Work in progress on fix for DPoP nonces received from the AS

samples/Web/Program.cs

@@ -14,6 +14,8 @@
 
 Log.Information("Host.Main Starting up");
 
+Console.Title = "Web (Sample)";
+
 try
 {
     var builder = WebApplication.CreateBuilder(args);

src/Duende.AccessTokenManagement.OpenIdConnect/AuthorizationServerDPoPHandler.cs

@@ -0,0 +1,149 @@
+// Copyright (c) Brock Allen & Dominick Baier. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Duende.AccessTokenManagement.OpenIdConnect;
+
+/// <summary>
+/// Delegating handler that adds behavior needed for DPoP to the backchannel
+/// http client of the OIDC authentication handler.
+///
+/// This handler has two main jobs:
+///
+/// 1. Store new nonces from successful responses from the authorization server.
+///
+/// 2. Attach proof tokens to token requests in the code flow. 
+///
+///    On the authorize request, we will have sent a dpop_jkt parameter with a
+///    key thumbprint. The AS expects that we will use the corresponding key to
+///    create our proof, and we track that key in the http context. This handler
+///    retrieves that key and uses it to create proof tokens for use in the code
+///    flow. 
+///
+///    Additionally, the token endpoint might respond to a token exchange
+///    request with a request to retry with a nonce that it supplies via http
+///    header. When it does, this handler retries those code exchange requests.
+///
+/// </summary>
+internal class AuthorizationServerDPoPHandler : DelegatingHandler
+{
+    private readonly IDPoPProofService _dPoPProofService;
+    private readonly IDPoPNonceStore _dPoPNonceStore;
+    private readonly IHttpContextAccessor _httpContextAccessor;
+    private readonly ILogger<AuthorizationServerDPoPHandler> _logger;
+
+    internal AuthorizationServerDPoPHandler(
+        IDPoPProofService dPoPProofService,
+        IDPoPNonceStore dPoPNonceStore,
+        IHttpContextAccessor httpContextAccessor,
+        ILoggerFactory loggerFactory)
+    {
+        _dPoPProofService = dPoPProofService;
+        _dPoPNonceStore = dPoPNonceStore;
+        _httpContextAccessor = httpContextAccessor;
+        // We depend on the logger factory, rather than the logger itself, since
+        // the type parameter of the logger (referencing this class) will not
+        // always be accessible.
+        _logger = loggerFactory.CreateLogger<AuthorizationServerDPoPHandler>();
+    }
+
+    /// <inheritdoc/>
+    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+    {
+        var codeExchangeJwk = _httpContextAccessor.HttpContext?.GetCodeExchangeDPoPKey();
+        if (codeExchangeJwk != null)
+        {
+            await SetDPoPProofTokenForCodeExchangeAsync(request, jwk: codeExchangeJwk).ConfigureAwait(false);
+        }
+
+        var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
+
+        // The authorization server might send us a new nonce on either a success or failure
+        var dPoPNonce = response.GetDPoPNonce();
+
+        if (dPoPNonce != null)
+        {
+            // This handler contains specialized logic to create the new proof
+            // token using the proof key that was associated with a code flow
+            // using a dpop_jkt parameter on the authorize call. Other flows
+            // (such as refresh), are separately responsible for retrying with a
+            // server-issued nonce. So, we ONLY do the retry logic when we have
+            // the dpop_jkt's jwk
+            if (codeExchangeJwk != null)
+            {
+                // If the http response code indicates a bad request, we can infer
+                // that we should retry with the new nonce. 
+                //
+                // The server should have also set the error: use_dpop_nonce, but
+                // there's no need to incur the cost of parsing the json and
+                // checking for that, as we would only receive the nonce http header
+                // when that error was set. Authorization servers might preemptively
+                // send a new nonce, but the spec specifically says to do that on a
+                // success (and we handle that case in the else block). 
+                //
+                // TL;DR - presence of nonce and 400 response code is enough to
+                // trigger a retry during code exchange
+                if (response.StatusCode == HttpStatusCode.BadRequest)
+                {
+                    _logger.LogDebug("Token request failed with DPoP nonce error. Retrying with new nonce.");
+                    response.Dispose();
+                    await SetDPoPProofTokenForCodeExchangeAsync(request, dPoPNonce, codeExchangeJwk).ConfigureAwait(false);
+                    return await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            if (response.StatusCode == HttpStatusCode.OK)
+            {
+                _logger.LogDebug("The authorization server has supplied a new nonce on a successful response, which will be stored and used in future requests to the authorization server");
+
+                await _dPoPNonceStore.StoreNonceAsync(new DPoPNonceContext
+                {
+                    Url = request.GetDPoPUrl(),
+                    Method = request.Method.ToString(),
+                }, dPoPNonce);
+            }
+        }
+
+        return response;
+    }
+
+    /// <summary>
+    /// Creates a DPoP proof token and attaches it to a request.
+    /// </summary>
+    internal async Task SetDPoPProofTokenForCodeExchangeAsync(HttpRequestMessage request, string? dpopNonce = null, string? jwk = null)
+    {
+        if (!string.IsNullOrEmpty(jwk))
+        {
+            // remove any old headers
+            request.ClearDPoPProofToken();
+
+            // create proof
+            var proofToken = await _dPoPProofService.CreateProofTokenAsync(new DPoPProofRequest
+            {
+                Url = request.GetDPoPUrl(),
+                Method = request.Method.ToString(),
+                DPoPJsonWebKey = jwk,
+                DPoPNonce = dpopNonce,
+            });
+
+            if (proofToken != null)
+            {
+                _logger.LogDebug("Sending DPoP proof token in request to endpoint: {url}",
+                    request.RequestUri?.GetLeftPart(System.UriPartial.Path));
+                request.SetDPoPProofToken(proofToken.ProofToken);
+            }
+            else
+            {
+                _logger.LogDebug("No DPoP proof token in request to endpoint: {url}",
+                    request.RequestUri?.GetLeftPart(System.UriPartial.Path));
+            }
+        }
+    }
+}

