解密苹果商务聊天身份验证令牌

Question

我正在查看此集成文档：

https://register.apple.com/resources/business-chat/BC_Sending_an_Auth_Msg.pdf

请参阅"如何解密身份验证令牌"部分

我正在使用充气城堡v1.8.3进行c#

我有一个测试控制台应用：

namespace AppleBusinessChat45
{
class Program
{
static void Main(string[] args)
{
var publicKey = "BNY+I93aHVkXnNWKVLdrMJLXpQ1BsyHYoiv6UNi4rDUsRx3sNNhW8FNy9yUwxYprAwwfj1ZkoJ61Fs+SwjIbGPtXi52arvSbPglyBN4uAxtP3VP3LCP4JtSEjdgsgsretA==";
var privateKey = "pX/BvdXXUdpC79mW/jWi10Z6PJb5SBY2+aqkR/qYOjqgakKsqZFKnl0kz10Ve+BP";
var token = "BDiRKNnPiPUb5oala31nkmCaXMB0iyWy3Q93p6fN7vPxEQSUlFVsInkJzPBBqmW1FUIY1KBA3BQb3W3Qv4akZ8kblqbmvupE/EJzPKbROZFBNvxpvVOHHgO2qadmHAjHSmnxUuxrpKxopWnOgyhzUx+mBUTao0pcEgqZFw0Y/qZIJPf1KusCMlz5TAhpjsw=";
var decodedToken = Base64.Decode(token);
var decodedEphemeralPublicKey = decodedToken.Take(97).ToArray();
var encodedEphemeralPublicKeyCheck = Encoding.ASCII.GetString(Base64.Encode(decodedEphemeralPublicKey));
if (encodedEphemeralPublicKeyCheck != "BDiRKNnPiPUb5oala31nkmCaXMB0iyWy3Q93p6fN7vPxEQSUlFVsInkJzPBBqmW1FUIY1KBA3BQb3W3Qv4akZ8kblqbmvupE/EJzPKbROZFBNvxpvVOHHgO2qadmHAjHSg==")
throw new Exception("Public key check failed");
X9ECParameters curveParams = ECNamedCurveTable.GetByName("secp384r1");
ECPoint decodePoint = curveParams.Curve.DecodePoint(decodedEphemeralPublicKey);
ECDomainParameters domainParams = new ECDomainParameters(curveParams.Curve, curveParams.G, curveParams.N, curveParams.H, curveParams.GetSeed());
ECPublicKeyParameters ecPublicKeyParameters = new ECPublicKeyParameters(decodePoint, domainParams);
var x = ecPublicKeyParameters.Q.AffineXCoord.ToBigInteger();
var y = ecPublicKeyParameters.Q.AffineYCoord.ToBigInteger();
if (!x.Equals(new BigInteger("8706462696031173094919866327685737145866436939551712382591956952075131891462487598200779332295613073905587629438229")))
throw new Exception("X coord check failed");
if (!y.Equals(new BigInteger("10173258529327482491525749925661342501140613951412040971418641469645769857676705559747557238888921287857458976966474")))
throw new Exception("Y coord check failed");
var privateKeyBytes = Strings.ToByteArray(privateKey);
ECPrivateKeyParameters ecPrivateKeyParameters = new ECPrivateKeyParameters(new BigInteger(privateKeyBytes), domainParams);
IBasicAgreement agree = AgreementUtilities.GetBasicAgreement("ECDHC");
agree.Init(ecPrivateKeyParameters);
BigInteger sharedKey = agree.CalculateAgreement(ecPublicKeyParameters);
var sharedKeyBytes = sharedKey.ToByteArrayUnsigned();
// Expecting:
// 2lvSJsBO2keUHRfvPG6C1RMUmGpuDbdgNrZ9YD7RYnvAcfgq/fjeYr1p0hWABeif
Console.WriteLine("Done");
Console.ReadLine();
}
}
}

