If we wanted to see the kernel addresses exposed via /proc, this kind of operation isnt allowed if the container is run without excess capabilities, and if we execute, here is what happens if we run the command. Cgroup mounts are mounted read-only inside containers, so the release_agent file they host cannot be written to. Container technologies rely on various features such as namespaces, cgroups, SecComp filters, and capabilities to isolate services running on the same host and apply the least privileges principle. So the fc->user_ns is the Each child group can be configured to either trigger or not trigger the release agent (upon the termination of one of its processes) by writing to the notify_on_release file. The setcap command calls on libcap to do this. Your use of Play With Docker is subject to the Docker Terms of Service which can be accessed. If we look at the main() function, we can see how the exploit takes advantage of the fact that the root inode (e.g. If the super_block data doesnt set it, it just bypassed this reveal check. In this lab youll learn the basics of capabilities in the Linux kernel. If the commandline doesn't appear in the terminal, make sure popups are enabled or try resizing the browser window. Multiple capabilities within the same set are separated by commas ,. As part of the same command try and change the ownership of a file or folder. Figure 7 shows the container setting the release agent, while Figure 8 shows a non-root container failing to do so. CVE-2022-0492 shows us that we can mount cgroupfs in new userns and then write to the release_agent file. In that case, even if a privileged program is compromised, the possible damages are limited by the set of capabilities that are available to the process. Docker capability constants are not prefixed with CAP_ but otherwise match the kernels constants. As I was just discussing the relative merits of using Docker, and how security is often quoted as one of them, I thought it would be interesting to dissect exactly how this exploit works by looking at a bit of the code. if ((fd = open_by_handle_at(bfd, (struct file_handle *)ih, O_RDONLY)) < 0) die("[-] open_by_handle_at"); fprintf(stderr, "[!] CVE-2022-0492 marks a logical bug in control groups (cgroups), a Linux feature that is a fundamental building block of containers. Notice the user ns passed to ns_capable is fs_contexts user ns. This system call takes a file descriptor for any open file system descriptor within the mount point of the file in question (mount_fd), a file handle that describes the file we wish to open, and additional flags we want to pass to the process that opens the file. It allows administrators to configure a "release agent" program that would run upon the termination of a process in the cgroup. In this step youll learn the basics of capabilities. 2022 Palo Alto Networks, Inc. All rights reserved. Even for this capability, the potential damage might be huge if the permissions are misused. Recently it has a CVE and become popular. CVE-2022-0492 is fixed on the latest Linux release; all users are encouraged to upgrade to the latest kernel version of their respective distribution. in sysfs and procfs. CVE-2022-0492 marks another Linux vulnerability that can be exploited for container escape. The mount_too_revealing is used only in new user namespace as we can see it return false if it is called in the init_user_ns. That's because the container may not have the utilities the script relies on, or their correct version, which may lead to inaccurate results. This function is interesting. The cgroup release_agent escape is a classical user mode helper escape issue several years ago. Linux simply didn't check that the process setting the release_agent file has administrative privileges (i.e. However, those files are also used in other exploitation to reach the same goal to escalate privileges and break the isolation. On one hand, the goal of capabilities is to limit the power of privileged programs to be less than root. As you can see in the last example, it was possible to create the new namespace thanks to the extra privileges. Using the command cat /proc/self/status, you can find the cap values applied. Linux supports two cgroup architectures called v1 and v2. reveals too much data the kernel should deny it. The procfs and sysfs will go to mnt_already_visible which we cant pass the permission check. The correct way of doing this requires ambient capabilities which was added to the Linux kernel in version 4.3. For example the runcs default The Linux kernel is able to break down the privileges of the root user into distinct units referred to as capabilities. If we tie this information to what we know about CAP_DAC_READ_SEARCH back above, we know that CAP_DAC_READ_SEARCH applied to our container not only allows us to traverse the file system without permission checks, but also explicitly removes any checks to open_by_handle_at(2) and could allow our process to sensitive files opened by other processes. On the other hand, if we have a program CAP_SYS_ADMIN, the game is more or less over. This reason is as following. The CAP_DAC_OVERRIDE capability allows the root user to bypass kernel permission checks on file read, write and execute operations. The capsh command can be useful for experimenting with capabilities. Thiss why it is a recurring topic in infosec and why it is so important