Spotify Connection and DH Handshake

index.js

//Spotify Protocol Connection Demo
//N.B. Don't forget to install the dependencies

var crypto = require('crypto');
var fs = require('fs');
var net = require('net');

var protobuf = require('protocol-buffers');

var HOST = 'lon6-accesspoint-a19.ap.spotify.com';
var PORT = 4070;

var client = new net.Socket();

var messages = protobuf(fs.readFileSync('keyexchange.proto'))

var prime = Buffer([
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc9,
        0x0f, 0xda, 0xa2, 0x21, 0x68, 0xc2, 0x34, 0xc4, 0xc6,
        0x62, 0x8b, 0x80, 0xdc, 0x1c, 0xd1, 0x29, 0x02, 0x4e,
        0x08, 0x8a, 0x67, 0xcc, 0x74, 0x02, 0x0b, 0xbe, 0xa6,
        0x3b, 0x13, 0x9b, 0x22, 0x51, 0x4a, 0x08, 0x79, 0x8e,
        0x34, 0x04, 0xdd, 0xef, 0x95, 0x19, 0xb3, 0xcd, 0x3a,
        0x43, 0x1b, 0x30, 0x2b, 0x0a, 0x6d, 0xf2, 0x5f, 0x14,
        0x37, 0x4f, 0xe1, 0x35, 0x6d, 0x6d, 0x51, 0xc2, 0x45,
        0xe4, 0x85, 0xb5, 0x76, 0x62, 0x5e, 0x7e, 0xc6, 0xf4,
        0x4c, 0x42, 0xe9, 0xa6, 0x3a, 0x36, 0x20, 0xff, 0xff,
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff ]);

var dh = crypto.createDiffieHellman(prime);
var dhLocalKeys = dh.generateKeys();

var clientHelloMessage = messages.ClientHello.encode({
  build_info: {
    product: messages.Product.PRODUCT_PARTNER,
    platform: messages.Platform.PLATFORM_OSX_X86_64,
    version: 105600451,
  },
  cryptosuites_supported: [messages.Cryptosuite.CRYPTO_SUITE_SHANNON],
  login_crypto_hello: {
    diffie_hellman: {
      gc: dhLocalKeys,
      server_keys_known: 1
    }
  },
  client_nonce: crypto.randomBytes(16),
});

var bufHeader = new Buffer([0x00, 0x04]);

var bufLength = Buffer.alloc(4);
bufLength.writeUInt32BE('0x' + (2 + 4 + clientHelloMessage.length).toString(16));

var clientHelloBuf = Buffer.concat([bufHeader, bufLength, clientHelloMessage]);

var isInitialPacket = true;

client.connect(PORT, HOST, function() {

    console.log('CONNECTED TO: ' + HOST + ':' + PORT);
  
    client.write(clientHelloBuf);

});

client.on('data', function(data) {
    
    var response = new Buffer(data, "hex");
  
    if (isInitialPacket) {
    
      var sharedSecret = dh.computeSecret(messages.APResponseMessage.decode(response.slice(4, 2 * (response.readUInt32BE(0, 7)))).challenge.login_crypto_challenge.diffie_hellman.gs);

      var shannonKeyBuf = new Buffer(100);

      for (var i = 1; i <= 5; i++) {
        var hmacSha1 = crypto.createHmac('sha1', sharedSecret);
        var buf = Buffer.concat([clientHelloBuf, response]);

        buf.write(i.toString(), buf.length - 1);
        hmacSha1.update(buf);

        shannonKeyBuf.write(hmacSha1.digest('hex'), (i - 1) * 20, 20, 'hex');

        if (shannonKeyBuf[99] !== 00) {
          
          console.log('\nKey String: ' + shannonKeyBuf.toString('hex'));
          console.log('\nChallenge: ' + shannonKeyBuf.slice(0, 20).toString('hex'));
          console.log('\nSend Key: ' + shannonKeyBuf.slice(20, 52).toString('hex'));
          console.log('\nRecieve Key: ' + shannonKeyBuf.slice(52, 82).toString('hex'));

          var clientResponsePlaintext = messages.ClientResponsePlaintext.encode({
            login_crypto_response: {
              diffie_hellman: {
                hmac: shannonKeyBuf.slice(0, 20)
              }
            },
            pow_response: {},
            crypto_response: {}
          });
          
          client.write(clientResponsePlaintext);
        }
        
      }
      
    } else {
      console.log(response.toString('hex'));
    }
    
    client.destroy();
    
