The top of the memory is the kernel area, which contains the command-line parameters that are passed to the program and the environment variables. The operating system will effectively call the main method of the code as a function, which then starts the flow for the rest of the program. When a program is run by the operating system (OS), the executable will be held in memory in a very specific way that's consistent between different processes. In this article, I will focus on the core principle of buffer overflows. There are ways to bypass these measures, but that's a (more advanced) topic in itself. NOTE: For the purpose of this article and its examples, I have disabled protective measures, like Address Space Layout Randomization (ASLR), that may interfere with a clear demonstration of the buffer overflow issue. However, note that the issue applies to many different languages and operating systems. In this example we're using a C program in Linux. In order to understand how buffer overflows work, we need to understand what happens in memory when a program is run. A few examples are the PS2 Independence exploit, the Twilight Hack for the Wii or an iDevice Lock Activation Bypass on the iPad.
By sending carefully crafted input to an application, an attacker can cause the application to execute arbitrary code, possibly taking over the machine.Īttackers have managed to identify buffer overflows in a many products and components. How does a typical buffer overflow exploit work in code, at run-time and in memory and what can be achieved by running it?Ī buffer overflow occurs when a program or process attempts to write more data to a fixed length block of memory (a buffer), than the buffer is allocated to hold.
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