Limiting Claims by App in Azure AD B2C - azure-ad-b2c

Question

We have 3 different applications requiring different sets of extension claims.
Application A - Claim A1, Claim A2, Claim A3
Application B - Claim B1, Claim B2, Claim B3
We defined the six Claims in TrustFrameworkExtensions, updated the various TechnicalProfiles to take the input from user and as well write it to directory.
To support the needs of the individual applications, we created 2 RP files, one for each Application and defined the User Journey's specific to the Apps.
The 6 claims are showing up for both Apps, and we want to restrict by App the Claims.
Tried to copy everything from TrustFrameworkExtensions into RP file, the RP does not load and throws an error as follows
Unable to upload policy. Reason : Validation failed: 3 validation error(s) found in policy "B2C_1A_1182017SIGNUP_SIGNIN" of tenant "XXXXXXXXX.onmicrosoft.com".
A required Metadata item with key "ApplicationObjectId" was not found in the TechnicalProfile with id "AAD-UserWriteUsingAlternativeSecurityId" in policy "B2C_1A_1182017signup_signin" of tenant "XXXXXXXXX.onmicrosoft.com".
A required Metadata item with key "ApplicationObjectId" was not found in the TechnicalProfile with id "AAD-UserWriteUsingLogonEmail" in policy "B2C_1A_1182017signup_signin" of tenant "XXXXXXXXX.onmicrosoft.com".
A required Metadata item with key "ApplicationObjectId" was not found in the TechnicalProfile with id "AAD-UserWriteProfileUsingObjectId" in policy "B2C_1A_1182017signup_signin" of tenant "XXXXXXXXX.onmicrosoft.com".
Appreciate advise and guidance to support multiple Apps with different claims.

Answer 1

To use extension attributes in your custom policy you need to add some configuration to your file involving the b2c-extensions-app that is automatically created and registered in the Portal for each B2C tenant.
In your case, you seem to be missing the ApplicationObjectID and possibly the ClientId of the b2c-extensions-app in the Metadata key section of your AAD-Common technical profile.
The Next Steps section of the Create Custom Attribute documentation describes how to perform this configuration.
https://learn.microsoft.com/en-us/azure/active-directory-b2c/custom-policy-custom-attributes#modify-your-custom-policy
Open the extensions file of your policy. For example, SocialAndLocalAccounts/TrustFrameworkExtensions.xml.
Find the ClaimsProviders element. Add a new ClaimsProvider to the ClaimsProviders element.
Replace ApplicationObjectId with the Object ID that you previously recorded. Then replace ClientId with the Application ID that you previously recorded in the below snippet.
<ClaimsProvider>
<DisplayName>Azure Active Directory</DisplayName>
<TechnicalProfiles>
<TechnicalProfile Id="AAD-Common">
<Metadata>
<!--Insert b2c-extensions-app application ID here, for example: 11111111-1111-1111-1111-111111111111-->
<Item Key="ClientId"></Item>
<!--Insert b2c-extensions-app application ObjectId here, for example: 22222222-2222-2222-2222-222222222222-->
<Item Key="ApplicationObjectId"></Item>
</Metadata>
</TechnicalProfile>
</TechnicalProfiles>
</ClaimsProvider>

Answer 2

Use <RelyingParty><TechnicalProfile><OutputClaims> to control the claims returned.
<RelyingParty>
<DefaultUserJourney ReferenceId="SignInAppA" />
<TechnicalProfile Id="PolicyProfile">
<DisplayName>PolicyProfile</DisplayName>
<Protocol Name="OpenIdConnect" />
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="ClaimA1" />
</OutputClaims>
<SubjectNamingInfo ClaimType="sub" />
</TechnicalProfile>
</RelyingParty>
and
<RelyingParty>
<DefaultUserJourney ReferenceId="SignInAppB" />
<TechnicalProfile Id="PolicyProfile">
<DisplayName>PolicyProfile</DisplayName>
<Protocol Name="OpenIdConnect" />
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="ClaimB1" />
</OutputClaims>
<SubjectNamingInfo ClaimType="sub" />
</TechnicalProfile>
</RelyingParty>