Add Envoy Proxy integration documentation for Permit.io

docs/integrations/gateways/envoy.mdx

@@ -0,0 +1,246 @@
+---
+sidebar_position: 4
+title: Envoy Proxy x Permit
+---
+
+## Overview
+
+This guide explains how to integrate Envoy's External Authorization (ext_authz) filter with a Permit.io PDP using **GitOps-managed custom Rego policies**.
+With this setup, Envoy acts as a gateway that filters application requests by calling the PDP, which evaluates your Permit policies and returns an allow/deny decision.
+
+URL Mapping (`POST /allowed_url` on the PDP HTTP API) is a separate path. It is not used by the Envoy ext_authz gRPC integration described here — the entrypoint policy must map the request to a Permit resource and action itself.
+
+---
+
+## Prerequisites
+
+- **Envoy** deployed with the [External Authorization filter](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/ext_authz_filter) available
+- **Permit.io account** and project with a running PDP
+- **PDP version** **0.9.10 or higher** (required for this integration)
+- **GitOps flow** configured for your Permit environment (see below)
+- Basic familiarity with Envoy configuration and OPA/Rego
+
+---
+
+## 1. Configure GitOps for Custom Policies
+
+Use Permit GitOps to manage your PDP policies (including the Envoy entrypoint) in a Git repository.
+
+1. **Configure GitOps** for your environment (choose one of the following):
+   - **Using the CLI**: follow the CLI GitOps guide: [Custom Rego (OPA) and GitOps CLI](/how-to/permit-cli/permit-cli-gitops).
+   - **Using the manual flow**: follow the GitOps integration guide: [Git and Permit](/integrations/gitops/github).
+2. **Clone the GitOps repository** locally and check out the branch for the environment you want Envoy to protect.
+
+Once GitOps is configured, any changes you push to the repository will be synced to the PDP.
+
+---
+
+## 2. Add an Envoy entrypoint policy under `custom`
+
+In your GitOps repository:
+
+1. **Create a new Rego file** under the `custom` directory at the root of the GitOps repo, for example:
+
+   ```text
+   custom/envoy_entrypoint.rego
+   ```
+
+2. Define an entrypoint rule that Envoy's ext_authz integration will call.
+   The PDP OPA plugin will evaluate the data document at the path you configure (see the `PDP_OPA_PLUGINS` section below).
+
+   Put the policy in the `permit.custom` namespace used by other custom GitOps files, and derive a Permit resource **key** from the path (Permit resource keys cannot contain `/`):
+
+   ```rego
+   package permit.custom.envoy
+
+   import data.permit.root as check
+   import input.attributes.request.http as http_request
+
+   # Boolean entrypoint evaluated by the Envoy ext_authz gRPC plugin
+   default envoy = false
+
+   envoy {
+     method := http_request.method
+
+     # First path segment is the resource key: /documents/123 -> "documents"
+     # This key must match a resource configured in Permit.
+     segments := split(trim_prefix(http_request.path, "/"), "/")
+     resource_key := segments[0]
+
+     # Example user & tenant extraction (adapt to your authentication setup)
+     user_key := http_request.headers["x-user-id"]
+     tenant_key := http_request.headers["x-tenant-id"]
+
+     check_input := {
+       "user": {
+         "key": user_key,
+       },
+       "action": method,
+       "resource": {
+         "type": resource_key,
+         "tenant": tenant_key,
+       },
+     }
+
+     # Call "permit.check"
+     check.allow with input as check_input
+   }
+   ```
+
+   This boolean entrypoint is enough for Envoy to allow or deny the request. The Audit Log **Decision** column is filled from the boolean result. To also fill **user**, **action**, **resource**, and **tenant**, return an object that includes `permitio_metadata` — see [Ingest Envoy decisions into Permit Audit Logs](#5-ingest-envoy-decisions-into-permit-audit-logs).
+
+3. Commit and **push** the new file to the GitOps repository.
+4. Wait for the PDP to sync the updated policies (or trigger a sync if you are using a CI flow).
+
+For the full structure of the Envoy authorization input (`input`) used in your policy, see the official
+[Envoy ext_authz filter documentation](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/ext_authz_filter).
+
+---
+
+## 3. Configure the PDP OPA plugins
+
+The PDP **must** be started with an `envoy_ext_authz_grpc` plugin that exposes the Envoy-compatible gRPC service and points it at your custom policy entrypoint.
+
+Set the **`PDP_OPA_PLUGINS`** environment variable when running the PDP:
+
+```bash
+export PDP_OPA_PLUGINS='{"permit_graph":{},"envoy_ext_authz_grpc":{"addr":":9191","path":"permit/custom/envoy"}}'
+```
+
+- **`permit_graph`** is required for Permit to function correctly.
+- **`envoy_ext_authz_grpc`** enables the Envoy gRPC external authorization endpoint.
+- **`addr`** is the address/port on which the gRPC server will listen (e.g. `:9191`).
+- **`path`** must match the OPA data path of your Envoy entrypoint policy (in the example above, `data.permit.custom.envoy`).
+
+The gRPC listener also has to be reachable from Envoy. The PDP image does not expose port `9191` by default:
+
