index.ts

/**
 * Consume the value of the `Authorization` HTTP header field, succeeding when the
 * value adheres to the "Basic" authentication scheme described by IETF RFC 2617.
 *
 * For example,
 *
 *     writeBasicAuth({ username: "Aladdin", password: "open sesame" })
 *
 * produces
 *
 *     "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ=="
 */
export function readBasicAuth(authorization: string):
  | {
    success: true;
    username: string;
    password: string;
  }
  | { success: false } {
  if (!authorization.startsWith(prefix)) return { success: false };
  const encodedCredentials = authorization.slice(prefix.length)
  const decodedCredentials = Buffer.from(encodedCredentials, "base64").toString(
    "utf8",
  );
  const i = decodedCredentials.indexOf(':')
  if (i === -1) return { success: false };
  const username = decodedCredentials.slice(0, i)
  const password = decodedCredentials.slice(i + 1)
  return { success: true, username, password };
}

/**
 * Produce a string suitable for use as the value of the `Authorization` HTTP header
 * field according to the "Basic" authentication scheme described by IETF RFC 2617.
 */
export function writeBasicAuth(x: {
  username: string;
  password: string;
}): string {
  return `${prefix}${Buffer.from(`${x.username}:${x.password}`).toString("base64")}`;
}

const prefix = "Basic "