to have tools like Falco to detect it. In docker and runc environment, it has maskedPaths which means the path should be masked in container. So it will pass the mount_capable check. But Jen, you may be asking, why is this system call even necessary? You can probably already imagine why this is a security nightmare in the making, lets say if one process has a handle open to something like, /etc/shadow and another process ISNT supposed to have access to it, but can somehow call open_by_handle_at(2) on the handle opened by the other process. The maskedPaths is implemented by mounting these file to /dev/null so the procfs has child mountpoint. Add privileges to non-root users at a very granular level. Any subsequent directories under the root cgroup denote a new child cgroup. After that, if you would like to find out more about Falco: An ad blocking extension or strict tracking protection is preventing this form from loading. Here is what happens if we run the container with CAP_SYS_ADMIN capability instead. Note: Another option may be added in future versions of Docker that will allow you to run containers as a non-root user with added capabilities. In the past, this wouldn't be considered a security issue. We still cant mount procfs in the new usernamespace and pid namespace. You can still see how a full exploit looks in the screenshot below. This confusion brings a lot of doubts and misunderstandings to developers hoping to understand how to proceed. By default, Docker drops all capabilities except those needed, using a whitelist approach. This is similar to the way the setuid bit works. As seen in the screenshots above, not all hosts are configured to support the same subsystems. Three new fields have been added into Falco to accomplish this task: In this case, we are in a container run as privileged and we can easily see the list of capabilities applied. Figure 1 shows the cgroup membership of a Docker container, and Figure 2 shows the cgroup membership of a Kubernetes pod. If you scroll back up to Figure 1, you'll see that the container doesn't run in the root memory cgroup but in a child cgroup: /docker/. the hard drive, or the mouse) can be accessed by processes in the cgroup. (Japanese). The "Am I Affected?" Run containers as root with limited capabilities and never change them within a container. Following is the reproducer. For example, the CAP_CHOWN capability is what allows the root user to make arbitrary changes to file UIDs and GIDs. First, lets look at the data structure thats defined at the top of the file, my_file_handle: This is simply an analog to the file_handle stat structure in the Linux kernel, defined here: Presumably the actual file handle value (f_handle) has no size since it depends on the architecture of your system. The following command enables the notify_on_release functionality for the a_child_cgroup cgroup: $ echo 1 > /sys/fs/cgroup/memory/a_child_cgroup/notify_on_release. The release_agent file is only visible in the root cgroup directory and affects all its child cgroups. Current is multiple sets separated by spaces. Updated March 7, 2022: Removed mentions of exploitation by (1) containers running with CAP_SYS_ADMIN and not protected by AppArmor or SELinux, and (2) semi-privileged host processes. With the advent of the 2.2 kernel, we are allowed more fine-grained access control over exactly what a privileged process can do. To read more about the various container-level privileges that are configurable in the kernel, you can man 7 capabilities (http://man7.org/linux/man-pages/man7/capabilities.7.html)). The command gives no return code indicating that the operation succeeded. You also learned that Docker does not currently support adding capabilities to non-root users. Tags: containers, CVE-2022-0492, Linux, vulnerabilities, This post is also available in: Well test these out in the next section. FIND, FOCUS, and FIX the Cloud Threats that Matter with Accenture, AWS, Expel, Snyk, Sysdig and SANS. If you are unable to complete this form, please email us at [emailprotected] and a sales rep will contact you. The issue stands out as one of the simplest Linux privilege escalations discovered in recent times: The Linux kernel mistakenly exposed a privileged operation to unprivileged users. Linux documentation clearly defines capabilities as: Starting with kernel 2.2, Linux divides the privileges traditionally associated with superuser into distinct units, known as capabilities, which can be independently enabled and disabled. Background on Cgroups http://jenpire.com. The memory cgroup for example, can limit the memory consumption of a collection of processes. The chown capability is all that is needed to change the ownership of a file. Well, you can see where this is going, and its not going to be pretty. Shortcuts like ./ are not permitted. The command below shows how to set the CAP_NET_RAW capability as effective and permitted on the file represented by $file. By submitting this form, you agree to our Terms of Use and acknowledge our Privacy Statement. The procfs and sysfs contains some global data, so the container should not touch. The first is that why core_pattern and uevent_helper cant work. Docker imposes certain limitations that make working with capabilities much simpler. Remember that Docker does not use the CAP_ prefix when addressing capability constants. In this example, we use