rshd(8c)																  rshd(8c)

Name
       rshd - remote shell server

Syntax
       /etc/rshd

Description
       The command is the server for the routine and, consequently, for the program.  The server provides remote execution facilities with authen-
       tication based on privileged port numbers.

       The is invoked by when it receives a connection on the port indicated in  the  cmd  service  specification.   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 (`') 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 the server aborts the connection.  For further information, see

       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 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.

       8)     The command validates the user according to the following steps.	The remote user name is looked up in the password file	and  a	is
	      performed  to  the user's home directory.  If either the lookup or fail, the connection is terminated.  If the user is not the supe-
	      ruser, (user id 0), the file or is consulted for a list of hosts considered equivalent.  If the client's host name is in this  file,
	      the  authentication  is considered successful.  If the lookup fails, or the user is the superuser, the file 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 the lookup fails, the connec-
	      tion 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

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 command to the home directory failed.

       Permission denied.
       The authentication procedure described above failed.

       Can't make pipe.
       The pipe needed for the stderr was not created.

       Try again.
       A fork by the server failed.

       /bin/sh: ...
       The user's login shell could not be started.

Restrictions
       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(1c), rcmd(3x), services(5), inetd(8c)

																	  rshd(8c)