warrant should make sure the time data is sent in English

[alexsavio]

In https://github.com/capless/warrant-lite/blob/master/warrant_lite/__init__.py#L193, if the LOCALE is not set to English, this would fail.

[piotrkubisa]

It would be nice to see a patch for this issue. Let's say you are including warrant-lite in GUI application made in PyGTK or PyQT, in such case locale will be get overriden by system-wide locale.

Quick fix would be a class which inherits the WarrantLite, i.e.:

import base64
import datetime
import hashlib
import hmac
import locale
import re

from warrant_lite import WarrantLite, hex_to_long


class WarrantModified(WarrantLite):
    def process_challenge(self, challenge_parameters):
        user_id_for_srp = challenge_parameters['USER_ID_FOR_SRP']
        salt_hex = challenge_parameters['SALT']
        srp_b_hex = challenge_parameters['SRP_B']
        secret_block_b64 = challenge_parameters['SECRET_BLOCK']
        # re strips leading zero from a day number (required by AWS Cognito)
        # NOTE: Specify en_US locale
        locale.setlocale(locale.LC_ALL, ('en_US', 'UTF-8'))
        timestamp = re.sub(r" 0(\d) ", r" \1 ",
                           datetime.datetime.utcnow().strftime("%a %b %d %H:%M:%S UTC %Y"))
        # NOTE: Return to default locale
        locale.setlocale(locale.LC_ALL, locale.getdefaultlocale())
        hkdf = self.get_password_authentication_key(user_id_for_srp,
                                                    self.password, hex_to_long(srp_b_hex), salt_hex)
        secret_block_bytes = base64.standard_b64decode(secret_block_b64)
        msg = bytearray(self.pool_id.split('_')[1], 'utf-8') + bytearray(user_id_for_srp, 'utf-8') + \
            bytearray(secret_block_bytes) + bytearray(timestamp, 'utf-8')
        hmac_obj = hmac.new(hkdf, msg, digestmod=hashlib.sha256)
        signature_string = base64.standard_b64encode(hmac_obj.digest())
        response = {'TIMESTAMP': timestamp,
                    'USERNAME': user_id_for_srp,
                    'PASSWORD_CLAIM_SECRET_BLOCK': secret_block_b64,
                    'PASSWORD_CLAIM_SIGNATURE': signature_string.decode('utf-8')}
        if self.client_secret is not None:
            response.update({
                "SECRET_HASH":
                self.get_secret_hash(self.username, self.client_id, self.client_secret)})
        return response

[alexsavio]

I've just created #6 with a possible fix