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authorjmc@openbsd.org <jmc@openbsd.org>2016-10-15 19:56:25 +0000
committerDarren Tucker <dtucker@zip.com.au>2016-10-19 03:30:04 +1100
commitfd2a8f1033fa2316fff719fd5176968277560158 (patch)
tree81a6e5e2b375c564f51b458558a4b7d38accd033 /ssh_config.5
parent8f866d8a57b9a2dc5dd04504e27f593b551618e3 (diff)
upstream commit
various formatting fixes, specifically removing Dq; Upstream-ID: 81e85df2b8e474f5f93d66e61d9a4419ce87347c
Diffstat (limited to 'ssh_config.5')
-rw-r--r--ssh_config.5566
1 files changed, 244 insertions, 322 deletions
diff --git a/ssh_config.5 b/ssh_config.5
index 1d515008..591365f3 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -33,8 +33,8 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.\" $OpenBSD: ssh_config.5,v 1.239 2016/09/28 17:59:22 jmc Exp $
-.Dd $Mdocdate: September 28 2016 $
+.\" $OpenBSD: ssh_config.5,v 1.240 2016/10/15 19:56:25 jmc Exp $
+.Dd $Mdocdate: October 15 2016 $
.Dt SSH_CONFIG 5
.Os
.Sh NAME
@@ -62,25 +62,25 @@ system-wide configuration file
For each parameter, the first obtained value
will be used.
The configuration files contain sections separated by
-.Dq Host
+.Cm Host
specifications, and that section is only applied for hosts that
match one of the patterns given in the specification.
The matched host name is usually the one given on the command line
(see the
.Cm CanonicalizeHostname
-option for exceptions.)
+option for exceptions).
.Pp
Since the first obtained value for each parameter is used, more
host-specific declarations should be given near the beginning of the
file, and general defaults at the end.
.Pp
-The configuration file has the following format:
-.Pp
-Empty lines and lines starting with
+The file contains keyword-argument pairs, one per line.
+Lines starting with
.Ql #
-are comments.
-Otherwise a line is of the format
-.Dq keyword arguments .
+and empty lines are interpreted as comments.
+Arguments may optionally be enclosed in double quotes
+.Pq \&"
+in order to represent arguments containing spaces.
Configuration options may be separated by whitespace or
optional whitespace and exactly one
.Ql = ;
@@ -92,9 +92,6 @@ and
.Nm sftp
.Fl o
option.
-Arguments may optionally be enclosed in double quotes
-.Pq \&"
-in order to represent arguments containing spaces.
.Pp
The possible
keywords and their meanings are as follows (note that
@@ -117,7 +114,7 @@ The host is usually the
argument given on the command line
(see the
.Cm CanonicalizeHostname
-option for exceptions.)
+keyword for exceptions).
.Pp
A pattern entry may be negated by prefixing it with an exclamation mark
.Pq Sq !\& .
@@ -212,57 +209,54 @@ files).
Specifies whether keys should be automatically added to a running
.Xr ssh-agent 1 .
If this option is set to
-.Dq yes
+.Cm 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
.Xr ssh-add 1 .
If this option is set to
-.Dq ask ,
-.Nm ssh
+.Cm ask ,
+.Xr ssh 1
will require confirmation using the
.Ev SSH_ASKPASS
program before adding a key (see
.Xr ssh-add 1
for details).
If this option is set to
-.Dq confirm ,
+.Cm confirm ,
each use of the key must be confirmed, as if the
.Fl c
option was specified to
.Xr ssh-add 1 .
If this option is set to
-.Dq no ,
+.Cm no ,
no keys are added to the agent.
The argument must be
-.Dq yes ,
-.Dq confirm ,
-.Dq ask ,
+.Cm yes ,
+.Cm confirm ,
+.Cm ask ,
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm AddressFamily
Specifies which address family to use when connecting.
Valid arguments are
-.Dq any ,
-.Dq inet
+.Cm any
+(the default),
+.Cm inet
(use IPv4 only), or
-.Dq inet6
+.Cm inet6
(use IPv6 only).