the command unshare which to create a new namespace; in this case, inside a container. Prisma Cloud users can refer to the "Prisma Cloud Protections" section for the mitigations provided by Prisma Cloud. Well, lets just head to the helpful ol man-page (`man 7 capabilities`) to find out. Unit 42 recommends users upgrade to a fixed kernel version. Digital Forensics Basics: A Practical Guide for DFIR Kubernetes, CVE-2022-0492: Privilege escalation vulnerability causing container escape, Security and visibility for cloud applications. In Docker Engine 0.12 (and continuing in Docker Engine 1.0) we drop all kernel capabilities by default. Cgroups are managed via cgroupfs, a management API exposed as a filesystem and normally mounted under /sys/fs/cgroup. One caveat of mounting a cgroupfs in a cgroup namespace is that you mount the cgroup you belong to, not the root cgroup. Thankfully for us, in the new Falco version 0.32 its possible to monitor the thread capabilities and be sure that just the allowed capabilities are available. Got a final handle!\n"); http://stealth.openwall.net/xSports/shocker.c, https://gist.github.com/jandre/4a8bed58dcb3455cfa85. Then we can mount the cgroupfs and write our data to release_agent. Learn on the go with our new app. The core problem is misconfigured permissions (CAP_DAC_READ_SEARCH) that are granted to the container process, and illustrates how container-level virtualization can be tricky to configure. For example, the proc_fill_super set it in proc_fill_super. Prisma Cloud Protections Now we can see we mount sysfs successfully. In an environment without file based capabilities, its not possible for applications to escalate their privileges beyond the bounding set (a set beyond which capabilities cannot grow). Docker and Kubernetes also have a variety of cgroup configurations, so containers on your hosts or clusters may not have the same memberships as in the examples above. Containers running with AppArmor, SELinux or Seccomp are protected. Using extended attributes (attr package): Docker images cannot have files with capability bits set. Here, we indicate some container breakout vulnerabilities: In this article, we explain how you can detect and monitor capabilities using Falco, analyzing a well-known container escaping technique. A malicious container that wants to exploit CVE-2022-0492 must mount another, writable cgroupfs. We must be running as root inside the container. new user namespace and has the CAP_SYS_ADMIN. Start another new container and drop all capabilities for the containers root account other than the CAP_CHOWN capability. Having this information available in Falco allows us to create detection over those capabilities and raise alerts if misconfigured capabilities are applied in our environment. The remainder of this lab will show you additional tools for working with capabilities form the Linux shell. As the last example points out, there are some actions that require CAP_SYS_ADMIN by design. As reported in the command documentation, unshare requires the CAP_SYS_ADMIN capability to work and perform the actions. Other examples for subsystems include block IO, CPU and remote direct memory access (RDMA). While those can exploit CVE-2022-0492 to escalate privileges, they often have other avenues to escalate privileges that don't require a vulnerability. To add capabilities to the root account of a container. But through the unshare() syscall, containers can create new user and cgroup namespaces where they possess the CAP_SYS_ADMIN capability and can mount a cgroupfs. Exploitation Prerequisites The fc->user_ns is set in the init_fs_context callback of struct file_system_type. Users can also choose to block containers running without Seccomp, as shown in Figure 13. From the definition of find_handle(), you can see it takes a file descriptor for mount_fd, (hello, /.dockerinit! The first interesting part is SB_I_USERNS_VISIBLE. The Docker folks have released a helpful post-mortem: In earlier Docker Engine releases (pre-Docker Engine 0.12) we dropped a specific list of kernel capabilities, ( a list which did not include this capability), and all other kernel capabilities were available to Docker containers. ), a path to look for, an input file handle, and an output file handle which our results get copied to. As always, it's best to upgrade your hosts to a fixed kernel version. Each subsystem is typically mounted at /sys/fs/cgroup/, which is considered the root cgroup for the subsystem. The lesson to be learned is that sandboxing things, especially sandboxing apps that need some level of root privileges or access, is not easy. Also back in Figure 1, you'll see that Docker ran the container in the root RDMA cgroup. While possible, we don't advise running the script in an existing container. The core of the logic you can see is in find_handle(), so lets look there next. maskedPaths is as following: As we can see some of the proc and sys file is masked in container which means the container has no fully view of procfs and sysfs. We strongly recommend running containers with Seccomp and either AppArmor or SELinux enabled, to protect against this vulnerability and against future Linux zero-day vulnerabilities. come work @threatstack https://www.threatstack.com, Jen writes about security & software stuff. In all three vulnerabilities, securing containers with Seccomp and either AppArmor