SEV-SNP Attestation Shim

A reverse proxy service that terminates TLS and exposes an AMD SEV-SNP attestation report over HTTP.

Features

• TLS termination with automatic certificate management
• AMD SEV-SNP attestation endpoint
• API key validation through an external key server
• Rate limiting per API key
• Path-based access control

Configuration

domain: example.com                # Domain name for TLS certificate (leave empty to generate a self-signed certificate)
upstream-port: 8080                # Required: upstream HTTP port
metrics-port: 8081                 # Optional: Prometheus metrics port (disabled if empty)
listen-port: 443                   # Port to listen on (default: 443)
paths:                             # Optional: List of allowed paths (default: all)
  - /api/v1
  - /api/v2
api-signer-public-key: "..."       # Optional: Public key of API key signer
staging-ca: false                  # Use Let's Encrypt staging environment
rate-limit: 1                      # Requests per second per API key
rate-burst: 2                      # Maximum burst size for rate limiting
verbose: true                      # Debug logging

Attestation

The shim provides an attestation endpoint at /.well-known/tinfoil-attestation that returns a signed SEV-SNP attestation report. The report includes a SHA-256 hash of the TLS certificate in the user data field, allowing clients to bind a TLS connection to an enclave measurement.

Authorization

Authorization is shared between the sev-shim and an external authorization provider. The only shared data (not a secret) is the public key of the API key signer. To require authorization and optionally enable rate limiting, set the api-signer-public-key option to the public key of the API key signer. See the example key signer for a simple implementation.

For each every request to the upstream (the attestation endpoint is excluded from authorization), the shim will check if the Authorization: Bearer ... header is set and attempt to verify the token agains the configured public key. The signed key includes a validity period that is controlled by the key signer.

Rate Limiting

The rate-limit and rate-burst options can be used to limit the number of requests per second per API key.