifies the local addresses sshd(8)
# should listen on.  The following forms may be used:
#
#     ListenAddress 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).
ListenAddress 0.0.0.0:22
ListenAddress [::]:22

# LoginGraceTime disconnects after this time if the
# user has not successfully logged into the server.
# If the value is 0, there is no time limit.
# The default is 120 seconds.
LoginGraceTime 35

# 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.
LogLevel VERBOSE

# MACs specifies the available MAC (message
# authentication code) algorithms.  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.  If the
# specified value begins with a ‘-’ character, then
# the specified algorithms (including wildcards) will
# be removed from the default set instead of replacing
# them.
#
# The algorithms that contain "-etm" calculate the MAC
# after encryption (encrypt-then-mac).  These are
# considered safer and their use recommended.  The
# supported MACs are:
#
#     hmac-md5
#     hmac-md5-96
#     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-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 "ssh -Q mac".
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com

# 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, 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: 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, ClientAliveCountMax,
#     ClientAliveInterval, DenyGroups, DenyUsers,
#     ForceCommand, GatewayPorts, GSSAPIAuthentication,
#     HostbasedAcceptedKeyTypes,
#     HostbasedAuthentication,
#     HostbasedUsesNameFromPacketOnly, IPQoS,
#     KbdInteractiveAuthentication,
#     KerberosAuthentication, LogLevel, MaxAuthTries,
#     MaxSessions, PasswordAuthentication,
#     PermitEmptyPasswords, PermitListen, PermitOpen,
#     PermitRootLogin, PermitTTY, PermitTunnel,
#     PermitUserRC, PubkeyAcceptedKeyTypes,
#     PubkeyAuthentication, RekeyLimit, RevokedKeys,
#     RDomain, SetEnv, 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.
MaxAuthtries 3

# 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 forwarding.
# The default is 10.
MaxSessions 1

# 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 10:30:100.
#
# 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).
MaxStartups 10:30:100

# PasswordAuthentication specifies whether password
# authentication is allowed.  The default is yes.
PasswordAuthentication yes

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

# PermitListen specifies the addresses/ports on which a
# remote TCP port forwarding may listen.  The listen
# specification must be one of the following forms:
#
#     PermitListen port
#     PermitListen host:port
#
# Multiple 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: the GatewayPorts option may further restrict
#       which addresses may be listened on.
# NOTE: ssh(1) will request a listen host of “localhost”
#       if no listen host was specifically requested,
#       and this this name is treated differently to
#       explicit localhost addresses of “127.0.0.1”
#       and “::1”.
PermitListen any

# PermitOpen specifies the destinations to which TCP
# port forwarding is permitted.  The forwarding
# specification must be one of the following forms:
#
#     PermitOpen host:port
#     PermitOpen IPv4_addr:port
#     PermitOpen [IPv6_addr]:port
#
# Multiple 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.  By default all port forwarding
# requests are permitted.
PermitOpen any

# PermitRootLogin specifies whether root can log in
# using ssh(1).  The argument must be yes,
# 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.
PermitRootlogin no

# PermitTTY specifies whether pty(4) allocation is
# permitted.  The default is yes.
PermitTTY yes

# 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.  The default is no.
#
# Independent of this setting, the permissions of the
# selected tun(4) device must allow access to the user.
PermitTunnel no

# PermitUserEnvironment specifies whether
# ~/.ssh/environment and environment= 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.
PermitUserEnvironment no

# PermitUserRC specifies whether any ~/.ssh/rc file
# is executed.  The default is yes.
PermitUserRc yes

# PidFile specifies the file that contains the process
# ID of the SSH daemon, or none to not write one.
# The default is /run/sshd.pid.
PidFile /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.
Port 22

# 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.
PrintLastLog 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.
#
# NOTE: Debian openssh-server package sets X11Forwarding
# option to 'no' as standard in
# /etc/ssh/sshd_config which are not the default in
# sshd(8):
PrintMotd yes