});

client.on('close', function() {
    console.log('Connection closed');
});

keyexchange.proto

syntax = "proto2";

message ClientHello {
    required BuildInfo build_info = 0xa; 
    repeated Fingerprint fingerprints_supported = 0x14; 
    repeated Cryptosuite cryptosuites_supported = 0x1e; 
    repeated Powscheme powschemes_supported = 0x28; 
    required LoginCryptoHelloUnion login_crypto_hello = 0x32; 
    required bytes client_nonce = 0x3c; 
    optional bytes padding = 0x46; 
    optional FeatureSet feature_set = 0x50; 
}


message BuildInfo {
    required Product product = 0xa; 
    repeated ProductFlags product_flags = 0x14; 
    required Platform platform = 0x1e; 
    required uint64 version = 0x28; 
}

enum Product {
    PRODUCT_CLIENT = 0x0;
    PRODUCT_LIBSPOTIFY= 0x1;
    PRODUCT_MOBILE = 0x2;
    PRODUCT_PARTNER = 0x3;
    PRODUCT_LIBSPOTIFY_EMBEDDED = 0x5;
}

enum ProductFlags {
    PRODUCT_FLAG_NONE = 0x0;
    PRODUCT_FLAG_DEV_BUILD = 0x1;
}

enum Platform {
    PLATFORM_WIN32_X86 = 0x0;
    PLATFORM_OSX_X86 = 0x1;
    PLATFORM_LINUX_X86 = 0x2;
    PLATFORM_IPHONE_ARM = 0x3;
    PLATFORM_S60_ARM = 0x4;
    PLATFORM_OSX_PPC = 0x5;
    PLATFORM_ANDROID_ARM = 0x6;
    PLATFORM_WINDOWS_CE_ARM = 0x7;
    PLATFORM_LINUX_X86_64 = 0x8;
    PLATFORM_OSX_X86_64 = 0x9;
    PLATFORM_PALM_ARM = 0xa;
    PLATFORM_LINUX_SH = 0xb;
    PLATFORM_FREEBSD_X86 = 0xc;
    PLATFORM_FREEBSD_X86_64 = 0xd;
    PLATFORM_BLACKBERRY_ARM = 0xe;
    PLATFORM_SONOS = 0xf;
    PLATFORM_LINUX_MIPS = 0x10;
    PLATFORM_LINUX_ARM = 0x11;
    PLATFORM_LOGITECH_ARM = 0x12;
    PLATFORM_LINUX_BLACKFIN = 0x13;
    PLATFORM_WP7_ARM = 0x14;
    PLATFORM_ONKYO_ARM = 0x15;
    PLATFORM_QNXNTO_ARM = 0x16;
    PLATFORM_BCO_ARM = 0x17;
}

enum Fingerprint {
    FINGERPRINT_GRAIN = 0x0;
    FINGERPRINT_HMAC_RIPEMD = 0x1;
}

enum Cryptosuite {
    CRYPTO_SUITE_SHANNON = 0x0;
    CRYPTO_SUITE_RC4_SHA1_HMAC = 0x1;
}

enum Powscheme {
    POW_HASH_CASH = 0x0;
}


message LoginCryptoHelloUnion {
    optional LoginCryptoDiffieHellmanHello diffie_hellman = 0xa; 
}


message LoginCryptoDiffieHellmanHello {
    required bytes gc = 0xa; 
    required uint32 server_keys_known = 0x14; 
}


