@styra/opa

OPA Typescript SDK

The Styra-supported driver to connect to Open Policy Agent (OPA) and Enterprise OPA deployments.

The documentation for this SDK lives at https://docs.styra.com/sdk, with reference documentation available at https://styrainc.github.io/opa-typescript

You can use the Styra OPA SDK to connect to Open Policy Agent and Enterprise OPA deployments.

SDK Installation

NPM

npm add @styra/opa

PNPM

pnpm add @styra/opa

Bun

bun add @styra/opa

Yarn

yarn add @styra/opa zod

# Note that Yarn does not install peer dependencies automatically. You will need
# to install zod as shown above.

Summary

For more information about the API: Enterprise OPA documentation

Table of Contents

• SDK Installation
• Requirements
• SDK Example Usage
• Available Resources and Operations
• Standalone functions
• Retries
• Error Handling
• Server Selection
• Custom HTTP Client
• Authentication
• Debugging

Requirements

For supported JavaScript runtimes, please consult RUNTIMES.md.

SDK Example Usage (high-level)

All the code examples that follow assume that the high-level SDK module has been imported, and that an OPA instance was created:

import { OPAClient } from "@styra/opa";

const serverURL = "http://opa-host:8181";
const path = "authz/allow";
const opa = new OPAClient(serverURL);

Simple query

For a simple boolean response without input, use the SDK as follows:

const allowed = await opa.evaluate(path);
console.log(allowed ? "allowed!" : "denied!");

Note that allowed will be of type any. You can change that by providing type parameters to evaluate:

const allowed = await opa.evaluate<never, boolean>(path);

The first parameter is the type of input passed into evaluate; we don't have any in this example, so you can use anything for it (any, unknown, or never).

HTTP Request

POST /v1/data/authz/allow
Content-Type: application/json

{}

Input

Input is provided as a second (optional) argument to evaluate:

const input = { user: "alice" };
const allowed = await opa.evaluate(path, input);
console.log(allowed ? "allowed!" : "denied!");

For providing types, use

interface myInput {
  user: string;
}
const input: myInput = { user: "alice" };
const allowed = await opa.evaluate<myInput, boolean>(path, input);
console.log(allowed ? "allowed!" : "denied!");

HTTP Request

POST /v1/data/authz/allow
Content-Type: application/json

{ "input": { "user": "alice" } }

Result Types

When the result of the policy evaluation is more complex, you can pass its type to evaluate and get a typed result:

interface myInput {
  user: string;
}
interface myResult {
  authorized: boolean;
  details: string[];
}
const input: myInput = { user: "alice" };
const result = await opa.evaluate<myInput, myResult>(path, input);
console.log(result.evaluated ? "allowed!" : "denied!");

Input Transformations

If you pass in an arbitrary object as input, it'll be stringified (JSON.stringify):

class A {
  // With these names, JSON.stringify() returns the right thing.
  name: string;
  list: any[];

  constructor(name: string, list: any[]) {
    this.name = name;
    this.list = list;
  }
}
const inp = new A("alice", [1, 2, true]);
const allowed = await opa.evaluate<myInput, boolean>(path, inp);
console.log(allowed ? "allowed!" : "denied!");

You can control the input that's constructed from an object by implementing ToInput:

class A implements ToInput {
  // With these names, JSON.stringify() doesn't return the right thing.
  private n: string;
  private l: any[];

  constructor(name: string, list: any[]) {
    this.n = name;
    this.l = list;
  }

  toInput(): Input {
    return { name: this.n, list: this.l };
  }
}
const inp = new A("alice", [1, 2, true]);
const allowed = await opa.evaluate<myInput, boolean>(path, inp);
console.log(allowed ? "allowed!" : "denied!");

HTTP Request

POST /v1/data/authz/allow
Content-Type: application/json

{ "input": { "name": "alice", "list": [ 1, 2, true ] } }

Result Transformations

If the result format of the policy evaluation does not match what you want it to be, you can provide a third argument, a function that transforms the API result.

