Re: creating backups in temporary directories

[Andreas Schwab <schwab@suse.de>]

David Kastrup <dak@gnu.org> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>> In a directory with mode 777, that's true: everything is dangerous.
>> But in a directory with mode 1777 when you open a file that *you* own,
>> nobody else can remove it or rename it, so normally nobody can replace it
>> with a symlink.  Emacs creates the problem when it moves /tmp/foo to
>> /tmp/foo~ at which point /tmp/foo is free for an attacker to take.
>
> Well, the alternative is to make a hard link of /tmp/foo to /tmp/foo~,
> then creat /tmp/foo over it and fill it with contents without
> reopening.
>
> That should close the time window for an attack.

You have to unlink the file first, so the window remains.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
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