-The default is
-.Dq any .
.It Cm BatchMode
If set to
-.Dq yes ,
+.Cm 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
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm BindAddress
Use the specified address on the local machine as the source address of
the connection.
@@ -270,7 +264,7 @@ Only useful on systems with more than one address.
Note that this option does not work if
.Cm UsePrivilegedPort
is set to
-.Dq yes .
+.Cm yes .
.It Cm CanonicalDomains
When
.Cm CanonicalizeHostname
@@ -279,11 +273,11 @@ search for the specified destination host.
.It Cm CanonicalizeFallbackLocal
Specifies whether to fail with an error when hostname canonicalization fails.
The default,
-.Dq yes ,
+.Cm yes ,
will attempt to look up the unqualified hostname using the system resolver's
search rules.
A value of
-.Dq no
+.Cm no
will cause
.Xr ssh 1
to fail instantly if
@@ -294,11 +288,11 @@ specified by
.It Cm CanonicalizeHostname
Controls whether explicit hostname canonicalization is performed.
The default,
-.Dq no ,
+.Cm no ,
is not to perform any name rewriting and let the system resolver handle all
hostname lookups.
If set to
-.Dq yes
+.Cm yes
then, for connections that do not use a
.Cm ProxyCommand ,
.Xr ssh 1
@@ -311,7 +305,7 @@ rules.
If
.Cm CanonicalizeHostname
is set to
-.Dq always ,
+.Cm always ,
then canonicalization is applied to proxied connections too.
.Pp
If this option is enabled, then the configuration files are processed
@@ -323,8 +317,7 @@ stanzas.
.It Cm CanonicalizeMaxDots
Specifies the maximum number of dot characters in a hostname before
canonicalization is disabled.
-The default,
-.Dq 1 ,
+The default, 1,
allows a single dot (i.e. hostname.subdomain).
.It Cm CanonicalizePermittedCNAMEs
Specifies rules to determine whether CNAMEs should be followed when
@@ -339,13 +332,13 @@ and
is a pattern-list of domains that they may resolve to.
.Pp
For example,
-.Dq *.a.example.com:*.b.example.com,*.c.example.com
+.Qq *.a.example.com:*.b.example.com,*.c.example.com
will allow hostnames matching
-.Dq *.a.example.com
+.Qq *.a.example.com
to be canonicalized to names in the
-.Dq *.b.example.com
+.Qq *.b.example.com
or
-.Dq *.c.example.com
+.Qq *.c.example.com
domains.
.It Cm CertificateFile
Specifies a file from which the user's certificate is read.
@@ -378,47 +371,42 @@ authentication.
.It Cm ChallengeResponseAuthentication
Specifies whether to use challenge-response authentication.
The argument to this keyword must be
-.Dq yes
+.Cm yes
+(the default)
or
-.Dq no .
-The default is
-.Dq yes .
+.Cm no .
.It Cm CheckHostIP
-If this flag is set to
-.Dq yes ,
+If set to
+.Cm yes
+(the default),
.Xr ssh 1
will additionally check the host IP address in the
.Pa known_hosts
file.
-This allows ssh to detect if a host key changed due to DNS spoofing
+This allows it to detect if a host key changed due to DNS spoofing
and will add addresses of destination hosts to
.Pa ~/.ssh/known_hosts
in the process, regardless of the setting of
.Cm StrictHostKeyChecking .
If the option is set to
-.Dq no ,
+.Cm no ,
the check will not be executed.
-The default is
-.Dq yes .
.It Cm Cipher
Specifies the cipher to use for encrypting the session
in protocol version 1.
Currently,
-.Dq blowfish ,
-.Dq 3des ,
+.Cm blowfish ,
+.Cm 3des
+(the default),
and
-.Dq des
-are supported.
-.Ar des
+.Cm des
+are supported,
+though
+.Cm des
is only supported in the
.Xr ssh 1
-client for interoperability with legacy protocol 1 implementations
-that do not support the
-.Ar 3des
-cipher.
