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Annotation of 43BSDReno/foreign/src/rshd/rshd.8, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983, 1989 The Regents of the University of California.
        !             2: .\" All rights reserved.
        !             3: .\"
        !             4: .\" Redistribution and use in source and binary forms are permitted provided
        !             5: .\" that: (1) source distributions retain this entire copyright notice and
        !             6: .\" comment, and (2) distributions including binaries display the following
        !             7: .\" acknowledgement:  ``This product includes software developed by the
        !             8: .\" University of California, Berkeley and its contributors'' in the
        !             9: .\" documentation or other materials provided with the distribution and in
        !            10: .\" all advertising materials mentioning features or use of this software.
        !            11: .\" Neither the name of the University nor the names of its contributors may
        !            12: .\" be used to endorse or promote products derived from this software without
        !            13: .\" specific prior written permission.
        !            14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            17: .\"
        !            18: .\"    @(#)rshd.8      6.10 (Berkeley) 6/24/90
        !            19: .\"
        !            20: .TH RSHD 8 "June 24, 1990"
        !            21: .UC 5
        !            22: .SH NAME
        !            23: rshd \- remote shell server
        !            24: .SH SYNOPSIS
        !            25: .B rshd [-aln]
        !            26: .SH DESCRIPTION
        !            27: .I Rshd
        !            28: is the server for the 
        !            29: .IR rcmd (3)
        !            30: routine and, consequently, for the
        !            31: .IR rsh (1)
        !            32: program.  The server provides remote execution facilities
        !            33: with authentication based on privileged port numbers from trusted hosts.
        !            34: .PP
        !            35: .I Rshd
        !            36: listens for service requests at the port indicated in
        !            37: the ``cmd'' service specification; see
        !            38: .IR services (5).
        !            39: When a service request is received the following protocol
        !            40: is initiated:
        !            41: .IP 1)
        !            42: The server checks the client's source port.
        !            43: If the port is not in the range 512-1023, the server
        !            44: aborts the connection.
        !            45: .IP 2)
        !            46: The server reads characters from the socket up
        !            47: to a null (`\e0') byte.  The resultant string is
        !            48: interpreted as an ASCII number, base 10.
        !            49: .IP 3)
        !            50: If the number received in step 2 is non-zero,
        !            51: it is interpreted as the port number of a secondary
        !            52: stream to be used for the 
        !            53: .BR stderr .
        !            54: A second connection is then created to the specified
        !            55: port on the client's machine.  The source port of this
        !            56: second connection is also in the range 512-1023.
        !            57: .IP 4)
        !            58: The server checks the client's source address
        !            59: and requests the corresponding host name (see
        !            60: .IR gethostbyaddr (3),
        !            61: .IR hosts (5)
        !            62: and
        !            63: .IR named (8)).
        !            64: If the hostname cannot be determined,
        !            65: the dot-notation representation of the host address is used.
        !            66: If the hostname is in the same domain as the server (according to
        !            67: the last two components of the domain name),
        !            68: or if the
        !            69: .B \-a
        !            70: option is given,
        !            71: the addresses for the hostname are requested,
        !            72: verifying that the name and address correspond.
        !            73: If address verification fails, the connection is aborted
        !            74: with the message, ``Host address mismatch.''
        !            75: .IP 5)
        !            76: A null terminated user name of at most 16 characters
        !            77: is retrieved on the initial socket.  This user name
        !            78: is interpreted as the user identity on the
        !            79: .BR client 's
        !            80: machine.
        !            81: .IP 6)
        !            82: A null terminated user name of at most 16 characters
        !            83: is retrieved on the initial socket.  This user name
        !            84: is interpreted as a user identity to use on the
        !            85: .BR server 's
        !            86: machine.
        !            87: .IP 7)
        !            88: A null terminated command to be passed to a
        !            89: shell is retrieved on the initial socket.  The length of
        !            90: the command is limited by the upper bound on the size of
        !            91: the system's argument list.  
        !            92: .IP 8)
        !            93: .I Rshd
        !            94: then validates the user using
        !            95: .IR ruserok (3),
        !            96: which uses the file ``/etc/hosts.equiv'' and the ``.rhosts''
        !            97: file found in the user's home directory.  The
        !            98: .B \-l
        !            99: option prevents
        !           100: .IR ruserok (3)
        !           101: from doing any validation based on the user's ``.rhosts'' file,
        !           102: unless the user is the superuser.
        !           103: .IP 9)
        !           104: A null byte is returned on the initial socket
        !           105: and the command line is passed to the normal login
        !           106: shell of the user.  The
        !           107: shell inherits the network connections established
        !           108: by
        !           109: .IR rshd .
        !           110: .PP
        !           111: Transport-level keepalive messages are enabled unless the
        !           112: .B \-n
        !           113: option is present.
        !           114: The use of keepalive messages allows sessions to be timed out
        !           115: if the client crashes or becomes unreachable.
        !           116: .SH DIAGNOSTICS
        !           117: Except for the last one listed below,
        !           118: all diagnostic messages
        !           119: are returned on the initial socket,
        !           120: after which any network connections are closed.
        !           121: An error is indicated by a leading byte with a value of
        !           122: 1 (0 is returned in step 9 above upon successful completion
        !           123: of all the steps prior to the execution of the login shell).
        !           124: .PP
        !           125: .B ``locuser too long''
        !           126: .br
        !           127: The name of the user on the client's machine is
        !           128: longer than 16 characters.
        !           129: .PP
        !           130: .B ``remuser too long''
        !           131: .br
        !           132: The name of the user on the remote machine is
        !           133: longer than 16 characters.
        !           134: .PP
        !           135: .B ``command too long ''
        !           136: .br
        !           137: The command line passed exceeds the size of the argument
        !           138: list (as configured into the system).
        !           139: .PP
        !           140: .B ``Login incorrect.''
        !           141: .br
        !           142: No password file entry for the user name existed.
        !           143: .PP
        !           144: .B ``No remote directory.''
        !           145: .br
        !           146: The 
        !           147: .I chdir
        !           148: command to the home directory failed.
        !           149: .PP
        !           150: .B ``Permission denied.''
        !           151: .br
        !           152: The authentication procedure described above failed.
        !           153: .PP
        !           154: .B ``Can't make pipe.''
        !           155: .br
        !           156: The pipe needed for the 
        !           157: .BR stderr ,
        !           158: wasn't created.
        !           159: .PP
        !           160: .B ``Can't fork; try again.''
        !           161: .br
        !           162: A
        !           163: .I fork
        !           164: by the server failed.
        !           165: .PP
        !           166: .B ``<shellname>: ...''
        !           167: .br
        !           168: The user's login shell could not be started.  This message is returned
        !           169: on the connection associated with the
        !           170: .BR stderr ,
        !           171: and is not preceded by a flag byte.
        !           172: .SH SEE ALSO
        !           173: rsh(1), rcmd(3), ruserok(3)
        !           174: .SH BUGS
        !           175: The authentication procedure used here assumes the integrity
        !           176: of each client machine and the connecting medium.  This is
        !           177: insecure, but is useful in an ``open'' environment.
        !           178: .PP
        !           179: A facility to allow all data exchanges to be encrypted should be
        !           180: present.
        !           181: .PP
        !           182: A more extensible protocol (such as Telnet) should be used.

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