hacktricks/reversing-and-exploiting/linux-exploiting-basic-esp/stack-overflow/ret2ret.md

# Ret2ret

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## Basic Information

The main goal of this technique is to try to **bypass ASLR by abusing an existing pointer in the stack**.

Basically, stack overflows are usually caused by strings, and **strings end with a null byte at the end** in memory. This allows to try to reduce the place pointed by na existing pointer already existing n the stack. So if the stack contained `0xbfffffdd`, this overflow could transform it into `0xbfffff00` (note the last zeroed byte).

If that address points to our shellcode in the stack, it's possible to make the flow reach that address by **adding addresses to the `ret` instruction** util this one is reached.

Therefore the attack would be like this:

* NOP sled
* Shellcode
* Overwrite the stack from the EIP with **addresses to `ret`**
* 0x00 added by the string modifying an address from the stack making it point to the NOP sled

## References

* [https://github.com/florianhofhammer/stack-buffer-overflow-internship/blob/master/NOTES.md](https://github.com/florianhofhammer/stack-buffer-overflow-internship/blob/master/NOTES.md)

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<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>

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