ASP.NET Core 5 MVC web application - Login via xamarin

Question

I've developed my ASP.NET Core 5 MVC application with "Individual Login". Registering and logging within the app works fine.

Now I want to log in to my MVC web application with an API for my Xamarin App. From what I've read "JWT" should be used. I want to use as much "standard" in the backend as possible, ideally using standard APIs.

Unfortunately, all the sites I've tried could not help me (solution broken, non-existing urls,....).

Could somebody please post me a working tutorial or an example for the backend please.

Thanks, Jeppen

Answer 1

From api, you can configure the jwt authentication as this.

1. In Startup

    public void ConfigureServices(IServiceCollection services) { services.AddAuthentication(x => { x.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme; x.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme; }).AddJwtBearer(o => { o.TokenValidationParameters = new TokenValidationParameters { NameClaimType = JwtClaimTypes.Name, RoleClaimType = JwtClaimTypes.Role, //The previous three items are required ValidIssuer = "http://localhost:5000", ValidAudience = "api", IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes("this is a long key")) /***********************************default TokenValidationParameters parameter***********************************/ // RequireSignedTokens = true, // SaveSigninToken = false, // ValidateActor = false, }; }); services.AddControllers(); } public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { //... app.UseRouting(); app.UseAuthentication(); app.UseAuthorization(); //... }

2. Apply for a token, generate a string token in the action.

    public IActionResult Authenticate() { var tokenHandler = new JwtSecurityTokenHandler(); var key = Encoding.ASCII.GetBytes("this is a long key"); var authTime = DateTime.UtcNow; var expiresAt = authTime.AddDays(7); var tokenDescriptor = new SecurityTokenDescriptor { Subject = new ClaimsIdentity(new Claim[] { new Claim(JwtClaimTypes.Audience,"api"), new Claim(JwtClaimTypes.Issuer,"http://localhost:5000"), new Claim(JwtClaimTypes.Id, "10"), new Claim(JwtClaimTypes.Name, "my name"), new Claim(JwtClaimTypes.Email, "email"), }), Expires = expiresAt, SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature) }; var token = tokenHandler.CreateToken(tokenDescriptor); var tokenString = tokenHandler.WriteToken(token); return Ok(tokenString); }

3. Xamarin App receives token and save it. When Xamarin App access the authorized resource, it can carray this token with this header .

    var client = new HttpClient(); var token = client.GetAsync("[url that get the token] "); client.DefaultRequestHeaders.Add("Authorization", $"Bearer {token}"); client.GetAsync("[url that get the authorized resource] ");