Unable to query custom REST API within Azure AD B2C custom policy - azure-ad-b2c

Question

I'm trying to call our REST API when a new user signs up by creating a custom Azure AD B2C custom policy. I've attempted adding the call to the API both as a validation profile as described at Integrate REST API claims exchanges in your Azure AD B2C user journey as validation of user input, and as a user journey as described at Walkthrough: Integrate REST API claims exchanges in your Azure AD B2C user journey as an orchestration step.
I have not been able to get either scenario to work. In both cases, I receive the following error, "AADB2C90027: Basic credentials specified for 'REST-API-SignUp' are invalid. Check that the credentials are correct and that access has been granted by the resource."
When I use Application Insights in combination with adding the call to the API as validation of user input, I see "Exception of type 'Web.TPEngine.Providers.BadArgumentRetryNeededException' was thrown." In other Stack Overflow posts, I see that the BadArgumentRetryNeededException was associated with the IdentityExperienceFramework and ProxyIdentityExperienceFramework apps not being configured correctly and/or permission not being granted from one app to the other. However, I have verified multiple times that these are configured correctly and that they are referenced correctly in the TrustFrameworkExtensions.xml file, so I assume that this is not the problem.
I have tested calling the API both with and without basic authentication, and I receive the same error. Therefore, I'm also assuming that the problem is not with the API requiring basic authentication because I receive this error even when the API requires no authentication.
I'll copy some of the custom policies below.
Code from TrustFrameworkExtensions.xml:
<?xml version="1.0" encoding="utf-8" ?>
<TrustFrameworkPolicy
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.microsoft.com/online/cpim/schemas/2013/06"
PolicySchemaVersion="0.3.0.0"
TenantId="notrealtenantid.onmicrosoft.com"
PolicyId="B2C_1A_TrustFrameworkExtensions"
PublicPolicyUri="http://notrealtenantid.onmicrosoft.com/B2C_1A_TrustFrameworkExtensions">
<BasePolicy>
<TenantId>notrealtenantid.onmicrosoft.com</TenantId>
<PolicyId>B2C_1A_TrustFrameworkBase</PolicyId>
</BasePolicy>
<BuildingBlocks>
<ClaimsSchema>
<ClaimType Id="loyaltyNumber">
<DisplayName>loyaltyNumber</DisplayName>
<DataType>string</DataType>
<UserHelpText>Customer loyalty number</UserHelpText>
</ClaimType>
</ClaimsSchema>
</BuildingBlocks>
<ClaimsProviders>
<!-- Local account claims provider -->
<ClaimsProvider>
<DisplayName>Local Account SignIn</DisplayName>
<TechnicalProfiles>
<TechnicalProfile Id="login-NonInteractive">
<Metadata>
<!-- ProxyIdentityExperienceFramework -->
<Item Key="client_id">732c7aec-0080-4421-bdba-cb0a156b596f</Item>
<!-- IdentityExperienceFramework -->
<Item Key="IdTokenAudience">e66b1d02-a473-4a1a-8cc2-b5d22da7d92a</Item>
</Metadata>
<InputClaims>
<!-- ProxyIdentityExperienceFramework -->
<InputClaim ClaimTypeReferenceId="client_id" DefaultValue="732c7aec-0080-4421-bdba-cb0a156b596f" />
<!-- IdentityExperienceFramework -->
<InputClaim ClaimTypeReferenceId="resource_id" PartnerClaimType="resource" DefaultValue="e66b1d02-a473-4a1a-8cc2-b5d22da7d92a" />
</InputClaims>
</TechnicalProfile>
</TechnicalProfiles>
</ClaimsProvider>
