![]() 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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.. | ||
ci | ||
dockerfile/install | ||
make | ||
test | ||
validate | ||
README.md | ||
dind | ||
generate-authors.sh | ||
generate-swagger-api.sh | ||
generate-test-certs.sh | ||
go-mod-prepare.sh | ||
make.ps1 | ||
make.sh | ||
vendor.sh |
README.md
About
This directory contains a collection of scripts used to build and manage this repository. If there are any issues regarding the intention of a particular script (or even part of a certain script), please reach out to us. It may help us either refine our current scripts, or add on new ones that are appropriate for a given use case.
DinD (dind.sh)
DinD is a wrapper script which allows Docker to be run inside a Docker container. DinD requires the container to be run with privileged mode enabled.
Generate Authors (generate-authors.sh)
Generates AUTHORS; a file with all the names and corresponding emails of individual contributors. AUTHORS can be found in the home directory of this repository.
Make
There are two make files, each with different extensions. Neither are supposed
to be called directly; only invoke make
. Both scripts run inside a Docker
container.
make.ps1
- The Windows native build script that uses PowerShell semantics; it is limited
unlike
hack\make.sh
since it does not provide support for the full set of operations provided by the Linux counterpart,make.sh
. However,make.ps1
does provide support for local Windows development and Windows to Windows CI. More information is found withinmake.ps1
by the author, @jhowardmsft
make.sh
- Referenced via
make test
when running tests on a local machine, or directly referenced when running tests inside a Docker development container. - When running on a local machine,
make test
to run all tests found intest
,test-unit
,test-integration
, andtest-docker-py
on your local machine. The default timeout is set inmake.sh
to 60 minutes (${TIMEOUT:=60m}
), since it currently takes up to an hour to run all of the tests. - When running inside a Docker development container,
hack/make.sh
does not have a single target that runs all the tests. You need to provide a single command line with multiple targets that performs the same thing. An example referenced from Run targets inside a development container:root@5f8630b873fe:/go/src/github.com/moby/moby# hack/make.sh dynbinary binary cross test-unit test-integration test-docker-py
- For more information related to testing outside the scope of this README, refer to Run tests and test documentation
Vendor (vendor.sh)
A shell script that is a wrapper around go mod vendor
.