1 files changed, 67 insertions, 0 deletions
diff --git a/rlz/win/lib/lib_mutex.cc b/rlz/win/lib/lib_mutex.cc
new file mode 100644
index 0000000..73dfade
--- /dev/null
+++ b/rlz/win/lib/lib_mutex.cc
@@ -0,0 +1,67 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Mutex to guarantee serialization of RLZ key accesses.
+
+#include "rlz/win/lib/lib_mutex.h"
+
+#include <windows.h>
+#include <Sddl.h>    // For SDDL_REVISION_1, ConvertStringSecurityDescript..
+#include <Aclapi.h>  // For SetSecurityInfo
+
+#include "base/logging.h"
+#include "base/win/windows_version.h"
+
+namespace {
+
+const wchar_t kMutexName[] = L"{A946A6A9-917E-4949-B9BC-6BADA8C7FD63}";
+
+}  // namespace anonymous
+
+namespace rlz_lib {
+
+// Needed to allow synchronization across integrity levels.
+static bool SetObjectToLowIntegrity(HANDLE object,
+    SE_OBJECT_TYPE type = SE_KERNEL_OBJECT) {
+  if (base::win::GetVersion() < base::win::VERSION_VISTA)
+    return true;  // Not needed on XP.
+
+  // The LABEL_SECURITY_INFORMATION SDDL SACL to be set for low integrity.
+  static const wchar_t kLowIntegritySddlSacl[] = L"S:(ML;;NW;;;LW)";
+
+  bool result = false;
+  DWORD error = ERROR_SUCCESS;
+  PSECURITY_DESCRIPTOR security_descriptor = NULL;
+  PACL sacl = NULL;
+  BOOL sacl_present = FALSE;
+  BOOL sacl_defaulted = FALSE;
+
+  if (ConvertStringSecurityDescriptorToSecurityDescriptorW(
+          kLowIntegritySddlSacl, SDDL_REVISION_1, &security_descriptor, NULL)) {
+    if (GetSecurityDescriptorSacl(security_descriptor, &sacl_present,
+            &sacl, &sacl_defaulted)) {
+      error = SetSecurityInfo(object, type, LABEL_SECURITY_INFORMATION,
+                              NULL, NULL, NULL, sacl);
+      result = (ERROR_SUCCESS == error);
+    }
+    LocalFree(security_descriptor);
+  }
+
+  return result;
+}
+
+LibMutex::LibMutex() : acquired_(false), mutex_(NULL) {
+  mutex_ = CreateMutex(NULL, false, kMutexName);
+  bool result = SetObjectToLowIntegrity(mutex_);
+  if (result) {
+    acquired_ = (WAIT_OBJECT_0 == WaitForSingleObject(mutex_, 5000L));
+  }
+}
+
+LibMutex::~LibMutex() {
+  if (acquired_) ReleaseMutex(mutex_);
+  CloseHandle(mutex_);
+}
+
+}  // namespace rlz_lib