Bug 1413868.

4 files changed, 311 insertions, 0 deletions

diff --git a/xpcom/io/FilePreferences.cpp b/xpcom/io/FilePreferences.cpp
new file mode 100644
index 000000000..ef942beb2
--- /dev/null
+++ b/xpcom/io/FilePreferences.cpp
@@ -0,0 +1,272 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "FilePreferences.h"
+
+#include "mozilla/Preferences.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsString.h"
+
+namespace mozilla {
+namespace FilePreferences {
+
+static bool sBlockUNCPaths = false;
+typedef nsTArray<nsString> Paths;
+
+static Paths& PathArray()
+{
+  static Paths sPaths;
+  return sPaths;
+}
+
+static void AllowDirectory(char const* directory)
+{
+  nsCOMPtr<nsIFile> file;
+  NS_GetSpecialDirectory(directory, getter_AddRefs(file));
+  if (!file) {
+    return;
+  }
+
+  nsString path;
+  if (NS_FAILED(file->GetTarget(path))) {
+    return;
+  }
+
+  // The whitelist makes sense only for UNC paths, because this code is used
+  // to block only UNC paths, hence, no need to add non-UNC directories here
+  // as those would never pass the check.
+  if (!StringBeginsWith(path, NS_LITERAL_STRING("\\\\"))) {
+    return;
+  }
+
+  if (!PathArray().Contains(path)) {
+    PathArray().AppendElement(path);
+  }
+}
+
+void InitPrefs()
+{
+  sBlockUNCPaths = Preferences::GetBool("network.file.disable_unc_paths", false);
+}
+
+void InitDirectoriesWhitelist()
+{
+  // NS_GRE_DIR is the installation path where the binary resides.
+  AllowDirectory(NS_GRE_DIR);
+  // NS_APP_USER_PROFILE_50_DIR and NS_APP_USER_PROFILE_LOCAL_50_DIR are the two
+  // parts of the profile we store permanent and local-specific data.
+  AllowDirectory(NS_APP_USER_PROFILE_50_DIR);
+  AllowDirectory(NS_APP_USER_PROFILE_LOCAL_50_DIR);
+}
+
+namespace { // anon
+
+class Normalizer
+{
+public:
+  Normalizer(const nsAString& aFilePath, const char16_t aSeparator);
+  bool Get(nsAString& aNormalizedFilePath);
+
+private:
+  bool ConsumeItem();
+  bool ConsumeSeparator();
+  bool IsEOF() { return mFilePathCursor == mFilePathEnd; }
+
+  bool ConsumeName();
+  bool CheckParentDir();
+  bool CheckCurrentDir();
+
+  nsString::const_char_iterator mFilePathCursor;
+  nsString::const_char_iterator mFilePathEnd;
+
+  nsDependentSubstring mItem;
+  char16_t const mSeparator;
+  nsTArray<nsDependentSubstring> mStack;
+};
+
+Normalizer::Normalizer(const nsAString& aFilePath, const char16_t aSeparator)
+  : mFilePathCursor(aFilePath.BeginReading())
+  , mFilePathEnd(aFilePath.EndReading())
+  , mSeparator(aSeparator)
+{
+}
+
+bool Normalizer::ConsumeItem()
+{
+  if (IsEOF()) {
+    return false;
+  }
+
+  nsString::const_char_iterator nameBegin = mFilePathCursor;
+  while (mFilePathCursor != mFilePathEnd) {
+    if (*mFilePathCursor == mSeparator) {
+      break; // don't include the separator
+    }
+    ++mFilePathCursor;
+  }
+
+  mItem.Rebind(nameBegin, mFilePathCursor);
+  return true;
+}
+
+bool Normalizer::ConsumeSeparator()
+{
+  if (IsEOF()) {
+    return false;
+  }
+
+  if (*mFilePathCursor != mSeparator) {
+    return false;
+  }
+
+  ++mFilePathCursor;
+  return true;
+}
+
+bool Normalizer::Get(nsAString& aNormalizedFilePath)
+{
+  aNormalizedFilePath.Truncate();
+
+  if (IsEOF()) {
+    return true;
+  }
+  if (ConsumeSeparator()) {
