Re: possible issue with ps2pdf (9.25) and transparency

At 14:02 15/09/2018 -0700, Paul Wessel wrote:


>We also just noticed a regression w.r.t. transparency today. Â 9.23 
>handled transparency correctly, 9.24 broke it, and I just built 9.25 today 
>and it still has that problem.

As noted (several times now) on this list, including my reply to the email 
you quoted, this is not a regression, it is a deliberate change in behaviour.

The (non-standard) PostScript extensions for transparency in Ghostscript 
were recently used in the series of publicly announced exploits, by abusing 
the operands to these operators.

As a result we have chosen to restrict these operators when -dSAFER is true 
(because, obviously, these are not safe)

As I also noted, there is an internal review in progress of all the 
non-standard PostScript extensions in Ghostscript. You can expect a number 
more to disappear, when running in SAFER mode.


>Attached is a 26-line ps file that plots two overlapping squares, the blue 
>is transparent.  The following gs command produces the PDF which was 
>transparent for versions prior to 9.24.
>
>gs -q -dSAFER -dNOPAUSE -dBATCH -sDEVICE=pdfwrite  -g2160x2160 -r720 
>-sOutputFile=gsbug.pdf -<http://fgsbug.ps>fgsbug.ps

Don't specify -dSAFER.


                     Ken