#Buffer overflow 1 code

Base Pointer (BP): (also known as the frame pointer) Points to the base of the current stackframe.

Instruction Pointer: Points to the address of the next CPU instruction to be executed.

Stack Pointer: Points to the top of the process call stack (or the last item pushed onto the stack).

In order to keep track of this, a computer keeps several pointers in memory: There will be a stackframe for each function that hasn't yet finished executing, with the function which is currently executing on the top of the stack. It's a stack of variables and stackframes which tell the computer in what order to execute instructions.

#Buffer overflow 1 code

As the process executes the main function, it will find both new local variables (which will be pushed onto the top of the stack) and calls to other functions (which will create a new stackframe).Ī diagram of a stack, for clarity: (abstract_data_type) So, what's a stackframe?įirst, a call stack is basically the assembler code for a particular program. When an executable is run, it runs within a process, and each process has its own stack. This means that a heap overflow would likely have to overwrite a function pointer – harder and less effective than a stack overflow.Īs stack overflows are the more commonly exploited type of buffer overflow, we'll briefly dig into exactly how they work. Memory on the heap typically contains program data and is dynamically allocated as the program runs. This return address can be replaced with the instruction to instead execute a piece of malicious code.Īs heaps less commonly store these return addresses, it's much harder to launch an exploit (though not impossible). This is because stacks contain a sequence of nested functions, each returning the address of the calling function to which the stack should return after the function has finished running. In general, stack overflows are more commonly exploited than heap overflows.

Or, on the heap: int* ptr = malloc (10 * sizeof(int)) īuffer overflows can occur on the stack (stack overflow) or on the heap (heap overflow). To declare a variable on the stack: int numberPoints = 10 In a C program, you can allocate memory on the stack, at compile time, or on the heap, at run time. In order to understand buffer overflows, it's important to understand a little about how programs allocate memory. While C, C++, and Objective-C are the main languages which have buffer overflow vulnerabilities (as they deal more directly with memory than many interpreted languages), they are the foundation of much of the internet.Įven if the code is written in a 'safe' language (like Python), if it calls on any libraries written in C, C++, or Objective C, it could still be vulnerable to buffer overflows. This can cause data corruption, program crashes, or even the execution of malicious code. A buffer overflow occurs when the size of information written to a memory location exceeds what it was allocated.