cap_dac_override docker escape

FIND, FOCUS, and FIX the Cloud Threats that Matter with Accenture, AWS, Expel, Snyk, Sysdig and SANS. So, without further ado, how does our friend shocker.c accomplish this? At first glance I dont know why and has little time to dig into the issue why it has a CVE now. This is similar to the way the setuid bit works. reveals too much data the kernel should deny it. This is the man page for capabilities. Its a great question, and one that can also be answered by the `open_by_handle_at` man page: So, where file descriptors are unique per process, which means you cant easily pass them around, the idea is you can pass around these file handles (which represents a structure that describes an open file system entry in the kernel) to other processes. A Docker container, for example, would normally be a part of the /docker/ cgroup, which could be found on the host at /sys/fs/cgroup//docker/. This confusion brings a lot of doubts and misunderstandings to developers hoping to understand how to proceed. The cgroup v1 virtual filesystem must be mounted read-write inside the container. The first is that why core_pattern and uevent_helper cant work. That means if you run a Docker container without specifying additional settings, Docker will use the limited set of capabilities. CVE-2022-0492 is now the third kernel vulnerability in recent months that allows malicious containers to escape. It allows administrators to configure a "release agent" program that would run upon the termination of a process in the cgroup. There are two main sets of tools for managing capabilities: Below are some useful commands from both. 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. However, it is possible to mount volumes that contain files with capability bits set into containers. For example, CAP_CHOWN, CAP_NET_ADMIN, CAP_SETUID, CAP_SYSADMIN etc. 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. To add capabilities to the root account of a container. 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. The device cgroup defines which devices (e.g. 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. You may need to manually install the packages required for some of these commands. If the super_block data doesnt set it, it just bypassed this reveal check. we can mount the whole procfs data in new user namespace. Multiple capabilities within the same set are separated by commas ,. By submitting this form, you agree to our Terms of Use and acknowledge our Privacy Statement. 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. By default, containers run without CAP_SYS_ADMIM, and thus cannot mount cgroupfs in the initial user namespace. Thus, the only way to see if there are misuses or malicious behaviors is monitoring the capabilities for threads and processes. Essentially, this changes our use of kernel capabilities from a blacklist to a whitelist. Using the new Falco fields in rules, its now possible to raise security alerts and get flagged when these malicious behaviors happen in your environment. Using extended attributes (attr package): Docker images cannot have files with capability bits set. In previous release_agent escape, we need to add CAP_SYS_ADMIN capability to the container. and Twitter Bootstrap, New Linux Vulnerability CVE-2022-0492 Affecting Cgroups: Can Containers Escape. In addition, the Linux development model doesnt have a central authority determining how capabilities should be assigned and split. With the advent of the 2.2 kernel, we are allowed more fine-grained access control over exactly what a privileged process can do. Sign up to receive the latest news, cyber threat intelligence and research from us. And in this user namespace the container has no CAP_SYS_ADMIN so it will not pass the mount_capable check. 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. Remember that Docker does not use the CAP_ prefix when addressing capability constants. Create another new container and try adding the CHOWN capability to the non-root user called nobody. Since Seccomp blocks the unshare() syscall, only containers running without Seccomp can create a new user namespace. Exploitation Prerequisites In containers which are isolated environments by definition, the most permissive capabilities are already removed by default. Cgroup mounts are mounted read-only inside containers, so the release_agent file they host cannot be written to. The platform also generates compliance alerts on containers that aren't protected by Seccomp, and on those running with neither AppArmor nor SELinux. Copyright 2022 Sysdig, Inc. All Rights Reserved. In this step you have added and removed capabilities to a range of new containers. 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. The final step of the escape is to invoke the configured release_agent, which doesn't require any privileges. You have seen that capabilities can be added and removed from the root user of a container at a very granular level. One very recent example is the CVE-2022-0492. http://jenpire.com. (Japanese). 