This custom script can be used to compromise a remote host and get a foothold on the host machine where docker daemon is running with root privilege. If the user using docker is in the group docker he can run container with host mounted volumes. If an attacker has gained access to the host machine during the exploitation phase, he/she can look for dangling volumes on the docker host as part of post-exploitation phase and examine for sensitive information in the volume, which can further be used to attack the infrastructure or the application in the environment. We can run the lightweight Docker container alpine and use a volume with the -v flag to mount the host file-system within the Docker container. Jai donc volontairement pull limage alpine et rpter la mme mthode que le premier cas. Developers use environment variables as a storage place to hardcode all the sensitive information like username, passwords, API keys, etc in the docker container. An attacker having access to a docker host can access this sensitive data. It is a tool which helps to create, deploy, and run applications by using containers. This scenario assumes you have shell access to the Linux machine as a low privilege user in the docker group. The following example show how to read /etc/shadow from host with the help of a docker container and a user in group docker. No votes so far! Check out the GTFOBins project for more Docker and Linux privilege escalation techniques. By passing the -it flag we can also spawn an interactive terminal within the Docker container. It is recommended to run the docker daemon in rootless mode. Start by performing basic enumeration to gather information about the system. Containers make it easy for the developers to build the application with all its dependencies and libraries and ship it out as one package. This is achieved by injecting a reverse shell payload to the root process of the host machine. This information can then be used by their application running in the container to retrieve the sensitive information from the environment variables to make database queries or API calls. Finally, we login using the credentials we have just discovered, and obtain root access through the debruyne user. To mitigate this technique we can run the Docker daemon as a none root user (rootless mode), rootless mode executes the Docker daemon and containers inside a user namespace, which separates the User IDs (uid) and Group IDs (gid) between the host Operating System and containers. The first line creates a container based on the ubuntu image, -v /etc/:/mnt option tells Docker to mount the /etc directory on the host machine to the /mnt directory in the container, and -it specifies an interactive session with a tty attached. The retrieved information can be used for a further attack in the network or application. Implement Authentication based mechanism to access the private registry (Token-based, bearer, OAuth, etc.). This can also be achieved using any of the following features: Containers help developers to create more secure environments because it isolates software. But with new technologies come new vulnerabilities. Be the first to rate this post. This poses challenges for both attackers and defenders of docker systems. Using this we can create a mount inside the Docker container mapping to the host file-system and read any files as if we were the root user on the host machine. For example, the ability to download third party files using wget must be disabled. This gives us access to the file-system on the host machine as the root user. Docker is a popular platform for developers to build, ship, and run distributed applications as containers. It doesnt matter which one. This can impose a great impact on the docker container security. More information can be found on the official Docker website. Identical to the commands we ran earlier, but this time we are only viewing the file's contents. An attacker can perform both enumeration and exploitation techniques using a python custom script. This is one of the ways to implement docker container security. A feature of Linux that can be used to separate the user IDs and group IDs between the host and containers is called User Namespaces. Dans cet article Docker Group LPE, nous allons passer dun utilisateur lambda sans droits mais dans le groupe docker lutilisateur root laide dune mauvaise configuration et utilisation de docker. A preferred alternative to the previous scenario would be to avoid modifying any file; instead, we will copy the contents of the shadow and passwd files and attempt to crack the passwords. Since docker is running as root with SGID, an unauthorized person who has access to the host user (with user privileges) can easily escalate privileges by mounting the host volume to one of the containers; granting the attacker full access to the filesystem. It is recommended to implement an authentication mechanism to the Docker daemon API and also implement TLS to the API call. Nous utilisons des cookies pour vous garantir la meilleure exprience sur notre site web. First, we will generate a password hash for a new user using OpenSSL. A docker example for privilege escalation. We will use John the Ripper to crack the passwords back on our machine, where we've created two files with contents from the passwd and shadow files of the victim's machine. It is recommended to secure the web application and perform proper input validation to stop an attacker from executing system commands. Si vous continuez utiliser ce site, nous supposerons que vous en tes satisfait. You now have full access to the host volume, and from here its just a matter of grabbing keys, hashes, and whatnot to get a shell. The volume created is then shared with a container. As there is no authentication implemented by default on Docker daemon API, an attacker can invoke the API remotely and perform an administrative task. Using the information we've gathered so far, we will attempt to write to the passwd file and elevate our privilege. Dans notre second cas, nous partons du principe que nous sommes dans un CTF et connect via VPN et donc nous ne pouvons pas sortir sur internet, en gnral une image est prsente volontairement pour nous permettre dexploiter cette technique. For example, consider a scenario where a developer has mounted a volume on the host and has written a sensitive file which contains database password/username. The use of API also helps in building automation scripts for the remote docker deployment without having to log in to the host system where the docker is installed to run the docker tasks. This method of privilege escalation abuses user namespaces in Linux, where the User ID (uid) of a user inside a container is mapped to the User ID (uid) of a user on the host. Dans ce premier cas, nous partons du principe que nous avons un accs sur la machine direct et quelle a bien accs internet sans rgles spcifiques au niveau du firewall. The problem arises when the docker group is assigned to the host user. This can be tackled in the right way by adding an additional level of docker container security like AppArmor, SECcomp and other suitable hardening techniques. I dont think Docker needs an introduction at this point, but in case you are unfamiliar with it; it is a way of isolating software packages by virtualizing them on an OS-level which runs in containers. It works in a similar way to traditional virtual machines, but with much less overhead as the kernel is shared between multiple containers. It is always advised to remove the container with -v flag. If a user belongs to the docker group, this effectively