Questions tagged [x86-64]

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How can i check if i am running in ring 0 / ring 3 on x64 CPU

I have read it is possible to check ring level with bit 3 of CS register. Is there another register which really contains ring value (2 bits) Thanks
2
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1answer
227 views

PE32+ executable : .text segment encryption

I am working on PE segment encryption(in C++). I completed the PE32 .text segment encryption. I added stub segment to the PE that will decrypt .text segment at runtime. Used inline assembly in the ...
1
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0answers
36 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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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 ...
1
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0answers
87 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....
1
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0answers
3k views

Receiving “Got EOF while reading in interactive” after properly executing system(“/bin/sh”) using pwntools

I've followed some tutorials on writing a pwntools-based exploit for the bitterman ELF binary, used in a CTF competition. However, all my attempts fail with the message below, i.e. Got EOF while ...
1
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0answers
1k views

Error: the file can't be loaded by debugger plupin IDA PRO 64 bit

I use IDA PRO 64bits on windows 10 64 bit, I want use it remote debug a file 64bit by linux. When I run linux_serverx64 in linux and connect then i error: the file can't be loaded by debugger plupin ...
1
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0answers
658 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 ...
1
vote
1answer
195 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 ...
0
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0answers
46 views

What does the file pointer of fgets actually point to in linux?

So i was reversing a 64 bit ELF binary, and it did a call to fgets, and based on documentation the third argument of fgets is a file pointer. now the weird part was that the third argument in this ...
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0answers
37 views

Extra Allocated Space in Stack and Wrong placement of Local Variable

I was recently reading reverse engineering for beginners by Yurichev where I happened to come across an example x64 MSVC and x64 GCC code. In this I'm unable to understand why there is a shadow space ...
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67 views

Why does this execve shellcode work with this argv?

I wrote the following program in fasm, and am using Evan's Debugger on Ubuntu to debug it: format ELF64 executable 3 segment readable executable entry $ mov rbp, rsp sub rsp, 32 mov rax, 'this a t' ...
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0answers
20 views

CPU integrated PCI device functions

I'm trying to reverse an Xeon based hardware bios. During the early initialization in the UEFI SEC phase, I stepped into some CPU embedded PCI devices initialization. After few hours researches, I've ...
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0answers
64 views

What's the point of changing the CS register and can any process do this?

So i was reading this article : http://waleedassar.blogspot.com/2012/07/wow64-user-mode-system-calls-hooking.html which explains the wow64, the part that we do a far jmp and change the CS register ...
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60 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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126 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 "...