Questions tagged [gdb]

A source level debugger based on `ptrace` for *NIX systems and developed by the GNU project.

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How to call to function while debug

When I debugging remote process with gdb-server and Ida, and put breakpoint in the code, when the process stopped at this breakpoint how can I call to function and after that return to my code ?
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41 views

How can I get my shellcode to work outside of GDB?

I'm working inside a Warzone VM with no ALSR or NX bit. The program I'm trying to exploit is really simple: #include <stdlib.h> #include <stdio.h> #include <string.h> /* * ...
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GDB exited when running library

I'm new with gdb and I have spent hours looking for direction but I can't find any. I need to analyze an executable to find how this program process the arguments and where the output came from. I ...
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Help explain warning messages when running gdb

[System: mac mojave 10.14.6, gdb 9.1 installed via brew] I have recently installed gdb and am a newb user. After many hours of searching, I got it working by following the instructions from https://...
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Debug process that use /dev/watchdog

I want to debug a process with gdb, but the problem is that process pings /dev/watchdog so when I tried to debug it, it stop the process for longer than the watchdog interval so the system is ...
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Is address in program can change

I talking about linux arch. When I open program in Ida (statically ) I can see all instructions address like 0x20da mov r8 r2 When I want use that address to breakpoint (for example with ptrace or ...
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1answer
43 views

How to detect which shared libraries a binary is actually using?

I have a stripped-down Linux-based embedded system where a closed-source program(32-bit ELF binary for MIPS) depends on several shared libraries. Two of those libraries are actually the same libcurl ...
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How to debug with gdb (rbreak) in order to obtain a callback to be used on C# interop

Well, I have several questions about this topic. I don't know if I'm using the right method to achieve what I need. I need to debug which exact method does something inside a process in order to ...
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33 views

Parsing C header files from DWARF Debug File

I have a Linux executable that has a linked .debug file containing DWARF debug info and I would like to find a way to parse C headers for types defined in the executable. Using gdb and ptype I can ...
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1answer
30 views

GDB disassembly - breakpoint problem

My question is, when i dont use any breakpoint it show the message saying "You made it, now keygen me!", but when i put a breakpoint in the main, or any other place it will show a message about ...
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1answer
33 views

Why does this x64 stack have other bytes and seems to be in reverse order?

I wrote the following small C program and you can also see the stack in the screenshot. My question is twofold: How come there are entire rows of other data between the 3 stack strings? Why is my ...
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1answer
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ASLR and it's effect

I was debugging some programs with gdb, I already set the disable-randomization to on, but I was having trouble, I set a break point and examined that the $sp is different everytime, what causes this ...
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1answer
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GDB - Send Python output to the program after SIGINT

I am trying to learn GDB to better understand buffer overflows but I can't find an answer to my problem which is how can I send a Python-generated output to the program when the program asks for user ...
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compile gdb with python 3 for gef-ida-interact

I'm trying to use GEF's IDA-interact which has issues with python2. I'm using android-ndk-r20b/prebuilt/linux-x86_64/bin/gdb - v7.11 using Python engine 2.7 How do I compile gdb with python 3.x ? I ...
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1answer
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How can I debug open source C code for Linux?

I want to debug & reverse engineer open source code such as this project. I usually use CLion to write and debug C code on Linux. I've also used GDB. What steps do I need to take to download a ...
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Using Gdb-Server with Ida 7.4 failed

I have gdb-server to arm , downloded from https://github.com/therealsaumil/static-arm-bins/blob/master/gdbserver-armel-static-8.0.1. When I use Ida 6.6 to connect remotly to this gdb-server that work ...
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1answer
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Why is there no call to strcpy in assembly?

I try to better understand assembly and currently playing around with some compiled c snippets. I have the following snippet: #include <stdio.h> #include <string.h> int main() { char ...
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1answer
108 views

Dumping the GOT with gdb at run time

I want to see how the plt stubs are being resolved at run time when lazy linking is used and how the GOT is changed along the way. How can I dump the GOT with gdb?
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GDB hangs when I try to run and debug a binary

When I type gdb a.out and then run inside the gdb itself I get stuck on the empty line: jericho-laptop:exploit.education jericho$ gdb a.out GNU gdb (GDB) 9.1 ... Reading symbols from a.out... (No ...
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Disassembly - First steps

I decided that I need to understand this more thoroughly, so am working in parallel with two resources: one more modern and one original from @Aleph1. In the essay, there is a basic code snippet, ...
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1answer
135 views

IDA Pro ignores condition in breakpoint

Look at the condition. It is supposed to break only when the R2 is 40, but it breaks in any call to this instruction. I'm using IDA Pro 7.2.181105, debugging with Remote GDB Debugger, an ARMv4T code. ...
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Debug only one thread with ida-gdb server

If I want to debug process in embedded that running linux , I can run gdb-server in embedded and attach to process with Ida. The problem is if this process has 1 thread that can't stop over than x ...
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1answer
73 views

Arrangement of variables on the stack - out of order?

I was practicing some reverse engineering crack-mes as part of our university curriculum, and I have a question around the arrangement of variables on the stack. I have a very basic C++ code, like ...
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1answer
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What's wrong with my mitm to support rr commands with gdbserver on IDA?

First of here is the gdb remote protocol doc. The idea of the below script is the following - you enter an actual command (one that will be send as a direct packet see packets) in the gdb window then ...
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2answers
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gdb shows that EBP contains a value other than some address(which is what it is supposed to contain). How is this possible?