-Its use is strongly discouraged due to cryptographic weaknesses.
-The default is
-.Dq 3des .
+client for interoperability with legacy protocol 1 implementations;
+its use is strongly discouraged due to cryptographic weaknesses.
.It Cm Ciphers
Specifies the ciphers allowed for protocol version 2
in order of preference.
@@ -429,39 +417,23 @@ character, then the specified ciphers will be appended to the default set
instead of replacing them.
.Pp
The supported ciphers are:
-.Pp
-.Bl -item -compact -offset indent
-.It
+.Bd -literal -offset indent
3des-cbc
-.It
aes128-cbc
-.It
aes192-cbc
-.It
aes256-cbc
-.It
aes128-ctr
-.It
aes192-ctr
-.It
aes256-ctr
-.It
aes128-gcm@openssh.com
-.It
aes256-gcm@openssh.com
-.It
arcfour
-.It
arcfour128
-.It
arcfour256
-.It
blowfish-cbc
-.It
cast128-cbc
-.It
chacha20-poly1305@openssh.com
-.El
+.Ed
.Pp
The default is:
.Bd -literal -offset indent
@@ -471,12 +443,8 @@ aes128-gcm@openssh.com,aes256-gcm@openssh.com,
aes128-cbc,aes192-cbc,aes256-cbc
.Ed
.Pp
-The list of available ciphers may also be obtained using the
-.Fl Q
-option of
-.Xr ssh 1
-with an argument of
-.Dq cipher .
+The list of available ciphers may also be obtained using
+.Qq ssh -Q cipher .
.It Cm ClearAllForwardings
Specifies that all local, remote, and dynamic port forwardings
specified in the configuration files or on the command line be
@@ -489,19 +457,17 @@ configuration files, and is automatically set by
and
.Xr sftp 1 .
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm Compression
Specifies whether to use compression.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm CompressionLevel
Specifies the compression level to use if compression is enabled.
The argument must be an integer from 1 (fast) to 9 (slow, best).
@@ -522,7 +488,7 @@ not when it refuses the connection.
.It Cm ControlMaster
Enables the sharing of multiple sessions over a single network connection.
When set to
-.Dq yes ,
+.Cm yes ,
.Xr ssh 1
will listen for connections on a control socket specified using the
.Cm ControlPath
@@ -532,21 +498,23 @@ Additional sessions can connect to this socket using the same
with
.Cm ControlMaster
set to
-.Dq no
+.Cm 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.
.Pp
Setting this to
-.Dq ask
-will cause ssh
+.Cm ask
+will cause
+.Xr ssh 1
to listen for control connections, but require confirmation using
.Xr ssh-askpass 1 .
If the
.Cm ControlPath
cannot be opened,
-ssh will continue without connecting to a master instance.
+.Xr ssh 1
+will continue without connecting to a master instance.
.Pp
X11 and
.Xr ssh-agent 1
@@ -558,18 +526,18 @@ 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:
-.Dq auto
+.Cm auto
and
-.Dq autoask .
+.Cm autoask .
The latter requires confirmation like the
-.Dq ask
+.Cm ask
option.
.It Cm ControlPath
Specify the path to the control socket used for connection sharing as described
in the
.Cm ControlMaster
section above or the string
-.Dq none
+.Cm none
to disable connection sharing.
Arguments to
.Cm ControlPath
@@ -590,18 +558,15 @@ 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
-.Dq no ,
+.Cm no ,
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
-.Dq yes
-or
-.Dq 0 ,
+.Cm yes
+or 0,
then the master connection will remain in the background indefinitely
(until killed or closed via a mechanism such as the
-.Xr ssh 1
-.Dq Fl O No exit
-option).
+.Qq ssh -O exit ) .
If set to a time in seconds, or a time in any of the formats documented in
.Xr sshd_config 5 ,
then the backgrounded master connection will automatically terminate
@@ -627,7 +592,7 @@ may be used to bind the connection to a specific address.