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 lab youll learn the basics of capabilities in the Linux kernel. If you are unable to complete this form, please email us at [emailprotected] and a sales rep will contact you. And that brings us to where we are today: CAP_SYS_ADMIN is the new root. Due to the broad permissions, it can easily lead to additional capabilities or full root (typical access to all capabilities). Docker imposes certain limitations that make working with capabilities much simpler. Youll learn how they work with Docker, some basic commands to view and manage them, as well as how to add and remove capabilities in new containers. Watch On Demand! Twitter: @fun_cuddles. Prisma Cloud users are encouraged to review Compute/Monitor/Compliance and determine whether any of their containers run without Seccomp. Lets find out. Learn on the go with our new app. The release agent runs with the highest possible permissions: a root process with all capabilities in the initial namespaces. Whether it is possible for Docker to approximate this behavior in older kernels requires more research. Basically this means that CAP_DAC_READ_SEARCH was previously a capability they had forgotten to add to their blacklist by default, and no longer applies since now you have to explicitly define which permissions you want your containers to have since Docker 1.0.0. For example, the proc_fill_super set it in proc_fill_super. In containers, even though a set of capabilities are removed by default, its always possible to expand the set of capabilities by specifying the ones to add when running the container. Prisma Cloud Protections new user namespace and has the CAP_SYS_ADMIN. The Linux kernel is able to break down the privileges of the root user into distinct units referred to as capabilities. As such, the vulnerability only allows root processes to escalate privileges. In conclusion, a container can escape if it runs: Unit 42 researchers created a script that can test whether a container environment is vulnerable to CVE-2022-0492. Containers running with AppArmor, SELinux or Seccomp are protected. The first interesting part is SB_I_USERNS_VISIBLE. Decoding the result 00000000a82425fb value using capsh, you can see the list of capabilities. This can be very confusing because it doesnt actually take away the capability from the effective or inheritable set. Add privileges to non-root users at a very granular level. The capsh command can be useful for experimenting with capabilities. One caveat of mounting a cgroupfs in a cgroup namespace is that you mount the cgroup you belong to, not the root cgroup. Conclusion. Not every container can exploit CVE-2022-0492 to escape; only those with permissive security profiles can perform the necessary steps. the CAP_SYS_ADMIN capability). Using the command cat /proc/self/status, you can find the cap values applied. In this step youll learn the basic approach to managing capabilities with Docker. Then we can mount the cgroupfs and write our data to release_agent. 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. 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. Postmortem from the docker folks: http://blog.docker.com/2014/06/docker-container-breakout-proof-of-concept-exploit/, like this kind of stuff? Got a final handle!\n"); http://stealth.openwall.net/xSports/shocker.c, https://gist.github.com/jandre/4a8bed58dcb3455cfa85. Fortunately, environments that follow best practices are protected from this vulnerability. Yay! On Feb. 4, Linux announced CVE-2022-0492, a new privilege escalation vulnerability in the kernel. The core of the logic you can see is in find_handle(), so lets look there next. Even though the kernel won't explicitly check the writing processes' privileges, normal file ownership and permission semantics still apply. When a process dies, the kernel checks whether its cgroups had notify_on_release enabled, and if so, spawns the configured release_agent binary. in sysfs and procfs. Here we uses ro as the runc mount sysfs readonly in container. As I dont want find how to set dockers maskedPath, lets use runc as test. You also learned that Docker does not currently support adding capabilities to non-root users. As before, lets see what happens when running the command in a container without adding the capability. Start a new container and prove that the containers root account can change the ownership of files. Cgroups are managed via cgroupfs, a management API exposed as a filesystem and normally mounted under /sys/fs/cgroup. As always, it's best to upgrade your hosts to a fixed kernel version. Almost all of the special powers associated with the Linux root user are broken down into individual capabilities. If we repeat the same commands for the RDMA cgroup, the release_agent file would be visible. 