Get bearer token with MSAL.NET to access App Service with EasyAuth - azure

I have an Azure App Service which is authenticated using Azure AD EasyAuth.
I am trying to send a request from another App Service using C# and MSAL.NET (Microsoft.Identity.Client).
The authentication code looks like this
var app = ConfidentialClientApplicationBuilder
.Create(config.ClientId) // The Client ID in the App Registration connected to the App Service
.WithClientSecret(config.ClientSecret)
.WithAuthority(new Uri(config.Authority)) // https://login.microsoftonline.com/tenant.onmicrosoft.com/v2.0
.WithTenantId(config.TenantId) // Tenant Id Guid
.Build();
// Used Scopes: ["https://graph.microsoft.com/.default"]
var credentials = await app.AcquireTokenForClient(config.Scopes)
.ExecuteAsync(cancellationToken);
I get a bearer token successfully, but when I try to call the App Service with token injected to the headers I get a 401 and You do not have permission to view this directory or page. :(
Update 1:
I tried #Jim Xu answer and it's still giving me 401. It returns a www-authenticate header with the following value
The resource id is the same ClientId in the App Reg
Update 2 - Solution
So to summarize the fix:
The requested scopes when calling AcquireTokenForClient should include {Application ID Uri}/.default
In EasyAuth configuration, the Allowed Token Audiences needs to be set to the Application ID Uri as well

If you want to call the Azure API app which enables easy auth, please refer to the following steps
Get the Application ID URI of the AD application you use to enable easy auth
a. In the Azure portal menu, select Azure Active Directory or search for and select Azure Active Directory from any page.
b. Select App registrations > Owned applications > View all applications in this directory. Select your web app name, and then select Overview.
code
var app = ConfidentialClientApplicationBuilder
.Create(config.ClientId) // The Client ID in the App Registration connected to the App Service
.WithClientSecret(config.ClientSecret)
.WithAuthority(new Uri(config.Authority)) // https://login.microsoftonline.com/tenant.onmicrosoft.com/v2.0
.WithTenantId(config.TenantId) // Tenant Id Guid
.Build();
// Used Scopes: ["{Application ID URI}/.default"]
var credentials = await app.AcquireTokenForClient("{Application ID URI}/.default")
.ExecuteAsync(cancellationToken);
For more details, please refer to here.

Related

Azure AD, Multi-tenant, App Roles Assignment for users from another tenant

I'm working on web application that contains client side (SPA, angular 9) and backend (WebAPI, ASP.NET Core 3.0). Decided to use Application Roles feature to authorize users in our application. And i have requirement to be able to manage Application role assignments for users from our application UI via MSFT Graph API.
I registered MyAuthApp application in Azure AD TenantA. And created several App Roles there.
Authentication works fine. Client side gets token and attaches it to http requests to backend. Authorization also works fine i can extract app roles from the token and validate them.
Problem with adding Application role assignments for users from other AzureAD tenant -- TenantB. Seems that problem in GraphServiceClient configuration due to GraphApiAuth registered in TenantA.
Question: is this possible to add application role assignment for user from TenantB using GraphServiceClient authorized by Client Credentials in TenantA?
Right now when i do add role assignment i'm getting exception like resource with some Guid not found. This resource is a user (from TenantB).
This is a piece of code that adds user app role assignment. I see possible problem in GetGraphServiceClient function. It uses as authority URL with TenantA Id.
public async Task<AppRoleAssignment> AssignAppRoleToUser(Guid userId, Guid appRoleId)
{
var graphClient = await this.graphClientProvider.GetGraphServiceClient();
return await graphClient.Users[userId.ToString()].AppRoleAssignments.Request().AddAsync(
new AppRoleAssignment()
{
PrincipalId = userId,
AppRoleId = appRoleId,
ResourceId = this.graphAppSettingsProvider.GetAppRoleResourceIdAsGuid()
});
}
df0b3e71-fd2d-41a4-bfa9-0310b31395ae is Id of user from tenantB.
UPDATE:After further investigation i was able to assign App role for user from TenantB. But i had to change settings in the code that returns GraphServiceClient and provide TenantB Id and Application Service Principal Id from TenantB (instead of values from TenantA). But that's a problem. We would like to be able to assign application roles for users from any tenant and it will be not doable if we will have to provide TenantId and Service Principal Id for each tenant separately.
Is it possible to do this some how with some common settings?
This is how i get GraphServiceClient:
public async Task<GraphServiceClient> GetGraphServiceClient()
{
var clientId = this.graphAppSettingsProvider.GetClientId();
var clientSecret = this.graphAppSettingsProvider.GetClientSecret();
var tenantId = this.graphAppSettingsProvider.GetTenant();
var app = ConfidentialClientApplicationBuilder.Create(clientId)
.WithClientSecret(clientSecret)
.WithTenantId(tenantId)
.Build();
string[] scopes = {"https://graph.microsoft.com/.default"};
return new GraphServiceClient(
"https://graph.microsoft.com/v1.0",
new DelegateAuthenticationProvider((requestMessage) =>
{
var ar = app.AcquireTokenForClient(scopes).ExecuteAsync();
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("bearer", ar.Result.AccessToken);
return Task.FromResult(0);
}));
}
UPDATE 2
Changed a little requirements and now we just need to manage App Roles list for users from current user tenant. So, we changed permissions type from Application to Delegated to be behalf of authenticated user.
As i said earlier we have Angular app in pair with ASP.NET Core WebAPI backend. Angular app gets access token and sends it to backend in Authorizaiton header. When i attach with access token to GraphServiceClient request (header) i'm getting error "Access token validation failure. Invalid audience."
Question: is this correct flow to use access token from client for Graph API requests or should i get new access token for Graph API at backend using access token from client?
Any help/ideas appreciated. Thanks in advance!
First, you need to set up the MyAuthApp application as a multi-tenant application.
Next, run admin consent url in the browser, and then you need to log in with another tenant's administrator account and consent. The multi-tenant application will then be added to the target tenant as an enterprise application. https://login.microsoftonline.com/common/adminconsent?client_id={client-id}.
At the same time, the app role you created in tenant A will also be synchronized to the target tenant (for example, tenant B). Next, you only need to grant the app role of MyAuthApp to the users of tenant B through the Azure portal of tenant B or use ms graph api.