The
.Ar bind_address
of
-.Dq localhost
+.Cm localhost
indicates that the listening port be bound for local use only, while an
empty address or
.Sq *
@@ -641,7 +606,7 @@ additional forwardings can be given on the command line.
Only the superuser can forward privileged ports.
.It Cm EnableSSHKeysign
Setting this option to
-.Dq yes
+.Cm yes
in the global client configuration file
.Pa /etc/ssh/ssh_config
enables the use of the helper program
@@ -649,11 +614,10 @@ enables the use of the helper program
during
.Cm HostbasedAuthentication .
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
This option should be placed in the non-hostspecific section.
See
.Xr ssh-keysign 8
@@ -666,7 +630,7 @@ be set on the command line.
The argument should be a single character,
.Ql ^
followed by a letter, or
-.Dq none
+.Cm none
to disable the escape
character entirely (making the connection transparent for binary
data).
@@ -683,28 +647,25 @@ for example, cause
.Xr ssh 1
to exit if TCP connections to the ultimate forwarding destination fail.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm FingerprintHash
Specifies the hash algorithm used when displaying key fingerprints.
Valid options are:
-.Dq md5
+.Cm md5
and
-.Dq sha256 .
-The default is
-.Dq sha256 .
+.Cm sha256
+(the default).
.It Cm ForwardAgent
Specifies whether the connection to the authentication agent (if any)
will be forwarded to the remote machine.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.Pp
Agent forwarding should be enabled with caution.
Users with the ability to bypass file permissions on the remote host
@@ -719,11 +680,10 @@ over the secure channel and
.Ev DISPLAY
set.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.Pp
X11 forwarding should be enabled with caution.
Users with the ability to bypass file permissions on the remote host
@@ -736,7 +696,8 @@ option is also enabled.
.It Cm ForwardX11Timeout
Specify a timeout for untrusted X11 forwarding
using the format described in the
-TIME FORMATS section of
+.Sx TIME FORMATS
+section of
.Xr sshd_config 5 .
X11 connections received by
.Xr ssh 1
@@ -745,11 +706,12 @@ The default is to disable untrusted X11 forwarding after twenty minutes has
elapsed.
.It Cm ForwardX11Trusted
If this option is set to
-.Dq yes ,
+.Cm yes ,
remote X11 clients will have full access to the original X11 display.
.Pp
If this option is set to
-.Dq no ,
+.Cm no
+(the default),
remote X11 clients will be considered untrusted and prevented
from stealing or tampering with data belonging to trusted X11
clients.
@@ -758,9 +720,6 @@ Furthermore, the
token used for the session will be set to expire after 20 minutes.
Remote clients will be refused access after this time.
.Pp
-The default is
-.Dq no .
-.Pp
See the X11 SECURITY extension specification for full details on
the restrictions imposed on untrusted clients.
.It Cm GatewayPorts
@@ -775,11 +734,10 @@ 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
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm GlobalKnownHostsFile
Specifies one or more files to use for the global
host key database, separated by whitespace.
@@ -789,11 +747,11 @@ The default is
.It Cm GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed.
The default is
-.Dq no .
+.Cm no .
.It Cm GSSAPIDelegateCredentials
Forward (delegate) credentials to the server.
The default is
-.Dq no .
+.Cm no .
.It Cm HashKnownHosts
Indicates that
.Xr ssh 1
@@ -806,7 +764,7 @@ and
but they do not reveal identifying information should the file's contents
be disclosed.
The default is
-.Dq no .
+.Cm no .
Note that existing names and addresses in known hosts files
will not be converted automatically,
but may be manually hashed using
@@ -815,11 +773,10 @@ but may be manually hashed using
Specifies whether to try rhosts based authentication with public key
authentication.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm HostbasedKeyTypes
Specifies the key types that will be used for hostbased authentication
as a comma-separated pattern list.
@@ -864,12 +821,8 @@ ssh-ed25519,ssh-rsa
If hostkeys are known for the destination host then this default is modified
to prefer their algorithms.
