/configuring-identity-aware-proxy-with-google-iap

name: configuring-identity-aware-proxy-with-google-iap
description: 'Configures Google Cloud Identity-Aware Proxy (IAP) via gcloud to enforce
  per-request identity verification on Compute Engine, App Engine, Cloud Run, and
  GKE, including IAM bindings, Access Context Manager access levels, session/reauth
  settings, and service-account programmatic access. Use when replacing VPN access
  with identity-based access to GCP backends or configuring context-aware, zero-trust
  policies for Google Cloud services.

  '
domain: cybersecurity
subdomain: zero-trust-architecture
tags:
- google-iap
- identity-aware-proxy
- gcp
- zero-trust
- access-context-manager
- cloud-run
- app-engine
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- PR.AA-01
- PR.AA-05
- PR.IR-01
- GV.PO-01
mitre_attack:
- T1078.004
- T1133
- T1021.007
mitre_f3:
  version: '1.1'
  tactics:
  - initial-access
  - positioning
  techniques:
  - id: F1006
    name: Account Takeover
    tactic: initial-access
    source: f3
  - id: F1004
    name: Access with Stolen Session Cookie
    tactic: initial-access
    source: f3
  - id: T1550.001
    name: 'Use Alternate Authentication Material: Application Access Token'
    tactic: initial-access
    source: attack
  - id: T1539
    name: Steal Web Session Cookie
    tactic: positioning
    source: attack

Configuring Identity-Aware Proxy with Google IAP

When to Use

• When protecting Google Cloud applications (App Engine, Cloud Run, GKE, Compute Engine) with identity-based access
• When implementing context-aware access requiring device posture and location verification
• When providing secure access to internal tools without VPN or public IP exposure
• When needing per-request authentication and authorization for web applications and TCP services
• When configuring programmatic access to IAP-protected resources using service accounts

**Do not use** for non-HTTP applications that cannot be placed behind an HTTPS load balancer, for public-facing applications that need unauthenticated access, or when applications handle their own authentication and IAP would conflict with existing auth flows.

Prerequisites

• Google Cloud project with billing enabled
• IAP API enabled (`gcloud services enable iap.googleapis.com`)
• Application deployed behind HTTPS Load Balancer, App Engine, or Cloud Run
• Cloud Identity or Google Workspace for user management
• Access Context Manager API enabled for access levels
• OAuth consent screen configured for the project

Workflow

Step 1: Enable IAP on Backend Services

Configure IAP for different GCP compute platforms.

# Enable required APIs
gcloud services enable iap.googleapis.com
gcloud services enable accesscontextmanager.googleapis.com

# Create OAuth consent screen
gcloud iap oauth-brands create \
  --application_title="Internal Applications" \
  --support_email=security@company.com

# Create OAuth client
gcloud iap oauth-clients create \
  projects/PROJECT_ID/brands/BRAND_ID \
  --display_name="IAP Web Client"

# === Enable IAP on Compute Engine Backend Service ===
gcloud compute backend-services update my-backend-service \
  --iap=enabled,oauth2-client-id=CLIENT_ID,oauth2-client-secret=CLIENT_SECRET \
  --global

# === Enable IAP on App Engine ===
gcloud iap web enable \
  --resource-type=app-engine \
  --oauth2-client-id=CLIENT_ID \
  --oauth2-client-secret=CLIENT_SECRET

# === Enable IAP on Cloud Run ===
# First grant IAP service account the Cloud Run Invoker role
gcloud run services add-iam-policy-binding my-service \
  --member="serviceAccount:service-PROJECT_NUM@gcp-sa-iap.iam.gserviceaccount.com" \
  --role="roles/run.invoker" \
  --region=us-central1

# Enable IAP on the Cloud Run backend service
gcloud compute backend-services update my-cloud-run-backend \
  --iap=enabled,oauth2-client-id=CLIENT_ID,oauth2-client-secret=CLIENT_SECRET \
  --global

# === Enable IAP TCP Forwarding for SSH/RDP ===
# No load balancer needed - uses IAP tunnel
gcloud compute instances add-iam-policy-binding my-vm \
  --member="group:developers@company.com" \
  --role="roles/iap.tunnelResourceAccessor" \
  --zone=us-central1-a

# SSH through IAP tunnel
gcloud compute ssh my-vm --zone=us-central1-a --tunnel-through-iap

# RDP through IAP tunnel
gcloud compute start-iap-tunnel my-windows-vm 3389 \
  --local-host-port=localhost:3390 \
  --zone=us-central1-a

Step 2: Configure IAM Bindings for Access Control

Grant access to specific users and groups with optional access level conditions.

# Grant basic access to a group
gcloud iap web add-iam-policy-binding \
  --resource-type=backend-services \
  --service=my-backend-service \
  --member="group:engineering@company.com" \
  --role="roles/iap.httpsResourceAccessor"

# Grant access with access level condition
gcloud iap web add-iam-policy-binding \
  --resource-type=backend-services \
  --service=finance-app \
  --member="group:finance@company.com" \
  --role="roles/iap.httpsResourceAccessor" \
  --condition='expression=request.auth.access_levels.exists(x, x == "accessPolicies/POLICY_ID/accessLevels/corporate-device"),title=RequireCorporateDevice,description=Requires managed corporate device'

# Grant access only during business hours
gcloud iap web add-iam-policy-binding \
  --resource-type=backend-services \
  --service=admin-console \
  --member="group:admins@company.com" \
  --role="roles/iap.httpsResourceAccessor" \
  --condition='expression=request.time.getHours("America/New_York") >= 8 && request.time.getHours("America/New_York") <= 18 && request.time.getDayOfWeek("America/New_York") >= 1 && request.time.getDayOfWeek("America/New_York") <= 5,title=BusinessHoursOnly'

# Grant access to a specific URL path
gcloud iap web add-iam-policy-binding \
  --resource-type=backend-services \
  --service=internal-api \
  --member="group:api-consumers@company.com" \
  --role="roles/iap.httpsResourceAccessor" \
  --condition='expression=request.path.startsWith("/api/v2