From cd1b1cacadac2479e291efe611979bdc1b3bdb19 Mon Sep 17 00:00:00 2001
From: Ken Sharp <ken.sharp@artifex.com>
Date: Wed, 21 Aug 2019 10:10:51 +0100
Subject: [PATCH] PDF interpreter - review .forceput security

Bug #701450 "Safer Mode Bypass by .forceput Exposure in .pdfexectoken"

By abusing the error handler it was possible to get the PDFDEBUG portion
of .pdfexectoken, which uses .forceput left readable.

Add an executeonly appropriately to make sure that clause isn't readable
no mstter what.

Review all the uses of .forceput searching for similar cases, add
executeonly as required to secure those. All cases in the PostScript
support files seem to be covered already.
---
 Resource/Init/pdf_base.ps |  2 +-
 Resource/Init/pdf_draw.ps | 14 +++++++-------
 Resource/Init/pdf_font.ps | 29 ++++++++++++++++-------------
 Resource/Init/pdf_main.ps |  6 +++---
 Resource/Init/pdf_ops.ps  | 11 ++++++-----
 5 files changed, 33 insertions(+), 29 deletions(-)

diff --git a/Resource/Init/pdf_base.ps b/Resource/Init/pdf_base.ps
index 2e28cdd..02503ee 100644
--- a/Resource/Init/pdf_base.ps
+++ b/Resource/Init/pdf_base.ps
@@ -157,7 +157,7 @@ currentdict /num-chars-dict .undef
     {
       dup ==only () = flush
     } ifelse % PDFSTEP
-  } if % PDFDEBUG
+  } executeonly if % PDFDEBUG
   2 copy .knownget {
     exch pop exch pop exch pop exec
   } {
diff --git a/Resource/Init/pdf_draw.ps b/Resource/Init/pdf_draw.ps
index 11eb485..fe3fc56 100644
--- a/Resource/Init/pdf_draw.ps
+++ b/Resource/Init/pdf_draw.ps
@@ -501,8 +501,8 @@ end
       (        Output may be incorrect.\n) pdfformaterror
       //pdfdict /.gs_warning_issued //true .forceput
       PDFSTOPONERROR { /gs /undefined signalerror } if
-    } if
-  }
+    } executeonly if
+  } executeonly
   ifelse
 } bind executeonly def
 
@@ -1152,7 +1152,7 @@ currentdict end readonly def
           .setglobal
           pdfformaterror
         } executeonly ifelse
-      }
+      } executeonly
       {
         currentglobal //pdfdict gcheck .setglobal
         //pdfdict /.Qqwarning_issued //true .forceput
@@ -1160,8 +1160,8 @@ currentdict end readonly def
         pdfformaterror
       } executeonly ifelse
       end
-    } ifelse
-  } loop
+    } executeonly ifelse
+  } executeonly loop
   {
     (\n   **** Error: File has unbalanced q/Q operators \(too many q's\)\n               Output may be incorrect.\n)
     //pdfdict /.Qqwarning_issued .knownget
@@ -1175,14 +1175,14 @@ currentdict end readonly def
         .setglobal
         pdfformaterror
       } executeonly ifelse
-    }
+    } executeonly
     {
       currentglobal //pdfdict gcheck .setglobal
       //pdfdict /.Qqwarning_issued //true .forceput
       .setglobal
       pdfformaterror
     } executeonly ifelse
-  } if
+  } executeonly if
   pop
 
   % restore pdfemptycount
diff --git a/Resource/Init/pdf_font.ps b/Resource/Init/pdf_font.ps
index da07da5..81b7af1 100644
--- a/Resource/Init/pdf_font.ps
+++ b/Resource/Init/pdf_font.ps
@@ -638,7 +638,7 @@ currentdict end readonly def
                   currentglobal 2 index dup gcheck setglobal
                   /FontInfo 5 dict dup 5 1 roll .forceput
                   setglobal
-                } if
+                } executeonly if
                 dup /GlyphNames2Unicode .knownget not {
                   //true                        % No existing G2U, make one
                 } {
@@ -668,10 +668,12 @@ currentdict end readonly def
                 pop                                     % font-res font-dict encoding|null font-info
                 pop                                     % font-res font-dict encoding|null
                 //false                                 % We built a GlyphNames2Unicode table, don't need to process further
-              }{
+              } executeonly
+              {
                 //true                                  % name is not Identity-V or H, fail by falling through
               }ifelse
-          } {
+          } executeonly
+          {
             //true
           } ifelse                                      % not a name, try as a dictionary (as specified)
 