src/Duende.AccessTokenManagement.OpenIdConnect/ConfigureOpenIdConnectClientCredentialsOptions.cs

@@ -7,7 +7,7 @@
 namespace Duende.AccessTokenManagement.OpenIdConnect;
 
 /// <summary>
-/// Named options to synthetize client credentials based on OIDC handler configuration
+/// Named options to synthesize client credentials based on OIDC handler configuration
 /// </summary>
 public class ConfigureOpenIdConnectClientCredentialsOptions : IConfigureNamedOptions<ClientCredentialsClient>
 {

src/Duende.AccessTokenManagement.OpenIdConnect/ConfigureOpenIdConnectOptions.cs

@@ -6,6 +6,7 @@
 using Microsoft.AspNetCore.Authentication.OpenIdConnect;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using System;
 using System.Net.Http;
@@ -22,6 +23,9 @@ public class ConfigureOpenIdConnectOptions : IConfigureNamedOptions<OpenIdConnec
     private readonly IDPoPProofService _dPoPProofService;
     private readonly IHttpContextAccessor _httpContextAccessor;
     private readonly IOptions<UserTokenManagementOptions> _userAccessTokenManagementOptions;
+
+    private readonly ILoggerFactory _loggerFactory;
+
     private readonly string? _configScheme;
     private readonly string _clientName;
 
@@ -33,13 +37,14 @@ public ConfigureOpenIdConnectOptions(
         IDPoPProofService dPoPProofService,
         IHttpContextAccessor httpContextAccessor,
         IOptions<UserTokenManagementOptions> userAccessTokenManagementOptions,
-        IAuthenticationSchemeProvider schemeProvider)
+        IAuthenticationSchemeProvider schemeProvider,
+        ILoggerFactory loggerFactory)
     {
         _dPoPNonceStore = dPoPNonceStore;
         _dPoPProofService = dPoPProofService;
         _httpContextAccessor = httpContextAccessor;
         _userAccessTokenManagementOptions = userAccessTokenManagementOptions;
-        
+
         _configScheme = _userAccessTokenManagementOptions.Value.ChallengeScheme;
         if (string.IsNullOrWhiteSpace(_configScheme))
         {
@@ -55,6 +60,7 @@ public ConfigureOpenIdConnectOptions(
         }
 
