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

DEVSIX-6548

Autoported commit.
Original commit hash: [c26866f30]

Author: ars18wrw

itext.tests/itext.kernel.tests/itext/kernel/pdf/PdfDocumentTest.cs

@@ -501,6 +501,15 @@ public virtual void MergedSiblingWidgetsRemovePageTest() {
                 , DESTINATION_FOLDER));
         }
 
+        [NUnit.Framework.Test]
+        [LogMessage(iText.IO.Logs.IoLogMessageConstant.XREF_ERROR_WHILE_READING_TABLE_WILL_BE_REBUILT)]
+        public virtual void RootCannotBeReferenceFromTrailerTest() {
+            String filename = SOURCE_FOLDER + "rootCannotBeReferenceFromTrailerTest.pdf";
+            PdfReader corruptedReader = new PdfReader(filename);
+            Exception e = NUnit.Framework.Assert.Catch(typeof(PdfException), () => new PdfDocument(corruptedReader));
+            NUnit.Framework.Assert.AreEqual(KernelExceptionMessageConstant.CORRUPTED_ROOT_ENTRY_IN_TRAILER, e.Message);
+        }
+
         private class IgnoreTagStructurePdfDocument : PdfDocument {
             internal IgnoreTagStructurePdfDocument(PdfReader reader)
                 : base(reader) {

itext.tests/itext.kernel.tests/resources/itext/kernel/pdf/PdfDocumentTest/rootCannotBeReferenceFromTrailerTest.pdf

@@ -169,6 +169,8 @@ public const String CONTENT_STREAM_MUST_NOT_INVOKE_OPERATORS_THAT_SPECIFY_COLORS
 
         public const String CORRUPTED_OUTLINE_NO_TITLE_ENTRY = "Document outline is corrupted: some outline (PDF object: \"{0}\") lacks the required title entry.";
 
+        public const 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 const String DATA_HANDLER_COUNTER_HAS_BEEN_DISABLED = "Data handler counter has been disabled";
 
         public const String DEFAULT_CRYPT_FILTER_NOT_FOUND_ENCRYPTION = "/DefaultCryptFilter not found " + "(encryption).";

itext/itext.kernel/itext/kernel/exceptions/KernelExceptionMessageConstant.cs

@@ -2016,7 +2016,11 @@ protected internal virtual void Open(PdfVersion newPdfVersion) {
                     pdfVersion = reader.headerPdfVersion;
                     trailer = new PdfDictionary(reader.trailer);
                     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) {

itext/itext.kernel/itext/kernel/pdf/PdfDocument.cs

@@ -1 +1 @@
-1953b3f0519c059fb438066102e090c396a051a4
+c26866f3001f1a3604045fe2eb063e5f5d4e9ebb