On Tue, Nov 07, 2017 at 10:21:12PM +0100, Bram Moolenaar wrote:
> Thanks.  The temp file is safe, since only the user can read the temp
> directory, but since it's move to the right place with a rename.

Hello,

I don't understand what you're saying here. Do you mean the
creation of the temp file in the fallback path is safe because
it's created in the vim temp directory which is only readable by
the user? But when it's renamed outside it's an issue (as
described above in the patch) because then the file which is
readable by all users becomes visible?

> Can you write a test for this?

I don't know how. It's a race condition which is difficult to
reproduce (file must not exist during mch_stat, but exist during
mch_open).

>> However this patch won't help users which were already affected
>> by this race condition as write_viminfo() retains the permissions
>> of an existing viminfo. As the use-case for a viminfo readable by
>> others doesn't seem very relevant to me, I recommend changing the
>> viminfo code to always enforce 0600 permissions to prevent this
>> kind of information leak (for affected users and in general).
>
> I wonder if this would ever cause problems.  I can't think of something.

Sounds good, I'll attach a second patch which will change the
behavior and enforce 0600.

Regards
Simon
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