Questions tagged [linux]

A free and open source POSIX compatible operating system with a monolithic kernel and a kernel module system. Originally created by Linus Torvalds.

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Modifying a legacy uImage

I have an old device from which I extracted a uImage. I know it has a linux kernel and a cpio filesystem in the uImage, and I need to make some changes to the filesystem. I'm hoping someone can help ...
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Format of Alcatel_Lucent I-240W-A backup file

I am trying to modify the backup file of this router in order to change some configurations. Here is the structure I have until now: 16 bytes of the header, zlib compressed xml with the ...
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Address of calling syscall

With strace I can see all syscall that process call. Is there any way to know witch address of process call to this syscall?
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How to see assembly of main function?

How can I dump the assembly of main function of binary(not striped) in ubuntu? I want to see the assembly command and the hex value of this command There are 1 binary for arm and 1 binary for x86
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Performing Buffer overflow in Linux

I have buffer overflow in a program i check(it is an array of pointers, and i can overflow the data in the first pointer), but the data i can write is not on the stack, it is on a space the system ...
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38 views

Protected shell in embedded linux

When I run telnetd -l /bin/sh on an embedded Linux device and use Putty to telnet to it, the provided shell is /bin/psh (protected shell). On this device, /bin/sh is a symbolic link to /bin/busybox. ...
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IDA shows MEMORY or unknown references on C std library calls (memset, memcpy, etc.)

I'm currently reversing a Linux 32-bit executable (with a statically linked library included in it) but I'm having a little problem I can't find a solution for. Basically whenever I stumble across a ...
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Linux encryption/luks/pymouth password scripts corruption

I noticed that the bootup scripts that collect the password for full disk encryption on linux (fedora-31) were displaying corrupted text. The kind that looked like binary data being printed at text: ...
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The buffer is too short to insert addresses when exploiting buffer overflow

Newbie here. Sorry for what you about to read . I'm currently working on exploiting a binary on Ubuntu 18.04. Here is some information about the binary: Its checksec information using pwntools: ...
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1answer
92 views

ildasm on Linux: “original” ildasm.exe same as dotnet-ildasm?

I would like to use ildasm on Linux. The original one, that comes with the .NET SDK and can be found on Windows e.g. at c:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\. I ...
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Extract files of a SquashFS Filesystem

I already asked a similar question but after a deeper analysis of the filesystem I found out that I misunderstood the problem and that's why I decided to delete the old question and make a new one. I ...
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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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reverse engineering hi3516ev200

I am new to reverse engineering and will describe my situation thus far. In short, I am looking for some tips on what to do next to gain access to a piece of hardware I am playing with. I bought a ...
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Capturing traffic of an integrated laptop keyboard

I'm trying to capture the traffic between my laptop's integrated keyboard and its controlling software on Windows. I'll analyze the traffic to write a driver for Linux to control keyboard backlight. I ...
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3answers
56 views

How to input ascii control character into program?

I am working on a CTF where I need to pass an address as input to a program. This address contains the value 0x09 (the tab character). This is causing me problems, because it seems that bash is ...
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1answer
63 views

`qemu-mips-static` chroot causing `Invalid ELF image` error

I'm trying to emulate a MIPS binary on my Ubuntu 16.04 x86 system, but I'm not able to. I chroot into the squashfs-root filesystem that I got from binwalking the firmware image. kan3k1@kaido:~/...
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submitting input into AFL fuzzer

I have some questions about the AFL Fuzzer: How does the AFL Fuzzer know where to inject the payload in the code I compile? For instance if I want to inject it in a specific parameter, how do I do it?...
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2answers
144 views

Prevent Memory Inspection in a Cython program?

Cython is a great way to protect the source code of a Python program. However, memory inspection and memory reverse engineering can still be done to this Cython program. What are ways to prevent (or ...
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1answer
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IAT vs GOT address resolving: which of them resolve during runtime and which during load time by default?

So based on my knowledge on windows apps, as far as i know the IAT gets filled with correct addresses when the library gets loaded (correct me if I'm wrong) now in linux, they use GOT, and again ...
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1answer
86 views

Unknown archive format from QNX operating system

We are reverse engineering a QNX system and we have found a small file that is uploaded to the system. It appears to be either a file system image or an uncompressed archive of some sort. We can't ...
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1answer
142 views

Reverse getline(cin, text)

I'm trying to solve a crackme that was made in C++, and I was able to "recreate" a function call, through the library calls the program made. Here's the piece of code that I'm trying to reverse: ...
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262 views

Extracting firmware image from binary

I have firmware file in .bin format, but I need get firmware.img image file and Kernel uImage file for reflashing bricked device. How can I get these parts? I used Binwalk to extract content, ...
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1answer
216 views

Radare2 ptrace can not attach

First my setup: Linux Mint 64bit 4.15.0-20-generic radare2 the newest version from github /etc/sysctl.d/10-ptrace.conf = 0 Executable: ELF 64-bit LSB executable, x86-64 read write and ...
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553 views

how to flash image.bin with uboot using serial or tftp

Hello I have a 4G LTE router which is blocked. and I have already dumped the partitions before via telnet from another device of the same model. U-Boot 2010.09 (Sep 06 2016 - 10:08:39)GCT GDM7243 ...
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1answer
356 views

How to do debug a running java process in linux?

