rexecd(1M)             UNIX System V(Internet Utilities)             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 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.

SEE ALSO
      inetd(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).




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rexecd(1M)             UNIX System V(Internet Utilities)             rexecd(1M)


      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 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.























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