How to add a User as a Member from another IDP? - azure-ad-b2c

Question

We have ADB2C tenant with a Identity Provider setup to an Okta setup in another Organization via Open ID Connect.
We have a Admin UI to add users. I see that GraphAPI has a createUser which takes a json with Password and changePwdOnFirstUse setting. This is fine to add a direct member to ADB2C.
The problem I have is that, how can I add the User from the other Okta
Organization so that when this user logs in to my App (and is authenticated by Okta), can login to my App.
At present, after authentication from Okta, we see User not found Error.
I suppose, I cannot add this user via Graph API using same createUser method as this user password is not something we are supposed to manage.
How do I add this other Organization user to ADB2C, so that I do not see this "User not found" issue?
Thanks.

Answer 1

Using Azure AD Graph API, you can create an external account user, with the userIdentities property of the user object being set to the sub (subject) claim of Okta's ID token:
{
"accountEnabled": false,
"displayName": "John Smith",
"mailNickname": "john.smith",
"otherMails": [
"john.smith#company.com"
],
"userIdentities": [
{
"issuer": "{okta-id-token-iss-claim-value}",
"issuerUserId": "{okta-id-token-sub-claim-value}"
}
],
"userPrincipalName": "{guid}#{your-tenant-name}.onmicrosoft.com"
}
where issuerUserId must be set to the base64 encoding for the sub claim of Okta's ID token.