CA2122: Do not indirectly expose methods with link demands
|
TypeName |
DoNotIndirectlyExposeMethodsWithLinkDemands |
|
CheckId |
CA2122 |
|
Category |
Microsoft.Security |
|
Breaking Change |
Non Breaking |
A public or protected member has a Link Demands and is called by a member that does not perform any security checks.
Add a security Data and Modeling in the .NET Framework or link demand to the member so that it no longer provides unsecured access to the link demand-protected member.
The following examples show a library that violates the rule, and an application that demonstrates the library's weakness. The sample library provides two methods that together violate the rule. The EnvironmentSetting method is secured by a link demand for unrestricted access to environment variables. The DomainInformation method makes no security demands of its callers before it calls EnvironmentSetting.
using System; using System.IO; using System.Security; using System.Security.Permissions; namespace SecurityRulesLibrary { public class DoNotIndirectlyExposeMethodsWithLinkDemands { // Violates rule: DoNotIndirectlyExposeMethodsWithLinkDemands. public static string DomainInformation() { return EnvironmentSetting("USERDNSDOMAIN"); } // Library method with link demand. // This method holds its immediate callers responsible for securing the information. // Because a caller must have unrestricted permission, the method asserts read permission // in case some caller in the stack does not have this permission. [EnvironmentPermissionAttribute(SecurityAction.LinkDemand, Unrestricted=true)] public static string EnvironmentSetting(string environmentVariable) { EnvironmentPermission envPermission = new EnvironmentPermission( EnvironmentPermissionAccess.Read,environmentVariable); envPermission.Assert(); return Environment.GetEnvironmentVariable(environmentVariable); } } }
The following application calls the unsecured library member.
using System; using SecurityRulesLibrary; using System.Security; using System.Security.Permissions; // You have no permission to access the sensitive information, // but you will get data from the unprotected method. [assembly:EnvironmentPermissionAttribute( SecurityAction.RequestRefuse,Unrestricted=true)] namespace TestUnsecuredMembers { class TestUnsecured { [STAThread] static void Main(string[] args) { string value = null; try { value = DoNotIndirectlyExposeMethodsWithLinkDemands.DomainInformation(); } catch (SecurityException e) { Console.WriteLine( "Call to unsecured member was stopped by code access security! {0}", e.Message); throw; } if (value != null) { Console.WriteLine("Value from unsecured member: {0}", value); } } } }
This example produces the following output.
Value from unsecured member: seattle.corp.contoso.com
