This is a self-study lab of CMU university. This lab is a part of the course CS-15213.

Learning Objective:->

1. x86-64 assembly language
2. gdb

Answers available in answers.txt

Notes

1. use objdump -D (capital D) to disassemble all the text area. This also includes the area which may not hold the instructions. Some addresses which may not be visible through -d flag or in gdb are also visible using this command.
2. use gdb to go through the code. Useful commands : p,x, disas, break, s, info, until.

Hints

Level 1

ASCII string available within the address space.

Level 2

Numeric calculations

Level 3

Combines the concepts introduced in Level 1, Level 2, and little endianness. Not a unique answer.

Level 4

Similar to level 3. Another function call inside phase_4 besides sscanf. Not bothering now to find multiple answers.

Level 5

Multiple answers possible. Quite difficult. See the last byte of every character in the answer.

Level 6

Level 5 very easy relatively. The answer is permutation of the integers in a given range. This level forces you to learn gdb. Difficult to maintain state of registers and stack on the paper or in the mind. Better go through a tutorial or a cheatsheet of gdb.