Assuming that the policy evaluates to

{
  "allowed": true,
  "details": ["property-a is OK", "property-B is OK"]
}

you can turn it into a boolean result like this:

const allowed = await opa.evaluate<any, boolean>(path, undefined, {
  fromResult: (r?: Result) => (r as Record<string, any>)["allowed"] ?? false,
});
console.log(allowed ? "allowed!" : "denied!");

Example Projects

Express

In the StyraInc/styra-demo-tickethub repository, you'll find a NodeJS backend service that is using @styra/opa:

router.get("/tickets/:id", [param("id").isInt().toInt()], async (req, res) => {
  const {
    params: { id },
  } = req;
  await authz.evaluated(path, { action: "get", id }, req);

  const ticket = await prisma.tickets.findUniqueOrThrow({
    where: { id },
    ...includeCustomers,
  });
  return res.status(OK).json(toTicket(ticket));
});

NestJS

In StyraInc/opa-typescript-example-nestjs, we have an decorator-based API authorization example using @styra/opa:

@Controller("cats")
@AuthzQuery("cats/allow")
@AuthzStatic({ resource: "cat" })
export class CatsController {
  constructor(private catsService: CatsService) {}

  @Post()
  @Authz(({ body: { name } }) => ({ name, action: "create" }))
  async create(@Body() createCatDto: CreateCatDto) {
    this.catsService.create(createCatDto);
  }

  @Get(":name")
  @AuthzQuery("cats") // For illustration, we're querying the package extent
  @Decision((r) => r.allow)
  @Authz(({ params: { name } }) => ({
    name,
    action: "get",
  }))
  async findByName(@Param("name") name: string): Promise<Cat> {
    return this.catsService.findByName(name);
  }
}

Please refer to the repository's README.md for more details.

Note: For low-level SDK usage, see the sections below.

---

OPA OpenAPI SDK (low-level)

Available Resources and Operations

Available methods

OpaApiClient SDK

• executeDefaultPolicyWithInput - Execute the default decision given an input
• executePolicy - Execute a policy
• executePolicyWithInput - Execute a policy given an input
• executeBatchPolicyWithInput - Execute a policy given a batch of inputs
• health - Verify the server is operational

Retries

Some of the endpoints in this SDK support retries. If you use the SDK without any configuration, it will fall back to the default retry strategy provided by the API. However, the default retry strategy can be overridden on a per-operation basis, or across the entire SDK.

To change the default retry strategy for a single API call, simply provide a retryConfig object to the call:

import { OpaApiClient } from "@styra/opa";

const opaApiClient = new OpaApiClient();

async function run() {
  const result = await opaApiClient.executeDefaultPolicyWithInput("8203.11", {
    retries: {
      strategy: "backoff",
      backoff: {
        initialInterval: 1,
        maxInterval: 50,
        exponent: 1.1,
        maxElapsedTime: 100,
      },
      retryConnectionErrors: false,
    },
  });

  // Handle the result
  console.log(result);
}

run();

If you'd like to override the default retry strategy for all operations that support retries, you can provide a retryConfig at SDK initialization:

import { OpaApiClient } from "@styra/opa";

const opaApiClient = new OpaApiClient({
  retryConfig: {
    strategy: "backoff",
    backoff: {
      initialInterval: 1,
      maxInterval: 50,
      exponent: 1.1,
      maxElapsedTime: 100,
    },
    retryConnectionErrors: false,
  },
});

async function run() {
  const result = await opaApiClient.executeDefaultPolicyWithInput("8203.11");

  // Handle the result
  console.log(result);
}

run();

Authentication

Per-Client Security Schemes

This SDK supports the following security scheme globally:

Name	Type	Scheme
bearerAuth	http	HTTP Bearer

To authenticate with the API the bearerAuth parameter must be set when initializing the SDK client instance. For example:

import { OpaApiClient } from "@styra/opa";

const opaApiClient = new OpaApiClient({
  bearerAuth: "<YOUR_BEARER_TOKEN_HERE>",
});

async function run() {
  const result = await opaApiClient.executeDefaultPolicyWithInput("8203.11");

  // Handle the result
  console.log(result);
}

run();

Debugging

You can setup your SDK to emit debug logs for SDK requests and responses.

You can pass a logger that matches console's interface as an SDK option.

[!WARNING] Beware that debug logging will reveal secrets, like API tokens in headers, in log messages printed to a console or files. It's recommended to use this feature only during local development and not in production.

import { OpaApiClient } from "@styra/opa";

const sdk = new OpaApiClient({ debugLogger: console });

Standalone functions

All the methods listed above are available as standalone functions. These functions are ideal for use in applications running in the browser, serverless runtimes or other environments where application bundle size is a primary concern. When using a bundler to build your application, all unused functionality will be either excluded from the final bundle or tree-shaken away.

To read more about standalone functions, check FUNCTIONS.md.

Available standalone functions

• executeBatchPolicyWithInput
• executeDefaultPolicyWithInput
• executePolicyWithInput
• executePolicy
• health

Community

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