rlogind.tproj/rlogind.8

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  32 .\"     @(#)rlogind.8   8.1 (Berkeley) 6/4/93
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  34 .Dd June 4, 1993
  35 .Dt RLOGIND 8
  36 .Os BSD 4.2
  37 .Sh NAME
  38 .Nm rlogind
  39 .Nd remote login server
  40 .Sh SYNOPSIS
  41 .Nm rlogind
  42 .Op Fl aln
  43 .Sh DESCRIPTION
  44 .Nm Rlogind
  45 is the server for the
  46 .Xr rlogin 1
  47 program.  The server provides a remote login facility
  48 with authentication based on privileged port numbers from trusted hosts.
  49 .Pp
  50 Options supported by
  51 .Nm rlogind :
  52 .Bl -tag -width Ds
  53 .It Fl a
  54 Ask hostname for verification.
  55 .It Fl l
  56 Prevent any authentication based on the user's
  57 .Dq Pa .rhosts
  58 file, unless the user is logging in as the superuser.
  59 .It Fl n
  60 Disable keep-alive messages.
  61 .El
  62 .Pp
  63 .Nm Rlogind
  64 listens for service requests at the port indicated in
  65 the ``login'' service specification; see
  66 .Xr services 5 .
  67 When a service request is received the following protocol
  68 is initiated:
  69 .Bl -enum
  70 .It
  71 The server checks the client's source port.
  72 If the port is not in the range 512-1023, the server
  73 aborts the connection.
  74 .It
  75 The server checks the client's source address
  76 and requests the corresponding host name (see
  77 .Xr gethostbyaddr 3 ,
  78 .Xr hosts 5
  79 and
  80 .Xr named 8 ) .
  81 If the hostname cannot be determined,
  82 the dot-notation representation of the host address is used.
  83 If the hostname is in the same domain as the server (according to
  84 the last two components of the domain name),
  85 or if the
  86 .Fl a
  87 option is given,
  88 the addresses for the hostname are requested,
  89 verifying that the name and address correspond.
  90 Normal authentication is bypassed if the address verification fails.
  91 .El
  92 .Pp
  93 Once the source port and address have been checked,
  94 .Nm rlogind
  95 proceeds with the authentication process described in
  96 .Xr rshd 8 .
  97 It then allocates a pseudo terminal (see
  98 .Xr pty 4 ) ,
  99 and manipulates file descriptors so that the slave
 100 half of the pseudo terminal becomes the
 101 .Em stdin ,
 102 .Em stdout ,
 103 and
 104 .Em stderr
 105 for a login process.
 106 The login process is an instance of the
 107 .Xr login 1
 108 program, invoked with the
 109 .Fl f
 110 option if authentication has succeeded.
 111 If automatic authentication fails, the user is
 112 prompted to log in as if on a standard terminal line.
 113 .Pp
 114 The parent of the login process manipulates the master side of
 115 the pseudo terminal, operating as an intermediary
 116 between the login process and the client instance of the
 117 .Xr rlogin
 118 program.  In normal operation, the packet protocol described
 119 in
 120 .Xr pty 4
 121 is invoked to provide
 122 .Ql ^S/^Q
 123 type facilities and propagate
 124 interrupt signals to the remote programs.  The login process
 125 propagates the client terminal's baud rate and terminal type,
 126 as found in the environment variable,
 127 .Ql Ev TERM ;
 128 see
 129 .Xr environ 7 .
 130 The screen or window size of the terminal is requested from the client,
 131 and window size changes from the client are propagated to the pseudo terminal.
 132 .Pp
 133 Transport-level keepalive messages are enabled unless the
 134 .Fl n
 135 option is present.
 136 The use of keepalive messages allows sessions to be timed out
 137 if the client crashes or becomes unreachable.
 138 .Sh DIAGNOSTICS
 139 All initial diagnostic messages are indicated
 140 by a leading byte with a value of 1,
 141 after which any network connections are closed.
 142 If there are no errors before
 143 .Xr login
 144 is invoked, a null byte is returned as in indication of success.
 145 .Bl -tag -width Ds
 146 .It Sy Try again.
 147 A
 148 .Xr fork
 149 by the server failed.
 150 .El
 151 .Sh SEE ALSO
 152 .Xr login 1 ,
 153 .Xr ruserok 3 ,
 154 .Xr rshd 8
 155 .Sh BUGS
 156 The authentication procedure used here assumes the integrity
 157 of each client machine and the connecting medium.  This is
 158 insecure, but is useful in an ``open'' environment.
 159 .Pp
 160 A facility to allow all data exchanges to be encrypted should be
 161 present.
 162 .Pp
 163 A more extensible protocol should be used.
 164 .Sh HISTORY
 165 The
 166 .Nm
 167 command appeared in
 168 .Bx 4.2 .