WebApi接口安全认证
摘要访问认证是一种协议规定的Web服务器用来同网页浏览器进行认证信息协商的方法。它在密码发出前,先对其应用哈希函数,这相对于HTTP基本认证发送明文而言,更安全。从技术上讲,摘要认证是使用随机数来阻止进行密码分析的MD5加密哈希函数应用。它使用HTTP协议。
一、摘要认证基本流程:
1.客户端请求 (无认证)
- GET /dir/index.html HTTP/1.0
- Host: localhost
2.服务器响应
服务端返回401未验证的状态,并且返回WWW-Authenticate信息,包含了验证方式Digest,realm,qop,nonce,opaque的值。其中:
Digest:认证方式;
realm:领域,领域参数是强制的,在所有的盘问中都必须有,它的目的是鉴别SIP消息中的机密,在SIP实际应用中,它通常设置为SIP代理服务器所负责的域名;
qop:保护的质量,这个参数规定服务器支持哪种保护方案,客户端可以从列表中选择一个。值 “auth”表示只进行身份查验, “auth-int”表示进行查验外,还有一些完整性保护。需要看更详细的描述,请参阅RFC2617;
nonce:为一串随机值,在下面的请求中会一直使用到,当过了存活期后服务端将刷新生成一个新的nonce值;
opaque:一个不透明的(不让外人知道其意义)数据字符串,在盘问中发送给用户。
- HTTP/1.0 401 Unauthorized
- Server: HTTPd/0.9
- Date: Sun, 10 Apr 2005 20:26:47 GMT
- WWW-Authenticate: Digest realm="testrealm@host.com",
- qop="auth,auth-int",
- nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
- opaque="5ccc069c403ebaf9f0171e9517f40e41"
3.客户端请求 (用户名 "Mufasa", 密码 "Circle Of Life")
客户端接受到请求返回后,进行HASH运算,返回Authorization参数
其中:realm,nonce,qop由服务器产生;
uri:客户端想要访问的URI;
nc:“现时”计数器,这是一个16进制的数值,即客户端发送出请求的数量(包括当前这个请求),这些请求都使用了当前请求中这个“现时”值。例如,对一个给定的“现时”值,在响应的第一个请求中,客户端将发送“nc=00000001”。这个指示值的目的,是让服务器保持这个计数器的一个副本,以便检测重复的请求。如果这个相同的值看到了两次,则这个请求是重复的;
cnonce:这是一个不透明的字符串值,由客户端提供,并且客户端和服务器都会使用,以避免用明文文本。这使得双方都可以查验对方的身份,并对消息的完整性提供一些保护;
response:这是由用户代理软件计算出的一个字符串,以证明用户知道口令。
- <strong>response计算过程:</strong>
- HA1=MD5(A1)=MD5(username:realm:password)
- 如果 qop 值为“auth”或未指定,那么 HA2 为
- HA2=MD5(A2)=MD5(method:digestURI)
- 如果 qop 值为“auth-int”,那么 HA2 为
- HA2=MD5(A2)=MD5(method:digestURI:MD5(entityBody))
- 如果 qop 值为“auth”或“auth-int”,那么如下计算 response:
- response=MD5(HA1:nonce:nonceCount:clientNonce:qop:HA2)
- 如果 qop 未指定,那么如下计算 response:
- response=MD5(HA1:nonce:HA2)
请求头:
- GET /dir/index.html HTTP/1.0
- Host: localhost
- Authorization: Digest username="Mufasa",
- realm="testrealm@host.com",
- nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
- uri="/dir/index.html",
- qop=auth,
- nc=00000001,
- cnonce="0a4f113b",
- response="6629fae49393a05397450978507c4ef1",
- opaque="5ccc069c403ebaf9f0171e9517f40e41"
4.服务器响应
当服务器接收到摘要响应,也要重新计算响应中各参数的值,并利用客户端提供的参数值,和服务器上存储的口令,进行比对。如果计算结果与收到的客户响应值是相同的,则客户已证明它知道口令,因而客户的身份验证通过。
- HTTP/1.0 200 OK
二、服务端验证
编写一个自定义消息处理器,需要通过System.Net.Http.DelegatingHandler进行派生,并重写SendAsync方法。
- public class AuthenticationHandler : DelegatingHandler
- {
- protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
- {
- try
- {
- HttpRequestHeaders headers = request.Headers;
- if (headers.Authorization != null)
- {
- Header header = new Header(request.Headers.Authorization.Parameter, request.Method.Method);
- if (Nonce.IsValid(header.Nonce, header.NounceCounter))
- {
- // Just assuming password is same as username for the purpose of illustration
- string password = header.UserName;
- string ha1 = String.Format("{0}:{1}:{2}", header.UserName, header.Realm, password).ToMD5Hash();
- string ha2 = String.Format("{0}:{1}", header.Method, header.Uri).ToMD5Hash();
- string computedResponse = String.Format("{0}:{1}:{2}:{3}:{4}:{5}",
- ha1, header.Nonce, header.NounceCounter,header.Cnonce, "auth", ha2).ToMD5Hash();
- if (String.CompareOrdinal(header.Response, computedResponse) == 0)
- {
- // digest computed matches the value sent by client in the response field.
- // Looks like an authentic client! Create a principal.
