Enum ssh_cfg::SshOptionKey [−][src]
pub enum SshOptionKey {
Show 109 variants
Host,
AddKeysToAgent,
AddressFamily,
BatchMode,
BindAddress,
BindInterface,
CanonicalDomains,
CanonicalizeFallbackLocal,
CanonicalizeHostname,
CanonicalizeMaxDots,
CanonicalizePermittedCNAMEs,
CASignatureAlgorithms,
CertificateFile,
ChallengeResponseAuthentication,
CheckHostIP,
Cipher,
Ciphers,
ClearAllForwardings,
Compression,
CompressionLevel,
ConnectionAttempts,
ConnectTimeout,
ControlMaster,
ControlPath,
ControlPersist,
DynamicForward,
EnableSSHKeysign,
EscapeChar,
ExitOnForwardFailure,
FingerprintHash,
ForkAfterAuthentication,
ForwardAgent,
ForwardX11,
ForwardX11Timeout,
ForwardX11Trusted,
GatewayPorts,
GlobalKnownHostsFile,
GSSAPIAuthentication,
GSSAPIClientIdentity,
GSSAPIDelegateCredentials,
GSSAPIKeyExchange,
GSSAPIRenewalForcesRekey,
GSSAPITrustDns,
HashKnownHosts,
HostbasedAcceptedAlgorithms,
HostbasedAuthentication,
HostKeyAlgorithms,
HostKeyAlias,
Hostname,
HostName,
IdentitiesOnly,
IdentityAgent,
IdentityFile,
IgnoreUnknown,
Include,
IPQoS,
KbdInteractiveAuthentication,
KbdInteractiveDevices,
KexAlgorithms,
KnownHostsCommand,
LocalCommand,
LocalForward,
LogLevel,
LogVerbose,
MACs,
Match,
NoHostAuthenticationForLocalhost,
NumberOfPasswordPrompts,
PasswordAuthentication,
PermitLocalCommand,
PermitRemoteOpen,
PKCS11Provider,
Port,
PreferredAuthentications,
Protocol,
ProxyCommand,
ProxyJump,
ProxyUseFdpass,
PubkeyAcceptedAlgorithms,
PubkeyAuthentication,
RekeyLimit,
RemoteCommand,
RemoteForward,
RequestTTY,
RevokedHostKeys,
RhostsRSAAuthentication,
RSAAuthentication,
SecurityKeyProvider,
SendEnv,
ServerAliveCountMax,
ServerAliveInterval,
SessionType,
SetEnv,
SmartcardDevice,
StdinNull,
StreamLocalBindMask,
StreamLocalBindUnlink,
StrictHostKeyChecking,
SyslogFacility,
TCPKeepAlive,
Tunnel,
TunnelDevice,
UpdateHostKeys,
UsePrivilegedPort,
User,
UserKnownHostsFile,
VerifyHostKeyDNS,
VisualHostKey,
XAuthLocation,
}Expand description
SSH option keys inside the SSH configuration file.
Variants
Restricts the following declarations (up to the next Host keyword) to
be only for those hosts that match one of the patterns given after
the keyword.
If more than one pattern is provided, they should be separated
by whitespace. A single * as a pattern can be used to provide global
defaults for all hosts. The host is the hostname argument given on the
command line (i.e. the name is not converted to a canonicalized host
name before matching).
See Patterns for more information on patterns.
Specifies whether keys should be automatically added to a running ssh-agent(1).
If this option is set to yes and a key is loaded from a file, the key and its passphrase are added to the agent with the default lifetime, as if by ssh-add(1). If this option is set to ask, ssh(1) will require confirmation using the SSH_ASKPASS program before adding a key (see ssh-add(1) for details). If this option is set to confirm, each use of the key must be confirmed, as if the -c option was specified to ssh-add(1). If this option is set to no, no keys are added to the agent. Alternately, this option may be specified as a time interval using the format described in the TIME FORMATS section of sshd_config(5) to specify the key’s lifetime in ssh-agent(1), after which it will automatically be removed. The argument must be no (the default), yes, confirm (optionally followed by a time interval), ask or a time interval.
Specifies which address family to use when connecting.
Valid arguments are any, inet (use IPv4 only), or inet6 (use IPv6
only).
If set to yes, passphrase/password querying will be disabled.
This option is useful in scripts and other batch jobs where no user is
present to supply the password. The argument must be yes or no.
The default is no.
Use the specified address on the local machine as the source address of the connection.
Only useful on systems with more than one address. Note
that this option does not work if UsePrivilegedPort is set to yes.
Use the address of the specified interface on the local machine as the source address of the connection.
When CanonicalizeHostname is enabled, this option specifies the list of domain suffixes in which to search for the specified destination host.
