WhiteHat and the Exploit Factory

Every single program uses string to store file paths, labels, prompt text. But not everyone knows that plain text strings can be easily obtained with a debugger. Some programs even store passwords or any other important information in plain text strings. In this blog post I will go over the most popular ways of hiding/encrypting strings in programs. Passwords should newer be stored as plain text (but we will do it anyways for demonstration purposes)! Better thing to do is to store a hash of the password and compare hashes. First, let's demonstrate with an example what I mean by storing plain text strings: Now, let's look at this program with the debugger. By searching for all referenced strings in the program we can easily discover what the password is, no need for advanced techniques: Now, let's look at something more interesting. In this case we have an alphabet (char array), where we have defined our char set. When it comes to checking the string - we co...

Buffer overflow is a vulnerability, which is usually caused by uncareful handling of user input, but it does not end there. Most of the time it happens when data is being copied into a buffer, which does not have enough space and as a result part of the process memory is being overwritten. It might seem as not that big of a deal at first, but it should not be underestimated. Here is a very basic example of a variable overflow: In this example we are continuously adding 10 to a variable. It may seem like this code will never exit the while statement, because we can keep adding 10 to a variable forever, but that's not quite how it works in programming languages. The thing is that every variable type has some amount of memory allocated to store it's value, thus creating a limit. In this case I created an Integer, which only can store values that can be represented in 4 bytes of space (approximately from -2 billion to +2 billion). When we reach the maximum positive value and ...