generate-crx-id.js

async function generateKeysAndId() {
  const keyPair = await crypto.subtle.generateKey(
    {
      name: "RSASSA-PKCS1-v1_5",
      modulusLength: 2048,
      publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
      hash: "SHA-256",
    },
    true,
    ["sign", "verify"]
  );

  const [pubBuf, privBuf] = await Promise.all([
    crypto.subtle.exportKey("spki", keyPair.publicKey),
    crypto.subtle.exportKey("pkcs8", keyPair.privateKey),
  ]);

  const hash = new Uint8Array(await crypto.subtle.digest("SHA-256", pubBuf));
  const id = [...hash.slice(0, 16)]
    .flatMap((b) => [b >> 4, b & 0x0f])
    .map((n) => String.fromCharCode(97 + n))
    .join("");

  const toPem = (buf, type) => {
    const b64 = btoa(String.fromCharCode(...new Uint8Array(buf)));
    const lines = b64.match(/.{1,64}/g).join("\n");
    return `-----BEGIN ${type}-----\n${lines}\n-----END ${type}-----`;
  };
  const privKey = toPem(privBuf, "PRIVATE KEY");
  const pubKey = btoa(String.fromCharCode(...new Uint8Array(pubBuf)));

  return { id, privKey, pubKey };
}