Added a way to deal with incorrectly constructed XREF tables.

 When an XREF table starts from any other number than 0, iText would add the 0000 65535 entry twice. A fix has been added that circumvents this bizarre entry.

 SUP-1557

Author: michaeldemey

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfReader.java

@@ -54,8 +54,6 @@ This file is part of the iText (R) project.
 import com.itextpdf.kernel.PdfException;
 import com.itextpdf.kernel.pdf.filters.FilterHandlers;
 import com.itextpdf.kernel.pdf.filters.IFilterHandler;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayInputStream;
 import java.io.Closeable;
@@ -65,6 +63,9 @@ This file is part of the iText (R) project.
 import java.text.MessageFormat;
 import java.util.Map;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 public class PdfReader implements Closeable, Serializable {
 
     private static final long serialVersionUID = -3584187443691964939L;
@@ -750,6 +751,22 @@ protected PdfDictionary readXrefSection() throws IOException {
                 tokens.nextValidToken();
                 int gen = tokens.getIntValue();
                 tokens.nextValidToken();
+                if ( pos == 0L && gen == 65535 && num == 1 ) {
+                    // Very rarely can an XREF have an incorrect start number. (SUP-1557)
+                    // e.g.
+                    // xref
+                    // 1 13
+                    // 0000000000 65535 f
+                    // 0000000009 00000 n
+                    // 0000215136 00000 n
+                    // [...]
+                    // Because of how iText reads (and initializes) the XREF, this will lead to the XREF having two 0000 65535 entries.
+                    // This throws off the parsing and other operations you'd like to perform.
+                    // To fix this we reset our index and decrease the limit when we've encountered the magic entry at position 1.
+                    num = 0;
+                    end--;
+                    continue;
+                }
                 PdfIndirectReference reference = xref.get(num);
                 if (reference == null) {
                     reference = new PdfIndirectReference(pdfDocument, num, gen, pos);