Specifies whether to fail with an error when hostname canonicalization fails. The default, yes, will attempt to look up the unqualified hostname using the system resolver’s search rules. A value of no will cause ssh(1) to fail instantly if CanonicalizeHostname is enabled and the target hostname cannot be found in any of the domains specified by CanonicalDomains.
Controls whether explicit hostname canonicalization is performed.
The default, no, is not to perform any name rewriting and let the
system resolver handle all hostname lookups. If set to yes then,
for connections that do not use a ProxyCommand or ProxyJump, ssh(1)
will attempt to canonicalize the hostname specified on the command
line using the CanonicalDomains suffixes and
CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is set
to always, then canonicalization is applied to proxied connections
too.
If this option is enabled, then the configuration files are processed again using the new target name to pick up any new configuration in matching Host and Match stanzas. A value of none disables the use of a ProxyJump host.
Specifies the maximum number of dot characters in a hostname before canonicalization is disabled. The default, 1, allows a single dot (i.e. hostname.subdomain).
Specifies rules to determine whether CNAMEs should be followed when canonicalizing hostnames.
The rules consist of one or more arguments of
source_domain_list:target_domain_list, where source_domain_list is a
pattern-list of domains that may follow CNAMEs in canonicalization, and
target_domain_list is a pattern-list of domains that they may resolve
to.
For example, "*.a.example.com:*.b.example.com,*.c.example.com" will
allow hostnames matching "*.a.example.com" to be canonicalized to
names in the "*.b.example.com" or "*.c.example.com" domains.
Specifies which algorithms are allowed for signing of certificates by certificate authorities (CAs).
The default is:
ssh-ed25519,
ecdsa-sha2-nistp256,
ecdsa-sha2-nistp384,
ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,
rsa-sha2-256If 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.
ssh(1) will not accept host certificates signed using algorithms other than those specified.
Specifies a file from which the user’s certificate is read.
A corresponding private key must be provided separately in order to use
this certificate either from an IdentityFile directive or -i flag to
ssh(1), via ssh-agent(1), or via a PKCS11Provider or
SecurityKeyProvider.
Arguments to CertificateFile may use the tilde syntax to refer to a user’s home directory, the tokens described in the TOKENS section and environment variables as described in the ENVIRONMENT VARIABLES section.
It is possible to have multiple certificate files specified in configuration files; these certificates will be tried in sequence. Multiple CertificateFile directives will add to the list of certificates used for authentication.
Specifies whether to use challenge-response authentication.
The argument to this keyword must be yes or no. The default is
yes.
If this flag is set to yes, ssh(1) will additionally check the host
IP address in the known_hosts file.
This allows ssh to detect if a host key changed due to DNS spoofing. If
the option is set to no, the check will not be executed. The default
is yes.
Specifies the cipher to use for encrypting the session in protocol version 1.
Currently, blowfish, 3des, and des are supported. des is only
supported in the ssh(1) client for interoperability with legacy protocol
1 implementations that do not support the 3des cipher. Its use is
strongly discouraged due to cryptographic weaknesses. The default is
3des.
Specifies the ciphers allowed for protocol version 2 in order of preference.
Multiple ciphers must be comma-separated. The supported ciphers are
3des-cbc, aes128-cbc, aes192-cbc, aes256-cbc, aes128-ctr,
aes192-ctr, aes256-ctr, arcfour128, arcfour256, arcfour,
blowfish-cbc, and cast128-cbc. The default is:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
aes256-cbc,arcfourSpecifies that all local, remote, and dynamic port forwardings specified in the configuration files or on the command line be cleared.
This option is primarily useful when used from the ssh(1) command line
to clear port forwardings set in configuration files, and is
automatically set by scp(1) and sftp(1). The argument must be yes
or no. The default is no.
Specifies whether to use compression.
The argument must be yes or no. The default is no.
Specifies the compression level to use if compression is enabled.
The argument must be an integer from 1 (fast) to 9 (slow, best). The default level is 6, which is good for most applications. The meaning of the values is the same as in gzip(1). Note that this option applies to protocol version 1 only.
Specifies the number of tries (one per second) to make before exiting.
The argument must be an integer. This may be useful in scripts if the connection sometimes fails. The default is 1.
Specifies the timeout (in seconds) used when connecting to the SSH server, instead of using the default system TCP timeout.
This value is used only when the target is down or really unreachable, not when it refuses the connection.
Enables the sharing of multiple sessions over a single network connection.
When set to yes, ssh(1) will listen for connections on a control
socket specified using the ControlPath argument. Additional sessions
can connect to this socket using the same ControlPath with
ControlMaster set to no (the default). These sessions will try to
reuse the master instance’s network connection rather than initiating
new ones, but will fall back to connecting normally if the control
socket does not exist, or is not listening.
