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 5/12/88                                                 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.




Printed 5/12/88                                                 2

RSHD(8N)                COMMAND REFERENCE                RSHD(8N)



     Permission denied.
                  The authentication procedure described above
                  failed.

     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), and inetd(8n).



















Printed 5/12/88                                                 3

%%index%%
na:264,78;
sy:342,195;
de:537,2529;3402,1436;
di:4838,1493;6667,467;
rv:7134,775;
ca:7909,266;
se:8175,170;
%%index%%000000000141