Develop Reference

iOS Device Check - Server Side C# .net solution (JWT)

Setting up DeviceCheck on iOS is super easy, but implementing the server-side using C# is difficult as there are hardly any examples and some tricky JWT code is needed, which has to be absolutely perfect for it to work. Does anyone have a solution?

Here is a complete solution. I stripped out the first and last line from the p8 file e.g. "key begins here" (or whatever) and also took out all the new lines so that the key was just one long line
static void Main(string[] args)
{
string deviceToken = ""; //you get this from the device
string transcationId = Guid.NewGuid().ToString();
var payload = new Dictionary<string, object>() {
{ "device_token", deviceToken },
{ "timestamp", DateTimeOffset.UtcNow.ToUnixTimeSeconds() * 1000 },
{ "transaction_id", transcationId }
};
var token = GetProviderToken();
var payloadJson = JsonConvert.SerializeObject(payload);
using (var httpClient = new HttpClient())
{
using (var request = new HttpRequestMessage(new HttpMethod("POST"), "https://api.development.devicecheck.apple.com/v1/query_two_bits"))
{
request.Headers.TryAddWithoutValidation("Authorization", $"Bearer {token}");
request.Content = new StringContent(payloadJson);
request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/x-www-form-urlencoded");
var response = httpClient.SendAsync(request).Result;
Console.WriteLine(response);
Console.WriteLine(response.Content.ReadAsStringAsync().Result);
}
}
}
private static CngKey GetPrivateKey()
{
using (var reader = File.OpenText(#".\applekey.p8.txt"))
{
var ecPrivateKeyParameters = (ECPrivateKeyParameters)new PemReader(reader).ReadObject();
var x = ecPrivateKeyParameters.Parameters.G.AffineXCoord.GetEncoded();
var y = ecPrivateKeyParameters.Parameters.G.AffineYCoord.GetEncoded();
var d = ecPrivateKeyParameters.D.ToByteArrayUnsigned();
return EccKey.New(x, y, d);
}
}
private static string GetProviderToken()
{
var epochNow = (int)DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1)).TotalSeconds;
var payload = new Dictionary<string, object>()
{
{"iss", "<10 DIGIT TEAM CODE FROM APPLE DEV CENTER>"},
{"iat", epochNow}
};
var extraHeaders = new Dictionary<string, object>()
{
{"kid", "<THE NAME OF THE P8 FILE, 10 DIGITS>"}
};
var privateKey = GetPrivateKey();
return JWT.Encode(payload, privateKey, JwsAlgorithm.ES256, extraHeaders);
}

How to generate JWT Bearer Flow OAuth access tokens from a .net core client?