Setting this to ask will cause ssh to listen for control
connections, but require confirmation using the SSH_ASKPASS program
before they are accepted (see ssh-add(1) for details). If the
ControlPath cannot be opened, ssh will continue without connecting to
a master instance.
X11 and ssh-agent(1) forwarding is supported over these multiplexed connections, however the display and agent forwarded will be the one belonging to the master connection i.e. it is not possible to forward multiple displays or agents.
Two additional options allow for opportunistic multiplexing: try to use
a master connection but fall back to creating a new one if one does not
already exist. These options are: auto and autoask. The latter
requires confirmation like the ask option.
Specify the path to the control socket used for connection sharing as
described in the ControlMaster section above or the string none to
disable connection sharing.
In the path, %l will be substituted by the local host name, %h will
be substituted by the target host name, %p the port, and %r by
the remote login username. It is recommended that any ControlPath
used for opportunistic connection sharing include at least %h, %p,
and `%r. This ensures that shared connections are uniquely identified.
When used in conjunction with ControlMaster, specifies that the master connection should remain open in the background (waiting for future client connections) after the initial client connection has been closed. If set to no (the default), then the master connection will not be placed into the background, and will close as soon as the initial client connection is closed. If set to yes or 0, then the master connection will remain in the background indefinitely (until killed or closed via a mechanism such as the “ssh -O exit”). If set to a time in seconds, or a time in any of the formats documented in sshd_config(5), then the backgrounded master connection will automatically terminate after it has remained idle (with no client connections) for the specified time.
Specifies that a TCP port on the local machine be forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine.
The argument must be [bind_address:]port. IPv6 addresses can be
specified by enclosing addresses in square brackets or by using an
alternative syntax: [bind_address/]port. By default, the local port is
bound in accordance with the GatewayPorts setting. However, an
explicit bind_address may be used to bind the connection to a specific
address. The bind_address of localhost indicates that the listening
port be bound for local use only, while an empty address or *
indicates that the port should be available from all interfaces.
Currently the SOCKS4 and SOCKS5 protocols are supported, and ssh(1)
will act as a SOCKS server. Multiple forwardings may be specified,
and additional forwardings can be given on the command line. Only
the superuser can forward privileged ports.
Setting this option to yes in the global client configuration file
/etc/ssh/ssh_config enables the use of the helper program
ssh-keysign(8) during HostbasedAuthentication.
The argument must be yes or no. The default is no. This option
should be placed in the non-hostspecific section. See ssh-keysign(8)
for more information.
Sets the escape character (default: ‘~’).
The escape character can also be set on the command line. The argument
should be a single character, ‘^’ followed by a letter, or none to
disable the escape character entirely (making the connection transparent
for binary data).
Specifies whether ssh(1) should terminate the connection if it cannot set up all requested dynamic, tunnel, local, and remote port forwardings.
The argument must be yes or no. The default is no.
Specifies the hash algorithm used when displaying key fingerprints. Valid options are: md5 and sha256 (the default).
Requests ssh to go to background just before command execution. This is
useful if ssh is going to ask for passwords or passphrases, but the user
wants it in the background. This implies the StdinNull configuration
option being set to yes. The recommended way to start X11 programs at
a remote site is with something like ssh -f host xterm, which is the
same as ssh host xterm if the ForkAfterAuthentication configuration
option is set to yes.
If the ExitOnForwardFailure configuration option is set to yes, then a
client started with the ForkAfterAuthentication configuration option
being set to yes will wait for all remote port forwards to be
successfully established before placing itself in the background. The
argument to this keyword must be yes (same as the -f option) or no (the
default).
Specifies whether the connection to the authentication agent (if any) will be forwarded to the remote machine.
The argument must be yes or no. The default is no.
Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent’s Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent.
Specifies whether X11 connections will be automatically redirected over the secure channel and DISPLAY set.
The argument must be yes or no. The default is no.
X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user’s X11 authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring if the ForwardX11Trusted option is also enabled.
Specify a timeout for untrusted X11 forwarding using the format described in the TIME FORMATS section of sshd_config(5). X11 connections received by ssh(1) after this time will be refused. Setting ForwardX11Timeout to zero will disable the timeout and permit X11 forwarding for the life of the connection. The default is to disable untrusted X11 forwarding after twenty minutes has elapsed.
If this option is set to yes, remote X11 clients will have full
access to the original X11 display.
If this option is set to no, remote X11 clients will be considered
untrusted and prevented from stealing or tampering with data belonging
to trusted X11 clients. Furthermore, the xauth(1) token used for the
session will be set to expire after 20 minutes. Remote clients will be
refused access after this time.
