Questions tagged [x86-64]

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Trying to call the Exit Shellcode in a c program

#include<stdio.h> #include<stdint.h> char shellcode[] = "\xb8\x3c\x00\x00\x00" "\xbf\x14\x00\x00\x00" "\x0f\x05"; int ...
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32 views

Instruction-level hooking library for win32?

I am looking for instruction-level hooking library for win32 x86/x64. I want to write hook insertion and hook implementation code in C/C++ (compiled into dll). (Therefore instrumentation tools are ...
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0answers
41 views

Memory modified at jump far

Observing a trace of Wow64 switching on Windows 7, the following situation makes me confused ... 0x77491dbe 64 ff 15 c0 00 00 00 call fs:[0xc0] ; syswow64\ntdll.dll 0x74632320 ea 1e 27 63 ...
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30 views

Go back to the original entry point after executing the instructions in the newly added segment- PE32+, C++

I am learning PE32+ (64 bit) files. I have added a new section to the PE32+ file and made the new section as the entry point. Some simple instructions are added in the new segment. Now I want to go to ...
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149 views

How to interpret binary instruction using the intel manual

OK. So I am really trying to figure out how to use the "Intel 64 and IA-32 Architectures Software Developer's Manual" for myself, since it seems like the authoritative source for x86(_64) machine code....
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1answer
327 views

Why address 7FFE0308 always gets compared in 64bit applications before making a syscall in Ntdll?

So there was a question asked before about this : What are the difference syscall and int 0x2E instructions? and it has two answer, one says that is just a way to check if we are in a 32 bit or 64 ...
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1answer
66 views

Need Advice for the purposes of learning [closed]

I would really like to make a multiplayer mod for Fallout 4, I know how to program and i have a basic understanding of how to get opcodes and read/write to those. Now what i don't understand is how to ...
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780 views

Find memory mapped file with x64dbg

I have 64 bit process I want to debug with x64dbg. There is memory mapped file, I found with help of Process Explorer. Properties windows says: Type: Section Description: A memory mapped file or ...
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1answer
272 views

How to debug a crash in wow64.dll in 32bit process

I have a 32bit application and a few wrapper tools that I use one after another to inject code, hook system dll functions (using the patch-first-bytes-of-the-function-with-jump approach). Also I have ...
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2answers
1k views

.00cfg section in the PE file

What's that .00cfg section that is being added by Visual Studio 2017 to PE32+ binary files (for x64 builds)? I'm assuming it stands for "Control Flow Guard" section. It is relatively small and mostly ...
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2answers
90 views

Where do arguments 5 and 6 go in this Microsoft x64 function call?

I'm disassembling a working-as-expected compiled C program (MS/Windows x64, MinGW gcc 10.1.0). In the main function, I have the following call which passes 6 arguments to the function DotProduct: ... /...
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1answer
102 views

MSVC Generates Weird Code for Volatile Local Variable

I want to know how MSVC 2010 generates code for volatile local variable and have done a test. This simple test function uses a volatile local variable: int proc1(int a, int b) { int volatile ...
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1answer
549 views

IDA Pro 64bit offset and opcode issue

I'm looking at a 64bit PE file in IDA. The instructions below access unknown data at offset 20030. Usually when I look at 32bit PE files, the offset is also listed next to the opcodes on the left. So ...
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1answer
570 views

brute force remote nop sled memory address

ELF x64 binary on a remote server communicates via simple socket server in C. After overflowing the buffer (total buffer is 2000, password buffer is less), overwriting the RIP, filling with NOP sled (...
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1answer
318 views

What do square brackets do in IDA's pseudocode representation?

I've been a bit stumped recently on my decomp work. I've not dealt with C in depth nor have I dealt with IDA's pseudocode system very much at all. I understand asm, but because of how IDA merges ...
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1answer
242 views

How do I go about overriding a function internally defined in a binary on Linux?

To be specific, I cannot recompile this binary, nor do I have access to the sourcecode. The functions are not defined within a shared library. So, how can I go about changing a function, or ...
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1answer
270 views

How to locate an specific data structure in an executable?

I need to locate an specific "struct" variable in the data section from an assembly. This structure is used for an specific System Function (Windows) "SetCommState()". I'm wondering how to locate the ...
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1answer
326 views

x64 Linux reverse-engineering - understanding asm code and inject eax

In a rootme exercise, i'm trying to bypass the control impleted to protect a "read" function. You'll find enclosed the code i'm refering to. As you may understand, i can inject data (with limitations) ...
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1answer
83 views

Calling MessageBoxW x64 confused about pointer

OK, I am very new to x64dbg. I used to use OllyDbg a lot and I'm having some problems with this. I just made a customized version of MS-PAINT for practice by changing a few things like the default ...
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1answer
95 views

How can I modify these?

