OpaDotNet.Extensions.AspNetCore 3.0.3

Open Policy Agent (OPA) AspNetCore Extensions

This is AspNetCore specific extensions for OpaDotNet project.

Getting Started

Install nuget package

dotnet add package OpaDotNet.Extensions.AspNetCore

Usage

Add policy file ./Policy/policy.rego

package example

import future.keywords.if

# METADATA
# entrypoint: true
allow if {
    true
}

# METADATA
# entrypoint: true
deny if {
    false
}

The code:

using System.Security.Claims;
using System.Text.Encodings.Web;
using System.Text.Json;

using Microsoft.AspNetCore.Authentication;
using Microsoft.Extensions.Options;

using OpaDotNet.Extensions.AspNetCore;

var builder = WebApplication.CreateBuilder(args);

// Register core services.
builder.Services.AddOpaAuthorization(
    cfg =>
    {
        // Get policies from the file system.
        cfg.AddFileSystemPolicySource();

        // Configure.
        cfg.AddConfiguration(
            p =>
            {
                // Allow to pass all headers as policy query input.
                p.AllowedHeaders.Add(".*");

                // Path where look for rego policies.
                p.PolicyBundlePath = "./Policy";
                p.EngineOptions = new()
                {
                    SerializationOptions = new()
                    {
                        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
                    },
                };
            }
            );
    }
    );

// In real scenarios here will be more sophisticated authentication.
builder.Services.AddAuthentication()
    .AddScheme<AuthenticationSchemeOptions, NopAuthenticationSchemeHandler>(
        NopAuthenticationSchemeHandler.AuthenticationSchemeName,
        null
        );

builder.Services.AddAuthorization();

var app = builder.Build();

app.UseAuthentication();
app.UseAuthorization();

// Will evaluate example/allow rule and return 200.
app.MapGet("/allow", [OpaPolicyAuthorize("example", "allow")] () => "Hi!");

// Authorize attribute works too. Policy needs to be named 'Opa/{module}/{entrypoint}'.
app.MapGet("/allow2", [Authorize("Opa/example/allow")]() => "Hi!");

// Will evaluate example/deny rule and return 403.
app.MapGet("/deny", [OpaPolicyAuthorize("example", "deny")] () => "Should not be here!");

app.Run();


internal class NopAuthenticationSchemeHandler : AuthenticationHandler<AuthenticationSchemeOptions>
{
    public const string AuthenticationSchemeName = "Nop";

    public NopAuthenticationSchemeHandler(
        IOptionsMonitor<AuthenticationSchemeOptions> options,
        ILoggerFactory logger,
        UrlEncoder encoder,
        ISystemClock clock) : base(options, logger, encoder, clock)
    {
    }

    protected override Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        var principal = new ClaimsPrincipal();
        var ticket = new AuthenticationTicket(principal, AuthenticationSchemeName);
        var result = AuthenticateResult.Success(ticket);

        return Task.FromResult(result);
    }
}