I'm having trouble getting my .NET Core client to generate OAuth access tokens for a salesforce endpoint that requires OAuth of type 'JWT Bearer Flow'.
It seems there are limited .NET Framework examples that show a .NET client doing this, however none that show a .NET Core client doing it
e.g.
https://salesforce.stackexchange.com/questions/53662/oauth-jwt-token-bearer-flow-returns-invalid-client-credentials
So in my .NET Core 3.1 app i've generated a self signed certificate, added the private key to the above example's code when loading in the certificate, however a System.InvalidCastExceptionexception exception occurs on this line:
var rsa = certificate.GetRSAPrivateKey() as RSACryptoServiceProvider;
Exception:
System.InvalidCastException: 'Unable to cast object of type 'System.Security.Cryptography.RSACng' to type 'System.Security.Cryptography.RSACryptoServiceProvider'.'
It appears that this private key is used in the JWT Bearer Flow as part of the signature, and perhaps RSACryptoServiceProvider is not used in .NET core as it was in .NET Framework.
My question is this - is there actually a way in .NET Core to generate access tokens for the OAuth JWT Bearer Flow?
Full code that I'm using:
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
var token = GetAccessToken();
}
static dynamic GetAccessToken()
{
// get the certificate
var certificate = new X509Certificate2(#"C:\temp\cert.pfx");
// create a header
var header = new { alg = "RS256" };
// create a claimset
var expiryDate = GetExpiryDate();
var claimset = new
{
iss = "xxxxxx",
prn = "xxxxxx",
aud = "https://test.salesforce.com",
exp = expiryDate
};
// encoded header
var headerSerialized = JsonConvert.SerializeObject(header);
var headerBytes = Encoding.UTF8.GetBytes(headerSerialized);
var headerEncoded = ToBase64UrlString(headerBytes);
// encoded claimset
var claimsetSerialized = JsonConvert.SerializeObject(claimset);
var claimsetBytes = Encoding.UTF8.GetBytes(claimsetSerialized);
var claimsetEncoded = ToBase64UrlString(claimsetBytes);
// input
var input = headerEncoded + "." + claimsetEncoded;
var inputBytes = Encoding.UTF8.GetBytes(input);
// signature
var rsa = (RSACryptoServiceProvider) certificate.GetRSAPrivateKey();
var cspParam = new CspParameters
{
KeyContainerName = rsa.CspKeyContainerInfo.KeyContainerName,
KeyNumber = rsa.CspKeyContainerInfo.KeyNumber == KeyNumber.Exchange ? 1 : 2
};
var aescsp = new RSACryptoServiceProvider(cspParam) { PersistKeyInCsp = false };
var signatureBytes = aescsp.SignData(inputBytes, "SHA256");
var signatureEncoded = ToBase64UrlString(signatureBytes);
// jwt
var jwt = headerEncoded + "." + claimsetEncoded + "." + signatureEncoded;
var client = new WebClient();
client.Encoding = Encoding.UTF8;
var uri = "https://login.salesforce.com/services/oauth2/token";
var content = new NameValueCollection();
content["assertion"] = jwt;
content["grant_type"] = "urn:ietf:params:oauth:grant-type:jwt-bearer";
string response = Encoding.UTF8.GetString(client.UploadValues(uri, "POST", content));
var result = JsonConvert.DeserializeObject<dynamic>(response);
return result;
}
static int GetExpiryDate()
{
var utc0 = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
var currentUtcTime = DateTime.UtcNow;
var exp = (int)currentUtcTime.AddMinutes(4).Subtract(utc0).TotalSeconds;
return exp;
}
static string ToBase64UrlString(byte[] input)
{
return Convert.ToBase64String(input).TrimEnd('=').Replace('+', '-').Replace('/', '_');
}

Well - it turns out posting to stackoverflow gets the brain cogs turning.
The answer ended up being doing a deep dive to find a similar issue here and using the solution from x509certificate2 sign for jwt in .net core 2.1
I ended up replacing the following code:
var cspParam = new CspParameters
{
KeyContainerName = rsa.CspKeyContainerInfo.KeyContainerName,
KeyNumber = rsa.CspKeyContainerInfo.KeyNumber == KeyNumber.Exchange ? 1 : 2
};
var aescsp = new RSACryptoServiceProvider(cspParam) { PersistKeyInCsp = false };
var signatureBytes = aescsp.SignData(inputBytes, "SHA256");
var signatureEncoded = ToBase64UrlString(signatureBytes);
With this code which makes use of the System.IdentityModel.Tokens.Jwt nuget package:
var signingCredentials = new X509SigningCredentials(certificate, "RS256");
var signature = JwtTokenUtilities.CreateEncodedSignature(input, signingCredentials);
Full code after solution:
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
var token = GetAccessToken();
}
static dynamic GetAccessToken()
{
// get the certificate
var certificate = new X509Certificate2(#"C:\temp\cert.pfx");
// create a header
var header = new { alg = "RS256" };
// create a claimset
var expiryDate = GetExpiryDate();
var claimset = new
{
iss = "xxxxx",
prn = "xxxxx",
aud = "https://test.salesforce.com",
exp = expiryDate
};
// encoded header
var headerSerialized = JsonConvert.SerializeObject(header);
var headerBytes = Encoding.UTF8.GetBytes(headerSerialized);
var headerEncoded = ToBase64UrlString(headerBytes);
// encoded claimset
var claimsetSerialized = JsonConvert.SerializeObject(claimset);
var claimsetBytes = Encoding.UTF8.GetBytes(claimsetSerialized);
var claimsetEncoded = ToBase64UrlString(claimsetBytes);
// input
var input = headerEncoded + "." + claimsetEncoded;
var inputBytes = Encoding.UTF8.GetBytes(input);
var signingCredentials = new X509SigningCredentials(certificate, "RS256");
var signature = JwtTokenUtilities.CreateEncodedSignature(input, signingCredentials);
// jwt
var jwt = headerEncoded + "." + claimsetEncoded + "." + signature;
var client = new WebClient();
client.Encoding = Encoding.UTF8;
var uri = "https://test.salesforce.com/services/oauth2/token";
var content = new NameValueCollection();
content["assertion"] = jwt;
content["grant_type"] = "urn:ietf:params:oauth:grant-type:jwt-bearer";
string response = Encoding.UTF8.GetString(client.UploadValues(uri, "POST", content));
var result = JsonConvert.DeserializeObject<dynamic>(response);
return result;
}
static int GetExpiryDate()
{
var utc0 = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
var currentUtcTime = DateTime.UtcNow;
var exp = (int)currentUtcTime.AddMinutes(4).Subtract(utc0).TotalSeconds;
return exp;
}
static string ToBase64UrlString(byte[] input)
{
return Convert.ToBase64String(input).TrimEnd('=').Replace('+', '-').Replace('/', '_');
}

