Set up sign-in for multi-tenant Azure Active Directory using custom policies in Azure Active Directory B2C

Before you begin, use the selector above to choose the type of policy you’re configuring. Azure AD B2C offers two methods of defining how users interact with your applications: through predefined user flows, or through fully configurable custom policies. The steps required in this article are different for each method.

This feature is available for custom policies only. For setup steps, choose Custom policy above.

This article shows you how to enable sign-in for users using the multi-tenant endpoint for Azure Active Directory (Azure AD). Allowing users from multiple Azure AD tenants to sign in using Azure AD B2C, without you having to configure an identity provider for each tenant. However, guest members in any of these tenants will not be able to sign in. For that, you need to individually configure each tenant.

Prerequisites

Register an Azure AD app

To enable sign-in for users with an Azure AD account in Azure Active Directory B2C (Azure AD B2C), you need to create an application in Azure portal. For more information, see Register an application with the Microsoft identity platform.

  1. Sign in to the Azure portal.

  2. Make sure you're using the directory that contains your organizational Azure AD tenant (for example, contoso.com). Select the Directory + subscription filter in the top menu, and then choose the directory that contains your tenant.

  3. Choose All services in the top-left corner of the Azure portal, and then search for and select App registrations.

  4. Select New registration.

  5. Enter a Name for your application. For example, Azure AD B2C App.

  6. Select Accounts in any organizational directory (Any Azure AD directory – Multitenant) for this application.

  7. For the Redirect URI, accept the value of Web, and enter the following URL in all lowercase letters, where your-B2C-tenant-name is replaced with the name of your Azure AD B2C tenant.

    https://your-B2C-tenant-name.b2clogin.com/your-B2C-tenant-name.onmicrosoft.com/oauth2/authresp
    

    For example, https://fabrikam.b2clogin.com/fabrikam.onmicrosoft.com/oauth2/authresp.

    If you use a custom domain, enter https://your-domain-name/your-tenant-name.onmicrosoft.com/oauth2/authresp. Replace your-domain-name with your custom domain, and your-tenant-name with the name of your tenant.

  8. Select Register. Record the Application (client) ID for use in a later step.

  9. Select Certificates & secrets, and then select New client secret.

  10. Enter a Description for the secret, select an expiration, and then select Add. Record the Value of the secret for use in a later step.

Configuring optional claims

If you want to get the family_name, and given_name claims from Azure AD, you can configure optional claims for your application in the Azure portal UI or application manifest. For more information, see How to provide optional claims to your Azure AD app.

  1. Sign in to the Azure portal. Search for and select Azure Active Directory.
  2. From the Manage section, select App registrations.
  3. Select the application you want to configure optional claims for in the list.
  4. From the Manage section, select Token configuration.
  5. Select Add optional claim.
  6. For the Token type, select ID.
  7. Select the optional claims to add, family_name, and given_name.
  8. Click Add.

[Optional] Verify your app authenticity

Publisher verification helps your users understand the authenticity of the app you registered. A verified app means that the publisher of the app has verified their identity using their Microsoft Partner Network (MPN). Learn how to mark your app as publisher verified.

Create a policy key

You need to store the application key that you created in your Azure AD B2C tenant.

  1. Make sure you're using the directory that contains your Azure AD B2C tenant. Select the Directory + subscription filter in the top menu, and then choose the directory that contains your Azure AD B2C tenant.
  2. Choose All services in the top-left corner of the Azure portal, and then search for and select Azure AD B2C.
  3. Under Policies, select Identity Experience Framework.
  4. Select Policy keys and then select Add.
  5. For Options, choose Manual.
  6. Enter a Name for the policy key. For example, AADAppSecret. The prefix B2C_1A_ is added automatically to the name of your key when it's created, so its reference in the XML in following section is to B2C_1A_AADAppSecret.
  7. In Secret, enter your client secret that you recorded earlier.
  8. For Key usage, select Signature.
  9. Select Create.

Configure Azure AD as an identity provider

To enable users to sign in using an Azure AD account, you need to define Azure AD as a claims provider that Azure AD B2C can communicate with through an endpoint. The endpoint provides a set of claims that are used by Azure AD B2C to verify that a specific user has authenticated.

You can define Azure AD as a claims provider by adding Azure AD to the ClaimsProvider element in the extension file of your policy.

