Validating asymmetric jwt with public key

Startup.cs

// ... imports

namespace Authentication.WebClient {
    public class Startup {
        private readonly IConfiguration configuration;

        public Startup(IConfiguration configuration) {
            this.configuration = configuration;
        }

        public void ConfigureServices(IServiceCollection services) {
            services.AddControllers();
          
            /*
             * Configure validation of JWT signed with a private asymmetric key.
             * 
             * We'll use a public key to validate if the token was signed
             * with the corresponding private key.
             */
            services.AddSingleton<RsaSecurityKey>(provider => {
                // It's required to register the RSA key with depedency injection.
                // If you don't do this, the RSA instance will be prematurely disposed.
                
                RSA rsa = RSA.Create();
                rsa.ImportRSAPublicKey(
                    source: Convert.FromBase64String(configuration["Jwt:Asymmetric:PublicKey"]),
                    bytesRead: out int _
                );
                
                return new RsaSecurityKey(rsa);
            });
            services.AddAuthentication()
                .AddJwtBearer("Asymmetric", options => {
                    SecurityKey rsa = services.BuildServiceProvider().GetRequiredService<RsaSecurityKey>();
                    
                    options.IncludeErrorDetails = true; // <- great for debugging

                    // Configure the actual Bearer validation
                    options.TokenValidationParameters = new TokenValidationParameters {
                        IssuerSigningKey = rsa,
                        ValidAudience = "jwt-test",
                        ValidIssuer = "jwt-test",
                        RequireSignedTokens = true,
                        RequireExpirationTime = true, // <- JWTs are required to have "exp" property set
                        ValidateLifetime = true, // <- the "exp" will be validated
                        ValidateAudience = true,
                        ValidateIssuer = true,
                    };
                });
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            app.UseDeveloperExceptionPage();
            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization(); // <- allows the use of [Authorize] on controllers and actions

            app.UseEndpoints(endpoints => { endpoints.MapDefaultControllerRoute(); });
        }
    }
}