I am replying to this question just because such a similar answer would have helped me a lot when I landed on this page the first time.
First of all you don't have to generate the JWT from the C# client.
To generate a JWT token you can use this website: https://jwt.io/
There is a very well done video showing how to generate a JWT token:
https://www.youtube.com/watch?v=cViU2-xVscA&t=1680s
Once generated, use it from your C# client to call the get access_token endpoint
https://developer.salesforce.com/docs/atlas.en-us.api_iot.meta/api_iot/qs_auth_access_token.htm
(Watch the video on YT)
If all is correct you will get the access_token
To run the API calls, all you need is the access_token and not the JWT.
Once you have it add it to the HTTP calls like this
public static void AddBearerToken(this HttpRequestMessage request, string accessToken)
{
request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", accessToken);
}
From time to time the access_token will expire. To check its validity you can call the token introspect api
https://help.salesforce.com/s/articleView?id=sf.remoteaccess_oidc_token_introspection_endpoint.htm&type=5
You need to pass two additional parameters: client_id and client_secret
The client_id is the Consumer Key. You get it from the Connected App in Salesforce
The client_server is the Consumer Secret. You get it from Connected App in Salesforce
If the introspect token API returns a response with
{ active: false, ... }
it means that the access_token is expired and you need to issue a new one.
To issue a new access_token simply call the "/services/oauth2/token" again using the same JWT.

How to implement apple token based push notifications (using p8 file) in C#?

For an app with some kind of chat based features I want to add push notification support for receiving new messages.
What I want to do is use the new token based authentication (.p8 file) from Apple, but I can't find much info about the server part.
I came across the following post:
How to use APNs Auth Key (.p8 file) in C#?
However the answer was not satisfying as there was not much detail about how to:
establish a connection with APNs
use the p8 file (except for some kind of encoding)
send data to the Apple Push Notification Service

You can't really do this on raw .NET Framework at the moment. The new JWT-based APNS server uses HTTP/2 only, which .NET Framework does not yet support.
.NET Core's version of System.Net.Http, however, does, provided you meet the following prerequisites:
On Windows, you must be running Windows 10 Anniversary Edition (v1607) or higher, or the equivalent build of Windows Server 2016 (I think).
On Linux, you must have a version of libcurl that supports HTTP/2.
On macOS, you have to compile libcurl with support for HTTP/2, then use the DYLD_INSERT_LIBRARIES environment variable in order to load your custom build of libcurl.
You should be able to use .NET Core's version of System.Net.Http in the .NET Framework if you really want.
I have no idea what happens on Mono, Xamarin or UWP.
There are then three things you have to do:
Parse the private key that you have been given. This is currently an ECDSA key, and you can load this into a System.Security.Cryptography.ECDsa object.
On Windows, you can use the CNG APIs. After parsing the base64-encoded DER part of the key file, you can then create a key with new ECDsaCng(CngKey.Import(data, CngKeyBlobFormat.Pkcs8PrivateBlob)).
On macOS or Linux there is no supported API and you have to parse the DER structure yourself, or use a third-party library.
Create a JSON Web Token / Bearer Token. If you use the System.IdentityModel.Tokens.Jwt package from NuGet, this is fairly simple. You will need the Key ID and Team ID from Apple.
public static string CreateToken(ECDsa key, string keyID, string teamID)
{
var securityKey = new ECDsaSecurityKey(key) { KeyId = keyID };
var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.EcdsaSha256);
var descriptor = new SecurityTokenDescriptor
{
IssuedAt = DateTime.Now,
Issuer = teamID,
SigningCredentials = credentials
};
var handler = new JwtSecurityTokenHandler();
var encodedToken = handler.CreateEncodedJwt(descriptor);
return encodedToken;
}
Send an HTTP/2 request. This is as normal, but you need to do two extra things:
Set yourRequestMessage.Version to new Version(2, 0) in order to make the request using HTTP/2.
Set yourRequestMessage.Headers.Authorization to new AuthenticationHeaderValue("bearer", token) in order to provide the bearer authentication token / JWT with your request.
Then just put your JSON into the HTTP request and POST it to the correct URL.

