readline.py file in current directory caused unexpected code execution.

[HirokiKiyohara]

BPO	25288
Nosy	@bitdancer, @4kir4, @zhangyangyu
Superseder	bpo-12238: Readline module loading in interactive mode

^{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 = <Date 2015-10-01.14:03:10.133>
created_at = <Date 2015-10-01.09:26:41.857>
labels = ['type-security']
title = 'readline.py file in current directory caused unexpected code execution.'
updated_at = <Date 2015-10-02.23:25:41.705>
user = 'https://bugs.python.org/HirokiKiyohara'

bugs.python.org fields:

activity = <Date 2015-10-02.23:25:41.705>
actor = 'akira'
assignee = 'none'
closed = True
closed_date = <Date 2015-10-01.14:03:10.133>
closer = 'r.david.murray'
components = []
creation = <Date 2015-10-01.09:26:41.857>
creator = 'Hiroki Kiyohara'
dependencies = []
files = []
hgrepos = []
issue_num = 25288
keywords = []
message_count = 6.0
messages = ['252012', '252015', '252027', '252028', '252077', '252180']
nosy_count = 4.0
nosy_names = ['r.david.murray', 'akira', 'xiang.zhang', 'Hiroki Kiyohara']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '12238'
type = 'security'
url = 'https://bugs.python.org/issue25288'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3', 'Python 3.4', 'Python 3.5', 'Python 3.6']

[HirokiKiyohara]

Running python interpreter will import readline.py file in current directory.
It causes unexpected code execution.

This problem is reported by 'Japan Vulnerability Notes' as a bug on
Windows version Python http://jvn.jp/jp/JVN49503705/

It says that when we run Windows version python will import readline.pyd file in current directory. And it may run unexpected codes with permission assigned to python.exe.

The line causing this problem may be...
https://github.com/python/cpython/blob/2.7/Lib/code.py#L303

Should it be considered as vulnerability of python (or Windows version python)?

[zhangyangyu]

I can reproduce this action on Ubuntu.

The forged readline.py in python's execution directory can steal the
permission of python and do something dangerous.

[bitdancer]

This is not a bug, this is the way python works. When running in interactive mode (only) the current directory is first on the path.

Now, should this behavior be changed? I think we've discussed this before and decided not to change it (for backward compatibility reasons), but I think there was dissent and that increasing emphasis on security since that discussion might argue for a different outcome. It's a python-dev mailing list level issue, in any case.

[bitdancer]

Well, so much for my memory :(.

The actual discussion was in bpo-12238, where *my* conclusion was that this should be fixed (readline should be special cased), but the issue is still open.

Patches welcome :)

[HirokiKiyohara]

I see. Thank you very much, guys.

[4kir4]

python3 -I

could be used as a workaround.