From 26bfc68c979dc1096e68b175fd3c130af2a269c1 Mon Sep 17 00:00:00 2001
From: Benjamin Dauvergne <bdauvergne@entrouvert.com>
Date: Tue, 6 Oct 2020 12:40:08 +0200
Subject: [PATCH 1/2] misc: check null characters in query-string and form data
 (#46625)

---
 src/authentic2/middleware.py | 21 +++++++++++++++++++++
 src/authentic2/settings.py   |  1 +
 tests/test_idp_saml2.py      |  5 +++++
 tests/test_login.py          |  8 ++++++++
 4 files changed, 35 insertions(+)

diff --git a/src/authentic2/middleware.py b/src/authentic2/middleware.py
index f3b32aa0..c9b8b3b2 100644
--- a/src/authentic2/middleware.py
+++ b/src/authentic2/middleware.py
@@ -30,6 +30,7 @@ from django.utils.encoding import force_text
 from django.utils.translation import ugettext as _
 from django.utils.six.moves.urllib import parse as urlparse
 from django.shortcuts import render
+from django import http
 
 from . import app_settings, utils, plugins
 from .utils.service import get_service_from_request
@@ -215,3 +216,23 @@ class SaveServiceInSessionMiddleware:
             request.session['service_pk'] = service.pk
 
         return self.get_response(request)
+
+
+def null_character_middleware(get_response):
+    def middleware(request):
+        def check_query_dict(qd):
+            for key in qd:
+                for value in qd.getlist(key):
+                    if '\0' in value:
+                        return False
+            return True
+
+        if not check_query_dict(request.GET):
+            return http.HttpResponseBadRequest('null character in query string')
+
+        if request.content_type == 'application/x-www-form-urlencoded':
+            if not check_query_dict(request.POST):
+                return http.HttpResponseBadRequest('null character in form data')
+
+        return get_response(request)
+    return middleware
diff --git a/src/authentic2/settings.py b/src/authentic2/settings.py
index c0ea6d9e..12bcf0e8 100644
--- a/src/authentic2/settings.py
+++ b/src/authentic2/settings.py
@@ -88,6 +88,7 @@ TEMPLATES = [
 
 
 MIDDLEWARE = (
+    'authentic2.middleware.null_character_middleware',
     'authentic2.middleware.StoreRequestMiddleware',
     'authentic2.middleware.RequestIdMiddleware',
     'authentic2.middleware.ServiceAccessControlMiddleware',
diff --git a/tests/test_idp_saml2.py b/tests/test_idp_saml2.py
index 182bc38d..209a434a 100644
--- a/tests/test_idp_saml2.py
+++ b/tests/test_idp_saml2.py
@@ -968,3 +968,8 @@ uGnhj8v6XwvbjKZrL9kA+xf8ziazZfvvw/VGTm+IVFYB7d1x457jY5zjjXJvNyso
 owIDAQAB
 -----END PUBLIC KEY-----'''
     response = app.get('/idp/saml2/metadata')
+
+
+def test_null_character_nonce(app, db):
+    response = app.get('/idp/saml2/continue/', params={'nonce': '\0'}, status=400)
+    assert response.text == 'null character in query string'
diff --git a/tests/test_login.py b/tests/test_login.py
index 7302df19..ec2f6c2e 100644
--- a/tests/test_login.py
+++ b/tests/test_login.py
@@ -304,3 +304,11 @@ def test_login_opened_session_cookie(db, app, settings, simple_user):
     for cookie in app.cookiejar:
         if cookie.name == 'A2_OPENED_SESSION':
             assert cookie.secure is True
+
+
+def test_null_characters(app, db):
+    response = app.get('/login/')
+    response.form.set('username', 'xx\0xx')
+    response.form.set('password', 'whatever')
+    response = response.form.submit(name='login-password-submit', status=400)
+    assert response.text == 'null character in form data'
-- 
2.28.0