Because Token (.p8) APNs only works in HTTP/2, thus most of the solutions only work in .net Core. Since my project is using .net Framework, some tweak is needed. If you're using .net Framework like me, please read on.
I search here and there and encountered several issues, which I managed to fix and pieced them together.
Below is the APNs class that actually works. I created a new class library for it, and placed the .P8 files within the AuthKeys folder of the class library. REMEMBER to right click on the .P8 files and set it to "Always Copy". Refer Get relative file path in a class library project that is being referenced by a web project.
After that, to get the location of the P8 files, please use AppDomain.CurrentDomain.RelativeSearchPath for web project or AppDomain.CurrentDomain.BaseDirectory for win application. Refer Why AppDomain.CurrentDomain.BaseDirectory not contains "bin" in asp.net app?
To get the token from the P8, you'll need to use the BouncyCastle class, please download it from Nuget.
using Jose;
using Newtonsoft.Json;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.OpenSsl;
using Security.Cryptography;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
namespace PushLibrary
{
public class ApplePushNotificationPush
{
//private const string WEB_ADDRESS = "https://api.sandbox.push.apple.com:443/3/device/{0}";
private const string WEB_ADDRESS = "https://api.push.apple.com:443/3/device/{0}";
private string P8_PATH = AppDomain.CurrentDomain.RelativeSearchPath + #"\AuthKeys\APNs_AuthKey.p8";
public ApplePushNotificationPush()
{
}
public async Task<bool> SendNotification(string deviceToken, string title, string content, int badge = 0, List<Tuple<string, string>> parameters = null)
{
bool success = true;
try
{
string data = System.IO.File.ReadAllText(P8_PATH);
List<string> list = data.Split('\n').ToList();
parameters = parameters ?? new List<Tuple<string, string>>();
string prk = list.Where((s, i) => i != 0 && i != list.Count - 1).Aggregate((agg, s) => agg + s);
ECDsaCng key = new ECDsaCng(CngKey.Import(Convert.FromBase64String(prk), CngKeyBlobFormat.Pkcs8PrivateBlob));
string token = GetProviderToken();
string url = string.Format(WEB_ADDRESS, deviceToken);
HttpRequestMessage httpRequestMessage = new HttpRequestMessage(HttpMethod.Post, url);
httpRequestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
httpRequestMessage.Headers.TryAddWithoutValidation("apns-push-type", "alert"); // or background
httpRequestMessage.Headers.TryAddWithoutValidation("apns-id", Guid.NewGuid().ToString("D"));
//Expiry
//
httpRequestMessage.Headers.TryAddWithoutValidation("apns-expiration", Convert.ToString(0));
//Send imediately
httpRequestMessage.Headers.TryAddWithoutValidation("apns-priority", Convert.ToString(10));
//App Bundle
httpRequestMessage.Headers.TryAddWithoutValidation("apns-topic", "com.xxx.yyy");
//Category
httpRequestMessage.Headers.TryAddWithoutValidation("apns-collapse-id", "test");
//
var body = JsonConvert.SerializeObject(new
{
aps = new
{
alert = new
{
title = title,
body = content,
time = DateTime.Now.ToString()
},
badge = 1,
sound = "default"
},
acme2 = new string[] { "bang", "whiz" }
});
httpRequestMessage.Version = new Version(2, 0);
using (var stringContent = new StringContent(body, Encoding.UTF8, "application/json"))
{
//Set Body
httpRequestMessage.Content = stringContent;
Http2Handler.Http2CustomHandler handler = new Http2Handler.Http2CustomHandler();
handler.SslProtocols = System.Security.Authentication.SslProtocols.Tls12 | System.Security.Authentication.SslProtocols.Tls11 | System.Security.Authentication.SslProtocols.Tls;
//handler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true;
//Continue
using (HttpClient client = new HttpClient(handler))
{
HttpResponseMessage resp = await client.SendAsync(httpRequestMessage).ContinueWith(responseTask =>
{
return responseTask.Result;
});
if (resp != null)
{
string apnsResponseString = await resp.Content.ReadAsStringAsync();
handler.Dispose();
}
handler.Dispose();
}
}
}
catch (Exception ex)
{
success = false;
}
return success;
}
private string GetProviderToken()
{
double epochNow = (int)DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1)).TotalSeconds;
Dictionary<string, object> payload = new Dictionary<string, object>()
{
{ "iss", "YOUR APPLE TEAM ID" },
{ "iat", epochNow }
};
var extraHeaders = new Dictionary<string, object>()
{
{ "kid", "YOUR AUTH KEY ID" },
{ "alg", "ES256" }
};
CngKey privateKey = GetPrivateKey();
return JWT.Encode(payload, privateKey, JwsAlgorithm.ES256, extraHeaders);
}
private CngKey GetPrivateKey()
{
using (var reader = File.OpenText(P8_PATH))
{
ECPrivateKeyParameters ecPrivateKeyParameters = (ECPrivateKeyParameters)new PemReader(reader).ReadObject();
var x = ecPrivateKeyParameters.Parameters.G.AffineXCoord.GetEncoded();
var y = ecPrivateKeyParameters.Parameters.G.AffineYCoord.GetEncoded();
var d = ecPrivateKeyParameters.D.ToByteArrayUnsigned();
return EccKey.New(x, y, d);
}
}
}
}
Secondly, if you noticed, I am using the custom WinHTTPHandler to make the code to support HTTP/2 based on How to make the .net HttpClient use http 2.0?. I am creating this using another class library, remember to download WinHTTPHandler from Nuget.
public class Http2CustomHandler : WinHttpHandler
{
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
request.Version = new Version("2.0");
return base.SendAsync(request, cancellationToken);
}
}
After that, just call the "SendNotification" on the ApplePushNotificationPush class and you should get the message on your iPhone.

