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The CTF Recipes
  • Introduction
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    • Introduction
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      • XOR
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      • Index of coincidence
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      • Well known algorithms
        • 🔴Scytale
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    • Symmetric Cryptography
      • AES
        • Block Encryption procedure
          • Byte Substitution
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          • Key Expansion / Key Schedule
        • Mode of Operation
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            • Block shuffling
              • Challenge example
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              • Challenge example
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              • Challenge example
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              • Challenge example
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            • Encrypt to Uncrypt
  • 🛠️Pwn
    • General knowledge
      • STACK
        • Variables storage
        • Stack frame
      • PLT and GOT
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        • HEAP operations
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    • Architectures
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      • aarch64
        • Registers
        • Instruction set
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      • mips32
        • Registers
        • Instruction set
        • Calling convention
      • mips64
        • Registers
        • Instruction set
        • Calling convention
      • x86 / x64
        • Registers
        • Instruction set
        • Calling convention
    • Stack exploitation
      • Stack Buffer Overflow
        • Dangerous functions
          • gets
          • memcpy
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          • strcat
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        • Basics
          • Challenge example
        • Instruction pointer Overwrite
          • Challenge example
        • De Bruijn Sequences
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          • Challenge example
      • Format string
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        • Placeholder
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          • Challenge example
        • Data modification
          • Challenge example
      • Arbitrary code execution
        • Shellcode
        • ret2reg
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          • Ret2plt
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          • GOT Overwrite
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          • Ret2csu
          • Return Oriented Programming - ROP
          • Sigreturn Oriented Programming - SROP
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            • Challenge example
          • 🔴Call Oriented Programming - COP
          • 🔴Jump Oriented Programming - JOP
          • One gadget
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    • 🛠️Heap exploitation
      • Heap overflow
        • Challenge example
      • Use after free
        • Challenge example
      • 🛠️Double free
      • 🔴Unlink exploit
    • Protections
      • Stack Canaries
      • No eXecute
      • PIE
      • ASLR
      • RELRO
    • Integer overflow
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On this page
  1. Pwn
  2. Stack exploitation
  3. Stack Buffer Overflow

Instruction pointer Overwrite

Arbitrary Instruction redirection

How it works ?

As explained in the "STACK" part, at the call of the function the process store the value of the instruction pointer onto the stack. Thus, there is always the saved instruction pointer at the end of a function stack frame.

   address     |   values
---------------+------------------------------------------------------------------
               |   +---------------- Function stack frame -------------------+
               |   | +------------- stack vars -------------+ +-saved ebp -+ |
   0xffffd264  |   | | 0x00000000   0x00000000   0x00000000 | | 0xffffd298 | | 
               |   | +--------------------------------------+ +------------+ |
               |   +---------------------------------------------------------+
               |   +-------------------- main stack frame -------------------+
               |   | +-saved eip -+ +---- function params ---+               |
   0xffffd274: |   | | 0x565561dd | | 0x00000001  0x00000002 |	0x00000001   |
               |   | +------------+ +------------------------+               |

If a buffer overflow occur within the function, it might be possible to overwrite the saved registers

   address     |   values
---------------+------------------------------------------------------------------
               |   +---------------- Function stack frame -------------------+
               |   | +------------- stack vars -------------+ +-saved ebp -+ |
   0xffffd264  |   | | 0x41414141   0x41414141   0x41414141 | | 0x41414141 | | 
               |   | +--------------------------------------+ +------------+ |
               |   +---------------------------------------------------------+
               |   +-------------------- main stack frame -------------------+
               |   | +-saved eip -+ +---- function params ---+               |
   0xffffd274: |   | | 0x41414141 | | 0x00000001  0x00000002 |	0x00000001   |
               |   | +------------+ +------------------------+               |

In this example, a buffer overflow occur at the variable stored at 0xffffd264 . 20 'A' have been send to entirely overwrite the saved EIP register

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Last updated 8 months ago

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