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Diff for /src/usr.bin/ssh/sshd.8 between version 1.51.2.4 and 1.51.2.5

version 1.51.2.4, 2001/03/12 15:44:17 version 1.51.2.5, 2001/03/21 18:53:16
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 .\" incompatible with the protocol description in the RFC file, it must be  .\" incompatible with the protocol description in the RFC file, it must be
 .\" called by a name other than "ssh" or "Secure Shell".  .\" called by a name other than "ssh" or "Secure Shell".
 .\"  .\"
 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.  .\" Copyright (c) 1999,2000 Markus Friedl.  All rights reserved.
 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.  .\" Copyright (c) 1999 Aaron Campbell.  All rights reserved.
 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.  .\" Copyright (c) 1999 Theo de Raadt.  All rights reserved.
 .\"  .\"
 .\" Redistribution and use in source and binary forms, with or without  .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions  .\" modification, are permitted provided that the following conditions
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 .Os  .Os
 .Sh NAME  .Sh NAME
 .Nm sshd  .Nm sshd
 .Nd OpenSSH secure shell daemon  .Nd OpenSSH ssh daemon
 .Sh SYNOPSIS  .Sh SYNOPSIS
 .Nm sshd  .Nm sshd
 .Op Fl diqD46  .Op Fl diqD46
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 .Op Fl V Ar client_protocol_id  .Op Fl V Ar client_protocol_id
 .Sh DESCRIPTION  .Sh DESCRIPTION
 .Nm  .Nm
 (Secure Shell Daemon) is the daemon program for  (SSH Daemon) is the daemon program for
 .Xr ssh 1 .  .Xr ssh 1 .
 Together these programs replace rlogin and rsh, and  Together these programs replace rlogin and rsh, and
 provide secure encrypted communications between two untrusted hosts  provide secure encrypted communications between two untrusted hosts
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 However, when the daemon starts, it does not generate a server key.  However, when the daemon starts, it does not generate a server key.
 Forward security is provided through a Diffie-Hellman key agreement.  Forward security is provided through a Diffie-Hellman key agreement.
 This key agreement results in a shared session key.  This key agreement results in a shared session key.
 The rest of the session is encrypted  The rest of the session is encrypted using a symmetric cipher, currently
 using a symmetric cipher, currently  Blowfish, 3DES, CAST128, Arcfour, 128 bit AES, or 256 bit AES.
 Blowfish, 3DES or CAST128 in CBC mode or Arcfour.  
 The client selects the encryption algorithm  The client selects the encryption algorithm
 to use from those offered by the server.  to use from those offered by the server.
 Additionally, session integrity is provided  Additionally, session integrity is provided
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 .Pp  .Pp
 .Nm  .Nm
 rereads its configuration file when it receives a hangup signal,  rereads its configuration file when it receives a hangup signal,
 .Dv SIGHUP .  .Dv SIGHUP ,
   by executing itself with the name it was started as, ie.
   .Pa /usr/sbin/sshd .
 .Pp  .Pp
 The options are as follows:  The options are as follows:
 .Bl -tag -width Ds  .Bl -tag -width Ds
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 authentication is allowed.  authentication is allowed.
 This option is only available for protocol version 2.  This option is only available for protocol version 2.
 .Pp  .Pp
   .It Cm ChallengeResponseAuthentication
   Specifies whether
   challenge response
   authentication is allowed.
   Currently there is only support for
   .Xr skey 1
   authentication.
   The default is
   .Dq yes .
 .It Cm Ciphers  .It Cm Ciphers
 Specifies the ciphers allowed for protocol version 2.  Specifies the ciphers allowed for protocol version 2.
 Multiple ciphers must be comma-separated.  Multiple ciphers must be comma-separated.
 The default is  The default is
 .Dq 3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes128-cbc .  .Dq aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour.
 .It Cm CheckMail  .It Cm CheckMail
 Specifies whether  Specifies whether
 .Nm  .Nm
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 can be used as wildcards in the patterns.  can be used as wildcards in the patterns.
 Only user names are valid; a numerical user ID isn't recognized.  Only user names are valid; a numerical user ID isn't recognized.
 By default login is allowed regardless of the user name.  By default login is allowed regardless of the user name.
 .It Cm PubkeyAuthentication  
 Specifies whether public key authentication is allowed.  
 The default is  
 .Dq yes .  
 Note that this option applies to protocol version 2 only.  
 .It Cm GatewayPorts  .It Cm GatewayPorts
 Specifies whether remote hosts are allowed to connect to ports  Specifies whether remote hosts are allowed to connect to ports
 forwarded for the client.  forwarded for the client.
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 The default is  The default is
 .Pp  .Pp
 .Bd -literal  .Bd -literal
   ``hmac-sha1,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,    ``hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,
     hmac-sha1-96,hmac-md5-96''      hmac-sha1-96,hmac-md5-96''
 .Ed  .Ed
 .It Cm MaxStartups  .It Cm MaxStartups
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 The default is  The default is
 .Dq no .  .Dq no .
