GenerateJWS.cs

using System.Collections.Generic;
using System.Net;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Http;
using Microsoft.Extensions.Logging;
using Azure.Identity;
using Azure.Security.KeyVault.Keys.Cryptography;
using System.Text;
using System.Security.Cryptography;
using System.Threading.Tasks;
using Microsoft.IdentityModel.Tokens;
using System.IdentityModel.Tokens.Jwt;
using Newtonsoft.Json;
using JwtHeaderParameterNames = Microsoft.IdentityModel.JsonWebTokens.JwtHeaderParameterNames;

namespace Company.Function
{
    public static class jwt_sign
    {
        private static ILogger _logger;
        [Function("jwt_sign")]
        public static async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req,
            FunctionContext executionContext)
        {
            _logger = executionContext.GetLogger("jwt_sign");
            _logger.LogInformation("C# HTTP trigger function processed a request.");

            var response = req.CreateResponse(HttpStatusCode.OK);
            response.Headers.Add("Content-Type", "text/plain; charset=utf-8");

            var rsaCryptoClient = new CryptographyClient(new System.Uri("https://hieuexamplekv.vault.azure.net/keys/logic/aa5c64a48038423da77482fd11b0a926"), new ManagedIdentityCredential());

            var token = new JwtSecurityToken(
                            "issuer",
                            "aud",
                            null,
                            null,
                            null);

            var header = Base64UrlEncoder.Encode(JsonConvert.SerializeObject(new Dictionary<string, string>()
            {
                { JwtHeaderParameterNames.Alg, "RS256" },
                { JwtHeaderParameterNames.Kid, "https://hieuexamplekv.vault.azure.net/keys/logic/aa5c64a48038423da77482fd11b0a926" },
                { JwtHeaderParameterNames.Typ, "JWT" }
            }));
            var byteData = Encoding.UTF8.GetBytes(header + "." + token.EncodedPayload);
            var hasher = new SHA256CryptoServiceProvider();
            var digest1 = hasher.ComputeHash(byteData);
            var signature = await rsaCryptoClient.SignAsync(SignatureAlgorithm.RS256, digest1);

            var ret1 = $"{header}.{token.EncodedPayload}.{Base64UrlEncoder.Encode(signature.Signature)}";

            response.WriteString(ret1);
            return response;
        }
    }
}