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
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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;}
}
}
}
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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();
//<ReplaceWithWse>
CredentialSoapHeader header = new CredentialSoapHeader();
header.Username = username;
header.Password = password;
dataService.CredentialSoapHeaderValue = header;
//</ReplaceWithWse>
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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