private string GetToken()
{
var dsa = GetECDsa();
return CreateJwt(dsa, "keyId", "teamId");
}
private ECDsa GetECDsa()
{
using (TextReader reader = System.IO.File.OpenText("AuthKey_xxxxxxx.p8"))
{
var ecPrivateKeyParameters =
(ECPrivateKeyParameters)new Org.BouncyCastle.OpenSsl.PemReader(reader).ReadObject();
var q = ecPrivateKeyParameters.Parameters.G.Multiply(ecPrivateKeyParameters.D).Normalize();
var qx = q.AffineXCoord.GetEncoded();
var qy = q.AffineYCoord.GetEncoded();
var d = ecPrivateKeyParameters.D.ToByteArrayUnsigned();
// Convert the BouncyCastle key to a Native Key.
var msEcp = new ECParameters {Curve = ECCurve.NamedCurves.nistP256, Q = {X = qx, Y = qy}, D = d};
return ECDsa.Create(msEcp);
}
}
private string CreateJwt(ECDsa key, string keyId, string teamId)
{
var securityKey = new ECDsaSecurityKey(key) { KeyId = keyId };
var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.EcdsaSha256);
var descriptor = new SecurityTokenDescriptor
{
IssuedAt = DateTime.Now,
Issuer = teamId,
SigningCredentials = credentials,
};
var handler = new JwtSecurityTokenHandler();
var encodedToken = handler.CreateEncodedJwt(descriptor);
return encodedToken;
}

