Authenticate your Cloud Run MCP server with IAP

Identity-Aware Proxy (IAP) lets you secure Model Context Protocol (MCP) servers deployed on Cloud Run with centralized identity verification. You can then configure clients such as the Gemini CLI or AI agents to authenticate through IAP and securely run tools on your remote server.

Before you begin

  1. Verify that you have the required roles.

  2. Enable Cloud Run in your project.

  3. Enable IAP in your project.

  4. Deploy an MCP server on Cloud Run.

Required roles

To get the permissions that you need to configure IAP authentication for Cloud Run MCP servers, ask your administrator to grant you the following IAM roles:

For more information about granting roles, see Manage access to projects, folders, and organizations.

You might also be able to get the required permissions through custom roles or other predefined roles.

Configure IAP on a Cloud Run service

To configure IAP on your Cloud Run MCP server, do the following:

  1. Grant the Cloud Run Invoker role (roles/run.invoker) to the IAP service agent:

    gcloud beta run services add-iam-policy-binding SERVICE_NAME \
    --member='serviceAccount:service-PROJECT_NUMBER@gcp-sa-iap.iam.gserviceaccount.com' \
    --role='roles/run.invoker'

    Replace the following:

    • SERVICE_NAME: the service name
    • PROJECT_NUMBER: your Google Cloud project number

  2. Enable IAP when you deploy a new service or deploy a new revision of an existing service:

    New service

    To deploy a new service with IAP enabled, run the gcloud beta run deploy command:

    gcloud beta run deploy SERVICE_NAME \
  --image=CONTAINER_IMAGE \
  --region=REGION \
  --project=PROJECT_ID \
  --allow-unauthenticated \
  --iap \
  --functional-type=mcp-server

    Replace the following:

    • SERVICE_NAME: the service name
    • CONTAINER_IMAGE: your container image
    • REGION: the region where you deploy your service
    • PROJECT_ID: the ID of the project where Cloud Run is enabled

    Existing service

    To deploy a new revision of an existing service with IAP enabled, run the gcloud beta run services update command:

    gcloud beta run services update SERVICE_NAME \
  --region=REGION \
  --iap \
  --functional-type=mcp-server

    Replace the following:

    • SERVICE_NAME: the service name
    • REGION: the region where you deploy your service

  3. Create and configure an OAuth client:

    To register your OAuth client's universal client ID for use with IAP, see Sharing OAuth clients for programmatic access.

    Record the following values:

    • OAuth client ID
    • OAuth client secret
    • Redirect URI

  4. To connect a client such as the Gemini CLI or your agent to your deployed MCP server, edit the ~/.gemini/settings.json file.

    Add the following configuration to your settings.json file:

    {
  "mcpServers": {
    "my_mcp_server": {
      "httpUrl": "https://SERVICE_URL",
      "oauth": {
        "enabled": "true",
        "clientId": "OAUTH_CLIENT_ID",
        "clientSecret": "OAUTH_CLIENT_SECRET",
        "scopes": [ "email", "openid" ],
        "redirectUri": "REDIRECT_URI"
      }
    }
  }
}

    Replace the following:

    • SERVICE_URL: your Cloud Run service URL
    • OAUTH_CLIENT_ID: the client ID from the OAuth client configuration
    • OAUTH_CLIENT_SECRET: the client secret from the OAuth client configuration
    • REDIRECT_URI: the redirect URI from the OAuth client configuration

Verify the connection

To verify that your client can authenticate through IAP and connect to the MCP server, do the following:

  1. In your terminal, start the Gemini CLI:

    gemini

  2. When prompted in your browser, complete the IAP authentication flow.

  3. Verify that the Gemini CLI successfully discovers and lists the tools provided by your MCP server.