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_random.Random state corrupted on exception #74146

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bladebryan mannequin opened this issue Apr 1, 2017 · 8 comments
Closed

_random.Random state corrupted on exception #74146

bladebryan mannequin opened this issue Apr 1, 2017 · 8 comments
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@serhiy-storchaka
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3.7 (EOL) end of life stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@bladebryan
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bladebryan mannequin commented Apr 1, 2017

BPO 29960
Nosy @rhettinger, @mdickinson, @serhiy-storchaka, @bladebryan, @Mariatta
PRs
  • bpo-29960 _random.Random state corrupted on exception. #953
  • bpo-29960 _random.Random corrupted on exception in setstate(). #1019
  • [3.6] bpo-29960 _random.Random corrupted on exception in setstate(). … #1287
  • [3.5] bpo-29960 _random.Random corrupted on exception in setstate(). … #1288
  • [2.7] bpo-29960 _random.Random corrupted on exception in setstate(). … #1289
    		•

    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/serhiy-storchaka'
closed_at = <Date 2017-05-27.14:22:10.000>
created_at = <Date 2017-04-01.10:46:26.025>
labels = ['3.7', 'type-bug', 'library']
title = '_random.Random state corrupted on exception'
updated_at = <Date 2017-05-27.14:22:09.999>
user = 'https://github.com/bladebryan'

    bugs.python.org fields:

    activity = <Date 2017-05-27.14:22:09.999>
actor = 'Mariatta'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2017-05-27.14:22:10.000>
closer = 'Mariatta'
components = ['Library (Lib)']
creation = <Date 2017-04-01.10:46:26.025>
creator = 'bryangeneolson'
dependencies = []
files = []
hgrepos = []
issue_num = 29960
keywords = []
message_count = 8.0
messages = ['290977', '290979', '292108', '293927', '294590', '294591', '294592', '294593']
nosy_count = 5.0
nosy_names = ['rhettinger', 'mark.dickinson', 'serhiy.storchaka', 'bryangeneolson', 'Mariatta']
pr_nums = ['953', '1019', '1287', '1288', '1289']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29960'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']
    @bladebryan
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    bladebryan mannequin commented Apr 1, 2017

    Demo:

    Run the Python library's test_random.py under the Python debugger and check the
    generator at the start of test_shuffle():

    C:\bin\Python36>python -m pdb Lib\test\test_random.py

    c:\bin\python36\lib\test\test_random.py(1)<module>()
    -> import unittest
    (Pdb) break 61
    Breakpoint 1 at c:\bin\python36\lib\test\test_random.py:61
    (Pdb) continue
    .............................> c:\bin\python36\lib\test\test_random.py(61)test_shuffle()
    -> shuffle = self.gen.shuffle
    (Pdb) list
    56 # randomness source is not available.
    57 urandom_mock.side_effect = NotImplementedError
    58 self.test_seedargs()
    59
    60 def test_shuffle(self):
    61 B-> shuffle = self.gen.shuffle
    62 lst = []
    63 shuffle(lst)
    64 self.assertEqual(lst, [])
    65 lst = [37]
    66 shuffle(lst)
    (Pdb) p self.gen.getrandbits(31)
    2137781566
    (Pdb) p self.gen.getrandbits(31)
    2137781566
    (Pdb) p self.gen.getrandbits(31)
    2137781566
    (Pdb) p self.gen.getrandbits(31)
    2137781566
    (Pdb) p self.gen.getrandbits(31)
    2137781566

    That's not random.

    Diagnosis:

    The order in which test functions run is the lexicographic order of their names. Thus unittest ran test_setstate_middle_arg() before running test_shuffle(). test_setstate_middle_arg() did some failed calls to _random.Random.setstate(), which raised exceptions as planned, but also trashed the state of the generator. test_random.py continues to use the same instance of _random.Random after setstate() raises exceptions.

    The documentation for Random.setstate() does not specify what happens to the state of the generator if setstate() raises an exception. Fortunately the generator recommended for secure applications, SystemRandom, does not implement setstate().

    Solution:

    The fix I prefer is a small change to random_setstate() in _randommodule.c, so that it does not change the state of the generator until the operation is sure to succeed.

    @bladebryan bladebryan mannequin added 3.7 (EOL) end of life stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Apr 1, 2017
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    bladebryan mannequin commented Apr 1, 2017

    I'm going through https://docs.python.org/devguide/pullrequest.html and would like to be assigned this issue.

    @rhettinger rhettinger assigned rhettinger and unassigned rhettinger Apr 1, 2017
    @serhiy-storchaka
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    New changeset 9616a82 by Serhiy Storchaka (bladebryan) in branch 'master':
    bpo-29960 _random.Random corrupted on exception in setstate(). (bpo-1019)
    9616a82

    @serhiy-storchaka serhiy-storchaka self-assigned this Apr 22, 2017
    @serhiy-storchaka
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    Mariatta, can you update your PRs?

    @Mariatta
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    New changeset 440bc4f by Mariatta in branch '3.5':
    [3.5] bpo-29960 _random.Random corrupted on exception in setstate(). … (bpo-1288)
    440bc4f

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    New changeset 1626a47 by Mariatta in branch '2.7':
    [2.7] bpo-29960 _random.Random corrupted on exception in setstate(). … (bpo-1289)
    1626a47

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    New changeset 94d8261 by Mariatta in branch '3.6':
    [3.6] bpo-29960 _random.Random corrupted on exception in setstate(). … (bpo-1287)
    94d8261

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    Thanks Bryan and Serhiy.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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