Standards

Standards

Open Container Initiative (OCI)

Specifications:

• Runtime
• Image
• Distribution

runc - reference implementation of runtime spec

Founded in 2015 by leaders in the container industry

Version 1.0 was release in 2020

Currently 29 members

Technical oversight commitee from 8 companies

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Scope of this talk

Overview of OCI specs w.r.t. image distribution

How does an OCI registry work

Image storage

APIs

What does the future hold

Generic artifacts

Relationships between artifacts

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How registries work

Typical workflow interacting with a container registry

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How registries work internally

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Media types

OCI defines new media types

Widespread adoption of OCI media types

What	OCI	Docker
Image Index	vnd.oci.image.index.v1+json	vnd.docker.distribution.manifest.list.v2+json
Image Manifest	vnd.oci.image.manifest.v1+json	vnd.docker.distribution.manifest.v2+json
Image Config	vnd.oci.image.config.v1+json	vnd.docker.container.image.v1+json
Image Layer	vnd.oci.image.layer.v1.tar+gzip	vnd.docker.image.rootfs.diff.tar.gzip

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Accept header

Tell registry which content to return

Manifests can only be image index or image manifest

Single Accept header

Content type must be known beforehand

Multiple Accept headers

Content types will be checked in order

Demo

Control which media type is returned

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How it started

What if we used new media types?!

OCI Registries as Storage (ORaS)

Initial project to store artifacts in OCI registries

Very low-level

Official guidance for artifacts

Demo

Upload generic artifacts to OCI registry

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How it’s going

Existing implementations (excerpt)

Docker App (archived)

Cloud Native Application Bundles (CNAB)

• porter

SBOM for container images

• BuildKit >=0.11.0
• buildx >=0.10.0

Container signatures using sigstore’s cosign

Helm charts

OPA policies

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Generic artifacts in OCI registries

OCI 1.0 already supports artifacts with custom media types

OCI 1.1 addresses generic artifacts…

…as well as linking them

OCI 1.1 is not released yet

Artifacts must include subject field in manifest mentioning the parent

New referrers API manages links to parent artifact

Tooling

Initial implementation in distribution by ORaS

Client tools: oras, trivy, trivy-plugin-referrer, regclient

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Demo

Push image

Sign image, push signature and refer to image

Create SBOM, push it and refer to image

Sign SBOM, push signature and refer to image

Create sarif report, push it and refer to SBOM

Sign sarif report, push signature and refer to sarif report

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Adaption of OCI 1.1

Data as of 2023-01-05 using OCI v1.1.0-rc.1 (diff to v1.1.0-rc.3) updated 2023-11-15 with research

Registry	State	Remarks
Distribution		oras-project/distribution#59
Docker Hub
AWS ECR		looks like it
Azure ACR		announcement
GitHub GCR
Google GAR
Harbor		since v2.9.0
Jfrog Artifactory
Quay		since v3.8.6
zot		since v1.3.4

Legend: unknown, underway, supported, unsupported

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Backwards compatibility

OCI 1.1 accomodates for slow adoption

Artifacts are stored…

• in the same repository as the parent
• with the tag sha256-<sha256>

Find linked artifacts:

1. Enumerate all tags sha256-*
2. Read subject from manifest

Demo

Referrers work even without support for OCI 1.1