bpo-41471: Ignore invalid prefix lengths in system proxy settings on macOS (GH-22762) (GH-22774)

(cherry picked from commit 93a1cca) Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com>

Author: miss-islington

Lib/test/test_urllib2.py

@@ -1444,6 +1444,18 @@ def test_osx_proxy_bypass(self):
  bypass = {'exclude_simple': True, 'exceptions': []}
  self.assertTrue(_proxy_bypass_macosx_sysconf('test', bypass))
 
+ # Check that invalid prefix lengths are ignored
+ bypass = {
+ 'exclude_simple': False,
+ 'exceptions': [ '10.0.0.0/40', '172.19.10.0/24' ]
+ }
+ host = '172.19.10.5'
+ self.assertTrue(_proxy_bypass_macosx_sysconf(host, bypass),
+ 'expected bypass of %s to be True' % host)
+ host = '10.0.1.5'
+ self.assertFalse(_proxy_bypass_macosx_sysconf(host, bypass),
+ 'expected bypass of %s to be False' % host)
+
  def check_basic_auth(self, headers, realm):
  with self.subTest(realm=realm, headers=headers):
  opener = OpenerDirector()

Lib/urllib/request.py

@@ -2604,6 +2604,11 @@ def ip2num(ipAddr):
  mask = 8 * (m.group(1).count('.') + 1)
  else:
  mask = int(mask[1:])
+
+ if mask < 0 or mask > 32:
+ # System libraries ignore invalid prefix lengths
+ continue
+
  mask = 32 - mask
 
  if (hostIP >> mask) == (base >> mask):

Misc/NEWS.d/next/macOS/2020-10-19-12-25-19.bpo-41471.gwA7un.rst

@@ -0,0 +1 @@
+Ignore invalid prefix lengths in system proxy excludes.