From ee44aef8d08d8f745380277412ec8bb420648a7c Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Mon, 5 Mar 2018 14:25:17 -0500
Subject: Treat loop in xref tables as damage (fixes #192)

Prior to this fix, if there was a loop detected in following /Prev
pointers in xref streams/tables, it would cause qpdf to lose data.
Note that this condition causes many PDF readers to hang or fail.
---
 libqpdf/QPDF.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'libqpdf/QPDF.cc')

diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 9e30d6db..90e90813 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -532,7 +532,9 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
 	}
         if (visited.count(xref_offset) != 0)
         {
-            xref_offset = 0;
+            QTC::TC("qpdf", "QPDF xref loop");
+            throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(), "", 0,
+                          "loop detected following xref tables");
         }
     }
 
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