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Usage of GDB

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As the first class of system security, We studied on usage of GDB. After finishing the description about GDB, We had the time of experimentation.

For the practice, you can join and download the file including two flags at http://cafe.naver.com/artofthings/2063.

Publicado en: Ingeniería
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Usage of GDB

  1. 1. Introduction Running GDB Experimentation Usage of GDB th!nkh@ck-hackartist cafe.thinkhack.org December 19, 2014
  2. 2. Introduction Running GDB Experimentation 1 Introduction Introduction to GDB 2 Running GDB Starting GDB Listing Codes Debugging Listing Functions and Variables Breaking Points Monitoring Registers Watching Values Dumping Stack 3 Experimentation Analysing a Program Solving the Program
  3. 3. Introduction Running GDB Experimentation Introduction to GDB Introduction to GDB What is GDB? GNU Project debugger Supports for Ada, C, C++, Objective-C, Pascal and many other languages The latest version is 7.8.1 of GDB Mac OS X uses modification version of GDB Features of GDB Supports for various architectures (Such as ARM, MIPS, i386, etc.) Supports for instructions; SSE, AVX, AVX2 MPX, etc. Various instructions is supported on various architectures Including all the functionalities of GUI debuggers
  4. 4. Introduction Running GDB Experimentation Starting GDB Starting GDB Debugging a program without any parameters gdb [options] filename gdb learn-gdb Debugging a program with parameters gdb [options] –args filename arg1 arg2 ... gdb –args learn-gdb -r
  5. 5. Introduction Running GDB Experimentation Listing Codes Listing Codes Listing All the codes (gdb) list {line number} (gdb) list 1 Listing a specific function (gdb) list {function name} (gdb) list main
  6. 6. Introduction Running GDB Experimentation Debugging Debugging Starting a program (gdb) run (gdb) r Debugging a program (gdb) continue (gdb) next (gdb) nexti (gdb) step (gdb) stepi
  7. 7. Introduction Running GDB Experimentation Listing Functions and Variables Listing Functions and Variables Listing all functions (gdb) info functions (gdb) i func Disassembling a function (gdb) disass {function name} (gdb) disass main Listing global/static variables (gdb) info variables (gdb) i var
  8. 8. Introduction Running GDB Experimentation Breaking Points Breaking Points Breaking a function (gdb) break {function name} (gbd) b main Breaking a specific address (gdb) break *{address} (gdb) b *0x100000af0 Listing breakpoints (gdb) info breakpoints (gdb) i b
  9. 9. Introduction Running GDB Experimentation Monitoring Registers Monitoring Registers Seeing all registers (gdb) info registers (gdb) i r Seeing a specific register (gdb) info register ${a specific register} (gdb) i r $rax
  10. 10. Introduction Running GDB Experimentation Watching Values Watching Values Watching variable (gdb) watch {variable name} (gdb) watch flag (gdb) continue (or other debugging command)
  11. 11. Introduction Running GDB Experimentation Dumping Stack Dumping Stack Dumping stack We can use “x” command with some parameter. In parameters, count of memeory we want to see, printed radix and unit will be required. Usage of “x” (gdb) x/{count}{radix}{unit} {address} (gdb) x/4xw
  12. 12. Introduction Running GDB Experimentation Analysing a Program Analysing a Program Problem Find flag string in the binary files http://wctf.thinkhack.org Hints The binary file performs part of AES encryption The total of rounds consists of 10 rounds There are three key functions.
  13. 13. Introduction Running GDB Experimentation Solving the Program Solving the Program Demostration

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