Abstract
It is known that code interpreters (also known as Virtual Machine (VM)) may be used for binary code obfuscation. For instance, this is the underlying technique on which the packer VMProtect is based. Our long-term objective is to attack such obfuscations. Here, we concentrate on the identification of the implementation of the VM. It is quite standard to consider that a VM is implemented through a single fetch and a single dispatch mechanism, see for instance [SBP18]. But in practice, such a hypothesis is very restrictive. For instance, the standard implementation of python does not fulfill it. We give a generic model of virtual machine implementation with an experimental validation.
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Notes
- 1.
the standard application to run python programs. Those can be run via other programs such as pypy, but that latter one is not based on an interpreter.
- 2.
at least intentionally.
- 3.
For threaded interpreters, such as cpython when compiled with --with-computed-gotos flag.
- 4.
Here meaning that there is a syntax.
- 5.
Actually given by the Operating System.
- 6.
In practice, the source code of CPython, implements both forms of interpreters: https://github.com/python/cpython/blob/main/Python/ceval.c.
- 7.
For instance a virtual program such that for all instruction, the next instruction to be executed is positioned at the address of the current virtual instruction + \(\varDelta \).
- 8.
- 9.
In practice, once a first group of dispatches has been extracted using the following method, we use the assumption that the interpreter is within a function in order to add the dispatches that are followed by only one instruction.
- 10.
- 11.
Total detected - Correctly detected.
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Acknowledgments
The authors would like to thank the ORION program for its contribution to the funding of A. Ithayakumar’s research internship. This work has benefited from a government grant managed by the Agence Nationale de la Recherche with the reference ANR-20-SFRI-0009.
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Bonfante, G., Ithayakumar, A. (2023). Where is the Virtual Machine Within Cpython?. In: Jourdan, GV., Mounier, L., Adams, C., Sèdes, F., Garcia-Alfaro, J. (eds) Foundations and Practice of Security. FPS 2022. Lecture Notes in Computer Science, vol 13877. Springer, Cham. https://doi.org/10.1007/978-3-031-30122-3_11
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