.Pp
-The list of available key types may also be obtained using the
-.Fl Q
-option of
-.Xr ssh 1
-with an argument of
-.Dq key .
+The list of available key types may also be obtained using
+.Qq ssh -Q key .
.It Cm HostKeyAlias
Specifies an alias that should be used instead of the
real host name when looking up or saving the host key
@@ -904,26 +857,25 @@ or a
.Cm PKCS11Provider
offers more identities.
The argument to this keyword must be
-.Dq yes
+.Cm yes
or
-.Dq no .
+.Cm no
+(the default).
This option is intended for situations where ssh-agent
offers many different identities.
-The default is
-.Dq no .
.It Cm IdentityAgent
Specifies the
.Ux Ns -domain
socket used to communicate with the authentication agent.
.Pp
This option overrides the
-.Dq SSH_AUTH_SOCK
+.Ev SSH_AUTH_SOCK
environment variable and can be used to select a specific agent.
Setting the socket name to
-.Dq none
+.Cm none
disables the use of an authentication agent.
If the string
-.Dq SSH_AUTH_SOCK
+.Qq SSH_AUTH_SOCK
is specified, the location of the socket will be read from the
.Ev SSH_AUTH_SOCK
environment variable.
@@ -999,7 +951,7 @@ Include the specified configuration file(s).
Multiple pathnames may be specified and each pathname may contain
.Xr glob 3
wildcards and, for user configurations, shell-like
-.Dq ~
+.Sq ~
references to user home directories.
Files without absolute paths are assumed to be in
.Pa ~/.ssh
@@ -1016,48 +968,47 @@ to perform conditional inclusion.
.It Cm IPQoS
Specifies the IPv4 type-of-service or DSCP class for connections.
Accepted values are
-.Dq af11 ,
-.Dq af12 ,
-.Dq af13 ,
-.Dq af21 ,
-.Dq af22 ,
-.Dq af23 ,
-.Dq af31 ,
-.Dq af32 ,
-.Dq af33 ,
-.Dq af41 ,
-.Dq af42 ,
-.Dq af43 ,
-.Dq cs0 ,
-.Dq cs1 ,
-.Dq cs2 ,
-.Dq cs3 ,
-.Dq cs4 ,
-.Dq cs5 ,
-.Dq cs6 ,
-.Dq cs7 ,
-.Dq ef ,
-.Dq lowdelay ,
-.Dq throughput ,
-.Dq reliability ,
+.Cm af11 ,
+.Cm af12 ,
+.Cm af13 ,
+.Cm af21 ,
+.Cm af22 ,
+.Cm af23 ,
+.Cm af31 ,
+.Cm af32 ,
+.Cm af33 ,
+.Cm af41 ,
+.Cm af42 ,
+.Cm af43 ,
+.Cm cs0 ,
+.Cm cs1 ,
+.Cm cs2 ,
+.Cm cs3 ,
+.Cm cs4 ,
+.Cm cs5 ,
+.Cm cs6 ,
+.Cm cs7 ,
+.Cm ef ,
+.Cm lowdelay ,
+.Cm throughput ,
+.Cm reliability ,
or a numeric value.
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
-.Dq lowdelay
+.Cm lowdelay
for interactive sessions and
-.Dq throughput
+.Cm throughput
for non-interactive sessions.
.It Cm KbdInteractiveAuthentication
Specifies whether to use keyboard-interactive authentication.
The argument to this keyword must be
-.Dq yes
+.Cm yes
+(the default)
or
-.Dq no .
-The default is
-.Dq yes .
+.Cm no .
.It Cm KbdInteractiveDevices
Specifies the list of methods to use in keyboard-interactive authentication.
Multiple method names must be comma-separated.
@@ -1065,10 +1016,10 @@ 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:
-.Dq bsdauth ,
-.Dq pam ,
+.Cm bsdauth ,
+.Cm pam ,
and
-.Dq skey .
+.Cm skey .
.It Cm KexAlgorithms
Specifies the available KEX (Key Exchange) algorithms.
