notation.md

Container Image Sign and Verify with notation tool

⚡ Requirement	nerdctl >= 1.3.0

notation is a project to add signatures as standard items in the registry ecosystem, and to build a set of simple tooling for signing and verifying these signatures.

You can enable container signing and verifying features with push and pull commands of nerdctl by using notation under the hood with make use of flags --sign while pushing the container image, and --verify while pulling the container image.

• Ensure notation executable in your $PATH.
• You can install notation by following this page: https://notaryproject.dev/docs/user-guides/installation/cli/
• Notation follows the RC of OCI spec v1.1.0. Follow the instruction to set up the local registry with the compliance for testing purpose.

Prepare your environment:

# Create a sample Dockerfile
$ cat <<EOF | tee Dockerfile.dummy
FROM alpine:latest
CMD [ "echo", "Hello World" ]
EOF

Please do not forget, we won't be validating the base images, which is alpine:latest in this case, of the container image that was built on, we'll only verify the container image itself once we sign it.

# Build the image
$ nerdctl build -t localhost:5000/my-test -f Dockerfile.dummy .

# Generate a key-pair in notation's key store and trust store
$ notation cert generate-test --default "test"

# Confirm the signing key is correctly configured. Key name with a * prefix is the default key.
$ notation key ls

# Confirm the certificate is stored in the trust store.
$ notation cert ls

Sign the container image while pushing:

# Sign the image and store the signature in the registry
$ nerdctl push --sign=notation --notation-key-name test localhost:5000/my-test

Verify the container image while pulling:

REMINDER: Image won't be pulled if there are no matching signatures with the cert in the trust policy in case you passed --verify flag.

# Create `trustpolicy.json` under $XDG_CONFIG_HOME/notation (XDG_CONFIG_HOME is ~/.config below)
cat <<EOF | tee ~/.config/notation/trustpolicy.json
{
    "version": "1.0",
    "trustPolicies": [
        {
            "name": "test-images",
            "registryScopes": [ "*" ],
            "signatureVerification": {
                "level" : "strict"
            },
            "trustStores": [ "ca:test" ],
            "trustedIdentities": [
                "*"
            ]
        }
    ]
}
EOF

# Verify the image
$ nerdctl pull --verify=notation localhost:5000/my-test

# You can not verify the image if it is not signed by the cert in the trust policy
$ nerdctl pull --verify=notation localhost:5000/my-test-bad