Resolve issue 128 - yubikey auth flow broken by google page update

aws_google_auth/google.py

@@ -7,6 +7,7 @@
 import json
 import logging
 import os
+import re
 import sys
 
 import requests
@@ -132,6 +133,42 @@ def parse_error_message(sess):
         else:
             return error.text
 
+    @staticmethod
+    def find_key_handle(input, challengeTxt):
+        typeOfInput = type(input)
+        if typeOfInput == dict:  # parse down a dict
+            for item in input:
+                rvalue = Google.find_key_handle(input[item], challengeTxt)
+                if rvalue is not None:
+                    return rvalue
+
+        elif typeOfInput == list:  # looks like we've hit an array - iterate it
+            array = list(filter(None, input))  # remove any None type objects from the array
+            for item in array:
+                typeValue = type(item)
+                if typeValue == list:  # another array - recursive call
+                    return Google.find_key_handle(item, challengeTxt)
+                elif typeValue == int or typeValue == bool:  # ints bools etc we don't care
+                    continue
+                else:  # we went a string or unicode here (python 3.x lost unicode global)
+                    try:  # keyHandle string will be base64 encoded -
+                        # if its not an exception is thrown and we continue as its not the string we're after
+                        base64UrlEncoded = base64.urlsafe_b64encode(base64.b64decode(item))
+                        if base64UrlEncoded != challengeTxt:  # make sure its not the challengeTxt - if it not return it
+                            return base64UrlEncoded
+                    except:
+                        pass
+
+    @staticmethod
+    def find_app_id(inputString):
+        try:
+            searchResult = re.search('"appid":"[a-z://.-_]+"', inputString).group()
+            searchObject = json.loads('{' + searchResult + '}')
+            return str(searchObject['appid'])
+        except:
+            logging.exception('Was unable to find appid value in googles SAML page')
+            sys.exit(1)
+
     def do_login(self):
         self.session = requests.Session()
         self.session.headers['User-Agent'] = "AWS Sign-in/{} (Cevo aws-google-auth)".format(self.version)
@@ -357,26 +394,35 @@ def handle_captcha(self, sess, payload):
     def handle_sk(self, sess):
         response_page = BeautifulSoup(sess.text, 'html.parser')
         challenge_url = sess.url.split("?")[0]
-
         challenges_txt = response_page.find('input', {
             'name': "id-challenge"
         }).get('value')
-        challenges = json.loads(challenges_txt)
 
         facet_url = urllib_parse.urlparse(challenge_url)
         facet = facet_url.scheme + "://" + facet_url.netloc
-        app_id = challenges["appId"]
+
+        keyHandleJSField = response_page.find('div', {'jsname': 'C0oDBd'}).get('data-challenge-ui')
+        startJSONPosition = keyHandleJSField.find('{')
+        endJSONPosition = keyHandleJSField.rfind('}')
+        keyHandleJsonPayload = json.loads(keyHandleJSField[startJSONPosition:endJSONPosition + 1])
+
+        keyHandle = self.find_key_handle(keyHandleJsonPayload, base64.urlsafe_b64encode(base64.b64decode(challenges_txt)))
+        appId = self.find_app_id(str(keyHandleJsonPayload))
+
+        # txt sent for signing needs to be base64 url encode
+        # we also have to remove any base64 padding because including including it will prevent google accepting the auth response
+        challenges_txt_encode_pad_removed = base64.urlsafe_b64encode(base64.b64decode(challenges_txt)).strip('='.encode())
+
         u2f_challenges = []
-        for c in challenges["challenges"]:
-            c["appId"] = app_id
-            u2f_challenges.append(c)
+        u2f_challenges.append({'version': 'U2F_V2', 'challenge': challenges_txt_encode_pad_removed.decode(), 'appId': appId, 'keyHandle': keyHandle.decode()})
 
         # Prompt the user up to attempts_remaining times to insert their U2F device.
         attempts_remaining = 5
         auth_response = None
         while True:
             try:
-                auth_response = json.dumps(u2f.u2f_auth(u2f_challenges, facet))
+                auth_response_dict = u2f.u2f_auth(u2f_challenges, facet)
+                auth_response = json.dumps(auth_response_dict)
                 break
             except RuntimeWarning:
                 logging.error("No U2F device found. %d attempts remaining",
@@ -403,8 +449,7 @@ def handle_sk(self, sess):
             response_page.find('input', {
                 'name': 'challengeType'
             }).get('value'),
-            'continue':
-            response_page.find('input', {
+            'continue': response_page.find('input', {
                 'name': 'continue'
             }).get('value'),
             'scc':
@@ -419,10 +464,7 @@ def handle_sk(self, sess):
             response_page.find('input', {
                 'name': 'checkedDomains'
             }).get('value'),
-            'pstMsg':
-            response_page.find('input', {
-                'name': 'pstMsg'
-            }).get('value'),
+            'pstMsg': '1',
             'TL':
             response_page.find('input', {
                 'name': 'TL'