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Binary Rewriting: Strengthening Defense Against Buffer Overflow Attacks

This presentation outlines the Binary Rewriting defense strategy against buffer overflow attacks, as discussed in the 2003 USENIX paper by Prasad & Chiueh. It covers methods of buffer overflows, open research problems, previous and related work, newness, significance, techniques, limitations, results, disassembly accuracy, performance overhead, and executable size overhead. The presentation explains two methods of overflow attacks, the classic return address hacks, and the overwriting of other pointers, while addressing open research problems and the significance of overflow protection in hardware. The Binary Rewriting technique involves altering assembly code to prevent vulnerabilities, storing return addresses in a separate stack, and ensuring secure program execution without requiring access to the source code, thus enhancing the security of even legacy applications.

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Binary Rewriting: Strengthening Defense Against Buffer Overflow Attacks

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  1. A Binary Rewriting Defense Against Buffer Overflow Attacks From USENIX 2003 Paper by Prasad & Chiueh Presentation by Bryan Pass

  2. Outline • Outline • Background • Buffer Overflow methods • Open Research Problems • Previous/Related Work • Binary Rewriting • Newness • Significance • Technique • Limitations • Results • Disassembly Accuracy • Performance Overhead • Executable Size Overhead

  3. Two Methods of Overflow • Classic Return Address hacks • Overflow a buffer and change the return address • Causes execution to jump to code inside the buffer when the function returns • Overwriting other pointers • Overflow a pointer used in another (potentially safe) copy operation • Insert code at any location in the executable • Usually used to overwrite the windows Global Offset Table

  4. Yes, it is a problem.

  5. Open Research Problems • Overflow safe compiler extensions • Why aren’t these more widespread and widely used? • Education • How many of you were taught how to avoid buffer overflows? • Overflow protection in hardware • Separate stack for return addresses • Interference with benign code? • Fixing legacy code • Binary Rewriting

  6. Previous/Related Work • “Canary” words • Languages & tools for compilers to use to identify potential overflows char *strcpy (char *s1, const char *s2) /*@requires maxSet(s1) >= maxRead(s2)@*/ /*@ensures maxRead(s1) == maxRead(s2) /\ result == s1@*/;

  7. A New Approach: Binary Rewriting • Alter assembly code of programs to prevent Return Address vulnerabilities • Uses compiled programs rather than their source code • Since source code is not required, this can help ensure the security of legacy applications/utilities and binaries provided by outside programmers

  8. Basic Method • Search a program’s assembly code for functions • Modify function prologs to store the proper return address in another area of memory (created by the binary rewriter) called the “return address stack” • Modify epilogs to use this “return address stack” to ensure they return to the proper address

  9. Architecture

  10. Issues with Disassembly • As it turns out, finding functions in disassembly is no simple task • Data in code regions • Variable Instruction size on x86 • Position independent code • Indirect branches • Functions without explicit CALLs • Hand written assembly • Cross function jumps

  11. Disassembly Methods • Recursive Traversal • Does not do well with complex code, especially GUIs • Linear Sweep • Hard to identify code segments • Misidentified segments can cause a “chain reaction” breaking most of the disassembly results • Combined approach with “Compiler independent heuristics”

  12. System Limitations • Intel Only • PE/Windows Only • Only protects return addresses • False negatives in function detection • False positives Fn1: // no ’interesting’ prologue : jne label : ret // no ’interesting’ epilogue Fn2: // ’interesting prologue’ : label: : ret // ’interesting’ epilogue • Hand-written assembly • Self modifying code • Small epilogs (int 3)

  13. Disassembly Accuracy

  14. Disassembly Accuracy

  15. Run-Time Overhead

  16. Executable Size Overhead

  17. References • A Binary Rewriting Defense against Stack based Buffer Overflow Attacks. Manish Prasad and Tzi-cker Chiueh.Proceedings of the General Track: 2003 USENIX Annual Technical Conference. June 9-14, 2003. http://www.usenix.org/publications/library/proceedings/usenix03/tech/prasad.html • Statically Detecting Buffer Overflow Vulnerabilities. Larochelle and Evans. http://lclint.cs.virginia.edu/usenix01.pdf • A First Step Towards Automated Detection of Buffer Overrun Vulnerabilities. Wagner, Foster, Brewer, Aiken. http://www.cs.berkeley.edu/~daw/papers/overruns-ndss00.pdf

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