Improving Web Application Security: Threats and - CGISecurity

244 Part III: Building Secure Web ApplicationsEvent LogThe EventLogPermission class is designed to encapsulate the rights of code to accessthe event log. Currently, however, code must be granted full trust to be able to accessthe event log. This means that a medium trust Web application cannot directly accessthe event log. To do so, you must sandbox your event logging code.Accessing the Event LogFirst, ensure that the process account that is used to run your Web application (or thethread identity if your application is impersonating) is able to create event sources.For this, the process or thread identity must be able to create registry keys beneaththe following key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventlogAt minimum, the ASP.NET process identity of any impersonated identity must havethe following permissions on this registry key:● Query key value● Set key value● Create subkey● Enumerate subkeys● Notify● ReadThese settings must be applied to the key shown above and subkeys. Alternatively,you can create event sources at installation time when administrative privileges areavailable. For more information about this approach, see “Auditing and Logging” inChapter 10, “Building Secure ASP.NET Web Pages and Controls.”SandboxingTo sandbox your event logging code, you create a wrapper assembly to encapsulateevent log access. You then install the wrapper assembly in the global assembly cacheso that is granted full trust by code access security policy.