It have tried the above on ASP.NET CORE 2.1 and 2.2 to no avail. The response I always got was "The message received was unexpected or badly formatted" with HttpVersion20 enabled, which made me doubt whether http2 implementation is concrete.
Below is what worked on ASP.NET CORE 3.0;
var teamId = "YOURTEAMID";
var keyId = "YOURKEYID";
try
{
//
var data = await System.IO.File.ReadAllTextAsync(Path.Combine(_environment.ContentRootPath, "apns/"+config.P8FileName));
var list = data.Split('\n').ToList();
var prk = list.Where((s, i) => i != 0 && i != list.Count - 1).Aggregate((agg, s) => agg + s);
//
var key = new ECDsaCng(CngKey.Import(Convert.FromBase64String(prk), CngKeyBlobFormat.Pkcs8PrivateBlob));
//
var token = CreateToken(key, keyId, teamId);
//
var deviceToken = "XXXXXXXXXXXXXXXXXXXXXXXXXXXX";
var url = string.Format("https://api.sandbox.push.apple.com/3/device/{0}", deviceToken);
var request = new HttpRequestMessage(HttpMethod.Post, url);
//
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
//
request.Headers.TryAddWithoutValidation("apns-push-type", "alert"); // or background
request.Headers.TryAddWithoutValidation("apns-id", Guid.NewGuid().ToString("D"));
//Expiry
//
request.Headers.TryAddWithoutValidation("apns-expiration", Convert.ToString(0));
//Send imediately
request.Headers.TryAddWithoutValidation("apns-priority", Convert.ToString(10));
//App Bundle
request.Headers.TryAddWithoutValidation("apns-topic", "com.xx.yy");
//Category
request.Headers.TryAddWithoutValidation("apns-collapse-id", "test");
//
var body = JsonConvert.SerializeObject(new
{
aps = new
{
alert = new
{
title = "Test",
body = "Sample Test APNS",
time = DateTime.Now.ToString()
},
badge = 1,
sound = "default"
},
acme2 = new string[] { "bang", "whiz" }
})
//
request.Version = HttpVersion.Version20;
//
using (var stringContent = new StringContent(body, Encoding.UTF8, "application/json"))
{
//Set Body
request.Content = stringContent;
_logger.LogInformation(request.ToString());
//
var handler = new HttpClientHandler();
//
handler.SslProtocols = SslProtocols.Tls12 | SslProtocols.Tls11 | SslProtocols.Tls;
//
handler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true;
//Continue
using (HttpClient client = new HttpClient(handler))
{
//
HttpResponseMessage resp = await client.SendAsync(request).ContinueWith(responseTask =>
{
return responseTask.Result;
//
});
//
_logger.LogInformation(resp.ToString());
//
if (resp != null)
{
string apnsResponseString = await resp.Content.ReadAsStringAsync();
//
handler.Dispose();
//ALL GOOD ....
return;
}
//
handler.Dispose();
}
}
}
catch (HttpRequestException e)
{
_logger.LogError(5, e.StackTrace, e);
}
For CreateToken() Refer Above Recommended solution by yaakov,

I has a problem like you. And i seen #gorniv answer. So it's work with me!
May be you can use: https://www.nuget.org/packages/Apple.Auth.Signin for it!
Goodluck!

c# How to verify signature JWT?

I have a token, a file containing public key and I want to verify the signature.
I tried to verify signature based on this.
However, decodedCrypto and decodedSignature don't match.
Here is my code:
public static string Decode(string token, string key, bool verify)
{
var parts = token.Split('.');
var header = parts[0];
var payload = parts[1];
byte[] crypto = Base64UrlDecode(parts[2]);
var headerJson = Encoding.UTF8.GetString(Base64UrlDecode(header));
var headerData = JObject.Parse(headerJson);
var payloadJson = Encoding.UTF8.GetString(Base64UrlDecode(payload));
var payloadData = JObject.Parse(payloadJson);
if (verify)
{
var bytesToSign = Encoding.UTF8.GetBytes(string.Concat(header, ".", payload));
var keyBytes = Encoding.UTF8.GetBytes(key);
var algorithm = (string)headerData["alg"];
var signature = HashAlgorithms[GetHashAlgorithm(algorithm)](keyBytes, bytesToSign);
var decodedCrypto = Convert.ToBase64String(crypto);
var decodedSignature = Convert.ToBase64String(signature);
if (decodedCrypto != decodedSignature)
{
throw new ApplicationException(string.Format("Invalid signature. Expected {0} got {1}", decodedCrypto, decodedSignature));
}
}
return payloadData.ToString();
}
I'm sure that the signature of token is valid. I try to verify on https://jwt.io/ and it showed that Signature verified.
So the problem is the algorithm to encode, decode.
Is there anyone can solve this problem? The algorithm is RS256