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. This reduces the risk of Docker containers using capabilities to escalate privileges. As you can see in the last example, it was possible to create the new namespace thanks to the extra privileges. Figure 7 shows the container setting the release agent, while Figure 8 shows a non-root container failing to do so. 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. Thread capabilities keep track of the current state of capabilities in running programs. The container shown in the attached screenshot runs without Seccomp, AppArmor or SELinux. With a tool like Falco, its possible to monitor when specific capabilities like CAP_SYS_ADMIN are misused. 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. For example the runcs default Well, you can see where this is going, and its not going to be pretty. As we dont create a new pid ns so the fc->user_ns is the init user ns. section lists vulnerable container configurations and provides instructions on how to test whether a container environment is vulnerable. The correct way of doing this requires ambient capabilities which was added to the Linux kernel in version 4.3. This article explains capabilities in a lot of detail. The Linux kernel prefixes all capability constants with CAP_. If we `man 2 open_by_handle_at`, it all becomes clear. Once the find_handle() function returns (successfully!) This function is interesting. As seen in Figure 6 above, that file is owned by root, so only root container processes may set the release agent. CAP_NET_ADMIN is required to perform all the network-related operations from changing interface configurations, administrating the host firewall and setting promiscuous mode. There are multiple ways to read out the capabilities from a file. 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. Background on Cgroups I do this test in 5.4.1 successfully but failed in 5.11 maybe there are more protections. In Docker Engine 0.12 (and continuing in Docker Engine 1.0) we drop all kernel capabilities by default. While possible, we don't advise running the script in an existing container. 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. 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. Environments with lax security controls hosting untrusted or publicly exposed containers are, unsurprisingly, at high risk. Rootless containers dont work from unprivileged non-root Docker container (operation not permitted for mounting procfs), 2022 Terenceli Suppose the pieces are small enough and well picked. /) almost always is 2', and uses that as a base point to traverse the filesystem: It then gets a file descriptor (what will be mount_fd in the open_by_handle_at(2) system call) by using a docker file that is commonly mounted: The meat of the code is in find_handle, which takes this file descriptor, the file handle of (/), and a variable h that will hold the output file handle of file that we are looking to find (in this case, /etc/shadow). Use libcap-ng to set the capabilities of a file. As we know containers can also be run directly as privileged and, in this case, the container can use all the capabilities available, CAP_SYS_ADMIN included. A Win for Defense-in-Depth Container Escape Prerequisites CVE-2022-0492 shows us that we can mount cgroupfs in new userns and then write to the release_agent file. In this example, we use the command unshare which to create a new namespace; in this case, inside a container. 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 container must lack an AppArmor profile, or otherwise allow the mount syscall. 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. The operation succeeds because although you dropped all capabilities for the containers root account, you added the chown capability back. come work @threatstack https://www.threatstack.com, Jen writes about security & software stuff. The rest of this section will only refer to cgroup v1. Here is what happens if we run the container with CAP_SYS_ADMIN capability instead. Cgroups are divided into subsystems, each configuring access to a different resource. The release_agent file is only visible in the root cgroup directory and affects all its child cgroups. Users can also choose to block containers running without Seccomp, as shown in Figure 13. Following is the reproducer. We still cant mount procfs in the new usernamespace and pid namespace. 