index.js

const crypto = require("crypto");

const md5 = (data, type = "ascii") => {
  const md5sum = crypto.createHash("md5");
  md5sum.update(data, type);
  return md5sum.digest("hex");
};

const getBlowfishKey = (trackId) => {
  let SECRET = "g4el58wc" + "0zvf9na1";
  let idMd5 = md5(trackId);
  let bfKey = "";
  for (let i = 0; i < 16; i++) {
    bfKey += String.fromCharCode(
      idMd5.charCodeAt(i) ^ idMd5.charCodeAt(i + 16) ^ SECRET.charCodeAt(i)
    );
  }
  return bfKey;
};

const decryptChunk = (chunk, blowFishKey) => {
  let cipher = crypto.createDecipheriv(
    "bf-cbc",
    blowFishKey,
    Buffer.from([0, 1, 2, 3, 4, 5, 6, 7])
  );
  cipher.setAutoPadding(false);
  return cipher.update(chunk, "binary", "binary") + cipher.final();
};

const getSongFileName = (track, quality) => {
  const { MD5_ORIGIN, SNG_ID, MEDIA_VERSION } = track;
  const step1 = [MD5_ORIGIN, quality, SNG_ID, MEDIA_VERSION].join("¤");

  let step2 = md5(step1) + "¤" + step1 + "¤";
  while (step2.length % 16 > 0) step2 += " ";

  return crypto
    .createCipheriv("aes-128-ecb", "jo6aey6haid2Teih", "")
    .update(step2, "ascii", "hex");
};

/**
 *
 * @param source Downloaded song from `getTrackDownloadUrl`
 * @param trackId Song ID as string
 */
const decryptDownload = (source, trackId) => {
  // let part_size = 0x1800;
  let chunk_size = 2048;
  let blowFishKey = getBlowfishKey(trackId);
  let i = 0;
  let position = 0;

  let destBuffer = Buffer.alloc(source.length);
  destBuffer.fill(0);

  while (position < source.length) {
    let chunk;
    if (source.length - position >= 2048) chunk_size = 2048;
    else chunk_size = source.length - position;
    chunk = Buffer.alloc(chunk_size);

    let chunkString;
    chunk.fill(0);
    source.copy(chunk, 0, position, position + chunk_size);
    if (i % 3 > 0 || chunk_size < 2048) chunkString = chunk.toString("binary");
    else chunkString = decryptChunk(chunk, blowFishKey);

    destBuffer.write(chunkString, position, chunkString.length, "binary");
    position += chunk_size;
    i++;
  }

  return destBuffer;
};

/**
 * @param track Track info json returned from `getTrackInfo`
 * @param quality 1 = 128kbps, 3 = 320kbps and 9 = flac (around 1411kbps)
 */
const getTrackDownloadUrl = (track, quality) => {
  const cdn = track.MD5_ORIGIN[0]; // cdn destination
  const filename = getSongFileName(track, quality); // encrypted file name
  return `http://e-cdn-proxy-${cdn}.deezer.com/mobile/1/${filename}`;
};

module.exports = { getSongFileName, decryptDownload, getTrackDownloadUrl };