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

apple-push-notifications, c#

Solution

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.

Problem

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

Original source

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