|
Flicker is a technique leveraging new features of CPUs
from AMD and Intel, including support for dynamic root
of trust, to execute application-specific code with an
extremely small TCB, while maintaining compatibility
with a legacy operating system.
Minimal TCB Code Execution
We propose an architecture that allows a Piece of
Application Logic (PAL) to execute in complete isolation
from other software while trusting only a tiny software
base that is orders of magnitude smaller than even
minimalist virtual machine monitors. Our technique also
enables more meaningful attestation than previous
proposals, since only measurements of the
security-sensitive portions of an application need to be
included. We achieve these guarantees by leveraging
hardware support provided by commodity processors from AMD
and Intel that are shipping today.
Prerequisites
To use Flicker, a PC platform supporting _skinit_ is
needed. The platform requires a processor supporting the
_skinit_ instruction, a v1.2
TPM, and a chipset which provides memory protection
for the Flicker code. The _skinit_ instruction is
available with newer AMD64
processors.
Frequently Asked Questions (FAQ)
- Q: Will Flicker run on my machine?
If it meets the Prerequisites above, Flicker _should_ run. However,
I have only tested it on the 3 machines that I have. The kmod
included with this version has only been tested with Linux kernel
2.6.24.
- Q: I don't have a Flicker-capable
machine. Can I still develop a Flicker module?
Yes, AMD's SimNow supports the _skinit_ instruction. However, there
will be no TPM support included. In fact, we have encountered
machines in the wild that will execute _skinit_ but do not include a
TPM. These can be useful for developing application-specific
functionality without requiring a reboot during a debug cycle.
- Q: I want to buy a machine to run
Flicker. What should I buy?
The machine we use the most is an HP dc5750.
- Q: Is Flicker bug-free?
Certainly not in this version. However, its extremely small size
suggests that a bug-free implementation may be attainable by buggy
human beings. :) Known problems include excessive I/O permissions to
ring 3 PAL code and excessive memory access by PAL segment
descriptors due to need to access the TPM from ring 3 without system
calls.
Revision History
- 2008.04.15. Initial public
release of Version 0.1. Contains Flicker
kernel module, barebones PAL with 250-line
TCB, and "Hello, world" PAL with debug
code. Please send email to Jonathan McCune
to request the code.
|
|
  Papers
McCune, Jonathan M., Bryan Parno, Adrian Perrig,
Michael K. Reiter, and Arvind Seshadri.
"Minimal TCB Code Execution (Extended Abstract)."
In Proceedings of
the IEEE Symposium on Security and
Privacy,
Oakland, California, May 2007.
[ PDF ]
McCune, Jonathan M., Bryan Parno, Adrian
Perrig, Michael K. Reiter, and Arvind
Seshadri. "How Low Can You Go?
Recommendations for Hardware-Supported
Minimal TCB Code Execution."
In Proceedings of
the ACM Conference on Architectural
Support for Programming Languages and
Operating Systems (ASPLOS'08),
Seattle, Washington,
March 1 - 5, 2008.
[ PDF
]
McCune, Jonathan M., Bryan Parno, Adrian
Perrig, Michael K. Reiter, and Hiroshi
Isozaki. "Flicker: An Execution Infrastructure
for TCB Minimization".
In Proceedings of
the ACM European Conference on Computer
Systems (EuroSys'08),
Glasgow, Scotland,
March 31 - April 4, 2008.
[ PDF
]
Presentation Slides
IEEE S&P 2007
[ PPT
]
ASPLOS 2008
[ PPT
]
EuroSys 2008
[ PPT
]
Extended version
[ PPT
]
Source Code
Version 0.1 [
please email Jon
]
|
Carnegie Mellon University 
