# Extract two-factor authentication (2FA, TFA) secret keys from export QR codes of "Google Authenticator" app
#
# Usage:
# 1. Export the QR codes from "Google Authenticator" app
# 2. Read QR codes with QR code reader
# 3. Save the captured QR codes in a text file. Save each QR code on a new line. (The captured QR codes look like "otpauth-migration://offline?data=...")
# 4. Call this script with the file as input:
# python extract_otp_secret_keys.py -q example_export.txt
#
# Requirement:
# The protobuf package of Google for proto3 is required for running this script.
# pip install protobuf
#
# Optional:
# For printing QR codes, the qrcode module is required
# pip install qrcode
#
# Technical background:
# The export QR code of "Google Authenticator" contains the URL "otpauth-migration://offline?data=...".
# The data parameter is a base64 encoded proto3 message (Google Protocol Buffers).
#
# Command for regeneration of Python code from proto3 message definition file (only necessary in case of changes of the proto3 message definition):
# protoc --python_out=generated_python google_auth.proto
#
# References:
# Proto3 documentation: https://developers.google.com/protocol-buffers/docs/pythontutorial
# Template code: https://github.com/beemdevelopment/Aegis/pull/406
# Author: Scito (https://scito.ch)
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
import argparse
import base64
import fileinput
import sys
from urllib . parse import parse_qs , urlencode , urlparse
import generated_python . google_auth_pb2
arg_parser = argparse . ArgumentParser ( )
arg_parser . add_argument ( ' --verbose ' , ' -v ' , help = ' verbose output ' , action = ' store_true ' )
arg_parser . add_argument ( ' --qr ' , ' -q ' , help = ' print QR codes (otpauth://...) ' , action = ' store_true ' )
arg_parser . add_argument ( ' infile ' , help = ' file or - for stdin (default: -) with " otpauth-migration://... " URLs separated by newlines, lines starting with # are ignored ' )
args = arg_parser . parse_args ( )
verbose = args . verbose
if args . qr :
from qrcode import QRCode
# https://stackoverflow.com/questions/40226049/find-enums-listed-in-python-descriptor-for-protobuf
def get_enum_name_by_number ( parent , field_name ) :
field_value = getattr ( parent , field_name )
return parent . DESCRIPTOR . fields_by_name [ field_name ] . enum_type . values_by_number . get ( field_value ) . name
def convert_secret_from_bytes_to_base32_str ( bytes ) :
return str ( base64 . b32encode ( otp . secret ) , ' utf-8 ' ) . replace ( ' = ' , ' ' )
def print_qr ( data ) :
qr = QRCode ( )
qr . add_data ( data )
qr . print_tty ( )
for line in ( line . strip ( ) for line in fileinput . input ( args . infile ) ) :
if verbose : print ( line )
if line . startswith ( ' # ' ) : continue
parsed_url = urlparse ( line )
params = parse_qs ( parsed_url . query )
data_encoded = params [ ' data ' ] [ 0 ]
data = base64 . b64decode ( data_encoded )
payload = generated_python . google_auth_pb2 . MigrationPayload ( )
payload . ParseFromString ( data )
if verbose : print ( payload )
# pylint: disable=no-member
for otp in payload . otp_parameters :
print ( ' \n Name: {} ' . format ( otp . name ) )
secret = convert_secret_from_bytes_to_base32_str ( otp . secret )
print ( ' Secret: {} ' . format ( secret ) )
if otp . issuer : print ( ' Issuer: {} ' . format ( otp . issuer ) )
print ( ' Type: {} ' . format ( get_enum_name_by_number ( otp , ' type ' ) ) )
url_params = { ' secret ' : secret }
if otp . type == 1 : url_params [ ' counter ' ] = otp . counter
if otp . issuer : url_params [ ' issuer ' ] = otp . issuer
otp_url = ' otpauth:// {} / {} ? ' . format ( ' totp ' if otp . type == 2 else ' hotp ' , otp . name ) + urlencode ( url_params )
if args . qr :
if verbose : print ( otp_url )
print_qr ( otp_url )