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Hardware Control Flow Protection for Cyber-Physical Systems

Hardware Control Flow Protection for Cyber-Physical Systems. Stanley Bak University of Illinois at Urbana-Champaign. (Some slides from Joel Van Der Woude ). Problem . Cyber-physical systems are vulnerable to cyber attack. Attacks on critical infrastructure bring physical consequences.

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Hardware Control Flow Protection for Cyber-Physical Systems

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  1. Hardware Control Flow Protection for Cyber-Physical Systems Stanley Bak University of Illinois at Urbana-Champaign (Some slides from Joel Van Der Woude)

  2. Problem • Cyber-physical systems are vulnerable to cyber attack. • Attacks on critical infrastructure bring physical consequences.

  3. Typical Attacks • Remote code execution • Buffer overflows • Return into libc • String format vulnerabilities • Code injection • Network attacks • Denial of service • MITM • Social Engineering

  4. Secure System Simplex Architecture (S3A)

  5. What Side Channels? • Timing of Multiple Task Executions • Statistical Timing of Blocks of Code • I/O Access • Memory Access Patterns • Program Control Flow

  6. What Side Channels? • Timing of Multiple Task Executions • Statistical Timing of Blocks of Code • I/O Access • Memory Access • Program Control Flow

  7. Control Flow Monitoring • Control flow possible paths a program may take to execute • Enumerates jumps/calls/branches to create a “map” of possible “routes” through a program • Does not guarantee that the proper instructions were executed, only that blocks were executed in a plausible order

  8. Our Approach • Detect unexpected changes in control flow • Implement secure co-processor to limit overhead • Create tool to generate a control flow graph that can be read by the co-processor • Fail safely using a trusted Simplex controller • Restore complex controller and return control

  9. CFG Info • We watch for changes in “blocks” • Each block represents a set of instructions • Address of block • Number of instructions • Taken block • Not taken block

  10. Detection • If PC is outside the “block” • Is it the address of taken? • Is it the address of not taken? • If not we have detected a problem • Could be caused by an attacker overwriting a return address

  11. Current Issues • Large code • Multiple processes • Operating system (do we trust?) • Polymorphic code • More general purpose computing • How do we ensure that each program has a control flow graph?

  12. Conclusion • CPS Security • Hardware Control Flow Protection • Currently Implementing • Questions?

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