remshd(1M)                                             remshd(1M)



     NAME
          remshd - remote shell server

     SYNOPSIS
          /etc/remshd

     DESCRIPTION
          remshd is the server for the rcmd(3N) routine and,
          consequently, for remsh(1N).  The server provides remote
          execution facilities with authentication based on privileged
          port numbers.

          remshd listens for service requests at the port indicated in
          the cmd service specification; see services(4N).  When
          remshd receives a service request, it initiates the
          following protocol:

          1. remshd checks the client's source port.  If the port is
             not in the range 0-1023, it aborts the connection.

          2. remshd reads characters from the socket up to a null
             (``\0'') byte. It interprets the resultant string as an
             ASCII number, base 10.

          3. If remshd receives a port number (in step 1) which is
             non-zero, it interprets it as the port number of a
             secondary stream to use for the stderr.  It then creates
             a second connection to the specified port on the client's
             machine. The source port of this second connection is
             also in the range 0-1023.

          4. remshd checks the client's source address.  If the
             address is associated with a host which has no
             corresponding entry in the host name data base (see
             hosts(4N)), remshd aborts the connection.

          5. remshd retrieves a null-terminated user name up to 16
             characters long on the initial socket. It interprets this
             user name as a user identity to use on the server's
             machine.

          6. remshd retrieves a null-terminated user name up to 16
             characters long on the initial socket. It interprets this
             user name as the user identity on the client's machine.

          7. remshd retrieves a null-terminated command on the initial
             socket to passed to a shell.  The length of the command
             is limited by the size of the system's argument list.

          8. remshd validates the user according to the following
             steps.  It looks up the remote user name in the password
             file and performs a chdir to the user's home directory.



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     remshd(1M)                                             remshd(1M)



             If either the lookup or chdir fail, it terminates the
             connection.  If the user is not the super-user, (user id
             0), it consults the file /etc/hosts.equiv for a list of
             ``equivalent'' hosts.  If the client's host name is in
             this file, the authentication is considered successful.
             If the lookup fails, or the user is the super-user, it
             checks the file .rhosts in the home directory of the
             remote user for the machine name and identity of the user
             on the client's machine. If this lookup fails, it
             terminates the connection.

          9. remshd returns a null byte on the connection associated
             with the stderr and passes the command line to the normal
             login shell of the user. The shell inherits the network
             connections established by remshd.

     DIAGNOSTICS
          remshd returns all diagnostic messages on the connection
          associated with the stderr, after which it closes any
          network connections.  It indicates an error by a leading
          byte with a value of 1 (it returns 0 in step 9 above if it
          has successfully completed all the steps up to 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.
          There is no entry in the host name database for the client's
          machine.

          Login incorrect.
          There is no password file entry for the user name.

          No remote directory.
          The chdir command to the home directory failed.

          Permission denied.
          The authentication procedure described above failed.

          Can't make pipe.
          The pipe needed for the stderr, wasn't created.




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     remshd(1M)                                             remshd(1M)



          Try again.
          A fork by the server failed.

          /bin/sh: ...
          Could not start the user's login shell.

     FILES
          /etc/remshd

     SEE ALSO
          remsh(1N), rcmd(3N).

     BUGS
          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.

          There should be a facility allowing all data exchanges to be
          encrypted.




































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