Support passing the Auth token as a url param.

This is required to support ebook downloads which the Kobo device emits
without any auth headers.

* Also some other small bug fixes discovered during device testing.

cps/helper.py

@@ -445,7 +445,7 @@ def get_book_cover_with_uuid(book_uuid,
 
 def get_book_cover_internal(book,
                    use_generic_cover_on_failure):
-    if book.has_cover:
+    if book and book.has_cover:
         if config.config_use_google_drive:
             try:
                 if not gd.is_gdrive_ready():

cps/kobo.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
+import base64
 import copy
 import uuid
 import os
@@ -25,8 +26,6 @@ kobo_auth.disable_failed_auth_redirect_for_blueprint(kobo)
 
 log = logger.create()
 
-import base64
-
 
 def b64encode(data):
     return base64.b64encode(data)
@@ -92,10 +91,12 @@ class SyncToken:
         if "." in sync_token_header:
             return SyncToken(raw_kobo_store_token=sync_token_header)
 
-        sync_token_json = json.loads(
-            base64.b64decode(sync_token_header + "=" * (-len(sync_token_header) % 4))
-        )
         try:
+            sync_token_json = json.loads(
+                base64.b64decode(
+                    sync_token_header + "=" * (-len(sync_token_header) % 4)
+                )
+            )
             validate(sync_token_json, SyncToken.token_schema)
             if sync_token_json["version"] < SyncToken.MIN_VERSION:
                 raise ValueError
@@ -217,8 +218,10 @@ def get_metadata__v1(book_uuid):
 
 
 def get_download_url_for_book(book):
-    return "{url_base}/download/{book_id}/kepub".format(
-        url_base=config.config_server_url, book_id=book.id
+    return "{url_base}/download/{book_id}/kepub?{auth_token_param}".format(
+        url_base=config.config_server_url,
+        book_id=book.id,
+        auth_token_param=kobo_auth.get_auth_url_param(request),
     )
 
 

cps/kobo_auth.py

@@ -50,6 +50,8 @@ from werkzeug.security import check_password_hash
 from . import logger, ub, lm
 
 USER_KEY_HEADER = "x-kobo-userkey"
+USER_KEY_URL_PARAM = "kobo_userkey"
+
 log = logger.create()
 
 
@@ -59,7 +61,7 @@ def disable_failed_auth_redirect_for_blueprint(bp):
 
 @lm.request_loader
 def load_user_from_kobo_request(request):
-    user_key = request.headers.get(USER_KEY_HEADER)
+    user_key = get_auth_token_from_request(request)
     if user_key:
         for user in (
             ub.session.query(ub.User).filter(ub.User.kobo_user_key_hash != "").all()
@@ -68,3 +70,20 @@ def load_user_from_kobo_request(request):
                 return user
     log.info("Received Kobo request without a recognizable UserKey.")
     return None
+
+
+def get_auth_token_from_request(request):
+    user_key = request.headers.get(USER_KEY_HEADER)
+    if not user_key:
+        user_key = request.args.get(USER_KEY_URL_PARAM)
+    return user_key
+
+
+def get_auth_url_param(request):
+    # Some of the API requests emitted by the Kobo device don't set any headers. To
+    # support those calls, authorization on those endpoints can only rely on URL params.
+    # Since the raw UserKey in already leaked in headers, it is probably not *that* much
+    # worse to also leak it over url params.
+    # Ideally however, we should be generating short-lived tokens that grant limited
+    # access instead..
+    return USER_KEY_URL_PARAM + "=" + get_auth_token_from_request(request)