# Copyright (c) 2009, Mario Vilas
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# modification, are permitted provided that the following conditions are met:
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# $Id: example9.py 160 2009-05-16 01:46:37Z qvasimodo $

# Example #9
# http://apps.sourceforge.net/trac/winappdbg/wiki/wiki/Debugging#Example9:hookingafunction

from winappdbg import Debug, EventHandler


# This function will be called when the hooked function is entered
def wsprintf( event, ra, lpOut, lpFmt ):

    # Get the format string
    lpFmt = event.get_process().peek_string( lpFmt, fUnicode = True )

    # Get the vararg parameters
    count      = lpFmt.replace( '%%', '%' ).count( '%' )
    parameters = event.get_thread().read_stack_dwords( count, offset = 3 )

    # Show a message to the user
    showparams = ", ".join( [ hex(x) for x in parameters ] )
    print "wsprintf( %r, %s );" % ( lpFmt, showparams )


class MyEventHandler( EventHandler ):

    def load_dll( self, event ):

        # Get the new module object
        module = event.get_module()

        # If it's user32...
        if module.match_name("user32.dll"):

            # Get the process ID
            pid = event.get_pid()

            # Get the address of wsprintf
            address = module.resolve( "wsprintfW" )

            # Hook the wsprintf function
            event.debug.hook_function( pid, address, wsprintf, paramCount = 2 )

            # Use stalk_function instead of hook_function
            # to be notified only the first time the function is called
            #
            # event.debug.stalk_function( pid, address, wsprintf, paramCount = 2 )


def simple_debugger( argv ):

    # Instance a Debug object, passing it the MyEventHandler instance
    debug = Debug( MyEventHandler() )
    try:

        # Start a new process for debugging
        debug.execv( argv )

        # Wait for the debugee to finish
        debug.loop()

    # Stop the debugger
    finally:
        debug.stop()


# When invoked from the command line,
# the first argument is an executable file,
# and the remaining arguments are passed to the newly created process
if __name__ == "__main__":
    import sys
    simple_debugger( sys.argv[1:] )