         _clientName = OpenIdConnectTokenManagementDefaults.ClientCredentialsClientNamePrefix + _configScheme;
+        _loggerFactory = loggerFactory;
     }
 
     /// <inheritdoc/>
@@ -72,7 +78,7 @@ public void Configure(string? name, OpenIdConnectOptions options)
             options.Events.OnAuthorizationCodeReceived = CreateCallback(options.Events.OnAuthorizationCodeReceived);
             options.Events.OnTokenValidated = CreateCallback(options.Events.OnTokenValidated);
 
-            options.BackchannelHttpHandler = new DPoPProofTokenHandler(_dPoPProofService, _dPoPNonceStore, _httpContextAccessor)
+            options.BackchannelHttpHandler = new AuthorizationServerDPoPHandler(_dPoPProofService, _dPoPNonceStore, _httpContextAccessor, _loggerFactory)
             {
                 InnerHandler = options.BackchannelHttpHandler ?? new HttpClientHandler()
             };
@@ -103,7 +109,10 @@ async Task Callback(RedirectContext context)
                 // checking for null allows for opt-out from using DPoP
                 if (jkt != null)
                 {
-                    // we store the proof key here to associate it with the access token returned
+                    // we store the proof key here to associate it with the
+                    // authorization code that will be returned. Ultimately we
+                    // use this to provide proof of possession during code
+                    // exchange.
                     context.Properties.SetProofKey(key.JsonWebKey);
 
                     // pass jkt to authorize endpoint
@@ -126,7 +135,7 @@ Task Callback(AuthorizationCodeReceivedContext context)
             if (jwk != null)
             {
                 // set it so the OIDC message handler can find it
-                context.HttpContext.SetOutboundProofKey(jwk);
+                context.HttpContext.SetCodeExchangeDPoPKey(jwk);
             }
 
             return result;

src/Duende.AccessTokenManagement.OpenIdConnect/TokenManagementHttpContextExtensions.cs

@@ -9,6 +9,7 @@
 using Duende.AccessTokenManagement;
 using Duende.AccessTokenManagement.OpenIdConnect;
 using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Logging;
 
 namespace Microsoft.AspNetCore.Authentication;
 
@@ -105,11 +106,11 @@ internal static void RemoveProofKey(this AuthenticationProperties properties)
     }
 
     const string HttpContextDPoPKey = "dpop_proof_key";
-    internal static void SetOutboundProofKey(this HttpContext context, string key)
+    internal static void SetCodeExchangeDPoPKey(this HttpContext context, string key)
     {
         context.Items[HttpContextDPoPKey] = key;
     }
-    internal static string? GetOutboundProofKey(this HttpContext context)
+    internal static string? GetCodeExchangeDPoPKey(this HttpContext context)
     {
         if (context.Items.ContainsKey(HttpContextDPoPKey))
         {

src/Duende.AccessTokenManagement.OpenIdConnect/UserTokenEndpointService.cs

@@ -115,6 +115,8 @@ public async Task<UserToken> RefreshAccessTokenAsync(
             dPoPJsonWebKey != null && 
             response.DPoPNonce != null)
         {
+            _logger.LogDebug("DPoP error during token refresh. Retrying with server nonce");
+
             var proof = await _dPoPProofService.CreateProofTokenAsync(new DPoPProofRequest
             {
                 Url = request.Address!,

src/Duende.AccessTokenManagement/DPoPExtensions.cs

@@ -43,7 +43,7 @@ public static void SetDPoPProofToken(this HttpRequestMessage request, string? pr
     }
 
     /// <summary>
-    /// Reads the WWW-Authenticate response header to determine if the respone is in error due to DPoP
+    /// Reads the WWW-Authenticate response header to determine if the response is in error due to DPoP
     /// </summary>
     public static bool IsDPoPError(this HttpResponseMessage response)
     {