Add BFF Sample using DPoP

IdentityServer/v6/BFF/DPoP/.vscode/launch.json

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+{
+    "version": "0.2.0",
+    "compounds": [
+        {
+            "name": "Run All",
+            "configurations": ["BFF", "API"],
+            "presentation": {
+                "hidden": false,
+                "group": "",
+                "order": 1
+            }
+        }
+    ],
+    "configurations": [
+        {
+            "name": "API",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build-api",
+            "program": "${workspaceFolder}/DPoP.Api/bin/Debug/net6.0/DPoP.Api.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}/DPoP.Api",
+            "env": {
+                "ASPNETCORE_ENVIRONMENT": "Development"
+            },
+            "console": "externalTerminal",
+        },
+        {
+            "name": "BFF",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build-bff",
+            "program": "${workspaceFolder}/DPoP.Bff/bin/Debug/net6.0/DPoP.Bff.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}/DPoP.Bff",
+            "env": {
+                "ASPNETCORE_ENVIRONMENT": "Development"
+            },
+            "serverReadyAction": {
+                "action": "openExternally",
+                "pattern": "\\bNow listening on:\\s+(https?://\\S+)"
+            },
+            "console": "externalTerminal",
+        }
+    ]
+}

IdentityServer/v6/BFF/DPoP/.vscode/tasks.json

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+{
+    "version": "2.0.0",
+    "tasks": [
+      {
+        "label": "build",
+        "type": "process",
+        "command": "dotnet",
+        "args": [
+            "build",
+            "${workspaceFolder}/DPoP.sln",
+            "/property:GenerateFullPaths=true",
+            "/consoleloggerparameters:NoSummary"
+        ],
+        "problemMatcher": "$msCompile"
+      },
+      {
+        "label": "build-api",
+        "type": "process",
+        "command": "dotnet",
+        "args": [
+            "build",
+            "${workspaceFolder}\\DPoP.Api\\DPoP.Api.csproj",
+            "/property:GenerateFullPaths=true",
+            "/consoleloggerparameters:NoSummary"
+        ],
+        "problemMatcher": "$msCompile"
+      },
+      {
+        "label": "build-bff",
+        "type": "process",
+        "command": "dotnet",
+        "args": [
+            "build",
+            "${workspaceFolder}\\DPoP.Bff\\DPoP.Bff.csproj",
+
+            "/property:GenerateFullPaths=true",
+            "/consoleloggerparameters:NoSummary"
+        ],
+        "problemMatcher": "$msCompile"
+      }
+    ]
+
+}

IdentityServer/v6/BFF/DPoP/DPoP.Api/DPoP.Api.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="IdentityModel" version="6.1.0" />
+        <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="6.0.9" />
+        <PackageReference Include="Serilog.AspNetCore" Version="6.0.1" />
+    </ItemGroup>
+</Project>

IdentityServer/v6/BFF/DPoP/DPoP.Api/DPoP/ConfigureJwtBearerOptions.cs

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+using Microsoft.AspNetCore.Authentication.JwtBearer;
+using Microsoft.Extensions.Options;
+using System;
+
+namespace DPoP.Api;
+
+public class ConfigureJwtBearerOptions : IPostConfigureOptions<JwtBearerOptions>
+{
+    private readonly string _configScheme;
+
+    public ConfigureJwtBearerOptions(string configScheme)
+    {
+        _configScheme = configScheme;
+    }
+
+    public void PostConfigure(string name, JwtBearerOptions options)
+    {
+        if (_configScheme == name)
+        {
+            if (options.EventsType != null && !typeof(DPoPJwtBearerEvents).IsAssignableFrom(options.EventsType))
+            {
+                throw new Exception("EventsType on JwtBearerOptions must derive from DPoPJwtBearerEvents to work with the DPoP support.");
+            }
+            if (options.Events != null && !typeof(DPoPJwtBearerEvents).IsAssignableFrom(options.Events.GetType()))
+            {
+                throw new Exception("Events on JwtBearerOptions must derive from DPoPJwtBearerEvents to work with the DPoP support.");
+            }
+
+            if (options.Events == null && options.EventsType == null)
+            {
+                options.EventsType = typeof(DPoPJwtBearerEvents);
+            }
+        }
+    }
+}

