.\" from: kshd.8,v 4.1 89/01/23 11:39:41 jtkohl Exp $ .\" $Id: kshd.8,v 1.2 1994/07/19 19:27:50 g89r4222 Exp $ .\" .\" Copyright (c) 1983 The Regents of the University of California. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms are permitted .\" provided that the above copyright notice and this paragraph are .\" duplicated in all such forms and that any documentation, .\" advertising materials, and other materials related to such .\" distribution and use acknowledge that the software was developed .\" by the University of California, Berkeley. The name of the .\" University may not be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED .\" WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. .\" .\" @(#)rshd.8 6.5 (Berkeley) 9/19/88 .\" .TH KSHD 8 "Kerberos Version 4.0" "MIT Project Athena" .UC 5 .SH NAME kshd \- remote shell server .SH SYNOPSIS .B /usr/etc/kshd .SH DESCRIPTION .I Kshd is the server for the .IR kcmd (3) routine and, consequently, for the .IR rsh (1) program. The server provides remote execution facilities with authentication based on Kerberos. .PP .I Kshd listens for service requests at the port indicated in the ``kshell'' service specification; see .IR services (5). When a service request is received the following protocol is initiated: .IP 1) The server reads characters from the socket up to a null (`\e0') byte. The resultant string is interpreted as an ASCII number, base 10. .IP 2) If the number received in step 1 is non-zero, it is interpreted as the port number of a secondary stream to be used for the .BR stderr . A second connection is then created to the specified port on the client's machine. .IP 3) The server checks the client's source address and requests the corresponding host name (see .IR gethostbyaddr (3N), .IR hosts (5) and .IR named (8)). If the hostname cannot be determined, the dot-notation representation of the host address is used. .IP 4) A Kerberos ticket/authenticator pair are retrieved on the initial socket. .IP 5) A null terminated user name of at most 16 characters is retrieved on the initial socket. This user name is interpreted as a user identity to use on the .BR server 's machine. .IP 6) A null terminated command to be passed to a shell is retrieved on the initial socket. The length of the command is limited by the upper bound on the size of the system's argument list. .IP 7) .I Kshd then validates the user according to the following steps. The local (server-end) user name is looked up in the password file and a .I chdir is performed to the user's home directory. If either the lookup or .I chdir fail, the connection is terminated. The \&.klogin file in the home directory is used to mediate access to the account (via \fIkuserok\fP(3)) by the Kerberos principal named in the ticket/authenticator. If this authorization check fails, the connection is terminated. .IP 8) A null byte is returned on the initial socket and the command line is passed to the normal login shell of the user. The shell inherits the network connections established by .IR kshd . .SH DIAGNOSTICS Except for the last one listed below, all diagnostic messages are returned on the initial socket, after which any network connections are closed. An error is indicated by a leading byte with a value of 1 (0 is returned in step 8 above upon successful completion of all the steps prior to the execution of the login shell). .PP .B ``remuser too long'' .br The name of the user on the remote machine is longer than 16 characters. .PP .B ``command too long '' .br The command line passed exceeds the size of the argument list (as configured into the system). .PP .B ``Login incorrect.'' .br No password file entry for the user name existed. .PP .B ``No remote directory.'' .br The .I chdir command to the home directory failed. .PP .B ``Permission denied.'' .br The authorization procedure described above failed. .PP .B ``Can't make pipe.'' .br The pipe needed for the .BR stderr , wasn't created. .PP .B ``Try again.'' .br A .I fork by the server failed. .PP .B ``: ...'' .br The user's login shell could not be started. This message is returned on the connection associated with the .BR stderr , and is not preceded by a flag byte. .SH SEE ALSO rsh(1), kerberos(3), kuserok(3) .SH BUGS A facility to allow all data exchanges to be encrypted should be present. .PP A more extensible protocol should be used.