bug#28350: enriched.el code execution

[Charles A. Roelli]

> Date: Thu, 07 Sep 2017 05:34:34 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> CC: 28350@debbugs.gnu.org
> 
> > Date: Wed, 06 Sep 2017 21:25:18 +0200
> > From: charles@aurox.ch (Charles A. Roelli)
> > 
> > As for a fix to apply to master: I'd like to keep "x-display" if we
> > can agree on some "safe" predicate that the given parameter would have
> > to satisfy.  Looking at the list of display specifications that are
> > available, it seems that simple string, margin text, space-width,
> > height (only in the (+ n), (- n) and n cases) and raise specifications
> > should be okay.  Does anybody else have an opinion about this?
> 
> I agree that the cases you have shown are safe.
> 
> Thanks.

Thank you.  Does the attached patch look OK?  I've used the file
enriched-test-safe-props.txt (also attached) to test that safe
properties are still applied.

0001-Prevent-code-execution-by-text-enriched-files-Bug-28.patch
Description: Text Data

Content-Type: text/enriched Text-Width: 70
<x-display>"replace"test</x-display>
<x-display>(space-width 5)large spaces</x-display>
<x-display>((margin left-margin) "string")marginal text</x-display>
<x-display>(height 3)tall text</x-display>
<x-display>(raise 5)raised text</x-display>