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SecureBox Pro
Secure shell application, terminal screens and auxiliary commands for Android OS
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Documents </>
Manual pages "File Formats and Conventions (5)" </>
SSHD_CONFIG(5) |
File Formats Manual |
SSHD_CONFIG(5) |
sshd_config —
Secure shell daemon configuration file
sshd(8) reads configuration data from
[APPDATA]/etc/sshd_config (or the file specified
with -f on the command line). The file contains
keyword-argument pairs, one per line. Unless noted otherwise, for each
keyword, the first obtained value will be used. Lines starting with
‘# ’ and empty lines are interpreted as
comments. Arguments may optionally be enclosed in double quotes (") in
order to represent arguments containing spaces. Configuration options may be
separated by whitespace or optional whitespace and exactly one
‘= ’; the latter format is useful to
avoid the need to quote whitespace when specifying configuration
options.
The possible keywords and their meanings are as follows (note that
keywords are case-insensitive and arguments are case-sensitive):
AcceptedAlgorithms
- Specifies the publickey algorithms as a comma-separated pattern list that
will be announced to client if client supports extension negotiation
mechanism. See PATTERNS in
ssh_config(5) for more information on patterns. The
default “*” will announce all algorithms. Note algorithms
that use X.509 certificates depend from option
X509KeyAlgorithm . The list of available key
algorithms may also be obtained using "ssh -Q key".
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 environment variable is always accepted
whenever the client requests a pseudo-terminal as it is required by the
protocol. Variables are specified by name, which may contain the wildcard
characters ‘* ’ and
‘? ’. Multiple environment variables
may be separated by whitespace or spread across multiple
AcceptEnv directives. Be warned that some
environment variables could be used to bypass restricted user
environments. For this reason, care should be taken in the use of this
directive. The default is not to accept any environment variables.
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).
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.
AllowedCertPurpose
- The intended use for the X.509 client certificate. Without this option no
chain verification will be done. Currently accepted uses are case
insensitive:
-
sslclient
| SSL
client |
SSL_client
|
client
- only SSL-client purpose
-
any
| Any
Purpose |
Any_Purpose
|
AnyPurpose
- allow any purpose
-
skip
| ''
(empty)
- do not check purpose
The default is sslclient .
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 groups directives are processed
in the following order:
DenyGroups ,
AllowGroups .
See PATTERNS in
ssh_config(5) for more information on patterns. This
keyword may appear multiple times in sshd_config
with each instance appending to the list.
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 that
disabling StreamLocal forwarding does not improve security unless users
are also denied shell access, as they can always install their own
forwarders.
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 that
disabling TCP forwarding does not improve security unless users are also
denied shell access, 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. HOST
criteria may additionally contain addresses to match in CIDR
address/masklen format. The allow/deny users directives are processed in
the following order:
DenyUsers ,
AllowUsers .
See PATTERNS in
ssh_config(5) for more information on patterns. This
keyword may appear multiple times in sshd_config
with each instance appending to the list.
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".
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. If no arguments
are specified then the username of the target user is used.
The program should produce on standard output zero or more
lines of authorized_keys output (see AUTHORIZED_KEYS
in sshd(8)).
AuthorizedKeysCommand is tried after the usual
AuthorizedKeysFile files and will not be
executed if a matching key is found there. By default, no
AuthorizedKeysCommand is run.
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 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".
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.
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.
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).
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.
CACertificateFile
- “X509 store” option: This file contain multiple certificates
of certificate signers in PEM format concatenated together. The default is
[APPDATA]/etc/ca/ca-bundle.crt.
CACertificatePath
- “X509 store” option: “Hash dir” with
certificates of certificate signers. Each certificate should be stored in
separate file with name [HASH].[NUMBER], where [HASH] is certificate hash
value and [NUMBER] is an integer starting from zero. The default is
[APPDATA]/etc/ca/crt.
CAldapVersion
- “X509 store” option: Specifies LDAP protocol version. The
default is not specified and depend from LDAP library.
CAldapURL
- “X509 store” option: Specifies hostport and dn(distinguished
name) of LDAP URLs (Uniform Resource Locators) as detailed in RFC 2255.