  1. Open the TrustFrameworkExtensions.xml file.

  2. Find the ClaimsProviders element. If it does not exist, add it under the root element.

  3. Add a new ClaimsProvider as follows:

    <ClaimsProvider>
      <Domain>commonaad</Domain>
      <DisplayName>Common AAD</DisplayName>
      <TechnicalProfiles>
        <TechnicalProfile Id="AADCommon-OpenIdConnect">
          <DisplayName>Multi-Tenant AAD</DisplayName>
          <Description>Login with your Contoso account</Description>
          <Protocol Name="OpenIdConnect"/>
          <Metadata>
            <Item Key="METADATA">https://login.microsoftonline.com/common/v2.0/.well-known/openid-configuration</Item>
            <!-- Update the Client ID below to the Application ID -->
            <Item Key="client_id">00000000-0000-0000-0000-000000000000</Item>
            <Item Key="response_types">code</Item>
            <Item Key="scope">openid profile</Item>
            <Item Key="response_mode">form_post</Item>
            <Item Key="HttpBinding">POST</Item>
            <Item Key="UsePolicyInRedirectUri">false</Item>
            <Item Key="DiscoverMetadataByTokenIssuer">true</Item>
            <!-- The key below allows you to specify each of the Azure AD tenants that can be used to sign in. Update the GUIDs below for each tenant. -->
            <Item Key="ValidTokenIssuerPrefixes">https://login.microsoftonline.com/00000000-0000-0000-0000-000000000000,https://login.microsoftonline.com/11111111-1111-1111-1111-111111111111</Item>
            <!-- The commented key below specifies that users from any tenant can sign-in. Uncomment if you would like anyone with an Azure AD account to be able to sign in. -->
            <!-- <Item Key="ValidTokenIssuerPrefixes">https://login.microsoftonline.com/</Item> -->
          </Metadata>
          <CryptographicKeys>
            <Key Id="client_secret" StorageReferenceId="B2C_1A_AADAppSecret"/>
          </CryptographicKeys>
          <OutputClaims>
            <OutputClaim ClaimTypeReferenceId="issuerUserId" PartnerClaimType="oid"/>
            <OutputClaim ClaimTypeReferenceId="tenantId" PartnerClaimType="tid"/>
            <OutputClaim ClaimTypeReferenceId="givenName" PartnerClaimType="given_name" />
            <OutputClaim ClaimTypeReferenceId="surName" PartnerClaimType="family_name" />
            <OutputClaim ClaimTypeReferenceId="displayName" PartnerClaimType="name" />
            <OutputClaim ClaimTypeReferenceId="authenticationSource" DefaultValue="socialIdpAuthentication" AlwaysUseDefaultValue="true" />
            <OutputClaim ClaimTypeReferenceId="identityProvider" PartnerClaimType="iss" />
          </OutputClaims>
          <OutputClaimsTransformations>
            <OutputClaimsTransformation ReferenceId="CreateRandomUPNUserName"/>
            <OutputClaimsTransformation ReferenceId="CreateUserPrincipalName"/>
            <OutputClaimsTransformation ReferenceId="CreateAlternativeSecurityId"/>
            <OutputClaimsTransformation ReferenceId="CreateSubjectClaimFromAlternativeSecurityId"/>
          </OutputClaimsTransformations>
          <UseTechnicalProfileForSessionManagement ReferenceId="SM-SocialLogin"/>
        </TechnicalProfile>
      </TechnicalProfiles>
    </ClaimsProvider>
    
  4. Under the ClaimsProvider element, update the value for Domain to a unique value that can be used to distinguish it from other identity providers.

  5. Under the TechnicalProfile element, update the value for DisplayName, for example, Multi-Tenant AAD. This value is displayed on the sign-in button on your sign-in page.

  6. Set client_id to the application ID of the Azure AD multi-tenant application that you registered earlier.

  7. Under CryptographicKeys, update the value of StorageReferenceId to the name of the policy key that created earlier. For example, B2C_1A_AADAppSecret.

Restrict access

Using https://login.microsoftonline.com/ as the value for ValidTokenIssuerPrefixes allows all Azure AD users to sign in to your application. Update the list of valid token issuers and restrict access to a specific list of Azure AD tenant users who can sign in.

