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docker pull cgr.dev/chainguard/cosign
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Sign InMinimalist Wolfi-based Cosign images for signing and verifying images using Sigstore.
Chainguard Images are regularly-updated, minimal container images with low-to-zero CVEs.
This image is available on cgr.dev
:
Be sure to replace the ORGANIZATION
placeholder with the name used for your organization's private repository within the Chainguard registry.
Like most other Chainguard Images, the Cosign image has few-to-zero CVEs and does not run as the root user.
You can use the Cosign image to sign and verify container images via Docker or through automated workflows such as GitHub Actions.
To verify an image signature, use the image to run Cosign's verify
command. As of Cosign 2.0, Cosign defaults to using Sigstore's keyless mode, you'll need to also specify the OIDC issuer and signer identity to tell Cosign who you trust for the verification process.
For convenience, you can export those values as environment variables in your shell, and then tell Docker to pass those environment variables into the running Cosign container:
The following example uses the Cosign image to verify the signature of the Cosign image itself:
The following GitHub Action will log into the registry, push an image, and then sign it with Cosign:
Another common use case for Cosign is attesting to an image's SBOM (software bill of materials). The following command creates an attestation of type spdxjson
for an image based on the provided SBOM file and image digest:
A detailed guide on how to sign an SBOM with Cosign is available on Chainguard Academy.
Cosign can also be used to verify the identity of the person or entity issuing an attestation. To verify that an attestation was issued by a specific entity, we use the cosign verify-attestation
command, specifying the email address of the issuer:
If the identity is successfully verified, an initial message similar to the following is printed to stderr:
The following environment variables are required when verifying a container image signature:
COSIGN_CERTIFICATE_OIDC_ISSUER
: Trusted OIDC issuer, example: https://token.actions.githubusercontent.com
COSIGN_CERTIFICATE_IDENTITY
: Trusted certificate identity, example: https://github.com/chainguard-images/images/.github/workflows/release.yaml@refs/heads/main
To obtain detailed information about the environment, you can run the cosign env
command:
You'll get output similar to this, containing the environment variables used to configure Cosign:
Chainguard Academy: Verifying Chainguard Images and Metadata Signatures with Cosign
Video: Signing and Verifying Container Images With Sigstore Cosign and Kyverno
If you have a Zendesk account (typically set up for you by your Customer Success Manager) you can reach out to Chainguard's Customer Success team through our Zendesk portal.
Chainguard Images are a collection of container images designed for security and minimalism.
Many Chainguard Images are distroless; they contain only an open-source application and its runtime dependencies. These images do not even contain a shell or package manager. Chainguard Images are built with Wolfi, our Linux undistro designed to produce container images that meet the requirements of a secure software supply chain.
The main features of Chainguard Images include:
-dev
VariantsAs mentioned previously, Chainguard’s distroless Images have no shell or package manager by default. This is great for security, but sometimes you need these things, especially in builder images. For those cases, most (but not all) Chainguard Images come paired with a -dev
variant which does include a shell and package manager.
Although the -dev
image variants have similar security features as their distroless versions, such as complete SBOMs and signatures, they feature additional software that is typically not necessary in production environments. The general recommendation is to use the -dev
variants only to build the application and then copy all application artifacts into a distroless image, which will result in a final container image that has a minimal attack surface and won’t allow package installations or logins.
That being said, it’s worth noting that -dev
variants of Chainguard Images are completely fine to run in production environments. After all, the -dev
variants are still more secure than many popular container images based on fully-featured operating systems such as Debian and Ubuntu since they carry less software, follow a more frequent patch cadence, and offer attestations for what they include.
To better understand how to work with Chainguard Images, we encourage you to visit Chainguard Academy, our documentation and education platform.
Chainguard Images contain software packages that are direct or transitive dependencies. The following licenses were found in the "latest" version of this image:
Apache-2.0
GCC-exception-3.1
GPL-2.0-only
GPL-2.0-or-later
GPL-3.0-or-later
LGPL-2.1-or-later
MIT
For a complete list of licenses, please refer to this Image's SBOM.
Software license agreementA FIPS validated version of this image is available for FedRAMP compliance. STIG is included with FIPS image.