Created
September 21, 2014 08:38
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Google OTP yubikey
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#!/usr/bin/env python | |
################################################################################ | |
# yubi_goog.py - google authenticator via yubikey | |
# | |
# Use --generate to generate OTPs given a base 32 secret key (from google) | |
# Use --yubi to send a challenge to the yubikey to generate OTPs | |
# Use --convert-secret to convert the google secret into hex | |
# | |
# author: Casey Link <unnamedrambler@gmail.com> | |
# https://github.com/Ramblurr/yubi-goog.git | |
################################################################################ | |
import base64 | |
import re | |
import binascii | |
import time | |
import sys | |
import subprocess | |
import hashlib | |
import hmac | |
import struct | |
ADJACENT_INTERVALS = 3 # generate 3 OTPs | |
TIME_STEP = 30 # default as per TOTP spec | |
# Use sudo when invoking ykchalresp | |
USE_SUDO = True | |
# supporting py2 and py3 sucks | |
IS_PY3 = sys.version_info[0] == 3 | |
def mangle_hash(h): | |
if IS_PY3: | |
offset = h[-1] & 0x0F | |
else: | |
offset = ord(h[-1]) & 0x0F | |
truncated_hash = h[offset:offset+4] | |
code = struct.unpack(">L", truncated_hash)[0] | |
code &= 0x7FFFFFFF; | |
code %= 1000000; | |
return '{0:06d}'.format(code) | |
def totp(secret, tm): | |
bin_key = binascii.unhexlify(secret) | |
h = hmac.new(bin_key, tm, hashlib.sha1).digest() | |
return mangle_hash(h) | |
def generate_challenges(intervals = ADJACENT_INTERVALS): | |
""" | |
intervals: must be odd number | |
generates intervals-number total challenges. used to | |
workaround clock skew. | |
""" | |
challenges = [] | |
t = int(time.time()) | |
for ix in range(0-int(intervals/2), int(intervals/2)+1): | |
tm = (t + TIME_STEP*ix)/TIME_STEP | |
tm = struct.pack('>q', int(tm)) | |
challenges.append(tm) | |
return challenges | |
def decode_secret(secret): | |
""" | |
Decodes the base32 string google provides" to hex | |
""" | |
# remove spaces and uppercase | |
secret = re.sub(r'\s', '', secret).upper() | |
secret = secret.encode('ascii') | |
secret = base64.b32decode(secret) | |
return binascii.hexlify(secret) | |
def get_secret(): | |
""" | |
Read secret from user | |
""" | |
if IS_PY3: | |
google_key = input("Google key: ") | |
else: | |
google_key = raw_input("Google key: ") | |
return decode_secret(google_key) | |
def convert_secret(): | |
secret = get_secret() | |
print(secret.decode()) | |
def generate(): | |
# convert secret to hex | |
secret = get_secret() | |
# now, and 30 seconds ahead and behind | |
for chal in generate_challenges(): | |
print("OTP: %s" %( totp(secret, chal) )) | |
def yubi(): | |
for chal in generate_challenges(): | |
chal = binascii.hexlify(chal) | |
cmd = [] | |
if USE_SUDO: | |
cmd = ['sudo'] | |
cmd.append('ykchalresp') | |
cmd.append('-2x') | |
cmd.append(chal) | |
if hasattr(subprocess, "check_output"): | |
resp = subprocess.check_output(cmd).strip() | |
else: | |
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE) | |
out, err = proc.communicate() | |
if not isinstance(out, basestring): | |
raise ValueError("Command {0} returned {1!r}." | |
.format(" ".join(cmd), out)) | |
resp = out.strip() | |
print("OTP: %s" %(mangle_hash(binascii.unhexlify(resp)))) | |
def error(): | |
print("Valid opts: --generate, --yubi, or --convert-secret") | |
if __name__ == "__main__": | |
if len(sys.argv) <= 1: | |
yubi() | |
sys.exit(1) | |
if sys.argv[1] == "--generate": | |
generate() | |
elif sys.argv[1] == "--yubi": | |
yubi() | |
elif sys.argv[1] == "--convert-secret": | |
convert_secret() | |
else: | |
error() | |
sys.exit(1) |
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