The default is no.
See the X11 SECURITY extension specification for full details on the
restrictions imposed on untrusted clients.
Specifies whether remote hosts are allowed to connect to local forwarded ports.
By default, ssh(1) binds local port forwardings to the loopback address.
This prevents other remote hosts from connecting to forwarded ports.
GatewayPorts can be used to specify that ssh should bind local
port forwardings to the wildcard address, thus allowing remote hosts to
connect to forwarded ports. The argument must be yes or no. The
default is no.
Specifies a file to use for the global host key database instead of
/etc/ssh/ssh_known_hosts.
Specifies whether user authentication based on GSSAPI is allowed.
The default is no. Note that this option applies to protocol version 2
only.
If set, specifies the GSSAPI client identity that ssh should use when connecting to the server.
The default is unset, which means that the default identity will be used.
Forward (delegate) credentials to the server.
The default is no. Note that this option applies to protocol version 2
connections using GSSAPI.
Specifies whether key exchange based on GSSAPI may be used.
When using GSSAPI key exchange the server need not have a host key. The
default is no. Note that this option applies to protocol version 2
only.
If set to yes then renewal of the client’s GSSAPI credentials will
force the rekeying of the ssh connection.
With a compatible server, this can delegate the renewed credentials to a
session on the server. The default is no.
Set to yes to indicate that the DNS is trusted to securely
canonicalize` the name of the host being connected to.
If no, the hostname entered on the command line will be passed
untouched to the GSSAPI library. The default is no. This option
only applies to protocol version 2 connections using GSSAPI.
Indicates that ssh(1) should hash host names and addresses when they are
added to ~/.ssh/known_hosts.
These hashed names may be used normally by ssh(1) and sshd(8), but they
do not reveal identifying information should the file’s contents be
disclosed. The default is no. Note that existing names and addresses
in known hosts files will not be converted automatically, but may be
manually hashed using ssh-keygen(1).
Specifies the signature algorithms that will be used for hostbased
authentication as a comma-separated list of patterns. Alternately if the
specified list begins with a + character, then the specified signature
algorithms will be appended to the default set instead of replacing
them. If the specified list begins with a - character, then the
specified signature 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 signature algorithms
will be placed at the head of the default set. The default for this
option is:
ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256,
ecdsa-sha2-nistp384,
ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,
rsa-sha2-256,ssh-rsaThe -Q option of ssh(1) may be used to list supported signature
algorithms. This was formerly named HostbasedKeyTypes.
Specifies whether to try rhosts based authentication with public key authentication.
The argument must be yes or no. The default is no. This option
applies to protocol version 2 only and is similar to
RhostsRSAAuthentication.
Specifies the protocol version 2 host key algorithms that the client wants to use in order of preference.
The default for this option is: ssh-rsa,ssh-dss.
Specifies an alias that should be used instead of the real host name when looking up or saving the host key in the host key database files.
This option is useful for tunneling SSH connections or for multiple servers running on a single host.
Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts. Arguments to Hostname accept the tokens described in the TOKENS section. Numeric IP addresses are also permitted (both on the command line and in Hostname specifications). The default is the name given on the command line.
Specifies the real host name to log into.
This can be used to specify nicknames or abbreviations for hosts. The
default is the name given on the command line. Numeric IP addresses
are also permitted (both on the command line and in HostName
specifications).
Specifies that ssh(1) should only use the authentication identity files configured in the ssh_config files, even if ssh-agent(1) offers more identities.
The argument to this keyword must be yes or no. This option is
intended for situations where ssh-agent offers many different
identities. The default is no.
Specifies the UNIX-domain socket used to communicate with the authentication agent.
This option overrides the SSH_AUTH_SOCK environment variable and can
be used to select a specific agent. Setting the socket name to none
disables the use of an authentication agent. If the string
"SSH_AUTH_SOCK" is specified, the location of the socket will be read
from the SSH_AUTH_SOCK environment variable. Otherwise if the
specified value begins with a $ character, then it will be treated
as an environment variable containing the location of the socket.
Arguments to IdentityAgent may use the tilde syntax to refer to a user’s home directory, the tokens described in the TOKENS section and environment variables as described in the ENVIRONMENT VARIABLES section.
Specifies a file from which the user’s RSA or DSA authentication identity is read.
The default is ~/.ssh/identity for protocol version 1, and
~/.ssh/id_rsa and ~/.ssh/id_dsa for protocol version 2.
Additionally, any identities represented by the authentication agent
will be used for authentication.
The file name may use the tilde syntax to refer to a user’s home
directory or one of the following escape characters: %d (local user’s
home directory), %u (local user name), %l (local host name), %h
(remote host name) or %r (remote user name).
