Identity-Aware Proxy (IAP) controls access to web resources based on user identity and context, not network firewalls (like Option B). The tool used to define the contextual requirements (IP range) and identity (group membership) is an Access Level within Access Context Manager.

Access Level: Defines the required context (e.g., source IP range of the internal network) and the required identity attributes (e.g., user is a member of the AppDev group).

IAP Policy: The IAP policy for the Cloud Run application is then configured to only allow access if the user meets the conditions defined in the Access Level.

Extracts:

"Identity-Aware Proxy works by verifying a user's identity and context of the request to determine if the user should be allowed to access an application." (Source 3.1)

"When you set an IAP policy, you can define an Access Level from Context-Aware Access to enforce conditions based on user location (IP address), security status, and device policy, along with user identity/group membership." (Source 3.2)

"IAP with Context-Aware Access is the recommended zero-trust approach for enforcing both identity (AppDev group) and context (internal IP address) requirements." (Source 3.3)