Issue #12856: Ensure child processes do not inherit the parent's random seed for filename generation in the tempfile module.

Patch by Brian Harring.
This commit is contained in:
Antoine Pitrou 2011-11-25 21:29:27 +01:00
commit c24847658f
3 changed files with 43 additions and 2 deletions

View File

@ -108,8 +108,13 @@ class _RandomNameSequence:
characters = "abcdefghijklmnopqrstuvwxyz0123456789_"
def __init__(self):
self.rng = _Random()
@property
def rng(self):
cur_pid = _os.getpid()
if cur_pid != getattr(self, '_rng_pid', None):
self._rng = _Random()
self._rng_pid = cur_pid
return self._rng
def __iter__(self):
return self

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@ -1,6 +1,7 @@
# tempfile.py unit tests.
import tempfile
import os
import signal
import sys
import re
import warnings
@ -135,6 +136,37 @@ class test__RandomNameSequence(TC):
except:
self.failOnException("iteration")
@unittest.skipUnless(hasattr(os, 'fork'),
"os.fork is required for this test")
def test_process_awareness(self):
# ensure that the random source differs between
# child and parent.
read_fd, write_fd = os.pipe()
pid = None
try:
pid = os.fork()
if not pid:
os.close(read_fd)
os.write(write_fd, next(self.r).encode("ascii"))
os.close(write_fd)
# bypass the normal exit handlers- leave those to
# the parent.
os._exit(0)
parent_value = next(self.r)
child_value = os.read(read_fd, len(parent_value)).decode("ascii")
finally:
if pid:
# best effort to ensure the process can't bleed out
# via any bugs above
try:
os.kill(pid, signal.SIGKILL)
except EnvironmentError:
pass
os.close(read_fd)
os.close(write_fd)
self.assertNotEqual(child_value, parent_value)
test_classes.append(test__RandomNameSequence)

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@ -395,6 +395,10 @@ Core and Builtins
Library
-------
- Issue #12856: Ensure child processes do not inherit the parent's random
seed for filename generation in the tempfile module. Patch by Brian
Harring.
- Issue #9957: SpooledTemporaryFile.truncate() now accepts an optional size
parameter, as other file-like objects. Patch by Ryan Kelly.