Enumerate users from web form

#!/usr/bin/python
#Author: Craig Freyman
#Description: Brute force usernames on a web form
#Version: 1.0
#Date: May 27, 2012
#Website: www.pwnag3.com

import urllib2,re,sys,os.path

def check_found_users():
        global append_or_overwrite
        if os.path.exists("found_users.txt"):
                append_or_overwrite = raw_input("\033[1;32m[*] Found an existing \"found_users.txt\" file. Press \"w\" to overwrite or \"a\" to append.\033[1;m\n")
        if append_or_overwrite not in ("w","a"):
                print "\033[1;31m[-] Please only press \"w\" or \"a\" .\033[1;m"
                check_found_users()

def check_resume():
        global resume_or_not
        global resume_start_word

        #simply check the current directory for our resume file
        if os.path.exists("resume_file.txt"):
                resume_or_not = raw_input("\033[1;32m[*] Found a resume file - Press \"R\" to resume or ENTER continue\033[1;m\n")
                #if user wants to resume, read the resume file to store the last word as a variable
                if resume_or_not in ("R","r"):
                        open_resume = open("resume_file.txt")
                        resume_start_word = open_resume.readline()
                        open_resume.close()

def resumefile():
        resume_file = open("resume_file.txt","w")
        resume_file.write(username+"\n")
        resume_file.close()

def search_file():
        global offset
        b = open(usernamefile).read()
        offset = b.find(resume_start_word)

def main():
        global username
        global counter
        counter = 0

        #attempt to open the user specified username file
        try:
                f = open(usernamefile,'r')

        except:
                print "\033[1;31m[-] Could not open file\033[1;m"
                sys.exit(1)

        #check to see if we're resuming. if we are, search the file and calc offset so we can jump to it
        if resume_or_not == "R" or resume_or_not == "r":
                search_file()
                f.seek(offset)

        #main program loop to iterate through our text file and do stuff
        for username in f:
                username = username[:-1]

                #every iteration, call resumefile() to write the last word to the file
                resumefile()

                #in my situation, I had to do things with 2 urls - adjust for your purposes
                url = "ADD YOUR URL"
                url2 = "ADD YOUR URL"

                #since we have custom headers use the build_opener and add headers
                opener = urllib2.build_opener()
                opener.addheaders.append(('Cookie', 'ADD ANY COOKIE INFORMATION HERE'))
                opener.addheaders.append(('Referer', 'PUT THE REFERER IN HERE IF NECESSARY'))
                f = opener.open(url,"PUT ANY REQUIRED POST INFORMATION HERE")

                #access the next url
                f2 = opener.open(url2)

                #capture the response in the_page
                the_page = f2.read()

                #regex match
                answer = re.search(r'PUT SOMETHING IN HERE THAT WILL BE IN THE RESPONSE FROM THE SERVER[a-zA-Z]',the_page,re.M)

                #print our results
                if answer is None:
                        print "\033[1;31m[-] " +username+ "\033[1;m"

                else:
                        print "\033[1;32m[+] "+username+ "\033[1;m"
                        outfile.write(username+"\n")
                        counter+=1

        f.close()
        outfile.close()


if __name__ == '__main__':

        try:

                if len(sys.argv) != 2:
                        print "[+] Usage: ./filename <username_file>"
                        sys.exit(1)

                usernamefile = sys.argv[1]

                append_or_overwrite = "a"
                resume_or_not = "no"

                #check for found_users file
                check_found_users()
                #if it returns nothing, lets just default to append

                #check to see if there is an existing resume file
                check_resume()

                #open the file to write discovered users to and append or overwrite, based on users response
                outfile = open("found_users.txt",append_or_overwrite)

                #start main program
                main()

                #done
                print "\033[1;34m[*] Done - found "+str(counter)+" users.\033[1;m"

        except KeyboardInterrupt:
                print "\033[1;34m\n[*] Program terminated.\033[1;m"