It is possible to have multiple identity files specified in configuration files; all these identities will be tried in sequence.
Specifies a pattern-list of unknown options to be ignored if they are encountered in configuration parsing. This may be used to suppress errors if ssh_config contains options that are unrecognised by ssh(1). It is recommended that IgnoreUnknown be listed early in the configuration file as it will not be applied to unknown options that appear before it.
Include the specified configuration file(s). Multiple pathnames may be
specified and each pathname may contain glob(7) wildcards and, for user
configurations, shell-like ~ references to user home directories.
Wildcards will be expanded and processed in lexical order. Files without
absolute paths are assumed to be in ~/.ssh if included in a user
configuration file or /etc/ssh if included from the system
configuration file. Include directive may appear inside a Match or
Host block to perform conditional inclusion.
Specifies the IPv4 type-of-service or DSCP class for connections.
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.
Specifies whether to use keyboard-interactive authentication.
The argument to this keyword must be yes or no. The default is
yes.
Specifies the list of methods to use in keyboard-interactive authentication.
Multiple method names must be comma-separated. The default is to use the
server specified list. The methods available vary depending on what
the server supports. For an OpenSSH server, it may be zero or more
of: bsdauth, pam, and skey.
Specifies the available KEX (Key Exchange) algorithms.
Multiple algorithms must be comma-separated. If the specified list
begins with a + character, then the specified methods will be appended
to the default set instead of replacing them. If the specified list
begins with a - character, then the specified methods (including
wildcards) will be removed from the default set instead of replacing
them. If the specified list begins with a ^ character, then the
specified methods will be placed at the head of the default set. 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-sha256The list of available key exchange algorithms may also be obtained using
ssh -Q kex.
Specifies a command to use to obtain a list of host keys, in addition to
those listed in UserKnownHostsFile and GlobalKnownHostsFile.
This command is executed after the files have been read. It may write host key lines to standard output in identical format to the usual files (described in the VERIFYING HOST KEYS section in ssh(1)). Arguments to KnownHostsCommand accept the tokens described in the TOKENS section. The command may be invoked multiple times per connection: once when preparing the preference list of host key algorithms to use, again to obtain the host key for the requested host name and, if CheckHostIP is enabled, one more time to obtain the host key matching the server’s address. If the command exits abnormally or returns a non-zero exit status then the connection is terminated.
Specifies a command to execute on the local machine after successfully connecting to the server.
The command string extends to the end of the line, and is executed with the user’s shell. The following escape character substitutions will be performed:
%d(local user’s home directory)%h(remote host name)%l(local host name)%n(host name as provided on the command line)%p(remote port)%r(remote user name)%u(local user name)
This directive is ignored unless PermitLocalCommand has been enabled.
Specifies that a TCP port on the local machine be forwarded over the secure channel to the specified host and port from the remote machine.
The first argument must be [bind_address:]port and the second
argument must be host:hostport. IPv6 addresses can be specified by
enclosing addresses in square brackets or by using an alternative
syntax: [bind_address/]port and host/hostport. Multiple
forwardings may be specified, and additional forwardings can be given on
the command line. Only the superuser can forward privileged ports. By
default, the local port is bound in accordance with the GatewayPorts
setting. However, an explicit bind_address may be used to bind the
connection to a specific address. The bind_address of localhost
indicates that the listening port be bound for local use only, while an
empty address or * indicates that the port should be available from
all interfaces.
Gives the verbosity level that is used when logging messages from ssh(1).
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 verbose output.
Specify one or more overrides to LogLevel.
An override consists of a 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.
Specifies the MAC (message authentication code) algorithms in order of preference.
The MAC algorithm is used in protocol version 2 for data integrity protection. Multiple algorithms must be comma-separated. The default is:
hmac-md5,hmac-sha1,umac-64@openssh.com,
hmac-ripemd160,hmac-sha1-96,hmac-md5-96Restricts the following declarations (up to the next Host or Match
keyword) to be used only when the conditions following the Match keyword
are satisfied. Match conditions are specified using one or more
criteria or the single token all which always matches. The available
criteria keywords are: canonical, final, exec, host, originalhost, user,
and localuser. The all criteria must appear alone or immediately after
canonical or final. Other criteria may be combined arbitrarily. All
criteria but all, canonical, and final require an argument. Criteria may
be negated by prepending an exclamation mark (!).
The canonical keyword matches only when the configuration file is being re-parsed after hostname canonicalization (see the CanonicalizeHostname option). This may be useful to specify conditions that work with canonical host names only.
The final keyword requests that the configuration be re-parsed (regardless of whether CanonicalizeHostname is enabled), and matches only during this final pass. If CanonicalizeHostname is enabled, then canonical and final match during the same pass.
