1 files changed, 589 insertions, 0 deletions
diff --git a/uriloader/exthandler/win/nsOSHelperAppService.cpp b/uriloader/exthandler/win/nsOSHelperAppService.cpp
new file mode 100644
index 0000000000..48c5ec64d8
--- /dev/null
+++ b/uriloader/exthandler/win/nsOSHelperAppService.cpp
@@ -0,0 +1,589 @@
+/* -*- Mode: C++; tab-width: 3; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim:set ts=2 sts=2 sw=2 et cin:
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsComponentManagerUtils.h"
+#include "nsOSHelperAppService.h"
+#include "nsISupports.h"
+#include "nsString.h"
+#include "nsIMIMEInfo.h"
+#include "nsMIMEInfoWin.h"
+#include "nsMimeTypes.h"
+#include "plstr.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsLocalFile.h"
+#include "nsIWindowsRegKey.h"
+#include "nsXULAppAPI.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/WindowsVersion.h"
+
+// shellapi.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <shellapi.h>
+#include <shlwapi.h>
+
+#define LOG(args) MOZ_LOG(mLog, mozilla::LogLevel::Debug, args)
+
+// helper methods: forward declarations...
+static nsresult GetExtensionFromWindowsMimeDatabase(const nsACString& aMimeType,
+                                                    nsString& aFileExtension);
+
+nsOSHelperAppService::nsOSHelperAppService()
+    : nsExternalHelperAppService(), mAppAssoc(nullptr) {
+  CoInitialize(nullptr);
+  CoCreateInstance(CLSID_ApplicationAssociationRegistration, nullptr,
+                   CLSCTX_INPROC, IID_IApplicationAssociationRegistration,
+                   (void**)&mAppAssoc);
+}
+
+nsOSHelperAppService::~nsOSHelperAppService() {
+  if (mAppAssoc) mAppAssoc->Release();
+  mAppAssoc = nullptr;
+  CoUninitialize();
+}
+
+// The windows registry provides a mime database key which lists a set of mime
+// types and corresponding "Extension" values. we can use this to look up our
+// mime type to see if there is a preferred extension for the mime type.
+static nsresult GetExtensionFromWindowsMimeDatabase(const nsACString& aMimeType,
+                                                    nsString& aFileExtension) {
+  nsAutoString mimeDatabaseKey;
+  mimeDatabaseKey.AssignLiteral("MIME\\Database\\Content Type\\");
+
+  AppendASCIItoUTF16(aMimeType, mimeDatabaseKey);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, mimeDatabaseKey,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+
+  if (NS_SUCCEEDED(rv))
+    regKey->ReadStringValue(u"Extension"_ns, aFileExtension);
+
+  return NS_OK;
+}
+
+nsresult nsOSHelperAppService::OSProtocolHandlerExists(
+    const char* aProtocolScheme, bool* aHandlerExists) {
+  // look up the protocol scheme in the windows registry....if we find a match
+  // then we have a handler for it...
+  *aHandlerExists = false;
+  if (aProtocolScheme && *aProtocolScheme) {
+    NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+    wchar_t* pResult = nullptr;
+    NS_ConvertASCIItoUTF16 scheme(aProtocolScheme);
+    // We are responsible for freeing returned strings.
+    HRESULT hr = mAppAssoc->QueryCurrentDefault(scheme.get(), AT_URLPROTOCOL,
+                                                AL_EFFECTIVE, &pResult);
+    if (SUCCEEDED(hr)) {
+      CoTaskMemFree(pResult);
+      nsCOMPtr<nsIWindowsRegKey> regKey =
+          do_CreateInstance("@mozilla.org/windows-registry-key;1");
+      if (!regKey) {
+        return NS_ERROR_NOT_AVAILABLE;
+      }
+
+      nsresult rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                                 nsDependentString(scheme.get()),
+                                 nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+      if (NS_FAILED(rv)) {
+        // Open will fail if the registry key path doesn't exist.
+        return NS_OK;
+      }
+
+      bool hasValue;
+      rv = regKey->HasValue(u"URL Protocol"_ns, &hasValue);
+      if (NS_FAILED(rv)) {
+        return NS_ERROR_FAILURE;
+      }
+      if (!hasValue) {
+        return NS_OK;
+      }
+
+      *aHandlerExists = true;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsOSHelperAppService::GetApplicationDescription(
+    const nsACString& aScheme, nsAString& _retval) {
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  NS_ConvertASCIItoUTF16 buf(aScheme);
+
+  if (mozilla::IsWin8OrLater()) {
+    wchar_t result[1024];
+    DWORD resultSize = 1024;
+    HRESULT hr = AssocQueryString(0x1000 /* ASSOCF_IS_PROTOCOL */,
+                                  ASSOCSTR_FRIENDLYAPPNAME, buf.get(), NULL,
+                                  result, &resultSize);
+    if (SUCCEEDED(hr)) {
+      _retval = result;
+      return NS_OK;
+    }
+  }
+
+  NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+  wchar_t* pResult = nullptr;
+  // We are responsible for freeing returned strings.
