add pomerium cloud run tutorial (#1397)

* add pomerium cloud run tutorial

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

* title lint

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* link

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* fmt

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* ahmet feedback

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* PR feedback

Signed-off-by: Travis Groth <tgroth@pomerium.com>

* Add gcp secrets info

Signed-off-by: Travis Groth <tgroth@pomerium.com>

* Update tutorials/cloud-run-with-pomerium-for-end-user-access/index.md

Co-authored-by: bobby <1544881+desimone@users.noreply.github.com>

* first quick edit pass during read-through

* second edit pass

* final edit, I think

* - break up shell script
- update dns config

* add links

* edit pass

* Update index.md

Co-authored-by: Todd Kopriva <43478937+ToddKopriva@users.noreply.github.com>
Co-authored-by: Travis Groth <travisgroth@users.noreply.github.com>

tutorials/cloud-run-with-pomerium-for-end-user-access/index.md

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+---
+title: Authorizing end users in Cloud Run with Pomerium
+description: Learn how to deploy Pomerium to Cloud Run and use it to protect other endpoints with authorization headers.
+author: travisgroth,desimone
+tags: Cloud Run, Pomerium
+date_published: 2020-09-01
+---
+
+This guide covers how to deploy Pomerium to Cloud Run, providing end-user authentication and authorization to other endpoints. The resulting configuration
+permits users with `@gmail.com` addresses to access an instance of `httpbin.org` hosted on Cloud Run.
+
+[Pomerium](https://www.pomerium.com) is an open source identity-aware proxy that enables secure access to internal applications. Pomerium provides a standardized
+interface to add access control to applications regardless of whether the application itself has authorization or authentication built in. Pomerium provides a 
+gateway for requests and can be used in situations where you'd typically consider using a VPN.
+
+Unlike [Cloud IAP](https://cloud.google.com/iap), Pomerium supports non-Google identity providers. You can also run Pomerium outside Google Cloud (such as on 
+other cloud providers and on-premises) and still use it to route or authorize traffic to Google Cloud targets such as Cloud Run or Cloud Functions.
+
+This guide assumes that you have editor access to a Google Cloud project that can be used for isolated testing and a DNS zone that you are able to control.
+DNS does not need to be inside Google Cloud for the example to work.
+
+## How it works
+
+Services on [Cloud Run](https://cloud.google.com/run) and [Cloud Functions](https://cloud.google.com/functions) can be restricted to only permit access with a 
+properly signed [identity token](https://cloud.google.com/run/docs/authenticating/service-to-service). This allows requests from other services running on
+Google Cloud or elsewhere to be securely authorized despite the endpoints being public.
+
+Browsers are not able to add these identity tokens to the `Authorization` header, so a proxy is required to authenticate end users to your Cloud Run service.
+Pomerium can perform this role by generating compatible tokens on behalf of end users and then acting as a proxy for their requests.
+
+You perform the following steps:
+
+- Add an IAM policy delegating `roles/run.invoker` permissions to a service account.
+- Run Pomerium with access to a key for the corresponding service account.
+- Publish DNS records for each protected application pointing to Pomerium.
+- Configure Pomerium with an appropriate policy and `enable_google_cloud_serverless_authentication`.
+
+The protected application delegates trust to a Google Cloud service account, which Pomerium runs as, and Pomerium performs user-based authorization for each
+route. This turns Pomerium into a bridge between a user-centric and a service-centric authorization model.
+
+## Setup
+
+To deploy Pomerium to Cloud Run, a [special image](https://console.cloud.google.com/gcr/images/pomerium-io/GLOBAL/pomerium) is available at
