How to do Authorization based on Azure AD groups?

Question

Hi I am trying to implement Azure Groups based authorization in my .net core app. I have more groups like 100 to 200. I have added policies to add authorization.

services.AddAuthorization(options =>
            {   
                options.AddPolicy("GroupsCheck", policy =>
                {
                    policy.AuthenticationSchemes.Add(JwtBearerDefaults.AuthenticationScheme);
                    policy.RequireAuthenticatedUser();
                    policy.Requirements.Add(new GroupsCheckRequirement("11b250bf-76c0-4efe-99f2-2d781bae43bb")); //currently hard coded but want to include all the groups returned from MS graph
                });
            });

Then

 GraphServiceClient client = await MicrosoftGraphClient.GetGraphServiceClient();
 var groupList = await client.Users[userId].TransitiveMemberOf.Request().GetAsync();

This will return more than 100 groups. Now in policy I want to include all these groups. Is hard coding in config file all the groups will better way? Also my JWT token has only hasgroups:true rather than group ids. So how can I authorize based on groups? can someone help me to find good way? thanks

Answer 1

I'm working on a blazor server application and have been struggling with exactly this issue so I thought I'd post my solution here :) In the AuthorizationPolicyBuilder, call the .RequireClaim() method and specify the string "groups" and the ObjectId of your security group.

Before this works though, you have to go into your

Azure portal -> Azure Ad -> app registrations -> token configurations -> add groups claim.

Make sure you check off the checkbox in Security Groups and the Group ID checkbox in { ID, Access, SAML }

I don't know if this is best practice, but it worked for me :)

Here's the code from Startup.cs

public void ConfigureServices(IServiceCollection services)
    {
        services.AddAuthentication(AzureADDefaults.AuthenticationScheme)
            .AddAzureAD(options => Configuration.Bind("AzureAd", options));

        services.AddControllersWithViews(options =>
        {
            var policy = new AuthorizationPolicyBuilder()
                .RequireAuthenticatedUser()
                .RequireClaim("groups", "<insert object id for group>")
                .Build();
            options.Filters.Add(new AuthorizeFilter(policy));
        });

    }

Answer 2

According to my test, if you just want to use groups based authorization, please refer to the following code:

1. change Startup.cs

services.AddAuthentication(AzureADDefaults.AuthenticationScheme)
      .AddAzureAD(options => configuration.Bind(configSectionName, options));
  services.Configure<AzureADOptions>(options => configuration.Bind(configSectionName, options));
services.Configure<OpenIdConnectOptions>(AzureADDefaults.OpenIdScheme, options =>
            {
options.Authority = options.Authority + "/v2.0/";
options.TokenValidationParameters.NameClaimType = "preferred_username";
 // Use the groups claim for populating roles
              options.TokenValidationParameters.RoleClaimType = "groups";
});
 services.AddMvc(options =>
      {
          var policy = new AuthorizationPolicyBuilder()
              .RequireAuthenticatedUser()
              .Build();
            options.Filters.Add(new AuthorizeFilter(policy));
            })
        .SetCompatibilityVersion(CompatibilityVersion.Latest);

2. Add the following code in the controller or method

if(User.Identity.IsAuthenticated){
   if (User.IsInRole("<group id>"))
            {
                 // do other action

            }
            else if (User?.FindFirst("_claim_names")?.Value != null)
            {

                /* call Graph API to check if the user is in the group

                     for example
                     GraphServiceClient client = await MicrosoftGraphClient.GetGraphServiceClient();
var memberOfGroups= await client.Me.TransitiveMemberOf.Request().GetAsync();


                    do
                    {
                        bool breakLoops = false;

                        foreach (var directoryObject in memberOfGroups.CurrentPage)
                        {
                            if (directoryObject is Group)
                            {
                                Group group = directoryObject as Group;
                                if (group.Id == "<group id>") {

                                    breakLoops = true;
                                    break;

                                }

                            }
                        }
                        if (breakLoops)
                        {
                            break;
                        }
                        if (memberOfGroups.NextPageRequest != null)
                        {
                            memberOfGroups = await memberOfGroups.NextPageRequest.GetAsync();
                        }
                        else
                        {
                            memberOfGroups = null;
                        }
                    } while (memberOfGroups != null);

               */


            }
            else {

                // do not have enough permissions
            }

}

For more details, please refer to the sample