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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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123 votes
2 answers
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How to handle stripped binaries with GDB? No source, no symbols and GDB only shows addresses?

I have GDB but the binary I want to reverse engineer dynamically has no symbols. That is, when I run the file utility it shows me stripped: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), ...
0xC0000022L's user avatar
  • 10.9k
87 votes
3 answers
133k views

How are the segment registers (fs, gs, cs, ss, ds, es) used in Linux?

I try to understand the process of memory segmentation for the i386 and amd64 architectures on Linux. It seems that this is heavily related to the segment registers %fs, %gs, %cs, %ss, %ds, %es. Can ...
perror's user avatar
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48 votes
8 answers
34k views

How do I add functionality to an existing binary executable?

I want to add some functionality to an existing binary file. The binary file was created using gcc. Do I need to decompile the binary first, even though I sufficiently understand the functioning of ...
asheeshr's user avatar
  • 2,465
37 votes
5 answers
11k views

How can I analyse an executable with no read permission?

I have a binary on a Linux (Kernel 2.6) which I can execute, but can't read (chmod 0711). Therefore no static analysis is possible. user1: $ ls -l bin -r-s--x--- user2 user1 bin user1: $ file bin ...
samuirai's user avatar
  • 3,079
31 votes
5 answers
57k views

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 ...
k170's user avatar
  • 453
23 votes
2 answers
15k views

How to reverse engineer simple usb device [windows -> linux]

I'd like to reverse engineer my usb beer-can refrigurator, which does connect via USB on windows and via simple GUI tray-tool can set/query temperature. I was thinking about running virtualboxed ...
AoeAoe's user avatar
  • 231
22 votes
3 answers
19k views

Detecting tracing in Linux

Under Linux it's possible to trace exactly the kernel system calls with strace. ltrace can be used also to trace library calls. I wonder if it's possible to detect if my executable is running under ...
Mellowcandle's user avatar
  • 4,825
20 votes
2 answers
37k views

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 ...
perror's user avatar
  • 19.1k
20 votes
2 answers
6k views

Why are GOT and PLT still present in Linux static stripped binaries?

I am looking at statically linked linux x86 stripped binary. I noticed that there are .got and .plt sections. I wonder what does a statically linked binary need got and plt sections for ? Anyone ?
daehee's user avatar
  • 603
18 votes
4 answers
180k views

Converting assembly code to c

I have the following assembly code over Linux distro: # using the .data section for write permission # instead of .text section .section .data .globl _start _start: # displaying some characters ...
MLSC's user avatar
  • 331
18 votes
1 answer
5k views

Debugging with radare2 using two terminals

I have been trying to figure this out for quite some time now, and would really need some help. Firstly, some intro: I am running the newest version of radare2 from Github on a 64bit Ubuntu 16.04 and ...
ubnix's user avatar
  • 1,073
13 votes
3 answers
11k views

Locating Linux Kernel Symbols on ARM

Igor posted a great answer previously on SO about the format of the Linux kernel image on ARM. Assuming I can't boot my kernel image, can someone give me pointers on finding this compressed symbol ...
mrduclaw's user avatar
  • 4,066
12 votes
2 answers
12k views

How does glibc malloc work?

Wishing to dig in the internals of dynamic memory allocation on Linux, the best I could find is an article titled Understanding glibc malloc. The explanation, though detailed, is not quite ...
sherlock's user avatar
  • 1,381
12 votes
3 answers
4k views

Hooking functions in Linux and/or OSX?

I want to hook functions in a library (lib.so or lib.dylib) from another process. I know that unlike windows libraries, libraries in Linux and Mac still have their symbols (function names and ...
TerryW's user avatar
  • 121
12 votes
1 answer
5k views

How are stripped shared libraries linked against?