 .It Cm PermitRootLogin  .It Cm PermitRootLogin
 Specifies whether the root can log in using  Specifies whether root can login using
 .Xr ssh 1 .  .Xr ssh 1 .
 The argument must be  The argument must be
 .Dq yes ,  .Dq yes ,
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 (which may be useful for taking remote backups even if root login is  (which may be useful for taking remote backups even if root login is
 normally not allowed). All other authentication methods are disabled  normally not allowed). All other authentication methods are disabled
 for root.  for root.
   .Pp
   If this option is set to
   .Dq no
   root is not allowed to login.
 .It Cm PidFile  .It Cm PidFile
 Specifies the file that contains the process identifier of the  Specifies the file that contains the process identifier of the
 .Nm  .Nm
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 Multiple versions must be comma-separated.  Multiple versions must be comma-separated.
 The default is  The default is
 .Dq 1 .  .Dq 1 .
 .It Cm RandomSeed  .It Cm PubkeyAuthentication
 Obsolete.  Specifies whether public key authentication is allowed.
 Random number generation uses other techniques.  The default is
   .Dq yes .
   Note that this option applies to protocol version 2 only.
 .It Cm ReverseMappingCheck  .It Cm ReverseMappingCheck
 Specifies whether  Specifies whether
 .Nm  .Nm
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 .It Cm ServerKeyBits  .It Cm ServerKeyBits
 Defines the number of bits in the server key.  Defines the number of bits in the server key.
 The minimum value is 512, and the default is 768.  The minimum value is 512, and the default is 768.
 .It Cm ChallengeResponseAuthentication  
 Specifies whether  
 challenge reponse  
 authentication is allowed.  
 Currently there is only support for  
 .Xr skey 1  
 authentication.  
 The default is  
 .Dq yes .  
 .It Cm StrictModes  .It Cm StrictModes
 Specifies whether  Specifies whether
 .Nm  .Nm
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 authentication.  authentication.
 .It Cm no-pty  .It Cm no-pty
 Prevents tty allocation (a request to allocate a pty will fail).  Prevents tty allocation (a request to allocate a pty will fail).
   .It Cm permitopen="host:port"
   Limit local
   .Li ``ssh -L''
   port-forwading such that it may only connect to the specified host and
   port. Multiple
   .Cm permitopen
   options may be applied seperated by commas. No pattern matching is
   performed on the specified hostnames, they must be literal domains or
   addresses.
 .El  .El
 .Ss Examples  .Ss Examples
 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar  1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
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 from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula  from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
 .Pp  .Pp
 command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi  command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
   .Pp
   permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23.\|.\|.\|2323
 .Sh SSH_KNOWN_HOSTS FILE FORMAT  .Sh SSH_KNOWN_HOSTS FILE FORMAT
 The  The
 .Pa /etc/ssh_known_hosts ,  .Pa /etc/ssh_known_hosts ,
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 .Nm sshd .  .Nm sshd .
 This file should be writable by root only, but it is recommended  This file should be writable by root only, but it is recommended
 (though not necessary) that it be world-readable.  (though not necessary) that it be world-readable.
 .It Pa /etc/ssh_host_key  .It Pa /etc/ssh_host_key, /etc/ssh_host_dsa_key, /etc/ssh_host_rsa_key
 Contains the private part of the host key.  These three files contain the private parts of the
 This file should only be owned by root, readable only by root, and not  (SSH1, SSH2 DSA, and SSH2 RSA) host keys.
   These files should only be owned by root, readable only by root, and not
 accessible to others.  accessible to others.
 Note that  Note that
 .Nm  .Nm
 does not start if this file is group/world-accessible.  does not start if this file is group/world-accessible.
 .It Pa /etc/ssh_host_key.pub  .It Pa /etc/ssh_host_key.pub, /etc/ssh_host_dsa_key.pub, /etc/ssh_host_rsa_key.pub
 Contains the public part of the host key.  There three files contain the public parts of the
 This file should be world-readable but writable only by  (SSH1, SSH2 DSA, and SSH2 RSA) host keys.
   These files should be world-readable but writable only by
 root.  root.
 Its contents should match the private part.  Their contents should match the respective private parts.
 This file is not  These files are not
 really used for anything; it is only provided for the convenience of  really used for anything; they are provided for the convenience of
 the user so its contents can be copied to known hosts files.  the user so their contents can be copied to known hosts files.
 These two files are created using  These files are created using
 .Xr ssh-keygen 1 .  .Xr ssh-keygen 1 .
 .It Pa /etc/primes  .It Pa /etc/primes
 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".  Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
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 authentication to check the public key of the host.  authentication to check the public key of the host.
 The key must be listed in one of these files to be accepted.  The key must be listed in one of these files to be accepted.
 The client uses the same files  The client uses the same files
 to verify that the remote host is the one it intended to connect.  to verify that it is connecting to the correct remote host.
 These files should be writable only by root/the owner.  These files should be writable only by root/the owner.
 .Pa /etc/ssh_known_hosts  .Pa /etc/ssh_known_hosts
 should be world-readable, and  should be world-readable, and
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  Added in v.1.51.2.5