Local Privilege Escalation via DYLIB Injection in Native Instruments Native Access

Summary

During the installation of the Native Access application, a privileged helper `com.native-instruments.NativeAccess.Helper2`, which is used by Native Access to trigger functions via XPC communication like copy-file, remove or set-permissions, is deployed as well. The communication with the XPC service of the privileged helper is only allowed if the client process is signed with the corresponding certificate and fulfills the following code signing requirement: "anchor trusted and certificate leaf[subject.CN] = \"Developer ID Application: Native Instruments GmbH (83K5EG6Z9V)\"" The Native Access application was found to be signed with the `com.apple.security.cs.allow-dyld-environment-variables` and `com.apple.security.cs.disable-library-validation` entitlements leading to DYLIB injection and therefore command execution in the context of this application. A low privileged user can exploit the DYLIB injection to trigger functions of the privileged helper XPC service resulting in privilege escalation by first deleting the /etc/sudoers file and then copying a malicious version of that file to /etc/sudoers.