Lately I've been reversing the Android framework for the Nexus S mobile phone. 99% of the source code is of course open, but there are few propriety shared libraries which needs to be downloaded in ...
Mellowcandle's user avatar
  • 4,825
12 votes
1 answer
5k views

Understanding the most recent heap implementation under Linux

A few days ago, I was wondering how one could teach himself heap-based overflow exploitation. So I searched through documentation, subsequently practicing what I read in order to have a better ...
Geoffrey R.'s user avatar
11 votes
4 answers
8k views

How can I generate a call graph from an unstripped x86 Linux ELF?

There's a piece of software, for which I only have the binary, not the source code. It's: unobfuscated (so, not polymorphic or anything. It is optimized a bit, though) unstripped x86 32 bit ...
Parthian Shot's user avatar
11 votes
3 answers
24k views

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 ...
J91321's user avatar
  • 271
11 votes
1 answer
20k views

Setting a breakpoint at system call

I want to modify my teamspeak server (linux), I'm particulary interested in the connection with clients (UDP), so I figured I need to set a breakpoint at the linux socket function to start reversing. ...
Hugo Kiiski's user avatar
11 votes
2 answers
16k views

Which python library for parsing Linux ELF files?

I want to be able to parse 32 and 64 bit ELF files - but not create or modify them (e.g. as discussed in this thread). The ELF binaries may possibly come from embedded Linux systems, that is, the ...
langlauf.io's user avatar
  • 1,560
10 votes
3 answers
5k views

Why does the function pointer get overwritten even though is declared before the vulnerable buffer?

I am working on io-wargames for fun right now, level3: I do understand why there is a stack-overflow in this code (strlen(argv[1])), but what I don't understand is why it overflows the function ...
0x90's user avatar
  • 677
10 votes
2 answers
21k views

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 ...
merrychap's user avatar
  • 103
10 votes
2 answers
3k views

Attaching GDB to a specific fork

I am trying to reverse engineer a Linux binary that makes several fork() calls. I am using GDB 7.5 on Ubuntu. What I am trying to do with GDB is attach to a certain fork() (say the second call). Is ...
Compster's user avatar
  • 369
10 votes
1 answer
5k views

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 ...
Brandon Bryant's user avatar
10 votes
4 answers
4k views

How can I get a running thread's start address on linux?

Problem Statement I'm trying to get the address of a running thread's start_routine as passed in the pthread_create() call. Research so far It is apparently not in /proc/[tid]/stat or /proc/[tid]/...
user2804197's user avatar
9 votes
2 answers
27k views

How to reverse engineer a Linux executable to find the parameters? [closed]

So I am on a Linux box with an executable.Vague - I know. This is what happens when I try and run it with an argument/parameter: me@there:~$ ./theFile theOption -a ./theFile : option requires an ...
pee2pee's user avatar
  • 221
9 votes
2 answers
16k views

Why does `ldd` and `(gdb) info sharedlibrary` show a different library base address?

I see three different outputs for where libc should be loaded. ldd shows the loading address of libc at 0xf7e9e000 $ ldd ~/my_tool linux-gate.so.1 => (0xf7ffe000) libc.so.6 => /lib/...
samuirai's user avatar
  • 3,079
9 votes
3 answers
3k views

Did somebody start to reverse engineer the proprietary Linux Brother Cups drivers?

I'm not very experienced with graphic or printer formats. My first (and only try yet) was to print a Tux.png with 265 x 314 pixel via the Chromium browser and see what Wireshark shows as USB transfer. ...
Sven's user avatar
  • 191
9 votes
1 answer
948 views

Understanding segment prefixes in assembly for Linux

In looking at some assembly, I have come across a few instructions using segment prefixes. For example <address>: .... mov eax,DWORD PTR gs:0x20 I understand the basics of memory segments, ...
HenryC's user avatar
  • 91
9 votes
2 answers
10k 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 ...
stacksmasher's user avatar
9 votes
1 answer
8k views

How to unpack manually an upx packed elf file

I am trying to learn to manually unpack an upx packed elf file. The examples I have found are for Windows, mostly with Ollydbg, and as I see the first step is to look for pushad and popad instructions....
robert's user avatar
  • 887
8 votes
4 answers
15k views

How to check if an ELF file is UPX packed?

