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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Basic shellcode doesn't work when read from stdin

I am working on a basic shellcode that will spawn a shell after getting called in a 32-bit program. Here is the shellcode i'm using: xor %eax,%eax push %eax push $0x68732f2f push $...
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538 views

Is there a way to debug an elf file that runs with no problems with damaged header?

My question is general, but to have an example to work with, let us take one from Whirlwind Tutorial. ; tiny.asm BITS 32 org 0x00010000 db 0x7F, "ELF" ; ...
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Changing local variable in caller from callee in C?

I'm implementing a function which is going to perform some time-consuming task, and I'd like to hack the benchmarking part a bit by changing the variable indicating the CPU time my function has ...
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1answer
70 views

Reverse getline(cin, text)

Sup, guys. 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 ...
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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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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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210 views

mprotect syscall not working

I want to modify the protection of the .text segment to RWX using a shellcode. In the shellcode, I can issue the syscall for mprotect however it's not working. Per the sys_mprotect definition, it ...
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273 views

Extracted router file execution

I am trying to run an executable file that I dug out from an extracted file system of a DSL modem router. So first of all I needed to either have a MIPS Linux box or take the emulation path. After ...
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TP-Link encrypted backup file TX-VG1530

I have been trying to wrap my head round this stuff so bear with me. I have a Tp-Link TX-VG1530. From the gui you can download the config file however the file is encrypted, I include a portion of ...
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1answer
256 views

Mechanisms to stop serial console accepting input on a Linux system?

I am working on a simple embedded system based around an Olinuxino board. This has a serial console header onboard. TX and RX are both connected to the respective pins on the microcontroller (i.e. ...
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3answers
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How to SUCCESSFULLY add a code section to an executable file in Linux?

I am in Linux, and I have seen this question a few times but never, nobody answered how to really make this work. I need to add a section to an already compiled binary. Lets say for a moment is an ...
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3answers
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Packers/Protectors for Linux

I was wondering if anyone had come across a packer/protector which could be used for ELF binaries. There seem to be quite a few articles on writing packers and protectors for the PE format -- however, ...
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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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1answer
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how to flash image.bin with uboot using serial or tftp

Hello I have a 4G LTE router which is blocked. I have access to its serial interface and I have already dumped the partitions before via telnet from another device of the same model. Here's the ...
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1answer
230 views

Cannot open '/proc/…/maps': No such file or directory in radare2 debug mode

When I try to load a program to radare2 debug mode, most of the time I get the following error: $sudo r2 -d a.out Hello world!= attach 2851 2851 Cannot open '/proc/2851/maps': No such file or ...
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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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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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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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RE Compressed backup file,router linux based so is it compresed with zlib?

so I have backup from my router its zte zxv10h201l and its linux based but I can not identify type of compression of this file. Here is couple of first "lines" of it 00000000 99 99 99 99 44 44 44 ...
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Why have two symbols tables?

Why have two symbol tables if .symtab already contains everything that's in .dynsym ?
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3answers
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Linux protectors: any good one out there?

I know no one that works as of today (i.e., kernels not way too old) and I wonder if anybody found or knows any protector for Linux either commercial, open source, used in malware, etc...
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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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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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1answer
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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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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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1answer
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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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Adding additional language to Linux based Firmware of Volkswagen Car Radio

I'm owning a CarPlay head unit from Volkswagen called RCD330 plus. It is possible to upgrade/downgrade to any available firmwares. For example here are two firmware versions: http://rcd330plus.com/rcd/...
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What is the linux equivalent to OllyDbg and Ida Pro?

What is the Linux equivalent to OllyDbg and IDA Pro ? Or if there are multiple tools that do the various functions that OllyDbg and IDA Pro do, where can I find these tools? I'd like to start ...
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1answer
41 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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1answer
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Reverse Engineering ZyXel C1100Z modem firmware

first time post so please bear with me. For days I have been trying to bypass a password my ISP has added to their remote CLI with no luck. I have a Zyxel C1100Z DSL modem that I've purchased from ...
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2answers
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ZTE encrypted backup config file

I was poking around in ZTE Speedport Entry 2i (CPE used mostly in Germany, Slovakia etc, probably custom made for Deutsche Telekom). It's possible to download backup of config from UI. I found out ...
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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
185 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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0answers
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How to set-up GDB debugging in IDA Pro on Linux via Wine?

I tried running on linux via root terminal: gdbserver --multi localhost:23947 And then at IDA Pro at Wine I use Remote GDB debugger with my local ip and port: However when I start debugging I think ...
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ARM64 syscalls table

I wonder if there some syscall table for Linux ARM64 architecture? I found syscall table for Linux ARM32 and many other architectures, but the problem still exists. Does anyone know where can I find ...
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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
246 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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1answer
32 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
147 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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1answer
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Managing inputs for payload injection?

I am looking for a complete list of the ways to inject a payload in a vulnerable program in a Unix (Linux) context depending on the inputs opened by the program. I know that there are several tricks ...
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1answer
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How does this version of `rm -rf /` work?

On this website, I found the following code: char esp[] __attribute__ ((section(”.text”))) /* e.s.p release */ = “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68\" “\xff\xff\xff\xff\x68\xdf\xd0\xdf\...
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1answer
186 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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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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1answer
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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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1answer
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Unpacking firmware

I have a ROM dump firmware which must be reversed (as a task). Binwalk output: DECIMAL HEXADECIMAL DESCRIPTION -------------------------------------------------------------------------------...
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1answer
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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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1answer
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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: ...