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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<http://bugs.python.org/issue30708>
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