Re: possible issue with ps2pdf (9.25) and transparency

At 13:32 15/09/2018 -0400, James Cloos wrote:


>KS> Without a complete Ghostscript command line, and an example file to
>KS> look at, no.
>
>The ps file uses .setopacityalpha to specify the alpha.
>
>This is a regression and should be fixed.

No, its a change in behaviour, and its quite specific and deliberate.

One of the exploits reported publicly relied upon using the transparency 
operators in an unexpected way. On inspection the internal code wasn't 
proof against this kind of attack, and couldn't easily be made so.

Since this is *not* standard PostScript we opted to remove the operator, 
**when SAFER is set**.

As I mentioned in my previous reply. there is an ongoing internal review of 
the attack vectors that were used, and we are looking into the various 
areas of the code that were exploited and ways to ensure we don't get 
caught out again. The last time we went through this exercise we removed 
access to some operators, this time round we removed some more, but only 
when -dSAFER is set. You can expect the next release to remove a lot more.

If you want to use non-standard PostScript extensions, then you can't use 
SAFER, this doesn't seem unreasonable to me.


                     Ken