Redirect POST search -> enc GET request

This should fix the annoyance with browsers like Firefox not caching
POST request responses. By redirecting a POST search to be a GET request
instead (with an encrypted query string), the page can be cached and
successfully navigated back to after visiting a result.

app/routes.py

@@ -21,7 +21,7 @@ from app.utils.misc import empty_gif, placeholder_img, get_proxy_host_url, \
     fetch_favicon
 from app.filter import Filter
 from app.utils.misc import read_config_bool, get_client_ip, get_request_url, \
-    check_for_update
+    check_for_update, encrypt_string
 from app.utils.widgets import *
 from app.utils.results import bold_search_terms,\
     add_currency_card, check_currency, get_tabs_content
@@ -34,6 +34,7 @@ from requests import exceptions
 from requests.models import PreparedRequest
 from cryptography.fernet import Fernet, InvalidToken
 from cryptography.exceptions import InvalidSignature
+from werkzeug.datastructures import MultiDict
 
 # Load DDG bang json files only on init
 bang_json = json.load(open(app.config['BANG_FILE'])) or {}
@@ -184,6 +185,7 @@ def before_request_func():
 def after_request_func(resp):
     resp.headers['X-Content-Type-Options'] = 'nosniff'
     resp.headers['X-Frame-Options'] = 'DENY'
+    resp.headers['Cache-Control'] = 'max-age=86400'
 
     if os.getenv('WHOOGLE_CSP', False):
         resp.headers['Content-Security-Policy'] = app.config['CSP']
@@ -301,6 +303,13 @@ def autocomplete():
 @session_required
 @auth_required
 def search():
+    if request.method == 'POST':
+        # Redirect as a GET request with an encrypted query
+        post_data = MultiDict(request.form)
+        post_data['q'] = encrypt_string(g.session_key, post_data['q'])
+        get_req_str = urlparse.urlencode(post_data)
+        return redirect(url_for('.search') + '?' + get_req_str)
+
     search_util = Search(request, g.user_config, g.session_key)
     query = search_util.new_search_query()
 

app/utils/misc.py

@@ -1,5 +1,6 @@
 import base64
 from bs4 import BeautifulSoup as bsoup
+from cryptography.fernet import Fernet
 from flask import Request
 import hashlib
 import io
@@ -126,3 +127,13 @@ def list_to_dict(lst: list) -> dict:
         return {}
     return {lst[i].replace(' ', ''): lst[i+1].replace(' ', '')
             for i in range(0, len(lst), 2)}
+
+
+def encrypt_string(key: bytes, string: str) -> str:
+    cipher_suite = Fernet(key)
+    return cipher_suite.encrypt(string.encode()).decode()
+
+
+def decrypt_string(key: bytes, string: str) -> str:
+    cipher_suite = Fernet(g.session_key)
+    return cipher_suite.decrypt(string.encode()).decode()