Getting Started with DPoP

This guide walks you through enabling DPoP (Demonstration of Proof-of-Possession) support in your Auth0-protected ASP.NET Core API.

Prerequisites

Before enabling DPoP, ensure you have:

  • ✅ An Auth0 account with DPoP enabled (contact Auth0 support if needed)
  • ✅ An API configured in Auth0 with DPoP support
  • ✅ The Auth0 ASP.NET Core API Authentication library installed
  • ✅ Basic Auth0 authentication already configured (see Getting Started)

Quick Start

Step 1: Enable DPoP with Default Settings

Add .WithDPoP() to your authentication configuration:

using Auth0.AspNetCore.Authentication.Api;
using Microsoft.AspNetCore.Authentication.JwtBearer;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAuth0ApiAuthentication(options =>
{
    options.Domain = builder.Configuration["Auth0:Domain"];
    options.JwtBearerOptions = new JwtBearerOptions()
    {
        Audience = builder.Configuration["Auth0:Audience"]
    };
}).WithDPoP(); // ✨ Enable DPoP with default settings

builder.Services.AddAuthorization();
builder.Services.AddControllers();

var app = builder.Build();

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

app.Run();

That's it! Your API now supports DPoP validation with sensible defaults.

Step 2: Configure Auth0

Ensure your Auth0 API is configured to issue DPoP-bound tokens. Follow the Auth0 DPoP configuration guide to set up DPoP for your API and clients.

Note: DPoP requires Auth0 tenant configuration. Contact Auth0 support if you don't see DPoP options.

Step 3: Test Your API

With DPoP (will succeed)

curl -X GET https://localhost:5001/api/protected \
  -H "Authorization: DPoP <dpop-bound-access-token>" \
  -H "DPoP: <dpop-proof-token>"

Without DPoP (will also succeed with default Allowed mode)

curl -X GET https://localhost:5001/api/protected \
  -H "Authorization: Bearer <regular-access-token>"

DPoP Modes Explained

Allowed Mode (Default)

.WithDPoP(options =>
{
    options.Mode = DPoPModes.Allowed;
});

Behavior:

  • ✅ Accepts DPoP-bound tokens with valid proofs
  • ✅ Also accepts standard Bearer tokens
  • 🔍 Validates DPoP when the DPoP header is present

Required Mode

.WithDPoP(options =>
{
    options.Mode = DPoPModes.Required;
});

Behavior:

  • ✅ Only accepts DPoP-bound tokens with valid proofs
  • ❌ Rejects standard Bearer tokens
  • ❌ Rejects requests without the DPoP header

Disabled Mode

.WithDPoP(options =>
{
    options.Mode = DPoPModes.Disabled;
});

Behavior:

  • ✅ Only standard JWT Bearer authentication
  • ❌ No DPoP validation performed
  • 🚫 DPoP headers are ignored

Common Configuration Examples

Example 1: Allowed Mode

Start with Allowed mode to test DPoP without breaking existing clients:

builder.Services.AddAuth0ApiAuthentication(options =>
{
    options.Domain = builder.Configuration["Auth0:Domain"];
    options.JwtBearerOptions = new JwtBearerOptions()
    {
        Audience = builder.Configuration["Auth0:Audience"]
    };
}).WithDPoP(options =>
{
    options.Mode = DPoPModes.Allowed;
    options.Leeway = 30; // 30 seconds tolerance
    options.IatOffset = 300; // 5 minutes max age
});

Example 2: Required Mode

Enforce DPoP for all requests:

builder.Services.AddAuth0ApiAuthentication(options =>
{
    options.Domain = builder.Configuration["Auth0:Domain"];
    options.JwtBearerOptions = new JwtBearerOptions()
    {
        Audience = builder.Configuration["Auth0:Audience"]
    };
}).WithDPoP(options =>
{
    options.Mode = DPoPModes.Required;
    options.Leeway = 10; // Tighter timing
    options.IatOffset = 120; // 2 minutes max age
});

Example 3: Custom Authentication Scheme

Use a custom scheme name:

builder.Services
    .AddAuthentication("MyCustomScheme")
    .AddAuth0ApiAuthentication("MyCustomScheme", options =>
    {
        options.Domain = builder.Configuration["Auth0:Domain"];
        options.JwtBearerOptions = new JwtBearerOptions()
        {
            Audience = builder.Configuration["Auth0:Audience"]
        };
    })
    .WithDPoP("MyCustomScheme", options =>
    {
        options.Mode = DPoPModes.Allowed;
    });

Protecting Endpoints

Once DPoP is enabled, protect your endpoints as usual:

Using Minimal APIs

app.MapGet("/api/public", () => 
    Results.Ok("Public endpoint - no authentication required"));

app.MapGet("/api/protected", () => 
    Results.Ok("Protected endpoint - authentication required"))
    .RequireAuthorization();

Using Controllers

[ApiController]
[Route("api/[controller]")]
public class DataController : ControllerBase
{
    [HttpGet("public")]
    public IActionResult Public()
    {
        return Ok("Public endpoint");
    }

    [Authorize]
    [HttpGet("protected")]
    public IActionResult Protected()
    {
        return Ok("Protected endpoint");
    }
}

Accessing Claims

DPoP validation is transparent - access claims normally:

[Authorize]
[HttpGet("user-info")]
public IActionResult GetUserInfo()
{
    var userId = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
    var email = User.FindFirst(ClaimTypes.Email)?.Value;
    
    return Ok(new { userId, email });
}

Troubleshooting

DPoP Validation Fails

Problem: Requests with DPoP header are rejected

Solutions:

  1. Check that Auth0 issued a DPoP-bound token (look for cnf claim)
  2. Verify the DPoP proof is properly formed
  3. Ensure htm (HTTP method) and htu (HTTP URI) match exactly
  4. Check time synchronization - iat must be recent

Bearer Tokens Rejected in Required Mode

Problem: Standard bearer tokens return 401

Solution: This is expected behavior in Required mode. Either:

  • Switch to DPoPModes.Allowed to support both
  • Update clients to send DPoP proofs

Time Validation Errors

Problem: Valid-looking DPoP proofs are rejected due to timing

Solutions:

  1. Increase IatOffset to allow older proofs
  2. Increase Leeway for clock skew tolerance
  3. Ensure client and server clocks are synchronized
.WithDPoP(options =>
{
    options.IatOffset = 600; // 10 minutes
    options.Leeway = 60; // 1 minute leeway
});

Error Responses

Invalid DPoP Proof

HTTP/1.1 401 Unauthorized
WWW-Authenticate: DPoP error="invalid_dpop_proof", 
                  error_description="DPoP proof validation failed"

Missing DPoP Proof (Required Mode)

HTTP/1.1 401 Unauthorized  
WWW-Authenticate: DPoP error="invalid_request",
                  error_description="DPoP proof is missing"

Invalid Token

HTTP/1.1 401 Unauthorized
WWW-Authenticate: DPoP error="invalid_token",
                  error_description="The cnf (confirmation) claim is missing or invalid"

Next Steps

Additional Resources

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