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

# CASAN Plan-16 SEC-23 (23.10, MT-02) — per-tenant encryption at rest (local-key MVP).
#
# Sensitive state (audit / telemetry) is encrypted with a PER-TENANT key so tenant B
# — or an admin of B — cannot read tenant A's plaintext on disk. The key lives under
# the tenant partition (0600) and differs per tenant, so a ciphertext produced by A
# cannot be decrypted with B's key. Production form uses Vault Transit (23.11, needs
# infra); this is the offline form.
#
# Usage:
#   tenant-crypt.sh encrypt <plaintext-file> <ciphertext-file>
#   tenant-crypt.sh decrypt <ciphertext-file> <plaintext-file>
# Env: CASAN_TENANT_ID (key is tenant-specific; prod requires it — tenant-store).
# Exit: 0 ok · 2 crypto failure (e.g. wrong tenant key) · 3 tenant/key/openssl error · 64 usage.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
TS="$SCRIPT_DIR/tenant-store.sh"

CMD="${1:-}"; IN="${2:-}"; OUT="${3:-}"
command -v openssl >/dev/null 2>&1 || { echo "TENANT_CRYPT_OPENSSL_UNAVAILABLE" >&2; exit 3; }
[[ -n "$CMD" && -n "$IN" && -n "$OUT" ]] || { echo "usage: tenant-crypt.sh {encrypt|decrypt} <in> <out>" >&2; exit 64; }
[[ -f "$IN" ]] || { echo "TENANT_CRYPT_INPUT_MISSING file=$IN" >&2; exit 3; }

# Per-tenant key (created once, 0600). tenant-store fails closed on an invalid/missing
# tenant in prod; in dev it resolves under the 'default' tenant.
KEYFILE="$(bash "$TS" resolve keys/at-rest.key 2>/dev/null)" || { echo "TENANT_CRYPT_DENIED (tenant unresolved)" >&2; exit 3; }
if [[ ! -f "$KEYFILE" ]]; then
  openssl rand -base64 48 > "$KEYFILE" 2>/dev/null || { echo "TENANT_CRYPT_KEYGEN_FAILED" >&2; exit 3; }
  chmod 600 "$KEYFILE" 2>/dev/null || true
fi

case "$CMD" in
  encrypt)
    if openssl enc -aes-256-cbc -pbkdf2 -salt -in "$IN" -out "$OUT" -pass "file:$KEYFILE" 2>/dev/null; then
      echo "TENANT_ENCRYPTED out=$OUT"
      exit 0
    fi
    echo "TENANT_ENCRYPT_FAILED" >&2; exit 2
    ;;
  decrypt)
    if openssl enc -d -aes-256-cbc -pbkdf2 -in "$IN" -out "$OUT" -pass "file:$KEYFILE" 2>/dev/null; then
      echo "TENANT_DECRYPTED out=$OUT"
      exit 0
    fi
    rm -f "$OUT" 2>/dev/null || true
    echo "TENANT_DECRYPT_FAILED (wrong tenant key or corrupt ciphertext)" >&2; exit 2
    ;;
  *)
    echo "Usage: tenant-crypt.sh {encrypt|decrypt} <in> <out>" >&2
    exit 64
    ;;
esac