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58 lines
4 KiB
Markdown
58 lines
4 KiB
Markdown
# Common Exploiting Problems
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<details>
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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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* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
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* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
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* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** 🐦[**@carlospolopm**](https://twitter.com/hacktricks\_live)**.**
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* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
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</details>
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## FDs in Remote Exploitation
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When sending an exploit to a remote server that calls **`system('/bin/sh')`** for example, this will be executed in the server process ofc, and `/bin/sh` will expect input from stdin (FD: `0`) and will print the output in stdout and stderr (FDs `1` and `2`). So the attacker won't be able to interact with the shell.
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A way to fix this is to suppose that when the server started it created the **FD number `3`** (for listening) and that then, your connection is going to be in the **FD number `4`**. Therefore, it's possible to use the syscall **`dup2`** to duplicate the stdin (FD 0) and the stdout (FD 1) in the FD 4 (the one of the connection of the attacker) so it'll make feasible to contact the shell once it's executed.
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[**Exploit example from here**](https://ir0nstone.gitbook.io/notes/types/stack/exploiting-over-sockets/exploit):
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```python
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from pwn import *
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elf = context.binary = ELF('./vuln')
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p = remote('localhost', 9001)
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rop = ROP(elf)
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rop.raw('A' * 40)
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rop.dup2(4, 0)
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rop.dup2(4, 1)
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rop.win()
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p.sendline(rop.chain())
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p.recvuntil('Thanks!\x00')
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p.interactive()
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```
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## Socat & pty
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Note that socat already transfers **`stdin`** and **`stdout`** to the socket. However, the `pty` mode **include DELETE characters**. So, if you send a `\x7f` ( `DELETE` -)it will **delete the previous character** of your exploit.
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In order to bypass this the **escape character `\x16` must be prepended to any `\x7f` sent.**
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**Here you can** [**find an example of this behaviour**](https://ir0nstone.gitbook.io/hackthebox/challenges/pwn/dream-diary-chapter-1/unlink-exploit)**.**
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<details>
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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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|
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* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
|
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
|
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
|
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** 🐦[**@carlospolopm**](https://twitter.com/hacktricks\_live)**.**
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* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
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</details>
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