+  HRESULT hr = mAppAssoc->QueryCurrentDefault(buf.get(), AT_URLPROTOCOL,
+                                              AL_EFFECTIVE, &pResult);
+  if (SUCCEEDED(hr)) {
+    nsCOMPtr<nsIFile> app;
+    nsAutoString appInfo(pResult);
+    CoTaskMemFree(pResult);
+    if (NS_SUCCEEDED(GetDefaultAppInfo(appInfo, _retval, getter_AddRefs(app))))
+      return NS_OK;
+  }
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP nsOSHelperAppService::IsCurrentAppOSDefaultForProtocol(
+    const nsACString& aScheme, bool* _retval) {
+  *_retval = false;
+
+  NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+
+  NS_ConvertASCIItoUTF16 buf(aScheme);
+
+  // Find the progID
+  wchar_t* pResult = nullptr;
+  HRESULT hr = mAppAssoc->QueryCurrentDefault(buf.get(), AT_URLPROTOCOL,
+                                              AL_EFFECTIVE, &pResult);
+  if (FAILED(hr)) {
+    return NS_ERROR_FAILURE;
+  }
+  nsAutoString progID(pResult);
+  // We are responsible for freeing returned strings.
+  CoTaskMemFree(pResult);
+
+  // Find the default executable.
+  nsAutoString description;
+  nsCOMPtr<nsIFile> appFile;
+  nsresult rv = GetDefaultAppInfo(progID, description, getter_AddRefs(appFile));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  // Determine if the default executable is our executable.
+  nsCOMPtr<nsIFile> ourBinary;
+  XRE_GetBinaryPath(getter_AddRefs(ourBinary));
+  bool isSame = false;
+  rv = appFile->Equals(ourBinary, &isSame);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  *_retval = isSame;
+  return NS_OK;
+}
+
+// GetMIMEInfoFromRegistry: This function obtains the values of some of the
+// nsIMIMEInfo attributes for the mimeType/extension associated with the input
+// registry key.  The default entry for that key is the name of a registry key
+// under HKEY_CLASSES_ROOT.  The default value for *that* key is the descriptive
+// name of the type.  The EditFlags value is a binary value; the low order bit
+// of the third byte of which indicates that the user does not need to be
+// prompted.
+//
+// This function sets only the Description attribute of the input nsIMIMEInfo.
+/* static */
+nsresult nsOSHelperAppService::GetMIMEInfoFromRegistry(const nsString& fileType,
+                                                       nsIMIMEInfo* pInfo) {
+  nsresult rv = NS_OK;
+
+  NS_ENSURE_ARG(pInfo);
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileType,
+                    nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+  // OK, the default value here is the description of the type.
+  nsAutoString description;
+  rv = regKey->ReadStringValue(u""_ns, description);
+  if (NS_SUCCEEDED(rv)) pInfo->SetDescription(description);
+
+  return NS_OK;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////////////
+// method overrides used to gather information from the windows registry for
+// various mime types.
+////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Looks up the type for the extension aExt and compares it to aType
+/* static */
+bool nsOSHelperAppService::typeFromExtEquals(const char16_t* aExt,
+                                             const char* aType) {
+  if (!aType) return false;
+  nsAutoString fileExtToUse;
+  if (aExt[0] != char16_t('.')) fileExtToUse = char16_t('.');
+
+  fileExtToUse.Append(aExt);
+
+  bool eq = false;
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return eq;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileExtToUse,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return eq;
+
+  nsAutoString type;
+  rv = regKey->ReadStringValue(u"Content Type"_ns, type);
+  if (NS_SUCCEEDED(rv)) eq = type.LowerCaseEqualsASCII(aType);
+
+  return eq;
+}
+
+// The "real" name of a given helper app (as specified by the path to the
+// executable file held in various registry keys) is stored n the VERSIONINFO
+// block in the file's resources. We need to find the path to the executable
+// and then retrieve the "FileDescription" field value from the file.
