1 files changed, 160 insertions, 0 deletions
diff --git a/helper.js b/helper.js
new file mode 100644
index 0000000..b4d37a6
--- /dev/null
+++ b/helper.js
@@ -0,0 +1,160 @@
+'use strict';
+
+var forge = require('node-forge');
+var rsa = forge.pki.rsa;
+
+var fs = require('fs');
+var crypto = require('crypto');
+var debug = require('debug')('nodetunes:helper');
+
+var parseSdp = function(msg) {
+  var multi = ['a', 'p', 'b'];
+
+  var lines = msg.split('\r\n');
+  var output = {};
+  for (var i = 0; i < lines.length; i++) {
+
+    var sp = lines[i].split(/=(.+)?/);
+    if (sp.length == 3) { // for some reason there's an empty item?
+      if (multi.indexOf(sp[0]) != -1) { // some attributes are multiline...
+        if (!output[sp[0]])
+          output[sp[0]] = [];
+
+        output[sp[0]].push(sp[1]);
+      } else {
+        output[sp[0]] = sp[1];
+      }
+    }
+  }
+
+  return output;
+};
+
+var dmapTypes = {
+  mper: 8,
+  asal: 'str',
+  asar: 'str',
+  ascp: 'str',
+  asgn: 'str',
+  minm: 'str',
+  astn: 2,
+  asdk: 1,
+  caps: 1,
+  astm: 4,
+};
+
+var parseDmap = function(buffer) {
+  var output = {};
+
+  for (var i = 8; i < buffer.length;) {
+    var itemType = buffer.slice(i, i + 4);
+    var itemLength = buffer.slice(i + 4, i + 8).readUInt32BE(0);
+    if (itemLength !== 0) {
+      var data = buffer.slice(i + 8, i + 8 + itemLength);
+      if (dmapTypes[itemType] == 'str') {
+        output[itemType.toString()] = data.toString();
+      } else if (dmapTypes[itemType] == 1) {
+        output[itemType.toString()] = data.readUInt8(0);
+      } else if (dmapTypes[itemType] == 2) {
+        output[itemType.toString()] = data.readUInt16BE(0);
+      } else if (dmapTypes[itemType] == 4) {
+        output[itemType.toString()] = data.readUInt32BE(0);
+      } else if (dmapTypes[itemType] == 8) {
+        output[itemType.toString()] = (data.readUInt32BE(0) << 8) + data.readUInt32BE(4);
+      }
+    }
+
+    i += 8 + itemLength;
+  }
+
+  return output;
+};
+
+var getPrivateKey = function() {
+
+  var keyFile = fs.readFileSync(__dirname + '/../private.key');
+  var privkey = forge.pki.privateKeyFromPem(keyFile);
+
+  return privkey;
+};
+
+var privateKey = getPrivateKey();
+
+var generateAppleResponse = function(challengeBuf, ipAddr, macAddr) {
+  debug = require('debug')('nodetunes:helper'); // HACK: need to reload debug here (https://github.com/visionmedia/debug/issues/150)
+  debug('building challenge for %s (ip: %s, mac: %s)', challengeBuf.toString('base64'), ipAddr.toString('hex'), macAddr.toString('hex'));
+
+  var fullChallenge = Buffer.concat([challengeBuf, ipAddr, macAddr]);
+
+  // im sure there's an easier way to pad this buffer
+  var padding = [];
+  for (var i = fullChallenge.length; i < 32; i++) {
+    padding.push(0);
+  }
+
+  fullChallenge = Buffer.concat([fullChallenge, new Buffer(padding)]).toString('binary');
+  var response = forge.pki.rsa.encrypt(fullChallenge, privateKey, 0x01);
+  debug('computed challenge: %s', forge.util.encode64(response));
+
+  return forge.util.encode64(response);
+};
+
+var generateRfc2617Response = function(username, realm, password, nonce, uri, method) {
+
+  var md5 = function(content) {
+    return crypto.createHash('md5').update(content).digest().toString('hex');
+  };
+
+  var ha1 = md5(username + ':' + realm + ':' + password);
+  var ha2 = md5(method + ':' + uri);
+  var response = md5(ha1 + ':' + nonce + ':' + ha2);
+
+  return response;
+};
+
+var getDecoderOptions = function(audioOptions) {
+  if (!audioOptions) return {}
+  var decoderOptions = {
+      frameLength: parseInt(audioOptions[1], 10),
+      compatibleVersion: parseInt(audioOptions[2], 10),
+      bitDepth: parseInt(audioOptions[3], 10),
+      pb: parseInt(audioOptions[4], 10),
+      mb: parseInt(audioOptions[5], 10),
+      kb: parseInt(audioOptions[6], 10),
+      channels: parseInt(audioOptions[7], 10),
+      maxRun: parseInt(audioOptions[8], 10),
+      maxFrameBytes: parseInt(audioOptions[9], 10),
+      avgBitRate: parseInt(audioOptions[10], 10),
+      sampleRate: parseInt(audioOptions[11], 10)
+    };
+
+  return decoderOptions;
+};
+
+var decryptAudioData = function(data, audioAesKey, audioAesIv, headerSize) {
+  var tmp = new Buffer(16);
+  if (!headerSize) headerSize = 12;
+
+  var remainder = (data.length - 12) % 16;
+  var endOfEncodedData = data.length - remainder;
+
+  var audioAesKeyBuffer = new Buffer(audioAesKey, 'binary');
+  var decipher = crypto.createDecipheriv('aes-128-cbc', audioAesKeyBuffer, audioAesIv);
+  decipher.setAutoPadding(false);
+
+  for (var i = headerSize, l = endOfEncodedData - 16; i <= l; i += 16) {
+    data.copy(tmp, 0, i, i + 16);
+    decipher.update(tmp).copy(data, i, 0, 16);
+  }
+
+  return data.slice(headerSize);
+};
+
+module.exports.decryptAudioData = decryptAudioData;
+module.exports.getDecoderOptions = getDecoderOptions;
+module.exports.parseSdp = parseSdp;
+module.exports.parseDmap = parseDmap;
+module.exports.generateAppleResponse = generateAppleResponse;
+module.exports.generateRfc2617Response = generateRfc2617Response;
+module.exports.rsaPrivateKey = privateKey;
+