The rest of URL is build internally. Because of options parser limitation
use ‘%3D’ instead of ‘=’ ! LDAP initialization
method may require URL to be escaped, i.e. use ‘%2C’ instead
of ‘,’ (comma). Escaped URL don't depend from LDAP
initialization method.
CARevocationFile
- “X509 store” option: This file contain multiple
“Certificate Revocation List” (CRL) of certificate signers
in PEM format concatenated together. The default is
[APPDATA]/etc/ca/ca-bundle.crl.
CARevocationPath
- “X509 store” option: “Hash dir” with
“Certificate Revocation List” (CRL) of certificate signers.
Each CRL should be stored in separate file with name [HASH].r[NUMBER],
where [HASH] is CRL hash value and [NUMBER] is an integer starting from
zero. The default is [APPDATA]/etc/ca/crl.
CASignatureAlgorithms
- Specifies which algorithms are allowed for signing of custom certificates
by custom certificate authorities (CAs). The default is:
ssh-ed25519,
ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
rsa-sha2-512,rsa-sha2-256,ssh-rsa
If the specified list begins with a ‘+’
character, then the specified algorithms will be appended to the default
set instead of replacing them. If the specified list begins with a
‘-’ character, then the specified algorithms (including
wildcards) will be removed from the default set instead of replacing
them.
Custom certificates signed using other algorithms will not be
accepted for public key or host-based authentication.
ChannelTimeout
- Specifies whether and how quickly sshd(8) should close
inactive channels. Timeouts are specified as one or more
“type=interval” pairs separated by whitespace, where the
“type” must be the special keyword “global” or
a channel type name from the list below, optionally containing wildcard
characters.
The timeout value “interval” is specified in
seconds or may use any of the units documented in the
TIME FORMATS section. For
example, “session=5m” would cause interactive sessions to
terminate after five minutes of inactivity. Specifying a zero value
disables the inactivity timeout.
The special timeout “global” applies to all
active channels, taken together. Traffic on any active channel will
reset the timeout, but when the timeout expires then all open channels
will be closed. Note that this global timeout is not matched by
wildcards and must be specified explicitly.
The available channel type names include:
agent-connection
- Open connections to ssh-agent(1).
-
direct-tcpip ,
direct-streamlocal@openssh.com
- Open TCP or Unix socket (respectively) connections that have been
established from a ssh(1) local forwarding, i.e.
LocalForward or
DynamicForward .
-
forwarded-tcpip ,
forwarded-streamlocal@openssh.com
- Open TCP or Unix socket (respectively) connections that have been
established to a sshd(8) listening on behalf of a
ssh(1) remote forwarding, i.e.
RemoteForward .
session
- The interactive main session, including shell session, command
execution, scp(1), sftp(1),
etc.
tun-connection
- Open
TunnelForward connections.
x11-connection
- Open X11 forwarding sessions.
Note that in all the above cases, terminating an inactive
session does not guarantee to remove all resources associated with the
session, e.g. shell processes or X11 clients relating to the session may
continue to execute.
Moreover, terminating an inactive channel or session does not
necessarily close the SSH connection, nor does it prevent a client from
requesting another channel of the same type. In particular, expiring an
inactive forwarding session does not prevent another identical
forwarding from being subsequently created.
The default is not to expire channels of any type for
inactivity.
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 group or others. 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 in-process sftp-server is used, though
sessions which use logging may require /dev/log
inside the chroot directory on some operating systems (see
sftp-server(8) for details).
For safety, it is very important that the directory hierarchy
be prevented from modification by other processes on the system
(especially those outside the jail). Misconfiguration can lead to unsafe
environments which sshd(8) cannot detect.
The default is none , indicating not to
chroot(2).
Ciphers
- Specifies the ciphers allowed. Multiple ciphers must be comma-separated.
If the specified list begins with a ‘+’ character, then the
specified ciphers will be appended to the default set instead of replacing
them. If the specified list begins with a ‘-’ character,
then the specified ciphers (including wildcards) will be removed from the
default set instead of replacing them. If the specified list begins with a
‘^’ character, then the specified ciphers will be placed at
the head of the default set.
