Improving Web Application Security: Threats and - CGISecurity

238 Part III: Building Secure Web ApplicationsDeciding Which Approach to TakeThe right approach depends upon the problem you are trying to solve and whetheror not you have the option of modifying security policy on the Web server.Customizing PolicyThis approach is the easier of the two and does not require any developer effort.However, you might not be permitted to modify policy on the Web server and, incertain scenarios, your code that calls the .NET Framework class library mightrequire full trust. In these situations, you must use sandboxing. For example, thefollowing resources demand full trust, and you must sandbox your resource accesscode when it accesses them:● Event log (through the EventLog class)● OLE DB data sources (through the ADO.NET OLE DB data provider)●●ODBC data sources (through the ADO.NET ODBC .NET data provider)Oracle databases (through the ADO.NET Oracle .NET data provider)Note This list is not exhaustive but it includes commonly used resource types that currently requirefull trust.SandboxingIf you sandbox your privileged application code in a separate assembly, you cangrant additional permissions to the assembly. Alternatively, you can grant it full trustwithout requiring your entire application to run with extended permissions.For example, consider code that uses the ADO.NET OLE DB data provider andinteracts with the System.Data.OleDb.OleDbCommand class. This code requires fulltrust. Although the System.Data.dll assembly is marked withAllowPartiallyTrustedCallersAttribute, the System.Data.OleDb.OleDbCommandclass, among others, cannot be called by partial-trust callers because it is protectedwith a link demand for full trust. To see this, run the following command using thepermview utility from the %windir%\Microsoft.NET\Framework\{version}directory:permview /DECL /OUTPUT System.Data.Perms.txt System.Data.dllThe output in System.Data.Perms.txt includes the following output:class System.Data.OleDb.OleDbCommand LinktimeDemand permission set: