Package Instance

`docker cp` allows unexpected chmod of host files in Moby Docker Engine
## Impact
A bug was found in Moby (Docker Engine) where attempting to copy files using `docker cp` into a specially-crafted container can result in Unix file permission changes for existing files in the host’s filesystem, widening access to others. This bug does not directly allow files to be read, modified, or executed without an additional cooperating process.

## Patches
This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers do not need to be restarted.

## Workarounds
Ensure you only run trusted containers.

## Credits
The Moby project would like to thank Lei Wang and Ruizhi Xiao for responsibly disclosing this issue in accordance with the [Moby security policy](https://github.com/moby/moby/blob/master/SECURITY.md).

## For more information
If you have any questions or comments about this advisory:

* [Open an issue](https://github.com/moby/moby/issues/new)
* Email us at  security@docker.com  if you think you’ve found a security bug

BuildKit vulnerable to possible host system access from mount stub cleaner
### Impact
A malicious BuildKit frontend or Dockerfile using `RUN --mount` could trick the feature that removes empty files created for the mountpoints into removing a file outside the container, from the host system.

### Patches
The issue has been fixed in v0.12.5

### Workarounds
Avoid using BuildKit frontend from an untrusted source or building an untrusted Dockerfile containing `RUN --mount` feature.

### References

Docker supplementary group permissions not set up properly, allowing attackers to bypass primary group restrictions
Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where supplementary groups are not set up properly. If an attacker has direct access to a container and manipulates their supplementary group access, they may be able to use supplementary group access to bypass primary group restrictions in some cases, potentially gaining access to sensitive information or gaining the ability to execute code in that container.  This bug is fixed in Moby (Docker Engine) 20.10.18. Users should update to this version when it is available. Running containers should be stopped and restarted for the permissions to be fixed. For users unable to upgrade, this problem can be worked around by not using the `"USER $USERNAME"` Dockerfile instruction. Instead by calling `ENTRYPOINT ["su", "-", "user"]` the supplementary groups will be set up properly.

Thanks to Steven Murdoch for reporting this issue.

----

### Impact

If an attacker has direct access to a container and manipulates their supplementary group access, they may be able to use supplementary group access to bypass primary group restrictions in some cases, potentially gaining access to sensitive information or gaining the ability to execute code in that container. 

### Patches

 This bug is fixed in Moby (Docker Engine) 20.10.18. Users should update to this version when it is available.

### Workarounds

This problem can be worked around by not using the `"USER $USERNAME"` Dockerfile instruction. Instead by calling `ENTRYPOINT ["su", "-", "user"]` the supplementary groups will be set up properly.

### References

https://www.benthamsgaze.org/2022/08/22/vulnerability-in-linux-containers-investigation-and-mitigation/

### For more information

If you have any questions or comments about this advisory:

* [Open an issue](https://github.com/moby/moby/issues/new)
* Email us at [security@docker.com](mailto:security@docker.com)

BuildKit vulnerable to possible race condition with accessing subpaths from cache mounts
### Impact
Two malicious build steps running in parallel sharing the same cache mounts with subpaths could cause a race condition that can lead to files from the host system being accessible to the build container.

### Patches
The issue has been fixed in v0.12.5

### Workarounds
Avoid using BuildKit frontend from an untrusted source or building an untrusted Dockerfile containing cache mounts with `--mount=type=cache,source=...` options.

### References
https://www.openwall.com/lists/oss-security/2019/05/28/1

Docker Swarm encrypted overlay network may be unauthenticated
[Moby](https://mobyproject.org/) is an open source container framework developed by Docker Inc. that is distributed as Docker, Mirantis Container Runtime, and various other downstream projects/products. The Moby daemon component (`dockerd`), which is developed as [moby/moby](https://github.com/moby/moby) is commonly referred to as *Docker*.

Swarm Mode, which is compiled in and delivered by default in `dockerd` and is thus present in most major Moby downstreams, is a simple, built-in container orchestrator that is implemented through a combination of [SwarmKit](https://github.com/moby/swarmkit) and supporting network code.

The `overlay` network driver is a core feature of Swarm Mode, providing isolated virtual LANs that allow communication between containers and services across the cluster. This driver is an implementation/user of [VXLAN](https://en.wikipedia.org/wiki/Virtual_Extensible_LAN), which encapsulates link-layer (Ethernet) frames in UDP datagrams that tag the frame with a VXLAN Network ID (VNI) that identifies the originating overlay network. In addition, the overlay network driver supports an optional, off-by-default encrypted mode, which is especially useful when VXLAN packets traverses an untrusted network between nodes.

Encrypted overlay networks function by encapsulating the VXLAN datagrams through the use of the [IPsec Encapsulating Security Payload](https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload) protocol in [Transport mode](https://en.wikipedia.org/wiki/IPsec#Transport_mode). By deploying IPSec encapsulation, encrypted overlay networks gain the additional properties of source authentication through cryptographic proof, data integrity through check-summing, and confidentiality through encryption.

