Re: deleting content of /tmp

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On 03/24/07 23:07, Paul E Condon wrote:
On Sat, Mar 24, 2007 at 10:46:08PM -0500, Ron Johnson wrote:
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On 03/24/07 22:36, Roberto C. Sánchez wrote:
On Sat, Mar 24, 2007 at 10:33:40PM -0500, Ron Johnson wrote:
On 03/24/07 22:19, Roberto C. Sánchez wrote:
Out of curiousity, why do you say that it is a bad design?
Destroying something to save it?

It seems like it makes perfect sense (in the temporary file case, not in
the destroying a village case). If you know that the operating system
will keep the file data allocated and allow you use the file as normal
until you close it, then why not unlink it? It prevents collisions with
naming
That's what, in python syntax, os.tmpfile() is for.

and minimizes a vulnerability.
A rich-enough file protection and locking protocol is supposed to
handle that for you.

I wonder how the python run-time package actually implements an os.tmpfile
on a *nix system --- maybe by creating a file and then unlinking it?

Apparently so. :(

tmpfile()
Return a new file object opened in update mode ("w+b").
The file has no directory entries associated with it and
will be automatically deleted once there are no file
descriptors for the file. Availability: Macintosh, Unix,
Windows.

What I meant was os.tempnam(). Which the documentation indicates is
vulnerable to symlink attacks.

Not being able to exclusively lock a file is a definite weakness.
Enterprise OSs give you much richer file semantics. But... they're
heavier and slower.

- --
Ron Johnson, Jr.
Jefferson LA USA

Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!

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