The exec keyword executes the specified command under the user’s shell. If the command returns a zero exit status then the condition is considered true. Commands containing whitespace characters must be quoted. Arguments to exec accept the tokens described in the TOKENS section.
The other keywords’ criteria must be single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNS section. The criteria for the host keyword are matched against the target hostname, after any substitution by the Hostname or CanonicalizeHostname options. The originalhost keyword matches against the hostname as it was specified on the command-line. The user keyword matches against the target username on the remote host. The localuser keyword matches against the name of the local user running ssh(1) (this keyword may be useful in system-wide ssh_config files).
This option can be used if the home directory is shared across machines.
In this case localhost will refer to a different machine on each of the
machines and the user will get many warnings about changed host keys.
However, this option disables host authentication for localhost. The
argument to this keyword must be yes or no. The default is to
check the host key for localhost.
Specifies the number of password prompts before giving up.
The argument to this keyword must be an integer. The default is 3.
Specifies whether to use password authentication.
The argument to this keyword must be yes or no. The default is
yes.
Allow local command execution via the LocalCommand option or using the
!command escape sequence in ssh(1).
The argument must be yes or no. The default is no.
Specifies the destinations to which remote TCP port forwarding is
permitted when RemoteForward is used as a SOCKS proxy.
The forwarding specification must be one of the following forms:
PermitRemoteOpen host:port
PermitRemoteOpen IPv4_addr:port
PermitRemoteOpen [IPv6_addr]:portMultiple forwards may be specified by separating them with whitespace.
An argument of any can be used to remove all restrictions and permit any
forwarding requests. An argument of none can be used to prohibit all
forwarding requests. The wildcard * can be used for host or port to
allow all hosts or ports respectively. Otherwise, no pattern matching or
address lookups are performed on supplied names.
Specifies which PKCS#11 provider to use or none to indicate that no provider should be used (the default).
The argument to this keyword is a path to the PKCS#11 shared library ssh(1) should use to communicate with a PKCS#11 token providing keys for user authentication.
Specifies the port number to connect on the remote host.
The default is 22.
Specifies the order in which the client should try protocol 2 authentication methods.
This allows a client to prefer one method (e.g. keyboard-interactive)
over another method (e.g. password). The default for this option is:
gssapi-with-mic, hostbased, publickey, keyboard-interactive, password.
Specifies the protocol versions ssh(1) should support in order of preference.
The possible values are ‘1’ and ‘2’. Multiple versions must be
comma-separated. The default is 2,1. This means that ssh tries
version 2 and falls back to version 1 if version 2 is not available.
Specifies the command to use to connect to the server.
The command string extends to the end of the line, and is executed with
the user’s shell. In the command string, %h will be substituted by
the host name to connect and %p by the port. The command can be
basically anything, and should read from its standard input and
write to its standard output. It should eventually connect an
sshd(8) server running on some machine, or execute sshd -i
somewhere. Host key management will be done using the HostName of
the host being connected (defaulting to the name typed by the user).
Setting the command to none disables this option entirely. Note
that CheckHostIP is not available for connects
with a proxy command.
This directive is useful in conjunction with nc(1) and its proxy support. For example, the following directive would connect via an HTTP proxy at 192.0.2.0:
ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %pSpecifies one or more jump proxies as either [user@]host[:port] or an
ssh URI.
Multiple proxies may be separated by comma characters and will be visited sequentially. Setting this option will cause ssh(1) to connect to the target host by first making a ssh(1) connection to the specified ProxyJump host and then establishing a TCP forwarding to the ultimate target from there. Setting the host to none disables this option entirely.
Note that this option will compete with the ProxyCommand option -
whichever is specified first will prevent later instances of the other
from taking effect.
Note also that the configuration for the destination host (either
supplied via the command-line or the configuration file) is not
generally applied to jump hosts. ~/.ssh/config should be used if
specific configuration is required for jump hosts.
Specifies that ProxyCommand will pass a connected file descriptor back
to ssh(1) instead of continuing to execute and pass data.
The default is no.
Specifies the signature algorithms that will be used for public key authentication as a comma-separated list of patterns.
