Starting  with  release  2.1.0  it  is possible to implement a private
   authentication  mechanism  without.  The  private  authentication mode
   disables  all  the  other  authentication  modes  (standard,  ssh  and
   certificates).

    On the client side

   Write your authentication code in the file bbftp/bbftp_private_user.c.

     * extern char *username;
       This  variable contains the username given on the command line (-u
       option).
     * extern char *privatestr;
       This  variable  contains the string given on the command line with
       the -P option (or NULL if not used).
     * int bbftp_private_getargs(char *logmessage)
       This routine is called at the begining of the login sequence (just
       before  setting  the  process in background if needed) in order to
       allow the programmer to set variables or to request input from the
       user.
       The return code and the variables are explained in the file.
       After  having  called  this routine the main program will exchange
       RSA  keys  with  the  server  in  order to crypt all messages sent
       during  the  authentication procedure. Then the hand will be given
       to the next routine :
     * int bbftp_private_auth(char *logmessage)
       This  routine will allow the user exchange data between the client
       and   the   server.   For   that   it   will   use   two  routines
       bbftp_private_recv  and  bbftp_private_send whose descriptions are
       given in the bbftp_private_user.c file.
       When  all this data exchange has ended, the routine will return to
       main  code  with  a  return code of 0 in case of success or with a
       return  code  of  -1  and  the string logmessage filled in case of
       error.

    On the server side

   Write your authentication code in the file
   bbftpd/bbftpd_private_user.c.

     * extern char currentusername[MAXLEN];
       It has to be filled by the bbftpd_private_auth routine.
     * int bbftpd_private_auth(char *logmessage)
       As  on  the  client  side,  this  routine will exchange data using
       bbftpd_private_send   and   bbftpd_private_recv   routines  (whose
       decriptions  are  given in the bbftpd_private_user.c file), do all
       checks needed and return 0 in case of success or -1 and the string
       logmessage filled in case of error.

    Building BBFTP with a private authentication module

    On the client side

   In the bbftpc directory, run
   % ./configure --enable-authentication=private

   Then run:
   % make

   Then run:
   % make install

    On the server side

   In the bbftpd directory, run
   % ./configure --enable-authentication=private

   Then run:
   % make

   Then run:
   % make install

   See  the installation pages for the client and for the server for more
   information about the BBFTP build process.