proxy bypass on Windows without DNS lookups

requests/compat.py

@@ -37,7 +37,9 @@ except (ImportError, SyntaxError):
 # ---------
 
 if is_py2:
-    from urllib import quote, unquote, quote_plus, unquote_plus, urlencode, getproxies, proxy_bypass
+    from urllib import (
+        quote, unquote, quote_plus, unquote_plus, urlencode, getproxies,
+        proxy_bypass, proxy_bypass_environment, getproxies_environment)
     from urlparse import urlparse, urlunparse, urljoin, urlsplit, urldefrag
     from urllib2 import parse_http_list
     import cookielib
@@ -54,7 +56,7 @@ if is_py2:
 
 elif is_py3:
     from urllib.parse import urlparse, urlunparse, urljoin, urlsplit, urlencode, quote, unquote, quote_plus, unquote_plus, urldefrag
-    from urllib.request import parse_http_list, getproxies, proxy_bypass
+    from urllib.request import parse_http_list, getproxies, proxy_bypass, proxy_bypass_environment, getproxies_environment
     from http import cookiejar as cookielib
     from http.cookies import Morsel
     from io import StringIO

requests/utils.py

@@ -14,6 +14,7 @@ import collections
 import contextlib
 import io
 import os
+import platform
 import re
 import socket
 import struct
@@ -26,7 +27,8 @@ from ._internal_utils import to_native_string
 from .compat import parse_http_list as _parse_list_header
 from .compat import (
     quote, urlparse, bytes, str, OrderedDict, unquote, getproxies,
-    proxy_bypass, urlunparse, basestring, integer_types)
+    proxy_bypass, urlunparse, basestring, integer_types, is_py3,
+    proxy_bypass_environment, getproxies_environment)
 from .cookies import cookiejar_from_dict
 from .structures import CaseInsensitiveDict
 from .exceptions import (
@@ -37,6 +39,54 @@ NETRC_FILES = ('.netrc', '_netrc')
 DEFAULT_CA_BUNDLE_PATH = certs.where()
 
 
+if platform.system() == 'Windows':
+    # provide a proxy_bypass version on Windows without DNS lookups
+
+    def proxy_bypass_registry(host):
+        if is_py3:
+            import winreg
+        else:
+            import _winreg as winreg
+        try:
+            internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
+                r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
+            proxyEnable = winreg.QueryValueEx(internetSettings,
+                                              'ProxyEnable')[0]
+            proxyOverride = winreg.QueryValueEx(internetSettings,
+                                                'ProxyOverride')[0]
+        except OSError:
+            return False
+        if not proxyEnable or not proxyOverride:
+            return False
+
+        # make a check value list from the registry entry: replace the
+        # '<local>' string by the localhost entry and the corresponding
+        # canonical entry.
+        proxyOverride = proxyOverride.split(';')
+        # now check if we match one of the registry values.
+        for test in proxyOverride:
+            if test == '<local>':
+                if '.' not in host:
+                    return True
+            test = test.replace(".", r"\.")     # mask dots
+            test = test.replace("*", r".*")     # change glob sequence
+            test = test.replace("?", r".")      # change glob char
+            if re.match(test, host, re.I):
+                return True
+        return False
+
+    def proxy_bypass(host):  # noqa
+        """Return True, if the host should be bypassed.
+
+        Checks proxy settings gathered from the environment, if specified,
+        or the registry.
+        """
+        if getproxies_environment():
+            return proxy_bypass_environment(host)
+        else:
+            return proxy_bypass_registry(host)
+
+
 def dict_to_sequence(d):
     """Returns an internal sequence dictionary update."""
 

tests/test_utils.py

@@ -604,20 +604,25 @@ def test_should_bypass_proxies_no_proxy(
 
 @pytest.mark.skipif(os.name != 'nt', reason='Test only on Windows')
 @pytest.mark.parametrize(
-    'url, expected', (
-            ('http://192.168.0.1:5000/', True),
-            ('http://192.168.0.1/', True),
-            ('http://172.16.1.1/', True),
-            ('http://172.16.1.1:5000/', True),
-            ('http://localhost.localdomain:5000/v1.0/', True),
-            ('http://172.16.1.22/', False),
-            ('http://172.16.1.22:5000/', False),
-            ('http://google.com:5000/v1.0/', False),
+    'url, expected, override', (
+            ('http://192.168.0.1:5000/', True, None),
+            ('http://192.168.0.1/', True, None),
+            ('http://172.16.1.1/', True, None),
+            ('http://172.16.1.1:5000/', True, None),
+            ('http://localhost.localdomain:5000/v1.0/', True, None),
+            ('http://172.16.1.22/', False, None),
+            ('http://172.16.1.22:5000/', False, None),
+            ('http://google.com:5000/v1.0/', False, None),
+            ('http://mylocalhostname:5000/v1.0/', True, '<local>'),
+            ('http://192.168.0.1/', False, ''),
     ))
-def test_should_bypass_proxies_win_registry(url, expected, monkeypatch):
+def test_should_bypass_proxies_win_registry(url, expected, override,
+                                            monkeypatch):
     """Tests for function should_bypass_proxies to check if proxy
     can be bypassed or not with Windows registry settings
     """
+    if override is None:
+        override = '192.168.*;127.0.0.1;localhost.localdomain;172.16.1.1'
     if compat.is_py3:
         import winreg
     else:
@@ -637,7 +642,7 @@ def test_should_bypass_proxies_win_registry(url, expected, monkeypatch):
             if value_name == 'ProxyEnable':
                 return [1]
             elif value_name == 'ProxyOverride':
-                return ['192.168.*;127.0.0.1;localhost.localdomain;172.16.1.1']
+                return [override]
 
     monkeypatch.setenv('http_proxy', '')
     monkeypatch.setenv('https_proxy', '')