or SELinux was enough to prevent container escape. To exploit the issue, we need to write a malicious release agent to the release_agent file. So, lacking sufficient information for a decision, the developer chooses CAP_SYS_ADMIN or similar excessive capabilities for their new feature. As such, the vulnerability only allows root processes to escalate privileges. then we simply call open_by_handle_at(2) on the returned file descriptor, and call read() to read the data on the file descriptor returned: So how was this vulnerability introduced? At first glance, a privilege escalation vulnerability that can only be exploited by the root user may seem bizarre. CVE-2022-0492 stems from a missing verification. Just as Yuval Avrahami point out, CVE-2022-0492 is about creating new user & cgroup namespace and do the release_agent escape. In other words, capabilities divide the privileges of root user into small pieces to grant a thread just enough power to perform specific privileged tasks. Am I Affected? us-central1-docker.pkg.dev/twistlock-secresearch/public/can-ctr-escape-cve-2022-0492, Protect Against Russia-Ukraine Cyber Activity, A Win for Defense-in-Depth Container Escape Prerequisites, On a host that enables unprivileged user namespaces; and. In this scenario, we see a well-known container escaping technique which relies on cgroup v1 virtual filesystem and, big surprise, CAP_SYS_ADMIN. As you can see, with the right capabilities we can open the file without any warning message by using the right capability. As we dont create a new pid ns so the fc->user_ns is the init user ns. capsh --help shows how to use the command: Warning: The operation succeeds because although you dropped all capabilities for the containers root account, you added the chown capability back. If we `man 2 open_by_handle_at`, it all becomes clear. Splitting root privileges into small pieces is useful from a security perspective, although we dont want too many pieces. Option 1 should be avoided wherever possible. That being said, if you run containers without best practice hardenings, or with additional privileges, you may be at risk. Not every container can create a new user namespace the underlying host must have unprivileged user namespaces enabled. A Win for Defense-in-Depth Container Escape Prerequisites In the cgroupfs case, as we unshare user namespace and cgroup namespace together. As of Docker 1.12 you have 3 high level options for using capabilities: Option 2 as the most realistic as of Docker 1.12. Capabilities are a per-thread attribute.. Almost all of the special powers associated with the Linux root user are broken down into individual capabilities. Here we uses ro as the runc mount sysfs readonly in container. I do this test in 5.4.1 successfully but failed in 5.11 maybe there are more protections. For those running containers, enable Seccomp and ensure AppArmor or SELinux are enabled. However, it is possible to mount volumes that contain files with capability bits set into containers. Under Compute/Defend/Compliance, you can further harden your environments by blocking containers that don't follow certain compliance rules, for example, and as shown in Figure 13, those running without Seccomp. The exploit makes this claim quite cleanly at the top of its file: What does this mean? The first permission check is at mount_capable. The very short patch for CVE-2022-0492 (lines 2-8 below) best explains the vulnerability: As established, if you can write to the release_agent file, you can force the kernel into invoking a binary of your choosing with elevated privileges and take control of the entire machine. So I guess the revealing reveals the meaning, if the mount operation Without both, a container can mount cgroupfs by abusing user namespaces. New Linux Vulnerability CVE-2022-0492 Affecting Cgroups: Can Containers Escape? To drop all capabilities and then explicitly add individual capabilities to the root account of a container. Since this step is always doable, it has no implications on whether an environment is vulnerable to CVE-2022-0492, and so we decided to leave it out. Docker sets the bounding set before starting a container. The only two fs who set this Control groups (cgroups) are a Linux feature that allows administrators to limit, account for and isolate the resource usage of a collection of processes. To protect against malicious containers in scenarios where upgrading isn't possible, users can enable one of the following mitigations: Prisma Cloud detects and alerts on hosts running a vulnerable kernel version. As before, lets see what happens when running the command in a container without adding the capability. In this case, we check if the thread explicitly contains CAP_SYS_ADMIN in the set of effective capabilities. Libcap and libcap-ng can both be used to modify capabilities. At first glance I dont know why and has little time to dig into the issue why it has a CVE now. The final step of the escape is to invoke the configured release_agent, which doesn't require any privileges. CVEs published in recent years have shown that those features can be misconfigured and lead an attacker to escape and escalate the privilege inside the container and the host. Not every container can exploit CVE-2022-0492 to escape; only those with permissive security profiles can perform the necessary steps. Anyway, if we allow this, You may need to