rshd(1M) rshd(1M)
NAME
rshd - remote shell server
SYNOPSIS
in.rshd host.port
DESCRIPTION
The rshd command is the server for the rsh(1) program. The
server provides remote execution facilities with
authentication based on privileged port numbers.
Files
/etc/hosts.equiv
Diagnostics
The following diagnostic messages are returned on the
connection associated with the stderr, 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 9 below upon
successful completion of all the steps prior to the command
execution).
locuser too long
The name of the user on the client's machine is longer
than 16 characters.
remuser too long
The name of the user on the remote machine is longer
than 16 characters.
command too long
The command line passed exceeds the size of the argument
list (as configured into the system).
Hostname for your address unknown.
No entry in the host name database existed for the
client's machine.
Login incorrect.
No password file entry for the user name existed.
Permission denied.
The authentication procedure described below failed.
Copyright 1994 Novell, Inc. Page 1
rshd(1M) rshd(1M)
Can't make pipe.
The pipe needed for the stderr was not created.
Try again.
A fork by the server failed.
USAGE
rshd is invoked by inetd(1M) each time a shell service is
requested, and executes the following protocol:
1) The server checks the client's source port. If the port
is not in the range
0-1023, the server aborts the connection. The clients
host address (in hex) and port number (in decimal) are
the argument passed to rshd.
2) The server reads characters from the socket up to a null
( \0 ) byte. The resultant string is interpreted as an
ASCII number, base 10.
3) 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 stderr. A second connection is then
created to the specified port on the client's machine.
The source port of this second connection is also in the
range 0-1023.
4) The server checks the client's source address. If the
address is associated with a host for which no
corresponding entry exists in the host name data base
[see hosts(4)], the server aborts the connection.
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 server's
machine.
6) A null terminated user name of at most 16 characters is
retrieved on the initial socket. This user name is
interpreted as the user identity on the client's
machine.
7) 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.
Copyright 1994 Novell, Inc. Page 2
rshd(1M) rshd(1M)
8) rshd then validates the user according to the following
steps. The remote user name is looked up in the
password file and a chdir is performed to the user's
home directory. If the lookup or fails, the connection
is terminated. If the chdir fails, it does a chdir to /
(root). If the user is not root (UID is 0), the file
/etc/hosts.equiv is consulted for a list of hosts
considered equivalent. If the client's host name is
present in this file, the authentication is considered
successful. If the lookup fails, or the user is a
privileged user, then the file .rhosts in the home
directory of the remote user is checked for the machine
name and identity of the user on the client's machine.
If this lookup fails, the connection is terminated.
9) A null byte is returned on the connection associated
with the stderr and the command line is passed to the
normal login shell of the user. The shell inherits the
network connections established by rshd.
REFERENCES
rsh(1)
NOTICES
The authentication procedure used here assumes the integrity
of each client machine and the connecting medium. This is
insecure, but is useful in an ``open'' environment.
If a remote user does not have a home directory, the root
directory (/) becomes the user's home directory.
A facility to allow all data exchanges to be encrypted should
be present.
Copyright 1994 Novell, Inc. Page 3