WebAPI的用户身份认证与MVC一样都是通过Attribute进行验证，此处定义了一个抽象基类，子类需要实现根据合作号获取合作用户信息的抽象方法

AbsBaseAuthenticationAttribute

    using System;
    using System.Web;
    using System.Collections.Specialized;
    using System.Net;
    using System.Net.Http;
    using System.Text.RegularExpressions;
    using System.Web.Http.Controllers;
    using System.Web.Http.Filters;

    /// <summary>
    /// WebAPI防篡改签名验证抽象基类Attribute
    /// </summary>
    public abstract class AbsBaseAuthenticationAttribute : ActionFilterAttribute
    {
        /// <summary>
        /// Occurs before the action method is invoked.
        /// </summary>
        /// <param name="actionContext">The action context</param>
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            //获取Asp.Net对应的Request
            var request = ((HttpContextWrapper)actionContext.Request.Properties["MS_HttpContext"]).Request;
            NameValueCollection getCollection = request.QueryString;//此签名要求Partner及Sign均通过QueryString传递
            if (getCollection != null && getCollection.Count > 0)
            {
                string partner = getCollection[SecuritySignHelper.Partner];
                string sign = getCollection[SecuritySignHelper.Sign];
                if (!string.IsNullOrWhiteSpace(partner)//必须包含partner
                   && !string.IsNullOrWhiteSpace(sign)//必须包含sign
                   && Regex.IsMatch(sign, "^[0-9A-Za-z]{32}$"))//sign必须为32位Md5摘要
                {
                    //获取partner对应的key
                    //这里暂时只做了合作key校验，不做访问权限校验，如有需要，此处可进行调整，建议RBAC
                    string partnerKey = this.GetPartnerKey(partner);
                    if (!string.IsNullOrWhiteSpace(partnerKey))
                    {
                        NameValueCollection postCollection = null;
                        switch (request.RequestType.ToUpper())
                        {
                            case "GET": break;//只是为了同时显示restful四种方式才有这部分无意义代码
                            //实际该以哪种方式进行请求应遵循restful标准
                            case "POST":
                            case "PUT":
                            case "DELETE":
                                postCollection = request.Form;//post的数据必须通过application/x-www-form-urlencoded方式传递
                                break;
                            default:
                                throw new NotImplementedException();
                        }
                        //根据请求数据获取MD5签名
                        string vSign = getCollection.GetSecuritySign(partner, partnerKey, postCollection);
                        if (string.Equals(sign, vSign, StringComparison.OrdinalIgnoreCase))
                        {//验证通过,执行基类方法
                            base.OnActionExecuting(actionContext);
                            return;
                        }
                    }
                }
            }
            //此处暂时以401返回，可调整为其它返回
            actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.Unauthorized);
            //actionContext.Response = new HttpResponseMessage(HttpStatusCode.Unauthorized);
        }

        /// <summary>
        /// 获取合作号对应的合作Key,如果未能获取，则返回空字符串或者null
        /// </summary>
        /// <param name="partner"></param>
        /// <returns></returns>
        protected abstract string GetPartnerKey(string partner);
    }

    public class AuthenticationAttribute : AbsBaseAuthenticationAttribute
    {
        protected override string GetPartnerKey(string partner)
        {
            //TODO:从缓存中或者其它地方读取数据
            return "bbb";
        }
    }

    [Authentication]
    public class ApiControllerBase : ApiController
    {
    }

WebAPI 用户认证防篡改实现（二）AbsBaseAuthenticationAttribute