Idris Kalp
214 lines
8.8 KiB
Diff
214 lines
8.8 KiB
Diff
From 2273e65e11dd0234f2f51ebaef61fc6e848d4059 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
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Date: Thu, 10 Sep 2020 13:35:39 +0200
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Subject: [PATCH 02/24] bpo-39503: CVE-2020-8492: Fix AbstractBasicAuthHandler
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(GH-18284) (GH-19304)
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The AbstractBasicAuthHandler class of the urllib.request module uses
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an inefficient regular expression which can be exploited by an
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attacker to cause a denial of service. Fix the regex to prevent the
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catastrophic backtracking. Vulnerability reported by Ben Caller
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and Matt Schwager.
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AbstractBasicAuthHandler of urllib.request now parses all
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WWW-Authenticate HTTP headers and accepts multiple challenges per
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header: use the realm of the first Basic challenge.
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Co-Authored-By: Serhiy Storchaka <storchaka@gmail.com>
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(cherry picked from commit 0b297d4ff1c0e4480ad33acae793fbaf4bf015b4)
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[rebased for py2.7]
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---
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Lib/test/test_urllib2.py | 81 ++++++++++++++++++++++++++--------------
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Lib/urllib2.py | 60 +++++++++++++++++++++++------
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2 files changed, 101 insertions(+), 40 deletions(-)
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diff --git a/Lib/test/test_urllib2.py b/Lib/test/test_urllib2.py
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index 20a0f58143..0adbb13c43 100644
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--- a/Lib/test/test_urllib2.py
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+++ b/Lib/test/test_urllib2.py
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@@ -1128,42 +1128,67 @@ class HandlerTests(unittest.TestCase):
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self.assertEqual(req.get_host(), "proxy.example.com:3128")
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self.assertEqual(req.get_header("Proxy-authorization"),"FooBar")
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- def test_basic_auth(self, quote_char='"'):
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+ def check_basic_auth(self, headers, realm):
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opener = OpenerDirector()
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password_manager = MockPasswordManager()
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auth_handler = urllib2.HTTPBasicAuthHandler(password_manager)
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- realm = "ACME Widget Store"
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- http_handler = MockHTTPHandler(
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- 401, 'WWW-Authenticate: Basic realm=%s%s%s\r\n\r\n' %
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- (quote_char, realm, quote_char) )
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+ body = '\r\n'.join(headers) + '\r\n\r\n'
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+ http_handler = MockHTTPHandler(401, body)
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opener.add_handler(auth_handler)
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opener.add_handler(http_handler)
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self._test_basic_auth(opener, auth_handler, "Authorization",
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realm, http_handler, password_manager,
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"http://acme.example.com/protected",
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- "http://acme.example.com/protected"
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- )
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-
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- def test_basic_auth_with_single_quoted_realm(self):
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- self.test_basic_auth(quote_char="'")
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-
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- def test_basic_auth_with_unquoted_realm(self):
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- opener = OpenerDirector()
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- password_manager = MockPasswordManager()
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- auth_handler = urllib2.HTTPBasicAuthHandler(password_manager)
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- realm = "ACME Widget Store"
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- http_handler = MockHTTPHandler(
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- 401, 'WWW-Authenticate: Basic realm=%s\r\n\r\n' % realm)
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- opener.add_handler(auth_handler)
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- opener.add_handler(http_handler)
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- msg = "Basic Auth Realm was unquoted"
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- with test_support.check_warnings((msg, UserWarning)):
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- self._test_basic_auth(opener, auth_handler, "Authorization",
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- realm, http_handler, password_manager,
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- "http://acme.example.com/protected",
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- "http://acme.example.com/protected"
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- )
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-
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+ "http://acme.example.com/protected")
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+
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+ def test_basic_auth(self):
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+ realm = "realm2@example.com"
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+ realm2 = "realm2@example.com"
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+ basic = 'Basic realm="{realm}"'.format(realm=realm)
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+ basic2 = 'Basic realm="{realm2}"'.format(realm2=realm2)
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+ other_no_realm = 'Otherscheme xxx'
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+ digest = ('Digest realm="{realm2}", '
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+ 'qop="auth, auth-int", '
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+ 'nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093", '
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+ 'opaque="5ccc069c403ebaf9f0171e9517f40e41"'
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+ .format(realm2=realm2))
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+ for realm_str in (
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+ # test "quote" and 'quote'
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+ 'Basic realm="{realm}"'.format(realm=realm),
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+ "Basic realm='{realm}'".format(realm=realm),
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+
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+ # charset is ignored
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+ 'Basic realm="{realm}", charset="UTF-8"'.format(realm=realm),
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+
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+ # Multiple challenges per header
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+ ', '.join((basic, basic2)),
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+ ', '.join((basic, other_no_realm)),
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+ ', '.join((other_no_realm, basic)),
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+ ', '.join((basic, digest)),
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+ ', '.join((digest, basic)),
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+ ):
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+ headers = ['WWW-Authenticate: {realm_str}'
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+ .format(realm_str=realm_str)]
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+ self.check_basic_auth(headers, realm)
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+
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+ # no quote: expect a warning
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+ with test_support.check_warnings(("Basic Auth Realm was unquoted",
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+ UserWarning)):
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+ headers = ['WWW-Authenticate: Basic realm={realm}'
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+ .format(realm=realm)]
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+ self.check_basic_auth(headers, realm)
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+
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+ # Multiple headers: one challenge per header.
