From ffc847eaa55dd5ce239402c24522fac146665677 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 11 Oct 2019 20:39:02 +0200
Subject: [PATCH] Allow over-writing entries, in `XRef.indexObjects`, only when
 the generation number matches (issues 11230, 11139, 9552, 9129, 7303)

This patch is making me somewhat worried about future regressions, since it's certainly easy to imagine this completely breaking certain kinds of corrupt/edited PDF documents while fixing others.[1]

Obviously it passes all existing reference tests (and even improves one), however compared to many other patches there's no telling how much it could break.
The only reason that I'm even submitting this patch, is because of the number of open issues that it would address.

Generally speaking though, the best course of action would probably be if `XRef.indexObjects` was re-written to be much more robust (since it currently feels somewhat hand-wavy in parts). E.g. by actually checking/validating more of the objects before committing to them.

---
[1] Especially given that it's reverting part of PR 5910, however in the case of issue 5909 it seems that other (more recent) changes have actually made that PR redundant.
---
 src/core/obj.js               |  2 +-
 test/pdfs/issue11139.pdf.link |  1 +
 test/pdfs/issue11230.pdf.link |  1 +
 test/pdfs/issue7303.pdf.link  |  1 +
 test/pdfs/issue9129.pdf.link  |  1 +
 test/pdfs/issue9552.pdf.link  |  1 +
 test/test_manifest.json       | 43 +++++++++++++++++++++++++++++++++++
 7 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 test/pdfs/issue11139.pdf.link
 create mode 100644 test/pdfs/issue11230.pdf.link
 create mode 100644 test/pdfs/issue7303.pdf.link
 create mode 100644 test/pdfs/issue9129.pdf.link
 create mode 100644 test/pdfs/issue9552.pdf.link

diff --git a/src/core/obj.js b/src/core/obj.js
index e854e1e1f..1f3053db0 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -1415,7 +1415,7 @@ var XRef = (function XRefClosure() {
           position += skipUntil(buffer, position, startxrefBytes);
         } else if ((m = objRegExp.exec(token))) {
           const num = m[1] | 0, gen = m[2] | 0;
-          if (typeof this.entries[num] === 'undefined') {
+          if (!this.entries[num] || this.entries[num].gen === gen) {
             this.entries[num] = {
               offset: position - stream.start,
               gen,
diff --git a/test/pdfs/issue11139.pdf.link b/test/pdfs/issue11139.pdf.link
new file mode 100644
index 000000000..aa66e87a7
--- /dev/null
+++ b/test/pdfs/issue11139.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/3602024/FR.Cekada.SedesUnCum.pdf
diff --git a/test/pdfs/issue11230.pdf.link b/test/pdfs/issue11230.pdf.link
new file mode 100644
index 000000000..a45cc1a3c
--- /dev/null
+++ b/test/pdfs/issue11230.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/3717821/Y._Tsividis_A_First_Lab_in_Circuits_and_Electronics.pdf
diff --git a/test/pdfs/issue7303.pdf.link b/test/pdfs/issue7303.pdf.link
new file mode 100644
index 000000000..eae35adb6
--- /dev/null
+++ b/test/pdfs/issue7303.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/254710/ws_protectyourwork_e.pdf
diff --git a/test/pdfs/issue9129.pdf.link b/test/pdfs/issue9129.pdf.link
new file mode 100644
index 000000000..35b73744c
--- /dev/null
+++ b/test/pdfs/issue9129.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/3721643/issue9129.pdf
diff --git a/test/pdfs/issue9552.pdf.link b/test/pdfs/issue9552.pdf.link
new file mode 100644
index 000000000..a8e41b6dc
--- /dev/null
+++ b/test/pdfs/issue9552.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/3721640/issue9552.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 2fd3a1d93..d1c582360 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1378,14 +1378,40 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue7303",
+       "file": "pdfs/issue7303.pdf",
+       "md5": "3a5a4ab6755d6c3b0c490996b83d69d2",
+       "link": true,
+       "rounds": 1,
+       "lastPage": 2,
+       "type": "eq"
+    },
     {  "id": "issue7496",
        "file": "pdfs/issue7496.pdf",
        "md5": "b422981ae781166e75c0fb4c3634ed96",
        "link": true,
        "rounds": 1,
        "lastPage": 2,
+       "type": "eq",
+       "annotations": true
+    },
+    {  "id": "issue9129",
+       "file": "pdfs/issue9129.pdf",
+       "md5": "939ffc8d6d29b1d74e9d0f98b227b97f",
+       "link": true,
+       "rounds": 1,
+       "lastPage": 1,
        "type": "eq"
     },
+    {  "id": "issue9552",
+       "file": "pdfs/issue9552.pdf",
+       "md5": "7f80fd5b426926f88fd2a9fdc02cd3bd",
+       "link": true,
+       "rounds": 1,
+       "lastPage": 1,
+       "type": "eq",
+       "annotations": true
+    },
     {  "id": "issue10326",
        "file": "pdfs/issue10326.pdf",
        "md5": "015c13b09ef735ea1204f38992c60487",
@@ -1394,6 +1420,23 @@
        "lastPage": 1,
        "type": "eq"
     },
+    {  "id": "issue11139",
+       "file": "pdfs/issue11139.pdf",
+       "md5": "006dd4f4bb1878bc14a12072d81a4524",
+       "link": true,
+       "rounds": 1,
+       "lastPage": 1,
+       "type": "eq"
+    },
+    {  "id": "issue11230",
+       "file": "pdfs/issue11230.pdf",
+       "md5": "db0a1464d8f9f3ce079b52e0cacdccd3",
+       "link": true,
+       "rounds": 1,
+       "firstPage": 100,
+       "lastPage": 100,
+       "type": "eq"
+    },
     {  "id": "issue7544",
        "file": "pdfs/issue7544.pdf",
        "md5": "87e3a9fc7d6a6c1bd5b53af6926ce48e",