Improving Web Application Security: Threats and - CGISecurity

Chapter 12: Building Secure Web Services 341The consumer code that handles potential SoapExceptions follows:try{EmployeeService service = new EmployeeService();Service.GiveBonus(empID,percentage);}catch (System.Web.Services.Protocols.SoapException se){// Extract custom message from se.Detail.InnerTextConsole.WriteLine("Server threw a soap exception" + se.Detail.InnerText );}Application Level Error Handling in Global.asaxASP.NET Web applications commonly handle application level exceptions that areallowed to propagate beyond a method boundary in the Application_Error eventhandler in Global.asax. This feature is not available to Web services, because theWeb service’s HttpHandler captures the exception before it reaches other handlers.If you need application level exception handling, create a custom SOAPextension to handle it. For more information, see MSDN article, “Alteringthe SOAP Message using SOAP Extensions” in the “Building Applications”section of the .NET Framework SDK at http://www.microsoft.com/downloads/details.aspx?FamilyID=9b3a2ca6-3647-4070-9f41-a333c6b9181d&DisplayLang=en.Auditing and LoggingWith a Web service, you can audit and log activity details and transactions either byusing platform-level features or by using custom code in your Web methodimplementations.You can develop code that uses the System.Diagnostics.EventLog class to log actionsto the Windows event log. The permission requirements and techniques for using thisclass from a Web service are the same as for a Web application. For more information,see the “Auditing and Logging” section in Chapter 10, “Building Secure ASP.NETPages and Controls.”Proxy ConsiderationsIf you use WSDL to automatically generate a proxy class to communicate with a Webservice, you should verify the generated code and service endpoints to ensure thatyou communicate with the desired Web service and not a spoofed service. If theWSDL files on a remote server are inadequately secured, it is possible for a malicioususer to tamper with the files and change endpoint addresses, which can impact theproxy code that you generate.