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:
aes128-ctr,aes192-ctr,aes256-ctr,
aes128-gcm@openssh.com,aes256-gcm@openssh.com,
chacha20-poly1305@openssh.com
The list of available ciphers may also be obtained using
"ssh -Q cipher".
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 unresponsive.
The default value is 3. If
ClientAliveInterval is set to 15, and
ClientAliveCountMax is left at the default,
unresponsive SSH clients will be disconnected after approximately 45
seconds. Setting a zero ClientAliveCountMax
disables connection termination.
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 enabled after the user has authenticated
successfully. The argument must be
yes ,
delayed (a legacy synonym for
yes ) or no . The default is
yes .
DenyGroups
- This keyword can be followed by a list of group name patterns, separated
by spaces. Login is disallowed for users whose primary group or
supplementary group list matches one of the patterns. Only group names are
valid; a numerical group ID is not recognized. By default, login is
allowed for all groups. The allow/deny groups directives are processed in
the following order:
DenyGroups ,
AllowGroups .
See PATTERNS in
ssh_config(5) for more information on patterns. This
keyword may appear multiple times in sshd_config
with each instance appending to the list.
DenyUsers
- This keyword can be followed by a list of user name patterns, separated by
spaces. Login is disallowed for user names that match one of the patterns.
Only user names are valid; a numerical user ID is not recognized. By
default, login is allowed for all users. If the pattern takes the form
USER@HOST then USER and HOST are separately checked, restricting logins to
particular users from particular hosts. HOST criteria may additionally
contain addresses to match in CIDR address/masklen format. The allow/deny
users directives are processed in the following order:
DenyUsers , AllowUsers .
See PATTERNS in
ssh_config(5) for more information on patterns. This
keyword may appear multiple times in sshd_config
with each instance appending to the list.
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.
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 .
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 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 .
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 current
hostname. If set to no then the client may
authenticate against any service key stored in the machine's default
store. This facility is provided to assist with operation on multi homed
machines. The default is yes .
HostbasedAcceptedAlgorithms
- Option compatibility. See
HostbasedAlgorithms
HostbasedAcceptedKeyTypes
- Option compatibility. See
HostbasedAlgorithms
HostbasedAlgorithms
- Specifies the publickey algorithms that will be accepted in
“hostbased” authentication as a comma-separated pattern
list. See PATTERNS in ssh_config(5)
for more information on patterns. The default “*” will allow
all algorithms. Also algorithms has to be accepted by patterns of option
AcceptedAlgorithms . Note algorithms that use X.509
certificates depend from option X509KeyAlgorithm .
The list of available key algorithms may also be obtained using "ssh
-Q key".
HostbasedAuthentication
- Specifies whether rhosts or /etc/hosts.equiv authentication together with
successful public key client host authentication is allowed (host-based
authentication). Also secure shell uses equavalient shosts and
[APPDATA]/etc/shosts.equiv. The default is
no .
HostbasedUsesNameFromPacketOnly
- Specifies whether or not the server will attempt to perform a reverse name
lookup when matching the name in the ~/.shosts,
~/.rhosts,
/etc/hosts.equiv, and
[APPDATA]/etc/shosts.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 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 [APPDATA]/etc/ssh_host_ecdsa_key,
[APPDATA]/etc/ssh_host_ed25519_key and
[APPDATA]/etc/ssh_host_rsa_key.
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.
For RSA, ECDSA, or Ed25519 host key file may contain X.509
certificate that match it. In addition file may contain extra X.509
certificates. Extra certificates along with certificates from X.509
store are used to build chain of certificates leading to a trusted
certificate authority if required by public key algorithm format.
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 the string
"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
“*” allows all algorithms. The list of available key
algorithms may also be obtained using "ssh -Q key".
IgnoreRhosts
- Specifies whether to ignore per-user .rhosts and
.shosts files during
HostbasedAuthentication . The system-wide
/etc/hosts.equiv and
[APPDATA]/etc/shosts.equiv are still used
regardless of this setting.
Accepted values are yes (the default)
to ignore all per-user files, rhosts-only to
allow the use of .shosts but to ignore
.rhosts or no to allow
both .rhosts and
.shosts.