Multiple algorithms must be comma-separated.
@@ -1085,12 +1036,8 @@ diffie-hellman-group-exchange-sha1,
diffie-hellman-group14-sha1
.Ed
.Pp
-The list of available key exchange algorithms may also be obtained using the
-.Fl Q
-option of
-.Xr ssh 1
-with an argument of
-.Dq kex .
+The list of available key exchange algorithms may also be obtained using
+.Qq ssh -Q kex .
.It Cm LocalCommand
Specifies a command to execute on the local machine after successfully
connecting to the server.
@@ -1133,7 +1080,7 @@ may be used to bind the connection to a specific address.
The
.Ar bind_address
of
-.Dq localhost
+.Cm localhost
indicates that the listening port be bound for local use only, while an
empty address or
.Sq *
@@ -1157,7 +1104,7 @@ character, then the specified algorithms will be appended to the default set
instead of replacing them.
.Pp
The algorithms that contain
-.Dq -etm
+.Qq -etm
calculate the MAC after encryption (encrypt-then-mac).
These are considered safer and their use recommended.
.Pp
@@ -1170,22 +1117,18 @@ umac-64@openssh.com,umac-128@openssh.com,
hmac-sha2-256,hmac-sha2-512,hmac-sha1
.Ed
.Pp
-The list of available MAC algorithms may also be obtained using the
-.Fl Q
-option of
-.Xr ssh 1
-with an argument of
-.Dq mac .
+The list of available MAC algorithms may also be obtained using
+.Qq ssh -Q mac .
.It Cm NoHostAuthenticationForLocalhost
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
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is to check the host key for localhost.
+.Cm no .
+(the default).
.It Cm NumberOfPasswordPrompts
Specifies the number of password prompts before giving up.
The argument to this keyword must be an integer.
@@ -1193,11 +1136,10 @@ The default is 3.
.It Cm PasswordAuthentication
Specifies whether to use password authentication.
The argument to this keyword must be
-.Dq yes
+.Cm yes
+(the default)
or
-.Dq no .
-The default is
-.Dq yes .
+.Cm no .
.It Cm PermitLocalCommand
Allow local command execution via the
.Ic LocalCommand
@@ -1206,11 +1148,10 @@ option or using the
escape sequence in
.Xr ssh 1 .
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm PKCS11Provider
Specifies which PKCS#11 provider to use.
The argument to this keyword is the PKCS#11 shared library
@@ -1235,18 +1176,14 @@ keyboard-interactive,password
Specifies the protocol versions
.Xr ssh 1
should support in order of preference.
-The possible values are
-.Sq 1
-and
-.Sq 2 .
+The possible values are 1 and 2.
Multiple versions must be comma-separated.
When this option is set to
-.Dq 2,1
+.Cm 2,1
.Nm ssh
will try version 2 and fall back to version 1
if version 2 is not available.
-The default is
-.Sq 2 .
+The default is version 2.
Protocol 1 suffers from a number of cryptographic weaknesses and should
not be used.
It is only offered to support legacy devices.
@@ -1274,7 +1211,7 @@ 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
-.Dq none
+.Cm none
disables this option entirely.
Note that
.Cm CheckHostIP
@@ -1319,7 +1256,7 @@ will pass a connected file descriptor back to
.Xr ssh 1
instead of continuing to execute and pass data.
The default is
-.Dq no .
+.Cm no .
.It Cm PubkeyAcceptedKeyTypes
Specifies the key types that will be used for public key authentication
as a comma-separated pattern list.
@@ -1338,19 +1275,15 @@ ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
ssh-ed25519,ssh-rsa
.Ed
.Pp
-The
-.Fl Q
-option of
-.Xr ssh 1
-may be used to list supported key types.
+The list of available key types may also be obtained using
+.Qq ssh -Q key .
.It Cm PubkeyAuthentication
Specifies whether to try public key authentication.
The argument to this keyword must be
-.Dq yes
+.Cm yes
+(the default)
or
-.Dq no .
