CA3011: Review code for DLL injection vulnerabilities

#Cause

Potentially untrusted HTTP request input reaches a method that loads an assembly.

By default, this rule analyzes the entire codebase, but this is configurable.

#Rule description

When working with untrusted input, be mindful of loading untrusted code. If your web application loads untrusted code, an attacker may be able to inject malicious DLLs into your process and execute malicious code.

This rule attempts to find input from an HTTP request that reaches a method that loads an assembly.

#How to fix violations

Don't load untrusted DLLs from user input.

#When to suppress warnings

Don't suppress warnings from this rule.

#Configure code to analyze

Use the following options to configure which parts of your codebase to run this rule on.

• Exclude specific symbols
• Exclude specific types and their derived types

You can configure these options for just this rule, for all rules they apply to, or for all rules in this category (Security) that they apply to. For more information, see Code quality rule configuration options.

#Exclude specific symbols

You can exclude specific symbols, such as types and methods, from analysis by setting the excluded_symbol_names option. For example, to specify that the rule should not run on any code within types named MyType, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType

Allowed symbol name formats in the option value (separated by |):

• Symbol name only (includes all symbols with the name, regardless of the containing type or namespace).
• Fully qualified names in the symbol's documentation ID format. Each symbol name requires a symbol-kind prefix, such as M: for methods, T: for types, and N: for namespaces.
• .ctor for constructors and .cctor for static constructors.

Examples:

#Exclude specific types and their derived types

You can exclude specific types and their derived types from analysis by setting the excluded_type_names_with_derived_types option. For example, to specify that the rule should not run on any methods within types named MyType and their derived types, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType

Allowed symbol name formats in the option value (separated by |):

• Type name only (includes all types with the name, regardless of the containing type or namespace).
• Fully qualified names in the symbol's documentation ID format, with an optional T: prefix.

Examples:

#Pseudo-code examples

#Violation

using System;
using System.Reflection;

public partial class WebForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string input = Request.Form["in"];
        byte[] rawAssembly = Convert.FromBase64String(input);
        Assembly.Load(rawAssembly);
    }
}

Imports System
Imports System.Reflection

Public Partial Class WebForm
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(sender As Object, e As EventArgs)
        Dim input As String = Request.Form("in")
        Dim rawAssembly As Byte() = Convert.FromBase64String(input)
        Assembly.Load(rawAssembly)
    End Sub
End Class