文档指出">示例私钥表示为转换为字节的无符号标量">，其值为：

pX/BvdXXUdpC79mW/jWi10Z6PJb5SBY2+aqkR/qYOjqgakKsqZFKnl0kz10Ve+BP

我可能读错了私钥？由于我尝试并解决的密钥与文档中的预期值不匹配。

网上几乎没有实施细节。

就充气城堡而言，如何从字符串中读取私钥，然后用于生成共享密钥？

更新

对于那些正在寻找解密 apple 聊天身份验证令牌的完整示例实现的人，请参阅下文：

namespace AppleBusinessChat45
{
class Program
{
static void Main(string[] args)
{
var privateKey = "pX/BvdXXUdpC79mW/jWi10Z6PJb5SBY2+aqkR/qYOjqgakKsqZFKnl0kz10Ve+BP";
var token = "BDiRKNnPiPUb5oala31nkmCaXMB0iyWy3Q93p6fN7vPxEQSUlFVsInkJzPBBqmW1FUIY1KBA3BQb3W3Qv4akZ8kblqbmvupE/EJzPKbROZFBNvxpvVOHHgO2qadmHAjHSmnxUuxrpKxopWnOgyhzUx+mBUTao0pcEgqZFw0Y/qZIJPf1KusCMlz5TAhpjsw=";
// #####
// ##### Step 1
// #####
var decodedToken = Convert.FromBase64String(token);
var decodedEphemeralPublicKey = decodedToken.Take(97).ToArray();
var encodedEphemeralPublicKeyCheck = Convert.ToBase64String(decodedEphemeralPublicKey);
if (encodedEphemeralPublicKeyCheck != "BDiRKNnPiPUb5oala31nkmCaXMB0iyWy3Q93p6fN7vPxEQSUlFVsInkJzPBBqmW1FUIY1KBA3BQb3W3Qv4akZ8kblqbmvupE/EJzPKbROZFBNvxpvVOHHgO2qadmHAjHSg==")
throw new Exception("Public key check failed");
X9ECParameters curveParams = ECNamedCurveTable.GetByName("secp384r1");
ECPoint decodePoint = curveParams.Curve.DecodePoint(decodedEphemeralPublicKey);
ECDomainParameters domainParams = new ECDomainParameters(curveParams.Curve, curveParams.G, curveParams.N, curveParams.H, curveParams.GetSeed());
ECPublicKeyParameters ecPublicKeyParameters = new ECPublicKeyParameters(decodePoint, domainParams);
var x = ecPublicKeyParameters.Q.AffineXCoord.ToBigInteger();
var y = ecPublicKeyParameters.Q.AffineYCoord.ToBigInteger();
if (!x.Equals(new BigInteger("8706462696031173094919866327685737145866436939551712382591956952075131891462487598200779332295613073905587629438229")))
throw new Exception("X coord check failed");
if (!y.Equals(new BigInteger("10173258529327482491525749925661342501140613951412040971418641469645769857676705559747557238888921287857458976966474")))
throw new Exception("Y coord check failed");
Console.WriteLine("Step 1 complete");
// #####
// ##### Step 2
// #####
var privateKeyBytes = Convert.FromBase64String(privateKey);
var ecPrivateKeyParameters = new ECPrivateKeyParameters("ECDHC", new BigInteger(1, privateKeyBytes), domainParams);
var privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(ecPrivateKeyParameters);
var ecPrivateKey = (ECPrivateKeyParameters) PrivateKeyFactory.CreateKey(privateKeyInfo);
IBasicAgreement agree = AgreementUtilities.GetBasicAgreement("ECDHC");
agree.Init(ecPrivateKey);
BigInteger sharedKey = agree.CalculateAgreement(ecPublicKeyParameters);
var sharedKeyBytes = sharedKey.ToByteArrayUnsigned();
var sharedKeyBase64 = Convert.ToBase64String(sharedKeyBytes);
if (sharedKeyBase64 != "2lvSJsBO2keUHRfvPG6C1RMUmGpuDbdgNrZ9YD7RYnvAcfgq/fjeYr1p0hWABeif")
throw new Exception("Shared key check failed");
Console.WriteLine("Step 2 complete");
// #####
// ##### Step 3
// #####
var kdf2Bytes = Kdf2(sharedKeyBytes, decodedEphemeralPublicKey);
var kdf2Base64 = Convert.ToBase64String(kdf2Bytes);