So I'm onto something interesting, I asked the less direct way but failed to meet the requirements in terms of explanation So here it is, how would I go about editing these the same way I would go ...
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1answer
145 views

How to determine when/where pointers in .ctors get mapped?

So I am learning about ELF, and am looking through a binary in Ghidra as I do. I've made sense of the ELF header, and now I am looking through the program header table. My binary has a bunch of ...
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1answer
199 views

XCHG RAX, RAX: 0x03, what does this code do and how does it work?

"XCHG RAX, RAX" is a kind of riddle book that provides assembly code for you to reverse and undercover the meaning. Some of the examples calculate the Fibonacci sequence others bit-twiddle to toggle ...
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1answer
77 views

Reading params of a text engine function amd86_64

I'm starting to learn amd86_64 calling convention and how it calls params and clean the stack but the concept hasn't sunk in yet, so i would like to get a help reading the params as this might clear ...
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2answers
83 views

Magic number in resource loading routine

I'm practicing windows disassembly on x64 notepad.exe I've managed to find buffer allocation and string resources load. But after that follows code, which I can't fully understand: rbx = 0, rdx = 0 ...
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1answer
872 views

Linux x64 Disassembly: single movzwl operand question

A quick question regarding a movzwl instruction which do not behave as I expected. here is the disassembled code: movzwl (%rax),%eax Before the instruction, rax is 0x7fffffffe410 and point to 0x5 ...
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2answers
978 views

Trying to call a function in an unknown DLL

My goal is far from nefarious. After several polite attempts to try and get Lenovo to implement a proper keyboard backlight control, I've had no response. They do have a Windows Store app which adds ...
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1answer
146 views

Why is using a 32bit system over 64bit recommended for people that are new to reverse engineering? [closed]

I am new to the world of reverse engineering and have been recommended by a number of people that I should start with IA32 because it is easier to learn the concepts. Aside from differences in the ...
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1answer
1k views

Calling DLL exports in x64dbg

I am attempting to debug a x64bit dll with x64dbg. Is there an export caller similar to Ollydbg? I checked the documents and haven't seen anything.
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38 views

How can I connect basic blocks seperated by unconditional jmps?

I'm analyzing an obfuscated code which splits its code into multiple blocks seperated by many, many unconditional jmps. Here is a picture of what the obfuscation looks like: I wrote an IDAPython ...
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0answers
31 views

objdump says “64-bit address is disabled”

I've run into an issue with the MinGW build of objdump on Windows. Consider this very simple input file: 48 bf 88 77 66 55 44 33 22 11 I want to disassemble this as Intel x86-64 raw machine code. I ...
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40 views

Remapping Branch Instructions After Obfuscation

Recently I've been working on a project. I've already got a hint for a problem that I had here: (Garbage Assembly Code Generationat at random offsets) however, the accepted answer's solution doesn't ...
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1answer
60 views

Cant recognise where is my targeted function executed

Im trying to recognise where is my targeted function int64 __fastcall sub_1400CE4F0(__int64 a1, const char *a2)executed. When stepping through this function, after return it's redirecting me here: if (...
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47 views

Change value of memory in a debugger?

So I got this app loaded in x64, there is a function, let's say "HeatGainedPerShot", which is basically the value which an object gains everytime it fires, Such a value would normally exist ...
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38 views

Windows pintool mismatch between call/ret instructions

So i've been trying to write a pintool that monitors call/ret instructions but i've noticed that threre was a significant inconsistency between the two. For example ret instructions without previous ...
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0answers
97 views

Bufferoverflow Stack

I want to do a buffer overflow exploit in the stack. For this i read in data via the "gets"-function. void ExploitMe() { char buffer[256]; gets(buffer); } I compile this file with gcc test.c -...
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184 views

R13 off by 2 bytes. Any help?

in this challenge i have to overwrite RIP register to point to the function "print_flags" which calls "getenv" to get the "FLAGS" variable. I have overwritten RIP register with the address of "...
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1answer
162 views

Calculate LEA operand

I have those opcodes on 64 bits: 48 8D 35 45 CE FF FF >>> lea rsi, [rip - 0x31bb]. How can I get the 0x31bb value from those opcodes and how can I know if I have a + sign or a - sign ...
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2answers
3k views

How can I use an x64 debugger to reroute a .NET application's logic?

I'd like to improve my reverse engineering skills, so I made this WPF application (targeting x64, of course): MainWindow.xaml: <Window x:Class="ApplicationTest.MainWindow" xmlns="http://...
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1answer
72 views

What does xchg means when accessing array element?

I have ASM code of some Windows *.exe in IDA: mov rax, [rbx+10h] mov ecx, edx xor edx, edx xchg rdx, [rax+rcx*8] Which is decompiled to pseudocode to _RAX = this->m_someMemoryPool; ...

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