+nsresult nsOSHelperAppService::GetDefaultAppInfo(
+    const nsAString& aAppInfo, nsAString& aDefaultDescription,
+    nsIFile** aDefaultApplication) {
+  nsAutoString handlerCommand;
+
+  // If all else fails, use the file type key name, which will be
+  // something like "pngfile" for .pngs, "WMVFile" for .wmvs, etc.
+  aDefaultDescription = aAppInfo;
+  *aDefaultApplication = nullptr;
+
+  if (aAppInfo.IsEmpty()) return NS_ERROR_FAILURE;
+
+  // aAppInfo may be a file, file path, program id, or
+  // Applications reference -
+  // c:\dir\app.exe
+  // Applications\appfile.exe/dll (shell\open...)
+  // ProgID.progid (shell\open...)
+
+  nsAutoString handlerKeyName(aAppInfo);
+
+  nsCOMPtr<nsIWindowsRegKey> chkKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!chkKey) return NS_ERROR_FAILURE;
+
+  nsresult rv =
+      chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, handlerKeyName,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) {
+    // It's a file system path to a handler
+    handlerCommand.Assign(aAppInfo);
+  } else {
+    handlerKeyName.AppendLiteral("\\shell\\open\\command");
+    nsCOMPtr<nsIWindowsRegKey> regKey =
+        do_CreateInstance("@mozilla.org/windows-registry-key;1");
+    if (!regKey) return NS_ERROR_FAILURE;
+
+    nsresult rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, handlerKeyName,
+                     nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+    // OK, the default value here is the description of the type.
+    rv = regKey->ReadStringValue(u""_ns, handlerCommand);
+    if (NS_FAILED(rv)) {
+      // Check if there is a DelegateExecute string
+      nsAutoString delegateExecute;
+      rv = regKey->ReadStringValue(u"DelegateExecute"_ns, delegateExecute);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      // Look for InProcServer32
+      nsAutoString delegateExecuteRegPath;
+      delegateExecuteRegPath.AssignLiteral("CLSID\\");
+      delegateExecuteRegPath.Append(delegateExecute);
+      delegateExecuteRegPath.AppendLiteral("\\InProcServer32");
+      rv = chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                        delegateExecuteRegPath,
+                        nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+      if (NS_SUCCEEDED(rv)) {
+        rv = chkKey->ReadStringValue(u""_ns, handlerCommand);
+      }
+
+      if (NS_FAILED(rv)) {
+        // Look for LocalServer32
+        delegateExecuteRegPath.AssignLiteral("CLSID\\");
+        delegateExecuteRegPath.Append(delegateExecute);
+        delegateExecuteRegPath.AppendLiteral("\\LocalServer32");
+        rv = chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                          delegateExecuteRegPath,
+                          nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+        NS_ENSURE_SUCCESS(rv, rv);
+        rv = chkKey->ReadStringValue(u""_ns, handlerCommand);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+    }
+  }
+
+  // XXX FIXME: If this fails, the UI will display the full command
+  // string.
+  // There are some rare cases this can happen - ["url.dll" -foo]
+  // for example won't resolve correctly to the system dir. The
+  // subsequent launch of the helper app will work though.
+  nsCOMPtr<nsILocalFileWin> lf = new nsLocalFile();
+  rv = lf->InitWithCommandLine(handlerCommand);
+  NS_ENSURE_SUCCESS(rv, rv);
+  lf.forget(aDefaultApplication);
+
+  wchar_t friendlyName[1024];
+  DWORD friendlyNameSize = 1024;
+  HRESULT hr = AssocQueryString(ASSOCF_NONE, ASSOCSTR_FRIENDLYAPPNAME,
+                                PromiseFlatString(aAppInfo).get(), NULL,
+                                friendlyName, &friendlyNameSize);
+  if (SUCCEEDED(hr) && friendlyNameSize > 1) {
+    aDefaultDescription.Assign(friendlyName, friendlyNameSize - 1);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<nsMIMEInfoWin> nsOSHelperAppService::GetByExtension(
+    const nsString& aFileExt, const char* aTypeHint) {
+  if (aFileExt.IsEmpty()) return nullptr;
+
+  // Determine the mime type.
+  nsAutoCString typeToUse;
+  if (aTypeHint && *aTypeHint) {
+    typeToUse.Assign(aTypeHint);
+  } else if (!GetMIMETypeFromOSForExtension(NS_ConvertUTF16toUTF8(aFileExt),
+                                            typeToUse)) {
+    return nullptr;
+  }
+
+  RefPtr<nsMIMEInfoWin> mimeInfo = new nsMIMEInfoWin(typeToUse);
+
+  // windows registry assumes your file extension is going to include the '.',
+  // but our APIs expect it to not be there, so make sure we normalize that bit.