IgnoreUserKnownHosts
- Specifies whether sshd(8) should ignore the user's
~/.ssh/known_hosts during
HostbasedAuthentication and use only the
system-wide known hosts file
[APPDATA]/etc/ssh_known_hosts. The default is
“no”.
Include
- Include the specified configuration file(s). Multiple pathnames may be
specified and each pathname may contain glob(7)
wildcards that will be expanded and processed in lexical order. Files
without absolute paths are assumed to be in
/etc/ssh. An
Include
directive may appear inside a Match block to
perform conditional inclusion.
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 ,
le , lowdelay ,
throughput , reliability , a
numeric value, or none to use the operating system
default. This option may take one or two arguments, separated by
whitespace. If one argument is specified, it is used as the packet class
unconditionally. If two values are specified, the first is automatically
selected for interactive sessions and the second for non-interactive
sessions. The default is af21 (Low-Latency Data)
for interactive sessions and cs1 (Lower Effort)
for non-interactive sessions.
KbdInteractiveAuthentication
- Specifies whether to allow keyboard-interactive authentication. All
authentication styles from login.conf(5) are supported.
The argument to this keyword must be
yes or
no . The default is yes .
ChallengeResponseAuthentication is a deprecated
alias for this.
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 password 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 permitted KEX (Key Exchange) algorithms that the server will
offer to clients. The ordering of this list is not important, as the
client specifies the preference order. Multiple algorithms must be
comma-separated.
If the specified list begins with a ‘+’
character, then the specified algorithms will be appended to the default
set instead of replacing them. If the specified list begins with a
‘-’ character, then the specified algorithms (including
wildcards) will be removed from the default set instead of replacing
them. If the specified list begins with a ‘^’ character,
then the specified algorithms will be placed at the head of the default
set.
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
- sntrup761x25519-sha512 (if build)
- sntrup761x25519-sha512@openssh.com (if build)
- mlkem768x25519-sha256 (if build)
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,
sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com,
mlkem768x25519-sha256,
diffie-hellman-group14-sha1
The list of supported key exchange algorithms may also be
obtained using "ssh -Q kex".
KeyAllowSelfIssued
- Specifies whether only encoded public key or X.509 certificate listed in
AuthorizedKeysFile can allow self-issued X.509
certificate to be used for user authentication. The default is
“no”. Unsupported if daemon is build without “X509
store”.
A certificate (including self-issued) is accepted for user
authentication if encoded public key or encoded X.509 certificate or
distinguished name is listed in
AuthorizedKeysFile , if is valid and if is
verified by certificates from “X509 store”. See
verify(1). If option is set to “yes”
self-issued certificate is accepted when its public key match public key
extracted from entry in AuthorizedKeysFile . In
this case validity of certificate is not checked.
ListenAddress
- Specifies the local addresses sshd(8) should listen on.
The following forms may be used:
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).
LoginGraceTime
- The server disconnects after this time if the user has not successfully
logged in. If the value is 0, there is no time limit. The default is 120
seconds.
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.
LogVerbose
- Specify one or more overrides to
LogLevel . An
override consists of one or more pattern lists that matches the source
file, function and line number to force detailed logging for. For example,
an override pattern of:
kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*
would enable detailed logging
for line 1000 of kex.c, everything in the
kex_exchange_identification ()
function, and all code in the packet.c file.
This option is intended for debugging and no overrides are enabled by
default, i.e. default value is none .
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 list begins with a
‘+’ character, then the specified algorithms will be
appended to the default set instead of replacing them. If the specified
list begins with a ‘-’ character, then the specified
algorithms (including wildcards) will be removed from the default set
instead of replacing them. If the specified list begins with a
‘^’ character, then the specified algorithms will be placed
at the head of the default set.
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@openssh.com,umac-128@openssh.com,
hmac-sha2-256,hmac-sha2-512,hmac-sha1,
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
The list of available MAC algorithms may also be obtained
using "ssh -Q mac".
MandatoryCRL
- “X509 store” option: Specifies whether CRL must present in
store for all certificates in “certificate chain” with
attribute “X509v3 CRL Distribution Points”. The default is
no .
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 that the mask length
provided must be consistent with the address - it is an error to specify
a mask length that is too long for the address or one with bits set in
this host portion of the address. For example, 192.0.2.0/33 and
192.0.2.0/8, respectively.
