CVE-2019-10160: urlsplit NFKD normalization vulnerability in user:password@

[hokousya]

BPO	36742
Nosy	@orsenthil, @vstinner, @larryhastings, @benjaminp, @ned-deily, @ezio-melotti, @ambv, @zooba, @stratakis, @miss-islington, @tirkarthi, @ret2libc
PRs	bpo-36742: Fixes handling of pre-normalization characters in urlsplit() #13017 [3.7] bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) #13023 [3.6] bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) #13024 [2.7] bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) #13025 [3.5] bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) #13042 bpo-36742: Corrects fix to handle decomposition in usernames #13812 [3.7] bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) #13813 [3.6] bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) #13814 [2.7] bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) #13815 [2.7] bpo-36742: Fix urlparse.urlsplit() error message for Unicode URL #13937 [3.5] bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) (GH-13814) #14772

^{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 = 'https://github.com/zooba'
closed_at = <Date 2019-05-01.15:04:11.989>
created_at = <Date 2019-04-27.12:30:16.902>
labels = ['type-security', '3.7', '3.8', 'expert-unicode', 'release-blocker']
title = 'CVE-2019-10160: urlsplit NFKD normalization vulnerability in user:password@'
updated_at = <Date 2019-09-07.06:33:27.509>
user = 'https://bugs.python.org/hokousya'

bugs.python.org fields:

activity = <Date 2019-09-07.06:33:27.509>
actor = 'larry'
assignee = 'steve.dower'
closed = True
closed_date = <Date 2019-05-01.15:04:11.989>
closer = 'steve.dower'
components = ['Unicode']
creation = <Date 2019-04-27.12:30:16.902>
creator = 'hokousya'
dependencies = []
files = []
hgrepos = []
issue_num = 36742
keywords = ['patch', '3.5regression', '3.6regression', '3.7regression']
message_count = 23.0
messages = ['340983', '341006', '341092', '341125', '341150', '341151', '341171', '341206', '341207', '341208', '341212', '341282', '344595', '344596', '344597', '344601', '344623', '344973', '344981', '345116', '345218', '347880', '351285']
nosy_count = 13.0
nosy_names = ['orsenthil', 'vstinner', 'larry', 'benjamin.peterson', 'ned.deily', 'ezio.melotti', 'lukasz.langa', 'steve.dower', 'cstratak', 'miss-islington', 'xtreak', 'hokousya', 'rschiron']
pr_nums = ['13017', '13023', '13024', '13025', '13042', '13812', '13813', '13814', '13815', '13937', '14772']
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'security'
url = 'https://bugs.python.org/issue36742'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7', 'Python 3.8']

[hokousya]

urllib.parse.urlsplit raises an exception for an url including a non-ascii hostname in NFKD form and a port number.

example:
>>> urlsplit('http://\u30d5\u309a:80')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/ito/.maltybrew/deen/lib/python3.7/urllib/parse.py", line 437, in urlsplit
    _checknetloc(netloc)
  File "/Users/ito/.maltybrew/deen/lib/python3.7/urllib/parse.py", line 407, in _checknetloc
    "characters under NFKC normalization")
ValueError: netloc 'プ:80' contains invalid characters under NFKC normalization
>>> urlsplit('http://\u30d5\u309a')
SplitResult(scheme='http', netloc='プ', path='', query='', fragment='')
>>> urlsplit(unicodedata.normalize('NFKC', 'http://\u30d5\u309a:80'))
SplitResult(scheme='http', netloc='プ:80', path='', query='', fragment='')

I believe this behavior was introduced at Python 3.7.3. Python 3.7.2 doesn't raise any exception for these lines.

[tirkarthi]

This could be due to bpo-36216.

[zooba]

Yes, it's due to that. I guess we need to do netloc.rpartition(':') like we currently do for '@' in _checknetloc.

Promoting to release blocker and security issue to match the original issue. I can't get to this today, but I should be able to at the PyCon sprints next week if nobody else gets it sooner.