manually install the packages required for some of these commands. One of the features of cgroups v1 is the release_agent file. Step 2 - Working with Docker and capabilities. The command works because the default behavior is for new containers to be started with a root user. It will help you understand how capability sets interact with each other, and is very useful if you plan to run privileged docker containers and manage capabilities manually inside of them. Run containers as an unprivileged user with no capabilities. Start a new container and prove that the containers root account can change the ownership of files. In this step you have added and removed capabilities to a range of new containers. The above command fails because Docker does not yet support adding capabilities to non-root users. To test your environment, you can simply deploy a new container running our us-central1-docker.pkg.dev/twistlock-secresearch/public/can-ctr-escape-cve-2022-0492 image, which is configured to run the script, print its output and exit. If you go over the bolded lines in this section, you'll find the requirements for exploiting CVE-2022-0492 for container escape via user namespaces. In a 64-bit system, as described in the exploit, it will be 8 bytes, where the first 4 bytes represent the inode of the path in question. The docker doesnt give CAP_SYS_ADMIN to container. After read Yuval Avrahamis post New Linux Vulnerability CVE-2022-0492 Affecting Cgroups: Can Containers Escape and discussed with him I found there are a lot of things after CVE-2022-0492 so I decide make a post. You will complete the following steps as part of this lab. Mitigations There are multiple ways to read out the capabilities from a file. Run containers as root with a large set of capabilities and try to manage capabilities within your container manually. Please temporarily disable ad blocking or whitelist this site, use less restrictive tracking protection, or enable JavaScript to load this form. mnt_already_visible will iterate the new mount namespace and check whether it has child mountpoint. This reduces the risk of Docker containers using capabilities to escalate privileges. Also we will use sysfs as we just need to delete one line. Youll also learn the Docker commands used to manage capabilities for a containers root account. In the following commands, $CAP will be used to indicate one or more individual capabilities. Copyright 2022 Sysdig, Inc. All Rights Reserved. Next we delete the /sys/firmware in maskedPaths in config.json. And that brings us to where we are today: CAP_SYS_ADMIN is the new root. The container shown in the attached screenshot runs without Seccomp, AppArmor or SELinux. However we will go to the second permission check of mount. The sysfs user the netnss user namespace so we need use unshare -Urmn sh. Lets see whether we can mount sysfs or procfs in new user namespace. + * Release agent gets called with all capabilities. New Linux Vulnerability CVE-2022-0492 Affecting Cgroups: Can Containers Escape? This is done by writing the desired release agent path to the release_agent file, as demonstrated below: $ echo /bin/my-release-agent > /sys/fs/cgroup/memory/release_agent. By default, containers run without CAP_SYS_ADMIM, and thus cannot mount cgroupfs in the initial user namespace. Many privilege escalation vulnerabilities in the Linux kernel can only be exploited for container escape when the container is allowed to create a new user namespace, or in other words, when the container runs without Seccomp. Decoding the result 00000000a82425fb value using capsh, you can see the list of capabilities. CAP_NET_ADMIN is required to perform all the network-related operations from changing interface configurations, administrating the host firewall and setting promiscuous mode. It is of course possible to get file capabilities into containers at runtime, however this is not recommended. Environments with lax security controls hosting untrusted or publicly exposed containers are, unsurprisingly, at high risk. This article explains capabilities in a lot of detail. Recently, an interesting Docker exploit was posted (http://stealth.openwall.net/xSports/shocker.c) that demonstrates an information leak where a Docker container can access some privileged filesystem data where it shouldnt. Use libcap-ng to set the capabilities of a file. You have seen that capabilities can be added and removed from the root user of a container at a very granular level. The release agent runs with the highest possible permissions: a root process with all capabilities in the initial namespaces. This is the default on recent Ubuntu releases, for example. /sys/fs/cgroup//docker/. On a high level, this function does this: a) If have not reached the leaf (the file itself, which is tested by looking for a / in the path), we test to see if we are a directory, and if so, list the contents of the directory. we can mount the whole procfs data in new user namespace. Each time you will use the commands learned in the previous step to tweak the capabilities associated with the account used to run the container. As pointed out in the warning message, we should use the specific capability CAP_SYSLOG to perform this action since it has been created to segregate the permissions from CAP_SYS_ADMIN. Cgroups are divided into subsystems, each configuring access to a different resource. That means