adding safeguards so input of oxffff glyph id isn't problematic (#256)

Author: galkahana

PDFWriter/TrueTypeDescendentFontWriter.cpp

@@ -24,6 +24,7 @@
 #include "TrueTypeEmbeddedFontWriter.h"
 #include "ObjectsContext.h"
 #include "IndirectObjectsReferenceRegistry.h"
+#include "Trace.h"
 
 using namespace PDFHummus;
 
@@ -55,14 +56,18 @@ EStatusCode TrueTypeDescendentFontWriter::WriteFont(	ObjectIDType inDecendentObj
 	// reset embedded font object ID (and flag...to whether it was actually embedded or not, which may 
 	// happen due to font embedding restrictions)
 	mEmbeddedFontFileObjectID = 0;
+	if(inEncodedGlyphs.back().first == 0xFFFF) {
+		TRACE_LOG("TrueTypeDescendentFontWriter::WriteFont, glyphs list includes a glyph id of 0xFFFF which is out of bounds for true type");
+		return eFailure;	
+	}
 	unsigned int subsetFontSize = inEncodedGlyphs.back().first + 1;
 
 	if (inEmbedFont)
 	{
 		TrueTypeEmbeddedFontWriter embeddedFontWriter;
 		EStatusCode status = embeddedFontWriter.WriteEmbeddedFont(inFontInfo, GetOrderedKeys(inEncodedGlyphs), inObjectsContext, mEmbeddedFontFileObjectID);
 
-		if (PDFHummus::eFailure == status)
+		if (eFailure == status)
 			return status;
 
 		// subset font size may have changed due to the inclusion of dependent glyphs

PDFWriter/TrueTypeEmbeddedFontWriter.cpp

@@ -154,7 +154,14 @@ EStatusCode TrueTypeEmbeddedFontWriter::CreateTrueTypeSubset(	FreeTypeFaceWrappe
 		// so - bottom line - the glyphs count will actually be 1 more than the maxium glyph index.
 		// and from here i'll just place the glyphs in their original indexes, and fill in the 
 		// vacant glyphs with empties.
-		mSubsetFontGlyphsCount = subsetGlyphIDs.back() + 1;
+		unsigned short maxGlyf = subsetGlyphIDs.back();
+		if(maxGlyf >= mTrueTypeInput.mMaxp.NumGlyphs)
+		{
+			TRACE_LOG2("TrueTypeEmbeddedFontWriter::CreateTrueTypeSubset, error, maximum requested glyph index %ld is larger than the maximum glyph index for this font which is %ld. ",maxGlyf,mTrueTypeInput.mMaxp.NumGlyphs-1);
+			status = eFailure;
+			break;
+		}
+		mSubsetFontGlyphsCount = maxGlyf + 1;
 
 		mFontFileStream.Assign(&outFontProgram);
 		mPrimitivesWriter.SetOpenTypeStream(&mFontFileStream);