Asp.Net Core 2.0 and Azure AD B2C for authentication on WebApp and API

Question

I have an existing small app that I use for test, it is in Asp.Net Core 1.1 for both the Web App and the API, the authentication is done using Azure AD B2C. I am trying to move it to .Net Core 2.0 but I can't figure how to get it working, I tried using both sample from GitHub Azure-Samples for Web App and API, but I have either an unauthorized or 500 error when trying to access the api, if you have a working example for calling a web api from a web app using 2.0 and protected by AD B2C it will be greatly appreciated.

Edit: The sample I use to test are : Web App : WebApp-OpenIDConnect-DotNet core2.0 Web Api : B2C-WebApi core2.0 , I changed the appsettings values to match my b2c directory.

For my asp.net core 1.1 test app I use the same samples as above but from the master branch, with the same value for appsettings.

Edit 2 by default, in startup.cs I have this :

        services.AddAuthentication()
            .AddJwtBearer(option => new JwtBearerOptions
            {
                Authority = string.Format("https://login.microsoftonline.com/tfp/{0}/{1}/v2.0/",
                Configuration["Authentication:AzureAd:Tenant"], Configuration["Authentication:AzureAd:Policy"]),
                Audience = Configuration["Authentication:AzureAd:ClientId"],
                Events = new JwtBearerEvents
                {
                    OnAuthenticationFailed = AuthenticationFailed
                }
            });

which gives me the following error:

Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request starting HTTP/1.1 GET http://localhost:44352/api/values/5
Microsoft.AspNetCore.Server.Kestrel:Error: Connection id "0HL89JHF4VBLM", Request id "0HL89JHF4VBLM:00000001": An unhandled exception was thrown by the application. System.InvalidOperationException: No authenticationScheme was specified, and there was no DefaultChallengeScheme found.

if modified services.AddAuthentication like that

        services.AddAuthentication(sharedOption =>
        {
            sharedOption.DefaultScheme = JwtBearerDefaults.AuthenticationScheme;
        })

the error is now

Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler:Information: Failed to validate the token xxx. Microsoft.IdentityModel.Tokens.SecurityTokenInvalidSignatureException: IDX10500: Signature validation failed. No security keys were provided to validate the signature. at System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler.ValidateSignature(String token, TokenValidationParameters validationParameters) at System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler.ValidateToken(String token, TokenValidationParameters validationParameters, SecurityToken& validatedToken) at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.d__6.MoveNext()

user_4917103 · Answer

I saw a pull request on the sample which correct this issue (Link), the services.AddAuthentication must be change to:

        services.AddAuthentication(options =>
          {
            options.DefaultScheme = JwtBearerDefaults.AuthenticationScheme;
                          })
            .AddJwtBearer(jwtOptions =>
            {
            jwtOptions.Authority = $"https://login.microsoftonline.com/tfp/{Configuration["Authentication:AzureAd:Tenant"]}/{Configuration["Authentication:AzureAd:Policy"]}/v2.0/";
            jwtOptions.Audience = Configuration["Authentication:AzureAd:ClientId"];
            jwtOptions.Events = new JwtBearerEvents
                              {
                OnAuthenticationFailed = AuthenticationFailed
                                  };
            });

Asp.Net Core 2.0 and Azure AD B2C for authentication on WebApp and API

2 Answers