if you run a Docker container without specifying additional settings, Docker will use the limited set of capabilities. So in the mount_too_revealing permission check, the cgroupfs passed it. Thanks to this rule, we can create a strong and noiseless detection on all the techniques that use release_agent and excessive capabilities to break container isolation and comprise the entire node. There are two main sets of tools for managing capabilities: Below are some useful commands from both. So, without further ado, how does our friend shocker.c accomplish this? In the screenshot above, the container successfully mounted a memory cgroup, but you may notice that the release_agent file isn't included in the mounted directory! This time we will pass the mount_capable check. This command also gives no return code, indicating a successful run. The cgroup v1 virtual filesystem must be mounted read-write inside the container. Start another new container and drop only the CHOWN capability form its root account. A well-known container escaping technique which relies on cgroup v1 virtual filesystem and, big surprise,.! Indicate one or more individual capabilities perspective, although we dont create a new ns. The hard drive, or enable JavaScript to load this form, can. From a security perspective, although we dont want too many pieces the first that! Just bypassed this reveal check we need to delete one line add privileges non-root. Seccomp, as demonstrated below: $ echo /bin/my-release-agent > /sys/fs/cgroup/memory/release_agent which on. Mitigations provided by prisma Cloud users can also choose to block containers running without Seccomp, AppArmor or.... Command enables the notify_on_release functionality for the subsystem and write our data to release_agent CVE-2022-0492 must mount another writable. Those files are also used in other exploitation to reach the same goal escalate. User namespaces enabled maybe there are multiple ways to read out the capabilities of a.. Threatstack https: //www.threatstack.com, Jen writes about security & software stuff ): Docker images can not written... As always, it 's best to upgrade your hosts to a fixed kernel version topic! Than root promiscuous mode we do n't require any privileges mounting these to! Latest Linux release ; all users are encouraged to upgrade your hosts to a different resource does mean... Many pieces if the commandline does n't require a vulnerability are, unsurprisingly, at high risk FIX Cloud! Write and execute operations 8 shows a non-root container failing to do this test in 5.4.1 successfully but failed 5.11! Becomes clear root with limited capabilities and try to manage capabilities within same... Container that wants to exploit CVE-2022-0492 must mount another, writable cgroupfs implemented by mounting these to! If it is called in the last example, the potential damage might be if... The mount_too_revealing permission check of mount process in the cgroup membership cap_dac_override docker escape a file marks a bug! All of the special powers associated with the right capability only those with permissive security profiles perform!, while Figure 8 shows a non-root container failing to do this test in 5.4.1 successfully failed. Find out step youll learn the basics of capabilities exploit makes this quite... Choose to block containers running with AppArmor, SELinux or Seccomp are protected granular.... We uses ro as the most realistic as of Docker containers using capabilities escalate. Cgroupfs and write our data to release_agent architectures called v1 and v2 settings. Going to be started with a root process with all capabilities in the initial namespaces libcap to do.... Example, the cgroupfs case, inside a container your hosts to a kernel! Pid namespace delete the /sys/firmware in maskedPaths in config.json highest possible permissions cap_dac_override docker escape a root with!: CAP_SYS_ADMIN is the default behavior is for new containers to be started with a root user are broken into! The setuid bit works however we will use sysfs as we dont want too many pieces and permitted on other! Less over configured release_agent, which does n't appear in the cgroup membership of container! Which was added to the latest kernel version relies on cgroup v1 virtual must! Perform all the network-related operations from changing interface configurations, administrating the host firewall and promiscuous! Cgroup directory and affects all its child cgroups hosts are configured to support same! Out the capabilities of a Kubernetes pod the super_block data doesnt set in... All rights reserved which can be exploited by the root cgroup directory and affects its... Are also used in other exploitation to reach the same command try and change the of! Look for, an input file handle, and an output file,! Understand how to proceed mount sysfs successfully release ; all users are encouraged to to... Only those with permissive security profiles can perform the necessary steps years ago runc mount or! Privileges ( i.e libcap to do this test in 5.4.1 successfully but failed in 5.11 maybe there are actions! Brings a lot of doubts and misunderstandings to developers hoping to understand how to proceed the highest possible permissions a... You also learned that Docker does not use the command in a cgroup is. Are also used in other exploitation to reach the same goal to escalate privileges of.... Have other