If the specified list begins with a + character, then the algorithms
after it will be appended to the default instead of replacing it. 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 default for this option is:
ssh-ed25519-cert-v01@openssh.com,
ecdsa-sha2-nistp256-cert-v01@openssh.com,
ecdsa-sha2-nistp384-cert-v01@openssh.com,
ecdsa-sha2-nistp521-cert-v01@openssh.com,
sk-ssh-ed25519-cert-v01@openssh.com,
sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
rsa-sha2-512-cert-v01@openssh.com,
rsa-sha2-256-cert-v01@openssh.com,
ssh-rsa-cert-v01@openssh.com,
ssh-ed25519,
ecdsa-sha2-nistp256,
ecdsa-sha2-nistp384,
ecdsa-sha2-nistp521,
sk-ssh-ed25519@openssh.com,
sk-ecdsa-sha2-nistp256@openssh.com,
rsa-sha2-512,
rsa-sha2-256,ssh-rsaThe list of available signature algorithms may also be obtained using
ssh -Q PubkeyAcceptedAlgorithms.
Specifies whether to try public key authentication.
The argument to this keyword must be yes or no. The default is
yes. This option applies to protocol version 2 only.
Specifies the maximum amount of data that may be transmitted before the session key is renegotiated.
The argument is the number of bytes, with an optional suffix of ‘K’, ‘M’, or ‘G’ to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between ‘1G’ and ‘4G’, depending on the cipher. This option applies to protocol version 2 only.
Specifies a command to execute on the remote machine after successfully connecting to the server. The command string extends to the end of the line, and is executed with the user’s shell. Arguments to RemoteCommand accept the tokens described in the TOKENS section.
Specifies that a TCP port on the remote machine be forwarded over the secure channel to the specified host and port from the local machine.
The first argument must be [bind_address:]port and the second
argument must be host:hostport. IPv6 addresses can be specified by
enclosing addresses in square brackets or by using an alternative
syntax: [bind_address/]port and host/hostport. Multiple forwardings
may be specified, and additional forwardings can be given on the command
line. Privileged ports can be forwarded only when logging in as root on
the remote machine.
If the port argument is ‘0’, the listen port will be dynamically allocated on the server and reported to the client at run time.
If the bind_address is not specified, the default is to only bind to
loopback addresses. If the bind_address is * or an empty string, then
the forwarding is requested to listen on all interfaces. Specifying a
remote bind_address will only succeed if the server’s GatewayPorts
option is enabled (see sshd_config(5)).
Specifies whether to request a pseudo-tty for the session. The argument may be one of: no (never request a TTY), yes (always request a TTY when standard input is a TTY), force (always request a TTY) or auto (request a TTY when opening a login session). This option mirrors the -t and -T flags for ssh(1).
Specifies revoked host public keys.
Keys listed in this file will be refused for host authentication. Note that if this file does not exist or is not readable, then host authentication will be refused for all hosts. 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).
Specifies whether to try rhosts based authentication with RSA host authentication.
The argument must be yes or no. The default is no. This option
applies to protocol version 1 only and requires ssh(1) to be setuid
root.
Specifies whether to try RSA authentication.
The argument to this keyword must be yes or no. RSA authentication
will only be attempted if the identity file exists, or an authentication
agent is running. The default is yes. Note that this option
applies to protocol version 1 only.
Specifies a path to a library that will be used when loading any FIDO authenticator-hosted keys, overriding the default of using the built-in USB HID support.
If the specified value begins with a $ character, then it will be
treated as an environment variable containing the path to the library.
Specifies what variables from the local environ(7) should be sent to the server.
Note that environment passing is only supported for protocol 2. The server must also support it, and the server must be configured to accept these environment variables. Refer to AcceptEnv in sshd_config(5) for how to configure the server. Variables are specified by name, which may contain wildcard characters. Multiple environment variables may be separated by whitespace or spread across multiple SendEnv directives. The default is not to send any environment variables.
See Patterns for more information on patterns.
Sets the number of server alive messages (see below) which may be sent without ssh(1) receiving any messages back from the server.
If this threshold is reached while server alive messages are being sent,
ssh will disconnect from the server, terminating the session. It is
important to note that the use of server alive messages is very
different from TCPKeepAlive (below). The server alive messages are
sent through the encrypted channel and therefore will not be
spoofable. The TCP keepalive option enabled by TCPKeepAlive is
spoofable. The server alive mechanism is valuable when the client or
server depend on knowing when a connection has become inactive.
The default value is 3. If, for example, ServerAliveInterval (see
below) is set to 15 and ServerAliveCountMax is left at the default,
if the server becomes unresponsive, ssh will disconnect after
approximately 45 seconds. This option applies to protocol version 2
only.
Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server.
The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only.
May be used to either request invocation of a subsystem on the remote system, or to prevent the execution of a remote command at all.
The latter is useful for just forwarding ports. The argument to this keyword must be none (same as the -N option), subsystem (same as the -s option) or default (shell or command execution).
Directly specify one or more environment variables and their contents to be sent to the server.
Similarly to SendEnv, with the exception of the TERM variable, the
server must be prepared to accept the environment variable.
Specifies which smartcard device to use.
