Throw an exeption in case the catalog cannot be referenced from the trailer

DEVSIX-6548

Author: ars18wrw

kernel/src/main/java/com/itextpdf/kernel/exceptions/KernelExceptionMessageConstant.java

@@ -129,6 +129,8 @@ public final class KernelExceptionMessageConstant {
             "Document outline is corrupted: some outline (PDF object: \"{0}\") lacks the required parent entry.";
     public static final String CORRUPTED_OUTLINE_NO_TITLE_ENTRY =
             "Document outline is corrupted: some outline (PDF object: \"{0}\") lacks the required title entry.";
+    public static final String CORRUPTED_ROOT_ENTRY_IN_TRAILER = "The trailer is corrupted: the catalog "
+            + "is corrupted or cannot be referenced from the file's trailer. The PDF cannot be opened.";
     public static final String DATA_HANDLER_COUNTER_HAS_BEEN_DISABLED = "Data handler counter has been disabled";
     public static final String DEFAULT_CRYPT_FILTER_NOT_FOUND_ENCRYPTION = "/DefaultCryptFilter not found "
             + "(encryption).";

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

@@ -1969,7 +1969,11 @@ protected void open(PdfVersion newPdfVersion) {
 
                 readDocumentIds();
 
-                catalog = new PdfCatalog((PdfDictionary) trailer.get(PdfName.Root, true));
+                PdfDictionary catalogDictionary = (PdfDictionary) trailer.get(PdfName.Root, true);
+                if (null == catalogDictionary) {
+                    throw new PdfException(KernelExceptionMessageConstant.CORRUPTED_ROOT_ENTRY_IN_TRAILER);
+                }
+                catalog = new PdfCatalog(catalogDictionary);
                 updatePdfVersionFromCatalog();
                 PdfStream xmpMetadataStream = catalog.getPdfObject().getAsStream(PdfName.Metadata);
                 if (xmpMetadataStream != null) {

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

@@ -1343,8 +1343,9 @@ protected void rebuildXref() throws IOException {
                 }
             }
         }
-        if (trailer == null)
+        if (trailer == null) {
             throw new PdfException(KernelExceptionMessageConstant.TRAILER_NOT_FOUND);
+        }
     }
 
     protected PdfNumber getXrefPrev(PdfObject prevObjectToCheck) {

kernel/src/test/java/com/itextpdf/kernel/pdf/PdfDocumentTest.java

@@ -45,6 +45,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.io.logs.IoLogMessageConstant;
 import com.itextpdf.io.image.ImageDataFactory;
 import com.itextpdf.io.source.DeflaterOutputStream;
+import com.itextpdf.kernel.exceptions.KernelExceptionMessageConstant;
 import com.itextpdf.kernel.exceptions.PdfException;
 import com.itextpdf.kernel.colors.ColorConstants;
 import com.itextpdf.kernel.geom.Rectangle;
@@ -595,6 +596,16 @@ public void mergedSiblingWidgetsRemovePageTest() throws IOException, Interrupted
                 DESTINATION_FOLDER));
     }
 
+    @Test
+    @LogMessages(messages = @LogMessage(messageTemplate =
+            IoLogMessageConstant.XREF_ERROR_WHILE_READING_TABLE_WILL_BE_REBUILT))
+    public void rootCannotBeReferenceFromTrailerTest() throws IOException {
+        String filename = SOURCE_FOLDER + "rootCannotBeReferenceFromTrailerTest.pdf";
+        PdfReader corruptedReader = new PdfReader(filename);
+        Exception e = Assert.assertThrows(PdfException.class, () -> new PdfDocument(corruptedReader));
+        Assert.assertEquals(KernelExceptionMessageConstant.CORRUPTED_ROOT_ENTRY_IN_TRAILER, e.getMessage());
+    }
+
     private static class IgnoreTagStructurePdfDocument extends PdfDocument {
 
         IgnoreTagStructurePdfDocument(PdfReader reader) {