rexecd(1M)                       (TCP/IP)                        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)                       (TCP/IP)                        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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