+  nsAutoString fileExtToUse;
+  if (aFileExt.First() != char16_t('.')) fileExtToUse = char16_t('.');
+
+  fileExtToUse.Append(aFileExt);
+
+  // don't append the '.' for our APIs.
+  nsAutoCString lowerFileExt =
+      NS_ConvertUTF16toUTF8(Substring(fileExtToUse, 1));
+  ToLowerCase(lowerFileExt);
+  mimeInfo->AppendExtension(lowerFileExt);
+  mimeInfo->SetPreferredAction(nsIMIMEInfo::useSystemDefault);
+
+  nsAutoString appInfo;
+  bool found;
+
+  // Retrieve the default application for this extension
+  NS_ENSURE_TRUE(mAppAssoc, nullptr);
+  nsString assocType(fileExtToUse);
+  wchar_t* pResult = nullptr;
+  HRESULT hr = mAppAssoc->QueryCurrentDefault(assocType.get(), AT_FILEEXTENSION,
+                                              AL_EFFECTIVE, &pResult);
+  if (SUCCEEDED(hr)) {
+    found = true;
+    appInfo.Assign(pResult);
+    CoTaskMemFree(pResult);
+  } else {
+    found = false;
+  }
+
+  // Bug 358297 - ignore the default handler, force the user to choose app
+  if (appInfo.EqualsLiteral("XPSViewer.Document")) found = false;
+
+  if (!found) {
+    return nullptr;
+  }
+
+  // Get other nsIMIMEInfo fields from registry, if possible.
+  nsAutoString defaultDescription;
+  nsCOMPtr<nsIFile> defaultApplication;
+
+  if (NS_FAILED(GetDefaultAppInfo(appInfo, defaultDescription,
+                                  getter_AddRefs(defaultApplication)))) {
+    return nullptr;
+  }
+
+  mimeInfo->SetDefaultDescription(defaultDescription);
+  mimeInfo->SetDefaultApplicationHandler(defaultApplication);
+
+  // Grab the general description
+  GetMIMEInfoFromRegistry(appInfo, mimeInfo);
+
+  return mimeInfo.forget();
+}
+
+NS_IMETHODIMP
+nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
+                                        const nsACString& aFileExt,
+                                        bool* aFound, nsIMIMEInfo** aMIMEInfo) {
+  *aFound = false;
+
+  const nsCString& flatType = PromiseFlatCString(aMIMEType);
+  nsAutoString fileExtension;
+  CopyUTF8toUTF16(aFileExt, fileExtension);
+
+  /* XXX The octet-stream check is a gross hack to wallpaper over the most
+   * common Win32 extension issues caused by the fix for bug 116938.  See bug
+   * 120327, comment 271 for why this is needed.  Not even sure we
+   * want to remove this once we have fixed all this stuff to work
+   * right; any info we get from the OS on this type is pretty much
+   * useless....
+   */
+  bool haveMeaningfulMimeType =
+      !aMIMEType.IsEmpty() &&
+      !aMIMEType.LowerCaseEqualsLiteral(APPLICATION_OCTET_STREAM);
+  LOG(("Extension lookup on '%s' with mimetype '%s'%s\n", fileExtension.get(),
+       flatType.get(),
+       haveMeaningfulMimeType ? " (treated as meaningful)" : ""));
+
+  RefPtr<nsMIMEInfoWin> mi;
+
+  // We should have *something* to go on here.
+  nsAutoString extensionFromMimeType;
+  if (haveMeaningfulMimeType) {
+    GetExtensionFromWindowsMimeDatabase(aMIMEType, extensionFromMimeType);
+  }
+  if (fileExtension.IsEmpty() && extensionFromMimeType.IsEmpty()) {
+    // Without an extension from the mimetype or the file, we can't
+    // do anything here.
+    mi = new nsMIMEInfoWin(flatType.get());
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+
+  // Either fileExtension or extensionFromMimeType must now be non-empty.
+
+  *aFound = true;
+
+  // On Windows, we prefer the file extension for lookups over the mimetype,
+  // because that's how windows does things.
+  // If we have no file extension or it doesn't match the mimetype, use the
+  // mime type's default file extension instead.
