Bug 1751367: Delay loading winmm.dll, so it loads after COM initialization. r=cmartin,media-playback-reviewers,alwu

This is to prevent user32.dll from loading before COM initialization on earlier
version of windows.

Differential Revision: https://phabricator.services.mozilla.com/D136936

dom/media/gmp/GMPChild.cpp

@@ -212,6 +212,7 @@ mozilla::ipc::IPCResult GMPChild::RecvPreloadLibs(const nsCString& aLibs) {
       u"ole32.dll",        // required for OPM
       u"psapi.dll",        // For GetMappedFileNameW, see bug 1383611
       u"softokn3.dll",     // NSS for clearkey CDM
+      u"winmm.dll",        // Dependency for widevine
   };
   constexpr static bool (*IsASCII)(const char16_t*) =
       IsAsciiNullTerminated<char16_t>;

dom/media/gmp/GMPParent.cpp

@@ -907,7 +907,7 @@ RefPtr<GenericPromise> GMPParent::ParseChromiumManifest(
 #if XP_WIN
     // psapi.dll added for GetMappedFileNameW, which could possibly be avoided
     // in future versions, see bug 1383611 for details.
-    mLibs = "dxva2.dll, ole32.dll, psapi.dll"_ns;
+    mLibs = "dxva2.dll, ole32.dll, psapi.dll, winmm.dll"_ns;
 #endif
   } else if (mDisplayName.EqualsASCII("fake")) {
     // The fake CDM just exposes a key system with id "fake".

ipc/glue/UtilityProcessImpl.cpp

@@ -23,6 +23,10 @@ UtilityProcessImpl::~UtilityProcessImpl() { mUtility = nullptr; }
 
 bool UtilityProcessImpl::Init(int aArgc, char* aArgv[]) {
 #if defined(MOZ_SANDBOX) && defined(OS_WIN)
+  // We delay load winmm.dll so that its dependencies don't interfere with COM
+  // initialization when win32k is locked down. We need to load it before we
+  // lower the sandbox in processes where the policy will prevent loading.
+  ::LoadLibraryW(L"winmm.dll");
   mozilla::SandboxTarget::Instance()->StartSandbox();
 #endif
 

security/moz.build

@@ -145,6 +145,11 @@ if CONFIG["OS_TARGET"] == "WINNT":
     if CONFIG["CPU_ARCH"] == "x86":
         # This should really be the default.
         sandbox_vars["ASFLAGS"] = ["-safeseh"]
+
+    DELAYLOAD_DLLS += [
+        "winmm.dll",
+    ]
+
 if CONFIG["OS_TARGET"] == "Android":
     sandbox_vars["CFLAGS"] = [
         "-include",

toolkit/library/moz.build

@@ -53,6 +53,7 @@ def Libxul(name, output_category=None):
         "usp10.dll",
         "uxtheme.dll",
         "wininet.dll",
+        "winmm.dll",
         "winspool.drv",
         "wtsapi32.dll",
     ]