rexecd(1M)        MISC. REFERENCE MANUAL PAGES         rexecd(1M)



NAME
     rexecd - remote execution server

SYNOPSIS
     in.rexecd host.port

DESCRIPTION
     rexecd is the server for the rexec(3N) routine.  The  server
     provides  remote  execution  facilities  with authentication
     based on user names and encrypted passwords.  It is  invoked
     automatically  as needed by inetd(1M), and then executes the
     following protocol:

     1)   The server reads characters from the  socket  up  to  a
          null (\0) byte.  The resultant string is interpreted as
          an ASCII number, base 10.

     2)   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.

     3)   A null terminated user name of at most 16 characters is
          retrieved on the initial socket.

     4)   A null terminated, encrypted, password of  at  most  16
          characters is retrieved on the initial socket.

     5)   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.

     6)   rexecd then validates the user as is done at login time
          and,  if  the authentication was successful, changes to
          the user's home directory, and establishes the user and
          group  protections  of the user.  If any of these steps
          fail the connection is aborted with a  diagnostic  mes-
          sage returned.

     7)   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 rexecd.

SEE ALSO
     inetd(1M)

DIAGNOSTICS
     All diagnostic messages are returned on the connection asso-
     ciated  with the stderr, after which any network connections
     are closed.  An error is indicated by a leading byte with  a



                       Last change: TCP/IP                      1

rexecd(1M)        MISC. REFERENCE MANUAL PAGES         rexecd(1M)



     value  of  1  (0 is returned in step 7 above upon successful
     completion of all the steps prior to the command execution).

     username too long
          The name is longer than 16 characters.

     password too long
          The password is longer than 16 characters.

     command too long
          The command line passed exceeds the size of  the  argu-
          ment list (as configured into the system).

     Login incorrect.
          No password file entry for the user name existed.

     Password incorrect.
          The wrong password was supplied.

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

     Try again.
          A fork by the server failed.

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

NOTES
     Indicating Login incorrect as opposed to Password  incorrect
     is  a  security breach which allows people to probe a system
     for users with null passwords.

     A facility to allow  all  data  exchanges  to  be  encrypted
     should be present.




















                       Last change: TCP/IP                      2