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Diff for /src/usr.bin/ssh/ssh.1 between version 1.48 and 1.49

version 1.48, 2000/05/03 18:04:39 version 1.49, 2000/05/03 22:01:09
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 connects and logs into the specified  connects and logs into the specified
 .Ar hostname .  .Ar hostname .
 The user must prove  The user must prove
 his/her identity to the remote machine using one of several methods.  his/her identity to the remote machine using one of several methods
   depending on the protocol version used:
 .Pp  .Pp
   .Ss SSH protocol version 1
   .Pp
 First, if the machine the user logs in from is listed in  First, if the machine the user logs in from is listed in
 .Pa /etc/hosts.equiv  .Pa /etc/hosts.equiv
 or  or
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 .Pa hosts.equiv  .Pa hosts.equiv
 method combined with RSA-based host authentication.  method combined with RSA-based host authentication.
 It means that if the login would be permitted by  It means that if the login would be permitted by
 .Pa \&.rhosts ,  .Pa $HOME/.rhosts ,
 .Pa \&.shosts ,  .Pa $HOME/.shosts ,
 .Pa /etc/hosts.equiv ,  .Pa /etc/hosts.equiv ,
 or  or
 .Pa /etc/shosts.equiv ,  .Pa /etc/shosts.equiv ,
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 spoofing, DNS spoofing and routing spoofing.  spoofing, DNS spoofing and routing spoofing.
 [Note to the administrator:  [Note to the administrator:
 .Pa /etc/hosts.equiv ,  .Pa /etc/hosts.equiv ,
 .Pa \&.rhosts ,  .Pa $HOME/.rhosts ,
 and the rlogin/rsh protocol in general, are inherently insecure and should be  and the rlogin/rsh protocol in general, are inherently insecure and should be
 disabled if security is desired.]  disabled if security is desired.]
 .Pp  .Pp
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 The user creates his/her RSA key pair by running  The user creates his/her RSA key pair by running
 .Xr ssh-keygen 1 .  .Xr ssh-keygen 1 .
 This stores the private key in  This stores the private key in
 .Pa \&.ssh/identity  .Pa $HOME/.ssh/identity
 and the public key in  and the public key in
 .Pa \&.ssh/identity.pub  .Pa $HOME/.ssh/identity.pub
 in the user's home directory.  in the user's home directory.
 The user should then copy the  The user should then copy the
 .Pa identity.pub  .Pa identity.pub
 to  to
 .Pa \&.ssh/authorized_keys  .Pa $HOME/.ssh/authorized_keys
 in his/her home directory on the remote machine (the  in his/her home directory on the remote machine (the
 .Pa authorized_keys  .Pa authorized_keys
 file corresponds to the conventional  file corresponds to the conventional
 .Pa \&.rhosts  .Pa $HOME/.rhosts
 file, and has one key  file, and has one key
 per line, though the lines can be very long).  per line, though the lines can be very long).
 After this, the user can log in without giving the password.  After this, the user can log in without giving the password.
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 host for checking; however, since all communications are encrypted,  host for checking; however, since all communications are encrypted,
 the password cannot be seen by someone listening on the network.  the password cannot be seen by someone listening on the network.
 .Pp  .Pp
   .Ss SSH protocol version 2
   .Pp
   When a user connects using the protocol version 2
   different authentication methods are available:
   At first, the client attempts to authenticate using the public key method.
   If this method fails password authentication is tried.
   .Pp
   The public key method is similar to RSA authentication described
   in the previous section except that the DSA algorithm is used
   instead of the patented RSA algorithm.
   The client uses his private DSA key
   .Pa $HOME/.ssh/id_dsa
   to sign the session identifier and sends the result to the server.
   The server checks whether the matching public key is listed in
   .Pa $HOME/.ssh/authorized_keys2
   and grants access if both the key is found and the signature is correct.
   The session identifier is derived from a shared Diffie-Hellman value
   and is only known to the client and the server.
   .Pp
   If public key authentication fails or is not available a password
   can be sent encrypted to the remote host for proving the user's identity.
