Add Azure m2m auth with ACS

Readme.md

@@ -2,14 +2,15 @@
 
 Welcome to the StackRox contributions repository. This repository stores a variety of configuration files, scripts, and samples related to the deployment and use of the [StackRox Kubernetes security platform](https://www.stackrox.io) and [Red Hat Advanced Cluster Security](https://www.redhat.com/en/technologies/cloud-computing/openshift/advanced-cluster-security-kubernetes).
 
-All code in this repo is provided as-is without warranty or support from Red Hat. 
+All code in this repo is provided as-is without warranty or support from Red Hat.
 
 Join the #stackrox channel on [CNCF Slack](https://cncf.slack.com/) for community discussion and support.
 
-We'd love your feedback! Please take care with any of the configurations in this repo before applying using these in your environment. 
+We'd love your feedback! Please take care with any of the configurations in this repo before applying using these in your environment.
 
 ## What's in this Repository
-* `ci/`  samples for using StackRox *roxctl* command-line tool in CI/CD pipelines
+* `ci/` samples for using StackRox *roxctl* command-line tool in CI/CD pipelines
 * `ingress/`  configurations for StackRox under popular Kubernetes ingress controllers
 * `completions/` shell auto-completions for roxctl
 * `util-scripts/` scripts using Stackrox API or roxctl for popular tasks (export to csv,...)
+* `guides/` instructions on how to configure ACS or integrate it with 3rd party services

guides/cloud-provider-integrations/azure-service-principal-m2m-auth.md

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+## Using Azure Entra ID service principals for machine to machine auth with ACS
+
+**Note:** Instructions provided in this guide are provided as-is without warranty or support from Red Hat.
+
+### 1. Create Azure service principal
+
+For this, we can use [the following guide from Microsoft Learn](https://learn.microsoft.com/en-us/entra/identity-platform/howto-create-service-principal-portal?source=recommendations#register-an-application-with-microsoft-entra-id-and-create-a-service-principal).
+
+The only step: “**Register an application with Microsoft Entra ID and create a service principal”** is required. We do not have to add roles for that service principal because it does not have to access any Azure resource. It will be used only for authentication in ACS.
+
+### 2. Setup authentication for created service principal
+
+This is required in order for the service principal to authenticate to Azure.
+
+We can use [the following steps from the same Microsoft Learn page](https://learn.microsoft.com/en-us/entra/identity-platform/howto-create-service-principal-portal?source=recommendations#set-up-authentication).
+
+After authentication setup, we can use the `az` command to log into Azure and retrieve the access token required to do m2m authentication to ACS.
+
+### 3. Login with `az`
+
+This example uses a secret to authenticate (**Option 3** in the “Setup authentication” guide mentioned under step 2.).
+
+```
+az login --service-principal \
+  --username <service principal Application (client) ID> \
+  --password <created secret Value field> \
+  --tenant <service principal Directory (tenant) ID> \
+  --allow-no-subscriptions
+```
+
+It is important to use the `--allow-no-subscriptions` flag if the service principal does not have any roles.
+
+**Note:** Logging as a regular user with `az login` would also work. In that case, the difference would be that we need to use `unique_name` or another claim from the token during the configuration of ACS machine access (Step 4\. below)
+
+After this, the command:
+
+```
+az account list --output yamlc
+```
+
+Should output account with `user` property. The name of that user should be the service principal ID.
+
+```
+  user:
+    name: <service principal Application (client) ID>
+    type: servicePrincipal
+```
+
+### 4. Configure ACS
+
+You can follow [Configuring short-lived access documentation on Red Hat documentation](https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_security_for_kubernetes/4.6/html/operating/managing-user-access#configure-short-lived-access). *Ensure to use documentation from used ACS version.*
+
+Create a **Machine access configuration** - with the following fields:
+
+Issuer: `https://sts.windows.net/<service principal Directory (tenant) ID>/`
+
+Add a rule with:
+Key: `appid`
+Value: `<service principal Application (client) ID>`
+
+**Important:** ACS has to be able to access: `https://sts.windows.net/<service principal Directory (tenant) ID>/.well-known/openid-configuration`
+
+### 5. Test everything
+
+Use the following `roxctl` command:
+
+```
+roxctl central machine-to-machine exchange \
+  --token="$(az account get-access-token --tenant "<service principal Directory (tenant) ID>" --query "accessToken" --output tsv)"
+```
+
+*If `--output tsv` does not provide valid token format. There is option to use JSON output and `jq` command to select token from payload.*
+
+After successful login, running: `roxctl central whoami` should output ACS authentication information. And “User name:” in the output should be the same as provided `<service principal Application (client) ID>` in the `az` login command.