* bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable
@ 2022-02-08 9:29 Ignacio Casso
2022-02-08 16:42 ` Glenn Morris
0 siblings, 1 reply; 4+ messages in thread
From: Ignacio Casso @ 2022-02-08 9:29 UTC (permalink / raw)
To: 53876
Hello,
I've noticed something that I believe it might be a bug. With Emacs 27.2
and the default configuration (starting with emacs -Q), I get the
following behavior:
If I visit a file ending with the three lines below, I get the usual
prompt asking whether I want to apply the local variables since they
might not be safe. So far so good.
# Local Variables:
# eval: (message "file was visited")
# End:
If I visit a file with the following local variables instead, I don't
get that prompt and the form is evaluated immediately, so I get line
numbers in the buffer. This happens for any other mode.
# Local Variables:
# eval: (display-line-numbers-mode)
# End:
I'm not sure if that is still good, but the real problem comes now, when I
define a function with a name ending in "-mode", like the following:
(defun not-really-a-mode ()
(message "This could be doing something nasty"))
If I visit a file with the following local variables, I don't get the
prompt either and the form is evaluated immediately.
# Local Variables:
# eval: (not-really-a-mode)
# End:
(Of course, activating an actual mode could be doing something equally
nasty, but somehow I find this worse)
I've investigated a little and found the function
hack-one-local-variable-eval-safep in files.el, which is responsible for
this. It has a comment that says "Allow (minor)-modes calls with no
arguments.", and just checks whether the function ends in "-mode".
I'm not sure if it's a bug or a feature, and it's not important at all
to me, since it's actually convenient. I'm just reporting it since I
noticed it and I'm trying to get in the habit of reporting (possible)
bugs when I find them.
Best regards,
Ignacio
In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.20)
of 2022-01-16 built on ignacio-IdeaPad-3-15ADA05
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Ubuntu 20.04.3 LTS
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable
2022-02-08 9:29 bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable Ignacio Casso
@ 2022-02-08 16:42 ` Glenn Morris
2022-02-09 1:08 ` Glenn Morris
2022-02-09 8:23 ` Lars Ingebrigtsen
0 siblings, 2 replies; 4+ messages in thread
From: Glenn Morris @ 2022-02-08 16:42 UTC (permalink / raw)
To: Ignacio Casso; +Cc: 53876
Thanks for the report.
Same issue with "-*- mode: not-really-a; -*-".
It's all intentional behaviour, but how sensible it is is a valid question.
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable
2022-02-08 16:42 ` Glenn Morris
@ 2022-02-09 1:08 ` Glenn Morris
2022-02-09 8:23 ` Lars Ingebrigtsen
1 sibling, 0 replies; 4+ messages in thread
From: Glenn Morris @ 2022-02-09 1:08 UTC (permalink / raw)
To: Ignacio Casso; +Cc: 53876
I suppose the assumption is that code already available in the user's
environment is not intrinsically malicious (ie does not contain
deliberately harmful mode definitions). Rather the file-local variables
safety mechanisms are intended to protect against malicious code
actually embedded in the file being visited; something like eval:
(shell-command ...).
It underlines again the need to be careful about what elisp libraries
one installs (although the simple act of installing a package can
already directly execute arbitrary code anyway).
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable
2022-02-08 16:42 ` Glenn Morris
2022-02-09 1:08 ` Glenn Morris
@ 2022-02-09 8:23 ` Lars Ingebrigtsen
1 sibling, 0 replies; 4+ messages in thread
From: Lars Ingebrigtsen @ 2022-02-09 8:23 UTC (permalink / raw)
To: Glenn Morris; +Cc: 53876, Ignacio Casso
Glenn Morris <rgm@gnu.org> writes:
> Thanks for the report.
>
> Same issue with "-*- mode: not-really-a; -*-".
>
> It's all intentional behaviour, but how sensible it is is a valid question.
I don't think this is something that we can change at this point,
though. If you've installed a package that defines a mode, then the
assumption is that it's safe.
So I don't think there's anything to fix here, and I'm therefore closing
this bug report.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-02-09 8:23 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-02-08 9:29 bug#53876: 27.2; "eval: (X-mode)" is always safe as file local variable Ignacio Casso
2022-02-08 16:42 ` Glenn Morris
2022-02-09 1:08 ` Glenn Morris
2022-02-09 8:23 ` Lars Ingebrigtsen
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