#!/usr/bin/env bash
set -uo pipefail

# CASAN Plan-16 SEC-23 (23.9, MT-04) — sign + verify the tenant/project registry.
#
# An UNSIGNED registry lets an attacker register a fake tenant or swap another
# tenant's project mapping (bypassing every tenant boundary that trusts it). This
# signs the registry (detached signature) and verifies it on load. A tampered,
# forged (wrong key), or unsigned registry is REFUSED — fail-closed by default.
#
# Usage:
#   tenant-registry-verify.sh sign   <registry-file> <priv-key>
#   tenant-registry-verify.sh verify <registry-file> <pub-key>
# Exit: 0 ok · 2 invalid/tampered/forged · 3 missing signature/file/openssl · 64 usage.
# (Production anchors the signature in KMS — see SEC-02; this is the offline form.)

CMD="${1:-}"; REG="${2:-}"; KEY="${3:-}"
command -v openssl >/dev/null 2>&1 || { echo "REGISTRY_OPENSSL_UNAVAILABLE" >&2; exit 3; }

case "$CMD" in
  sign)
    [[ -f "$REG" && -f "$KEY" ]] || { echo "usage: tenant-registry-verify.sh sign <registry> <priv-key>" >&2; exit 64; }
    if openssl dgst -sha256 -sign "$KEY" -out "$REG.sig" "$REG" 2>/dev/null; then
      echo "REGISTRY_SIGNED file=$REG sig=$REG.sig"
      exit 0
    fi
    echo "REGISTRY_SIGN_FAILED file=$REG" >&2; exit 2
    ;;
  verify)
    [[ -f "$REG" ]] || { echo "REGISTRY_MISSING file=$REG" >&2; exit 3; }
    [[ -f "$KEY" ]] || { echo "REGISTRY_PUBKEY_MISSING key=$KEY" >&2; exit 3; }
    if [[ ! -f "$REG.sig" ]]; then
      # SEC-23/SEC-01: unsigned registry is REFUSED (fail-closed), not trusted.
      echo "REGISTRY_UNSIGNED file=$REG — refusing (fail-closed)" >&2; exit 3
    fi
    if openssl dgst -sha256 -verify "$KEY" -signature "$REG.sig" "$REG" >/dev/null 2>&1; then
      echo "REGISTRY_VERIFIED file=$REG"
      exit 0
    fi
    echo "REGISTRY_INVALID file=$REG — tampered or forged signature" >&2; exit 2
    ;;
  *)
    echo "Usage: tenant-registry-verify.sh {sign|verify} <registry-file> <key>" >&2
    exit 64
    ;;
esac