Security: fix potential multiplication overflow

Better sanity check inputs to bit stream reader

2 files changed, 7 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 449f5f93..c8dbafa4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2013-10-05  Jay Berkenbilt  <ejb@ql.org>
 
+	* Security fix: perform additional argument sanity checks when
+	reading bit streams.
+
 	* Security fix: in QUtil::toUTF8, change bounds checking to avoid
 	having a pointer point temporarily outside the bounds of an
 	array.  Some compiler optimizations could have made the original
diff --git a/libqpdf/BitStream.cc b/libqpdf/BitStream.cc
index eb511f72..14eae55d 100644
--- a/libqpdf/BitStream.cc
+++ b/libqpdf/BitStream.cc
@@ -16,6 +16,10 @@ BitStream::reset()
 {
     p = start;
     bit_offset = 7;
+    if (static_cast<unsigned int>(nbytes) > static_cast<unsigned int>(-1) / 8)
+    {
+	throw std::runtime_error("array too large for bitstream");
+    }
     bits_available = 8 * nbytes;
 }