Prevent StackOverflow in ParseTrailer and fix UglyToad#1122

Author: BobLd

src/UglyToad.PdfPig.Tests/Integration/GithubIssuesTests.cs

@@ -7,6 +7,15 @@
 
     public class GithubIssuesTests
     {
+        [Fact]
+        public void Issue1122()
+        {
+            var path = IntegrationHelpers.GetSpecificTestDocumentPath("StackOverflow_Issue_1122.pdf");
+            
+            var ex = Assert.Throws<PdfDocumentFormatException>(() => PdfDocument.Open(path, new ParsingOptions() { UseLenientParsing = true }));
+            Assert.StartsWith("Reached maximum search depth while getting indirect reference.", ex.Message);
+        }
+
         [Fact]
         public void Issue1096()
         {

src/UglyToad.PdfPig.Tests/Integration/SpecificTestDocuments/StackOverflow_Issue_1122.pdf

@@ -625,7 +625,8 @@ private DictionaryToken GetStreamDictionary()
                 {
                     if (offset < 0)
                     {
-                        var result = GetObjectFromStream(lengthReference.Data, offset);
+                        ushort searchDepth = 0;
+                        var result = GetObjectFromStream(lengthReference.Data, offset, searchDepth);
 
                         if (!(result.Data is NumericToken streamLengthToken))
                         {
@@ -714,9 +715,23 @@ public void DeregisterCustomTokenizer(ITokenizer tokenizer)
 
             coreTokenScanner.DeregisterCustomTokenizer(tokenizer);
         }
-        
+
         public ObjectToken? Get(IndirectReference reference)
         {
+            ushort searchDepth = 0;
+            return Get(reference, searchDepth);
+        }
+
+        private ObjectToken? Get(IndirectReference reference, ushort searchDepth)
+        {
+            if (searchDepth > 1_000)
+            {
+                throw new PdfDocumentFormatException("Reached maximum search depth while getting indirect reference.");
+            }
+
+            searchDepth++;
+
+
             if (isDisposed)
             {
                 throw new ObjectDisposedException(nameof(PdfTokenScanner));
@@ -740,7 +755,7 @@ public void DeregisterCustomTokenizer(ITokenizer tokenizer)
             // Negative offsets refer to a stream with that number.
             if (offset < 0)
             {
-                var result = GetObjectFromStream(reference, offset);
+                var result = GetObjectFromStream(reference, offset, searchDepth);
 
                 return result;
             }
@@ -802,11 +817,11 @@ private ObjectToken BruteForceFileToFindReference(IndirectReference reference)
             }
         }
 
-        private ObjectToken GetObjectFromStream(IndirectReference reference, long offset)
+        private ObjectToken GetObjectFromStream(IndirectReference reference, long offset, ushort searchDepth)
         {
             var streamObjectNumber = offset * -1;
 
-            var streamObject = Get(new IndirectReference(streamObjectNumber, 0));
+            var streamObject = Get(new IndirectReference(streamObjectNumber, 0), searchDepth);
 
             if (!(streamObject?.Data is StreamToken stream))
             {