When setting an endpoint up on an encrypted overlay network, Moby installs three [iptables](https://www.netfilter.org/projects/iptables/index.html) (Linux kernel firewall) rules that enforce both incoming and outgoing IPSec. These rules rely on the `u32` iptables extension provided by the `xt_u32` kernel module to directly filter on a VXLAN packet's VNI field, so that IPSec guarantees can be enforced on encrypted overlay networks without interfering with other overlay networks or other users of VXLAN.

[Two iptables rules](https://github.com/moby/libnetwork/blob/d9fae4c73daf76c3b0f77e14b45b8bf612ba764d/drivers/overlay/encryption.go#L230-L234) serve to filter incoming VXLAN datagrams with a VNI that corresponds to an encrypted network and discards unencrypted datagrams. The rules are appended to the end of the `INPUT` filter chain, following any rules that have been previously set by the system administrator. Administrator-set rules take precedence over the rules Moby sets to discard unencrypted VXLAN datagrams, which can potentially admit unencrypted datagrams that should have been discarded.

On Red Hat Enterprise Linux and derivatives such as CentOS and Rocky, the `xt_u32` module has been:
* [moved to the kernel-modules-extra package and no longer installed by default in RHEL 8.3](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/8.3_release_notes/rhel-8-3-0-release#technology-preview_networking)
* [officially deprecated in RHEL 8.6](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/8.6_release_notes/deprecated_functionality#deprecated-functionality_networking)
* [removed completely in RHEL 9](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/considerations_in_adopting_rhel_9/assembly_networking_considerations-in-adopting-rhel-9#ref_firewall-networking_assembly_networking)

These rules are not created when `xt_u32` is unavailable, even though the container is still attached to the network.

## Impact
Encrypted overlay networks on affected configurations silently accept cleartext VXLAN datagrams that are tagged with the VNI of an encrypted overlay network. As a result, it is possible to inject arbitrary Ethernet frames into the encrypted overlay network by encapsulating them in VXLAN datagrams.

The injection of arbitrary Ethernet frames can enable a Denial of Service attack. A sophisticated attacker may be able to establish a UDP or TCP connection by way of the container’s outbound gateway that would otherwise be blocked by a stateful firewall, or carry out other escalations beyond simple injection by smuggling packets into the overlay network.

## Patches
Patches are available in Moby releases 23.0.3, and 20.10.24. As Mirantis Container Runtime's 20.10 releases are numbered differently, users of that platform should update to 20.10.16.

## Workarounds
* Close the VXLAN port (by default, UDP port 4789) to incoming traffic at the Internet boundary (see [GHSA-vwm3-crmr-xfxw](https://github.com/moby/moby/security/advisories/GHSA-vwm3-crmr-xfxw)) to prevent all VXLAN packet injection.
* Ensure that the `xt_u32` kernel module is available on all nodes of the Swarm cluster.

## Background
* [#43382](https://github.com/moby/moby/issues/43382) partially discussed this concern, but did not consider the security implications.
* Mirantis FIELD-5788 essentially duplicates [#43382](https://github.com/moby/moby/issues/43382), and was created six months earlier; it similarly overlooked the security implications.
* [#45118](https://github.com/moby/moby/pull/45118) is the ancestor of the final patches, and was where the security implications were discovered.

## Related
* [CVE-2023-28841: Encrypted overlay network traffic may be unencrypted](https://github.com/moby/moby/security/advisories/GHSA-33pg-m6jh-5237)
* [CVE-2023-28842: Encrypted overlay network with a single endpoint is unauthenticated](https://github.com/moby/moby/security/advisories/GHSA-6wrf-mxfj-pf5p)
* [GHSA-vwm3-crmr-xfxw: The Swarm VXLAN port may be exposed to attack due to ambiguous documentation](https://github.com/moby/moby/security/advisories/GHSA-vwm3-crmr-xfxw)
* [GHSA-gvm4-2qqg-m333: Security issues in encrypted overlay networks](https://github.com/moby/libnetwork/security/advisories/GHSA-gvm4-2qqg-m333) (libnetwork)

Buildkit's interactive containers API does not validate entitlements check
### Impact
In addition to running containers as build steps, BuildKit also provides APIs for running interactive containers based on built images. It was possible to use these APIs to ask BuildKit to run a container with elevated privileges. Normally, running such containers is only allowed if special `security.insecure` entitlement is enabled both by buildkitd configuration and allowed by the user initializing the build request.

### Patches
The issue has been fixed in v0.12.5 .

### Workarounds
Avoid using BuildKit frontends from untrusted sources. A frontend image is usually specified as the `#syntax` line on your Dockerfile, or with `--frontend` flag when using `buildctl build` command.

### References