Overview of IAP for on-premises apps

Identity-Aware Proxy (IAP) allows you to manage access to HTTP-based apps outside of Google Cloud. This includes apps on-premises in your enterprise's data centers.

To learn how to secure on-premises apps with IAP, see Setting up IAP for on-premises apps.

Introduction

IAP targets on-premises apps with the IAP connector. This configurable Cloud Deployment Manager template creates the resources needed to host and deploy the IAP connector into a IAP-enabled Google Cloud project, forwarding authenticated and authorized requests to on-premises apps.

The configurable Cloud Deployment Manager template creates the following resources:

  • A Google Kubernetes Engine cluster that maintains Ambassador-based services.
  • A Cloud Load Balancing HTTP(S) load balancer that acts as the ingress controller for requests.
  • Routing rules.

A deployment can have multiple Ambassador-created Compute Engine backend services that run behind one HTTP(s) load balancer. Each backend service maps to an individual on-premises app.

Once the IAP connector is deployed, IAP secures your app with identity and context based Cloud Identity and Access Management (Cloud IAM) access policies. Because a Cloud IAM access policy is configured on the backend service resource level, you're able to have different access control lists for each of your on-premises apps. This means only one Google Cloud project is needed to manage access to multiple on-premises apps.

How IAP for on-premises apps works

When a request is sent to an app hosted on Google Cloud, IAP authenticates and authorizes the user requests. It then grants the user access to the Google Cloud app.

When a request is sent to an on-premises app, IAP authenticates and authorizes the user request. It then routes the request to the IAP connector. The IAP connector forwards the request through a site-to-site connection established with Cloud Interconnect from Google Cloud to the on-premises network.

The following diagram shows the high-level traffic flow of a web request for a Google Cloud app (app1) and an on-premises app (app2).

Routing rules

When configuring a IAP connector deployment, you configure the routing rules. These rules route authenticated and authorized web requests coming to your DNS hostname ingress point to the DNS hostname that's the destination.

The following is an example of routing parameters defined for a IAP connector Deployment Manager template.

   routing:
     - name: hr
       mapping:
        - name: host
          source: www.hr-domain.com
          destination: hr-internal.domain.com
        - name: sub
          source: sheets.hr-domain.com
          destination: sheets.hr-internal.domain.com
     - name: finance
       mapping:
        - name: host
          source: www.finance-domain.com
          destination: finance-internal.domain.com
  • Each routing name corresponds to a new, Ambassador-created Compute Engine backend service resource.
  • The mapping parameter specifies a list of Ambassador routing rules for a backend service.
  • The source of a routing rule is mapped to a destination, where source is the URL of requests coming to Google Cloud, and destination is the URL for your on-premises app that IAP routes traffic to after a user has been authorized and authenticated.

The following table demonstrates example rules to route incoming requests from www.hr-domain.com to hr-internal.domain.com:

Compute Engine backend service Routing rule name Source Destination
hr hr-host www.hr-domain.com hr-internal.domain.com
hr-sub sheets.hr-domain.com sheets.hr-internal.domain.com
finance finance-host www.finance-domain.com finance-internal.domain.com

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