+- **Docker:** add `-p 9191:9191` to the `docker run` command (or a `ports` entry in Compose).
+- **Helm:** add the port to the PDP Service via `pdp.additionalPorts`:
+
+  ```yaml
+  pdp:
+    additionalPorts:
+      - name: grpc
+        port: 9191
+        targetPort: 9191
+  ```
+
+For more advanced plugin and Envoy integration options (timeouts, metadata, headers, etc.), see the OPA Envoy plugin configuration docs: [OPA Envoy Integration Configuration](https://www.openpolicyagent.org/docs/latest/envoy/#configuration).
+
+Ensure this variable is set alongside your usual PDP configuration (such as `PDP_API_KEY`, `PDP_DEBUG`, etc.).
+
+---
+
+## 4. Configure Envoy to call the PDP
+
+In your Envoy configuration, add the **HTTP ext_authz filter** and point it to the PDP gRPC endpoint configured above.
+
+A minimal example (simplified) might look like this:
+
+```yaml
+http_filters:
+  - name: envoy.filters.http.ext_authz
+    typed_config:
+      "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz
+      transport_api_version: V3
+      grpc_service:
+        envoy_grpc:
+          cluster_name: permit_pdp_ext_authz
+        timeout: 0.5s
+
+clusters:
+  - name: permit_pdp_ext_authz
+    type: logical_dns
+    connect_timeout: 0.25s
+    lb_policy: round_robin
+    http2_protocol_options: {}
+    load_assignment:
+      cluster_name: permit_pdp_ext_authz
+      endpoints:
+        - lb_endpoints:
+            - endpoint:
+                address:
+                  socket_address:
+                    address: pdp
+                    port_value: 9191
+```
+
+`http2_protocol_options` is required so the cluster speaks HTTP/2, which gRPC needs. Without it, the upstream defaults to HTTP/1.1 and ext_authz calls to the PDP can fail.
+
+Adjust the cluster name, address, and port to match your environment.
+Consult the [Envoy ext_authz docs](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/ext_authz_filter)
+for the full configuration options.
+
+---
+
+## 5. Ingest Envoy decisions into Permit Audit Logs
+
+Envoy's ext_authz input is **not** a `permit.check` payload. The PDP records a decision log for the Envoy query (`permit/custom/envoy`) and fills the **Decision** column from the boolean result, but the Audit Log page cannot fill **user**, **action**, **resource**, or **tenant** from that Envoy-shaped input.
+
+To map those columns, include a `permitio_metadata` object on the **policy result**, using the same structure as [`permit.check()`](/how-to/enforce-permissions/check). Permit reads this object as a fallback when the query input is not a standard check.
+
+Return an object from the Envoy entrypoint (the OPA Envoy plugin uses the `allowed` field for allow/deny). Put `permitio_metadata` on the **default** as well — otherwise default-denied requests (missing headers, unparseable path) produce an empty audit row and are dropped:
+
+```rego
+package permit.custom.envoy
+
+import data.permit.root as check
+import input.attributes.request.http as http_request
+
+default envoy := {
+  "allowed": false,
+  "permitio_metadata": {"allow": false},
+}
+
+envoy := {
+  "allowed": allowed,
+  "permitio_metadata": {
+    "allow": allowed,
+    "user": {"key": user_key},
+    "action": method,
+    "resource": {
+      "type": resource_key,
+      "tenant": tenant_key,
+    },
+  },
+} {
+  method := http_request.method
+  segments := split(trim_prefix(http_request.path, "/"), "/")
+  resource_key := segments[0]
+  user_key := http_request.headers["x-user-id"]
+  tenant_key := http_request.headers["x-tenant-id"]
+
+  check_input := {
+    "user": {"key": user_key},
+    "action": method,
+    "resource": {
+      "type": resource_key,
+      "tenant": tenant_key,
+    },
+  }
+
+  allowed := check.allow with input as check_input
+}
+```
+
+`permitio_metadata` supports the following fields (all optional; omit any you do not have):
+
+| Field | Audit Log column |
+| --- | --- |
+| `allow` | Decision (allow / deny) |
+| `user.key` | User |
+| `user.email` | User email |
+| `user.first_name` / `user.last_name` | User display name |
+| `action` | Action |
+| `resource.type` | Resource |
+| `resource.tenant` | Tenant |
+
+If the query input already has a standard `permit.check` field (for example `input.user.key`), that value wins. `permitio_metadata` is only used when the corresponding input field is missing.
+
+:::note
+Keep the OPA path under the `permit/` prefix (for example `permit/custom/envoy`). Decision logs whose query path does not start with `permit/` are not ingested into the Audit Log.
+:::
+
+After traffic hits Envoy, open the [Audit Log](https://app.permit.io/audit-log) and use the **All** query type. Envoy evaluations are not `permit.check` queries, so they will not appear if you filter to Check only. Missing columns in the table mean that field was not present on `permitio_metadata`.
+
+For how to read and filter logs, see [Audit Types & Filtering](/how-to/use-audit-logs/types-and-filtering).

sidebars.js

@@ -675,6 +675,7 @@ const sidebars = {
             "integrations/gateways/aws-api-gateway",
             "integrations/gateways/kong",
             "integrations/gateways/nginx",
+            "integrations/gateways/envoy",
           ],
         },
         {