Securely implementing OAuth2 authentication in an ASP.NET Core application
I'm optimizing some code but I've hit a wall trying to I'm trying to configure Currently developing a web application using ASP.NET Core where I need to integrate OAuth2 authentication with a third-party provider. After researching and trying various approaches, I have set up the necessary NuGet packages, including `Microsoft.AspNetCore.Authentication.OAuth` and `IdentityModel`, but the implementation isn’t behaving as expected. I've defined the authentication in `Startup.cs` as follows: ```csharp public void ConfigureServices(IServiceCollection services) { services.AddAuthentication(options => { options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme; options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme; }) .AddJwtBearer(options => { options.Authority = "https://your-oauth-provider.com"; options.Audience = "your-audience"; options.RequireHttpsMetadata = true; options.Events = new JwtBearerEvents { OnAuthenticationFailed = context => { Console.WriteLine("Authentication failed: " + context.Exception.Message); return Task.CompletedTask; } }; }); } ``` After implementing the above, I’m able to receive the token, but it doesn’t seem to be correctly validating on subsequent requests. I performed tests using Postman, sending the token as a Bearer token in the Authorization header, but receiving a `401 Unauthorized` response. To debug, I added logging for the authentication events but found no extensive logs indicating why it failed. I've also double-checked the scopes and permissions configured in the OAuth provider to ensure they match what I'm requesting. Another attempt involved manually validating the JWT token to isolate the problem, using the `System.IdentityModel.Tokens.Jwt` library: ```csharp var handler = new JwtSecurityTokenHandler(); var token = "your_jwt_token_here"; var validationParameters = new TokenValidationParameters { ValidateIssuerSigningKey = true, IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("your_secret_key")), ValidateIssuer = false, ValidateAudience = false }; SecurityToken validatedToken; var claimsPrincipal = handler.ValidateToken(token, validationParameters, out validatedToken); ``` Despite these efforts, I still face challenges getting a successful token validation. Could anyone provide insight into common pitfalls with OAuth2 in ASP.NET Core or suggest best practices I've possibly overlooked? Any help would be greatly appreciated. What's the best practice here? This issue appeared after updating to C# 3.11. Is this even possible?