/tmp does not exist on Android and is used by curses.window.putwin()

[xdegaye]

BPO	29176
Nosy	@Yhg1s, @vstinner, @tiran, @xdegaye, @serhiy-storchaka, @yan12125
PRs	bpo-29176: Fix name of the _curses.window class #52 curses: use tempfile.TemporaryFile for get/putwin #53 bpo-29176 Use tmpfile() in curses module #235 bpo-29176: curses: use tmpfile() for getwin/putwin #237 [3.6] bpo-29176: Fix name of the _curses.window class (GH-52) #532
Files	ncurses.patch mkstemp_curses.patch curses_temporaryfile.patch curses_fix_window_class_name.patch

^{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 2017-03-27.11:15:29.155>
created_at = <Date 2017-01-06.10:47:00.717>
labels = ['type-security', 'extension-modules', '3.7']
title = '/tmp does not exist on Android and is used by curses.window.putwin()'
updated_at = <Date 2017-03-27.11:15:29.153>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2017-03-27.11:15:29.153>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2017-03-27.11:15:29.155>
closer = 'vstinner'
components = ['Extension Modules']
creation = <Date 2017-01-06.10:47:00.717>
creator = 'xdegaye'
dependencies = []
files = ['46266', '46267', '46622', '46623']
hgrepos = []
issue_num = 29176
keywords = ['patch']
message_count = 30.0
messages = ['284810', '284819', '285310', '285320', '285321', '285322', '287511', '287512', '287514', '287521', '287643', '287645', '288006', '288011', '288303', '288308', '288348', '288350', '288352', '288359', '288384', '288440', '288441', '288794', '288795', '288989', '290259', '290349', '290440', '290585']
nosy_count = 6.0
nosy_names = ['twouters', 'vstinner', 'christian.heimes', 'xdegaye', 'serhiy.storchaka', 'yan12125']
pr_nums = ['52', '53', '235', '237', '532']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'security'
url = 'https://bugs.python.org/issue29176'
versions = ['Python 3.6', 'Python 3.7']

[xdegaye]

======================================================================
ERROR: test_module_funcs (test.test_curses.TestCurses)
Test module-level functions
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/sdcard/org.bitbucket.pyona/lib/python3.7/test/test_curses.py", line 219, in test_module_fun
cs
    self.stdscr.putwin(f)
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/py.curses.putwin.nsIZYY'

---

[yan12125]

I guess replace mkstemp (C function) with tempfile.mkstemp (Python function) can solve the problem.

[xdegaye]

The test suite runner in the test.libregrtest.main module calls tempfile.gettempdir() and mkstemp_curses.patch uses the same logic to fix the problem on Android where the tests that I run use TMPDIR=/data/local/tmp on Android API 24.

As a side note, when the curses library is ncurses-6.0, the library must be patched in ncurses/base/lib_screen.c with the attached ncurses.patch, see:
http://lists.gnu.org/archive/html/bug-ncurses/2016-05/msg00000.html
https://bugs.python.org/issue27323

[vstinner]

The putwin() function uses mkstemp() with the path template /tmp/py.curses.getwin.XXXXXX.

I would prefer to use the Python function tempfile.mkstemp(). This function has a more portable behaviour. For example, Python is able to atomatically make the file descriptor non-inherirable if the OS supports this feature.

I suggest to expect a file descriptor in the C putwin() and write a Python putwin() which expects a file and pass file.fileno() if available, or use tempfile.TemporaryFile().

tempfile.TemporaryFile is even more secure because the file is not accessible from the regular file system on most platforms. This function is able to use the secure Linux O_TMPFILE flag and the O_TEMPORARY flag on Windows.

[vstinner]

I change the issue type to security.

[vstinner]

Oops, I missed Chi Hsuan Yen's comment:

I guess replace mkstemp (C function) with tempfile.mkstemp (Python function) can solve the problem.

So yes, I agree :-)

[vstinner]

curses_temporaryfile.patch: Call tempfile.TemporaryFile in getwin() and putwin() to create the temporary file in a more portable and safer manner.

The curses library requires a FILE* object, but TemporaryFile.close() must be called to remove the temporary file. So I chose to duplicate the file descriptor, so we can close fclose() and tmpfile.close().

I chose to modify the C rather rather than trying to implement a window class in Python, because the C window class is part of a "PyCurses_API", and many C functions instanciate the C class.

[vstinner]

curses_fix_window_class_name.patch: Fix the name of the C window class: "_curses.window", not "_curses.curses window" (with a space in the class name) !?

The following example current displays <class '_curses.curses window'>:
---

import curses
w = curses.initscr()
curses.endwin()
print(type(w))

---