The argument to this keyword is the device ssh(1) should use to communicate with a smartcard used for storing the user’s private RSA key. By default, no device is specified and smartcard support is not activated.
Redirects stdin from /dev/null (actually, prevents reading from
stdin).
Either this or the equivalent -n option must be used when ssh is run in the background. The argument to this keyword must be yes (same as the -n option) or no (the default).
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.
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, ssh 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).
If this flag is set to yes, ssh(1) will never automatically add host
keys to the ~/.ssh/known_hosts file, and refuses to connect to hosts
whose host key has changed.
This provides maximum protection against trojan horse attacks, though it
can be annoying when the /etc/ssh/ssh_known_hosts file is poorly
maintained or when connections to new hosts are frequently made.
This option forces the user to manually add all new hosts. If this
flag is set to no, ssh will automatically add new host keys to the
user known hosts files. If this flag is set to ask, new host keys
will be added to the user known host files only after the user has
confirmed that is what they really want to do, and ssh will refuse
to connect to hosts whose host key has changed. The host keys of
known hosts will be verified automatically in all cases. The
argument must be yes, no, or ask. The default is ask.
Gives the facility code that is used when logging messages from ssh(1).
The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1,
LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The
default is USER.
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.
The default is yes (to send TCP keepalive messages), and the client
will notice if the network goes down or the remote host dies. This is
important in scripts, and many users want it too.
To disable TCP keepalive messages, the value should be set to no.
Request tun(4) device forwarding between the client and the server.
The argument must be yes, point-to-point (layer 3), ethernet
(layer 2), or no. Specifying yes requests the default tunnel
mode, which is point-to-point. The default is no.
Specifies the tun(4) devices to open on the client (local_tun) and the
server (remote_tun).
The argument must be local_tun[:remote_tun]. The devices may be
specified by numerical ID or the keyword any, which uses the next
available tunnel device. If remote_tun is not specified, it defaults to
any. The default is any:any.
Specifies whether ssh(1) should accept notifications of additional
hostkeys from the server sent after authentication has completed and add
them to UserKnownHostsFile.
The argument must be yes, no or ask. This option allows learning
alternate hostkeys for a server and supports graceful key rotation by
allowing a server to send replacement public keys before old ones are
removed.
Additional hostkeys are only accepted if the key used to authenticate
the host was already trusted or explicitly accepted by the user, the
host was authenticated via UserKnownHostsFile (i.e. not
GlobalKnownHostsFile) and the host was authenticated using a plain key
and not a certificate.
UpdateHostKeys is enabled by default if the user has not overridden
the default UserKnownHostsFile setting and has not enabled
VerifyHostKeyDNS, otherwise UpdateHostKeys will be set to no.
If UpdateHostKeys is set to ask, then the user is asked to confirm
the modifications to the known_hosts file. Confirmation is currently
incompatible with ControlPersist, and will be disabled if it is enabled.
Presently, only sshd(8) from OpenSSH 6.8 and greater support the “hostkeys@openssh.com” protocol extension used to inform the client of all the server’s hostkeys.
Specifies whether to use a privileged port for outgoing connections.
The argument must be yes or no. The default is no. If set to
yes, ssh(1) must be setuid root. Note that this option must be set
to yes for RhostsRSAAuthentication with older servers.
Specifies the user to log in as.
This can be useful when a different user name is used on different machines. This saves the trouble of having to remember to give the user name on the command line.
Specifies a file to use for the user host key database instead of
~/.ssh/known_hosts.
Specifies whether to verify the remote key using DNS and SSHFP resource records.
If this option is set to yes, the client will implicitly trust keys
that match a secure fingerprint from DNS. Insecure fingerprints will
be handled as if this option was set to ask. If this option is set
to ask, information on fingerprint match will be displayed, but
the user will still need to confirm new host keys according to the
StrictHostKeyChecking option. The argument must be yes, no, or
ask. The default is no. Note that this option applies to
protocol version 2 only.
See also VERIFYING HOST KEYS in ssh(1).
If this flag is set to yes, an ASCII art representation of the
remote host key fingerprint is printed in addition to the hex
fingerprint string at login and for unknown host keys.
If this flag is set to no, no fingerprint strings are printed at login
and only the hex fingerprint string will be printed for unknown host
keys. The default is no.
Specifies the full pathname of the xauth(1) program.
The default is /usr/bin/xauth.
Trait Implementations
Auto Trait Implementations
impl RefUnwindSafe for SshOptionKey
impl Send for SshOptionKey
impl Sync for SshOptionKey
impl Unpin for SshOptionKey
impl UnwindSafe for SshOptionKey
Blanket Implementations
Mutably borrows from an owned value. Read more
Compare self to key and return true if they are equal.