punktfunk-plugin-index/tools/keygen.ts

#!/usr/bin/env bun
/**
 * Generate an ed25519 signing keypair for the index.
 *
 * Prints the PUBLIC key in the exact form the host pins (`ed25519:<base64>` of
 * the raw 32 bytes) and writes the PRIVATE key as a PKCS#8 PEM.
 *
 * The private key is NEVER printed to stdout -- it only ever reaches a file
 * with 0600 permissions, so it cannot leak into a terminal scrollback, a CI
 * log, or a shell history via a pipe.
 *
 * Usage:
 *   bun tools/keygen.ts [--out path/to/key.pem] [--force]
 *
 * Then: store the PEM contents in the INDEX_SIGNING_KEY CI secret, add the
 * public key to a host key slot, and destroy every other copy of the PEM.
 */
import { generateKeyPairSync } from "node:crypto";
import { existsSync, writeFileSync } from "node:fs";
import { resolve } from "node:path";
import { encodePublicKey } from "./keys.ts";

function die(message: string): never {
  console.error(`error: ${message}`);
  process.exit(1);
}

const args = process.argv.slice(2);
let out = "index-signing-key.pem";
let force = false;
for (let i = 0; i < args.length; i++) {
  const arg = args[i]!;
  if (arg === "--out") {
    const next = args[++i];
    if (!next) die("--out needs a path");
    out = next;
  } else if (arg.startsWith("--out=")) {
    out = arg.slice("--out=".length);
  } else if (arg === "--force") {
    force = true;
  } else {
    die(`unknown argument ${arg}`);
  }
}

const outPath = resolve(out);
if (existsSync(outPath) && !force) {
  die(
    `${outPath} already exists. Refusing to overwrite a private key -- ` +
      "move it aside first, or pass --force if you are certain it is disposable.",
  );
}

const { publicKey, privateKey } = generateKeyPairSync("ed25519");

const pem = privateKey.export({ type: "pkcs8", format: "pem" }) as string;
// mode 0600 on create; also set explicitly in case of a pre-existing file.
writeFileSync(outPath, pem, { mode: 0o600 });

console.log(`private key -> ${outPath} (mode 0600, NOT printed, do not commit)`);
console.log("");
console.log("public key (pin this in the host):");
console.log("");
console.log(`  ${encodePublicKey(publicKey)}`);
console.log("");
console.log("Next steps:");
console.log("  1. Put the PEM contents in the INDEX_SIGNING_KEY repository secret.");
console.log("  2. Add the public key above to a host key slot (the host pins two,");
console.log("     so you can roll to a new key before retiring the old one).");
console.log("  3. Destroy every copy of the PEM outside the secret store.");