Open Policy Agent (OPA) WebAssembly dotnet core SDK

This is SDK for using WebAssembly (wasm) compiled Open Policy Agent policies with dotnet core.

Initial implementation was based on Open Policy Agent WebAssemby NPM Module

For more information check out the guide.

Key Features

• Fast in-process OPA policies evaluation.
• Full ABI support.
• Additional OPA built-ins.
• Compilation.
• AspDotNet Core integration.

NuGet Packages

	Official	Preview
OpaDotNet.Wasm
OpaDotNet.Extensions.AspNetCore
OpaDotNet.Compilation.Cli		-
OpaDotNet.Compilation.Interop		-

Getting Started

Install nuget package

dotnet add package OpaDotNet.Wasm

Usage

To evaluate OPA policy you need to:

Load compiled policy

using using OpaDotNet.Wasm;

const string data = "{ \"world\": \"world\" }";

using var engine = OpaEvaluatorFactory.CreateFromWasm(
    File.OpenRead("policy.wasm")
    );

engine.SetDataFromRawJson(data);

Evaluate policy

IOpaEvaluator has several APIs for policy evaluation:

• EvaluatePredicate - Evaluates named policy with specified input. Response interpreted as simple true/false result.
• Evaluate - Evaluates named policy with specified input.
• EvaluateRaw - Evaluates named policy with specified raw JSON input.

var policyResult = engine.EvaluatePredicate(inp);

Check result

if (policyResult.Result)
{
    // We've been authorized.
}
else
{
    // Can't do that.
}

Writing policy

See writing policy

Compiling policy

You have several options to compile rego policy into wasm module:

package example

default hello = false

hello {
    x := input.message
    x == data.world
}

Manually

Either use the Compile REST API or opa build CLI tool.

For example, with OPA v0.20.5+:

opa build -t wasm -e example/hello example.rego

Which is compiling the example.rego policy file. The result will be an OPA bundle with the policy.wasm binary included. See ./samples for a more comprehensive example.

See opa build --help for more details.

With OpaDotNet.Compilation

You can use SDK to do compilation for you. For more information see OpaDotNet.Compilation.

OpaDotNet.Compilation.Cli

Important

You will need opa cli tool to be in your PATH or provide full path in RegoCliCompilerOptions.

dotnet add package OpaDotNet.Compilation.Cli

using OpaDotNet.Wasm;
using OpaDotNet.Compilation.Cli;

var compiler = new RegoCliCompiler();
var policyStream = await compiler.CompileFile("example.rego", new[] { "example/hello" });

// Use compiled policy.
using var engine = OpaEvaluatorFactory.CreateFromBundle(policyStream);

OpaDotNet.Compilation.Interop

dotnet add package OpaDotNet.Compilation.Interop

using OpaDotNet.Wasm;
using OpaDotNet.Compilation.Interop;

var compiler = new RegoInteropCompiler();
var policyStream = await compiler.CompileFile("example.rego", new[] { "example/hello" });

// Use compiled policy.
using var engine = OpaEvaluatorFactory.CreateFromBundle(policyStream);

3rd Party Libraries and Contributions

• OPA - An open source, general-purpose policy engine that unifies policy enforcement across the stack.
• Moq - The most popular and friendly mocking library for .NET.
• xUnit.net - Free, open source, community-focused unit testing tool for the .NET Framework.
• wasmtime-dotnet - .NET embedding of Wasmtime.
• IPNetwork2 - Utility classes take care of complex network, IPv4, IPv6, CIDR calculation for .NET developers.
• BenchmarkDotNet - Powerful .NET library for benchmarking.
• Semver - Implementation in .Net based on the v2.0.0 of the spec.
• json-everything - Set of libraries that ensure that common JSON functionality has good support in the System.Text.Json space.
• YamlDotNet - YamlDotNet is a YAML library for netstandard and other .NET runtimes.