avenues to escalate privileges happens when running the script in an container. Exploitation Prerequisites the fc- > user_ns is the init user ns passed to is... Accessed by processes in the initial user namespace only the chown capability form its root.... Youll also learn the Docker commands used to modify capabilities in proc_fill_super detect it all that is to!, enable Seccomp and ensure AppArmor or SELinux was enough to prevent escape. Of files just bypassed this reveal check also we will use the command cat /proc/self/status, you see. With CAP_ but otherwise match the kernels constants range of new containers might huge! Users are encouraged to upgrade your hosts to a fixed kernel version of their respective distribution the notify_on_release for! Agree to our Terms of use and acknowledge our Privacy Statement 1 shows the container a CVE Now are actions... The cap values applied cgroups ), a Linux feature that is needed to cap_dac_override docker escape the of. For this capability, the goal of capabilities can exploit CVE-2022-0492 to escape ; only those permissive. The command unshare which to create a new user & cgroup namespace and check whether has... Account of a Kubernetes pod architectures called v1 and v2 contains some global data, so the >., AppArmor or SELinux settings, Docker will use the limited set capabilities. This reduces the risk of Docker 1.12 normally mounted under /sys/fs/cgroup almost all of the 2.2,! Will iterate the new mount namespace and check whether it has a CVE Now you a! Option 2 as the runc mount sysfs or procfs in new user & cgroup namespace and check whether it maskedPaths. Writable cgroupfs to escalate privileges capabilities in a container maskedPaths in config.json libcap-ng to set the capability. Container at a very granular level command works because the default behavior is for new containers to less... Broken down into individual capabilities ran the container with CAP_SYS_ADMIN capability instead at first glance i know! Kernel capabilities by default, containers run without CAP_SYS_ADMIM, and Figure 2 shows the release_agent! Rdma cgroup the procfs and sysfs contains some global data, so the container with CAP_SYS_ADMIN to... This requires ambient capabilities which was added to the root user of a collection processes! ; in this case, as we can see it return false if is. The memory cgroup for the subsystem running with AppArmor, SELinux or Seccomp are protected that process! Complete this form, please email us at [ emailprotected ] and a sales rep will you! Behavior is for new containers other avenues to escalate privileges fs_contexts user ns on file read, write and operations! Passed to ns_capable is fs_contexts user ns your hosts to a fixed kernel version of their respective distribution read-only containers. Capabilities by default, containers run without CAP_SYS_ADMIM, and thus can mount... As we dont create a new pid ns so the container in the you... Containers run without CAP_SYS_ADMIM, and thus can not have files with capability bits set shows a non-root container to! Cgroups are divided into subsystems, each configuring access to a range of new containers be... But otherwise match the kernels constants as demonstrated below: $ echo /bin/my-release-agent >.. Access ( RDMA ) the most realistic as of Docker 1.12 filesystem and, big,... Appear in the command cat /proc/self/status, you can find the cap values applied attached runs... The capability fixed on the latest Linux release ; all users are encouraged to upgrade your hosts to a kernel. Does our friend shocker.c accomplish this most realistic as of Docker 1.12 restrictive tracking protection, or enable JavaScript load... Of find_handle ( ), a path to the Linux kernel in version 4.3 exploit to. Wants to exploit the issue, we see a well-known container escaping which. Classical user mode helper escape issue several years ago this requires ambient capabilities which was added to the cgroup... Individual capabilities handle! \n '' ) ; http: //stealth.openwall.net/xSports/shocker.c,:. To read out the capabilities of a Kubernetes pod can open the file represented $! Tools like Falco to detect it this lab blocking or whitelist this,. A range of new containers to be less than root avenues to escalate and! Exploit makes this claim quite cleanly at the top of its file: what does this mean cgroup release_agent.... Not touch the CAP_NET_RAW capability as effective and permitted on the file without any warning message by using the capability. A large set of capabilities to be less than root access to a range of new containers block containers. Container with CAP_SYS_ADMIN capability to work and perform the actions cap_dac_override docker escape Seccomp, AppArmor or SELinux most. But Jen, you can find the cap values applied a privileged process can.... Looks in the cgroup you belong to, not all hosts are configured to support cap_dac_override docker escape same command and... New container and drop only the chown capability is what allows the root account cgroupfs write! ( RDMA ) goal of capabilities is to limit the power of privileged programs to be with. Result 00000000a82425fb value using capsh, you may be at risk default containers. Topic in infosec and why it is called in the new root managed via cgroupfs, a management API as... User ns passed to ns_capable is fs_contexts user ns our Terms of use and acknowledge our Statement.