Only a subset of keywords may be used on the lines following a
Match keyword. Available keywords are
AcceptEnv ,
AllowAgentForwarding ,
AllowGroups ,
AllowStreamLocalForwarding ,
AllowTcpForwarding ,
AllowUsers ,
AuthenticationMethods ,
AuthorizedKeysCommand ,
AuthorizedKeysCommandUser ,
AuthorizedKeysFile ,
AuthorizedPrincipalsCommand ,
AuthorizedPrincipalsCommandUser ,
AuthorizedPrincipalsFile ,
Banner ,
CASignatureAlgorithms ,
ChannelTimeout ,
ChrootDirectory ,
ClientAliveCountMax ,
ClientAliveInterval ,
DenyGroups , DenyUsers ,
DisableForwarding ,
ExposeAuthInfo ,
ForceCommand ,
GatewayPorts ,
GSSAPIAuthentication ,
HostbasedAlgorithms ,
HostbasedAuthentication ,
HostbasedUsesNameFromPacketOnly ,
IgnoreRhosts , Include ,
IPQoS ,
KbdInteractiveAuthentication ,
KerberosAuthentication ,
LogLevel , MaxAuthTries ,
MaxSessions ,
PAMServiceName ,
PasswordAuthentication ,
PermitEmptyPasswords ,
PermitListen ,
PermitOpen ,
PermitRootLogin ,
PermitTTY , PermitTunnel ,
PermitUserRC ,
PubkeyAlgorithms ,
PubkeyAuthentication ,
PubkeyAuthOptions ,
RefuseConnection ,
RekeyLimit , RevokedKeys ,
RDomain , SetEnv ,
StreamLocalBindMask ,
StreamLocalBindUnlink ,
TrustedUserCAKeys ,
UnusedConnectionTimeout ,
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 forwarding. The default is
10.
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).
ModuliFile
- Specifies the moduli(5) file that contains the
Diffie-Hellman groups used for the
“diffie-hellman-group-exchange-sha1” and
“diffie-hellman-group-exchange-sha256” key exchange methods.
The default is [APPDATA]/etc/moduli.
PAMServiceName
- Specifies the service name used for Pluggable Authentication Modules (PAM)
authentication, authorisation and session controls when
UsePAM is enabled. The default is
sshd .
PasswordAuthentication
- Specifies whether password authentication is allowed. The default is
yes .
PermitEmptyPasswords
- When password authentication is allowed, it specifies whether the server
allows login to accounts with empty password strings. The default is
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:
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 that the GatewayPorts option may further
restrict which addresses may be listened on. Note also that
ssh(1) will request a listen host of
“localhost” if no listen host was specifically requested,
and this name is treated differently to explicit localhost addresses of
“127.0.0.1” and “::1”.
PermitOpen
- Specifies the destinations to which TCP port forwarding is permitted. The
forwarding specification must be one of the following forms:
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. Otherwise, no pattern matching or
address lookups are performed on supplied names. 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 ,
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.
PermitTTY
- Specifies whether pty(4) allocation is permitted. The
default is
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.
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 .
PermitUserRC
- Specifies whether any ~/.ssh/rc file is executed.
The default is
yes .
PerSourceMaxStartups
- Specifies the number of unauthenticated connections allowed from a given
source address, or “none” if there is no limit. This limit
is applied in addition to
MaxStartups , whichever
is lower. The default is none .
PerSourceNetBlockSize
- Specifies the number of bits of source address that are grouped together
for the purposes of applying PerSourceMaxStartups limits. Values for IPv4
and optionally IPv6 may be specified, separated by a colon. The default is
32:128 , which means each address is considered
individually.
PidFile
- Specifies the file that contains the process ID of the SSH daemon, or
none to not write one. The default is
[APPDATA]/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 .
