[urllib] proxy_bypass_registry - extra error handling required for ProxyOverride, Windows under proxy environment

[chansolkim]

BPO	32465
Nosy	@iritkatriel

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-12-31.14:01:24.115>
labels = ['easy', 'type-bug', 'library', '3.11']
title = '[urllib] proxy_bypass_registry - extra error handling required for ProxyOverride, Windows under proxy environment'
updated_at = <Date 2021-06-18.09:32:03.073>
user = 'https://bugs.python.org/chansolkim'

bugs.python.org fields:

activity = <Date 2021-06-18.09:32:03.073>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-12-31.14:01:24.115>
creator = 'chansol kim'
dependencies = []
files = []
hgrepos = []
issue_num = 32465
keywords = ['easy']
message_count = 2.0
messages = ['309284', '396036']
nosy_count = 2.0
nosy_names = ['chansol kim', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32465'
versions = ['Python 3.11']

Linked PRs

• gh-76646: Fix proxy_bypass_registry trailing semicolon on Windows #138172

[chansolkim]

[Problem]

• String value from registry Proxy override is read and incorrectly decides the current connection requires not to use proxy.

[Setup]

• Using urllib under proxy environment.
• Proxy bypass settings are in place. ProxyOverride string value in registry ends with ;

[Detail]
https://github.com/python/cpython/blob/2.7/Lib/urllib.py
proxy_bypass_registry has an issue

1. It gets registry value from HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings ProxyEnable string value.
2. Splits the string with ;. And as the registry value ends with ; the split list contains a zero length string at the end.
3. Use the split string to re.match. And as there is zero length string at the end it, and the result of re.match('', 'anystring', re.I) is always not None.
4. Afterwards connection is attempted without using the proxy, hence connection cannot be made

From line 1617

        proxyOverride = proxyOverride.split(';')
        # now check if we match one of the registry values.
        for test in proxyOverride:
            if test == '<local>':
                if '.' not in rawHost:
                    return 1
            test = test.replace(".", r"\.")     # mask dots
            test = test.replace("*", r".*")     # change glob sequence
            test = test.replace("?", r".")      # change glob char
            for val in host:
                # print "%s <--> %s" %( test, val )
                if re.match(test, val, re.I):
                    return 1

[iritkatriel]

There are currently no unit tests for proxy_bypass_registry, proxy_bypass, and nothing much for proxy_open. Those should be added as part of this work.

[mblahay]

Should this be tagged with OS-windows?