-The default is
-.Dq yes .
+.Cm no .
.It Cm RekeyLimit
Specifies the maximum amount of data that may be transmitted before the
session key is renegotiated, optionally followed a maximum amount of
@@ -1368,12 +1301,13 @@ and
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 of
+.Sx TIME FORMATS
+section of
.Xr sshd_config 5 .
The default value for
.Cm RekeyLimit
is
-.Dq default none ,
+.Cm 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.
.It Cm RemoteForward
@@ -1393,8 +1327,7 @@ logging in as root on the remote machine.
.Pp
If the
.Ar port
-argument is
-.Ql 0 ,
+argument is 0,
the listen port will be dynamically allocated on the server and reported
to the client at run time.
.Pp
@@ -1416,13 +1349,13 @@ option is enabled (see
.It Cm RequestTTY
Specifies whether to request a pseudo-tty for the session.
The argument may be one of:
-.Dq no
+.Cm no
(never request a TTY),
-.Dq yes
+.Cm yes
(always request a TTY when standard input is a TTY),
-.Dq force
+.Cm force
(always request a TTY) or
-.Dq auto
+.Cm auto
(request a TTY when opening a login session).
This option mirrors the
.Fl t
@@ -1444,25 +1377,23 @@ For more information on KRLs, see the KEY REVOCATION LISTS section in
Specifies whether to try rhosts based authentication with RSA host
authentication.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
This option applies to protocol version 1 only and requires
.Xr ssh 1
to be setuid root.
.It Cm RSAAuthentication
Specifies whether to try RSA authentication.
The argument to this keyword must be
-.Dq yes
+.Cm yes
+(the default)
or
-.Dq no .
+.Cm no .
RSA authentication will only be
attempted if the identity file exists, or an authentication agent is
running.
-The default is
-.Dq yes .
Note that this option applies to protocol version 1 only.
.It Cm SendEnv
Specifies what variables from the local
@@ -1545,14 +1476,13 @@ 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.
.Pp
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
.It Cm StrictHostKeyChecking
If this flag is set to
-.Dq yes ,
+.Cm yes ,
.Xr ssh 1
will never automatically add host keys to the
.Pa ~/.ssh/known_hosts
@@ -1565,24 +1495,18 @@ frequently made.
This option forces the user to manually
add all new hosts.
If this flag is set to
-.Dq no ,
+.Cm no ,
ssh will automatically add new host keys to the
user known hosts files.
If this flag is set to
-.Dq ask ,
+.Cm ask
+(the default),
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
-.Dq yes ,
-.Dq no ,
-or
-.Dq ask .
-The default is
-.Dq ask .
.It Cm TCPKeepAlive
Specifies whether the system should send TCP keepalive messages to the
other side.
@@ -1593,31 +1517,30 @@ connections will die if the route is down temporarily, and some people
find it annoying.
.Pp
The default is
-.Dq yes
+.Cm 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.
.Pp
To disable TCP keepalive messages, the value should be set to
-.Dq no .
+.Cm no .
.It Cm Tunnel
Request
.Xr tun 4
device forwarding between the client and the server.
The argument must be
-.Dq yes ,
-.Dq point-to-point
+.Cm yes ,
+.Cm point-to-point
(layer 3),
-.Dq ethernet
+.Cm ethernet
(layer 2),
or
-.Dq no .
+.Cm no
+(the default).
Specifying
-.Dq yes
+.Cm yes
requests the default tunnel mode, which is
-.Dq point-to-point .
-The default is
-.Dq no .
+.Cm point-to-point .
.It Cm TunnelDevice
Specifies the
.Xr tun 4
@@ -1631,14 +1554,14 @@ The argument must be
.Ar local_tun Op : Ar remote_tun .
.Sm on
The devices may be specified by numerical ID or the keyword
-.Dq any ,
+.Cm any ,
which uses the next available tunnel device.
If
.Ar remote_tun
is not specified, it defaults to
-.Dq any .
+.Cm any .