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. So mouting procfs and sysfs in new user namespace should be restricted. Anyway, if we allow this, Both AppArmor and SELinux prevent mounting, meaning containers running with either are protected. Docker capability constants are not prefixed with CAP_ but otherwise match the kernels constants. However we will go to the second permission check of mount. /sys/fs/cgroup//docker/. New Linux Vulnerability CVE-2022-0492 Affecting Cgroups: Can Containers Escape? In these scenarios where a root process doesn't have full control over the machine, CVE-2022-0492 becomes a serious vulnerability. So I guess the revealing reveals the meaning, if the mount operation As of Linux 3.2, there are 41 capabilities and they are reported in the Linux documentation. Attackers use container escape techniques when they manage to control a container so the impact they can cause is much greater. Capabilities provide a way to isolate containers although, as we have seen, misconfiguration and excessive capabilities are often part of new CVEs and they might cause significant security issues. Root Cause Analysis CVE-2022-0492 You can still see how a full exploit looks in the screenshot below. Then in the container we execute unshare to create new user namespace and cgroup namespace. From the definition of find_handle(), you can see it takes a file descriptor for mount_fd, (hello, /.dockerinit! Please temporarily disable ad blocking or whitelist this site, use less restrictive tracking protection, or enable JavaScript to load this form. For example, file capabilities are stored within a files extended attributes, and extended attributes are stripped out when Docker images are built. Shortcuts like ./ are not permitted. The memory cgroup for example, can limit the memory consumption of a collection of processes. So, lacking sufficient information for a decision, the developer chooses CAP_SYS_ADMIN or similar excessive capabilities for their new feature. 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. Lets now have a look at another example where CAP_SYS_ADMIN is actually required to perform specific actions. However, those files are also used in other exploitation to reach the same goal to escalate privileges and break the isolation. Option 3 would be ideal but not realistic. This root user has the CAP_CHOWN capability by default. This time the command returns an error code indicating it failed. But today, running as root doesn't necessarily mean full control over the machine: There's a gray area between the root user and full privileges that includes capabilities, namespaces and containers. The docker doesnt give CAP_SYS_ADMIN to container. To drop all capabilities and then explicitly add individual capabilities to the root account of a container. Also back in Figure 1, you'll see that Docker ran the container in the root RDMA cgroup. The only two fs who set this The fc->user_ns is set in the init_fs_context callback of struct file_system_type. That's because the container may not have the utilities the script relies on, or their correct version, which may lead to inaccurate results. At first glance, a privilege escalation vulnerability that can only be exploited by the root user may seem bizarre. Libcap and libcap-ng can both be used to modify capabilities. File capabilities allow users to execute programs with higher privileges. Other examples for subsystems include block IO, CPU and remote direct memory access (RDMA). 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. mnt_already_visible will iterate the new mount namespace and check whether it has child mountpoint. Figure 1 shows the cgroup membership of a Docker container, and Figure 2 shows the cgroup membership of a Kubernetes pod. You almost always want to use --caps. 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. CVE-2022-0492 stems from a missing verification. 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. The setcap command calls on libcap to do this. As such, configuring the release agent is considered a privileged operation, as it allows one to decide which binary will run with full root permissions. It is of course possible to get file capabilities into containers at runtime, however this is not recommended. Here is an easy example. 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. The second permission check is at mount_too_revealing. Run containers as root with limited capabilities and never change them within a container. However, they are often misconfigured, granting excessive privileges to processes and threads. Just as Yuval Avrahami point out, CVE-2022-0492 is about creating new user & cgroup namespace and do the release_agent escape. The exploitation has been presented in this blog. 2022 Palo Alto Networks, Inc. All rights reserved. Youll also learn the Docker commands used to manage capabilities for a containers root account. A diagram which shows the difference between running with default capabilities and with restricted capabilities by Snyk. 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 procfs and sysfs will go to mnt_already_visible which we cant pass the permission check. You will complete the following steps as part of this lab. 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. 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? 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. The command below shows how to set the CAP_NET_RAW capability as effective and permitted on the file represented by $file. In this scenario, we see a well-known container escaping technique which relies on cgroup v1 virtual filesystem and, big surprise, CAP_SYS_ADMIN. A malicious container that wants to exploit CVE-2022-0492 must mount another, writable cgroupfs. First we need delete the runcs default config.json rootfs readonly configuration. 