if (kdf2Base64 != "mAzkYatDlz4SzrCyM23NhgL/+mE3eGgfUz9h1CFPhZOtXequzN3Q8w+B5GE2eU5g")
throw new Exception("Kdf2 failed");
Console.WriteLine("Step 3 complete");
// #####
// ##### Step 4
// #####
var decryptionKeyBytes = kdf2Bytes.Take(32).ToArray();
var decryptionIvBytes = kdf2Bytes.Skip(32).ToArray();
var decryptionKeyBase64 = Convert.ToBase64String(decryptionKeyBytes);
var decryptionIvBase64 = Convert.ToBase64String(decryptionIvBytes);
if (decryptionKeyBase64 != "mAzkYatDlz4SzrCyM23NhgL/+mE3eGgfUz9h1CFPhZM=")
throw new Exception("Decryption key check failed");
if (decryptionIvBase64 != "rV3qrszd0PMPgeRhNnlOYA==")
throw new Exception("Decryption iv check failed");
var encryptedDataBytes = decodedToken.Skip(97).Take(decodedToken.Length - 113).ToArray();
var tagBytes = decodedToken.Skip(decodedToken.Length - 16).ToArray();
var encryptedDataBase64 = Convert.ToBase64String(encryptedDataBytes);
var tagBase64 = Convert.ToBase64String(tagBytes);
if (encryptedDataBase64 != "afFS7GukrGilac6DKHNTH6YFRNqjSlwSCpkXDRj+")
throw new Exception("Encrypted data check failed");
if (tagBase64 != "pkgk9/Uq6wIyXPlMCGmOzA==")
throw new Exception("Tag check failed");
KeyParameter keyParam = ParameterUtilities.CreateKeyParameter("AES", decryptionKeyBytes);
ParametersWithIV parameters = new ParametersWithIV(keyParam, decryptionIvBytes);
IBufferedCipher cipher = CipherUtilities.GetCipher("AES/GCM/NoPadding");
cipher.Init(false, parameters);
var resultBytes = cipher.DoFinal(encryptedDataBytes.Concat(tagBytes).ToArray());
var resultBase64 = Convert.ToBase64String(resultBytes);
var resultString = Strings.FromByteArray(resultBytes);
if (resultString != "xXTi32iZwrQ6O8Sy6r1isKwF6Ff1Py")
throw new Exception("Decryption failed");
Console.WriteLine("Step 4 complete");
Console.WriteLine(resultString);
Console.WriteLine();
Console.WriteLine("Done... press any key to finish");
Console.ReadLine();
}
static byte[] Kdf2(byte[] sharedKeyBytes, byte[] ephemeralKeyBytes)
{
var gen = new Kdf2BytesGenerator(new Sha256Digest());
gen.Init(new KdfParameters(sharedKeyBytes, ephemeralKeyBytes));
byte[] encryptionKeyBytes = new byte[48];
gen.GenerateBytes(encryptionKeyBytes, 0, encryptionKeyBytes.Length);
return encryptionKeyBytes;
}
}
}

Answer 1

替换这个：

var privateKeyBytes = Strings.ToByteArray(privateKey);
ECPrivateKeyParameters ecPrivateKeyParameters = new ECPrivateKeyParameters(new BigInteger(privateKeyBytes), domainParams);
IBasicAgreement agree = AgreementUtilities.GetBasicAgreement("ECDHC");
agree.Init(ecPrivateKeyParameters);

有了这个：

var privateKeyBytes = Convert.FromBase64String(privateKey);
var ecPrivateKeyParameters = new ECPrivateKeyParameters("ECDHC", new BigInteger(1, privateKeyBytes), domainParams);
var privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(ecPrivateKeyParameters);
var ecPrivateKey = (ECPrivateKeyParameters)PrivateKeyFactory.CreateKey(privateKeyInfo);
var agree = AgreementUtilities.GetBasicAgreement("ECDHC");
agree.Init(ecPrivateKey);

它应该有效。