RSHD(8N) COMMAND REFERENCE RSHD(8N)
NAME
rshd - remote shell server
SYNOPSIS
/etc/rshd
DESCRIPTION
Rshd is the server for the rcmd(3n) routine and,
consequently, for the rsh(1n) program. The server provides
remote execution facilities with authentication based on
privileged port numbers.
Tcpd spawns an Rshd process for service requests at the port
indicated in the cmd service specification; see
services(5n). When a service request is received the
following protocol is initiated:
1) The server checks the client's source port. If the
port is not in the range 0-1023, the server aborts the
connection.
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(5n)), 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.
Printed 10/17/86 1
RSHD(8N) COMMAND REFERENCE RSHD(8N)
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 either the lookup or chdir fail,
the connection is terminated. If the user is not the
super-user, (user ID 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 the
super-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.
DIAGNOSTICS
All 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 above 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.
No remote directory.
The chdir command to the home directory failed.
Permission denied.
The authentication procedure described above failed.
Printed 10/17/86 2
RSHD(8N) COMMAND REFERENCE RSHD(8N)
Can't make pipe.
The pipe needed for the stderr, wasn't created.
Try again.
A fork by the server failed.
/bin/sh: ...
The user's login shell could not be started.
RETURN VALUE
[0] Rshd is running.
[1] Rshd is not running.
[USAGE] Incorrect command line syntax. Execution
terminated.
[P_ERR] A system error occurred. Execution
terminated. See intro(2) for more
information on system errors.
[NP_WARN] An error warranting a warning message
occurred. Execution continues.
[NP_ERR] An error occurred that was not a system
error. Execution terminated.
CAVEATS
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.
SEE ALSO
rsh(1n), rcmd(3n), inetd(8n).
Printed 10/17/86 3
%%index%%
na:72,62;
sy:134,127;
de:261,2308;2713,1292;
di:4005,1391;5540,292;
rv:5832,673;
ca:6505,238;
se:6743,140;
%%index%%000000000140