13

First of all, I have bad news for you ! Doug Lea's malloc is almost no more used in any C library implementation (even if understanding dlmalloc can help a lot to understand new ones). The new implementation that is most widely used is ptmalloc2 and the best way to learn about it is... to read the code... So, if you are using a Debian(-like) distribution, ...


13

If you look at the disassembly of authorize() I'm sure you'll find that the compiler is pushing and restoring more registers than just EBP or aligning the stack. I would recommend that you always look at the disassemly when dealing with overflows of various kinds. The compiler and decompiler, if you use one, hides a lot of details. The disassembly never lies ...


11

On modern systems the most obvious culprit is probably address space layout randomization, but stack frame layout variablity was problematic for exploit development even before ASLR became widely implemented. This was alluded to in AlephOne's venerable "Smashing the Stack for Fun and Profit": The problem we are faced when trying to overflow the buffer of ...


8

You don't need to bypass gcc's stack smashing detection. If you overwrite key correctly, you get an interactive shell before the stack check is performed at the end of func(). Here's the proof in the form of a Python script: import socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(("pwnable.kr", 9000)) s.send("A"*52 + "\xBE\xBA\xFE\xCA" ...


8

As far as the screenshot depicts, I can say that you are on the right track. You have correctly, overwritten the Pointer to NextSEH and SE Handler. Some explanation: Exception Registration Record Structure typedef struct _EXCEPTION_REGISTRATION_RECORD { struct _EXCEPTION_REGISTRATION_RECORD *Next; PEXCEPTION_ROUTINE Handler; } ...


8

The answer from Jason is the correct solution. However, I wanted to give an alternative answer without Python, but from the terminal. IMO Python is always preferred for better automation, but sometimes you just wanna have a quick exploit done without extra tools. With that in mind, one's natural attempt would be something like below: echo -e "...


7

Yes, this is an implementation of what's often called "Stack Canaries", a method of stack Buffer Overflow Protection. That example you're describing is specifically the method used by Visual Studio, enabled by default since Visual Studio 2005, implemented since Visual Studio 2003. It is also called GS protection due to the fact Visual Studio provided the ...


7

AFAIR Windows XP does not necessarily crash on heap corruption, you need to specifically turn this behavior on using gflags.exe (from debugging tools) gflags /p /full /enable foo.exe Pageheap.exe might work as well, see http://support.microsoft.com/kb/286470 In any case, the point of exploitation is not to crash the process but to get it to run your code, ...


6

Nothing easier than that. gdb the executable, set a breakpoint at main, have gdb print your buffer. $ gdb /opt/protostar/bin/stack5 (gdb) break main Breakpoint 1 at 0x80483cd: file stack5/stack5.c, line 10. (gdb) run Starting program: /tmp/stack5 Breakpoint 1, main (argc=1, argv=0xffffd674) at stack5/stack5.c:10 10 stack5/stack5.c: No such file or ...


6

In fact, the memory layout within gdb and outside of it differs of a few bytes. There have been recently a question about this here. You can read: How to predict address space layout differences between real and gdb-controlled executions? In your case, you may just have to adjust your address by adding/subtracting 96 bytes. I can, also, give you a few ...


6

This comes down to the type of bug you are exploiting. If your payload cant contain null bytes (a vulnerable strcpy), this can become an issue, however not all bugs have this constraint. Take for example a bug in how a filetype is parsed, which allows null bytes. Also there is the possibility of a series of bugs to be used, for example, the idea of heap ...


6

first, you should disable ASLR system-wide, you can do this as follows: echo "0" > /proc/sys/kernel/randomize_va_space second, compile your program using flag with -zexecstack -fno-stack-protector -g example gcc program.c -o program -zexecstack -fno-stack-protector -g cheers :)


6

First of all, read this: https://www.blackhat.com/presentations/bh-asia-03/bh-asia-03-litchfield.pdf That's pretty much how all this started. A SEH buffer overflow is a specific stack overflow that targets the EXCEPTION_REGISTRATION_RECORD sitting some arbitrary distance down the stack. Why does this not happen for every program then since there should ...


