changeset
[svn] Steel FilenameChecker against race conditions.
Sun, 20 Jan 2008 15:32:02 -0500
- author
- brett
- date
- Sun, 20 Jan 2008 15:32:02 -0500
- branch
- trunk
- changeset 58
- 16506464d57b
- parent 57
- 5f6afe2cf9e1
- child 59
- 7a0aafe2fe87
[svn] Steel FilenameChecker against race conditions.
Since FilenameChecker was just using os.path.exists() to see whether or not
a filename was free, it had a time of check vs. time of use vulnerability.
Matthew was prodding me about the inconsistency with DirectoryChecker, so
that inspired me to fix this. This also entailed some refactoring. Thanks
Matthew.
| scripts/dtrx | file | annotate | diff | comparison | revisions |
--- a/scripts/dtrx Sun Jan 20 13:42:48 2008 -0500 +++ b/scripts/dtrx Sun Jan 20 15:32:02 2008 -0500 @@ -71,11 +71,23 @@ logger = logging.getLogger('dtrx-log') class FilenameChecker(object): + free_func = os.open + free_args = (os.O_CREAT | os.O_EXCL,) + free_close = os.close + def __init__(self, original_name): self.original_name = original_name def is_free(self, filename): - return not os.path.exists(filename) + try: + result = self.free_func(filename, *self.free_args) + except OSError, error: + if error.errno == errno.EEXIST: + return False + raise + if self.free_close: + self.free_close(result) + return True def create(self): fd, filename = tempfile.mkstemp(prefix=self.original_name + '.', @@ -84,8 +96,6 @@ return filename def check(self): - if self.is_free(self.original_name): - return self.original_name for suffix in [''] + ['.%s' % (x,) for x in range(1, 10)]: filename = '%s%s' % (self.original_name, suffix) if self.is_free(filename): @@ -94,14 +104,9 @@ class DirectoryChecker(FilenameChecker): - def is_free(self, filename): - try: - os.mkdir(filename) - except OSError, error: - if error.errno == errno.EEXIST: - return False - raise - return True + free_func = os.mkdir + free_args = () + free_close = None def create(self): return tempfile.mkdtemp(prefix=self.original_name + '.', dir='.')
