check for offsets exceeding file length for xref parsing #293

src/UglyToad.PdfPig/Parser/FileStructure/CrossReferenceObjectOffsetValidator.cs

@@ -23,6 +23,8 @@
             {
                 return true;
             }
+
+            var builderOffsets = new Dictionary<IndirectReference, long>();
             
             var bruteForceOffsets = BruteForceSearcher.GetObjectLocations(bytes);
             if (bruteForceOffsets.Count > 0)
@@ -77,10 +79,11 @@
 
                     foreach (var item in bruteForceOffsets)
                     {
-                        //xrefOffset[item.Key] = item.Value;
+                        builderOffsets[item.Key] = item.Value;
                     }
-
                 }
+
+                actualOffsets = builderOffsets;
             }
 
             return false;
@@ -131,6 +134,12 @@
 
             try
             {
+                if (offset >= bytes.Length)
+                {
+                    bytes.Seek(originOffset);
+                    return false;
+                }
+
                 bytes.Seek(offset);
 
                 if (ReadHelper.IsWhitespace(bytes.CurrentByte))

src/UglyToad.PdfPig/Parser/FileStructure/XrefOffsetValidator.cs

@@ -4,7 +4,6 @@
     using System.Collections.Generic;
     using Core;
     using Logging;
-    using Parts;
     using Tokenization.Scanner;
     using Tokens;
 
@@ -30,6 +29,11 @@
                 return startXRefOffset;
             }
 
+            if (startXRefOffset >= inputBytes.Length)
+            {
+                return CalculateXRefFixedOffset(startXRefOffset, scanner, inputBytes);
+            }
+
             scanner.Seek(startXRefOffset);
 
             scanner.MoveNext();