Hotfix: Enforce https in heroku opensearch template

Heroku instances were using the base http url when formatting the
opensearch.xml template. This adds a new routing utility, "needs_https",
which can be used for determining if the url in question needs
upgrading.

app/routes.py

@@ -66,11 +66,7 @@ def before_request_func():
         app.user_elements.update({session['uuid']: 0})
 
     # Handle https upgrade
-    https_only = os.getenv('HTTPS_ONLY', False)
-    is_heroku = request.url.endswith('.herokuapp.com')
-    is_http = request.url.startswith('http://')
-
-    if (is_heroku and is_http) or (https_only and is_http):
+    if needs_https(request.url):
         return redirect(
             request.url.replace('http://', 'https://', 1),
             code=308)
@@ -80,7 +76,7 @@ def before_request_func():
     if not g.user_config.url:
         g.user_config.url = request.url_root.replace(
             'http://',
-            'https://') if https_only else request.url_root
+            'https://') if os.getenv('HTTPS_ONLY', False) else request.url_root
 
     g.user_request = Request(
         request.headers.get('User-Agent'),
@@ -146,6 +142,10 @@ def opensearch():
     if opensearch_url.endswith('/'):
         opensearch_url = opensearch_url[:-1]
 
+    # Enforce https for opensearch template
+    if needs_https(opensearch_url):
+        opensearch_url = opensearch_url.replace('http://', 'https://', 1)
+
     get_only = g.user_config.get_only or 'Chrome' in request.headers.get(
         'User-Agent')
 

app/utils/routing_utils.py

@@ -5,10 +5,19 @@ from bs4 import BeautifulSoup as bsoup
 from cryptography.fernet import Fernet, InvalidToken
 from flask import g
 from typing import Any, Tuple
+import os
 
 TOR_BANNER = '<hr><h1 style="text-align: center">You are using Tor</h1><hr>'
 
 
+def needs_https(url: str) -> bool:
+    https_only = os.getenv('HTTPS_ONLY', False)
+    is_heroku = url.endswith('.herokuapp.com')
+    is_http = url.startswith('http://')
+
+    return (is_heroku and is_http) or (https_only and is_http)
+
+
 class RoutingUtils:
     def __init__(self, request, config, session, cookies_disabled=False):
         method = request.method