InvalidOperationException:未指定authenticationScheme，未找到DefaultChallengeScheme

Question

我们有一个NetCore2.1API项目。我们使用请求头来检索API密钥，并根据数据库检查该密钥是否与期望的密钥之一匹配。如果确实如此，那么我们允许请求继续，否则我们希望发回未经授权的响应。

我们的startup.cs

services.AddAuthorization(options =>
            {
                options.AddPolicy("APIKeyAuth", policyCorrectUser =>
                {
                    policyCorrectUser.Requirements.Add(new APIKeyAuthReq());
                });

            });
services.AddSingleton<Microsoft.AspNetCore.Authorization.IAuthorizationHandler, APIKeyAuthHandler>();

我们的APIKeyAuthHandler.cs

public class APIKeyAuthReq : IAuthorizationRequirement { }

    public class APIKeyAuthHandler : AuthorizationHandler<APIKeyAuthReq>
    {
        protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, APIKeyAuthReq requirement)
        {
            if (context == null)
                throw new ArgumentNullException(nameof(context));
            if (requirement == null)
                throw new ArgumentNullException(nameof(requirement));

            var httpContext = context.Resource as Microsoft.AspNetCore.Mvc.Filters.AuthorizationFilterContext;

            var headers = httpContext.HttpContext.Request.Headers;
            if (headers.TryGetValue("Authorization", out Microsoft.Extensions.Primitives.StringValues value))
            {
                using (DBContext db = new DBContext ())
                {
                    var token = value.First().Split(" ")[1];
                    var login = db.Login.FirstOrDefault(l => l.Apikey == token);
                    if (login == null)
                    {
                        context.Fail();
                        httpContext.HttpContext.Response.StatusCode = 403;
                        return Task.CompletedTask;
                    } else
                    {
                        httpContext.HttpContext.Items.Add("CurrentUser", login);
                        context.Succeed(requirement);
                        return Task.CompletedTask;
                    }
                }
            }
        }
    }

还有我们的controller.cs

    [Route("api/[controller]/[action]")]
    [Authorize("APIKeyAuth")]
    [ApiController]
    public class SomeController : ControllerBase
    {
    }

当有效密钥存在时，一切正常，但当它不存在时，将引发500个内部错误，原因是No authenticationScheme而不是403。

我们对net core（来自net Framework/Forms Authentication）相对较新，因此如果有更准确的方式进行此类身份验证，请让我知道。

错误消息：

无效操作异常：未指定身份验证方案，也未找到默认挑战方案。微软。AspNetCore.认证。身份验证服务。HttpContext上下文，字符串方案，身份验证属性

Answer 1

基于令牌的身份验证是首选。但是，如果您确实需要一个自定义的ApiKeyAuth方案，那么，这是可能的。

首先，似乎Authorize（“APIKeyAuth”）在这里没有意义，因为我们必须在授权之前对用户进行身份验证。当有传入请求时，服务器不知道用户是谁。因此，让我们将ApiKeyAuth从Authorization移动到Authentication。

为此，只需创建一个可用于保存选项的虚拟ApiKeyAuthOpts

public class ApiKeyAuthOpts : AuthenticationSchemeOptions
{
}

和一个简单的ApiKeyAuthHandler来处理身份验证（我只是复制上面的一些代码）：

public class ApiKeyAuthHandler : AuthenticationHandler<ApiKeyAuthOpts>
{
    public ApiKeyAuthHandler(IOptionsMonitor<ApiKeyAuthOpts> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock) 
        : base(options, logger, encoder, clock)
    {
    }
    
    private const string API_TOKEN_PREFIX = "api-key";

    protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        string token = null;
        string authorization = Request.Headers["Authorization"];

        if (string.IsNullOrEmpty(authorization)) {
            return AuthenticateResult.NoResult();
        }

        if (authorization.StartsWith(API_TOKEN_PREFIX, StringComparison.OrdinalIgnoreCase)) {
            token = authorization.Substring(API_TOKEN_PREFIX.Length).Trim();
        }

        if (string.IsNullOrEmpty(token)) {
            return AuthenticateResult.NoResult();
        }
        
        // does the token match ?
        bool res =false; 
        using (DBContext db = new DBContext()) {
            var login = db.Login.FirstOrDefault(l => l.Apikey == token);  // query db
            res = login ==null ? false : true ; 
        }

        if (!res) {
            return AuthenticateResult.Fail($"token {API_TOKEN_PREFIX} not match");
        }
        else {
            var id=new ClaimsIdentity( 
                new Claim[] { new Claim("Key", token) },  // not safe , just as an example , should custom claims on your own
                Scheme.Name 
            );
            ClaimsPrincipal principal=new ClaimsPrincipal( id);
            var ticket = new AuthenticationTicket(principal, new AuthenticationProperties(), Scheme.Name);
            return AuthenticateResult.Success(ticket);
        }
    }
}

最后，我们还需要一些配置来让它们工作：

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    services.AddAuthentication("ApiKeyAuth")
            .AddScheme<ApiKeyAuthOpts,ApiKeyAuthHandler>("ApiKeyAuth","ApiKeyAuth",opts=>{ });
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    // ...
    app.UseAuthentication();
    app.UseHttpsRedirection();
    app.UseMvc();
}

当您向受[Authorize]保护的操作方法发送请求时：

GET https://localhost:44366/api/values/1 HTTP/1.1
Authorization: api-key xxx_yyy_zzz

响应将是HTTP/1.1 200 OK。当您发送没有正确密钥的请求时，响应将是：

HTTP/1.1 401 Unauthorized
Server: Kestrel
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Date: Wed, 12 Sep 2018 08:33:23 GMT
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