WebApi ASP.NET身份Facebook登录

显然，所有WebAPI Owin OAuth选项都是基于浏览器的，也就是说他们需要大量的浏览器重定向请求，不适合本地移动应用程序(我的情况)。
我仍然在调查和实验，但正如Hongye Sun在他的博客文章http://blogs.msdn.com/b/webdev/archive/2013/09/20/understanding-security-features-in-spa-template.aspx?PageIndex=2#comments的一个评论中所简要描述的，使用Facebook登录访问令牌可以直接通过API进行验证，通过图形调用/ me端点。

通过使用图形调用返回的信息，您可以检查用户是否已经注册。
最后，我们需要登录用户，也许使用Authentication.SignIn Owin方法，返回一个将用于所有后续API调用的承载令牌。

编辑：
实际上我错了，承载令牌是发出呼叫“/ Token”端点，其上输入接受类似grant_type =密码&用户名=爱丽丝&密码=密码123
这里的问题是我们没有密码(这是OAuth机制的整个要点)，那么我们还能如何调用“/ Token”端点呢？

更新：
我终于找到一个工作的解决方案，以下是我不得不添加到现有的类，使其工作：
Startup.Auth.cs

public partial class Startup
{
    /// <summary>
    /// This part has been added to have an API endpoint to authenticate users that accept a Facebook access token
    /// </summary>
    static Startup()
    {
        PublicClientId = "self";

        //UserManagerFactory = () => new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));
        UserManagerFactory = () => 
        {
            var userManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));
            userManager.UserValidator = new UserValidator<ApplicationUser>(userManager) { AllowOnlyAlphanumericUserNames = false };
            return userManager;
        };

        OAuthOptions = new OAuthAuthorizationServerOptions
        {
            TokenEndpointPath = new PathString("/Token"),Provider = new ApplicationOAuthProvider(PublicClientId,UserManagerFactory),AuthorizeEndpointPath = new PathString("/api/Account/ExternalLogin"),AccessTokenExpireTimeSpan = TimeSpan.FromDays(14),AllowInsecureHttp = true
        };

        OAuthBearerOptions = new OAuthBearerAuthenticationOptions();
        OAuthBearerOptions.AccessTokenFormat = OAuthOptions.AccessTokenFormat;
        OAuthBearerOptions.AccessTokenProvider = OAuthOptions.AccessTokenProvider;
        OAuthBearerOptions.AuthenticationMode = OAuthOptions.AuthenticationMode;
        OAuthBearerOptions.AuthenticationType = OAuthOptions.AuthenticationType;
        OAuthBearerOptions.Description = OAuthOptions.Description;
        OAuthBearerOptions.Provider = new CustomBearerAuthenticationProvider();            
        OAuthBearerOptions.SystemClock = OAuthOptions.SystemClock;
    }

    public static OAuthBearerAuthenticationOptions OAuthBearerOptions { get; private set; }

    public static OAuthAuthorizationServerOptions OAuthOptions { get; private set; }

    public static Func<UserManager<ApplicationUser>> UserManagerFactory { get; set; }

    public static string PublicClientId { get; private set; }

    // For more information on configuring authentication,please visit http://go.microsoft.com/fwlink/?LinkId=301864
    public void ConfigureAuth(IAppBuilder app)
    {
        [Initial boilerplate code]

        OAuthBearerAuthenticationExtensions.USEOAuthBearerAuthentication(app,OAuthBearerOptions);

        [More boilerplate code]
    }
}

public class CustomBearerAuthenticationProvider : OAuthBearerAuthenticationProvider
{
    public override Task ValidateIdentity(OAuthValidateIdentityContext context)
    {
        var claims = context.Ticket.Identity.Claims;
        if (claims.Count() == 0 || claims.Any(claim => claim.Issuer != "Facebook" && claim.Issuer != "LOCAL_AUTHORITY" ))
            context.Rejected();
        return Task.FromResult<object>(null);
    }
}

进入AccountController，我添加了以下操作

[HttpPost]
        [AllowAnonymous]
        [Route("FacebookLogin")]
        public async Task<IHttpActionResult> FacebookLogin(string token)
        {
            [Code to validate input...]
            var tokenExpirationTimeSpan = TimeSpan.FromDays(14);            
            ApplicationUser user = null;    
            // Get the fb access token and make a graph call to the /me endpoint    
            // Check if the user is already registered
            // If yes retrieve the user 
            // If not,register it  
            // Finally sign-in the user: this is the key part of the code that creates the bearer token and authenticate the user
            var identity = new ClaimsIdentity(Startup.OAuthBearerOptions.AuthenticationType);
            identity.AddClaim(new Claim(ClaimTypes.Name,user.Id,null,"Facebook"));
                // This claim is used to correctly populate user id
                identity.AddClaim(new Claim(ClaimTypes.NameIdentifier,"LOCAL_AUTHORITY"));
            AuthenticationTicket ticket = new AuthenticationTicket(identity,new AuthenticationProperties());            
            var currentUtc = new Microsoft.Owin.Infrastructure.SystemClock().UtcNow;
            ticket.Properties.IssuedUtc = currentUtc;
            ticket.Properties.ExpiresUtc = currentUtc.Add(tokenExpirationTimeSpan);            
            var accesstoken = Startup.OAuthBearerOptions.AccessTokenFormat.Protect(ticket); 
            Authentication.SignIn(identity);

            // Create the response
            JObject blob = new JObject(
                new JProperty("userName",user.UserName),new JProperty("access_token",accesstoken),new JProperty("token_type","bearer"),new JProperty("expires_in",tokenExpirationTimeSpan.TotalSeconds.ToString()),new JProperty(".issued",ticket.Properties.IssuedUtc.ToString()),new JProperty(".expires",ticket.Properties.ExpiresUtc.ToString())
            );
            var json = Newtonsoft.Json.JsonConvert.SerializeObject(blob);
            // Return OK
            return Ok(blob);
        }

而已。我发现与经典/令牌端点响应的唯一的区别是承载令牌稍短，过期和发布日期在UTC，而不是在GMT(至少在我的机器上)。

我希望这有帮助！