How about using JwtSecurityTokenHandler?
it could look something like this:
public bool ValidateToken(string token, byte[] secret)
{
var tokenHandler = new JwtSecurityTokenHandler();
var validationParameters = new TokenValidationParameters
{
ValidateIssuerSigningKey = true,
IssuerSigningToken = new BinarySecretSecurityToken(secret)
};
SecurityToken validatedToken;
try
{
tokenHandler.ValidateToken(token, validationParameters, out validatedToken);
}
catch (Exception)
{
return false;
}
return validatedToken != null;
}
Be aware I haven't tested it but we used a similar implementation in one of the projects

I finally got a solution from my colleague.
For those who have the same problem, try my code:
public static string Decode(string token, string key, bool verify = true)
{
string[] parts = token.Split('.');
string header = parts[0];
string payload = parts[1];
byte[] crypto = Base64UrlDecode(parts[2]);
string headerJson = Encoding.UTF8.GetString(Base64UrlDecode(header));
JObject headerData = JObject.Parse(headerJson);
string payloadJson = Encoding.UTF8.GetString(Base64UrlDecode(payload));
JObject payloadData = JObject.Parse(payloadJson);
if (verify)
{
var keyBytes = Convert.FromBase64String(key); // your key here
AsymmetricKeyParameter asymmetricKeyParameter = PublicKeyFactory.CreateKey(keyBytes);
RsaKeyParameters rsaKeyParameters = (RsaKeyParameters)asymmetricKeyParameter;
RSAParameters rsaParameters = new RSAParameters();
rsaParameters.Modulus = rsaKeyParameters.Modulus.ToByteArrayUnsigned();
rsaParameters.Exponent = rsaKeyParameters.Exponent.ToByteArrayUnsigned();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.ImportParameters(rsaParameters);
SHA256 sha256 = SHA256.Create();
byte[] hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(parts[0] + '.' + parts[1]));
RSAPKCS1SignatureDeformatter rsaDeformatter = new RSAPKCS1SignatureDeformatter(rsa);
rsaDeformatter.SetHashAlgorithm("SHA256");
if (!rsaDeformatter.VerifySignature(hash, FromBase64Url(parts[2])))
throw new ApplicationException(string.Format("Invalid signature"));
}
return payloadData.ToString();
}
It works for me. The algorithm is RS256.

I know this is an old thread but I could have recommended you to use this library instead of writing on your own. It has got some good documentation to get started. Am using it without any issues.

byte[] crypto = Base64UrlDecode(parts[2]);
In this line you are base64 decoding signature part of JWT token, but as I know that part isn't base64 encoded. Please try this code. ( I have commented out unnecessary lines )
public static string Decode(string token, string key, bool verify)
{
var parts = token.Split('.');
var header = parts[0];
var payload = parts[1];
// byte[] crypto = Base64UrlDecode(parts[2]);
var jwtSignature = parts[2];
var headerJson = Encoding.UTF8.GetString(Base64UrlDecode(header));
var headerData = JObject.Parse(headerJson);
var payloadJson = Encoding.UTF8.GetString(Base64UrlDecode(payload));
var payloadData = JObject.Parse(payloadJson);
if (verify)
{
var bytesToSign = Encoding.UTF8.GetBytes(string.Concat(header, ".", payload));
var keyBytes = Encoding.UTF8.GetBytes(key);
var algorithm = (string)headerData["alg"];
var computedJwtSignature = Encoding.UTF8.GetString(HashAlgorithms[GetHashAlgorithm(algorithm)](keyBytes, bytesToSign));
// var decodedCrypto = Convert.ToBase64String(crypto);
// var decodedSignature = Convert.ToBase64String(signature);
if (jwtSignature != computedJwtSignature)
{
throw new ApplicationException(string.Format("Invalid signature. Expected {0} got {1}", decodedCrypto, decodedSignature));
}
}
return payloadData.ToString();
}

Google OAuth2 Service Account Access Token Request gives 'Invalid Request' Response

