Windows based buffer overflow exploit writing

With this technique, we basically use a register that contains the address where the Shellcode resides and put that address in EIP. This only works if one of the available registers contains an address that points to the Shellcode. This is how we are going to exploit the Server. If we cannot find a or opcode anywhere, we could simply put the address on the stack and then do a ret. So we basically try to find a push , followed by a ret. Find the opcode for this sequence, find an address that performs this sequence, and overwrite EIP with this address.

If we are faced with the fact that the available space in the buffer after the EIP overwrite is limited, but we have plenty of space before overwriting EIP, then you could use jump code in the smaller buffer to jump to the main Shellcode in the first part of the buffer. So even if the application itself does not use exception handling, you can try to overwrite the SEH handler with your own address and make it jump to your Shellcode. Using SEH can make an exploit more reliable on various windows platforms, but it requires some more explanation before you can start abusing the SEH to write exploits.

The idea behind this is that if we build an exploit that does not work on a given OS, then the payload might just crash the application and trigger an exception. Note that a typical stack based overflow, where you overwrite EIP, could potentially be subject to a SEH based exploit technique as well, giving you more stability, a larger buffer size and overwriting EIP would trigger SEH.

We will be adding a dll file in the Server machine. So download the DLL file and keep it in the same folder as the server. You will need it further. Shell Shell is a piece of code or program which can be used to gain command execution on a device. There are two types of Shell which is explained below: Bind Shell Bind shell is a type of shell in which the target machine opens up a communication port or a listener on the victim machine and waits for an incoming connection.

Figure 6. Bind Shell Reverse Shell A reverse shell is a type of shell in which the target machine communicates back to the attacking machine. The attacking machine has a listener port on which it receives the connection, which by using, code or command execution is achieved.

Figure 7. Reverse Shell The above details are the basic thing that you should know to perform the attack. You can also leave the comment below for any question regarding it and also if you have any suggestion on it. Riha has spent many hours exploring ways to penetrate windows machine, android devices, servers so she could get better idea of what she could be looking forward to in her field of Cyber Security.

She also found vulnerabilities in her college's website which she reported. Riha enjoys spending her time writing about the practical experiments that she performed. She also spends a great deal of time learning Guitar and watching TV Series. You must be logged in to post a comment.

No products in the cart. Blog Buffer Overflow Exploit — Part 1. Shell is a piece of code or program which can be used to gain command execution on a device. There are two types of Shell which is explained below:.

Bind shell is a type of shell in which the target machine opens up a communication port or a listener on the victim machine and waits for an incoming connection.

A reverse shell is a type of shell in which the target machine communicates back to the attacking machine. The attacking machine has a listener port on which it receives the connection, which by using, code or command execution is achieved. The above details are the basic thing that you should know to perform the attack. You can also leave the comment below for any question regarding it and also if you have any suggestion on it. Riha has spent many hours exploring ways to penetrate windows machine, android devices, servers so she could get better idea of what she could be looking forward to in her field of Cyber Security.

Riha enjoys spending her time writing about the practical experiments that she performed. She also spends a great deal of time learning Guitar and watching TV Series. Email: rihazz13 gmail. Like Liked by 1 person. Like Like. You are commenting using your WordPress.

You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Skip to content Hi guys, if you are here it means you are stuck somewhere doing buffer overflow or want to perform it. What will this tutorial cover? What is Buffer Overflow? Stack-Based Buffer Overflow-The stack is a continuous space in memory used to organise data associated with function calls, including function parameters, function local variables and management information, such as frame and instruction pointers.

Heap Based Buffer Overflow-The heap is a memory structure used to manage dynamic memory. Program Image- The Program Image portion of memory is where the executable resides. Dynamic Link Library- DLLs are similar to executables, but they cannot be called directly, and instead they have to be called by an executable.

Information that is needed by systems that should not have access to kernel components is stored in memory. The first thread is known as the primary thread and each thread after that has its own TEB. Each TEB shares the memory allocations of the process that initiated them, but they can execute instructions in a manner that makes task completion more efficient. Kernel- The most critical component of the OS. All communication is brokered as necessary through OS features. The attacks we are highlighting here do not depend on a deep understanding of the kernel.

Stack and Heap Immunity Debugger Immunity Debugger is a powerful new way to write exploits, analyze malware, and reverse engineer binary files. An interface of Immunity Debugger As you can see, the CPU window is broken up into four panes depicting the following information: The CPU Instructions — displays the memory address, opcode and assembly instructions, additional comments, function names and other information related to the CPU instructions The Registers — displays the contents of the general purpose registers, instruction pointer, and flags associated with the current state of the application.

Pictorial View of working of a Buffer overflow in memory In brief, the buffer size given is Loading a DLL A DLL is a piece of code which, when used, is made apparent into the address space of the application, as code which can be executed.

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 heap data area, it is referred to as a heap-based buffer overflow. Heap overflows are relatively harder to exploit when compared to stack overflows.

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. The user-supplied buffer often overwrites data on the heap to manipulate the program data in an unexpected manner. Understanding how to use debuggers is a crucial part of exploiting buffer overflows.

When writing buffer overflow exploits, we often need to understand the stack layout, memory maps, instruction mnemonics, CPU registers and so on. A debugger can help with dissecting these details for us during the debugging process. 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.

The following makefile can be used to compile this program with all the exploit mitigation techniques disabled in the binary.

We are simply using gcc and passing the program vulnerable. We are producing the binary vulnerable as output. This looks like the following:. Now we are fully ready to exploit this vulnerable program. To do this, run the command make and it should create a new binary for us.

We should have a new binary in the current directory. Nothing happens. So we can use it as a template for the rest of the exploit. Let us also ensure that the file has executable permissions. As you can see, there is a segmentation fault and the application crashes. If you notice, in the current directory there is nothing like a crash dump.

There are no new files created due to the segmentation fault. This should enable core dumps. Type ls once again and you should see a new file called core.