Web API 基于ASP.NET Identity的Basic Authentication

　　今天给大家分享在Web API下，如何利用ASP.NET Identity实现基本认证（Basic Authentication），在博客园子搜索了一圈Web API的基本认证，基本都是做的Forms认证，很少有Claims认证（声明式认证），而我们在用ASP.NET Identity实现登录，认证，授权的时候采用的是Claims认证。

　　在Web API2.0中认证接口为IAuthenticationFilter，我们只需实现该接口就行。创建BasicAuthenticationAttribute抽象基类，实现IAuthenticationFilter接口：

 1 public abstract class BasicAuthenticationAttribute : Attribute, IAuthenticationFilter 
 2     {
 3         protected abstract Task<IPrincipal> AuthenticateAsync(string userName, string password, HttpAuthenticationContext context,
 4             CancellationToken cancellationToken);
 5         public async Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
 6         {
 7             context.Principal = null;
 8             AuthenticationHeaderValue authenticationHeader = context.Request.Headers.Authorization;
 9             if (authenticationHeader != null && authenticationHeader.Scheme == "Basic")
10             {
11                 if (!string.IsNullOrEmpty(authenticationHeader.Parameter))
12                 {
13                     Tuple<string, string> data = GetUserNameAndPassword(authenticationHeader.Parameter);
14                     context.Principal = await AuthenticateAsync(data.Item1, data.Item2,context, cancellationToken);
15                 }
16             }
17 
18             if (context.Principal == null)
19             {
20                 context.ErrorResult = new UnauthorizedResult(new[] {new AuthenticationHeaderValue("Basic")},
21                     context.Request);
22             }
23         }
24         public Task ChallengeAsync(HttpAuthenticationChallengeContext context, CancellationToken cancellationToken)
25         {
26             return Task.FromResult(0);
27         }
28         public bool AllowMultiple
29         {
30             get { return false; }
31         }
32         private Tuple<string, string> GetUserNameAndPassword(string authenticationParameter)
33         {
34             if (!string.IsNullOrEmpty(authenticationParameter))
35             {
36                 var data = Encoding.ASCII.GetString(Convert.FromBase64String(authenticationParameter)).Split(':');
37                 return new Tuple<string, string>(data[0], data[1]);
38             }
39             return null;
40         }
41     }

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