# PubkeyAcceptedKeyTypes specifies the key types that
# will be accepted for public key authentication as a
# list of comma-separated patterns.  Alternately if
# the specified value begins with a ‘+’ character,
# then the specified key types will be appended to
# the default set instead of replacing them.  If the
# specified value begins with a ‘-’ character, then
# the specified key types (including wildcards) will
# be removed from the default set instead of replacing
# 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,
#     rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,
#     ssh-rsa-cert-v01@openssh.com,
#     ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
#     ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
#
# The list of available key types may also be obtained
# using "ssh -Q key".
PubkeyAcceptedKeyTypes 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,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa

# PubkeyAuthentication specifies whether public key
# authentication is allowed.  The default is yes.
PubkeyAuthentication yes

# RekeyLimit specifies the maximum amount of data that
# may be transmitted before the session key is
# renegotiated, optionally followed a maximum amount
# of time that may pass before the session key is
# renegotiated.  The first argument is specified in
# bytes and may have a suffix of ‘K’, ‘M’, or ‘G’ to
# indicate Kilobytes, Megabytes, or Gigabytes,
# respectively.  The default is between ‘1G’ and ‘4G’,
# depending on the cipher.  The optional second value
# is specified in seconds and may use any of the
# units documented in the TIME FORMATS section.  The
# default value for RekeyLimit is default none,
# which means that rekeying is performed after the
# cipher's default amount of data has been sent or
# received and no time based rekeying is done.
RekeyLimit 0 0

# RevokedKeys specifies revoked public keys file, or
# none 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).
RevokedKeys none

# RDomain specifies an explicit routing domain that is
# applied after authentication has completed.  The
# user session, as well and any forwarded or listening
# IP sockets, will be bound to this rdomain(4).  If
# the routing domain is set to %D, then the domain in
# which the incoming connection was received will be
# applied.
# RDomain accepts the token %D.
RDomain none

     SetEnv specifies one or more environment variables to set in child sessions started by sshd(8) as “NAME=VALUE”.  The environment value may be quoted (e.g. if it contains whitespace characters).  Environment variables set by SetEnv override the default environment and any variables specified by the user via AcceptEnv or PermitUserEnvironment.

# 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.
StreamLocalBindMask 0177

# 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.
StreamLocalBindUnlink 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.
StrictModes yes

# 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 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.
#
# NOTE: Debian openssh-server package sets Subsystem
# option to 'sftp /usr/lib/openssh/sftp-server' as
# standard in /etc/ssh/sshd_config which are not
# the default in sshd(8):
Subsystem sftp /usr/lib/openssh/sftp-server

# 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 default is AUTH.
SyslogFacility 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 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.
#
# 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.
#
# This option was formerly called KeepAlive.
TcpKeepAlive no

# TrustedUserCAKeys specifies a file containing public
# keys of certificate authorities that are trusted to
# sign user certificates for authentication, 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 authentication for any user
# listed in the certificate's principals list.
# NOTE: 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).
TrustedUserCAKeys none

# UseDNS specifies whether sshd(8) should look up the
# remote host name, and to check that the resolved
# host name for the remote IP address maps back to
# the very same IP address.
#
# If 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.
UseDns 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.
#
# NOTE: Debian openssh-server package sets UsePAM
# option to 'yes' as standard in
# /etc/ssh/sshd_config which are not the default in
# sshd(8):
UsePAM no

# VersionAddendum optionally specifies additional text
# to append to the SSH protocol banner sent by the
# server upon connection.  The default is none.
VersionAddendum none

# 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.
X11DisplayOffset 10

# X11Forwarding specifies whether X11 forwarding is
# permitted.  The argument must be yes 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.
#
# NOTE: Debian openssh-server package sets X11Forwarding
# option to 'yes' as standard in
# /etc/ssh/sshd_config which are not the default in
# sshd(8):
X11Forwarding 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.  The argument must be yes or no.  The
# default is yes.
X11UseLocalhost yes

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