TLDR I want to do live debugging of a java program on a linux machine, and don't how/what debugger to attach to the JVM to get this done. I expect that this is a well-solved problem, but I lack the ...
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Unable to exploit format string vulenrability on Ubuntu 18.04.2 LTS

I am studying from "Hacking: The Art of Exploitation" and in program fmt_vuln.c format string is exploited. I am getting Segmentation Fault error. Checking position of AAAA on stack: $ ./fmt_vuln ...
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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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1answer
72 views

What is actually loaded here and different hexdump outputs on util-linux hexdump and on cutter and ghidra's hexdump

I was trying to understand what segment of file gets loaded by fourth LOAD header on phdr array. First 6 headers are shown below from readelf Program Headers: Type Offset ...
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1answer
134 views

Why have two symbols tables?

Why have two symbol tables if .symtab already contains everything that's in .dynsym ?
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2answers
378 views

How can I pass input to my program while debugging it with IDA

I have a program that waits for the user to enter a string input, how can I enter that string input while debugging my program with IDA?
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401 views

Can i trap SIGSEGV (on a linux) and what are are the conditions to make it works ? (for a crackme)

Friendly greetings ! I'm writing some crackmes.one challenge and i want to write a challenge where the solution appears on a segmentation fault. (And you have to disassemble the code to find a way ...
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1answer
193 views

Unexpected SEGFAULT when there's apparently nothing that would cause it

This is a from a CTF problem I'm working on. Hopefully it's appropriate to ask this question here. Above is the GDB output when the segfault goes off. movaps is the offending instruction, meaning ...
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1answer
117 views

Understand what Ioctl do

I looking in ida on arm linux binary . I can see there that there is ioctl call ioctl(fd,req,num). fd is fd to /dev/module. ,req is some 4bytes and num is some number. How can I understand what ...
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311 views

Changing entry-point of and ELF file

I'm trying to conduct a little experiment which basically consists of changing the EP of an ELF file and executing an exit(9) syscall, without returning to the OEP. As shown in the image everything ...
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1answer
43 views

Find out if address store in heap or stack

While dynamic debugging with ida and gdb-server on binary file running on linux , I saw address that store some value. How can I know if this address allocated in stack or in heap?
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Sniffing TCP packets using Wireshark

I am trying to reverse engineer a decoder. The decoder contains a web server that makes sending/receiving information through the Internet possible. To do so I need to sniff the packets that the ...
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57 views

IDA remote debugging - non printable characters in parameters

I am trying to remote debug a certain binary which gets user-specified command line arguments, which can be non-printable of course. My goal is the ability to debug with IDA the process with the ...
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1answer
289 views

Help needed to extract u-boot kernel & rootfs - nxp lpc 3143 processor

I have a board where in principle aim at emulating a DVD-ROM loading iso file from a drive. This board is running a ARM CPU with 32MB of ram and has no vga output. The firmware update comes with 2 ...
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Stack trace with GdbServer

When I debug binary file on linux with gdbServer with Ida ,I don't see stack trace. Why? How can I fix it to see stack trace??
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1answer
411 views

Lipo alternate for linux

Currently, I'm using lipo tool to extract the arch type from a fat iOS binary on a Mac OS. Now, I want to do the same on the linux platform for the iOS binaries, i.e. extract a given arch type from a ...
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Decrypt ibt.sfi linux firmware(Intel Wireless 8265 Linux Bluetooth)

Why I want to decrypt: Intel 8265 Bluetooth is likely a RAMUSB device, which needs system to update firmware. I try to transplant this linux firmware to macOS. Problems I met: The macOS BT firmware ...
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33 views

What is causing \r\n in libnotify? [closed]

I am trying to look under the hood of libnotify, and ran strace notify-send 'hello' and one of the system calls is: sendto(5, "AUTH\r\n", 6, MSG_NOSIGNAL, NULL, 0) = 6 Surrounded by a: sendmsg(5, {...
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1answer
217 views

Fork and Waitpid calls in a CTF linux binary

I'm doing one of my first linux crackmes. In the first blocks of code, it goes inside some anti-debug routine and inside one of those it forks and after it calls a waitpid routine. I can verify it ...
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343 views

why saved rip changed by push?

I am doing a reverse homework. see the following pictures: as can be seen from this picture, before call push touch3, "saved rip" is at 0x5561dca8, which is equal to the current rsp(0x5561dca8). ...
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OTOOL alternative for linux

I have a reverse engineering set up on a Mac machine. This set up does some reverse engineering on iOS applications(.ipa files). I'm migrating the setup from Mac to a linux machine. Currently on Mac, ...
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71 views

Significance of link address 2000 8000 7C00;

Can you explain to me the significance of link address 2000 8000 7C00? It's in a MACRO from the GRUB configure script, which checks whether OBJCOPY works for absolute addresses. Here's the snippet ...
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79 views

Process Immediately Killed

I'm trying to reverse an ARM executable. It's for an embedded system, but I don't have any details about the normally targeted environment. Here's what file shows: ELF 32-bit LSB executable, ARM, ...
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67 views

Unknown parameters in custom signal handler on Linux

0x0000000008001946: mov 0xa8(%rdx),%rax 0x000000000800194d: lea 0x28(%rdx),%rsi 0x0000000008001951: lea 0x2(%rax),%rdi 0x0000000008001955: add $0xe,%rax 0x0000000008001959: ...
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1answer
148 views

Remote debugger for Linux from one VM (IDA) to another (running the debuggee)

I want to debug a Linux program (ELF), but my IDA Pro is on a Windows 10 VM and I want to use remote debugging to debug the program on Ubuntu (also in a VM). So, is it possible to debug if both ...
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137 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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