Questions tagged [c]
General purpose programming language that uses the procedural and structured programming paradigm.
292
questions
0
votes
2answers
64 views
Using a buffer overflow to call a function
I'm new to reverse engineering C binaries but have been working on an old ctf and thought to ask for explanation of specific assembly commands and how a buffer overflow might force a function to be ...
0
votes
0answers
44 views
How to maintain function ordering in an executable when replacing machine code with C step by step?
I am working on reversing a DOS game consisting of 16-bit MZ EXE files. I was able to determine the exectuables were generated by Microsoft C v 5.10, and loading the signatures from the static ...
0
votes
1answer
74 views
How to get the input necessary to get to the end
In short, I have a code that gets an input via stdin. Once it has the input string in memory, it verifies its integrity by calling a function for every condition, and exiting the program if those ...
1
vote
0answers
76 views
How to create an algorithm in C…(or C# or C++, basically in “a programming language”)
After a LOT of sending challenges and recording the responses I've 'broken' the "encryption" in my car's immobiliser...the reason for doing it is so I can use the engine and transmission in ...
1
vote
0answers
28 views
How do I disassemble mips .o object files in ida elf 64bit
So I’m trying to disassemble some object files in mips. I use IDA 7 on windows. These object files are loadable kernel modules. Mipself64 Is What ida auto sets to when they are dropped in. I’d like to ...
1
vote
0answers
44 views
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 ...
2
votes
1answer
91 views
Extracting strings from binary files (.exe)
This question has been asked quite a lot especially on stackoverflow, but the solutions/replies are not clear or extensive.
What I`m looking for is to build what Strings does from Sysinternals. My ...
3
votes
1answer
44 views
Confused about the use of the shl instruction in this disassembly
I created a code construct in C to see how it looks in x86. I'm confused about the use of the shl instructions. I'm confused about what is happening in between the lines <+39> and <+51> I ...
0
votes
1answer
91 views
How do I find missing/undefined vtable functions in IDA64?
I'm reverse engineering a game and came across some function calls like the ones shown below, how do I find where these functions are located / decompile them?
(*(BaseClient->int640 + 304))(...
0
votes
2answers
59 views
Import header files in IDA to get the struct definitions?
I am reversing a program that has a lot of internal structs in it.
The problem is that there are a lot of structs, so i can't import them manually using local types->insert.
Lets say i have some ...
0
votes
0answers
28 views
How to reverse engineer structs in radare2?
Is there any way to indentify structs in radare2?
when i tried to look them, they look like normal variables, i seen people using td and tl command but I don't know how to use them. If you know please ...
0
votes
0answers
54 views
Radare2 is showing weird disassembly as compared to disassembly of gcc
Today i was playing around with c code in r2.
I compiled a file which had the following code.
#include <stdio.h>
int main(){
int a=9;
float b=1.1;
int sum;
sum = ...
0
votes
0answers
23 views
malware emulator
I heard about malware emulators such as unicorn and speakeasy for gathering artifacts and It sounds interesting for me to build one. I have solid knowledge in C.
Are there any recommended tutorials to ...
1
vote
1answer
133 views
Arrays assembly
I'm reversing my C array's programs where I'm storing numbers in arrays like this...
int marks[5];
marks[0] = 1;
marks[1] = 3;
marks[2] = 2;
marks[3] = 7;
marks[4] = 9;
so the compiler showing me the ...
0
votes
1answer
74 views
Why compiler is doing this?
While I was disassembling my own C code for practice I saw an interesting point which I want to share with you guys and needs to know the answer as I always get from here. Now, the interesting point ...
2
votes
1answer
92 views
Not able to understand the C-switch statement in disassembly
While I'm trying to disassemble my own C code I am stuck in a problem of not understanding how this Switch statement is implemented in assembly code. Can anyone please help to figure it out? This the ...
0
votes
3answers
176 views
How to extract machine code from a file(especially executable) in C
How to get machine code of a file(mainly executables) in C?
I have written a C program to convert machine code to assembly. But how to get machine code of a file? How would I go about programming a c ...
