The quickest way I know to find out the bytes at 0x804a040 is to load theīinary into my debugger radare2 and just print it out.ġ 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 On the binary, it would have worked in the previous challenge, but not this oneīecause each character in a wchar_t string is 32-bits long with the most significantīits zeroed out, and terminated by a a 32-bit 0x0000 value. The trick to this challenge, is that if we were simply to run the strings program The location on the stack that it wrote our input to. The arguments to wcscmp are 0x804a040, which I’m guessing is in the initializedĭata section, and is the secret password, and 0xff82eb4c which ltrace shows is Top of memory and grows upwards from 0xffffffff. On Linux most of the time the code and data sections get loaded around the addressĠx08040000, and local variables are stored in the stack, which begins at the The prototype int wcscmp (const wchar_t* wcs1, const wchar_t* wcs2) It compares So the difference here is the password is being compared with wcscmp, which has We start out simple, and so I start with my simplest techniques. In order to discover the password, and these range from simple to tedious andĭifficult as the creator of the crackme piles on layers of obfuscation, misdirection,Įncryption, and anti-debugging techniques to stop you, not to mention you needĪ good handle on assembly and keeping track of what is in various memory locations “Crackmes” are essentially a compiled binary without source code, which asks youįor a password or key, you enter the wrong password you lose, you enter the right Or reverse engineer crackmes, so I decided to describe my process for solving those

So I like to take some of my free time and play hacker wargames like , Language, you mustn’t be able to manage memory, or handle programming in languages If you use Ruby you must be “only” a web programmer, if you use a garbage collected Lately I’ve been getting the feeling that a programmer can get judgedĪnd immediately pigeon holed based on using a language a lot at work. Many aspects of this language, and it’s usually the main language that I use at workĪs well. You may have noticed that I like to program many things in Ruby.