e9bbc41dd1
A copy of Go's archive/tar packge was vendored with a patch applied to mitigate CVE-2019-14271. Vendoring standard library packages is not supported by Go in module-aware mode, which is getting in the way of maintenance. A different approach to mitigate the vulnerability is needed which does not involve vendoring parts of the standard library. glibc implements name service lookups such as users, groups and DNS using a scheme known as Name Service Switch. The services are implemented as modules, shared libraries which glibc dynamically links into the process the first time a function requiring the module is called. This is the crux of the vulnerability: if a process linked against glibc chroots, then calls one of the functions implemented with NSS for the first time, glibc may load NSS modules out of the chrooted filesystem. The API underlying the `docker cp` command is implemented by forking a new process which chroots into the container's rootfs and writes a tar stream of files from the container over standard output. It utilizes the Go standard library's archive/tar package to write the tar stream. It makes use of the tar.FileInfoHeader function to construct a tar.Header value from an fs.FileInfo value. In modern versions of Go on *nix platforms, FileInfoHeader will attempt to resolve the file's UID and GID to their respective user and group names by calling the os/user functions LookupId and LookupGroupId. The cgo implementation of os/user on *nix performs lookups by calling the corresponding libc functions. So when linked against glibc, calls to tar.FileInfoHeader after the process has chrooted into the container's rootfs can have the side effect of loading NSS modules from the container! Without any mitigations, a malicious container image author can trivially get arbitrary code execution by leveraging this vulnerability and escape the chroot (which is not a sandbox) into the host. Mitigate the vulnerability without patching or forking archive/tar by hiding the OS-dependent file info from tar.FileInfoHeader which it needs to perform the lookups. Without that information available it falls back to populating the tar.Header with only the information obtainable directly from the FileInfo value without making any calls into os/user. Fixes #42402 Signed-off-by: Cory Snider <csnider@mirantis.com> |
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| NOTICE | ||
| README.md | ||
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| SECURITY.md | ||
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README.md
The Moby Project
Moby is an open-source project created by Docker to enable and accelerate software containerization.
It provides a "Lego set" of toolkit components, the framework for assembling them into custom container-based systems, and a place for all container enthusiasts and professionals to experiment and exchange ideas. Components include container build tools, a container registry, orchestration tools, a runtime and more, and these can be used as building blocks in conjunction with other tools and projects.
Principles
Moby is an open project guided by strong principles, aiming to be modular, flexible and without too strong an opinion on user experience. It is open to the community to help set its direction.
- Modular: the project includes lots of components that have well-defined functions and APIs that work together.
- Batteries included but swappable: Moby includes enough components to build fully featured container system, but its modular architecture ensures that most of the components can be swapped by different implementations.
- Usable security: Moby provides secure defaults without compromising usability.
- Developer focused: The APIs are intended to be functional and useful to build powerful tools. They are not necessarily intended as end user tools but as components aimed at developers. Documentation and UX is aimed at developers not end users.
Audience
The Moby Project is intended for engineers, integrators and enthusiasts looking to modify, hack, fix, experiment, invent and build systems based on containers. It is not for people looking for a commercially supported system, but for people who want to work and learn with open source code.
Relationship with Docker
The components and tools in the Moby Project are initially the open source components that Docker and the community have built for the Docker Project. New projects can be added if they fit with the community goals. Docker is committed to using Moby as the upstream for the Docker Product. However, other projects are also encouraged to use Moby as an upstream, and to reuse the components in diverse ways, and all these uses will be treated in the same way. External maintainers and contributors are welcomed.
The Moby project is not intended as a location for support or feature requests for Docker products, but as a place for contributors to work on open source code, fix bugs, and make the code more useful. The releases are supported by the maintainers, community and users, on a best efforts basis only, and are not intended for customers who want enterprise or commercial support; Docker EE is the appropriate product for these use cases.
Legal
Brought to you courtesy of our legal counsel. For more context, please see the NOTICE document in this repo.
Use and transfer of Moby may be subject to certain restrictions by the United States and other governments.
It is your responsibility to ensure that your use and/or transfer does not violate applicable laws.
For more information, please see https://www.bis.doc.gov
Licensing
Moby is licensed under the Apache License, Version 2.0. See LICENSE for the full license text.