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# HG changeset patch
# User Bob Owen <bobowencode@gmail.com>
# Date 1611849321 0
# Thu Jan 28 15:55:21 2021 +0000
# Node ID c9195d88e6c67ef2c23c12e307bc16b94d696f50
# Parent 37557864a6845bb8068904e44e8a7dd16746d211
diff --git a/sandbox/win/src/process_mitigations.cc b/sandbox/win/src/process_mitigations.cc
--- a/sandbox/win/src/process_mitigations.cc
+++ b/sandbox/win/src/process_mitigations.cc
@@ -80,16 +80,37 @@ bool IsRunning32bitEmulatedOnArm64() {
if (!retval)
return false;
if (native_machine == IMAGE_FILE_MACHINE_ARM64)
return true;
#endif // defined(ARCH_CPU_X86)
return false;
}
+// Returns true if user-mode Hardware-enforced Stack Protection is available for
+// the Win32 environment.
+bool IsUserCetWin32Available() {
+ static bool cetAvailable = []() -> bool {
+ using IsUserCetAvailableInEnvironmentFunction =
+ decltype(&IsUserCetAvailableInEnvironment);
+
+ IsUserCetAvailableInEnvironmentFunction is_user_cet_available =
+ reinterpret_cast<IsUserCetAvailableInEnvironmentFunction>(
+ ::GetProcAddress(::GetModuleHandleW(L"kernel32.dll"),
+ "IsUserCetAvailableInEnvironment"));
+ if (!is_user_cet_available) {
+ return false;
+ }
+
+ return is_user_cet_available(USER_CET_ENVIRONMENT_WIN32_PROCESS);
+ }();
+
+ return cetAvailable;
+}
+
} // namespace
namespace sandbox {
bool ApplyProcessMitigationsToCurrentProcess(MitigationFlags flags) {
if (!CanSetProcessMitigationsPostStartup(flags))
return false;
@@ -487,16 +508,25 @@ void ConvertProcessMitigationsToPolicy(M
// the underlying hardware does not support the implementation.
// Windows just does its best under the hood for the given hardware.
if (flags & MITIGATION_RESTRICT_INDIRECT_BRANCH_PREDICTION) {
*policy_value_2 |=
PROCESS_CREATION_MITIGATION_POLICY2_RESTRICT_INDIRECT_BRANCH_PREDICTION_ALWAYS_ON;
}
}
+ // Mitigations >= Win10 20H1
+ //----------------------------------------------------------------------------
+ if (version >= base::win::Version::WIN10_20H1) {
+ if (flags & MITIGATION_CET_COMPAT_MODE && IsUserCetWin32Available()) {
+ *policy_value_2 |=
+ PROCESS_CREATION_MITIGATION_POLICY2_CET_USER_SHADOW_STACKS_ALWAYS_ON;
+ }
+ }
+
// When done setting policy flags, sanity check supported policies on this
// machine, and then update |size|.
const ULONG64* supported = GetSupportedMitigations();
*policy_value_1 = *policy_value_1 & supported[0];
*policy_value_2 = *policy_value_2 & supported[1];
diff --git a/sandbox/win/src/security_level.h b/sandbox/win/src/security_level.h
--- a/sandbox/win/src/security_level.h
+++ b/sandbox/win/src/security_level.h
@@ -286,11 +286,15 @@ const MitigationFlags MITIGATION_RESTRIC
// Working down from the high bit to avoid conflict with new upstream flags.
// Disable Control Flow Guard. This may seem more like an anti-mitigation, but
// this flag allows code to make targeted changes to CFG to avoid bugs, while
// leaving it enabled in the common case. Corresponds to
// PROCESS_CREATION_MITIGATION_POLICY_CONTROL_FLOW_GUARD_ALWAYS_ON.
const MitigationFlags MITIGATION_CONTROL_FLOW_GUARD_DISABLE = 0x80000000;
+// This enables CET User Shadow Stack for compatible modules and corresponds to
+// PROCESS_CREATION_MITIGATION_POLICY2_CET_USER_SHADOW_STACKS_ALWAYS_ON.
+const MitigationFlags MITIGATION_CET_COMPAT_MODE = 0x40000000;
+
} // namespace sandbox
#endif // SANDBOX_SRC_SECURITY_LEVEL_H_