The default is
-.Dq any:any .
+.Cm any:any .
.It Cm UpdateHostKeys
Specifies whether
.Xr ssh 1
@@ -1646,10 +1569,10 @@ should accept notifications of additional hostkeys from the server sent
after authentication has completed and add them to
.Cm UserKnownHostsFile .
The argument must be
-.Dq yes ,
-.Dq no
+.Cm yes ,
+.Cm no
(the default) or
-.Dq ask .
+.Cm ask .
Enabling 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.
@@ -1658,7 +1581,7 @@ host was already trusted or explicitly accepted by the user.
If
.Cm UpdateHostKeys
is set to
-.Dq ask ,
+.Cm ask ,
then the user is asked to confirm the modifications to the known_hosts file.
Confirmation is currently incompatible with
.Cm ControlPersist ,
@@ -1667,22 +1590,21 @@ and will be disabled if it is enabled.
Presently, only
.Xr sshd 8
from OpenSSH 6.8 and greater support the
-.Dq hostkeys@openssh.com
+.Qq hostkeys@openssh.com
protocol extension used to inform the client of all the server's hostkeys.
.It Cm UsePrivilegedPort
Specifies whether to use a privileged port for outgoing connections.
The argument must be
-.Dq yes
+.Cm yes
or
-.Dq no .
-The default is
-.Dq no .
+.Cm no
+(the default).
If set to
-.Dq yes ,
+.Cm yes ,
.Xr ssh 1
must be setuid root.
Note that this option must be set to
-.Dq yes
+.Cm yes
for
.Cm RhostsRSAAuthentication
with older servers.
@@ -1701,39 +1623,35 @@ The default is
Specifies whether to verify the remote key using DNS and SSHFP resource
records.
If this option is set to
-.Dq yes ,
+.Cm 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
-.Dq ask .
+.Cm ask .
If this option is set to
-.Dq ask ,
+.Cm ask ,
information on fingerprint match will be displayed, but the user will still
need to confirm new host keys according to the
.Cm StrictHostKeyChecking
option.
-The argument must be
-.Dq yes ,
-.Dq no ,
-or
-.Dq ask .
The default is
-.Dq no .
+.Cm no .
.Pp
-See also VERIFYING HOST KEYS in
+See also
+.Sx VERIFYING HOST KEYS
+in
.Xr ssh 1 .
.It Cm VisualHostKey
If this flag is set to
-.Dq yes ,
+.Cm yes ,
an ASCII art representation of the remote host key fingerprint is
printed in addition to the fingerprint string at login and
for unknown host keys.
If this flag is set to
-.Dq no ,
+.Cm no
+(the default),
no fingerprint strings are printed at login and
only the fingerprint string will be printed for unknown host keys.
-The default is
-.Dq no .
.It Cm XAuthLocation
Specifies the full pathname of the
.Xr xauth 1
@@ -1751,7 +1669,7 @@ or
.Sq ?\&
(a wildcard that matches exactly one character).
For example, to specify a set of declarations for any host in the
-.Dq .co.uk
+.Qq .co.uk
set of domains,
the following pattern could be used:
.Pp
@@ -1771,7 +1689,7 @@ by preceding them with an exclamation mark
For example,
to allow a key to be used from anywhere within an organization
except from the
-.Dq dialup
+.Qq dialup
pool,
the following entry (in authorized_keys) could be used:
.Pp
@@ -1846,11 +1764,15 @@ This file must be world-readable.
.Sh SEE ALSO
.Xr ssh 1
.Sh AUTHORS
+.An -nosplit
OpenSSH is a derivative of the original and free
-ssh 1.2.12 release by Tatu Ylonen.
-Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
-Theo de Raadt and Dug Song
+ssh 1.2.12 release by
+.An Tatu Ylonen .
+.An Aaron Campbell , Bob Beck , Markus Friedl ,
+.An Niels Provos , Theo de Raadt
+and
+.An 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.
+.An Markus Friedl
+contributed the support for SSH protocol versions 1.5 and 2.0.