<!-- Facebook claims provider -->
<ClaimsProvider>
<DisplayName>Facebook</DisplayName>
<TechnicalProfiles>
<TechnicalProfile Id="Facebook-OAUTH">
<Metadata>
<Item Key="client_id">1234</Item>
<Item Key="scope">email public_profile</Item>
<Item Key="ClaimsEndpoint">https://graph.facebook.com/me?fields=id,first_name,last_name,name,email</Item>
</Metadata>
</TechnicalProfile>
</TechnicalProfiles>
</ClaimsProvider>
<ClaimsProvider>
<DisplayName>REST APIs</DisplayName>
<TechnicalProfiles>
<!-- Custom Restful service -->
<TechnicalProfile Id="REST-API-SignUp">
<DisplayName>Validate user's input data and return loyaltyNumber claim</DisplayName>
<Protocol Name="Proprietary" Handler="Web.TPEngine.Providers.RestfulProvider, Web.TPEngine, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
<Metadata>
<Item Key="ServiceUrl">https://NotRealUrl.com/1/0/usercheck</Item>
<Item Key="AuthenticationType">None</Item>
<Item Key="SendClaimsIn">Body</Item>
</Metadata>
<InputClaims>
<InputClaim ClaimTypeReferenceId="email" />
<InputClaim ClaimTypeReferenceId="givenName" PartnerClaimType="firstName" />
<InputClaim ClaimTypeReferenceId="surname" PartnerClaimType="lastName" />
<InputClaim ClaimTypeReferenceId="objectId" PartnerClaimType="sub"/>
</InputClaims>
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="loyaltyNumber" PartnerClaimType="loyaltyNumber" />
</OutputClaims>
<UseTechnicalProfileForSessionManagement ReferenceId="SM-Noop" />
</TechnicalProfile>
</TechnicalProfiles>
</ClaimsProvider>
</ClaimsProviders>
<UserJourneys>
<UserJourney Id="SignUpOrSignIn">
<OrchestrationSteps>
<OrchestrationStep Order="1" Type="CombinedSignInAndSignUp" ContentDefinitionReferenceId="api.signuporsignin">
<ClaimsProviderSelections>
<ClaimsProviderSelection TargetClaimsExchangeId="FacebookExchange" />
<ClaimsProviderSelection ValidationClaimsExchangeId="LocalAccountSigninEmailExchange" />
</ClaimsProviderSelections>
<ClaimsExchanges>
<ClaimsExchange Id="LocalAccountSigninEmailExchange" TechnicalProfileReferenceId="SelfAsserted-LocalAccountSignin-Email" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- Check if the user has selected to sign in using one of the social providers -->
<OrchestrationStep Order="2" Type="ClaimsExchange">
<Preconditions>
<Precondition Type="ClaimsExist" ExecuteActionsIf="true">
<Value>objectId</Value>
<Action>SkipThisOrchestrationStep</Action>
</Precondition>
</Preconditions>
<ClaimsExchanges>
<ClaimsExchange Id="FacebookExchange" TechnicalProfileReferenceId="Facebook-OAUTH" />
<ClaimsExchange Id="SignUpWithLogonEmailExchange" TechnicalProfileReferenceId="LocalAccountSignUpWithLogonEmail" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- For social IDP authentication, attempt to find the user account in the directory. -->
<OrchestrationStep Order="3" Type="ClaimsExchange">
<Preconditions>
<Precondition Type="ClaimEquals" ExecuteActionsIf="true">
<Value>authenticationSource</Value>
<Value>localAccountAuthentication</Value>
<Action>SkipThisOrchestrationStep</Action>
</Precondition>
</Preconditions>
<ClaimsExchanges>
<ClaimsExchange Id="AADUserReadUsingAlternativeSecurityId" TechnicalProfileReferenceId="AAD-UserReadUsingAlternativeSecurityId-NoError" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- Show self-asserted page only if the directory does not have the user account already (i.e. we do not have an objectId).
