From: charles@aurox.ch (Charles A. Roelli)
To: Eli Zaretskii <eliz@gnu.org>
Cc: 28350@debbugs.gnu.org
Subject: bug#28350: enriched.el code execution
Date: Sat, 09 Sep 2017 17:57:10 +0200 [thread overview]
Message-ID: <m27ex7amqx.fsf@aurox.ch> (raw)
In-Reply-To: <838thovvcr.fsf@gnu.org> (message from Eli Zaretskii on Sat, 09 Sep 2017 16:45:40 +0300)
Thanks for the feedback.
> Date: Sat, 09 Sep 2017 16:45:40 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> CC: 28350@debbugs.gnu.org
> Reply-to: Eli Zaretskii <eliz@gnu.org>
>
> > --- a/lisp/textmodes/enriched.el
> > +++ b/lisp/textmodes/enriched.el
> > @@ -503,6 +503,47 @@ enriched-decode-display-prop
> > (error nil)))))
> > (unless prop
> > (message "Warning: invalid <x-display> parameter %s" param))
> > - (list start end 'display prop)))
> > + (if (enriched-display-prop-safe-p prop)
> > + (list start end 'display prop)
> > + (message "Warning: unsafe <x-display> parameter %s not applied" param)
> > + (list start end))))
>
> I think we will want to allow unsafe display properties, given a
> user's explicit permission. So I think we need a defcustom that
> allows this, and then enriched-display-prop-safe-p should always
> return non-nil.
Agreed, I've added this.
> > +See Info node `(elisp)Display Property' for the use of these
> > +display specifications."
> > + (ignore-errors
> > + (or (stringp prop)
> ^^^^^^^^^^^^
> What about an image spec (including a slice spec)?
Okay, I see that image specs can be safe. But are they all safe?
And I don't understand how a slice spec is used together with an image
spec. Is the slice spec used inside of IMAGE-PROPS, i.e. as you might
gather from the manual:
‘(image . IMAGE-PROPS)’
This kind of display specification is an image descriptor (*note
Images). When used as a display specification, it means to
display the image instead of the text that has the display
specification.
‘(slice X Y WIDTH HEIGHT)’
This specification together with ‘image’ specifies a “slice” (a
partial area) of the image to display.
?
>
> > + (and (eq (car prop) 'space-width)
> > + (or (integerp (cadr prop)) (floatp (cadr prop))))
> > + (and (consp (car prop))
> > + (eq (caar prop) 'margin)
> > + (or (eq (cadar prop) 'right-margin)
> > + (eq (cadar prop) 'left-margin))
> > + (stringp (cadr prop)))
>
> The margin display can also specify an image, not just a string, and I
> think that would be safe as well.
Okay, I'll apply the same procedure as we decide for the above image
spec.
>
> > + (and (eq (car prop) 'height)
> > + (or (integerp (cadr prop))
> > + (and (listp (cadr prop))
> > + (or (eq (elt (cadr prop) 0) '+) (elt (cadr prop) 0) '-)
> > + (integerp (elt (cadr prop) 1)))))
> ^^^^^^^^
> I think this should be numberp, as the value could also safely be a
> float.
>
> > + (and (eq (car prop) 'raise)
> > + (integerp (cadr prop))))))
> ^^^^^^^^
> The FACTOR in (raise FACTOR) can also be a float, so I think numberp
> is the correct predicate here.
>
> And then what about (space . PROPS) type of display spec? I think all
> of its variants are safe.
Okay, I've made these changes and added the `space' spec. At this
point it seems that unsafe display specs are more the exception than
the rule, so it might make sense to define the
`enriched-display-prop-safe-p' function by excluding the unsafe
specifications instead of including the safe ones. What do you think?
next prev parent reply other threads:[~2017-09-09 15:57 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 19:24 bug#28350: enriched.el code execution Charles A. Roelli
2017-09-06 19:25 ` Charles A. Roelli
2017-09-07 2:34 ` Eli Zaretskii
2017-09-09 12:23 ` Charles A. Roelli
2017-09-09 13:45 ` Eli Zaretskii
2017-09-09 15:57 ` Charles A. Roelli [this message]
2017-09-09 16:55 ` Eli Zaretskii
2017-09-09 20:37 ` Charles A. Roelli
2017-09-10 17:01 ` Eli Zaretskii
2017-09-11 16:32 ` Glenn Morris
2017-09-11 17:01 ` Eli Zaretskii
2017-09-09 22:43 ` Paul Eggert
2017-09-10 18:54 ` Charles A. Roelli
2017-09-10 21:46 ` Paul Eggert
2017-09-11 2:39 ` Eli Zaretskii
2017-09-11 14:22 ` Eli Zaretskii
2017-09-11 15:18 ` Eli Zaretskii
2017-09-11 18:44 ` Charles A. Roelli
2017-09-11 19:07 ` Eli Zaretskii
2017-09-16 9:48 ` Eli Zaretskii
2017-09-11 15:33 ` Glenn Morris
2017-09-11 16:38 ` Paul Eggert
2017-09-11 21:16 ` Glenn Morris
2017-09-12 19:59 ` Paul Eggert
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