6

Don't worry, the shellcode is executing properly, just that the debugger "skipped" past the execution. Remember that rip is the instruction pointer and whatever code present at the rip is executed. If the code is invalid however, something will go wrong (for example a SIGSEGV will be raised) In this particular case, a S (byte \x53) corresponds to a push ...


5

Yes, this is Microsoft's stack overflow protection, commonly known as "GS cookie". From Compiler Security Checks In Depth: When the function is compiled with /GS, the functions prolog will set aside an additional four bytes and add three more instructions as follows: sub esp,24h mov eax,dword ptr [___security_cookie (408040h)] xor eax,dword ptr ...


5

The only idea I have is to compare the dumps. The places that are same in all dumps are code or read only data. The places that are changing from dump to dump are either stack or section like .bss. After finding places that are not changing I'd try to disassemble these places in order to divide between code and data. I think that the places with the code ...


5

Nope. Metasploit is a pentester framework, not a reversing/malware-dev framework. Instead, you should master a debugger (IDA, Radare2, OllyDbg, etc) and at least one scripting language (Python or Ruby).


4

No.               ​


4

I'm sorry, but this certainly works for me. Lets go through this step by step, shall we? 1. Set up I used your command line to compile the program: gcc -z execstack game_of_chance.c -fno-stack-protector -no-pie -m32 -o goc I've done one small change though, I changed #define DATAFILE "/var/chance.data" // File to store user data to #define ...


4

You're doing well, with a little bit help you can exploit this program. First, let's look at stack layout for Linux (i assume it is Linux because of sudo and it is more common than other Unix-like OSes). old-EIP is not immediately after our buffer. I compiled your program in my 32-bit Linux Mint and as you can see GCC throw security warning. Lets, prepare ...


4

First thing that comes to mind when you have non-executable stack is Return-oriented programming which, as the name implies, uses return to execute a code you want. When using ROP, you will want to use the program's executable and dlls (or .so files for linux) and rely as little as you can on system dlls as they change with the OS version. The idea is that ...


3

We have two major stack protection for buffer overflows: Stack canaries Non-executable stack You land on nopsled but, you get segmentation fault. Because your operating system marked program stack as non-executable and processor raises the exception when program counter addresses that segment. But, even we have an executable stack (for GCC use -z execstack)...


3

The ROP chain uses gadgets, which are short code snippets performing a basic function. The instruction what you see in the Python script in the video are the gadgets names, which were selected in the beginning. As an example, the XOREAX gadget was a code snippet at address 0x080512c0, which contains the following instructions: xor eax, eax ret So, whet the ...


3

Metasploit can generate some malicious files, such as PDFs. Malware analysis isn't necessarily just Windows PE files so it might be a good idea to look into other file formats. Metaploit could be useful to generate your own samples to analyze. Msfvenom might be interesting to you as well. It is a tool that generates shellcode given a payload. ...


3

Yes, you can simply jump backwards. Control flow should reach your NOP pad, you can code your trampoline in there.


3

the latest visual studio compilers use runtime checks to detect overflows it performs them using a variety of run-time checks you can use them in un-optimized builds only /Od (these don't work in optimized builds not with /O1 or /O2 or /Ox) these can be either #pragmas or /RTC1 /RTCS | U | C command-line switches the stack corruption is detected by ...


3

The bug is in update_volume. pglobal_data -> radio_data.speakers_volume[index] = new_volume; index is an int, it can take negative values too. Ideally you should not be able to access -ve indices in an array as it gives you read/write over memory area preceding the array. Here we just have a check to limit its max value to 4 but you can use negative ...


3

__libc_start_main is called by the entry point code (usually in a file called crt0.S or similar) and that code usually sets up the initial EBP value (usually to 0, to denote end of the call stack for the debuggers). Here's a sample entry point code from a random ELF binary: _start: xor ebp, ebp pop esi mov ecx, esp and ...


2

You may find other people code useful and metasplot is good to test and understand how things can be exploited. For reversing there are alot of videos and sildes that other people have released explaining how they achieved there goals


2

You can read from and write to a process's data segment from shellcode (assuming proper page protections). However, you typically want to supply the data your shellcode is going to use (for example, the data string "http://172.19.3.204/stager.exe"), and not rely what's currently in the exploited process's data segment (for example, the data string "Internet ...


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