I'm trying to communicate with my app's enabled BigQuery API via the server to server method.
I've ticked all the boxes on this Google guide for constructing my JWT as best I can in C#.
And I've Base64Url encoded everything that was necessary.
However, the only response I get from google is a 400 Bad Request
"error" : "invalid_request"
I've made sure of all of the following from these other SO questions:
The signature is properly encrypted using RSA and SHA256
I am using POST and using application/x-www-form-urlencoded content type
Escaped all the backslashes in the claim set
Tried various grant_type and assertion values in the POST data
I get the same result when I use Fiddler. The error message is frustratingly lacking in detail! What else can I try?! Here's my code:
class Program
{
static void Main(string[] args)
{
// certificate
var certificate = new X509Certificate2(#"<Path to my certificate>.p12", "notasecret");
// header
var header = new { typ = "JWT", alg = "RS256" };
// claimset
var times = GetExpiryAndIssueDate();
var claimset = new
{
iss = "<email address of the client id of my app>",
scope = "https://www.googleapis.com/auth/bigquery",
aud = "https://accounts.google.com/o/oauth2/token",
iat = times[0],
exp = times[1],
};
// encoded header
var headerSerialized = JsonConvert.SerializeObject(header);
var headerBytes = Encoding.UTF8.GetBytes(headerSerialized);
var headerEncoded = Base64UrlEncode(headerBytes);
// encoded claimset
var claimsetSerialized = JsonConvert.SerializeObject(claimset);
var claimsetBytes = Encoding.UTF8.GetBytes(claimsetSerialized);
var claimsetEncoded = Base64UrlEncode(claimsetBytes);
// input
var input = headerEncoded + "." + claimsetEncoded;
var inputBytes = Encoding.UTF8.GetBytes(input);
// signiture
var rsa = certificate.PrivateKey as RSACryptoServiceProvider;
var cspParam = new CspParameters
{
KeyContainerName = rsa.CspKeyContainerInfo.KeyContainerName,
KeyNumber = rsa.CspKeyContainerInfo.KeyNumber == KeyNumber.Exchange ? 1 : 2
};
var aescsp = new RSACryptoServiceProvider(cspParam) { PersistKeyInCsp = false };
var signatureBytes = aescsp.SignData(inputBytes, "SHA256");
var signatureEncoded = Base64UrlEncode(signatureBytes);
// jwt
var jwt = headerEncoded + "." + claimsetEncoded + "." + signatureEncoded;
Console.WriteLine(jwt);
var client = new HttpClient();
var uri = "https://accounts.google.com/o/oauth2/token";
var post = new Dictionary<string, string>
{
{"assertion", jwt},
{"grant_type", "urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer"}
};
var content = new FormUrlEncodedContent(post);
var result = client.PostAsync(uri, content).Result;
Console.WriteLine(result);
Console.WriteLine(result.Content.ReadAsStringAsync().Result);
Console.ReadLine();
}
private static int[] GetExpiryAndIssueDate()
{
var utc0 = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
var issueTime = DateTime.Now;
var iat = (int)issueTime.Subtract(utc0).TotalSeconds;
var exp = (int)issueTime.AddMinutes(55).Subtract(utc0).TotalSeconds;
return new[]{iat, exp};
}
private static string Base64UrlEncode(byte[] input)
{
var output = Convert.ToBase64String(input);
output = output.Split('=')[0]; // Remove any trailing '='s
output = output.Replace('+', '-'); // 62nd char of encoding
output = output.Replace('/', '_'); // 63rd char of encoding
return output;
}
}

Looks like my guess in the comment above was correct. I got your code working by changing:
"urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer"
to:
"urn:ietf:params:oauth:grant-type:jwt-bearer"
Looks like you were accidentally double-encoding it.
I now get a response which looks something like:
{
"access_token" : "1/_5pUwJZs9a545HSeXXXXXuNGITp1XtHhZXXxxyyaacqkbc",
"token_type" : "Bearer",
"expires_in" : 3600
}
Edited Note: please make sure to have the correct date/time/timezone/dst configuration on your server. Having the clock off by even a few seconds will result in an invalid_grant error. http://www.time.gov will give the official time from the US govt, including in UTC.

Be sure to use DateTime.UtcNow instead of DateTime.Now in the GetExpiryAndIssueDate method.