rexecd(1M)                                                       rexecd(1M)

NAME
     rexecd, in.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 direc-
        tory, and establishes the user and group protections of the user.
        If any of these steps fail the connection is aborted with a diag-
        nostic message 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.















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rexecd(1M)                                                       rexecd(1M)

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 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 argument 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 secu-
     rity 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.

SEE ALSO
     inetd(1M).












Page 2                       Reliant UNIX 5.44                Printed 11/98