optree

Problem

Software license is a legal instrument that governs the use and distribution of software source code and its binary representation. Software publishers have the freedom to choose any commonly used or purposefully written license to publish their work under. While some licenses are liberal and allow almost any kind of distribution, with or without code modification, other licenses are more restrictive and impose rules for their inclusion in other software projects. Some software licenses place restrictions on software distribution of the code they apply to. These restrictions may extend to the services built upon the code licensed under such restrictive licenses. Some restrictive licenses explicitly state that the licensee may not provide the software to third parties as a hosted or managed service, where the service provides users with access to any substantial set of the features or functionality of the licensed software. When building commercial applications, this is typically undesirable. Therefore, the inclusion of any code that may impose limits on software distribution is commonly avoided or even prohibited by the organization policy.

Problem

Control Flow Guard (CFG/CFI) protects the code flow integrity by ensuring that dynamic calls are made only to vetted functions. Trusted execution paths rely on the ability of the operating system to build a list of valid function targets. Certain functions can intentionally be disallowed to prevent malicious code from deactivating vulnerability mitigation features. A list of such invalid function targets can include publicly exported symbols. Applications that enhance control flow integrity through export suppression rely on libraries to mark their publicly visible symbols as suppressed. This is done for all symbols that are considered to be sensitive functions, and to which access should be restricted. It is considered dangerous to mix applications that perform export suppression with libraries that do not.

Problem

Control Flow Guard (CFG/CFI) protects the code flow integrity by ensuring that indirect calls are made only to vetted functions. This mitigation protects dynamically resolved function targets by instrumenting the code responsible for transferring execution control. Higher-level programming languages implement structured exception handling by managing their own code flow execution paths. As such, they are subject to code flow hijacking during runtime. Language-specific exception handling mitigation enforces execution integrity by instrumenting calls to manage execution context switching. Any deviation from the known and trusted code flow paths will cause the application to terminate. This makes malicious code less likely to execute.