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Questions tagged [disassembly]

The translation of machine code into a human readable assembly code, also the result of such translation.

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Legality on sharing rom dumps on abandoned hardware

I have an old piece of HP test gear from the 80's that HP no longer supports. I want to add in a feature and need to dump roms and figure things out to do that. How can I share my process and ...
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Can anyone please explain this disassembly code? [on hold]

Disassembly: 0: 6a 05 push 0x5 2: 58 pop eax 3: 31 c9 xor ecx,ecx 5: 51 push ecx ...
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1answer
79 views

Can anyone please explain the following dissasembly codes?

Disassembly: 0: 31 c9 xor ecx,ecx 2: f7 e1 mul ecx 4: 51 push ecx 5: 68 2f 2f 73 68 push 0x68732f2f a: 68 2f 62 69 ...
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21 views

Finding lua C functions compiled binary

So i am trying to "hack" a game however not for cheating purposes. I am looking to extend the games scripting functionality through a DLL that can look for processes and return them. The game I am ...
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1answer
56 views

When can trapping be used?

This is the beginning of one of the functions inside NTDLL of Windows XP: MOV EDI,EDI PUSH EBP MOV EBP,ESP ... The book on reverse engineering I am reading(Eldad Eilam - Reversing: Secrets of ...
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2answers
51 views

Calculation with not defined variables?

I am new to reverse engineering and try to solve a crackme with radare2. My problem is understanding of the following lines: | 0x000007a9 c745b8000000. mov dword [var_48h], 0 | ...
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1answer
61 views

Extract a secret from an Android apk or .so file

Context As an exercise I am researching all methods of hiding a secret in an android mobile app binary... Yes I know that with more or less effort they can always be extracted with static analyses, ...
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3answers
152 views

Jump in the middle of an instruction Coldfire firmware

I'm working on an embedded system Coldfire ROM. Currently, I'm trying to reverse engineering it to gain some more in-depth knowledge about its structure. ROM code quality seems pretty low, and I see ...
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Asking the meaning of an assembly instruction [duplicate]

I want to know the meaning of following instruction. MOV AL,BYTE PTR DS:[ECX+402158]
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1answer
83 views

Why disassemble multi-thread binary is hard?

Why disassemble multi-thread binary is hard? I also know that some obfuscation techniques are to create unnecessary threads. But why reverse engineering multi-thread program is hard.
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26 views

Error Exception EOLeSysError class, When execute delphi program

I ran into a error and get the following message and just have EXE Files: Error EOLeSysError class not registered Class Not Registered. How I can find the name of the class which is not registered?...
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133 views

Unable to figure out how to map segments in IDA

I have a 2 MB executable that I'm attempting to reverse engineer. It's executed on a 16-bit 8086 CPU. The segments go from 4000 (0x140000) to F000 (0x1F0000). I'm attempting to map the segments in ...
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84 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
73 views

How do the PSHUFLW and PSHUFD instructions work?

I have been trying to figure out exactly what is happening with these instructions and can't make sense of them. I can see that the PSHUFLW instruction acts upon the first 16 bytes of the XMM register ...
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1answer
32 views

How is the I/O address space on the PC arranged?

I'm disassembling a 16-bit DOS executable, and looking at the following three instructions: mov dx,0x3ce mov ax,0xff08 out dx,ax I know it writes the value 0xff08 to I/O port 0x3ce. I also know that ...
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2answers
123 views

Lots of mov instructions into ebp+offset - What is happening?

While learning RE I have come across this large segment of instructions that contains a majority of mov [ebp+offset], value instructions. I believe that ebp + offset are local variables? I think? ...
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2answers
136 views

Why are there so much more functions in ida than my source code?

I am trying to learn how to use IDA Pro 6.8 to analyze binaries. However, there are much more functions in ida function list than my code. For example, there is a function in source code that calls ...
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1answer
50 views

Why does -A (aaa) analysis show much more information, when using the -d (debug) CLI option in Radare2?