+`gcr.io/pomerium-io/pomerium-[VERSION]-cloudrun`. It allows sourcing configuration from Google Cloud Secret Manager, and it sets some defaults for Cloud Run to 
+keep configuration minimal. This example uses it to store identity provider credentials. Pomerium's
+[authorization policy](https://www.pomerium.com/reference/#policy) contains no secrets, so you can place it directly in an
+[environment variable](https://www.pomerium.io/reference/#configuration-settings).
+
+The [Dockerfile for this setup for Cloud Run](https://github.com/pomerium/pomerium/blob/master/.github/Dockerfile-cloudrun) is based on the Dockerfile in
+[vals-entrypoint](https://github.com/pomerium/vals-entrypoint).
+
+This image depends on a configuration file present at `/pomerium/config.yaml`, and can source it from Google Cloud Secret Manager. To do so, set
+`VALS_FILES=[secretref]:/pomerium/config.yaml` and set any other [Pomerium environment variables](https://www.pomerium.io/reference/#configuration-settings) 
+directly or with an additional `secretref`.
+
+The `secretref` format for Google Cloud Secret Manager is `ref+gcpsecrets://PROJECT/SECRET(#/key])`.
+
+### Identity provider credentials and secrets in `config.yaml`
+
+Set up Pomerium's [`config.yaml`](https://www.pomerium.com/reference/#shared-settings) to contain your identity provider credentials and secrets:
+
+    # config.yaml
+    authenticate_service_url: https://authn.cloudrun.pomerium.com
+    shared_secret: XXXXXX
+    cookie_secret: XXXXXX
+    idp_provider: "google"
+    idp_client_id: XXXXXX
+    idp_client_secret: "XXXXXX"
+
+### Subdomain and e-mail domain in `policy.template.yaml`
+
+Substitute `cloudrun.pomerium.com` for your own subdomain and your e-mail domain if appropriate:
+
+    # policy.template.yaml
+    # see https://www.pomerium.com/reference/#policy
+    - from: https://hello.cloudrun.pomerium.com
+      to: ${HELLO_URL}
+      allowed_domains:
+        - gmail.com
+      enable_google_cloud_serverless_authentication: true
+    - from: https://httpbin.cloudrun.pomerium.com
+      to: https://httpbin.org
+      pass_identity_headers: true
+      allowed_domains:
+        - gmail.com
+
+## Deployment
+
+This section includes the commands to configure and deploy Pomerium.
+
+1.  Ensure that you have set a default project:
+
+        gcloud config set default-project MYTESTPROJECT
+
+1.  Set up your environment:
+
+        # Install gcloud beta
+        gcloud components install beta
+
+        # Capture current project number
+        PROJECT=$(gcloud projects describe $(gcloud config get-value project) --format='get(projectNumber)')
+
+1.  Deploy your protected application:
+
+        gcloud run deploy hello --image=gcr.io/cloudrun/hello --region us-central1 --platform managed --no-allow-unauthenticated
+
+1.  Set the IAM policy:
+
+        gcloud run services add-iam-policy-binding hello --platform managed --region us-central1 \
+            --member=serviceAccount:${PROJECT}-compute@developer.gserviceaccount.com \
+            --role=roles/run.invoker
+
+1.  Rewrite the policy file with a unique `hello` service URL:
+
+        HELLO_URL=$(gcloud run services describe hello --platform managed --region us-central1 --format 'value(status.address.url)') envsubst <policy.template.yaml >policy.yaml
+
+1.  Install your base configuration in a Google Cloud secret:
+
+        gcloud secrets create --data-file config.yaml pomerium-config --replication-policy automatic
+
+1.  Grant the default compute account access to the secret:
+
+        gcloud secrets add-iam-policy-binding pomerium-config \
+            --member=serviceAccount:${PROJECT}-compute@developer.gserviceaccount.com \
+            --role=roles/secretmanager.secretAccessor
+
+1.  Deploy Pomerium with policy and configuration references:
+
+        gcloud run deploy pomerium --region us-central1 --platform managed --allow-unauthenticated --max-instances 1 \
+            --image=gcr.io/pomerium-io/pomerium:v0.10.0-rc2-cloudrun \
+            --set-env-vars VALS_FILES="/pomerium/config.yaml:ref+gcpsecrets://${PROJECT}/pomerium-config" \
+            --set-env-vars POLICY=$(base64 policy.yaml)
+
+## DNS
+
+Pomerium and end users need known hostnames to interact with. To provide this, set up
