![]() At the current time, we recommend beginning by enabling compatibility mode enforcement for your application. We are working with our ecosystem developers to clean up any of this behavior. Today, it is recommended to enable your application in compatibility mode, as third-party DLLs may be injected into your process, and subsequently perform return address hijacking. Strict mode, by definition, strictly enforces shadow stack protections and will terminate the process if the intended return address is also not on the shadow stack. Note that all native 64-bit Windows DLLs are compiled with /CETCOMPAT. Note that by default this API can only be called from outside the target process for security purposes. To protect dynamic code in compatibility mode, there is a new API, SetProcessDynamicEnforcedCetCompatibleRanges, to allow you to specify a range of virtual addresses to enforce this mitigation. ![]() This way, you can slowly increase the coverage of the mitigation, by compiling more modules with /CETCOMPAT at your own pace. If either hold true, the execution is allowed to continue. When a return address mismatch occurs in this mode, it is checked to see if 1) it is not in an image binary (from dynamic code) or 2) in a module that is not compiled for /CETCOMPAT. ![]() Compatibility mode provides a more flexible enforcement of shadow stacks, at module granularity. Shadow stack enforcement by default is in compatibility mode. This allows programs with multiple executables with the same name to specify specific processes to enable enforcement. However, if your code behavior includes modifying the return addresses on the stack (which results in mismatch with the shadow stack), then the hijacking code must be removed.Īpplications can also choose to dynamically enable shadow stack enforcement, by using the PROC_THREAD_ATTIBUTE_MITIGATION_POLICY attribute in CreateProcess. Generally, code changes are not needed and the only modification to the binary is a bit in the PE header. To enable shadow stack enforcement on an application, you only need to recompile the application with the /CETCOMPAT linker flag (available in Visual Studio 2019 16.7 Preview 4). Due to these required hardware capabilities only newer processors will have this feature. On supported hardware, call instructions push the return address on both stacks and return instructions compare the values and issues a CPU exception if there is a return address mismatch. Shadow stack is a hardware-enforced read-only memory region that helps keep record of the intended control-flow of the program. ![]() Shadow stack hardens the return address and instruction pointer validation protects exception handling targets. We will describe in detail the two policies in Hardware-enforced Stack Protection: 1) shadow stack 2) instruction pointer validation. More details on ROP and hardware shadow stacks is in this kernel blog.įor user mode applications, this mitigation is opt-in, and the following details are intended to aid developers in understanding how to build protected applications. This technique is known as return-oriented programming (ROP). When attackers find a vulnerability that allows them to overwrite values on the stack, a common exploit technique is to overwrite return addresses into attacker-defined locations to build a malicious payload. This exploit mitigation will protect the return address, and work with other Windows mitigations to prevent exploit techniques that aim to achieve arbitrary code execution. Starting from the 11C latest cumulative update for 20H1 (19041) and 20H2 (19042) versions of Windows 10, we’ve enabled user mode Hardware-enforced Stack Protection for supported hardware. Please see requirements section for hardware and OS requirements to take advantage of Hardware-enforced Stack Protection. Today, we are excited to share the next level of details with our developer community around protecting user-mode applications with this feature. In March 2020, we share d some preliminary information about a new security feature in Windows called Hardware-enforced Stack Protection based on Intel’s Control-flow Enforcement Technology (CET).
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