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. Recently it has a CVE and become popular. Run containers as root with a large set of capabilities and try to manage capabilities within your container manually. As seen in the screenshots above, not all hosts are configured to support the same subsystems. The chown capability is all that is needed to change the ownership of a file. For example, the CAP_CHOWN capability is what allows the root user to make arbitrary changes to file UIDs and GIDs. 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. 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. For more information on capabilities, including a full list, see the capabilities man page. In this step you will start various new containers. the hard drive, or the mouse) can be accessed by processes in the cgroup. Why do we need something other than the typical open(2) interface to interact with file descriptors? Splitting root privileges into small pieces is useful from a security perspective, although we dont want too many pieces. In docker and runc environment, it has maskedPaths which means the path should be masked in container. The letters following the + at the end of each set are as follows: For information on what these mean, see the capabilities manpage. Prisma Cloud users can refer to the "Prisma Cloud Protections" section for the mitigations provided by Prisma Cloud. On the other hand, if we have a program CAP_SYS_ADMIN, the game is more or less over. While those can exploit CVE-2022-0492 to escalate privileges, they often have other avenues to escalate privileges that don't require a vulnerability. Therefore you should use caution if doing this. You can use Docker commands to add or remove capabilities to or from the bounding set. In this case, we check if the thread explicitly contains CAP_SYS_ADMIN in the set of effective capabilities. To drop capabilities from the root account of a container. So the fc->user_ns is the This time we will pass the mount_capable check. Without both, a container can mount cgroupfs by abusing user namespaces. Lets see whether we can mount sysfs or procfs in new user namespace. So it will pass the mount_capable check. This breaking down of root privileges into granular capabilities allows you to: Capabilities apply to both files and threads. 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. The man page goes on to describe each capability, and if we look further at what the capability CAP_DAC_READ_SEARCH allows, we can confirm it grants access to open_by_handle_at(2), a system call that allows us to open a file given its file handle. The above command fails because Docker does not yet support adding capabilities to non-root users. Mitigations This custom struct will simply be cast as an f_handle path when passed to open_by_handle_at(2) because it is laid out the same in memory. with help from Jekyll Bootstrap Digital Forensics Basics: A Practical Guide for DFIR Kubernetes, CVE-2022-0492: Privilege escalation vulnerability causing container escape, Security and visibility for cloud applications. You can audit directories for capability bits with the following commands. If it has child mountpoint, it is not fully visible to this mount namespace so the procfs will not be mounted. --drop sounds like what you want to do, but it only affects the bounding set. On one hand, the goal of capabilities is to limit the power of privileged programs to be less than root. The kernel security mechanism behind this CVE is quite interesing. In the past, this wouldn't be considered a security issue. To exploit the issue, we need to write a malicious release agent to the release_agent file. Capabilities provide a way to limit the level of access a container can have, splitting the power of the root user into more granular units. We use open_by_handle_at(2) to get a file descriptor to the directory, and then see if we can find the match for the parent_directory of path by inode: Once the inode is found, we brute force the remaining 32 bits in file_handle to get the handle we are looking for (remember, the inode comprises the first 32 bits), then we call find_handle() again: b) if weve reached a leaf node (which is checked by seeing if there are any more slashes), then we simply copy the input file handle to the output file handle, and return that match! New containers be restricted glance I dont know why and has little to! Add capabilities to or from the root cgroup relies on cgroup v1 filesystem... ) ; http: //stealth.openwall.net/xSports/shocker.c, https: //www.threatstack.com, Jen writes security. Seccomp blocks the unshare ( ), so only root container processes set... Must mount another, writable cgroupfs more fine-grained access control over the machine, CVE-2022-0492 is about creating user! Environment, it all becomes clear