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Session 3: Software security and memory safety

Perform this exercise:
    https://exploit.education/protostar/stack-zero/

Perform this exercise:
    https://exploit.education/protostar/stack-one/

Perform this exercise:
    https://exploit.education/protostar/stack-three/

Research

  1. Installing Qemu
  2. –> problems with “no device to boot” > Problem solved
  3. –> problems to find the right repositery where the exercises are > Problem solved

  1. Understanding code manipulation

Questions asked

Exploit 1

Try until you get this message: “you have changed the ‘modified’ variable”

  • Explain what happened

  • Thanks to the get() function in the code, the variable was rewritten with 65 being 1 character more than expected. * How is it that providing an input in the line that reads “gets(buffer)” can change the value of the variable “modified”?

  • What does “Segmentation fault” mean? I* t’s a crash generated by an intent to access a memory zone that is not allowed
    Segmentation fault-Wikipedia

Exploit 2

Try until you get this message: “you have correctly got the variable to the right value”

  • Explain what happened.
  • What does “little endian” mean?
  • It’s the order how the octet are transmitted. Little endian begins with the least significant byte stored at the lowest memory address https://en.wikipedia.org/wiki/Endianness
  • Why didn’t you get “Segmentation fault”?

Exploit 3

  • How can you input hex values that don’t correspond to keyboard letters?
  • Try until you gest this message “code flow successfully changed”

Explain what happened