PubkeyAcceptedAlgorithms
- Option compatibility. See
PubkeyAlgorithms
PubkeyAcceptedKeyTypes
- Option compatibility. See
PubkeyAlgorithms
PubkeyAlgorithms
- Specifies the publickey algorithms that will be accepted for
“publickey” authentication as a comma-separated pattern
list. See PATTERNS in ssh_config(5)
for more information on patterns. The default
*
will allow all algorithms. Also algorithms has to be accepted by patterns
of option AcceptedAlgorithms . Note algorithms that
use X.509 certificates depend from
X509KeyAlgorithm and is enough patter to match one
of names set in X509KeyAlgorithm for a certain
key-type to enable all from that key-type. The list of available key
algorithms may also be obtained using "ssh -Q key".
PubkeyAuthentication
- Specifies whether public key authentication is allowed. The default is
yes .
RDomain
- Specifies an explicit routing domain that is applied after authentication
has completed. The user session, as well as 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.
RefuseConnection
- Indicates that sshd(8) should unconditionally terminate
the connection. This option is only really useful in a
Match block.
RekeyLimit
- Specifies the maximum amount of data that may be transmitted or received
before the session key is renegotiated, optionally followed by 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.
RequiredRSASize
- Specifies the minimum RSA key size (in bits) that
sshd(8) will accept. User and host-based authentication
keys smaller than this limit will be refused. The default is
1024 bits. Note that this limit may only be raised
from the default.
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 custom 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).
SetEnv
- Specifies one or more environment variables to set in child sessions
started by sshd(8) as “NAME=VALUE”.
Variables and their contents are specified as pattern-list. Lists may be
separated by whitespace or spread across multiple
SetEnv directives. 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 . These variables do not
override variables set in child session by daemon itself. Variables set by
daemon are described in
ENVIRONMENT
section of ssh(1).
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 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. It accepts the same command line arguments
as sftp-server and even though it is in-process,
settings such as LogLevel or
SyslogFacility do not apply to it and must be
set explicitly via command line arguments.
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
default 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 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 .
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 that certificates that lack a list of
principals will not be permitted for authentication using
TrustedUserCAKeys . For more details on
certificates, see the CERTIFICATES section in
ssh-keygen(1).
UnusedConnectionTimeout
- Specifies whether and how quickly sshd(8) should close
client connections with no open channels. Open channels include active
shell, command execution or subsystem sessions, connected network, socket,
agent or X11 forwardings. Forwarding listeners, such as those from the
ssh(1)
-R flag, are not
considered as open channels and do not prevent the timeout. The timeout
value is specified in seconds or may use any of the units documented in
the TIME FORMATS section.
Note that this timeout starts when the client connection
completes user authentication but before the client has an opportunity
to open any channels. Caution should be used when using short timeout
values, as they may not provide sufficient time for the client to
request and open its channels before terminating the connection.
The default none is to never expire
connections for having no open channels. This option may be useful in
conjunction with ChannelTimeout .
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.
UsePAM
- Enables the Pluggable Authentication Module interface. If set to
yes this will enable PAM authentication using
KbdInteractiveAuthentication and
PasswordAuthentication in addition to PAM account
and session module processing for all authentication types.
Because PAM keyboard-interactive authentication usually serves
an equivalent role to password authentication, you should disable either
PasswordAuthentication or
KbdInteractiveAuthentication .
If UsePAM is enabled, you will not be
able to run sshd(8) as a non-root user. The default is
no .
UsePrivilegeSeparation
- Specifies whether sshd(8) separates privileges by
creating an unprivileged child process to deal with incoming network
traffic. After successful authentication, another process will be created
that has the privilege of the authenticated user. The goal of privilege
separation is to prevent privilege escalation by containing any corruption
within the unprivileged processes. The argument must be
yes , no , or
sandbox . If
UsePrivilegeSeparation is set to
sandbox then the pre-authentication unprivileged
process is subject to additional restrictions. The default is
sandbox .
VACertificateFile
- File with X.509 certificates in PEM format concatenated together. In use
when
VAType is set to
ocspspec . The default value is ‘’
(empty). Certificates from that file explicitly trust ‘OCSP
Responder’ public key. They are used as trusted certificates in
addition to certificates from CACertificateFile
and CACertificatePath to verify responder
certificate.
ValidateFirst
- Specifies whether first to perform validation of X.509 certificate and
then authorization of public key. Process is applicable for x509v3-*
public key algorithms. The default is
no , i.e.
first key is authorized and then X.509 certificate is validated.
