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Annotation of 43BSDTahoe/man/man8/rshd.8, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)rshd.8      6.4 (Berkeley) 10/25/87
        !             6: .\"
        !             7: .TH RSHD 8C "October 25, 1987"
        !             8: .UC 5
        !             9: .SH NAME
        !            10: rshd \- remote shell server
        !            11: .SH SYNOPSIS
        !            12: .B /etc/rshd
        !            13: .SH DESCRIPTION
        !            14: .I Rshd
        !            15: is the server for the 
        !            16: .IR rcmd (3X)
        !            17: routine and, consequently, for the
        !            18: .IR rsh (1C)
        !            19: program.  The server provides remote execution facilities
        !            20: with authentication based on privileged port numbers from trusted hosts.
        !            21: .PP
        !            22: .I Rshd
        !            23: listens for service requests at the port indicated in
        !            24: the ``cmd'' service specification; see
        !            25: .IR services (5).
        !            26: When a service request is received the following protocol
        !            27: is initiated:
        !            28: .IP 1)
        !            29: The server checks the client's source port.
        !            30: If the port is not in the range 0-1023, the server
        !            31: aborts the connection.
        !            32: .IP 2)
        !            33: The server reads characters from the socket up
        !            34: to a null (`\e0') byte.  The resultant string is
        !            35: interpreted as an ASCII number, base 10.
        !            36: .IP 3)
        !            37: If the number received in step 2 is non-zero,
        !            38: it is interpreted as the port number of a secondary
        !            39: stream to be used for the 
        !            40: .BR stderr .
        !            41: A second connection is then created to the specified
        !            42: port on the client's machine.  The source port of this
        !            43: second connection is also in the range 0-1023.
        !            44: .IP 4)
        !            45: The server checks the client's source address
        !            46: and requests the corresponding host name (see
        !            47: .IR gethostbyaddr (3N),
        !            48: .IR hosts (5)
        !            49: and
        !            50: .IR named (8)).
        !            51: If the hostname cannot be determined,
        !            52: the dot-notation representation of the host address is used.
        !            53: .IP 5)
        !            54: A null terminated user name of at most 16 characters
        !            55: is retrieved on the initial socket.  This user name
        !            56: is interpreted as the user identity on the
        !            57: .BR client 's
        !            58: machine.
        !            59: .IP 6)
        !            60: A null terminated user name of at most 16 characters
        !            61: is retrieved on the initial socket.  This user name
        !            62: is interpreted as a user identity to use on the
        !            63: .BR server 's
        !            64: machine.
        !            65: .IP 7)
        !            66: A null terminated command to be passed to a
        !            67: shell is retrieved on the initial socket.  The length of
        !            68: the command is limited by the upper bound on the size of
        !            69: the system's argument list.  
        !            70: .IP 8)
        !            71: .I Rshd
        !            72: then validates the user according to the following steps.
        !            73: The local (server-end) user name is looked up in the password file
        !            74: and a
        !            75: .I chdir
        !            76: is performed to the user's home directory.  If either
        !            77: the lookup or 
        !            78: .I chdir
        !            79: fail, the connection is terminated.
        !            80: If the user is not the super-user, (user id 0), the file 
        !            81: .I /etc/hosts.equiv
        !            82: is consulted for a list of hosts considered ``equivalent''.
        !            83: If the client's host name is present in this file, the
        !            84: authentication is considered successful.  If the lookup
        !            85: fails, or the user is the super-user, then the file
        !            86: .I .rhosts
        !            87: in the home directory of the remote user is checked for
        !            88: the machine name and identity of the user on the client's
        !            89: machine.  If this lookup fails, the connection is terminated.
        !            90: .IP 9)
        !            91: A null byte is returned on the initial socket
        !            92: and the command line is passed to the normal login
        !            93: shell of the user.  The
        !            94: shell inherits the network connections established
        !            95: by
        !            96: .IR rshd .
        !            97: .SH DIAGNOSTICS
        !            98: Except for the last one listed below,
        !            99: all diagnostic messages
        !           100: are returned on the initial socket,
        !           101: after which any network connections are closed.
        !           102: An error is indicated by a leading byte with a value of
        !           103: 1 (0 is returned in step 9 above upon successful completion
        !           104: of all the steps prior to the execution of the login shell).
        !           105: .PP
        !           106: .B ``locuser too long''
        !           107: .br
        !           108: The name of the user on the client's machine is
        !           109: longer than 16 characters.
        !           110: .PP
        !           111: .B ``remuser too long''
        !           112: .br
        !           113: The name of the user on the remote machine is
        !           114: longer than 16 characters.
        !           115: .PP
        !           116: .B ``command too long ''
        !           117: .br
        !           118: The command line passed exceeds the size of the argument
        !           119: list (as configured into the system).
        !           120: .PP
        !           121: .B ``Login incorrect.''
        !           122: .br
        !           123: No password file entry for the user name existed.
        !           124: .PP
        !           125: .B ``No remote directory.''
        !           126: .br
        !           127: The 
        !           128: .I chdir
        !           129: command to the home directory failed.
        !           130: .PP
        !           131: .B ``Permission denied.''
        !           132: .br
        !           133: The authentication procedure described above failed.
        !           134: .PP
        !           135: .B ``Can't make pipe.''
        !           136: .br
        !           137: The pipe needed for the 
        !           138: .BR stderr ,
        !           139: wasn't created.
        !           140: .PP
        !           141: .B ``Try again.''
        !           142: .br
        !           143: A
        !           144: .I fork
        !           145: by the server failed.
        !           146: .PP
        !           147: .B ``<shellname>: ...''
        !           148: .br
        !           149: The user's login shell could not be started.  This message is returned
        !           150: on the connection associated with the
        !           151: .BR stderr ,
        !           152: and is not preceded by a flag byte.
        !           153: .SH SEE ALSO
        !           154: rsh(1C),
        !           155: rcmd(3X)
        !           156: .SH BUGS
        !           157: The authentication procedure used here assumes the integrity
        !           158: of each client machine and the connecting medium.  This is
        !           159: insecure, but is useful in an ``open'' environment.
        !           160: .PP
        !           161: A facility to allow all data exchanges to be encrypted should be
        !           162: present.
        !           163: .PP
        !           164: A more extensible protocol should be used.

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