+  bool usedMimeTypeExtensionForLookup = false;
+  if (fileExtension.IsEmpty() ||
+      (!extensionFromMimeType.IsEmpty() &&
+       !typeFromExtEquals(fileExtension.get(), flatType.get()))) {
+    usedMimeTypeExtensionForLookup = true;
+    fileExtension = extensionFromMimeType;
+    LOG(("Now using '%s' mimetype's default file extension '%s' for lookup\n",
+         flatType.get(), fileExtension.get()));
+  }
+
+  // If we have an extension, use it for lookup:
+  mi = GetByExtension(fileExtension, flatType.get());
+  LOG(("Extension lookup on '%s' found: 0x%p\n", fileExtension.get(),
+       mi.get()));
+
+  if (mi) {
+    bool hasDefault = false;
+    mi->GetHasDefaultHandler(&hasDefault);
+    // If we don't find a default handler description, see if we can find one
+    // using the mimetype.
+    if (!hasDefault && !usedMimeTypeExtensionForLookup) {
+      RefPtr<nsMIMEInfoWin> miFromMimeType =
+          GetByExtension(extensionFromMimeType, flatType.get());
+      LOG(("Mime-based ext. lookup for '%s' found 0x%p\n",
+           extensionFromMimeType.get(), miFromMimeType.get()));
+      if (miFromMimeType) {
+        nsAutoString desc;
+        miFromMimeType->GetDefaultDescription(desc);
+        mi->SetDefaultDescription(desc);
+      }
+    }
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+
+  // The extension didn't work. Try the extension from the mimetype if
+  // different:
+  if (!extensionFromMimeType.IsEmpty() && !usedMimeTypeExtensionForLookup) {
+    mi = GetByExtension(extensionFromMimeType, flatType.get());
+    LOG(("Mime-based ext. lookup for '%s' found 0x%p\n",
+         extensionFromMimeType.get(), mi.get()));
+  }
+  if (mi) {
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+  // This didn't work either, so just return an empty dummy mimeinfo.
+  *aFound = false;
+  mi = new nsMIMEInfoWin(flatType.get());
+  // If we didn't resort to the mime type's extension, we must have had a
+  // valid extension, so stick its lowercase version on the mime info.
+  if (!usedMimeTypeExtensionForLookup) {
+    nsAutoCString lowerFileExt;
+    ToLowerCase(aFileExt, lowerFileExt);
+    mi->AppendExtension(lowerFileExt);
+  }
+  mi.forget(aMIMEInfo);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsOSHelperAppService::GetProtocolHandlerInfoFromOS(const nsACString& aScheme,
+                                                   bool* found,
+                                                   nsIHandlerInfo** _retval) {
+  NS_ASSERTION(!aScheme.IsEmpty(), "No scheme was specified!");
+
+  nsresult rv =
+      OSProtocolHandlerExists(nsPromiseFlatCString(aScheme).get(), found);
+  if (NS_FAILED(rv)) return rv;
+
+  nsMIMEInfoWin* handlerInfo =
+      new nsMIMEInfoWin(aScheme, nsMIMEInfoBase::eProtocolInfo);
+  NS_ENSURE_TRUE(handlerInfo, NS_ERROR_OUT_OF_MEMORY);
+  NS_ADDREF(*_retval = handlerInfo);
+
+  if (!*found) {
+    // Code that calls this requires an object regardless if the OS has
+    // something for us, so we return the empty object.
+    return NS_OK;
+  }
+
+  nsAutoString desc;
+  GetApplicationDescription(aScheme, desc);
+  handlerInfo->SetDefaultDescription(desc);
+
+  return NS_OK;
+}
+
+bool nsOSHelperAppService::GetMIMETypeFromOSForExtension(
+    const nsACString& aExtension, nsACString& aMIMEType) {
+  if (aExtension.IsEmpty()) return false;
+
+  // windows registry assumes your file extension is going to include the '.'.
+  // so make sure it's there...
+  nsAutoString fileExtToUse;
+  if (aExtension.First() != '.') fileExtToUse = char16_t('.');
+
+  AppendUTF8toUTF16(aExtension, fileExtToUse);
+
+  // Try to get an entry from the windows registry.
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return false;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileExtToUse,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  nsAutoString mimeType;
+  if (NS_FAILED(regKey->ReadStringValue(u"Content Type"_ns, mimeType)) ||
+      mimeType.IsEmpty()) {
+    return false;
+  }
+  // Content-Type is always in ASCII
+  aMIMEType.Truncate();
+  LossyAppendUTF16toASCII(mimeType, aMIMEType);
+  return true;
+}