Finish the refactor which was partially completed with commit
34536c498d, passing around IdentityMapping structs instead of pairs of
[]IDMap slices.
Existing code which uses []IDMap relies on zero-valued fields to be
valid, empty mappings. So in order to successfully finish the
refactoring without introducing bugs, their replacement therefore also
needs to have a useful zero value which represents an empty mapping.
Change IdentityMapping to be a pass-by-value type so that there are no
nil pointers to worry about.
The functionality provided by the deprecated NewIDMappingsFromMaps
function is required by unit tests to to construct arbitrary
IdentityMapping values. And the daemon will always need to access the
mappings to pass them to the Linux kernel. Accommodate these use cases
by exporting the struct fields instead. BuildKit currently depends on
the UIDs and GIDs methods so we cannot get rid of them yet.
Signed-off-by: Cory Snider <csnider@mirantis.com>
pkg/system historically has been a bit of a kitchen-sink of things that were
somewhat "system" related, but didn't have a good place for. EnsureRemoveAll()
is one of those utilities. EnsureRemoveAll() is used to both unmount and remove
a path, for which it depends on both github.com/moby/sys/mount, which in turn
depends on github.com/moby/sys/mountinfo.
pkg/system is imported in the CLI, but neither EnsureRemoveAll(), nor any of its
moby/sys dependencies are used on the client side, so let's move this function
somewhere else, to remove those dependencies from the CLI.
I looked for plausible locations that were related; it's used in:
- daemon
- daemon/graphdriver/XXX/
- plugin
I considered moving it into a (e.g.) "utils" package within graphdriver (but not
a huge fan of "utils" packages), and given that it felt (mostly) related to
cleaning up container filesystems, I decided to move it there.
Some things to follow-up on after this:
- Verify if this function is still needed (it feels a bit like a big hammer in
a "YOLO, let's try some things just in case it fails")
- Perhaps it should be integrated in `containerfs.Remove()` (so that it's used
automatically)
- Look if there's other implementations (and if they should be consolidated),
although (e.g.) the one in containerd is a copy of ours:
https://github.com/containerd/containerd/blob/v1.5.9/pkg/cri/server/helpers_linux.go#L200
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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>
also renamed the non-windows variant of this file to be
consistent with other files in this package
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This implements chown support on Windows. Built-in accounts as well
as accounts included in the SAM database of the container are supported.
NOTE: IDPair is now named Identity and IDMappings is now named
IdentityMapping.
The following are valid examples:
ADD --chown=Guest . <some directory>
COPY --chown=Administrator . <some directory>
COPY --chown=Guests . <some directory>
COPY --chown=ContainerUser . <some directory>
On Windows an owner is only granted the permission to read the security
descriptor and read/write the discretionary access control list. This
fix also grants read/write and execute permissions to the owner.
Signed-off-by: Salahuddin Khan <salah@docker.com>
Prevent changing the tar output by setting the format to
PAX and keeping the times truncated.
Without this change the archiver will produce different tar
archives with different hashes with go 1.10.
The addition of the access and changetime timestamps would
also cause diff comparisons to fail.
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The promise package represents a simple enough concurrency pattern that
replicating it in place is sufficient. To end the propagation of this
package, it has been removed and the uses have been inlined.
While this code could likely be refactored to be simpler without the
package, the changes have been minimized to reduce the possibility of
defects. Someone else may want to do further refactoring to remove
closures and reduce the number of goroutines in use.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This enables docker cp and ADD/COPY docker build support for LCOW.
Originally, the graphdriver.Get() interface returned a local path
to the container root filesystem. This does not work for LCOW, so
the Get() method now returns an interface that LCOW implements to
support copying to and from the container.
Signed-off-by: Akash Gupta <akagup@microsoft.com>