[zooba]

I found the time to get the first patch. Hopefully backports to 3.6 and 3.7 are easy, but I think 2.7 will take manual steps.

Chihiro Ito - if you have other test scenarios, it would be great if you could try them out with the fix in PR 13017. It should be easy enough to copy into your installed Python.

[zooba]

New changeset d537ab0 by Steve Dower in branch 'master':
bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017)
d537ab0

[miss-islington]

New changeset 4d723e7 by Miss Islington (bot) in branch '3.7':
bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017)
4d723e7

[hokousya]

I have confirmed that all of my app's test cases have passed.

What I've done:

1. Installed Python 3.7.3.
2. Replaced urllib/parse.py with the one from 781ffb1.
3. Ran my app's test cases.

Thank you for the quick fix!

[zooba]

New changeset 98a4dce by Steve Dower in branch '2.7':
bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017)
98a4dce

[zooba]

I'll leave the 3.6 backport in Ned's hands and close this issue.

[tirkarthi]

I'll leave the 3.6 backport in Ned's hands and close this issue.

3.5 was added as an affected version and seems the original fix was merged to 3.5 too. 3.4 is EoL so is it worthy of backporting to 3.5? I guess the backport would not have merge conflicts and is straightforward.

[zooba]

Yes, you're right. I'll do that port as well.

[ned-deily]

New changeset e5f9f4a by Ned Deily (Miss Islington (bot)) in branch '3.6':
bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) (GH-13024)
e5f9f4a

[ambv]

New changeset 8d0ef0b by Łukasz Langa (Steve Dower) in branch 'master':
bpo-36742: Corrects fix to handle decomposition in usernames (bpo-13812)
8d0ef0b

[orsenthil]

Thanks for this engagement and pull requests, Steve.
Thanks for reviews Karthikeyan.

[miss-islington]

New changeset 250b62a by Miss Islington (bot) in branch '3.7':
bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812)
250b62a

[zooba]

New changeset f61599b by Steve Dower in branch '2.7':
bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812)
f61599b

[ned-deily]

New changeset fd1771d by Ned Deily (Miss Islington (bot)) in branch '3.6':
bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) (GH-13814)
fd1771d

[vstinner]

CVE-2019-10160 has been assigned by Red Hat to this flaw.

[ret2libc]

The fix for python-2.7 (https://github.com/python/cpython/pull/13815/files#diff-b577545d73dd0cdb2c337a4c5f89e1d7R183) causes errors when netloc contains characters that can't be encoded by 'ascii' codec.

You can see it by doing:
>>> netloc = u'example.com\uFF03@bing.com'
>>> raise ValueError(u"netloc '" + netloc + u"' contains invalid characters under NFKC normalization")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: <exception str() failed>
>>> str(netloc)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode character u'\uff03' in position 11: ordinal not in range(128)

I suggest we use repr(netloc) instead of netloc in the ValueError message.

[ret2libc]

CVE-2019-10160 has been assigned by Red Hat to this flaw.

For clarity, CVE-2019-10160 has been assigned to the bug introduced with the fix for the functional regression mentioned in this bug, and not to the bug itself explained in the first comment. See https://bugzilla.redhat.com/show_bug.cgi?id=1718388 for more details about it.

[vstinner]

New changeset 2b57847 by Victor Stinner in branch '2.7':
[2.7] bpo-36742: Fix urlparse.urlsplit() error message for Unicode URL (GH-13937)
2b57847

[larryhastings]

New changeset 4655d57 by larryhastings (Steve Dower) in branch '3.5':
bpo-36742: Fixes handling of pre-normalization characters in urlsplit() (GH-13017) (bpo-13042)
4655d57

[larryhastings]

New changeset 095373c by larryhastings (Victor Stinner) in branch '3.5':
bpo-36742: Corrects fix to handle decomposition in usernames (GH-13812) (GH-13814) (bpo-14772)
095373c