@@ -759,9 +761,9 @@ currentdict end readonly def
           PDFDEBUG {
             (.processToUnicode end) =
           } if
-        } if
-      } if
-    } stopped
+        } executeonly if
+      } executeonly if
+    } executeonly stopped
     {
       .dstackdepth 1 countdictstack 1 sub
       {pop end} for
@@ -1298,19 +1300,20 @@ currentdict /eexec_pdf_param_dict .undef
                 //pdfdict /.Qqwarning_issued //true .forceput
               } executeonly if
               Q
-            } repeat
+            } executeonly repeat
             Q
-          } PDFfile fileposition 2 .execn % Keep pdfcount valid.
+          } executeonly PDFfile fileposition 2 .execn % Keep pdfcount valid.
           PDFfile exch setfileposition
-        } ifelse
-      } {
+        } executeonly ifelse
+      } executeonly
+      {
         % PDF Type 3 fonts don't use .notdef
         % d1 implementation adjusts the width as needed
         0 0 0 0 0 0
         pdfopdict /d1 get exec
       } ifelse
       end end
-    } bdef
+    } executeonly bdef
     dup currentdict Encoding .processToUnicode
     currentdict end .completefont exch pop
 } bind executeonly odef
@@ -2124,9 +2127,9 @@ currentdict /CMap_read_dict undef
           (Will continue, but content may be missing.) = flush
         } ifelse
       } if
-    } if
+    } executeonly if
     /findresource cvx /undefined signalerror
-  } loop
+  } executeonly loop
 } bind executeonly odef
 
 /buildCIDType0 {	% <CIDFontType0-font-resource> buildCIDType0 <font>
diff --git a/Resource/Init/pdf_main.ps b/Resource/Init/pdf_main.ps
index 00d7e36..7690bae 100644
--- a/Resource/Init/pdf_main.ps
+++ b/Resource/Init/pdf_main.ps
@@ -2771,15 +2771,15 @@ currentdict /PDF2PS_matrix_key undef
           .setglobal
           pdfformaterror
         } executeonly ifelse
-      }
+      } executeonly
       {
         currentglobal //pdfdict gcheck .setglobal
         //pdfdict /.Qqwarning_issued //true .forceput
         .setglobal
         pdfformaterror
       } executeonly ifelse
-    } if
-  } if
+    } executeonly if
+  } executeonly if
   pop
   count PDFexecstackcount sub { pop } repeat
   (after exec) VMDEBUG
diff --git a/Resource/Init/pdf_ops.ps b/Resource/Init/pdf_ops.ps
index a15c8c6..d594035 100644
--- a/Resource/Init/pdf_ops.ps
+++ b/Resource/Init/pdf_ops.ps
@@ -192,14 +192,14 @@ currentdict /gput_always_allow .undef
         .setglobal
         pdfformaterror
       } executeonly ifelse
-    }
+    } executeonly
     {
       currentglobal //pdfdict gcheck .setglobal
       //pdfdict /.Qqwarning_issued //true .forceput
       .setglobal
       pdfformaterror
     } executeonly ifelse
-  } if
+  } executeonly if
 } bind executeonly odef
 
 % Save PDF gstate
@@ -446,11 +446,12 @@ currentdict /gput_always_allow .undef
   dup type /booleantype eq {
     .currentSMask type /dicttype eq {
       .currentSMask /Processed 2 index .forceput
+    } executeonly
+    {
+      .setSMask
+    }ifelse
   } executeonly
   {
-      .setSMask
-  }ifelse
-  }{
   .setSMask
   }ifelse
 
-- 
1.8.3.1