Why does -A (aaa) analysis show much more information, when using the -d (debug) CLI option in Radare2? I'm using the newest version of Radare2 to analyze the Windows application. As can be seen ...
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2answers
148 views

Can Machine Learning be used to develop better reverse engineering tools? [duplicate]

So i googled this but other than some papers i couldnt find any reverse engineering tool that was built using machine learning I'm not an expert in machine learning and deep learning but it seems ...
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1answer
83 views

Reversing PE32 executable - CTF Question

So we were playing CTF , and we found this interesting RE challenge . And when we did a statical analysis to the file we found an interesting for loop . for (var_84 = 0x0; var_84 < 0x13; var_84 = ...
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1answer
65 views

Strange Message after manipulating an exe file

i debugged und reversed an exe file with x64dbg I simply changed an assembly command (je) into nop , patched the file and saved it under a different name. (only one line was changed) When i tried to ...
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2answers
115 views

Can't find SetCooperativeLevel call in disassembled program

I am trying to make some changes to the setup program that installs the game "Emperor: Battle for Dune". If you want to look at the EXE I am working on, you can download a copy of this setup program ...
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How is DS register interpreted in x86-64 assembly instructions?

IDA disassembled an x86-64 instruction as below: 0000000000000761 lea rdx, ds:0[rax*4] What I know is, segment registers are only relevant in in segmented memory model, while in ...
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1answer
124 views

How can I make IDA understand this switch statement with a signed jump table?

I took the following C code and compiled it on Ubuntu 16.04 with GCC 5.4.0: int main() { int a = 0; for (int i = 0; i < 5; i++) { switch (i) { case 0: a = 1; break; ...
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Getting function arguments with IDA: When do function prototypes exist?

This post explains how to get function arguments using idapython. However, I read here that get_arg_addrs() requires the prototype of the called function to be present. My question: In which cases ...
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44 views

Common practices for 'hiding' a class within an Android application?

I've recently gotten into Android reverse engineering, and I've been messing around with some apps lately for education/research purposes to see how some things are done with private (mobile) APIs. ...
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1answer
164 views

How to disassemble a packed .NET executable?

I'm trying to reverse a Windows executable that shows as having been packed with ENIGMA(5.X): If I later check the class name for one of its UI elements, when the process is unpacked and running, it ...
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1answer
229 views

Reverse Engineering bios of ATM Machine

I bought an Hyosung NH1500 off Offer-up and it boots up and initializes some peripherals and then spits out and error of "COM download is failed". I've searched Google and 0 results came up, I've been ...
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0answers
39 views

int 2eh instead of syscall/sysenter [duplicate]

I have been looking into ntdll.dll on windows 10 x64 bit, and i noticed a check inside the ntdll like this: So after testing some bit, it tries to execute the system call via int 2eh. I have tried to ...
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2answers
80 views

Check if instruction is reached

I am doing a challenge for a CTF and I have to reverse an encryption scheme to find a flag. However it would be easier to just try all inputs but they are too much. There is an instruction that when ...
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1answer
121 views

Finding the main function without symbols

for a C/C++ program compiled on windows using the x86 architecture, what is the best way to find the main function within disassembled code? I've found various answers to questions similar to this, ...
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1answer
104 views

Can someone please help me reverse engineer this assembly code to C please! [closed]

I am really bad at understanding assembly code and the way it works. I have little problems given to me in Assembly code and I have to reverse engineer it to C, but I have been doing really bad job at ...
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1answer
365 views

XCHG RAX, RAX: 0x09, what does this code do and how does it work?

Given the following short assembly snippet: shr rax, 3 adc rax, 0 I worked this out a bit: We know SHR sets the CF with the last bit shifted. We know ADC dest, 0 is just adding the CF. So ...
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78 views

Has anyone reversed Wyze cameras? [closed]

Has anyone looked at the hardware to see what processor they're using or disassembled the firmware? Wyze claims to have opensourced their firmware but their github repository seems to be mostly ...
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1answer
56 views

Reversing characters from argument of the program

Below code is from the IDA. This is the code before the parsing function: movzx eax, byte ptr [rbp+nineth_char+3] movsx eax, al mov edi, eax call sub_898 And this is the code of the ...
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1answer
75 views

How are ARMv7 assembly opcodes and operands stored in bytes?