Authenticate Azure Function by Token with Resource

I have an Azure Function with Authorization/authnetication enabled via AD log in.
I am trying to authenticate by generating a token using client_credentials:
Refer to the following code below:
var tokenendpoint = "https://login.microsoftonline.com/172f05a2-f956-4856-b4c8-9580a54dbd56/oauth2/token";
string clientID = "eaeff78a-26ef-4bcb-b977-638316ff15b7";
string clientSecret = "HvVlipQkpuezmD4YiUcWVpZ5Cn1cP3vxiW61pSpDo8k=";
string resource = "eaeff78a-26ef-4bcb-b977-638316ff15b7"; //ClientID
string grantType = "client_credentials";
using (var reqToken = new WebClient())
{
NameValueCollection parameters = new NameValueCollection();
parameters.Add("client_id", clientID);
parameters.Add("client_secret", clientSecret);
parameters.Add("resource", resource);
parameters.Add("grant_type", grantType);
var responseTokenBytes = reqToken.UploadValues(tokenendpoint, "POST", parameters);
string responseTokenContent = Encoding.UTF8.GetString(responseTokenBytes).Replace(#"\", "");
azureFunctionTokenResponse = responseTokenContent.Deserialize<AzureFunctionTokenResponseBase>();
AzureFunctionToken = azureFunctionTokenResponse.access_token;
}
All works fine if I set the resource as the ClientID of my function.
However, in many examples online the Resource is set to the Azure Function Uri.
If I set my Resource to https://www.xxxxxx.azurewebsites.com then I get a 401 error.
Why is this?
I spent a whole day in getting this to finally work but nowhere in the docs does it say to enter the ClientID as the Resource??
If you use the same AAD app to enable Authorization/Authentication for your Azure Function and your client code to acquire the access_token for accessing your Azure Function, you could specify the resource to the Application ID (ClientID) or the App ID URI of your AAD app.
In general, we would use the ClientID as the resource, and App Service Authorization/Authentication would compare the Client ID you configured under Authentication / Authorization > Azure Active Directory Settings with the aud property of the incoming JWT bearer token, you could leverage https://jwt.io/ to decode your token.
However, in many examples online the Resource is set to the Azure Function Uri.
If I set my Resource to https://www.xxxxxx.azurewebsites.com then I get a 401 error.
I assume that those samples may use the App ID URI, you could set the App ID URI to https://www.xxxxxx.azurewebsites.com for your AAD app (Settings > Properties > App ID URI), then you could use App ID URI for the resource parameter.
Note: For this approach, you may need adjust the Azure Active Directory Settings for your Azure Function, you may keep the Client ID to the Application ID of your AAD app and add App ID URI to ALLOWED TOKEN AUDIENCES list or you could just replace it with your App ID URI.
Additionally, you could ADAL library for acquiring the token. Also, if you create each AAD app for your Azure Function and your client app, you could follow this issue.

