Signing Configs

A signed-Nitro enclave boots only from a config whose signature verifies against the operator/CI public keys baked into the enclave image (CONFIG_SIGNERS, measured into PCR0). You sign one config file: the enclave verifies it, and the chart reads the same file’s values to wire the parent-side proxies — one source of truth, no parent/enclave drift.

Note

Signing is authenticity + authorization, not encryption. The config travels in the clear; the #-comment signature trailer proves a trusted quorum approved these exact bytes. A malicious parent EC2 host cannot forge the approval or strip it without the enclave noticing.

How it flows

direction: down

author: "author config.yaml" { style.fill: "#FFF6EF" }
sign: "sign payload (YubiKey PIV / OpenSSL Ed25519)" { style.fill: "#FFF6EF" }
helm: "helm upgrade --set-file signedConfig=signed.yaml" { style.fill: "#FFF6EF" }

render: "Helm render (single input)"
cm: "ConfigMap: signed bytes, verbatim"
derived: "parent values: egress allowlist + ports (fromYaml)"

parent: "Parent proxy: forwards bytes, NO verify"
enclave: "Enclave: verify vs PCR0-baked CONFIG_SIGNERS"

author -> sign
sign -> helm
helm -> render
render -> cm
render -> derived
cm -> parent: "mount /config/config.yaml"
parent -> enclave: "forward over vsock"
derived -> parent: "wire vsock-proxy + ports"
enclave -> enclave: "boot iff quorum verifies, else refuse"

Prerequisites

1. Signer keys. An operator key on a YubiKey PIV (ECDSA P-256, slot 9c) and/or a software Ed25519 key for CI. Operators use P-256 (not Ed25519) so signing works on any YubiKey 5.x; Ed25519-in-PIV needs firmware ≥ 5.7.

2. Trust manifest baked into the EIF. Your signers’ public keys, threshold, and required IDs live in custody/config-signers.ron, baked into the enclave image at build time (CHAMBER_SIGNERS_FILE) and measured into PCR0. See the manifest format in EKS Enclave Deployment. A signed-Nitro EIF built without it refuses to boot.

Sign and deploy

1. Freeze the config and stamp a generation. bundle --create edits in place, normalizes the signed region to end in exactly one LF, and writes a trailer carrying generation N (monotonic, >= 1). Keep the unsigned original.

   cp config.yaml signed.yaml
   containment-chamber config bundle --file signed.yaml --create --generation N

2. Emit the exact bytes to sign. This is the canonical message DOMAIN ‖ generation ‖ signed_region — domain- and generation-bound, so a signature cannot be replayed across generations.

   containment-chamber config sign-payload --file signed.yaml > payload.bin

3. Sign the payload with each signer. Helper scripts wrap the exact algorithm so you cannot accidentally produce a signature the enclave will reject:

   # YubiKey PIV operator (ECDSA P-256, slot 9c) -> raw DER signature
   scripts/sign-config-piv.sh payload.bin operator-a.sig
   
   # software Ed25519 (CI) -> raw 64-byte signature
   scripts/sign-config-ed25519.sh ci-ed25519.key payload.bin > github-ci.sig

4. Embed each signature into the trailer (base64). Repeatable — run once per signer. The <signer-id> must match an id in config-signers.ron.

   containment-chamber config bundle --file signed.yaml --add operator-a=operator-a.sig
   containment-chamber config bundle --file signed.yaml --add github-ci=github-ci.sig

5. Verify locally (optional, but see the caveat below).

   containment-chamber config verify --file signed.yaml

6. Deploy. --set-file loads the file’s bytes as the signedConfig value, verbatim.

   helm upgrade containment-chamber ./k8s/charts/containment-chamber \
     --set-file signedConfig=signed.yaml

M-of-N quorum

The signed region is frozen at step 1, so every signer runs steps 2–3 against the same payload.bin, and you --add each signature once. The threshold and required-signer IDs come from the baked config-signers.ron, never from the file on the wire.

Signature algorithms

Role	Key	Signature emitted	Helper
operator	YubiKey PIV, ECDSA P-256	DER, over SHA-256(message)	scripts/sign-config-piv.sh
ci	software Ed25519	raw 64-byte, over message	scripts/sign-config-ed25519.sh

The alg is bound to the signer’s manifest entry and is never read from the wire.

How --set-file triggers a rollout

--set-file signedConfig=signed.yaml injects the file’s bytes as an opaque string value — it does not parse the YAML and does not compute any hash. The rolling restart on a config change comes from a separate, chart-side annotation on the pod template:

checksum/config: {{`{{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}`}}

When signedConfig changes, the rendered ConfigMap changes, so its sha256sum changes, so the pod template changes, so helm upgrade performs a rolling restart. Editing a ConfigMap alone never restarts pods — this checksum is what turns a byte change into a redeploy.

config verify is build-relative

Caution

config verify checks the quorum against the CONFIG_SIGNERS manifest baked into the binary you run it with — the same check the enclave runs, but only as trustworthy as that binary’s baked manifest.

• A containment-chamber built without CHAMBER_SIGNERS_FILE has no manifest and config verify errors out (it refuses to validate against nothing).
• A binary built with a different manifest than the EIF verifies against the wrong signer set — a green check locally that the enclave may still reject (or vice versa).

Build the verifier from the same config-signers.ron the EIF was built from — point CHAMBER_SIGNERS_FILE at that file path (not its contents):

# the file in your checkout, or extract the protected base-branch manifest first:
git show origin/main:custody/config-signers.ron > /tmp/config-signers.ron
CHAMBER_SIGNERS_FILE=/tmp/config-signers.ron cargo build --release

Or use the exact release artifact whose PCR0 you are deploying. The enclave’s verification is the authoritative gate; config verify is a pre-flight convenience.

Line endings

Caution

The signed file must use LF line endings. The chart mounts it through a YAML block scalar, and block scalars normalize CRLF to LF — which would alter the signed bytes and fail verification. The chart rejects CRLF at helm template time with an actionable error.