![]() To be able to exploit a buffer overflow vulnerability on a modern operating system, we often need to deal with various exploit mitigation techniques such as stack canaries, data execution prevention, address space layout randomization and more. GNU Debugger (GDB) is the most commonly used debugger in the Linux environment. In the Windows environment, OllyDBG and Immunity Debugger are freely available debuggers. A debugger can help with dissecting these details for us during the debugging process. When writing buffer overflow exploits, we often need to understand the stack layout, memory maps, instruction mnemonics, CPU registers and so on. Understanding how to use debuggers is a crucial part of exploiting buffer overflows. The user-supplied buffer often overwrites data on the heap to manipulate the program data in an unexpected manner. The successful exploitation of heap-based buffer overflow vulnerabilities relies on various factors, as there is no return address to overwrite as with the stack-based buffer overflow technique. Heap overflows are relatively harder to exploit when compared to stack overflows. ![]() When a user-supplied buffer is stored on the heap data area, it is referred to as a heap-based buffer overflow. As mentioned earlier, a stack-based buffer overflow vulnerability can be exploited by overwriting the return address of a function on the stack. When a user-supplied buffer is stored on the stack, it is referred to as a stack-based buffer overflow. The following are some of the common buffer overflow types. However, a buffer overflow is not limited to the stack. We have just discussed an example of stack-based buffer overflow. That’s the reason why this is called a stack-based buffer overflow. If this overflowing buffer is written onto the stack and if we can somehow overwrite the saved return address of this function, we will be able to control the flow of the entire program. This function doesn’t perform any bounds checking implicitly thus, we will be able to write more than 256 characters into the variable buffer and buffer overflow occurs. However, we are performing this copy using the strcpy function. This argument is being passed into a variable called input, which in turn is being copied into another variable called buffer, which is a character array with a length of 256. If you look closely, we have a function named vuln_func, which is taking a command-line argument. This is a simple C program which is vulnerable to buffer overflow. So let’s take the following program as an example. In simple words, it occurs when more data is put into a fixed-length buffer than the buffer can handle. There’s a reality here for all of us.Buffer overflow is a class of vulnerability that occurs due to the use of functions that do not perform bounds checking. ![]() "This incident makes it abundantly clear that anyone with a phone is impacted by the kind of vulnerabilities that customers of these companies are slinging around. "Companies like NSO Group try to keep a little stockpile of things that can be used to get onto devices," says John Scott-Railton, a senior researcher at the University of Toronto's Citizen Lab. But you should still download the patch on your Android and iOS devices. The WhatsApp bug was being exploited to target only a small number of high-profile activists and political dissidents, so most people won't have been affected by any of this in practice. ![]() "Security never was WhatsApp's primary design objective, which means WhatsApp has to rely on complex VoIP stacks that are known for having vulnerabilities." "This does indeed sound like a freak incident, but at the heart of it seems to be a buffer overflow problem that is unfortunately not too uncommon these days," says Bjoern Rupp, CEO of the German secure communication firm CryptoPhone. The Facebook-owned company told the FT that it contacted a number of human rights groups about the issue and that exploitation of this vulnerability bears "all the hallmarks of a private company known to work with governments to deliver spyware." In a statement, NSO Group denied any involvement in selecting or targeting victims but not its role in the creation of the hack itself. WhatsApp, which offers encrypted messaging by default to its 1.5 billion users worldwide, discovered the vulnerability in early May and released a patch for it on Monday. But how would a hack like that even work in the first place? The targets didn't need to pick up to be infected, and the calls often left no trace on the phone's log. But a new Financial Times report alleges that the notorious Israeli spy firm NSO Group developed a WhatsApp exploit that could inject malware onto targeted phones-and steal data from them-simply by calling them. Don't click links in suspicious emails or texts.
0 Comments
Leave a Reply. |