From: Chris Liddell <chris.liddell@artifex.com>
Date: Tue, 21 Aug 2018 19:17:51 +0000 (+0100)
Subject: Bug 699658: Fix handling of pre-SAFER opened files.

Bug 699658: Fix handling of pre-SAFER opened files.

Temp files opened for writing before SAFER is engaged are not subject to the
SAFER restrictions - that is handled by recording in a dictionary, and
checking that as part of the permissions checks.

By adding a custom error handler for invalidaccess, that allowed the filename
to be added to the dictionary (despite the attempted open throwing the error)
thus meaning subsequent accesses were erroneously permitted.

https://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=a054156d425b4dbdaaa9fda4b5f1182b27598c2b
---

diff -up a/Resource/Init/gs_init.ps.cve-2018-16539 b/Resource/Init/gs_init.ps
--- a/Resource/Init/gs_init.ps.cve-2018-16539	2018-11-14 16:34:23.268867657 +0100
+++ b/Resource/Init/gs_init.ps	2018-11-14 16:36:38.765552576 +0100
@@ -2015,6 +2015,19 @@ readonly def
             concatstrings concatstrings .generate_dir_list_templates
         } if
       ]
+      /PermitFileWriting [
+          currentuserparams /PermitFileWriting get aload pop
+          (TMPDIR) getenv not
+          {
+            (TEMP) getenv not
+            {
+              (TMP) getenv not
+              {
+                (/temp) (/tmp)
+              } if
+            } if
+          } if
+      ]
       /LockFilePermissions //true
     >> setuserparams
   }
@@ -2062,7 +2075,9 @@ readonly def
 % the file can be deleted later, even if SAFER is set.
 /.tempfile {
   .tempfile	% filename file
-  //SAFETY /tempfiles get 2 .argindex //true .forceput
+    //SAFETY /safe get not { % only add the filename if we're not yet safe
+    //SAFETY /tempfiles get 2 .argindex //true .forceput
+  } if
 } .bind executeonly odef
 
 % If we are running in SAFER mode, lock things down