0
votes
0answers
26 views
HexRay API - Programatically rebaseing program on firmware
I am working on several firmwares (mostly ARM and PPC) that have no structure that IDA can decipher and so far I have been guessing BASE address until the functions and strings align with what I see ...
0
votes
1answer
60 views
How to simplify a function “calling itself's reference”
I encounter often a function calling itself (in the pseudo code) such as:
result = (**(__int64 (__fastcall ***)(volatile signed __int32 *))lambda)(lambda);
Since the disassembly is call qword ptr [...
4
votes
1answer
183 views
Find Decryption algorithm of an encryption algorithm
I recently work on an algorithm that encrypt some data with 8 byte length.
I worked hard and I successful to get this algorithm, but I need decryption of this algorithm.
How I can invert it?
I guess ...
0
votes
1answer
41 views
Reverse engineering mode X VGA function(s)
I'm trying to reverse engineer an old DOS game. At the moment I'm stuck at a function that implements some functionality of VGA running in mode X. My issue is that any of the available sample codes on ...
0
votes
1answer
51 views
Assuming x is a number smaller than 0xff what happens to x after the assignment LOBYTE(x)=x-1?
I understand that LOBYTE is an IDA macro for retrieving the lower byte of a variable. My question is what is the difference between the result of x=x-1 and LOBYTE(x)=x-1 when x is smaller than or ...
0
votes
1answer
51 views
Link decompiled C code to Assembly (retdec decompiled object into C code, but with many errors, i found the kill switch which i need to edit)
I am using retdec to decompile a piece of software. It has a "kill switch" to detect if it's being run in an untrusted environment, in the decompiled code it just a simple
if (env_untrusted()...
0
votes
1answer
48 views
Call libc functions from the payload statically injected into ELF binary
I am working on ELF-injector, which given some payload (currently it's an assembly file with .text section only) will inject it into ELF binary. I had related post here.
Now I would like to make it ...
0
votes
1answer
36 views
Visual c compiler options
I ask if exist some c compiler option that can "keep" some imformation after compile that can be visible when I disassamble with IDA.
This because I need to find a particular funciton with ...
3
votes
1answer
225 views
ELF binary injection
I am currently working on an ELF-injector and my approach is standard: find code cave (long enough sequence of 0's), rewrite it with the instructions I want to execute and then jump back to the start ...
0
votes
0answers
67 views
How the return address of the notesearch program was calculated in “The Art Of Exploitation”
I am reading the book "The Are Of Exploitation" 2nd Edition by Jon Erikson and there is something I don't understand about the calculation of the return address.
In page 137 it covers the ...
0
votes
0answers
95 views
Delphi mt38 CRC (Tricore 1766 Arch)
I want to calculate CRC32 for Delphi mt38 and found the below assembly algorithm and converted it to C. It seems that this algorithm is defined for n = 256 or 1024. I want to calculate CRC32 for n = ...
0
votes
1answer
86 views
Converting rep movsd to to C without memcpy
So I am currently in the stages of creating binexact version of functions in decompiled code. I noticed that in this function the rep movsd is called and logically this is translated as Qmemcpy/memcpy ...
0
votes
1answer
59 views
Custom IDA Decompilation Format
Is there a way to customize the format of IDA's decompiled code?
e.g.
char buf[7]; // [rsp+5h] [rbp-1Fh]
to
char buf[ 7 ]; // [ rsp + 5h ] [ rbp - 1Fh ]
or
switch (c)
to
switch( c )
0
votes
0answers
156 views
Binary bomb lab, can't find starting number and having problem recognizing pattern
The following is the assembly dump of a binary bomb from bomb lab Basically, you have to come up with a 6 number sequence to defuse the bomb, however, I am having trouble finding the first number and ...
2
votes
1answer
130 views
Why can't find hardcoded string in the disassembled program?
I've wrote a simple program to print something on the screen as below:
ebra@him:/tmp/tuts$ cat sample.c
#include <stdio.h>
int main()
{
puts("Sample!");
}
ebra@him:/tmp/tuts$ ...
-1
votes
1answer
76 views
Why I get 0xc00000005?
I'm trying to use RunPE technique (For learning).