- var claims = new List<Claim>
- {
- new Claim(ClaimTypes.Name, header.UserName),
- new Claim(ClaimTypes.AuthenticationMethod, AuthenticationMethods.Password)
- };
- ClaimsPrincipal principal = new ClaimsPrincipal(new[] { new ClaimsIdentity(claims, "Digest") });
- Thread.CurrentPrincipal = principal;
- if (HttpContext.Current != null)
- HttpContext.Current.User = principal;
- }
- }
- }
- HttpResponseMessage response = await base.SendAsync(request, cancellationToken);
- if (response.StatusCode == HttpStatusCode.Unauthorized)
- {
- response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue("Digest",Header.UnauthorizedResponseHeader.ToString()));
- }
- return response;
- }
- catch (Exception)
- {
- var response = request.CreateResponse(HttpStatusCode.Unauthorized);
- response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue("Digest",Header.UnauthorizedResponseHeader.ToString()));
- return response;
- }
- }
- }
Header类
- public class Header
- {
- public Header() { }
- public Header(string header, string method)
- {
- string keyValuePairs = header.Replace("\"", String.Empty);
- foreach (string keyValuePair in keyValuePairs.Split(','))
- {
- int index = keyValuePair.IndexOf("=", System.StringComparison.Ordinal);
- string key = keyValuePair.Substring(0, index);
- string value = keyValuePair.Substring(index + 1);
- switch (key)
- {
- case "username": this.UserName = value; break;
- case "realm": this.Realm = value; break;
- case "nonce": this.Nonce = value; break;
- case "uri": this.Uri = value; break;
- case "nc": this.NounceCounter = value; break;
- case "cnonce": this.Cnonce = value; break;
- case "response": this.Response = value; break;
- case "method": this.Method = value; break;
- }
- }
- if (String.IsNullOrEmpty(this.Method))
- this.Method = method;
- }
- public string Cnonce { get; private set; }
- public string Nonce { get; private set; }
- public string Realm { get; private set; }
- public string UserName { get; private set; }
- public string Uri { get; private set; }
- public string Response { get; private set; }
- public string Method { get; private set; }
- public string NounceCounter { get; private set; }
- // This property is used by the handler to generate a
- // nonce and get it ready to be packaged in the
- // WWW-Authenticate header, as part of 401 response
- public static Header UnauthorizedResponseHeader
- {
- get
- {
- return new Header()
- {
- Realm = "MyRealm",
- Nonce = WebApiDemo.Nonce.Generate()
- };
- }
- }
- public override string ToString()
- {
- StringBuilder header = new StringBuilder();
- header.AppendFormat("realm=\"{0}\"", Realm);
- header.AppendFormat(",nonce=\"{0}\"", Nonce);
- header.AppendFormat(",qop=\"{0}\"", "auth");
- return header.ToString();
- }
- }
- public class Nonce
- {
- private static ConcurrentDictionary<string, Tuple<int, DateTime>>
- nonces = new ConcurrentDictionary<string, Tuple<int, DateTime>>();
- public static string Generate()
- {
- byte[] bytes = new byte[16];
- using (var rngProvider = new RNGCryptoServiceProvider())
- {
- rngProvider.GetBytes(bytes);
- }
- string nonce = bytes.ToMD5Hash();
- nonces.TryAdd(nonce, new Tuple<int, DateTime>(0, DateTime.Now.AddMinutes(10)));
- return nonce;
- }
- public static bool IsValid(string nonce, string nonceCount)
- {
- Tuple<int, DateTime> cachedNonce = null;
- //nonces.TryGetValue(nonce, out cachedNonce);
- nonces.TryRemove(nonce, out cachedNonce);//每个nonce只允许使用一次
- if (cachedNonce != null) // nonce is found
- {
- // nonce count is greater than the one in record
- if (Int32.Parse(nonceCount) > cachedNonce.Item1)
- {
- // nonce has not expired yet
- if (cachedNonce.Item2 > DateTime.Now)
- {
- // update the dictionary to reflect the nonce count just received in this request
- //nonces[nonce] = new Tuple<int, DateTime>(Int32.Parse(nonceCount), cachedNonce.Item2);
- // Every thing looks ok - server nonce is fresh and nonce count seems to be
- // incremented. Does not look like replay.
- return true;
- }
- }
- }
- return false;
- }
- }
- [Authorize]
- public class ProductsController : ApiController
- GlobalConfiguration.Configuration.MessageHandlers.Add(
- new AuthenticationHandler());
- public static string Request(string sUrl, string sMethod, string sEntity, string sContentType,
- out string sMessage)
- {
- try
- {
- sMessage = "";
- using (System.Net.WebClient client = new System.Net.WebClient())
- {
- client.Credentials = CreateAuthenticateValue(sUrl);
- client.Headers = CreateHeader(sContentType);
- Uri url = new Uri(sUrl);
- byte[] bytes = Encoding.UTF8.GetBytes(sEntity);
- byte[] buffer;
- switch (sMethod.ToUpper())
- {
- case "GET":
- buffer = client.DownloadData(url);
- break;
- case "POST":
- buffer = client.UploadData(url, "POST", bytes);
- break;
- default:
- buffer = client.UploadData(url, "POST", bytes);
- break;
- }
- return Encoding.UTF8.GetString(buffer);
- }
- }
- catch (WebException ex)
- {
- sMessage = ex.Message;
- var rsp = ex.Response as HttpWebResponse;
- var httpStatusCode = rsp.StatusCode;
- var authenticate = rsp.Headers.Get("WWW-Authenticate");
- return "";
- }
- catch (Exception ex)
- {
- sMessage = ex.Message;
- return "";
- }
- }
- private static CredentialCache CreateAuthenticateValue(string sUrl)
- {
- CredentialCache credentialCache = new CredentialCache();
- credentialCache.Add(new Uri(sUrl), "Digest", new NetworkCredential("Lime", "Lime"));
- return credentialCache;
- }