export async function hkdfExpand()

in src/crypto.js [82:102]

• 20 lines of code
• 4 McCabe index (conditional complexity)

export async function hkdfExpand(prk, info, length) {
  // Ref https://tools.ietf.org/html/rfc5869#section-2.3
  const N = Math.ceil(length / HASH_LENGTH);
  if (N <= 0) {
    throw new TLSError(ALERT_DESCRIPTION.INTERNAL_ERROR);
  }
  if (N >= 255) {
    throw new TLSError(ALERT_DESCRIPTION.INTERNAL_ERROR);
  }
  const input = new BufferWriter();
  const output = new BufferWriter();
  let T = new Uint8Array(0);
  for (let i = 1; i <= N; i++) {
    input.writeBytes(T);
    input.writeBytes(info);
    input.writeUint8(i);
    T = await hmac(prk, input.flush());
    output.writeBytes(T);
  }
  return output.slice(0, length);
}