+[Custom Domain Mappings](https://cloud.google.com/run/docs/mapping-custom-domains) for each service.
+
+### Service names
+
+Names to map to each Cloud Run service:
+
+| Cloud Run service   | DNS name                             |
+| ------------------- | ------------------------------------ |
+| `hello`             | `hello-direct.cloudrun.pomerium.com` |
+| `pomerium`          | `hello.cloudrun.pomerium.com`        |
+| `pomerium`          | `authn.cloudrun.pomerium.com`        |
+| `pomerium`          | `httpbin.cloudrun.pomerium.com`      |
+
+ Substitute `cloudrun.pomerium.com` as appropriate.
+
+### Example commands
+
+```bash
+    # Set domain mappings for the protected routes and authenticate
+    gcloud beta run domain-mappings --platform managed --region us-central1 create --service=hello --domain hello-direct.cloudrun.pomerium.com
+    gcloud beta run domain-mappings --platform managed --region us-central1 create --service=pomerium --domain hello.cloudrun.pomerium.com
+    gcloud beta run domain-mappings --platform managed --region us-central1 create --service=pomerium --domain authn.cloudrun.pomerium.com
+    gcloud beta run domain-mappings --platform managed --region us-central1 create --service=pomerium --domain httpbin.cloudrun.pomerium.com
+
+    # Retrieve the records for configuration in your DNS provider
+    gcloud beta run domain-mappings describe --domain hello-direct.cloudrun.pomerium.com --platform managed --region us-central1 --format='get (status.resourceRecords)'
+    gcloud beta run domain-mappings describe --domain hello.cloudrun.pomerium.com --platform managed --region us-central1 --format='get (status.resourceRecords)'
+    gcloud beta run domain-mappings describe --domain authn.cloudrun.pomerium.com --platform managed --region us-central1 --format='get (status.resourceRecords)'
+    gcloud beta run domain-mappings describe --domain httpbin.cloudrun.pomerium.io --platform managed --region us-central1 --format='get (status.resourceRecords)'
+```
+
+## Results
+
+### Overview
+
+You should see two applications deployed: The `hello` app is your protected app, and `pomerium` is... Pomerium!
+
+![Cloud Run overview](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/cloudrun-overview.png)
+
+Pomerium allows unauthenticated access, but `hello` does not.
+
+Here are the domain mappings set up:
+
+![Cloud Run domains](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/cloudrun-domains.png)
+
+### Direct access
+
+Verify that you can't access the main application directly by visiting
+[`https://hello-direct.cloudrun.pomerium.com`](https://hello-direct.cloudrun.pomerium.com).
+
+![Hello Direct Access](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/hello-direct.png)
+
+You should see a 403 error, because you don't have the proper credentials.
+
+### Authenticated access
+
+1.  Go to [`https://hello.cloudrun.pomerium.com`](https://hello.cloudrun.pomerium.com).
+
+    You should see a sign-in page:
+
+    ![Hello sign-in](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/hello-signin.png)
+
+1.  Enter your credentials at the sign-in page.
+
+    After you enter your credentials, you should see a hello page:
+
+    ![Hello](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/hello-success.png)
+
+### Applications not running on Google Cloud
+
+If your target application is not running on Google Cloud, you can also perform your own header validation.
+
+1.  Go to [`https://httpbin.cloudrun.pomerium.com`](https://httpbin.cloudrun.pomerium.com/headers).
+
+    You should see your identity header set:
+
+    ![Hello](https://storage.googleapis.com/gcp-community/tutorials/cloud-run-with-pomerium-for-end-user-access/headers.png)
+
+See [getting user's identity](https://www.pomerium.com/docs/topics/getting-users-identity.html) for details on using this header.
+
+## What's next
+
+Learn more about Pomerium:
+
+  - [Pomerium home](https://www.pomerium.com)
+
+  - [Pomerium documentation](https://www.pomerium.com/docs/)
+
+  - [Pomerium solution guides](https://www.pomerium.com/guides/)
+
+  - [Pomerium Cloud Run guide](https://www.pomerium.com/guides/cloud-run.html)