I have an ELF file and want to know if it is UPX packed. How can I detect UPX compression in GNU/Linux?
qbi's user avatar
  • 527
8 votes
2 answers
6k views

Base address of shared objects from ldd output

I'm on a Linux machine with ASLR disabled. Running ldd on a binary gives me the following result : linux-gate.so.1 => (0xb7fe1000) libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7e5c000) /lib/...
user avatar
8 votes
1 answer
907 views

Why are values passed through useless copies?

So, say that I have the following code, which gives three examples of what I believe to be unnecessary copies of values. mov QWORD PTR [rbp-0x18],rdi mov rdx,QWORD PTR [rbp-0x18] lea rax,[...
David's user avatar
  • 285
8 votes
2 answers
14k views

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, ...
Rohit saraf's user avatar
8 votes
3 answers
1k 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 ...
Cyrax's user avatar
  • 81
7 votes
2 answers
344 views

How should I go about trying to figure out the programming language that was used?

I have an executable file and I would like to figure out which programming language was the source code written in. The first step would be to use a disassembler. What should be done after that ? ...
asheeshr's user avatar
  • 2,465
7 votes
3 answers
7k views

unpack Clear spot .bin firmware update

I am trying to unpack a clear spot firmware update The firmware I am trying to reverse can be found on the download page of the vendor I have used the fwtools to unpack the firmware as described on ...
Ahmed Rhuma's user avatar
7 votes
3 answers
4k views

Debugging forked child in an anti-debug protected crackme

I am interested in the anti-debugging method implemented in the crackme called trace-p. A child process is forked, which communicates with the parent using int3 instructions. I would like to debug the ...
robert's user avatar
  • 887
7 votes
1 answer
435 views

How can I check I've moved outside the stack without triggering a protection fault?

I'm adding a feature to my Linux debugger (I'm using Ptrace to manipulate the traced process as well as libbfd/libopcodes) to unwind the stack and determine if discrepancies exist between each CALL's ...
zetavolt's user avatar
  • 1,213
7 votes
1 answer
2k views

How does API call work on Android (NDK)?

In windows platform, an application usually references its IAT(Import Access Table) to get the address of the APIs it wants, then call it. Then some mechanisms are done as demonstrated here nicely. ...
Hyeonseo Yang's user avatar
7 votes
1 answer
2k views

Calling fgets while debugging under IDA Linux

I have _fgets call in a program I want to debug in IDA. My program receives SIGTTIN while calling it, that's normal. But when I mark to pass SIGTTIN to application, program waits for input in terminal,...
michaeluskov's user avatar
7 votes
2 answers
3k views

32-bit binary stack layout on a x64 Linux OS

Stack layout is well documented in many ways. Especially for x86 systems as there were numerous tutorials on how to exploit stack overflow on old 32-bit systems many years ago. So far we can know ...
Geoffrey R.'s user avatar
6 votes
3 answers
6k views

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 ...
Vido's user avatar
  • 515
6 votes
3 answers
2k views

Reversing self-modifying code

I am learning reversing an I am studying a code, which modifies itself (actually it is a crackme). It contains statements like: movw $0xc031, 0x(%edx), where edx contains the address of a statement. ...
robert's user avatar
  • 887
6 votes
1 answer
5k views

Why are symbols with local binding present in the symbol table of my ELF files?

I found out that there are symbols with binding=LOCAL and visibility=HIDDEN in the symbol table (.symtab) of ELF executables/libraries. What are they needed for? They are not involved in the ...
user19496's user avatar
6 votes
3 answers
12k views

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, ...
user avatar
6 votes
1 answer
5k views

Why have two symbols tables?

Why have two symbol tables if .symtab already contains everything that's in .dynsym ?
Itra's user avatar
  • 85
6 votes
2 answers
8k views

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

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 to segfault. It should ...
ker2x's user avatar
  • 173
6 votes
3 answers
9k views

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 ...
0xfede7c8's user avatar
  • 243

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