IdentityServer/v6/BFF/DPoP/DPoP.Api/DPoP/DPoPExtensions.cs

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+using IdentityModel;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Http;
+using Microsoft.IdentityModel.Tokens;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json;
+
+namespace DPoP.Api;
+
+/// <summary>
+/// Extensions methods for DPoP
+/// </summary>
+static class DPoPExtensions
+{
+    const string DPoPPrefix = OidcConstants.AuthenticationSchemes.AuthorizationHeaderDPoP + " ";
+
+    public static bool IsDPoPAuthorizationScheme(this HttpRequest request)
+    {
+        var authz = request.Headers.Authorization.FirstOrDefault();
+        return authz?.StartsWith(DPoPPrefix, System.StringComparison.Ordinal) == true;
+    }
+
+    public static bool TryGetDPoPAccessToken(this HttpRequest request, out string token)
+    {
+        token = null;
+
+        var authz = request.Headers.Authorization.FirstOrDefault();
+        if (authz?.StartsWith(DPoPPrefix, System.StringComparison.Ordinal) == true)
+        {
+            token = authz[DPoPPrefix.Length..].Trim();
+            return true;
+        }
+        return false;
+    }
+
+    public static string GetAuthorizationScheme(this HttpRequest request)
+    {
+        return request.Headers.Authorization.FirstOrDefault()?.Split(' ', System.StringSplitOptions.RemoveEmptyEntries)[0];
+    }
+
+    public static string GetDPoPProofToken(this HttpRequest request)
+    {
+        return request.Headers[OidcConstants.HttpHeaders.DPoP].FirstOrDefault();
+    }
+
+    public static string GetDPoPNonce(this AuthenticationProperties props)
+    {
+        if (props.Items.ContainsKey("DPoP-Nonce"))
+        {
+            return props.Items["DPoP-Nonce"] as string;
+        }
+        return null;
+    }
+    public static void SetDPoPNonce(this AuthenticationProperties props, string nonce)
+    {
+        props.Items["DPoP-Nonce"] = nonce;
+    }
+
+    /// <summary>
+    /// Create the value of a thumbprint-based cnf claim
+    /// </summary>
+    public static string CreateThumbprintCnf(this JsonWebKey jwk)
+    {
+        var jkt = jwk.CreateThumbprint();
+        var values = new Dictionary<string, string>
+        {
+            { JwtClaimTypes.ConfirmationMethods.JwkThumbprint, jkt }
+        };
+        return JsonSerializer.Serialize(values);
+    }
+
+    /// <summary>
+    /// Create the value of a thumbprint
+    /// </summary>
+    public static string CreateThumbprint(this JsonWebKey jwk)
+    {
+        var jkt = Base64Url.Encode(jwk.ComputeJwkThumbprint());
+        return jkt;
+    }
+}

IdentityServer/v6/BFF/DPoP/DPoP.Api/DPoP/DPoPJwtBearerEvents.cs

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+using IdentityModel;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
+using Microsoft.Extensions.Options;
+using Microsoft.Net.Http.Headers;
+using System.Text;
+using System.Threading.Tasks;
+using static IdentityModel.OidcConstants;
+
+namespace DPoP.Api;
+
+public class DPoPJwtBearerEvents : JwtBearerEvents
+{
+    private readonly IOptionsMonitor<DPoPOptions> _optionsMonitor;
+    private readonly DPoPProofValidator _validator;
+
+    public DPoPJwtBearerEvents(IOptionsMonitor<DPoPOptions> optionsMonitor, DPoPProofValidator validator)
+    {
+        _optionsMonitor = optionsMonitor;
+        _validator = validator;
+    }
+
+    public override Task MessageReceived(MessageReceivedContext context)
+    {
+        var dpopOptions = _optionsMonitor.Get(context.Scheme.Name);
+
+        if (context.HttpContext.Request.TryGetDPoPAccessToken(out var token))
+        {
+            context.Token = token;
+        }
+        else if (dpopOptions.Mode == DPoPMode.DPoPOnly)
+        {
+            // this rejects the attempt for this handler,
+            // since we don't want to attempt Bearer given the Mode
+            context.NoResult();
+        }
+
+        return Task.CompletedTask;
+    }
+
+    public override async Task TokenValidated(TokenValidatedContext context)
+    {
+        var dpopOptions = _optionsMonitor.Get(context.Scheme.Name);
+
+        if (context.HttpContext.Request.TryGetDPoPAccessToken(out var at))
+        {
+            var proofToken = context.HttpContext.Request.GetDPoPProofToken();
+            var result = await _validator.ValidateAsync(new DPoPProofValidatonContext
+            {
+                Scheme = context.Scheme.Name,
+                ProofToken = proofToken,
+                AccessToken = at,
+                Method = context.HttpContext.Request.Method,
+                Url = context.HttpContext.Request.Scheme + "://" + context.HttpContext.Request.Host + context.HttpContext.Request.PathBase + context.HttpContext.Request.Path
+            });
+
+            if (result.IsError)
+            {
+                // fails the result
+                context.Fail(result.ErrorDescription ?? result.Error);
+
+                // we need to stash these values away so they are available later when the Challenge method is called later
+                context.HttpContext.Items["DPoP-Error"] = result.Error;
+                if (!string.IsNullOrWhiteSpace(result.ErrorDescription))
+                {
+                    context.HttpContext.Items["DPoP-ErrorDescription"] = result.ErrorDescription;
+                }
+                if (!string.IsNullOrWhiteSpace(result.ServerIssuedNonce))
+                {
+                    context.HttpContext.Items["DPoP-Nonce"] = result.ServerIssuedNonce;
+                }
+            }
+        }
+        else if (dpopOptions.Mode == DPoPMode.DPoPAndBearer)
+        {
+            // if the scheme used was not DPoP, then it was Bearer
+            // and if a access token was presented with a cnf, then the 
+            // client should have sent it as DPoP, so we fail the request
+            if (context.Principal.HasClaim(x => x.Type == JwtClaimTypes.Confirmation))
+            {
+                context.HttpContext.Items["Bearer-ErrorDescription"] = "Must use DPoP when using an access token with a 'cnf' claim";
+                context.Fail("Must use DPoP when using an access token with a 'cnf' claim");
+            }
+        }
+    }
+
+    public override Task Challenge(JwtBearerChallengeContext context)
+    {
+        var dpopOptions = _optionsMonitor.Get(context.Scheme.Name);
+
+        if (dpopOptions.Mode == DPoPMode.DPoPOnly)
+        {
+            // if we are using DPoP only, then we don't need/want the default
+            // JwtBearerHandler to add its WWW-Authenticate response header
+            // so we have to set the status code ourselves
+            context.Response.StatusCode = 401;
+            context.HandleResponse();
+        }
+        else if (context.HttpContext.Items.ContainsKey("Bearer-ErrorDescription"))
+        {
+            var description = context.HttpContext.Items["Bearer-ErrorDescription"] as string;
+            context.ErrorDescription = description;
+        }
+
+        if (context.HttpContext.Request.IsDPoPAuthorizationScheme())
+        {
+            // if we are challening due to dpop, then don't allow bearer www-auth to emit an error
+            context.Error = null;
+        }
+
+        // now we always want to add our WWW-Authenticate for DPoP
+        // For example:
+        // WWW-Authenticate: DPoP error="invalid_dpop_proof", error_description="Invalid 'iat' value."
+        var sb = new StringBuilder();
+        sb.Append(OidcConstants.AuthenticationSchemes.AuthorizationHeaderDPoP);
+
+        if (context.HttpContext.Items.ContainsKey("DPoP-Error"))
+        {
+            var error = context.HttpContext.Items["DPoP-Error"] as string;
+            sb.Append(" error=\"");
+            sb.Append(error);
+            sb.Append('\"');
+
+            if (context.HttpContext.Items.ContainsKey("DPoP-ErrorDescription"))
+            {
+                var description = context.HttpContext.Items["DPoP-ErrorDescription"] as string;
+
+                sb.Append(", error_description=\"");
+                sb.Append(description);
+                sb.Append('\"');
+            }
+        }
+
+        context.Response.Headers.Add(HeaderNames.WWWAuthenticate, sb.ToString());
+
+
+        if (context.HttpContext.Items.ContainsKey("DPoP-Nonce"))
+        {
+            var nonce = context.HttpContext.Items["DPoP-Nonce"] as string;
+            context.Response.Headers[HttpHeaders.DPoPNonce] = nonce;
+        }
+        else
+        {
+            var nonce = context.Properties.GetDPoPNonce();
+            if (nonce != null)
+            {
+                context.Response.Headers[HttpHeaders.DPoPNonce] = nonce;
+            }
+        }
+
+        return Task.CompletedTask;
+    }
+}

IdentityServer/v6/BFF/DPoP/DPoP.Api/DPoP/DPoPMode.cs

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+namespace DPoP.Api;
+
+public enum DPoPMode
+{
+    /// <summary>
+    /// Only DPoP tokens will be accepted
+    /// </summary>
+    DPoPOnly,
+    /// <summary>
+    /// Both DPoP and Bearer tokens will be accepted
+    /// </summary>
+    DPoPAndBearer
+}