This article describes how to add authentication for a Box account to an Azure AD B2C custom policy.

Architecture

The following diagram illustrates the authentication flow for a Box account to an Azure AD B2C custom policy.

For information about Box and OAuth 2.0, see https://developer.box.com/guides/authentication/oauth2/.

Prerequisites

1. If you don’t already have one, then you must create an Azure AD B2C tenant that is linked to your Azure subscription.
2. Prepare your Azure AD B2C tenant by creating the token signing and encryption keys and creating the Identity Experience Framework applications.
3. Download one of the starter packs for Azure AD B2C from Microsoft’s GitHub repository.

Configure a Box application

1. Log in to https://app.box.com/developers/console.
2. On the My Apps page, select Create New App.
3. On the Create New App page, select Custom App.
4. In the Custom App dialogue, select User Authentication (OAuth 2.0), enter an application name, and then select Create App.
5. On the application page, in the Configuration tab, enter the following fields and then select Save Changes:
   1. OAuth 2.0 Redirect URI: Enter either https://your-tenant-name.b2clogin.com/your-tenant-name.onmicrosoft.com/oauth2/authresp if you use the built-in domain or https://your-domain-name/your-tenant-name.onmicrosoft.com/oauth2/authresp if you use a custom domain for the OAuth 2.0 Redirect URI field. Replace your-tenant-name with your tenant name and your-domain-name with your custom domain.
6. On the application page, in the Configuration tab, copy the Client ID and Client Secret fields.

Add the client secret for the Box application as a policy key

1. Sign in to the Azure AD B2C portal.
2. Select Identity Experience Framework.
3. Select Policy keys.
4. Select Add.
5. In the Create a key section, enter the following fields and then select Create:
   1. Options: Manual
   2. Name: BoxClientSecret
   3. Secret: Paste the Client Secret field that was copied in the previous section.

Configure Box as an identity provider

1. Open the TrustFrameworkExtensions.xml file.
2. Find the ClaimsProviders element. If it doesn’t exist, then add it to the TrustFrameworkPolicy element.
3. Add the following ClaimsProvider element to the ClaimsProviders element. Replace your-box-client-id with the Client ID field that was copied in the Configure a Box application section.

<ClaimsProvider>
  <Domain>box.com</Domain>
  <DisplayName>Box</DisplayName>
  <TechnicalProfiles>
    <TechnicalProfile Id="Box-OAuth2">
      <DisplayName>Box</DisplayName>
      <Protocol Name="OAuth2" />
      <Metadata>
        <Item Key="client_id">your-box-client-id</Item>
        <Item Key="authorization_endpoint">https://account.box.com/api/oauth2/authorize</Item>
        <Item Key="AccessTokenEndpoint">https://api.box.com/oauth2/token</Item>
        <Item Key="ClaimsEndpoint">https://api.box.com/2.0/users/me</Item>
        <Item Key="HttpBinding">POST</Item>
        <Item Key="BearerTokenTransmissionMethod">AuthorizationHeader</Item>
        <Item Key="UsePolicyInRedirectUri">false</Item>
      </Metadata>
      <CryptographicKeys>
        <Key Id="client_secret" StorageReferenceId="B2C_1A_BoxClientSecret" />
      </CryptographicKeys>
      <OutputClaims>
        <OutputClaim ClaimTypeReferenceId="authenticationSource" DefaultValue="socialIdpAuthentication" AlwaysUseDefaultValue="true" />
        <OutputClaim ClaimTypeReferenceId="identityProvider" DefaultValue="box.com" AlwaysUseDefaultValue="true" />
        <OutputClaim ClaimTypeReferenceId="issuerUserId" PartnerClaimType="id" />
        <OutputClaim ClaimTypeReferenceId="displayName" PartnerClaimType="name" />
        <OutputClaim ClaimTypeReferenceId="email" PartnerClaimType="login" />
      </OutputClaims>
      <OutputClaimsTransformations>
        <OutputClaimsTransformation ReferenceId="CreateRandomUPNUserName" />
        <OutputClaimsTransformation ReferenceId="CreateUserPrincipalName" />
        <OutputClaimsTransformation ReferenceId="CreateAlternativeSecurityId" />
      </OutputClaimsTransformations>
      <UseTechnicalProfileForSessionManagement ReferenceId="SM-SocialLogin" />
    </TechnicalProfile>
  </TechnicalProfiles>
</ClaimsProvider>

Add a user journey

1. Open the TrustFrameworkBase.xml file.
2. Copy the UserJourney element that includes Id="SignUpOrSignIn".
3. Open the TrustFrameworkExtensions.xml file and find the UserJourneys element. If it doesn’t exist, then add it to the TrustFrameworkPolicy element.
4. Paste the UserJourney element that was copied in step 2 to the UserJourneys element and replace the Id attribute for this UserJourney element from "SignUpOrSignIn" to "BoxSignUpOrSignIn".

Add the identity provider to the user journey

1. Add the claims provider that was configured in the Configure Box as an identity provider section to the user journey that was added in the previous section.

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

<OrchestrationStep Order="2" Type="ClaimsExchange">
  ...
  <ClaimsExchanges>
    <ClaimsExchange Id="BoxExchange" TechnicalProfileReferenceId="Box-OAuth2" />
  </ClaimsExchanges>
  ...
</OrchestrationStep>

Configure the relying party policy

1. Open the SignUpOrSignIn.xml file.
2. Replace the ReferenceId attribute for the DefaultUserJourney element from "SignUpOrSignIn" to "BoxSignUpOrSignIn".

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

Upload and test the custom policy

1. Upload all policy files in the following order to your Azure AD B2C tenant:
   1. TrustFrameworkBase.xml
   2. TrustFrameworkLocalization.xml
   3. TrustFrameworkExtensions.xml
   4. SignUpOrSignIn.xml
2. Test the B2C_1A_signup_signin policy from your Azure AD B2C tenant.

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