Improving Web Application Security: Threats and - CGISecurity

312 Part III: Building Secure Web Applications(continued)}}catch( Exception ex){// Log exception details.throw new Exception("Failed to credit account balance for customer: " +customerID, ex);}}private void AuditTransaction(string customerID, double amount){// (8) Original caller identity is obtained from call context for// logging purposes.SecurityIdentity caller = SecurityCallContext.CurrentCall.OriginalCaller;try{if (!EventLog.SourceExists(appName)){EventLog.CreateEventSource(appName,eventLog);}StringBuilder logmessage = new StringBuilder();logmessage.AppendFormat("{0}User {1} performed the following transaction"+ "{2} Account balance for customer {3} "+ "credited by {4}",Environment.NewLine, caller.AccountName,Environment.NewLine, customerID, amount);EventLog.WriteEntry(appName, logmessage.ToString(),EventLogEntryType.Information);}catch(SecurityException secex){throw new SecurityException("Event source does not exist and cannot be created", secex);}}The code shown above exhibits the following security characteristics (identified bythe numbers in the comment lines):1. An interface is defined and implemented explicitly to support interface andmethod level authorization with COM+ roles.2. Component level access checks are enabled for the class by using the[ComponentAccessControl] attribute at the class level.3. The [SecurityRole] attribute is used on the CreditAccountBalance method torestrict access to members of the Manager or Senior Managers role.4. Structured exception handling is used to protect implementation. Exceptions arecaught, logged, and an appropriate exception is propagated to the caller.