hacktricks/reversing-and-exploiting/linux-exploiting-basic-esp/one-gadget.md

# One Gadget

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## Basic Information

[**One Gadget**](https://github.com/david942j/one\_gadget) allows to obtain a shell instead of using **system** and **"/bin/sh". One Gadget** will find inside the libc library some way to obtain a shell (`execve("/bin/sh")`) using just one **address**.\
However, normally there are some constrains, the most common ones and easy to avoid are like `[rsp+0x30] == NULL` As you control the values inside the **RSP** you just have to send some more NULL values so the constrain is avoided.

![](<../../.gitbook/assets/image (615).png>)

```python
ONE_GADGET = libc.address + 0x4526a
rop2 = base + p64(ONE_GADGET) + "\x00"*100
```

To the address indicated by One Gadget you need to **add the base address where `libc`** is loaded.

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One Gadget is a **great help for Arbitrary Write 2 Exec techniques** and might **simplify ROP chains** as you only need to call one address (and fulfill the requirements).
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
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