From 346810e02af17e2991255543e8ec1e99530237e9 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Tue, 19 Jun 2018 11:04:30 +0200
Subject: [PATCH] Add basic validation of the 'Root' dictionary in `XRef.parse`
 and try to recover when possible

Note that the `Catalog` constructor, and some of its methods, are already enforcing that the 'Root' dictionary is valid/well-formed. However, by doing additional validation already in `XRef.parse` there's a slightly larger chance that corrupt PDF files could be successfully parsed/rendered.
---
 src/core/obj.js | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/core/obj.js b/src/core/obj.js
index 620efbf4e..eee8eae11 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -877,8 +877,22 @@ var XRef = (function XRefClosure() {
                                                   this.pdfManager.password);
       }
 
-      // get the root dictionary (catalog) object
-      if (!(this.root = trailerDict.get('Root'))) {
+      // Get the root dictionary (catalog) object, and do some basic validation.
+      let root;
+      try {
+        root = trailerDict.get('Root');
+      } catch (ex) {
+        if (ex instanceof MissingDataException) {
+          throw ex;
+        }
+        warn(`XRef.parse - Invalid "Root" reference: "${ex}".`);
+      }
+      if (isDict(root) && root.has('Pages')) {
+        this.root = root;
+      } else {
+        if (!recoveryMode) {
+          throw new XRefParseException();
+        }
         throw new FormatError('Invalid root reference');
       }
     },