--- /dev/null
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. SPDX-License-Identifier: CC-BY-4.0
+.. Copyright (C) 2023 Nordix
+
+#################################
+Security Architecture Prototyping
+#################################
+
+************
+Introduction
+************
+The O-RAN (Open Radio Access Network) security architecture is a framework for securing the communication between different
+components of an open system. It is designed to ensure the confidentiality, integrity, and availability of data and services,
+while also providing protection against potential security threats.
+This involves securing the communication between different components, including encryption, authentication, and access control.
+The O-RAN security architecture is designed to be flexible, scalable, and interoperable, enabling different vendors to integrate their solutions into the O-RAN ecosystem while maintaining security.
+
+Here are some key features provided by the platform:
+
+* MTLS provides secure encrypted communication and mutual authentication of peers.
+* Users are authenticated using a client via the OpenID Connect (OIDC) protocol.
+* OAuth 2.0 is a framework that controls authorization for access of services.
+
+Apps (rApps) need to use Service Management & Orchestration (SMO) services and provide services to other Apps.
+Apps & SMO services may be multivendor.
+The goal of the Security Architecture is to provide selective & controlled exposure of these services.
+
+* Ensure that services cannot be accessed without a valid token.
+* Ensure that inter-services communication is done using mTLS.
+* Ensure the automated setup and configuration of security prior to app deployment.
+
+This product is a part of :doc:`NONRTRIC <../index>`.
+
+**********
+Components
+**********
+
+======
+Istio
+======
+App security relies on Istio service mesh to enforce mTLS between applications.
+The applications running in the cluster are not required to implement mTLS,
+instead this is done by attaching an Istio sidecar to the running containers.
+mTLS communication is done between the sidecars.
+
+
+.. image:: ./se-service-mesh-architecture.png
+ :width: 1000pt
+
+========
+Keycloak
+========
+Keycloak is an open-source identity and access management tool.
+It is used to issue access tokens to the apps.
+The access token comes in the form of a JWT which includes claims or fields which are used to determine the access level to grant to a particular app.
+
+ * Access tokens (JWT) are retrieved using Keycloak clients.
+ * Access token has limited lifetime (needs to be refreshed).
+ * Access token is sent in the HTTP header is each REST call.
+
+This is an example of a JWT payload:
+
+.. code-block:: javascript
+
+ {
+ "exp": 1683628065,
+ "iat": 1683627765,
+ "jti": "b61ae49d-5a73-4e91-96f2-de3b400a5779",
+ "iss": "https://keycloak:8443/realms/demo",
+ "sub": "e7709f80-61bd-4440-a265-d51c4fed8ece",
+ "typ": "Bearer",
+ "azp": "demoprovider-cli",
+ "session_state": "89ac7390-2865-4e07-bd1a-aea43c43827a",
+ "scope": "email",
+ "sid": "89ac7390-2865-4e07-bd1a-aea43c43827a",
+ "clientHost": "127.0.0.6",
+ "clientId": "demoprovider-cli",
+ "email_verified": false,
+ "clientRole": [
+ "provider-viewer"
+ ],
+ "clientAddress": "127.0.0.6"
+ }
+
+.. image:: ./se-istio-authorization.png
+ :width: 1000pt
+
+========
+Postgres
+========
+Postgres is used as the back-end database for Keycloak, it will persistent the Keycloak objects that have been created.
+
+============
+Cert Manager
+============
+Cert Manager is used to provide both server and client certificates for Keycloak.
+It also provides certificates for the webhook server.
+
+============
+Chart Museum
+============
+Chart museum is used to stores the Helm charts for the apps.
+
+==============
+Helm Installer
+==============
+Helm installer is used to automate the installation of the Helm charts.
+Each chart contains an app configuration section in the values.yaml file which is used by Istio manager and Keycloak manager.
+
+==============
+Istio Manager
+==============
+Istio manager is used to automate the setup of Gateways, Virtual Services, Authorization Policies
+and Request Authentication polices for the apps.
+The exact configuration required is read from the values.yaml file in the Helm chart.
+
+================
+Keycloak Manager
+================
+Keycloak manager is used to automate the setup of realms, clients, users, role mappings and authentication flows.
+Keycloak provides REST API endpoints for creating and deleting these objects.
+The exact configuration required is read from the values.yaml file in the Helm chart.
+
+====================
+JWT Proxy Controller
+====================
+The Jwt Proxy Admission Controller determines whether to attach a jwt proxy sidecar to the app container based on the app label.
+If permitted the exact configuration required is read from the values.yaml file in the Helm chart.
+
+.. image:: ./se-jwt-proxy.png
+ :width: 1000pt
+
+
+************
+Request Flow
+************
+
+.. image:: ./se-request-flow.png
+ :width: 1000pt
+
+============
+Provider App
+============
+When a provider app is installed using Helm manager, all the necessary security is automatically setup prior to deployment.
+
+Helm manager calls Istio manager and sets up the following Istio services:
+ * Gateway: a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections.
+ * VirtualService: routes request from the gateway to the app.
+ * RequestAuthentication: verifies the issuer and jwksUri of the JWT.
+ * AuthorizationPolicy: authorizes incoming requests based on claims in the JWT.
+
+Helm manager calls Keycloak manager and sets up the following Keycloak objects:
+ * Realm : represents a set of users, credentials, roles, groups and clients. Realms can be used to isolated different apps from each other.
+ * Client: used to authenticate a user and retrieve a JWT.
+ * Role Mapper: maps the user role(s) to the token. These role(s) are used during app authorization.
+
+Clients support 4 authenticator types:
+ #. Client Secret
+ #. x509 certificate
+ #. JWT signed with certificate
+ #. JWT signed with secret
+
+Depending on the app configuration it will either setup an x509 client, a jwt client or a secret client.
+
+.. note:: If the app is configured to use the x509 authenticator, a direct flow grant for x509 is also setup to check fields in x509 certificate against some pre-defined value(s).
+
+===========
+Invoker App
+===========
+When an invoker app is installed using Helm manager,
+the app label is used to determine whether to inject the deployment with a jwt proxy sidecar.
+If the app label has been whitelisted the proxy is added to the container.
+The jwt proxy sidecar will automatically retrieve the token required to access the app provider and include it in the request header.
+
+.. image:: ./se-app-invoker-flow.png
+ :width: 1000pt
+
+This is an example of a provider and invoker running in a cluster:
+
+.. image:: ./se-rapp-jwt.png
+ :width: 1000pt
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