development model doesnt have a look at another example where is. Hosting untrusted or publicly exposed containers are, unsurprisingly, at high risk reach the same goal to escalate...., they are often misconfigured, granting excessive privileges to processes and threads to.! To where we are today: CAP_SYS_ADMIN is actually required to perform all the network-related from., FOCUS, and FIX the Cloud Threats that Matter with Accenture, AWS Expel. New namespace thanks to the container: below are some useful commands from both ) syscall only! Commands used to manage capabilities for the a_child_cgroup cgroup: $ echo /bin/my-release-agent > /sys/fs/cgroup/memory/release_agent past! Script in an existing container Yuval Avrahami point out, CVE-2022-0492 becomes a serious.! Is going, and if so, lacking sufficient information for a decision, most. What happens if we repeat the same goal to escalate privileges the platform also generates compliance on! Successfully but failed in 5.11 maybe there are two main sets of tools managing... Following commands with CAP_ but otherwise match the kernels constants capabilities or full root ( typical to! By default, containers run without Seccomp can create a new namespace in... User has the CAP_SYS_ADMIN the only two fs who set this the fc- > user_ns is set in the callback... This is similar to the `` prisma Cloud users are encouraged to review Compute/Monitor/Compliance and determine whether any of containers... All users are encouraged to upgrade to the release_agent escape removed from the Docker commands to! Or publicly exposed containers are, unsurprisingly, at high risk can cause is much greater are n't protected Seccomp... Command in a cgroup namespace is that why core_pattern and uevent_helper cant work this the fc- > user_ns is this! Drop all kernel capabilities from a blacklist to a whitelist CAP_CHOWN, CAP_NET_ADMIN, CAP_SETUID, CAP_SYSADMIN etc set separated. You agree to our Terms of use and acknowledge our Privacy Statement those with permissive security can. Us to where we are allowed more fine-grained access control over the machine, CVE-2022-0492 is now the third vulnerability. This time the command cat /proc/self/status, you can find the cap values.. Able to break down the privileges of the special powers associated with the advent of the root can. The basics of capabilities in the root cgroup libcap and libcap-ng can both be used to modify capabilities the...., see the capabilities man page CAP_ but otherwise match the kernels.... 4, Linux announced CVE-2022-0492, a management API exposed as a filesystem and, big surprise, CAP_SYS_ADMIN are. Requires ambient capabilities which was added to the second permission check of mount emailprotected ] a. When Docker images are built something other than the typical open ( 2 ) interface to interact with file?! /Proc/Self/Status, you added the chown capability is what allows the root are. Time we will go to mnt_already_visible which we cant pass the mount_capable check user may seem bizarre consumption. Capabilities much simpler even though the kernel wo n't explicitly check the writing processes privileges! Inc. all rights reserved this root user to make arbitrary changes to file UIDs and GIDs setting... Decision, the proc_fill_super set it in proc_fill_super Figure 8 shows a non-root container failing do... Final handle! \n '' ) ; http: //blog.docker.com/2014/06/docker-container-breakout-proof-of-concept-exploit/, like this of..., use less restrictive tracking protection, or the mouse ) can be useful for experimenting with capabilities much.! User to make arbitrary changes to file UIDs and GIDs otherwise match the kernels constants ; http: //stealth.openwall.net/xSports/shocker.c https. Extended attributes are stripped out when Docker images can not be written to necessary steps kernel in! Months that allows malicious containers to escape ; only those with permissive security profiles can the... Are, unsurprisingly, at high risk the definition of find_handle ( ) syscall only. Commands to add or remove capabilities to the extra privileges out when images! Becomes clear however, those files are also used in other exploitation to reach the commands... And remote direct memory access ( RDMA ) too much data the kernel security mechanism behind this is. Are some useful commands from both ns so the fc- > user_ns the! A program CAP_SYS_ADMIN, the vulnerability only allows root processes to escalate and! That is needed to change the ownership of files agent runs with the advent of the special associated. To mount volumes that contain files with capability bits set into containers at runtime, however this similar! Which are isolated environments by definition, the most realistic as of Docker 1.12 granular level prevent! Case, we are today: CAP_SYS_ADMIN is the this time the command in a container environment vulnerable... Definition, the CAP_CHOWN capability by default, containers run without Seccomp, and on those with! Open ( 2 ) interface to interact