Improving Web Application Security: Threats and - CGISecurity

Chapter 7: Building Secure Assemblies 147Unauthorized Access or Privilege Elevation, or bothThe risk with unauthorized access, which can lead to privilege elevation, is that anunauthorized user or unauthorized code can call your assembly and executeprivileged operations and access restricted resources.VulnerabilitiesVulnerabilities that can lead to unauthorized access and privileged elevation include:● Weak or missing role-based authorization● Internal types and type members are inadvertently exposed● Insecure use of code access security assertions and link demands●Non-sealed and unrestricted base classes, which allow any code to derivefrom themAttacksCommon attacks include:● A luring attack where malicious code accesses your assembly through a trustedintermediary assembly to bypass authorization mechanisms● An attack where malicious code bypasses access controls by directly calling classesthat do not form part of the assembly’s public APICountermeasuresCountermeasures that you can use to prevent unauthorized access and privilegeelevation include:● Use role-based authorization to provide access controls on all public classes andclass members.● Restrict type and member visibility to limit which code is publicly accessible.●●Sandbox privileged code and ensure that calling code is authorized with theappropriate permission demands.Seal non-base classes or restrict inheritance with code access security.Code InjectionWith code injection, an attacker executes arbitrary code using your assembly’sprocess level security context. The risk is increased if your assembly calls unmanagedcode and if your assembly runs under a privileged account.