CA2144: Transparent code should not load assemblies from byte arrays

Cause

A transparent method loads an assembly from a byte array using one of the following methods:

• Load

• Load

• Load

Rule Description

The security review for transparent code is not as thorough as the security review for critical code, because transparent code cannot perform security sensitive actions. Assemblies loaded from a byte array might not be noticed in transparent code, and that byte array might contain critical, or more importantly safe-critical code, that does need to be audited. Therefore, transparent code should not load assemblies from a byte array.

How to Fix Violations

To fix a violation of this rule, mark the method that is loading the assembly with the SecurityCriticalAttribute or the SecuritySafeCriticalAttribute attribute.

When to Suppress Warnings

Do not suppress a warning from this rule.

Example

The rule fires on the following code because a transparent method loads an assembly from a byte array.

using System;
using System.IO;
using System.Reflection;

namespace TransparencyWarningsDemo
{

    public class TransparentMethodsLoadAssembliesFromByteArraysClass
    {
        public void TransparentMethod()
        {
            byte[] assemblyBytes = File.ReadAllBytes("DependentAssembly.dll");

            // CA2144 violation - transparent code loading an assembly via byte array.  The fix here is to 
            // either make TransparentMethod critical or safe-critical.
            Assembly dependent = Assembly.Load(assemblyBytes);
        }
    }
}