I am using Azure AD B2C and I want a group based user distribution for my application. Lets say I have two subdomains subA.myapp.com and subB.myapp.com. On the other hand, I have two groups subA and subBin Azure B2C. Now a user wants to signin to subA.myapp.com, but is not a member of group subA, I would like to deny the user to sign in.
I know that Azure B2C does not include group info in the access token. So I will actually use Graph API to get the group membership of the user. But I am not quite sure if there is an appropriate event where I could intercept the validation process and manually deny a user to sign-in. Also, I thought I could use one of the *Validator methods of TokenValidationParameters but not sure which one.
I have read Authorize By Group in Azure Active Directory B2C. My problem is different because that problem is trying to protect only some actions based on group memberships, I want to prevent the whole login process to fail based on group membership.