opa-express-middleware

Abstract

build.security provides simple development and management for your organization’s authorization policy.
opa-express-middleware is a Node.js Express middleware intended for performing authorization requests against build.security PDP(Policy Decision Point)/OPA.

Data Flow

Usage

Before you start we recommend completing the onboarding tutorial.

---

Important note

To simplify the setup process, the following example uses a local build.security PDP instance.
If you are already familiar with how to run your PDP, You can also run a pdp on you environment (Dev/Prod, etc).

In that case, don’t forget to change the hostname and the port in your code.

---

Simple usage

const express = require('express');
const bodyParser = require('body-parser');
const extAuthz = require('@build-security/opa-express-middleware');
const port = 3000;

const app = express();

const extAuthzMiddleware = extAuthz.authorize((req) => ({
    port: 8181,
    hostname: 'http://localhost',
    policyPath: '/authz/allow',
}));


app.use(bodyParser.json(), extAuthzMiddleware);

app.listen(port, () => {
  console.log(`Now listening on http://localhost:${port}`)
});

Mandatory configuration

1. hostname: The hostname of the Policy Decision Point (PDP)
2. port: The port at which the OPA service is running
3. policyPath: Full path to the policy (including the rule) that decides whether requests should be authorized

Optional configuration

1. allowOnFailure: Boolean. “Fail open” mechanism to allow access to the API in case the policy engine is not reachable. Default is false.
2. includeBody: Boolean. Whether or not to pass the request body to the policy engine. Default is true.
3. includeHeaders: Boolean. Whether or not to pass the request headers to the policy engine. Default is true
4. timeout: Integer. Amount of time to wait before request is abandoned and request is declared as failed. Default is 1000ms.
5. enable: Boolean. Whether or not to consult with the policy engine for the specific request. Default is true
6. enrich: Object. An object to attach to the request that is being sent to the policy engine. Default is an empty object {}

Advanced example

The following example will:

• consult with the policy engine only for GET requests
• add a field named “serviceId” with the value 1 to the request
• provide route parameters to the PDP as input. (For this to work, the middleware can’t be applied globally using app.use)
• an endpoint can declare the required permission the client needs in order to access it

const express = require('express');
const bodyParser = require('body-parser');
const extAuthz = require('@build-security/opa-express-middleware');

const app = express();

const extAuthzMiddleware = extAuthz.authorize((req) => ({
    port: 8181,
    hostname: 'http://localhost',
    policyPath: '/authz/allow',
    enable: req.method === "GET",
    enrich: { serviceId: 1 }
}));

app.use(bodyParser.json());

app.get('/region/:region/users/:userId', extAuthz.permissions('user.read'), extAuthzMiddleware, (req, res) => {
    res.send('allowed');
});

PDP Request example

This is what the input received by the PDP would look like.

{
   "input":{
      "request":{
         "method":"GET",
         "query":{
            
         },
         "path":"/region/israel/users/buildsec",
         "scheme":"http",
         "host":"localhost",
         "body":{
            
         },
         "headers":{
            "host":"localhost:3000",
            "user-agent":"curl/7.64.1",
            "accept":"*/*"
         }
      },
      "source":{
         "port":56038,
         "ipAddress":"::1"
      },
      "destination":{
         "port":3000,
         "ipAddress":"::1"
      },
      "resources":{
         "attributes":{
            "region":"1",
            "userId":"2"
         },
         "permissions":[
            "user.read"
         ]
      },
      "serviceId":1
   }
}

If everything works well you should receive the following response:

{
    "decision_id":"ef414180-05bd-4817-9634-7d1537d5a657",
    "result":true
}