First, I tried it on Windows XP(32-bit) and no error occurs but, the injected code for(HelloWorld) didn't run.
Then, I tried to use it on Windows 7 ...
0
votes
0answers
59 views
Reverse an encryption algorithem in APK .so file
I try to reverse a cipher algorithm (I guess Tiny Encryption Algorithm (TEA)) in an android application. But I have a serious problem in initializing arguments. How I can understand that I have ...
0
votes
2answers
289 views
how to use class member function defined in a exe within a dll
I have an executable (.exe) containing some classes and functions definition and plan on using those functions from within a DLL, although I know to call a regular C style function using calling ...
0
votes
0answers
23 views
What is the meaning of call ds:ApiName[registry*constant] in IDA .asm files?
I have a dataset of .ASM files generated by IDA (dont have the corresponding file)
now there are a lot of calls like this :
.text:00637114 5F pop edi
.text:...
0
votes
1answer
51 views
Application only Crashes on CPU with SHA extension
Have an application that only crashes if CPU has SHA extensions. After some investigation find a hashing routine that only occurs if CPU has SHA extensions.
I'm trying to confirm if issue is with ...
5
votes
2answers
1k views
Difference between Main and Entry
Sometimes, I see while disassembling a binary that there is the main function. but sometimes, instead of main, there is entry function.
I want to know what is the difference between entry and main.
0
votes
0answers
142 views
C166/C167 code analyzing
Recently I try to reverse piece of assembly code that written for C166/C167 Arch.
But I have a problem with some places for convert to C code, such as:
loc_1892:
mov r9, #4
add r9, r0
mov ...
1
vote
1answer
185 views
How to restrict angr to printable characters
I have a binary that scanfs and then does some checks and returns either FAIL or SUCCESS that has SUCCESS for multiple inputs. Although only one of the inputs has only printable characters. How do I ...
0
votes
1answer
81 views
Buffer space in C
I was wondering if there is some way to get information about buffer size via reversing the binary, created in C language. can we also know how many buffers we have created while writing that script.
...
2
votes
1answer
229 views
How do we decompile java so easy?
I have seen a lot of videos where everyone is decompiling the jar files so easily. but I learnt that we cannot decompile any compiled file so easily. I have a little bit of experience in Gidhra. I ...
0
votes
1answer
106 views
2 byte format string attacks
Protostar
I was doing the protostar format string (3rd challenge). where we have to change the value of a variable target with format string buffer overflow. so, I came up to this medium article: ...
0
votes
1answer
325 views
How to find function start in stripped binary?
Given C code, are the function addresses from the ELF the same as those in the stripped version?
I don't have any specific code in mind. Just trying to learn in general how to find the function ...
1
vote
1answer
110 views
how could i follow a system call from a dll -> kernel driver syscall
basically i would like to follow (system calls / internal calls) that basically lands in the kernel i would like for example to debug a specific dll ex : ntdll.dll and follow it to (NtXXX) function ...
2
votes
3answers
102 views
Intercepting game function with C and Assembler, game unstable with minimum changes
I am reverse engeneering a really old game (Mu 97d) for the sake of adding new things to the game.
What I am doing is intercepting the game with a DLL, and in the DLL do the calculations so I can add ...
1
vote
0answers
282 views
which has better pseudocode? IDA or Ghidra [closed]
I would like to know which of the two has a better pseudo code generator in C, IDA or Ghidra, if possible, point out the strengths and low points of each one.
1
vote
1answer
120 views
Is Ghidra's decompilation of ARMv7 strb.w instruction broken?
I'm currently disassembling some firmware, when I stumbled across the following code snippet produced by Ghidra (the names are already my own ones):
void memset(byte *addr,byte value,int count)
...
2
votes
2answers
108 views
Newbie problems exploiting a format string vulnerability
I encountered a print format vulnerability challenge in a CTF. I don't know anything about these vulnerabilities, so I'm working my way through Saif El-Sherei's format string exploitation tutorial ...
1
vote
2answers
525 views
Simple angr example not working
I am trying to learn angr from beginning. Due to lack of simple tutorials I programmed my own little executable which angr should solve.
The C code looks as follows:
#include <stdio.h>
#...
