From a22866244736345239909eaca7be2eb8da791997 Mon Sep 17 00:00:00 2001
From: Viktor Chuchurski <viktor@doyensec.com>
Date: Thu, 25 Jul 2024 19:34:35 +0200
Subject: [PATCH 1/6] - added output encoding in redirect HTML

---
 src/twisted/web/_template_util.py          |  2 +-
 src/twisted/web/newsfragments/12263.bugfix |  1 +
 src/twisted/web/newsfragments/9839.bugfix  |  1 +
 src/twisted/web/test/test_util.py          | 39 +++++++++++++++++++++-
 4 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 src/twisted/web/newsfragments/12263.bugfix
 create mode 100644 src/twisted/web/newsfragments/9839.bugfix

diff --git a/src/twisted/web/_template_util.py b/src/twisted/web/_template_util.py
index 38ebbed..c6f7e9d 100644
--- a/src/twisted/web/_template_util.py
+++ b/src/twisted/web/_template_util.py
@@ -92,7 +92,7 @@ def redirectTo(URL: bytes, request: IRequest) -> bytes:
     </body>
 </html>
 """ % {
-        b"url": URL
+        b"url": escape(URL.decode("utf-8")).encode("utf-8")
     }
     return content
 
diff --git a/src/twisted/web/newsfragments/12263.bugfix b/src/twisted/web/newsfragments/12263.bugfix
new file mode 100644
index 0000000..b3982ca
--- /dev/null
+++ b/src/twisted/web/newsfragments/12263.bugfix
@@ -0,0 +1 @@
+twisted.web.util.redirectTo now HTML-escapes the provided URL in the fallback response body it returns (GHSA-cf56-g6w6-pqq2). The issue is being tracked with CVE-2024-41810.
\ No newline at end of file
diff --git a/src/twisted/web/newsfragments/9839.bugfix b/src/twisted/web/newsfragments/9839.bugfix
new file mode 100644
index 0000000..1e2e7f7
--- /dev/null
+++ b/src/twisted/web/newsfragments/9839.bugfix
@@ -0,0 +1 @@
+twisted.web.util.redirectTo now HTML-escapes the provided URL in the fallback response body it returns (GHSA-cf56-g6w6-pqq2, CVE-2024-41810).
diff --git a/src/twisted/web/test/test_util.py b/src/twisted/web/test/test_util.py
index 996b0d0..87282ce 100644
--- a/src/twisted/web/test/test_util.py
+++ b/src/twisted/web/test/test_util.py
@@ -5,7 +5,6 @@
 Tests for L{twisted.web.util}.
 """
 
-
 import gc
 
 from twisted.internet import defer
@@ -64,6 +63,44 @@ class RedirectToTests(TestCase):
         targetURL = "http://target.example.com/4321"
         self.assertRaises(TypeError, redirectTo, targetURL, request)
 
+    def test_legitimateRedirect(self):
+        """
+        Legitimate URLs are fully interpolated in the `redirectTo` response body without transformation
+        """
+        request = DummyRequest([b""])
+        html = redirectTo(b"https://twisted.org/", request)
+        expected = b"""
+<html>
+    <head>
+        <meta http-equiv=\"refresh\" content=\"0;URL=https://twisted.org/\">
+    </head>
+    <body bgcolor=\"#FFFFFF\" text=\"#000000\">
+    <a href=\"https://twisted.org/\">click here</a>
+    </body>
+</html>
+"""
+        self.assertEqual(html, expected)
+
+    def test_maliciousRedirect(self):
+        """
+        Malicious URLs are HTML-escaped before interpolating them in the `redirectTo` response body
+        """
+        request = DummyRequest([b""])
+        html = redirectTo(
+            b'https://twisted.org/"><script>alert(document.location)</script>', request
+        )
+        expected = b"""
+<html>
+    <head>
+        <meta http-equiv=\"refresh\" content=\"0;URL=https://twisted.org/&quot;&gt;&lt;script&gt;alert(document.location)&lt;/script&gt;\">
+    </head>
+    <body bgcolor=\"#FFFFFF\" text=\"#000000\">
+    <a href=\"https://twisted.org/&quot;&gt;&lt;script&gt;alert(document.location)&lt;/script&gt;\">click here</a>
+    </body>
+</html>
+"""
+        self.assertEqual(html, expected)
+
 
 class ParentRedirectTests(SynchronousTestCase):
     """
-- 
2.41.0