Azure AD - Add app principal to a Group

I have an Azure AD app (AAD App1) which has user assignment enabled. So only, users from a particular group let's say "Group A" can access any resource (let's say an Azure Function API) protected by that Azure AD app.
Now I have another daemon Azure function job, which needs to make an authenticated call to the above mentioned Azure function API. Since this is a daemon job, I have generated another Azure AD app (AAD App2) for this.
Below is my code to get access tokens:
string resourceId = "id of app used to authenticate azure function"; // AAD app ID used by the Azure function for authentication
string clientId = "id of app registered for the daemon job";// AAD app ID of your console app
string clientSecret = "secret of app registered for the daemon job"; // Client secret of the AAD app registered for console app
string resourceUrl = "https://blahblah.azurewebsites.net/api/events";
string domain = "<mytenant>.onmicrosoft.com"; //Tenant domain
var accessToken = await TokenHelper.GetAppOnlyAccessToken(domain, resourceId, clientId, clientSecret);
Now when I try to generate access token to access the Azure function API, I get an invalid grant error as below:
AdalException:
{"error":"invalid_grant","error_description":"AADSTS50105: Application
'' is not assigned to a role for the application
''.\r\nTrace ID:
6df90cf440-c16d-480e-8daf-2349ddef3800\r\nCorrelation ID:
4c4bf7bf-2140-4e01-93e3-b85d1ddfc09d4d\r\nTimestamp: 2018-05-09
17:28:11Z","error_codes":[50105],"timestamp":"2018-05-09
17:28:11Z","trace_id":"690cf440-c16d-480e-8daf-2349ddef3800","correlation_id":"4c4bf7bf-2140-4e01-93ef3-b85d1dc09d4d"}:
Unknown error
I am able to properly generate AAD access tokens if I disable the user assignment.
I am trying to avoid creating a service account here. Is there anyway I can add an app principal to an Azure AD group or add it as a member of another Azure AD app?
Unfortunately, you cannot add an AAD application/service principal as a member of Azure AD group.
I have confirmed this issue in My Answer for another similar question [EDIT - now seems to be possible, see said answer]
You can also upvote this idea in our Feedback Forum. Azure AD Team will review it.
Hope this helps!

Azure AD token has already access to other app without permissions

We have 2 apps registered in Azure AD, let's call them WebApi1 and WebApi2.
WebApi1 needs to call WebApi2. A secret has been configured in WebApi1 in order to get a token. Here is the code I'm using to get the token and then make the call to WebApi2:
And here is how my WebApi2 is configured:
The thing that I don't understand is that I would expect WebApi2 to return a 401 exception since I have not set any permissions in Azure (via the App Registration portal) to WebApi1.
Yet, the call is made successfully and WebApi1 has access to WebApi2.
Why WebApi1 has access to WebApi2 without the use of permissions in Azure?
Your web api application should check access using the IsInRole() or the [Authorize] attribute. If your web api doesn't check access , by default the access token with no application roles(permission) could access to your web api .
Please refer to document Roles based access control in cloud applications using Azure AD . Since you are acquiring token with application identity (client credential flow) , please check the Assigning client applications to application roles of resource APIs section in the document .
Just another thing.
If you're working with Azure and roles, when setting the WindowsAzureActiveDirectoryBearerAuthenticationOptions, you'll need to set the right role type in order for IsInRole (or Authorize("YourRole")) to work.
app.UseWindowsAzureActiveDirectoryBearerAuthentication(
new WindowsAzureActiveDirectoryBearerAuthenticationOptions
{
TokenValidationParameters = new System.IdentityModel.Tokens.TokenValidationParameters
{
ValidateIssuer = false,
ValidAudience = ConfigurationManager.AppSettings["AzureAd:Audience"],
RoleClaimType = System.Security.Claims.ClaimTypes.Role
},
AuthenticationMode = Microsoft.Owin.Security.AuthenticationMode.Active,
Tenant = ConfigurationManager.AppSettings["AzureAd:Tenant"],
});

Getting Authorization has been denied for this request in Fiddler with Azure AD

I have created a ASP.Net Web API (.Net Framework) app with "Work or School Accounts" as authentication type. This automatically registers this API app in my Azure subscription and I can see it under "App Registrations". I can see that Home Page Url is pointing to localhost address. I can see that API is launching locally on localhost address. I then launch Fiddler to get access token from Azure AD. My POST request to endpoint https://login.microsoftonline.com/<mytenant>.onmicrosoft.com/oauth2/token. has following 4 parameters
grant_type=client_credentials
&client_id=<appid from Azure AD Portal>
&client_secret=<secret from Azure AD Portal>
&resource=<appid from Azure AD Portal>
I get a token back. When I decode this token, I see aud and appid as expected(matching appid in Azure AD). I use this token as bearer token to invoke API call by adding Authorization: Bearer <mytoken> header in GET request to https://localhost:44374/api/values. However, this GET call to my API is returning me {"Message":"Authorization has been denied for this request."} error message.
What am I missing?
You should use App ID URI as the resource value when acquiring token , you could find the App ID URI in Properties of api app in azure portal ,like https://xxxxx.onmicrosoft.com/WebApplicationName . Web api will check whether the aud claim in access token matches the one you set in web.config :
app.UseWindowsAzureActiveDirectoryBearerAuthentication(
new WindowsAzureActiveDirectoryBearerAuthenticationOptions
{
Tenant = ConfigurationManager.AppSettings["ida:Tenant"],
TokenValidationParameters = new TokenValidationParameters {
ValidAudience = ConfigurationManager.AppSettings["ida:Audience"]
},
});
ida:Audience value in web.config is the allowed audience .

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