在调用Web Serivices时,往往需要身份验证,使得通过验证的用户才能调用你Web Serivices中的方法.当然你可以通过将参数添加到每个需要自定义身份验证方案的Web services方法中去,这需要花费很大的精力.IssueVision 中使用了非常常用而且有效便捷的方法-----使用SoapHeader来实现自定义身份验证数据的传递.
SoapHeader提供了一种方法，用于将数据传递到Web services方法或从Web services方法传递数据，条件是该数据不直接与Web services 方法的主功能相关. 你不用将参数添加到每个需要自定义身份验证方案的Web services 方法，而可以将引用从 SoapHeader 派生的类的 SoapHeaderAttribute 应用于每个Web services 方法。从 SoapHeader 派生的类的实现处理该自定义身份验证方案. IssueVision 就是利用SoapHeader的这种能力来实现自定义身份验证数据传递的.
我们来看一下如何利用SoapHeader来传递数据.
1. 首先需要在服务中定义一个从 SOAPHeader 派生的类,表示传入 SOAP 标头的数据.
IssueVision 在中IssueVisionWeb项目(此项目用于发布Web Services)中通过创建CredentialSoapHeader类来实现第一步.
CredentialSoapHeader.cs
using System.Web.Services.Protocols;
namespace IssueVision.Web
{
public class CredentialSoapHeader : SoapHeader
{
private string m_username;
private string m_password;
public string Username
{
get{ return m_username;}
set{ m_username = value;}
}
public string Password
{
get{ return m_password;}
set{ m_password = value;}
}
}
}
2. 将服务的公共字段声明为该类型,使该SoapHeader在Web Services的公共合同中公开,并在创建代理时可由客户端使用.
IssueVision的Web Services----IssueVisionServices.asmx如此实现.
IssueVisionServices.asmx代码片断:
public class IssueVisionServices : WebService
{
...
private CredentialSoapHeader m_credentials;
// custom SOAP header to pass credentials
public CredentialSoapHeader Credentials
{
get { return m_credentials; }
set { m_credentials = value; }
}
.......
}
3. 在Web Services使用 SoapHeader 自定义属性定义一组关联的标头,服务中的每个 WebMethod 都可以使用.(默认情况下，标头是必需的，但也可以定义可选标头)
IssueVisionServices.asmx代码片断:
....
[WebMethod(Description="Returns the lookup tables for IssueVision.")]
[SoapHeader("Credentials")]
public IVDataSet GetLookupTables()
{
SecurityHelper.VerifyCredentials(this);
return new IVData().GetLookupTables();
}
SecurityHelper类的VerifyCredentials方法用来从Web Services中的SoapHeader类来得到自定义身份验证凭据(如用户名和密码).
SecurityHelper.cs代码片断如下:
// verifies the clients credentials
public static void VerifyCredentials(IssueVisionServices service)
{
if (service.Credentials == null || service.Credentials.Username == null || service.Credentials.Password == null ) //如果没有认证信息,返回SoapException,这样就不能匿名调用Web Method了
{
EventLogHelper.LogFailureAudit("A login was attempted with missing credential information.");
throw new SoapException(string.Empty, SoapException.ClientFaultCode, "Security");
}
string password = Authenticate(service.Credentials);
}
// authenticates a user's credentials passed in a custom SOAP header
private static string Authenticate( CredentialSoapHeader header)
{
DataSet dataSet = new DataSet();
string dbPasswordHash;
try
{
SqlConnection conn = new SqlConnection(Common.ConnectionString);
SqlCommand cmd = new SqlCommand("GetUser", conn);
cmd.Parameters.Add("@UserName", header.Username);
cmd.CommandType = CommandType.StoredProcedure;
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dataSet);
}
catch (Exception ex)
{
EventLogHelper.LogFailureAudit(string.Format("The GetUser stored procedure encounted a problem: {0}", ex.ToString()));
throw new SoapException(string.Empty, SoapException.ServerFaultCode, "Database");
}
// does the user exist?
if (dataSet.Tables[0].Rows.Count == 0)
{
EventLogHelper.LogFailureAudit(string.Format("The username {0} does not exist.", header.Username));
throw new SoapException(string.Empty, SoapException.ClientFaultCode, "Security");
}
else
{
// we found the user, verify the password hash by compare the Salt + PasswordHash
DataRow dataRow = dataSet.Tables[0].Rows[0];
dbPasswordHash = (string)dataRow["PasswordHash"];
string dbPasswordSalt = (string)dataRow["PasswordSalt"];
// create a hash based on the user's salt and the input password
string passwordHash = HashString(dbPasswordSalt + header.Password);
// does the computed hash match the database hash?
if (string.Compare(dbPasswordHash, passwordHash) != 0)
{
EventLogHelper.LogFailureAudit(string.Format("The password for the username {0} was incorrect.", header.Username));
throw new SoapException(string.Empty, SoapException.ClientFaultCode, "Security");
}
}
return dbPasswordHash;
}
4. 最后客户端在调用要求标头的方法之前，需直接在代理类上设置标头.
IssueVision 的SmartClient端的WebServicesLayer类来调用此Web Services
WebServicesLayer.cs程序片断如下:
private static IssueVisionServices GetWebServiceReference(string username, string password)
{
IssueVisionServices dataService = new IssueVisionServices();
//
CredentialSoapHeader header = new CredentialSoapHeader();
header.Username = username;
header.Password = password;
dataService.CredentialSoapHeaderValue = header;
//
InitWebServiceProxy(dataService);
return dataService;
}
通过以上步骤就可以完成Web Services自定义身份验证了.IssueVision中还有很多相关的操作,因为在这里只是讨论一下SoapHeader的用法,就不在列举了.
鄙人见识就这么多了,欢迎大家讨论,提出新的看法.
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