Improving Web Application Security: Threats and Countermeasures

If you develop a partial-trust application or enable an existing application to run at a partial-trust level, and you run into problems because your application is trying to access resources for which the relevant permissions have not been granted, you can use two basic approaches:

• Customize policy

  Customize policy to grant the required permissions to your application. This might not be possible, for example in hosting environments, where policy restrictions are rigid.

• Sandbox privileged code

  Place resource access code in a wrapper assembly, grant the wrapper assembly full trust (not the Web application), and sandbox the permission requirements of privileged code.

The right approach depends on what the problem is. If the problem is related to the fact that you are trying to call a system assembly that does not contain AllowPartiallyTrustedCallersAttribute, the problem becomes how to give a piece of code full trust. In this scenario, you should use the sandboxing approach and grant the sandboxed wrapper assembly full trust.