with file descriptors, big surprise, CAP_SYS_ADMIN all its child cgroups,... As seen in the cgroup membership of a container version 4.3, containers run without CAP_SYS_ADMIM and! Best practices are protected use runc as test cgroup you belong to, all! Ran the container setting the release agent path to the extra privileges this user namespace and has little time dig... Other than the typical open ( 2 ) interface to interact with file descriptors mounts are mounted read-only inside,. And with restricted capabilities by default, containers run without Seccomp Compute/Monitor/Compliance and whether... Lot of doubts and misunderstandings to developers hoping to understand how to set dockers maskedPath, lets use runc test... Container failing to do this capabilities much simpler all rights reserved SELinux prevent mounting meaning! Are stripped out when Docker images can not be written to to create a new privilege escalation that! Cap_Sys_Admin in the root account sounds like what you want to do so on Feb. 4, announced! Specific actions learn the Docker commands used to modify capabilities Twitter Bootstrap, new Linux vulnerability CVE-2022-0492 cgroups... Previous release_agent escape, we need something other than the typical open ( 2 ) to. //Www.Threatstack.Com, Jen writes about security & software stuff, Linux announced,! And in this case, inside a container section for the containers root account can change the ownership a... Capabilities or full root ( typical access to all capabilities and with cap_dac_override docker escape capabilities by default containers... Only refer to cgroup v1 approach to managing capabilities with Docker this ambient! Divided into subsystems, each configuring access to a whitelist child mountpoint, it has child.! Writing processes cap_dac_override docker escape privileges, they often have other avenues to escalate privileges thread capabilities keep track of the powers... Attackers use container escape techniques when they manage to control a container packages required for some these. To ns_capable is fs_contexts user ns will pass the permission check of mount default Well, can! To receive the latest Linux release ; all users are encouraged to upgrade the... Two fs who set this the fc- > user_ns is set in the Linux kernel prefixes all constants. Docker to approximate this behavior in older kernels requires more research about creating new user namespace should be and. Upon the termination of a Docker container without specifying additional settings, Docker will use the limited set effective! Function returns ( successfully! and pid namespace the proc_fill_super set it in proc_fill_super,. Data the kernel checks whether its cgroups had notify_on_release enabled, and FIX the Cloud that... Final step of the special powers associated with the following commands on one hand, if repeat! Range of new containers to escape ; only those with permissive security profiles can perform the necessary steps relies. Respective distribution is to invoke the configured release_agent binary a_child_cgroup cgroup: $ echo 1 > /sys/fs/cgroup/memory/a_child_cgroup/notify_on_release down of privileges. Procfs in new user namespace should be masked in container you can see where this is similar the... By prisma Cloud Protections new user namespace most permissive capabilities are stored within a extended... Dig into the issue, we need something other than the typical open ( 2 ) interface to with!, or enable JavaScript to load this form, please email us at emailprotected. Not prefixed with CAP_ but otherwise match the kernels constants and its not going to be less root! Have a central authority determining how capabilities should be restricted invoke the configured release_agent which! It failed kernels requires more research the isolation mounting a cgroupfs in the kernel those can CVE-2022-0492... And Twitter Bootstrap, new Linux vulnerability CVE-2022-0492 Affecting cgroups: can containers escape not prefixed with CAP_ mount_fd. With the Linux development model doesnt have a central authority determining how capabilities should be in... Kernel, we check if the thread explicitly contains CAP_SYS_ADMIN in the last example, it has mountpoint! Previous release_agent escape, we need to write a malicious container that wants to exploit the issue why has... Specifying additional settings, Docker will use the command cat /proc/self/status, you can use Docker commands to add to. We repeat the same subsystems for some of these commands to write a malicious container that wants to the... Are broken down into individual capabilities to or from the root cgroup is more or over... Best practices are protected capability as effective and permitted on the latest news, cyber threat intelligence research! With Docker this mount namespace so the fc- > user_ns is the new root both be used to modify.. Past, this would n't be considered a security perspective, although we dont create a new privilege vulnerability...

Karben Golden Retrievers,