To obtain the values, look at the OpenID Connect discovery metadata for each of the Azure AD tenants that you would like to have users sign in from. The format of the metadata URL is similar to https://login.microsoftonline.com/your-tenant/v2.0/.well-known/openid-configuration, where your-tenant is your Azure AD tenant name. For example:

https://login.microsoftonline.com/fabrikam.onmicrosoft.com/v2.0/.well-known/openid-configuration

Perform these steps for each Azure AD tenant that should be used to sign in:

  1. Open your browser and go to the OpenID Connect metadata URL for the tenant. Find the issuer object and record its value. It should look similar to https://login.microsoftonline.com/00000000-0000-0000-0000-000000000000/.
  2. Copy and paste the value into the ValidTokenIssuerPrefixes key. Separate multiple issuers with a comma. An example with two issuers appears in the previous ClaimsProvider XML sample.

Add a user journey

At this point, the identity provider has been set up, but it's not yet available in any of the sign-in pages. If you don't have your own custom user journey, create a duplicate of an existing template user journey, otherwise continue to the next step.

  1. Open the TrustFrameworkBase.xml file from the starter pack.
  2. Find and copy the entire contents of the UserJourney element that includes Id="SignUpOrSignIn".
  3. Open the TrustFrameworkExtensions.xml and find the UserJourneys element. If the element doesn't exist, add one.
  4. Paste the entire content of the UserJourney element that you copied as a child of the UserJourneys element.
  5. Rename the Id of the user journey. For example, Id="CustomSignUpSignIn".

Add the identity provider to a user journey

Now that you have a user journey, add the new identity provider to the user journey. You first add a sign-in button, then link the button to an action. The action is the technical profile you created earlier.

  1. Find the orchestration step element that includes Type="CombinedSignInAndSignUp", or Type="ClaimsProviderSelection" in the user journey. It's usually the first orchestration step. The ClaimsProviderSelections element contains a list of identity providers that a user can sign in with. The order of the elements controls the order of the sign-in buttons presented to the user. Add a ClaimsProviderSelection XML element. Set the value of TargetClaimsExchangeId to a friendly name.

  2. In the next orchestration step, add a ClaimsExchange element. Set the Id to the value of the target claims exchange Id. Update the value of TechnicalProfileReferenceId to the Id of the technical profile you created earlier.

The following XML demonstrates the first two orchestration steps of a user journey with the identity provider:

<OrchestrationStep Order="1" Type="CombinedSignInAndSignUp" ContentDefinitionReferenceId="api.signuporsignin">
  <ClaimsProviderSelections>
    ...
    <ClaimsProviderSelection TargetClaimsExchangeId="AzureADCommonExchange" />
  </ClaimsProviderSelections>
  ...
</OrchestrationStep>

<OrchestrationStep Order="2" Type="ClaimsExchange">
  ...
  <ClaimsExchanges>
    <ClaimsExchange Id="AzureADCommonExchange" TechnicalProfileReferenceId="AADCommon-OpenIdConnect" />
  </ClaimsExchanges>
</OrchestrationStep>

Configure the relying party policy

The relying party policy, for example SignUpSignIn.xml, specifies the user journey which Azure AD B2C will execute. Find the DefaultUserJourney element within relying party. Update the ReferenceId to match the user journey ID, in which you added the identity provider.

In the following example, for the CustomSignUpOrSignIn user journey, the ReferenceId is set to CustomSignUpOrSignIn:

<RelyingParty>
  <DefaultUserJourney ReferenceId="CustomSignUpSignIn" />
  ...
</RelyingParty>

Upload the custom policy

  1. Sign in to the Azure portal.
  2. Select the Directory + Subscription icon in the portal toolbar, and then select the directory that contains your Azure AD B2C tenant.
  3. In the Azure portal, search for and select Azure AD B2C.
  4. Under Policies, select Identity Experience Framework.
  5. Select Upload Custom Policy, and then upload the two policy files that you changed, in the following order: the extension policy, for example TrustFrameworkExtensions.xml, then the relying party policy, such as SignUpSignIn.xml.

Test your custom policy

  1. Select your relying party policy, for example B2C_1A_signup_signin.
  2. For Application, select a web application that you previously registered. The Reply URL should show https://jwt.ms.
  3. Select the Run now button.
  4. From the sign-up or sign-in page, select Common AAD to sign in with Azure AD account.

To test the multi-tenant sign-in capability, perform the last two steps using the credentials for a user that exists another Azure AD tenant. Copy the Run now endpoint and open it in a private browser window, for example, Incognito Mode in Google Chrome or an InPrivate window in Microsoft Edge. Opening in a private browser window allows you to test the full user journey by not using any currently cached Azure AD credentials.

If the sign-in process is successful, your browser is redirected to https://jwt.ms, which displays the contents of the token returned by Azure AD B2C.

Next steps

Learn how to pass the Azure AD token to your application.