I am fairly new to RE and Binary Exploitation, I have learned basic assembly instructions for Binary Exploitation and I was doing Protostar exercises (stack0) in which I have to simply overflow the ...
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<error sending command to monitor>

I'm trying to debug a backtrace created with rr so I type: rr replay -s 50505 -k it displays out: gdb '-l' '10000' '-ex' 'set sysroot /' '-ex' 'target extended-remote 127.0.0.1:50505' target Then ...
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Strange behaviour debugging Android ARM binary with gdbserver

I'm trying to run this armv5 binary from OWASP's mobile security guide (validate) using Android Studio's emulator on my x86_64 machine. I'm seeing very weird behaviour and would appreciate any ...
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1answer
119 views

Breakpoint in GDB hit 144 times before first call to function

I am working on a reverse engineering challenge and have a binary file. I know how to get the flag by changing the instruction flow after doing a strcmp so I jump to the function that prints the flag....
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1answer
260 views

How to decrypt the password using radare2 or gdb?

.--------------------------------------------------. | [0x804851b] | ...
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1k views

Use GCC and objdump to disassemble any hex to assembly code

What would be the best way (also fewer steps) to generate assembly code for a given hex code ? For e.g., if we know the architecture is x86, and given hex value 0x55, what is the best way to generate ...
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1answer
214 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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1answer
138 views

Why EIP is being overwritten before local buffer ends?

I am doing a simple buffer overflow exercise, here is the source: //vuln.c #include <stdio.h> #include <string.h> int main(int argc, char* argv[]) { char buf[256]; strcpy(buf,...
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1answer
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How to set breakpoint with gdb on arbitrary memory location?

I'm trying to debug some code on Linux. There's an arbitrary memory location I need the program to jump to. This location is result of calling mmap with appropriate protection flags for executing a ...
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94 views

How to change operator by GDB?

How can I change je to jne via GDB tooL?
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Examining Stack Frame in GDB

I am learning exploitation from the book "Hacking: The Art of Exploitation". In the program an integer variable auth_flag is declared after a char array password_buffer. So on stack frame first ...
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1answer
47 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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2answers
238 views

eip register address not matching with address at breakpoint (breakpoint set at main function)

I recently started reading a book about reverse engineering. In one of the examples it uses gdb (debugger) to disassemble the main. So I did it, and the output is below (gdb) disass main Dump of ...
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0answers
202 views

gdb - searching for pointers to a given memory region

Let's suppose there is a memory region that is m'mapped in memory, we need to find its address (which randomly changes, because of ASLR) by following a pointer path, basically, I'm trying to find a ...
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R13 off by 2 bytes. Any help?

in this challenge i have to overwrite RIP register to point to the function "print_flags" which calls "getenv" to get the "FLAGS" variable. I have overwritten RIP register with the address of "...
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Reversing ELF 64-bit LSB pie executable [duplicate]

I have a file crackme, which is an executable. hamuto@hamuto-pc:~/Security/NOOB/FruitSalad$ file crackme crackme: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, ...
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1answer
125 views

radare2 shows main function arguments argv as pointer to char on the stack, not as pointer to pointer to char

Well, I've been digging around process command line arguments as well as environment variables a bit these last days, especially looking up the way main function arguments were pushed onto the stack. ...
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340 views

Illegal instruction fault in stack based buffer overflow

I wrote this short C program to practice buffer overflow exploits: #include <stdio.h> #include <string.h> #include <stddef.h> #include <inttypes.h> char *decode(char *s){ ...
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How to debug programs that load from another one? with radare2/gdb

I'm reversing engendering a plugin. This plugin is loaded into memory by the main program. I disassemble the plugin with radare2 but I don't know how to debug it. I try with gdb but same problem. I ...
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198 views

Using GDB to trace guest OS inside a hypervisor, the whole running on Qemu - kvm

I use Gdb to trace the execution (breakpoint, single stepping, ...) of a hypervisor OS in Qemu and it works fine so far. qemu-system-x86_64 -enable-kvm -display sdl -cpu host -serial my: stdio -m ...
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1answer
137 views

GUARD_PAGE memory breakpoints with gdb?

I came across a question the other day on reddit: How can we use PAGE_GUARD-based memory breakpoints in GDB (not hardware breakpoints)? Ollydbg, x64dbg and IDA PRO all support these types of ...
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1answer
215 views

how watchpoint on register works

GDB has an option to set watchpoint on register*, how does it work ? what happens during context switching ? why the only implementation is for mips ? Is there a way to make it work for lldb also ? *...
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1answer
1k views

GDB: Could not load shared library symbols

I'm currently having a look at the Damn Vulnerable Router Firmware, and I'm roughly following the description that is given here: https://p16.praetorian.com/blog/getting-started-with-damn-vulnerable-...
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1answer
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DT_DEBUG not filled on dlopen [closed]

A target library "lib42.so" has DT_DEBUG entry in the .dynamic section. After dlopen("lib42.so", RTLD_LOCAL | RTLD_NOW) succeded, r_debug->d_un.d_ptr is equal to zero. Why?
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1answer
440 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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How to use “handle SIGILL nostop noprint” with a gdbserver?

I have a program linked against libcrypto.so. If i run the program in gdb i'll get the following error: "Program received signal SIGILL, Illegal instruction." I researched a bit and found out that it ...

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