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cert-manager Signature Verification

To help prevent supply chain attacks, some cert-manager release artifacts are cryptographically signed so you can be sure that the version of cert-manager you're about to install is actually built by and provided by the cert-manager maintainers.

This signing is vitally important if for any reason you need to use a mirrored version of cert-manager; it allows you to confirm that the mirror hasn't tampered with the code you're about to install.

Signing keys required for verification are all available on this website, but the actual key that you need might depend on the artifact you're trying to validate in the future. At the time of writing, all signing is done using the same underlying key.

Container Images / Cosign

For all cert-manager versions from v1.8.0 and later, cert-manager container images are signed and verifiable using cosign.

IMAGE_TAG=v1.16.1  # change as needed
KEY=https://cert-manager.io/public-keys/cert-manager-pubkey-2021-09-20.pem
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-acmesolver:$IMAGE_TAG
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-cainjector:$IMAGE_TAG
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-ctl:$IMAGE_TAG
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-startupapicheck:$IMAGE_TAG
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-controller:$IMAGE_TAG
cosign verify --signature-digest-algorithm sha512 --insecure-ignore-tlog --key $KEY quay.io/jetstack/cert-manager-webhook:$IMAGE_TAG

For a more fully-featured signature verification process in Kubernetes, check out connaisseur.

Why --insecure-ignore-tlog?

We'd rather not have an flag which says insecure in the verification command and it's our intention to fix that some time in the future. For now, ignoring the transparency log makes verification work.

Note that the cert-manager key is stored in Google Cloud KMS, and is used by Google Cloud Build only when a cert-manager release is being signed.

Helm Charts

Helm requires the use of PGP for verification; the key format is different.

Trying to use "plain" PEM encoded public keys during verification will fail.

For all cert-manager versions from v1.6.0 and later, Helm charts are signed and verifiable through the Helm CLI.

The easiest way to verify is to grab the GPG keyring directly, which can then be passed into helm verify like so:

curl -sSL https://cert-manager.io/public-keys/cert-manager-keyring-2021-09-20-1020CF3C033D4F35BAE1C19E1226061C665DF13E.gpg > cert-manager-keyring-2021-09-20-1020CF3C033D4F35BAE1C19E1226061C665DF13E.gpg
helm verify --keyring cert-manager-keyring-2021-09-20-1020CF3C033D4F35BAE1C19E1226061C665DF13E.gpg /path/to/cert-manager-vx.y.z.tgz

If you know what you're doing and you want the signing key in a format that's easy to import into GPG, it's available in an ASCII armored version: