C# 如何在客户端获取DotNetOpenAuth.OAuth2返回的错误消息？

我正在使用

ExchangeUserCredentialForToken

函数从授权服务器获取令牌。当我的用户存在于我的数据库中时，它可以正常工作，但当凭据不正确时，我希望向客户端发回一条消息。我使用以下两行代码设置错误消息：

context.SetError("Autorization Error", "The username or password is incorrect!");
context.Rejected();

但是在客户端，我得到的只是协议错误（错误400）。您能帮助我如何在授权服务器的服务器端获取错误消息集吗

来自授权服务器的完整应用程序配置：

using Constants;
using Microsoft.Owin;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Cookies;
using Microsoft.Owin.Security.Infrastructure;
using Microsoft.Owin.Security.OAuth;
using Owin;
using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Security.Claims;
using System.Security.Principal;
using System.Threading.Tasks;
using AuthorizationServer.Entities;
using AuthorizationServer.Entities.Infrastructure.Abstract;
using AuthorizationServer.Entities.Infrastructure.Concrete;

namespace AuthorizationServer
{
    public partial class Startup
    {
        private IEmployeeRepository Repository;  
        public void ConfigureAuth(IAppBuilder app)
        {
            //instanciate the repository
            Repository = new EmployeeRepository();

            // Enable Application Sign In Cookie
            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = "Application",
                AuthenticationMode = AuthenticationMode.Passive,
                LoginPath = new PathString(Paths.LoginPath),
                LogoutPath = new PathString(Paths.LogoutPath),
            });

            // Enable External Sign In Cookie
            app.SetDefaultSignInAsAuthenticationType("External");
            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = "External",
                AuthenticationMode = AuthenticationMode.Passive,
                CookieName = CookieAuthenticationDefaults.CookiePrefix + "External",
                ExpireTimeSpan = TimeSpan.FromMinutes(5),
            });

            // Enable google authentication
            app.UseGoogleAuthentication();

            // Setup Authorization Server
            app.UseOAuthAuthorizationServer(new OAuthAuthorizationServerOptions
            {
                AuthorizeEndpointPath = new PathString(Paths.AuthorizePath),
                TokenEndpointPath = new PathString(Paths.TokenPath),
                ApplicationCanDisplayErrors = true,
#if DEBUG
                AllowInsecureHttp = true,
#endif
                // Authorization server provider which controls the lifecycle of Authorization Server
                Provider = new OAuthAuthorizationServerProvider
                {
                    OnValidateClientRedirectUri = ValidateClientRedirectUri,
                    OnValidateClientAuthentication = ValidateClientAuthentication,
                    OnGrantResourceOwnerCredentials = GrantResourceOwnerCredentials,
                    OnGrantClientCredentials = GrantClientCredetails
                },

                // Authorization code provider which creates and receives authorization code
                AuthorizationCodeProvider = new AuthenticationTokenProvider
                {
                    OnCreate = CreateAuthenticationCode,
                    OnReceive = ReceiveAuthenticationCode,
                },

                // Refresh token provider which creates and receives referesh token
                RefreshTokenProvider = new AuthenticationTokenProvider
                {
                    OnCreate = CreateRefreshToken,
                    OnReceive = ReceiveRefreshToken,
                }
            });

            // indicate our intent to use bearer authentication
            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions
            {
                AuthenticationType = "Bearer",
                AuthenticationMode = Microsoft.Owin.Security.AuthenticationMode.Active
            });
        }

        private Task ValidateClientRedirectUri(OAuthValidateClientRedirectUriContext context)
        {
            if (context.ClientId == Clients.Client1.Id)
            {
                context.Validated(Clients.Client1.RedirectUrl);
            }
            else if (context.ClientId == Clients.Client2.Id)
            {
                context.Validated(Clients.Client2.RedirectUrl);
            }
            return Task.FromResult(0);
        }

        private Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
        {

            string clientname;
            string clientpassword;


            if (context.TryGetBasicCredentials(out clientname, out clientpassword) ||
                context.TryGetFormCredentials(out clientname, out clientpassword))
            {
                employee Employee = Repository.GetEmployee(clientname, clientpassword);

                if (Employee != null)
                {
                    context.Validated();
                }
                else
                {
                    context.SetError("Autorization Error", "The username or password is incorrect!");
                    context.Rejected();
                }
            }
            return Task.FromResult(0);
        }

        private Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            var identity = new ClaimsIdentity(new GenericIdentity(context.UserName, OAuthDefaults.AuthenticationType), context.Scope.Select(x => new Claim("urn:oauth:scope", x)));

            context.Validated(identity);

            return Task.FromResult(0);
        }

        private Task GrantClientCredetails(OAuthGrantClientCredentialsContext context)
        {
            var identity = new ClaimsIdentity(new GenericIdentity(context.ClientId, OAuthDefaults.AuthenticationType), context.Scope.Select(x => new Claim("urn:oauth:scope", x)));

            context.Validated(identity);

            return Task.FromResult(0);
        }


        private readonly ConcurrentDictionary<string, string> _authenticationCodes =
            new ConcurrentDictionary<string, string>(StringComparer.Ordinal);

        private void CreateAuthenticationCode(AuthenticationTokenCreateContext context)
        {
            context.SetToken(Guid.NewGuid().ToString("n") + Guid.NewGuid().ToString("n"));
            _authenticationCodes[context.Token] = context.SerializeTicket();
        }

        private void ReceiveAuthenticationCode(AuthenticationTokenReceiveContext context)
        {
            string value;
            if (_authenticationCodes.TryRemove(context.Token, out value))
            {
                context.DeserializeTicket(value);
            }
        }

        private void CreateRefreshToken(AuthenticationTokenCreateContext context)
        {
            context.SetToken(context.SerializeTicket());
        }

        private void ReceiveRefreshToken(AuthenticationTokenReceiveContext context)
        {
            context.DeserializeTicket(context.Token);
        }
    }
}

使用常量；
使用Microsoft.Owin；
使用Microsoft.Owin.Security；
使用Microsoft.Owin.Security.Cookies；
使用Microsoft.Owin.Security.Infrastructure；
使用Microsoft.Owin.Security.OAuth；
使用Owin；
使用制度；
使用System.Collections.Concurrent；
使用System.Linq；
使用System.Security.Claims；
使用System.Security.Principal；
使用System.Threading.Tasks；
使用AuthorizationServer.Entities；
使用AuthorizationServer.Entities.Infrastructure.Abstract；
使用AuthorizationServer.Entities.Infrastructure.Concrete；
命名空间授权服务器
{
公共部分类启动
{
私人雇员存储库；
public void ConfigureAuth（IAppBuilder应用程序）
{
//实例化存储库
Repository=新员工Repository（）；
//启用应用程序登录Cookie
app.UseCookieAuthentication（新的CookieAuthenticationOptions
{
AuthenticationType=“应用程序”，
AuthenticationMode=AuthenticationMode.Passive，
LoginPath=新路径字符串（path.LoginPath），
LogoutPath=新路径字符串（path.LogoutPath），
});
//启用外部登录Cookie
app.setDefaultSignatureAuthenticationType（“外部”）；
app.UseCookieAuthentication（新的CookieAuthenticationOptions
{
AuthenticationType=“外部”，
AuthenticationMode=AuthenticationMode.Passive，
CookieName=CookieAuthenticationDefaults.CookiePrefix+“外部”，
ExpireTimeSpan=从分钟（5）开始的时间跨度，
});
//启用google身份验证
app.UseGoogleAuthentication（）；
//设置授权服务器
app.useAuthorizationServer（新的OAuthorizationServerOptions
{
AuthorizeEndpointPath=新路径字符串（path.AuthorizePath），
TokenEndpointPath=新路径字符串（path.TokenPath），
ApplicationAndDisplayErrors=true，
#如果调试
AllowInsecureHttp=true，
#恩迪夫
//授权服务器提供程序，用于控制授权服务器的生命周期
Provider=新的OAuthAuthorizationServerProvider
{
OnValidateClientRedirectUri=ValidateClientRedirectUri，
OnValidateClientAuthentication=ValidateClientAuthentication，
OnGrantResourceOwnerCredentials=GrantResourceOwnerCredentials，
OnGrantClientCredentials=GrantClientCredentials详细信息
},
//创建和接收授权代码的授权代码提供程序
AuthorizationCodeProvider=新的AuthenticationTokenProvider
{
OnCreate=CreateAuthenticationCode，
OnReceive=ReceiveAuthenticationCode，
},
//刷新创建和接收referesh令牌的令牌提供程序
RefreshTokenProvider=新的AuthenticationTokenProvider
{
OnCreate=CreateRefreshToken，
OnReceive=ReceiverFreshToken，
}
});
//表明我们打算使用承载身份验证
app.useAuthBeareAuthentication（新的OAuthBeareAuthenticationOptions
{
AuthenticationType=“承载人”，
AuthenticationMode=Microsoft.Owin.Security.AuthenticationMode.Active
});
}
专用任务ValidateClientRedirectUri（OAuthValidateClientRedirectUriContext上下文）
{
if（context.ClientId==Clients.Client1.Id）
{
context.Validated（Clients.Client1.RedirectUrl）；
}
else if（context.ClientId==Clients.Client2.Id）
{
context.Validated（Clients.Client2.RedirectUrl）；
}
返回Task.FromResult（0）；
}
专用任务ValidateClientAuthentication（OAuthValidateClientAuthenticationContext）
{
字符串clientname；
字符串clientpassword；
if（context.TryGetBasicCredentials（out clientname，out clientpassword）||
TryGetFormCredentials（out clientname，out clientpassword））
{
employee=Repository.GetEmployee（clientname，clientpassword）；
if（Employee！=null）
{
context.Validated（）；
}
其他的
{
SetError（“自动化错误”，“用户名或密码不正确！”）；
context.Rejected（）；
}
}
返回Task.FromResult（0）；
}
专用任务GrantResourceOwnerCredentials（OAuthGrantResourceOwnerCredentials上下文）
{
var identity=newclaimsidentity（newgenericientity（context.UserName，OAuthDefaults.AuthenticationType），context.Scope.Select（x=>newclaim（“urn:oauth:Scope”，x））；
上下文验证（身份）；
返回Task.FromResult（0）；
}
专用任务GrantClientCredetails（OAuthGrantClientCredentialsContext）
    context.SetError("Account locked", 
             "You have exceeded the total allowed failed logins.  Please try back in an hour.");
    context.Rejected();

public static class ServerGlobalVariables
{
//Your other properties...
public const string OwinChallengeFlag = "X-Challenge";
}

//Set the error message
context.SetError("Account locked", 
        "You have exceeded the total allowed failed logins.  Please try back in an hour.");

//Add your flag to the header of the response
context.Response.Headers.Add(ServerGlobalVariables.OwinChallengeFlag, 
         new[] { ((int)HttpStatusCode.Unauthorized).ToString() }); 

//This class handles all the OwinMiddleware responses, so the name should 
//not just focus on invalid authentication
public class CustomAuthenticationMiddleware : OwinMiddleware
{
    public CustomAuthenticationMiddleware(OwinMiddleware next)
        : base(next)
    {
    }

    public override async Task Invoke(IOwinContext context)
    {
        await Next.Invoke(context);

        if (context.Response.StatusCode == 400 
            && context.Response.Headers.ContainsKey(
                      ServerGlobalVariables.OwinChallengeFlag))
        {
            var headerValues = context.Response.Headers.GetValues
                  (ServerGlobalVariables.OwinChallengeFlag);

            context.Response.StatusCode = 
                   Convert.ToInt16(headerValues.FirstOrDefault());

            context.Response.Headers.Remove(
                   ServerGlobalVariables.OwinChallengeFlag);
        }         

    }
}

app.Use<CustomAuthenticationMiddleware>();

//Need to create a class to deserialize the Json
//Create this somewhere in your application
public class OAuthErrorMsg
    {
        public string error { get; set; }
        public string error_description { get; set; }
        public string error_uri { get; set; }
    }

 //Need to make sure to include Newtonsoft.Json
 using Newtonsoft.Json;

 //Code for your object....

 private void login()
    {
        try
        {
            var state = _webServerClient.ExchangeUserCredentialForToken(
                this.emailTextBox.Text, 
                this.passwordBox.Password.Trim(), 
                scopes: new string[] { "PublicProfile" });

            _accessToken = state.AccessToken;
            _refreshToken = state.RefreshToken;
        }
        catch (ProtocolException ex)
        {
            var webException = ex.InnerException as WebException;

            OAuthErrorMsg error = 
                JsonConvert.DeserializeObject<OAuthErrorMsg>(
                ExtractResponseString(webException));

            var errorMessage = error.error_description;
            //Now it's up to you how you process the errorMessage
        }
    }

    public static string ExtractResponseString(WebException webException)
    {
        if (webException == null || webException.Response == null)
            return null;

        var responseStream = 
            webException.Response.GetResponseStream() as MemoryStream;

        if (responseStream == null)
            return null;

        var responseBytes = responseStream.ToArray();

        var responseString = Encoding.UTF8.GetString(responseBytes);
        return responseString;
    }

context.SetError("Autorization Error", "The username or password is incorrect!");
context.Response.Headers.Add("AuthorizationResponse", new[] { "Failed" });

public class InvalidAuthenticationMiddleware : OwinMiddleware
{
    public InvalidAuthenticationMiddleware(OwinMiddleware next) 
        : base(next)
    {
    }

    public override async Task Invoke(IOwinContext context)
    {
        await Next.Invoke(context);

        if (context.Response.StatusCode == 400 && context.Response.Headers.ContainsKey("AuthorizationResponse"))
        {
            context.Response.Headers.Remove("AuthorizationResponse");
            context.Response.StatusCode = 401;
        }
    }
}

app.Use<InvalidAuthenticationMiddleware>();

public class InvalidAuthenticationMiddleware : OwinMiddleware
{
    public InvalidAuthenticationMiddleware(OwinMiddleware next) : base(next) { }

    public override async Task Invoke(IOwinContext context)
    {
        context.Response.OnSendingHeaders(state =>
        {
            var response = (OwinResponse)state;

            if (!response.Headers.ContainsKey("AuthorizationResponse") && response.StatusCode != 400) return;

            response.Headers.Remove("AuthorizationResponse");
            response.StatusCode = 401;

        }, context.Response);

        await Next.Invoke(context);
    }
}