   This protocol 2 implementation does not yet support Kerberos or
   S/Key authentication.
   .Pp
   Protocol 2 provides additional mechanisms for confidentiality
   (the traffic is encrypted using 3DES, blowfish, cast128 or arcfour)
   and integrity (hmac-sha1, hmac-md5).
   Note that protocol 1 lacks a strong mechanism for ensuring the
   integrity of the connection.
   .Pp
   .Ss Login session and remote execution
   .Pp
 When the user's identity has been accepted by the server, the server  When the user's identity has been accepted by the server, the server
 either executes the given command, or logs into the machine and gives  either executes the given command, or logs into the machine and gives
 the user a normal shell on the remote machine.  the user a normal shell on the remote machine.
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 of  of
 .Nm ssh .  .Nm ssh .
 .Pp  .Pp
   .Ss X11 and TCP forwarding
   .Pp
 If the user is using X11 (the  If the user is using X11 (the
 .Ev DISPLAY  .Ev DISPLAY
 environment variable is set), the connection to the X11 display is  environment variable is set), the connection to the X11 display is
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 One possible application of TCP/IP forwarding is a secure connection to an  One possible application of TCP/IP forwarding is a secure connection to an
 electronic purse; another is going trough firewalls.  electronic purse; another is going trough firewalls.
 .Pp  .Pp
   .Ss Server authentication
   .Pp
 .Nm  .Nm
 automatically maintains and checks a database containing RSA-based  automatically maintains and checks a database containing
 identifications for all hosts it has ever been used with.  identifications for all hosts it has ever been used with.
 The database is stored in  RSA host keys are stored in
 .Pa \&.ssh/known_hosts  .Pa $HOME/.ssh/known_hosts
   and
   DSA host keys are stored in
   .Pa $HOME/.ssh/known_hosts2
 in the user's home directory.  in the user's home directory.
 Additionally, the file  Additionally, the files
 .Pa /etc/ssh_known_hosts  .Pa /etc/ssh_known_hosts
 is automatically checked for known hosts.  and
   .Pa /etc/ssh_known_hosts2
   are automatically checked for known hosts.
 Any new hosts are automatically added to the user's file.  Any new hosts are automatically added to the user's file.
 If a host's identification  If a host's identification
 ever changes,  ever changes,
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 Selects the file from which the identity (private key) for  Selects the file from which the identity (private key) for
 RSA authentication is read.  RSA authentication is read.
 Default is  Default is
 .Pa \&.ssh/identity  .Pa $HOME/.ssh/identity
 in the user's home directory.  in the user's home directory.
 Identity files may also be specified on  Identity files may also be specified on
 a per-host basis in the configuration file.  a per-host basis in the configuration file.
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 .It Cm IdentityFile  .It Cm IdentityFile
 Specifies the file from which the user's RSA authentication identity  Specifies the file from which the user's RSA authentication identity
 is read (default  is read (default
 .Pa .ssh/identity  .Pa $HOME/.ssh/identity
 in the user's home directory).  in the user's home directory).
 Additionally, any identities represented by the authentication agent  Additionally, any identities represented by the authentication agent
 will be used for authentication.  will be used for authentication.
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 .It Cm IdentityFile2  .It Cm IdentityFile2
 Specifies the file from which the user's DSA authentication identity  Specifies the file from which the user's DSA authentication identity
 is read (default  is read (default
 .Pa .ssh/id_dsa  .Pa $HOME/.ssh/id_dsa
 in the user's home directory).  in the user's home directory).
 The file name may use the tilde  The file name may use the tilde
 syntax to refer to a user's home directory.  syntax to refer to a user's home directory.
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 .Dq 2 .  .Dq 2 .
 Multiple versions must be comma-separated.  Multiple versions must be comma-separated.
 The default is  The default is
 .Dq 1 .  .Dq 1,2 .
   This means that
   .Nm
   tries version 1 and falls back to version 2
   if version 1 is no available.
 .It Cm ProxyCommand  .It Cm ProxyCommand
 Specifies the command to use to connect to the server.  Specifies the command to use to connect to the server.
 The command  The command
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