Cloud / HELM Interview Questions
What are Helm provenance files and how do you sign charts?
Provenance files provide cryptographic verification that Helm charts come from trusted sources and haven't been tampered with.
Generating GPG key for signing:
# Generate GPG key
gpg --full-generate-key
# Select RSA and RSA, 4096 bits, no expiry
# Export public key
gpg --export --armor "Helm Maintainer" > helm-public.key
# Configure Helm to use GPG key
export HELM_KEY_NAME="Helm Maintainer"
export HELM_KEY_PASSPHRASE_FILE=~/helm-passphrase.txt
Signing a chart during packaging:
# Package and sign chart
helm package --sign --key "Helm Maintainer" --keyring ~/.gnupg/pubring.gpg ./mychart
# Results:
# mychart-1.2.3.tgz
# mychart-1.2.3.tgz.prov # Provenance file
# Verify provenance
helm verify mychart-1.2.3.tgz
# Verify with specific keyring
helm verify --keyring ~/.gnupg/pubring.gpg mychart-1.2.3.tgz
Provenance file contents (PROV file):
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
apiVersion: v1
description: A Helm chart for Kubernetes
name: mychart
version: 1.2.3
...
files:
Chart.yaml: sha256:abc123...
values.yaml: sha256:def456...
templates/deployment.yaml: sha256:ghi789...
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
iQIcBAABCgAGBQJfghkLAAoJEL...
-----END PGP SIGNATURE-----
Repository with signed charts:
# Index with provenance
helm repo index --url https://myrepo.github.io/charts --merge index.yaml .
# Client verification on install
helm install myrepo/mychart --verify
# Configure Helm to always verify
export HELM_VERIFY=always
CI/CD signing automation:
# GitHub Actions signing
- name: Import GPG key
run: |
echo "${{ secrets.GPG_PRIVATE_KEY }}" | gpg --import
echo "${{ secrets.GPG_PASSPHRASE }}" > passphrase.txt
- name: Package and sign chart
run: |
helm package --sign --key "${{ secrets.GPG_KEY_NAME }}" \
--passphrase-file passphrase.txt \
./charts/mychart
- name: Verify signature
run: |
helm verify charts/mychart-*.tgz
Trust management:
# Add trusted keys to keyring
gpg --import trusted-maintainer.key
helm repo add --keyring ~/.gnupg/pubring.gpg myrepo https://myrepo.github.io/charts
# Verify chart dependencies are signed
helm dependency update --verify
Limitations: Provenance doesn't verify the contents of external charts referenced by dependencies. OCI registries support Cosign signatures as alternative.
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