1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)rexecd.8 6.5 (Berkeley) 3/16/91 33.\" $Id: rexecd.8,v 1.2 1993/08/01 07:40:04 mycroft Exp $ 34.\" 35.Dd March 16, 1991 36.Dt REXECD 8 37.Os BSD 4.2 38.Sh NAME 39.Nm rexecd 40.Nd remote execution server 41.Sh SYNOPSIS 42.Nm rexecd 43.Sh DESCRIPTION 44.Nm Rexecd 45is the server for the 46.Xr rexec 3 47routine. The server provides remote execution facilities 48with authentication based on user names and 49passwords. 50.Pp 51.Nm Rexecd 52listens for service requests at the port indicated in 53the ``exec'' service specification; see 54.Xr services 5 . 55When a service request is received the following protocol 56is initiated: 57.Bl -enum 58.It 59The server reads characters from the socket up 60to a NUL 61.Pq Ql \e0 62byte. The resultant string is 63interpreted as an 64.Tn ASCII 65number, base 10. 66.It 67If the number received in step 1 is non-zero, 68it is interpreted as the port number of a secondary 69stream to be used for the 70.Em stderr . 71A second connection is then created to the specified 72port on the client's machine. 73.It 74A NUL terminated user name of at most 16 characters 75is retrieved on the initial socket. 76.It 77A NUL terminated, unencrypted password of at most 7816 characters is retrieved on the initial socket. 79.It 80A NUL terminated command to be passed to a 81shell is retrieved on the initial socket. The length of 82the command is limited by the upper bound on the size of 83the system's argument list. 84.It 85.Nm Rexecd 86then validates the user as is done at login time 87and, if the authentication was successful, changes 88to the user's home directory, and establishes the user 89and group protections of the user. 90If any of these steps fail the connection is 91aborted with a diagnostic message returned. 92.It 93A NUL byte is returned on the initial socket 94and the command line is passed to the normal login 95shell of the user. The 96shell inherits the network connections established 97by 98.Nm rexecd . 99.El 100.Sh DIAGNOSTICS 101Except for the last one listed below, 102all diagnostic messages are returned on the initial socket, 103after which any network connections are closed. 104An error is indicated by a leading byte with a value of 1051 (0 is returned in step 7 above upon successful completion 106of all the steps prior to the command execution). 107.Pp 108.Bl -tag -width Ds 109.It Sy username too long 110The name is 111longer than 16 characters. 112.It Sy password too long 113The password is longer than 16 characters. 114.It Sy command too long 115The command line passed exceeds the size of the argument 116list (as configured into the system). 117.It Sy Login incorrect. 118No password file entry for the user name existed. 119.It Sy Password incorrect. 120The wrong was password supplied. 121.It Sy \&No remote directory. 122The 123.Xr chdir 124command to the home directory failed. 125.It Sy Try again. 126A 127.Xr fork 128by the server failed. 129.It Sy <shellname>: ... 130The user's login shell could not be started. 131This message is returned 132on the connection associated with the 133.Em stderr , 134and is not preceded by a flag byte. 135.El 136.Sh SEE ALSO 137.Xr rexec 3 138.Sh BUGS 139Indicating ``Login incorrect'' as opposed to ``Password incorrect'' 140is a security breach which allows people to probe a system for users 141with null passwords. 142.Pp 143A facility to allow all data and password exchanges to be encrypted should be 144present. 145.Sh HISTORY 146The 147.Nm 148command appeared in 149.Bx 4.2 . 150