Find presence of password in pwned SHA1 files

pwned-find.py

#!/usr/bin/env python3

# SHA1 files can be found here: https://haveibeenpwned.com/Passwords

import sys
import os, os.path
from hashlib import sha1
import codecs

HERE=os.path.dirname(os.path.abspath(__file__))

PASSWDFILE = [
	os.path.join(HERE, 'pwned-passwords-1.0.txt'),
	os.path.join(HERE, 'pwned-passwords-update-1.txt'),
	os.path.join(HERE, 'pwned-passwords-update-2.txt')
]

def main():
	hexencode = codecs.getencoder('hex')
	hexdecode = codecs.getdecoder('hex')
	for passwd_string in sys.argv[1:]:
		passwd, _ = codecs.utf_8_encode(passwd_string)
		enc = sha1()
		enc.update(passwd)
		h = enc.digest()
		hh, _ = hexencode(h)
		print('Looking up \"%s\" with SHA1 %s' % (passwd_string, hh))
		found = False
		for passfile in PASSWDFILE:
			fd = os.open(passfile, os.O_RDONLY)
			st = os.stat(fd)
			min, max, hmiddle = 0, st.st_size, ''
			while (max - min) > 42 and not found:
				middle = (min + max) // 2
				middle -= middle % 42
				os.lseek(fd, middle, os.SEEK_SET)
				hmiddle = os.read(fd, 40)
				if len(hmiddle) != 40:
					print('bad read')
					print(hmiddle)
				try:
					hmiddle, n = hexdecode(hmiddle)
					if n != 40:
						print('# n =', n)
						raise Exception('SHA1 must be 20 bytes')
				except Exception:
					print('# Failed to decode')
					print(hmiddle)
					raise
				if h < hmiddle:
					max = middle
				elif h > hmiddle:
					min = middle
				elif h == hmiddle:
					min = max = middle
			if hmiddle == h:
				hh, _ = hexencode(hmiddle)
				print("PWNED !!!!! Hash found in %s !" % (os.path.basename(passfile)))
				found = True
			os.close(fd)
			if found:
				break
		if not found:
			print('Good ! Password not found')

if __name__ == '__main__':
	main()