VAOCSPResponderURL
- ‘Access Location’ / ‘OCSP Service Locator’ URL
of the OCSP provider. In use when
VAType is set to
ocspspec .
VAType
- Specifies whether ‘Online Certificate Status Protocol’
(OCSP) is used to validate X.509 certificates. Accepted values are case
insensitive:
- none
- do not use OCSP to validate certificates;
- ocspcert
- validate only certificates that specify ‘OCSP Service
Locator’ URL;
- ocspspec
- use specified in the configuration ‘OCSP Responder’ to
validate all certificates.
The default is none .
VersionAddendum
- Optionally specifies additional text to append to the SSH protocol banner
sent by the server upon connection. The default is
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.
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.
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 .
X509KeyAlgorithm
- Specifies how X.509 certificates and signatures are encoded. It is
possible to have multiple algorithms in form specified in
X509 Key Algorithms
Format. Programs use the first listed for
ECDSA , Ed25519 , or
RSA key in signing and accept all listed.
The default for certificates with ECDSA keys is:
The default for certificates with Ed25519 keys is:
The default for certificates with RSA key is:
Note for EC curves nistp256, nistp384, and nistp521 correspond
crypto(3) library curves prime256v1, secp384r1, and
secp521r1. Support of EC curves depend from library version. See
ecparam(1) to find how to list curves supported by
library.
XAuthLocation
- Specifies the full pathname of the xauth(1) program, or
none to not use one. The default is
/usr/bin/xauth.
sshd(8) command-line arguments and configuration
file options that specify 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 following:
- ⟨
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)
Arguments to some keywords can make use of tokens, which are
expanded at runtime:
- %%
- A literal ‘%’.
- %C
- Identifies the connection endpoints, containing four space-separated
values: client address, client port number, server address, and server
port number.
- %D
- The routing domain in which the incoming connection was received (OS
specific).
- %F
- The fingerprint of the CA key.
- %f
- The fingerprint of the key or certificate.
- %h
- The home directory of the user.
- %i
- The key ID in the certificate.
- %K
- The base64-encoded CA key.
- %k
- The base64-encoded key or certificate for authentication.
- %s
- The serial number of the certificate.
- %T
- The type of the CA key.
- %t
- The key or certificate type.
- %U
- The numeric user ID of the target user.
- %u
- The username.
AuthorizedKeysCommand accepts the tokens
%%, %C, %D, %f, %h, %k, %t, %U, and %u.
AuthorizedKeysFile accepts the tokens %%,
%h, %U, and %u.
AuthorizedPrincipalsCommand accepts the
tokens %%, %C, %D, %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.
AuthorizedPrincipalsFile accepts the
tokens %%, %h, %U, and %u.
ChrootDirectory accepts the tokens %%, %h,
%U, and %u.
RDomain accepts the token %D.
sshd command-line arguments and
configuration file options that specify ‘X509 Key Algorithms’
expressed using a sequence of the form:
algorithm-name,digest-name[,signature-identifier],
where algorithm-name is name of public key algorithm,
digest-name is
rsa-sha1
- : RSA key and signature using the SHA-1 hash;
rsa-md5
- : RSA key and signature using the MD5 hash;
rsa2048-sha256
- : RSA key and signature using the SHA-256 hash as specified in “RFC
6187”;
ssh-sha256
-
ssh-sha384
-
ssh-sha512
- : ECDSA key and signature as specified in “RFC 6187”.
none
- : Ed25519 key with PureEdDSA signature as specified in “RFC
8032”.
and optional signature-identifier. When
signature-identifier is omitted
algorithm-name is used as identifier.
For compatibility with old versions following signatures are
supported:
Daemon sshd(8) and client ssh(1) switch
automatically to those signatures if is detected old version.
- [APPDATA]/etc/sshd_config
- Contains configuration data for sshd(8). This file
should be writable by root only, but it is recommended (though not
necessary) that it be world-readable.
PKIX-SSH 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 created 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.
Roumen Petrov contributed support for X.509
certificates.
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Copyright © 2018-2024 |
, Roumen Petrov |
Авторско право 2018-2024 |
, Румен Петров |
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