Re: [elpa] externals-release/org e2366ac283: * lisp/org-persist.el: Do not litter /tmp when native compiling

[Ihor Radchenko <yantar92@posteo.net>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> +  (setq org-persist-directory
>> +        (make-temp-file "org-persist-" 'dir))
>> +  ;; We don't need the temp directory to exist.
>> +  ;; `org-persist-write-all' will refrain from creating and writing to the dir if
>> +  ;; none exists yet.
>> +  (delete-directory org-persist-directory))
>
> Could we skip the "create dir" so we can skip the `delete-directory`
> part as well?

It would be wonderful, but

    There is a race condition between calling make-temp-name and
    later creating the file, which opens all kinds of security holes.
    For that reason, you should normally use make-temp-file instead.

which scared me.

> Also, this smells like a security hole: after `delete-directory`, with
> the /tmp setup as mode #o1777, some other user can come and create
> a directory at that location, so that our `org-persist-directory` will
> then point to their directory (where they may be able to read the
> things we write) or they can replace it with a link to a directory of
> our own tricking us into overwriting some of our own files.

This also means that other user has access to Elisp machine state (the
value of org-persist-directory). If we are in that situation, your
scenario is the least of our concerns. Also, do note that this branch of
code is only executed with emacs -Q.

> IOW, I suggest we use something like
>
>     (setq org-persist-directory "/non-existing")
> or
>     (setq org-persist-directory (make-temp-name "/non-existing"))
>
> [ Not sure if there is a standard such name that's "guaranteed" not to
>   exist.  ]

If you confirm that it is safe to use `make-temp-name' here, I will go
with your suggestion.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
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