This can only happen when authentication happened using a social IDP. If local account was created or authentication done
using ESTS in step 2, then an user account must exist in the directory by this time. -->
<OrchestrationStep Order="4" Type="ClaimsExchange">
<Preconditions>
<Precondition Type="ClaimsExist" ExecuteActionsIf="true">
<Value>objectId</Value>
<Action>SkipThisOrchestrationStep</Action>
</Precondition>
</Preconditions>
<ClaimsExchanges>
<ClaimsExchange Id="SelfAsserted-Social" TechnicalProfileReferenceId="SelfAsserted-Social" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- This step reads any user attributes that we may not have received when authenticating using ESTS so they can be sent
in the token. -->
<OrchestrationStep Order="5" Type="ClaimsExchange">
<Preconditions>
<Precondition Type="ClaimEquals" ExecuteActionsIf="true">
<Value>authenticationSource</Value>
<Value>socialIdpAuthentication</Value>
<Action>SkipThisOrchestrationStep</Action>
</Precondition>
</Preconditions>
<ClaimsExchanges>
<ClaimsExchange Id="AADUserReadWithObjectId" TechnicalProfileReferenceId="AAD-UserReadUsingObjectId" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- The previous step (SelfAsserted-Social) could have been skipped if there were no attributes to collect
from the user. So, in that case, create the user in the directory if one does not already exist
(verified using objectId which would be set from the last step if account was created in the directory. -->
<OrchestrationStep Order="6" Type="ClaimsExchange">
<Preconditions>
<Precondition Type="ClaimsExist" ExecuteActionsIf="true">
<Value>objectId</Value>
<Action>SkipThisOrchestrationStep</Action>
</Precondition>
</Preconditions>
<ClaimsExchanges>
<ClaimsExchange Id="AADUserWrite" TechnicalProfileReferenceId="AAD-UserWriteUsingAlternativeSecurityId" />
</ClaimsExchanges>
</OrchestrationStep>
<!-- Do Rest call.
NOTE!! Sign up works if this orchestration step is not included. -->
<OrchestrationStep Order="7" Type="ClaimsExchange">
<ClaimsExchanges>
<ClaimsExchange Id="GetLoyaltyData" TechnicalProfileReferenceId="REST-API-SignUp" />
</ClaimsExchanges>
</OrchestrationStep>
<OrchestrationStep Order="8" Type="SendClaims" CpimIssuerTechnicalProfileReferenceId="JwtIssuer" />
</OrchestrationSteps>
<ClientDefinition ReferenceId="DefaultWeb" />
</UserJourney>
</UserJourneys>
</TrustFrameworkPolicy>
Code from SignUpOrSignin.xml:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<TrustFrameworkPolicy
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.microsoft.com/online/cpim/schemas/2013/06"
PolicySchemaVersion="0.3.0.0"
TenantId="notrealtenantid.onmicrosoft.com"
PolicyId="B2C_1A_signup_signin"
PublicPolicyUri="http://notrealtenantid.onmicrosoft.com/B2C_1A_signup_signin"
DeploymentMode="Development"
UserJourneyRecorderEndpoint="urn:journeyrecorder:applicationinsights">
<BasePolicy>
<TenantId>notrealtenantid.onmicrosoft.com</TenantId>
<PolicyId>B2C_1A_TrustFrameworkExtensions</PolicyId>
</BasePolicy>
<RelyingParty>
<DefaultUserJourney ReferenceId="SignUpOrSignIn" />
<TechnicalProfile Id="PolicyProfile">
<DisplayName>PolicyProfile</DisplayName>
<Protocol Name="OpenIdConnect" />
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="displayName" />
<OutputClaim ClaimTypeReferenceId="givenName" />
<OutputClaim ClaimTypeReferenceId="surname" />
<OutputClaim ClaimTypeReferenceId="email" />
<OutputClaim ClaimTypeReferenceId="objectId" PartnerClaimType="sub"/>
<OutputClaim ClaimTypeReferenceId="identityProvider" />
<OutputClaim ClaimTypeReferenceId="loyaltyNumber" DefaultValue="" />
</OutputClaims>
<SubjectNamingInfo ClaimType="sub" />
</TechnicalProfile>
</RelyingParty>
</TrustFrameworkPolicy>
If I comment out orchestration step 7, which is the step that calls our REST API, then the sign up process works. So, the problem is isolated to the calling of the API.
Does anyone know what might be causing the "AADB2C90027: Basic credentials specified for 'REST-API-SignUp' are invalid. Check that the credentials are correct and that access has been granted by the resource." error? I'm at a loss because the API is not requiring basic authentication.

Answer 1

After some team discussion, it turns out that the Web Application Firewall (WAF) configured on our Azure Application Gateway was blocking the request and returning an HTTP response of 403 because B2C wasn't sending an HTTP header for User-Agent.
The request worked after disabling the WAF rule that was blocking it.
A feature request was created to have B2C send a User-Agent request header at https://feedback.azure.com/forums/34192--general-feedback/suggestions/35235046-send-a-user-agent-when-an-azure-ad-b2c-custom-poli
In the meantime, a workaround is to either disable the WAF rule that requires a User-Agent header, or to have B2C call an API that is not protected by a WAF.