From 43a9c9bfa6aa626ec2a22540bea28d2ca77964be Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Fri, 4 Nov 2022 13:47:53 -0400
Subject: [PATCH] Limit the amount of whitespace to search/backtrack.Fixes
 #3659.

---
 setuptools/package_index.py           | 2 +-
 setuptools/tests/test_packageindex.py | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/setuptools/package_index.py b/setuptools/package_index.py
index 270e7f3..e93fcc6 100644
--- a/setuptools/package_index.py
+++ b/setuptools/package_index.py
@@ -197,7 +197,7 @@ def unique_values(func):
     return wrapper
 
 
-REL = re.compile(r"""<([^>]*\srel\s*=\s*['"]?([^'">]+)[^>]*)>""", re.I)
+REL = re.compile(r"""<([^>]*\srel\s{0,10}=\s{0,10}['"]?([^'" >]+)[^>]*)>""", re.I)
 # this line is here to fix emacs' cruddy broken syntax highlighting
 
 
diff --git a/setuptools/tests/test_packageindex.py b/setuptools/tests/test_packageindex.py
index 8e9435e..fc544c0 100644
--- a/setuptools/tests/test_packageindex.py
+++ b/setuptools/tests/test_packageindex.py
@@ -308,3 +308,11 @@ class TestPyPIConfig:
         cred = cfg.creds_by_repository['https://pypi.org']
         assert cred.username == 'jaraco'
         assert cred.password == 'pity%'
+
+
+@pytest.mark.timeout(1)
+def test_REL_DoS():
+    """
+    REL should not hang on a contrived attack string.
+    """
+    setuptools.package_index.REL.search('< rel=' + ' ' * 2**12)
-- 
2.27.0