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+ # Use the first Basic realm.
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+ for challenges in (
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+ [basic, basic2],
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+ [basic, digest],
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+ [digest, basic],
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+ ):
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+ headers = ['WWW-Authenticate: {challenge}'
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+ .format(challenge=challenge)
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+ for challenge in challenges]
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+ self.check_basic_auth(headers, realm)
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def test_proxy_basic_auth(self):
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opener = OpenerDirector()
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diff --git a/Lib/urllib2.py b/Lib/urllib2.py
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index 8b634ada37..b2d1fad6f2 100644
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--- a/Lib/urllib2.py
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+++ b/Lib/urllib2.py
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@@ -856,8 +856,15 @@ class AbstractBasicAuthHandler:
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# allow for double- and single-quoted realm values
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# (single quotes are a violation of the RFC, but appear in the wild)
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- rx = re.compile('(?:.*,)*[ \t]*([^ \t]+)[ \t]+'
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- 'realm=(["\']?)([^"\']*)\\2', re.I)
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+ rx = re.compile('(?:^|,)' # start of the string or ','
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+ '[ \t]*' # optional whitespaces
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+ '([^ \t]+)' # scheme like "Basic"
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+ '[ \t]+' # mandatory whitespaces
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+ # realm=xxx
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+ # realm='xxx'
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+ # realm="xxx"
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+ 'realm=(["\']?)([^"\']*)\\2',
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+ re.I)
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# XXX could pre-emptively send auth info already accepted (RFC 2617,
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# end of section 2, and section 1.2 immediately after "credentials"
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@@ -869,23 +876,52 @@ class AbstractBasicAuthHandler:
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self.passwd = password_mgr
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self.add_password = self.passwd.add_password
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+ def _parse_realm(self, header):
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+ # parse WWW-Authenticate header: accept multiple challenges per header
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+ found_challenge = False
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+ for mo in AbstractBasicAuthHandler.rx.finditer(header):
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+ scheme, quote, realm = mo.groups()
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+ if quote not in ['"', "'"]:
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+ warnings.warn("Basic Auth Realm was unquoted",
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+ UserWarning, 3)
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+
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+ yield (scheme, realm)
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+
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+ found_challenge = True
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+
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+ if not found_challenge:
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+ if header:
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+ scheme = header.split()[0]
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+ else:
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+ scheme = ''
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+ yield (scheme, None)
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def http_error_auth_reqed(self, authreq, host, req, headers):
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# host may be an authority (without userinfo) or a URL with an
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# authority
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- # XXX could be multiple headers
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- authreq = headers.get(authreq, None)
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+ headers = headers.getheaders(authreq)
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+ if not headers:
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+ # no header found
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+ return
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- if authreq:
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- mo = AbstractBasicAuthHandler.rx.search(authreq)
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- if mo:
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- scheme, quote, realm = mo.groups()
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- if quote not in ['"', "'"]:
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- warnings.warn("Basic Auth Realm was unquoted",
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- UserWarning, 2)
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- if scheme.lower() == 'basic':
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+ unsupported = None
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+ for header in headers:
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+ for scheme, realm in self._parse_realm(header):
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+ if scheme.lower() != 'basic':
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+ unsupported = scheme
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+ continue
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+
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+ if realm is not None:
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+ # Use the first matching Basic challenge.
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+ # Ignore following challenges even if they use the Basic
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+ # scheme.
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return self.retry_http_basic_auth(host, req, realm)
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+ if unsupported is not None:
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+ raise ValueError("AbstractBasicAuthHandler does not "
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+ "support the following scheme: %r"
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+ % (scheme,))
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+
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def retry_http_basic_auth(self, host, req, realm):
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user, pw = self.passwd.find_user_password(realm, host)
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if pw is not None:
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--
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2.30.1
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