forcepoint #27 check region bands loaded from stream for consistency

Change-Id: I92376b5fb4208c78fa25a94d4dd394256793161c
Reviewed-on: https://gerrit.libreoffice.org/51145Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>

vcl/inc/regionband.hxx

@@ -36,6 +36,7 @@ private:
     ImplRegionBand*             mpLastCheckedBand;
 
     void implReset();
+    SAL_WARN_UNUSED_RESULT bool CheckConsistency() const;
 
 public:
     RegionBand();
@@ -46,7 +47,7 @@ public:
 
     bool operator==( const RegionBand& rRegionBand ) const;
 
-    void load(SvStream& rIStrm);
+    SAL_WARN_UNUSED_RESULT bool load(SvStream& rIStrm);
     void save(SvStream& rIStrm) const;
 
     bool isSingleRectangle() const;

vcl/source/gdi/region.cxx

@@ -1586,7 +1586,7 @@ SvStream& ReadRegion(SvStream& rIStrm, vcl::Region& rRegion)
         default:
         {
             RegionBand* pNewRegionBand = new RegionBand();
-            pNewRegionBand->load(rIStrm);
+            bool bSuccess = pNewRegionBand->load(rIStrm);
             rRegion.mpRegionBand.reset(pNewRegionBand);
 
             if(aCompat.GetVersion() >= 2)
@@ -1603,6 +1603,12 @@ SvStream& ReadRegion(SvStream& rIStrm, vcl::Region& rRegion)
                 }
             }
 
+            if (!bSuccess)
+            {
+                SAL_WARN("vcl.gdi", "bad region band");
+                rRegion.SetNull();
+            }
+
             break;
         }
     }

vcl/source/gdi/regionband.cxx

@@ -190,7 +190,7 @@ bool RegionBand::operator==( const RegionBand& rRegionBand ) const
 
 enum StreamEntryType { STREAMENTRY_BANDHEADER, STREAMENTRY_SEPARATION, STREAMENTRY_END };
 
-void RegionBand::load(SvStream& rIStrm)
+bool RegionBand::load(SvStream& rIStrm)
 {
     // clear this instance data
     implReset();
@@ -203,14 +203,14 @@ void RegionBand::load(SvStream& rIStrm)
     rIStrm.ReadUInt16(nTmp16);
 
     if (STREAMENTRY_END == (StreamEntryType)nTmp16)
-        return;
+        return false;
 
     size_t nRecordsPossible = rIStrm.remainingSize() / (2*sizeof(sal_Int32));
     if (!nRecordsPossible)
     {
         OSL_ENSURE(false, "premature end of region stream" );
         implReset();
-        return;
+        return false;
     }
 
     do
@@ -259,13 +259,19 @@ void RegionBand::load(SvStream& rIStrm)
         {
             OSL_ENSURE(false, "premature end of region stream" );
             implReset();
-            return;
+            return false;
         }
 
         // get next header
         rIStrm.ReadUInt16( nTmp16 );
     }
     while (STREAMENTRY_END != (StreamEntryType)nTmp16 && rIStrm.good());
+    if (!CheckConsistency())
+    {
+        implReset();
+        return false;
+    }
+    return true;
 }
 
 void RegionBand::save(SvStream& rOStrm) const
@@ -1155,6 +1161,19 @@ bool RegionBand::Exclude(const RegionBand& rSource)
     return true;
 }
 
+bool RegionBand::CheckConsistency() const
+{
+    // look in the band list (don't test first band again!)
+    const ImplRegionBand* pBand = mpFirstBand->mpNextBand;
+    while (pBand)
+    {
+        if (!pBand->mpFirstSep)
+            return false;
+        pBand = pBand->mpNextBand;
+    }
+    return true;
+}
+
 tools::Rectangle RegionBand::GetBoundRect() const
 {