message FeatureSet {
    optional bool autoupdate2 = 0x1; 
    optional bool current_location = 0x2; 
}


message APResponseMessage {
    optional APChallenge challenge = 0xa; 
    optional UpgradeRequiredMessage upgrade = 0x14; 
    optional APLoginFailed login_failed = 0x1e; 
}

message APChallenge {
    required LoginCryptoChallengeUnion login_crypto_challenge = 0xa; 
    required FingerprintChallengeUnion fingerprint_challenge = 0x14; 
    required PoWChallengeUnion pow_challenge = 0x1e; 
    required CryptoChallengeUnion crypto_challenge = 0x28; 
    required bytes server_nonce = 0x32; 
    optional bytes padding = 0x3c; 
}

message LoginCryptoChallengeUnion {
    optional LoginCryptoDiffieHellmanChallenge diffie_hellman = 0xa; 
}

message LoginCryptoDiffieHellmanChallenge {
    required bytes gs = 0xa; 
    required int32 server_signature_key = 0x14; 
    required bytes gs_signature = 0x1e; 
}

message FingerprintChallengeUnion {
    optional FingerprintGrainChallenge grain = 0xa; 
    optional FingerprintHmacRipemdChallenge hmac_ripemd = 0x14; 
}


message FingerprintGrainChallenge {
    required bytes kek = 0xa; 
}


message FingerprintHmacRipemdChallenge {
    required bytes challenge = 0xa; 
}


message PoWChallengeUnion {
    optional PoWHashCashChallenge hash_cash = 0xa; 
}

message PoWHashCashChallenge {
    optional bytes prefix = 0xa; 
    optional int32 length = 0x14; 
    optional int32 target = 0x1e; 
}


message CryptoChallengeUnion {
    optional CryptoShannonChallenge shannon = 0xa; 
    optional CryptoRc4Sha1HmacChallenge rc4_sha1_hmac = 0x14; 
}


message CryptoShannonChallenge {
}


message CryptoRc4Sha1HmacChallenge {
}


message UpgradeRequiredMessage {
    required bytes upgrade_signed_part = 0xa; 
    required bytes signature = 0x14; 
    optional string http_suffix = 0x1e; 
}

message APLoginFailed {
    required ErrorCode error_code = 0xa; 
    optional int32 retry_delay = 0x14; 
    optional int32 expiry = 0x1e; 
    optional string error_description = 0x28; 
}

enum ErrorCode {
    ProtocolError = 0x0;
    TryAnotherAP = 0x2;
    BadConnectionId = 0x5;
    TravelRestriction = 0x9;
    PremiumAccountRequired = 0xb;
    BadCredentials = 0xc;
    CouldNotValidateCredentials = 0xd;
    AccountExists = 0xe;
    ExtraVerificationRequired = 0xf;
    InvalidAppKey = 0x10;
    ApplicationBanned = 0x11;
}

message ClientResponsePlaintext {
    required LoginCryptoResponseUnion login_crypto_response = 0xa; 
    required PoWResponseUnion pow_response = 0x14; 
    required CryptoResponseUnion crypto_response = 0x1e; 
}


message LoginCryptoResponseUnion {
    optional LoginCryptoDiffieHellmanResponse diffie_hellman = 0xa; 
}


message LoginCryptoDiffieHellmanResponse {
    required bytes hmac = 0xa; 
}


message PoWResponseUnion {
    optional PoWHashCashResponse hash_cash = 0xa; 
}


message PoWHashCashResponse {
    required bytes hash_suffix = 0xa; 
}


message CryptoResponseUnion {
    optional CryptoShannonResponse shannon = 0xa; 
    optional CryptoRc4Sha1HmacResponse rc4_sha1_hmac = 0x14; 
}


message CryptoShannonResponse {
    optional int32 dummy = 0x1; 
}


message CryptoRc4Sha1HmacResponse {
    optional int32 dummy = 0x1; 
}