I've been trying to analyze an ARM binary but cannot figure out how the operators and operands are stored in the bytes of a program. For example, by looking at the disassembly listing of an ARMv7 ...
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40 views

getting %localappdata% in asm

I have an old windows x86 application that no longer works properly since windows 8. This app creates files within its own folders for things like app settings. Unfortunately, Microsoft no longer ...
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1answer
115 views

Radare2 Call $+5 and register-based cross-references not found

I have a library of ~65MB which uses this "technique" as a kind of PIC. First, it gets some kind of base address (it is always the same): 0x00708497 e800000000 call 0x70849c 0x0070849c ...
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2answers
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Why there are two different shellcodes for bin/sh with much different syntax and which one is better to use? (x86)

I have found two shellcodes for spawning /bin/sh which are much different from each other. The second one is hardly ever found on the net, and it mostly comes up in reverse engineering websites: 1. "\...
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1answer
241 views

Converting Assembly x64 code to C

I have the following code: 0000000000400526 <main>: 400526: 55 push rbp 400527: 48 89 e5 mov rbp,rsp 40052a: 48 83 ec 20 sub ...
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1answer
216 views

How can I convert this assembly code (x64) to C?

I have the following assembly (x64) function: 400700: sub rsp,0x18 400704: mov QWORD PTR [rsp+0x8],rdi 400709: cmp QWORD PTR [rsp+0x8],0x0 40070f: jne 400718 <bar+0x18> 400711: mov eax,0x0 ...
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1answer
103 views

Figuring out what a segment of assembly code does

I have the following assembly code: 0000000000400711 <foo>: 400711: 55 push rbp 400712: 48 89 e5 mov rbp,rsp 400715: 48 89 7d e8 ...
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1answer
97 views

How can I decompile the CC2650 .hex file to C?

I want to decompile it to C, or at least assembly the CC2650 hex file (Bluetooth Low Energy Sensor Tag), that provide TI. My goal is to know the specific way used by CC2650 to generate the LTK. I'll ...
4
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1answer
174 views

Need help identifying main processor for Roland synthesizer

I desperately need help figuring out the ic chips in this unit so I can view the firmware in ida pro. So the unit is a roland gr-55 guitar synthesizer and i'm trying to disassemble the firmware into ...
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2answers
196 views

.NET assembly IDA PRO, using LDSTR IL op code, how to patch a string?

I'm trying to patch a string. So right now I'm trying to replace instruction LDSTR with LDSTR "mystring"; however, I have been unsuccessful. After assembling the LDSTR op code, I don't quite ...
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2answers
304 views

Move twice, from and to the same location

I'm trying to reverse a function and I came across these lines inside the function: 1. call ds:HeapAlloc 2. mov [ebp+var_4], eax 3. mov eax, [ebp+var_4] Why is line 3 needed? If I need to ...
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2answers
185 views

replacing static value with variable

I'm trying to replace a static value: MOV DWORD PTR SS:[EBP-30],4c With a value from a specific address: MOV DWORD PTR SS:[EBP-30],400400 // MOV DWORD PTR SS:[EBP-30],OFFSET 400400 But SS:[EBP-30] ...
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2answers
141 views

Getting opcode Length , How to

I am apparently not very good with assembly as I am novice to somethings! Hence i wanted to make a question again. Now i got this from here to make something like a LDE (Length Disassembly Engine) ...
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4answers
867 views

Calculation of jmp address through subtraction

I don't get why the two addresses of the functions are subtracted in order to get the jump destination. mov eax, [ebp+func1] sub eax, [ebp+func2] sub eax, 5 mov [ebp+var_4], eax Which ...
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2answers
521 views

Can't find the password anywhere in the binary

This is my first post here. I was recently involved in a capture the flag preparation test which involved decompiling an ELF 32-bit LSB executable, Intel 80386 file for Linux compiled with GCC. The ...