  Complexities that arise from implementation of object-oriented concepts in
C++ such as virtual dispatch and dynamic type casting have attracted the
attention of attackers and defenders alike.
  Binary-level defenses are dependent on full and precise recovery of class
inheritance tree of a given program.
  While current solutions focus on recovering single and multiple inheritances
from the binary, they are oblivious to virtual inheritance. Conventional wisdom
among binary-level defenses is that virtual inheritance is uncommon and/or
support for single and multiple inheritances provides implicit support for
virtual inheritance. In this paper, we show neither to be true.
  Specifically, (1) we present an efficient technique to detect virtual
inheritance in C++ binaries and show through a study that virtual inheritance
can be found in non-negligible number (more than 10\% on Linux and 12.5\% on
Windows) of real-world C++ programs including Mysql and libstdc++. (2) we show
that failure to handle virtual inheritance introduces both false positives and
false negatives in the hierarchy tree. These false positves and negatives
either introduce attack surface when the hierarchy recovered is used to enforce
CFI policies, or make the hierarchy difficult to understand when it is needed
for program understanding (e.g., during decompilation). (3) We present a
solution to recover virtual inheritance from COTS binaries. We recover a
maximum of 95\% and 95.5\% (GCC -O0) and a minimum of 77.5\% and 73.8\% (Clang
-O2) of virtual and intermediate bases respectively in the virtual inheritance
tree.
