A Framework For Trusted Instruction Execution Via Basic Block Signature Verification

1. A Framework For Trusted Instruction ExecutionVia Basic Block Signature Verification Milena Milenković, Aleksandar Milenković, and Emil Jovanov Electrical and Computer Engineering Dept. The University of Alabama in Huntsville {milenkm|milenka|jovanov}@ece.uah.edu

2. Outline • Introduction • Related Work • Trusted Instruction Execution Framework • The Framework Potential • Conclusion

3. Introduction • Most of today’s computers connected to Internet security is a critical issue • Even more so in the future • One of the major security problems: the execution of the unauthorized code • A lot of applications may be vulnerable • Attack examples: • buffer overflow (heap, stack) • format string attack

4. Introduction • We propose a processor architecture that • will allow execution of the trusted instructions only • will not significantly increase the program execution time

5. Related Work • Two categories: • Static source code analysis • Dynamic detection/prevention • Static code analysis: false alarms • Dynamic • Monitoring program behavior (system calls, performance monitoring registers) • Compilers, safe language dialects • Secure Program Execution Framework (SPEF) • Tag data from “spurious” channels • Split stack for data/addresses, or secure stack

6. Trusted Instruction Execution • Atomic code unit protected by its signature: a basic block • Verify all basic blocks? • Cache memory is safe:verify the signature of basic blocks that generated a cache miss • Text memory write protected:check only last basic block in a stream

7. Code BBST_M Heap Stack Architecture For Trusted Computing BBST – Basic Block Signature Table BBST_M – Basic Block Signature Table (Memory) BBSVU – Basic Block Signature Verification Unit MMU L1D Datapath L1I FPUs IF BBST Control BBSVU

8. Phases of the Security Mechanism • Compilation • Compiler generates a list of basic blocks • Secure program installation • Signature table (BBST_M) is generated, encrypted and appended to the program binary • Program loading in the memory • BBST_M is decrypted, loaded in the memory • Program execution • Signature of each last basic block in a streamthat generated a cache miss is verified • If no match, a trap to OS – kill process & audit

9. Signature generation • MISR (Multiple input signature register) • Linear feedback coefficients – based on the processor secret key

10. Program Execution

11. The Framework Potential • 32-bit MISR • I-cache: 4 ways, 128 sets, 64B line • BBST: 4 ways, 4B line, 128/256 sets • LRU replacement • Traces of SPEC CPU2000 benchmarks for Alpha architecture • F2B, M2B segments • Measure: BBST misses per 1 M instructions

12. The Framework Potential

13. The Framework Potential

14. Conclusion • Proposed a framework for trusted instruction execution,evaluated potential • Promises to be faster than SPEF, with additional hardware resources and BBST appended to program binary • Future work: • different BBST organizations and sizes • detailed performance evaluation • an alternative implementation:signature embedded in the code