WebApi介面安全認證——HTTP之摘要認證
摘要訪問認證是一種協議規定的Web伺服器用來同網頁瀏覽器進行認證資訊協商的方法。它在密碼發出前,先對其應用雜湊函式,這相對於HTTP基本認證傳送明文而言,更安全。從技術上講,摘要認證是使用隨機數來阻止進行密碼分析的MD5加密雜湊函式應用。它使用HTTP協議。
一、摘要認證基本流程:
1.客戶端請求 (無認證)`
GET /dir/index.html HTTP/1.0
Host: localhost
2.伺服器響應
服務端返回401未驗證的狀態,並且返回WWW-Authenticate資訊,包含了驗證方式Digest,realm,qop,nonce,opaque的值。其中:
Digest:認證方式;
realm:領域,領域引數是強制的,在所有的盤問中都必須有,它的目的是鑑別SIP訊息中的機密,在SIP實際應用中,它通常設定為SIP代理伺服器所負責的域名;
qop:保護的質量,這個引數規定伺服器支援哪種保護方案,客戶端可以從列表中選擇一個。值 “auth”表示只進行身份查驗, “auth-int”表示進行查驗外,還有一些完整性保護。需要看更詳細的描述,請參閱RFC2617;
nonce:為一串隨機值,在下面的請求中會一直使用到,當過了存活期後服務端將重新整理生成一個新的nonce值;
opaque:一個不透明的(不讓外人知道其意義)資料字串,在盤問中傳送給使用者。
HTTP/1.0 401 Unauthorized
Server: HTTPd/0.9
Date: Sun, 10 Apr 2005 20:26:47 GMT
WWW-Authenticate: Digest realm="[email protected]",
qop="auth,auth-int",
nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
opaque="5ccc069c403ebaf9f0171e9517f40e41"
3.客戶端請求 (使用者名稱 “Mufasa”, 密碼 “Circle Of Life”)
客戶端接受到請求返回後,進行HASH運算,返回Authorization引數
其中:realm,nonce,qop由伺服器產生;
uri:客戶端想要訪問的URI;
nc:“現時”計數器,這是一個16進位制的數值,即客戶端傳送出請求的數量(包括當前這個請求),這些請求都使用了當前請求中這個“現時”值。例如,對一個給定的“現時”值,在響應的第一個請求中,客戶端將傳送“nc=00000001”。這個指示值的目的,是讓伺服器保持這個計數器的一個副本,以便檢測重複的請求。如果這個相同的值看到了兩次,則這個請求是重複的;
cnonce:這是一個不透明的字串值,由客戶端提供,並且客戶端和伺服器都會使用,以避免用明文文字。這使得雙方都可以查驗對方的身份,並對訊息的完整性提供一些保護;
response:這是由使用者代理軟體計算出的一個字串,以證明使用者知道口令。
<strong>response計算過程:</strong>
HA1=MD5(A1)=MD5(username:realm:password)
如果 qop 值為“auth”或未指定,那麼 HA2 為
HA2=MD5(A2)=MD5(method:digestURI)
如果 qop 值為“auth-int”,那麼 HA2 為
HA2=MD5(A2)=MD5(method:digestURI:MD5(entityBody))
如果 qop 值為“auth”或“auth-int”,那麼如下計算 response:
response=MD5(HA1:nonce:nonceCount:clientNonce:qop:HA2)
如果 qop 未指定,那麼如下計算 response:
response=MD5(HA1:nonce:HA2)
請求頭:
GET /dir/index.html HTTP/1.0
Host: localhost
Authorization: Digest username="Mufasa",
realm="[email protected]",
nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
uri="/dir/index.html",
qop=auth,
nc=00000001,
cnonce="0a4f113b",
response="6629fae49393a05397450978507c4ef1",
opaque="5ccc069c403ebaf9f0171e9517f40e41"
4.伺服器響應
當伺服器接收到摘要響應,也要重新計算響應中各引數的值,並利用客戶端提供的引數值,和伺服器上儲存的口令,進行比對。如果計算結果與收到的客戶響應值是相同的,則客戶已證明它知道口令,因而客戶的身份驗證通過。
HTTP/1.0 200 OK
二、服務端驗證
編寫一個自定義訊息處理器,需要通過System.Net.Http.DelegatingHandler進行派生,並重寫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類:
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();
}
}
nonce類:
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);//每個nonce只允許使用一次
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;
}
}
需要使用摘要驗證可在程式碼裡新增Attribute [Authorize],如:
[Authorize]
public class ProductsController : ApiController
最後Global.asax裡需註冊下:
GlobalConfiguration.Configuration.MessageHandlers.Add(
new AuthenticationHandler());
三、客戶端的呼叫
這裡主要說明使用WebClient呼叫
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 "";
}
}
關鍵程式碼,在這裡新增使用者認證,使用NetworkCredential:
private static CredentialCache CreateAuthenticateValue(string sUrl)
{
CredentialCache credentialCache = new CredentialCache();
credentialCache.Add(new Uri(sUrl), "Digest", new NetworkCredential("Lime", "Lime"));
return credentialCache;
}