ASP.NET Owin OAuth (Google / Facebook) 正在重定向到默认的 login.aspx，而不是远程登录页面

我正在使用 Owin 库（包括 Google 和 Facebook）设置 OAuth。

从表面上看，Owin 启动课程注册得很好。我发现我没有被重定向到 Facebook 或 Google 的相应登录页面，而是被重定向到默认的“login.aspx”页面。我的解决方案中没有 login.aspx 页面。

该流程在视图中触发，如下所示：

@{
        // Get list of configured external authentication middleware

        var loginProviders = Context.GetOwinContext().Authentication.GetExternalAuthenticationTypes();

        if (!loginProviders.Any())
        {
            <div>
                <p>There are no external authentication services configured</p>
            </div>
        }
        else
        {
            using (Html.BeginForm("ExternalLogin", "OAuth"))
            {
                @Html.AntiForgeryToken()

                <div>
                    <p>
                        @foreach (AuthenticationDescription p in loginProviders)
                        {
                            <button type="submit" class="btn btn-default" id="@p.AuthenticationType" name="provider" value="@p.AuthenticationType" title="Log in using your @p.Caption account">@p.AuthenticationType</button>
                        }
                    </p>
                </div>
            }
        }
    }

这会触发质询结果，但是质询结果只会导致重定向到 login.aspx（该地址又不存在）

[HttpPost]
        [AllowAnonymous]
        [ValidateAntiForgeryToken]
        public ActionResult ExternalLogin(string provider)
        {
            string redirectUri = Url.Action("ExternalLoginCallback");

            // Request a redirect to the external login provider
            return new ChallengeResult(provider, redirectUri);
        }

我可能会错过什么？

为了更好地衡量，我已经包含了 Startup.cs 类：

public void Configuration(IAppBuilder app)
        {

            app.UseCookieAuthentication(

               new CookieAuthenticationOptions
               {
                   AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie
               });

            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

            app.UseFacebookAuthentication(new FacebookAuthenticationOptions
            {
                AppId = Config.OAuthFacebookAppId,
                AppSecret = Config.OAuthFacebookAppSecret,
                Scope = { "email" }, // "email", also "publish_actions" can be included if post to facebook authorization is required
                Provider = new FacebookAuthenticationProvider
                {
                    OnAuthenticated = context =>
                    {
                        context.Identity.AddClaim(new System.Security.Claims.Claim("FacebookAccessToken", context.AccessToken));
                        return Task.FromResult(true);
                    }
                }
            });

            app.UseGoogleAuthentication(
                 clientId: Config.OAuthGoogleClientId,
                 clientSecret: Config.OAuthGoogleClientSecret
            );
        }

关键修改是添加代码：

// Stop execution of the current page/method - the 401 forces OWIN to kick-in and do its thing

Response.StatusCode = 401;
Response.End();

AuthenticationProperties.RedirectUri 未在 Challenge() 中传递给 Google https://stackoverflow.com/questions/33698266/authenticationproperties-redirecturi-is-not-passed-to-google-in-challenge

其他问题是 Google+ API 未启用

OWIN 的 GetExternalLoginInfoAsync 始终返回 null https://stackoverflow.com/questions/19775321/owins-getexternallogininfoasync-always-returns-null/29921451#29921451

...对于 Facebook，需要将 Owin 库升级到 3.1.0

MVC5 空引用与 facebook 登录 https://stackoverflow.com/questions/20180562/mvc5-null-reference-with-facebook-login

完整的ExternalLogin方法：

[HttpPost]
        [AllowAnonymous]
        [ValidateAntiForgeryToken]
        public void ExternalLogin(string provider)
        {
            string redirectUri = Url.Action("ExternalLoginCallback");

            var properties = new AuthenticationProperties() { RedirectUri = redirectUri };
            HttpContext.GetOwinContext().Authentication.Challenge(properties, provider);

            // Stop execution of the current page/method - the 401 forces OWIN to kick-in and do its thing

            Response.StatusCode = 401;
            Response.End();
        }