means that you can create a Docker container with a root user. See also: Running a Docker container as a non-root user, Running a Docker container as a non-root user. An attacker having the ability to run operating system commands via web application execution vulnerability can easily view the sensitive information set in the environment variable. A low privilege user (non-root user) in a Linux machine with Docker group assigned, can escalate the privilege to a root user and perform an administrative task in the host machine. However, using containers also increases the attack surface and risks because containerization of software also adds extra layers of abstraction and complexity which can increase docker vulnerabilities in the container environment. Zero-Day Vulnerabilities in Web Applications, How DevSecOps is a Key Enabler for Digital Transformation, Beagle Security named a Leader in G2 Summer 2022 Reports, Spring4Shell Vulnerability: Analysis and Mitigation. If the -v flag is not being used when removing the container, the volume will always end up dangling and remain in the local disk. This is a short guide on how to read the host file-system with root privileges as an unprivileged user, abusing the Docker group for privilege escalation. Implement Content Trust to impose client-side signing and validation of image tags. Keep in mind that this is not an exclusive list of privilege escalation techniques via Docker. We append a line to the passwd file that includes the username, followed by the hash we generated, user id zero, and group id zero specifying that the user is a superuser. Rootless mode executes the Docker daemon and containers inside a user namespace. User Namespaces can provide better isolation and security: the privileged user root in the container can be mapped to a non-privileged user on the host. We can shorten this whole process into a one-liner to read the /etc/passwd file of the host file-system. Next lets see if we can read the /etc/passwd file, this will be located at /root/passwd as thats where we mounted the volume in the first step. As the privileged flag is used to access the PID of the host from the container, an attacker having an initial foothold on the container can escape from the container environment and access the host machine with root privilege. Well be looking into a few attacks that can be performed to exploit docker vulnerabilities. Another method to go about this is to use a command docker image prune. This allows us to clean up all unused images. Nous allons tout simplement pull une image comme par exemple celle dubuntu qui nest pas prsente sur la machine cest donc pour cette raison que nous avons besoin dun accs rseau vers le docker hub. Docker daemon API is set up and configured to allow users to remotely access and administrate the docker related tasks via API. Due to its widespread adoption, you will likely come across it during a penetration testing engagement. An attacker can access insecure private registry remotely using the docker registry HTTP API to enumerate the list of repositories in the private registry. Hardening techniques can be implemented to increase the docker container security. It is recommended to implement container hardening techniques in order to limit the activity of the attacker after getting an initial foothold on to the system. A rootless mode is a mode where both the daemon and the container are running without root privileges. You signed in with another tab or window. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. In the docker setup, a user with low privilege (non-root user) is added to the docker group to perform docker related tasks without giving the user root or sudo privileges. If a user belongs to the Docker group, this effectively means that you can create a Docker container with a root user on the host machine. In an organization, when the development team will need to access the host resources from the container environment, it can be achieved using the privileged flag while running the container. Using this we can create a mount inside the Docker container mapping to the host file-system and read any files as if we were the root user. This can be combined with running the container without root privileges using userns-remap which isolates containers with a user namespace, further reading on this can be found on the official Docker website. Ce qui nous permet dutiliser docker compltement avec cet utilisateur et donc de monter le volume hte sur lun de nos conteneurs. First, make sure the host user is part of the docker group: Run docker container ps to get a quick list of the containers: From here you can spawn a tty for each container: Even better, you can specify -v to mount the entire filesystem of the host to one of the containers before accessing it. Victim machine with a local (none root) user in the. Next, we interact with the ubuntu container and write to the host's passwd file. It is recommended not to store sensitive information like passwords, keys, auth-tokens in the environment variables. An attacker can also use this attack vector to download the images in the private registry to localhost via remote API using the blobSum information to check the underlying code for any sensitive information. Et cest parti pour la mme opration mais avec limage alpine locale dj prsente sur la machine cible. We can check that these prerequisites are met with a few simple commands, Check local user is part of the docker group with id. Creating Private Registry is useful in a scenario where an organization needs to organize all the custom images privately and does not want to publish it to the public docker registry. Then we login as the newly created superuser. But as explained in the Docker security documentation: only trusted users should be allowed to control your Docker daemon. We can check the permissions on a file that is only usually readable/modifiable by the root user. My first CVE (2021-24856) WordPress Plugin, Sorare sous l'oeil scrutateur de lAutorit nationale des jeux, Cyberattaques: 15minutes pour exploiter une faille de scurit publique, Chinese Hackers Using New Manjusaka Hacking Framework Similar to Cobalt Strike, New 'ParseThru' Parameter Smuggling Vulnerability Affects Golang-based Applications, Comment fonctionne la compilation de programme. In this case, the user can run a light container with /etc mounted in and then get root access in the container. When the images are deleted from the host machine, this action will not lead to the deletion of the mounted volume automatically. Salut, bon article jai juste dtect dans Second cas, ceci; en gnral une image est prsente volontairement pour nous permettre dexploitation cette technique. Afin de raliser cette attaque, jai install une machine Linux ayant dj docker de prinstall laide de ce tutoriel suivant et en mettant lutilisateur ubuntu18 dans le groupe docker ce moment de linstallation : Comme prvu notre utilisateur fait bien parti du groupe docker ! Now when the developer tries to stop and remove the container, although the container is deleted, the volume is still dangling around and we can access the data in it. Docker is one of the most widely used container-based technologies. Grce ceci nous pouvons lire le fichier prsent dans /root et prouvant la russite de cette technique : Il est possible aprs a de changer/supprimer le hash de lutilisateur root dans le fichier /etc/shadow et galement de crer une cl ssh pour ce mme utilisateur. Le volume hte sur lun de nos conteneurs credentials we have just discovered and... 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