[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Wrong commit message in 3.6. Should be the same as in 3.5.

This functionality was backported as a private function 
_PyUnicode_AsWideCharString().

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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:


New changeset 94b169fe48bc7ea76b926823885d1b12c2c381fa by Serhiy Storchaka in 
branch '3.5':
[3.5] bpo-30708: Add private C API function _PyUnicode_AsWideCharString(). 
(GH-2285) (GH-2443)  (#2448)
https://github.com/python/cpython/commit/94b169fe48bc7ea76b926823885d1b12c2c381fa


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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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pull_requests: +2505

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:


New changeset 0edffa3073b551ffeca34952529e7b292f1bd350 by Serhiy Storchaka in 
branch '3.6':
[3.6] bpo-30708: Check for null characters in PyUnicode_AsWideCharString(). 
(GH-2285) (#2443)
https://github.com/python/cpython/commit/0edffa3073b551ffeca34952529e7b292f1bd350


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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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pull_requests: +2497

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:


New changeset e613e6add5f07ff6aad5802924596b631b707d2a by Serhiy Storchaka in 
branch 'master':
bpo-30708: Check for null characters in PyUnicode_AsWideCharString(). (#2285)
https://github.com/python/cpython/commit/e613e6add5f07ff6aad5802924596b631b707d2a


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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Could anyone please make a review of this PR? Especially the documentation 
part. This PR is a part of a set of PRs that fix potential vulnerabilities 
(issue13617, issue30730, and yet few issues planned).

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

This change needs changing one ctypes test, and can break third-party tests or 
even a code. That is why it is targeted only for 3.7. I'm going to backport the 
change as a private function for using in CPython internally since this can fix 
vulnerabilities.

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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pull_requests: +2333

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[issue30708] Ensure that the result of PyUnicode_AsWideCharString() doesn't contain null characters if size is not returned

[Serhiy Storchaka]

New submission from Serhiy Storchaka:

The second parameter of the PyUnicode_AsWideCharString() function

wchar_t* PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)

is a pointer to Py_ssize_t. The size of created wchar_t array is saved on this 
pointer if it is not NULL. If NULL is passed as the second argument, the only 
way to determine the size of the wchar_t string is using wcslen(). But if the 
string contains the null characters, it looks truncated for wcslen() and other 
C API functions.

Reliable code should always pass the non-NULL second argument and check that 
wcslen() is equal to the returned string size. See for example the code in 
Modules/_io/winconsoleio.c. Passing NULL as the second argument is unsafe. But 
most code doesn't do such check (see all other usages of 
PyUnicode_AsWideCharString(..., NULL)). And this check complicates the callers 
code.

I propose to make the check for null characters inside of 
PyUnicode_AsWideCharString() if NULL is passes as the second argument. This 
will fix all unsafe usages of PyUnicode_AsWideCharString() and allow to 
simplify the reliable code.

This issue fixes the part of issue13617.

--
components: Interpreter Core, Unicode
messages: 296401
nosy: ezio.melotti, haypo, serhiy.storchaka, steve.dower
priority: normal
severity: normal
stage: patch review
status: open
title: Ensure that the result of PyUnicode_AsWideCharString() doesn't contain 
null characters if size is not returned
type: enhancement
versions: Python 3.7

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