From cf7978d50716c63fc7836de0c1f8df624bafdad7 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 19 Jul 2021 17:45:10 +0200
Subject: [PATCH] XFA - Prevent breaking errors in `Binder`, when `searchNode`
 doesn't return data (issue 13756)

As can be seen in the code (see below), the `searchNode` helper function will return `null` in some cases and all of its call-sites should protect against that before attempting to access the returned data.
While only one of these changes were necessary to fix the breaking errors in issue 13756, in order to prevent future bugs I've added similar defensive code throughout this file.

 - https://github.com/mozilla/pdf.js/blob/07955fa1d31df62fd668a15f58cd40b29a82bd63/src/core/xfa/som.js#L169
 - https://github.com/mozilla/pdf.js/blob/07955fa1d31df62fd668a15f58cd40b29a82bd63/src/core/xfa/som.js#L239
 - https://github.com/mozilla/pdf.js/blob/07955fa1d31df62fd668a15f58cd40b29a82bd63/src/core/xfa/som.js#L254
---
 src/core/xfa/bind.js          | 20 ++++++++++++--------
 test/pdfs/issue13756.pdf.link |  1 +
 test/test_manifest.json       |  8 ++++++++
 3 files changed, 21 insertions(+), 8 deletions(-)
 create mode 100644 test/pdfs/issue13756.pdf.link

diff --git a/src/core/xfa/bind.js b/src/core/xfa/bind.js
index 76b171ca5..991be7060 100644
--- a/src/core/xfa/bind.js
+++ b/src/core/xfa/bind.js
@@ -198,34 +198,36 @@ class Binder {
         continue;
       }
 
-      const [node] = searchNode(
+      const nodes = searchNode(
         this.root,
         dataNode,
         ref,
         false /* = dotDotAllowed */,
         false /* = useCache */
       );
-      if (!node) {
+      if (!nodes) {
         warn(`XFA - Invalid reference: ${ref}.`);
         continue;
       }
+      const [node] = nodes;
 
       if (!node[$isDescendent](this.data)) {
         warn(`XFA - Invalid node: must be a data node.`);
         continue;
       }
 
-      const [targetNode] = searchNode(
+      const targetNodes = searchNode(
         this.root,
         formNode,
         target,
         false /* = dotDotAllowed */,
         false /* = useCache */
       );
-      if (!targetNode) {
+      if (!targetNodes) {
         warn(`XFA - Invalid target: ${target}.`);
         continue;
       }
+      const [targetNode] = targetNodes;
 
       if (!targetNode[$isDescendent](formNode)) {
         warn(`XFA - Invalid target: must be a property or subproperty.`);
@@ -337,34 +339,36 @@ class Binder {
           continue;
         }
 
-        const [labelNode] = searchNode(
+        const labelNodes = searchNode(
           this.root,
           node,
           labelRef,
           true /* = dotDotAllowed */,
           false /* = useCache */
         );
-        if (!labelNode) {
+        if (!labelNodes) {
           warn(`XFA - Invalid label: ${labelRef}.`);
           continue;
         }
+        const [labelNode] = labelNodes;
 
         if (!labelNode[$isDescendent](this.datasets)) {
           warn(`XFA - Invalid label: must be a datasets child.`);
           continue;
         }
 
-        const [valueNode] = searchNode(
+        const valueNodes = searchNode(
           this.root,
           node,
           valueRef,
           true /* = dotDotAllowed */,
           false /* = useCache */
         );
-        if (!valueNode) {
+        if (!valueNodes) {
           warn(`XFA - Invalid value: ${valueRef}.`);
           continue;
         }
+        const [valueNode] = valueNodes;
 
         if (!valueNode[$isDescendent](this.datasets)) {
           warn(`XFA - Invalid value: must be a datasets child.`);
diff --git a/test/pdfs/issue13756.pdf.link b/test/pdfs/issue13756.pdf.link
new file mode 100644
index 000000000..12a75cb4c
--- /dev/null
+++ b/test/pdfs/issue13756.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/6842290/Attestation_d.occupation.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 71a92f33e..445c97dab 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1347,6 +1347,14 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue13756",
+       "file": "pdfs/issue13756.pdf",
+       "md5": "67040c6df3b5039fcbc81bf63b7c7f98",
+       "link": true,
+       "rounds": 1,
+       "enableXfa": true,
+       "type": "eq"
+    },
     {  "id": "issue9262",
        "file": "pdfs/issue9262_reduced.pdf",
        "md5": "5347ce2d7b3866625c22e115fd90e0de",