+    aNormalizedFilePath.Append(mSeparator);
+  }
+
+  if (IsEOF()) {
+    return true;
+  }
+  if (ConsumeSeparator()) {
+    aNormalizedFilePath.Append(mSeparator);
+  }
+
+  while (!IsEOF()) {
+    if (!ConsumeName()) {
+      return false;
+    }
+  }
+
+  for (auto const& name : mStack) {
+    aNormalizedFilePath.Append(name);
+  }
+
+  return true;
+}
+
+bool Normalizer::ConsumeName()
+{
+  if (!ConsumeItem()) {
+    return true;
+  }
+
+  if (CheckCurrentDir()) {
+    return true;
+  }
+
+  if (CheckParentDir()) {
+    if (!mStack.Length()) {
+      // This means there are more \.. than valid names
+      return false;
+    }
+
+    mStack.RemoveElementAt(mStack.Length() - 1);
+    return true;
+  }
+
+  if (mItem.IsEmpty()) {
+    // this means an empty name (a lone slash), which is illegal
+    return false;
+  }
+
+  if (ConsumeSeparator()) {
+    mItem.Rebind(mItem.BeginReading(), mFilePathCursor);
+  }
+  mStack.AppendElement(mItem);
+
+  return true;
+}
+
+bool Normalizer::CheckCurrentDir()
+{
+  if (mItem == NS_LITERAL_STRING(".")) {
+    ConsumeSeparator();
+    // EOF is acceptable
+    return true;
+  }
+
+  return false;
+}
+
+bool Normalizer::CheckParentDir()
+{
+  if (mItem == NS_LITERAL_STRING("..")) {
+    ConsumeSeparator();
+    // EOF is acceptable
+    return true;
+  }
+
+  return false;
+}
+
+} // anon
+
+bool IsBlockedUNCPath(const nsAString& aFilePath)
+{
+  if (!sBlockUNCPaths) {
+    return false;
+  }
+
+  if (!StringBeginsWith(aFilePath, NS_LITERAL_STRING("\\\\"))) {
+    return false;
+  }
+
+  nsAutoString normalized;
+  if (!Normalizer(aFilePath, L'\\').Get(normalized)) {
+    // Broken paths are considered invalid and thus inaccessible
+    return true;
+  }
+
+  for (const auto& allowedPrefix : PathArray()) {
+    if (StringBeginsWith(normalized, allowedPrefix)) {
+      if (normalized.Length() == allowedPrefix.Length()) {
+        return false;
+      }
+      if (normalized[allowedPrefix.Length()] == L'\\') {
+        return false;
+      }
+
+      // When we are here, the path has a form "\\path\prefixevil"
+      // while we have an allowed prefix of "\\path\prefix".
+      // Note that we don't want to add a slash to the end of a prefix
+      // so that opening the directory (no slash at the end) still works.
+      break;
+    }
+  }
+
+  return true;
+}
+
+void testing::SetBlockUNCPaths(bool aBlock)
+{
+  sBlockUNCPaths = aBlock;
+}
+
+void testing::AddDirectoryToWhitelist(nsAString const & aPath)
+{
+  PathArray().AppendElement(aPath);
+}
+
+bool testing::NormalizePath(nsAString const & aPath, nsAString & aNormalized)
+{
+  Normalizer normalizer(aPath, L'\\');
+  return normalizer.Get(aNormalized);
+}
+
+} // ::FilePreferences
+} // ::mozilla
diff --git a/xpcom/io/FilePreferences.h b/xpcom/io/FilePreferences.h
new file mode 100644
index 000000000..fa281f9e6
--- /dev/null
+++ b/xpcom/io/FilePreferences.h
@@ -0,0 +1,25 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "nsIObserver.h"
+
+namespace mozilla {
+namespace FilePreferences {
+
+void InitPrefs();
+void InitDirectoriesWhitelist();
+bool IsBlockedUNCPath(const nsAString& aFilePath);
+
+namespace testing {
+
+void SetBlockUNCPaths(bool aBlock);
+void AddDirectoryToWhitelist(nsAString const& aPath);
+bool NormalizePath(nsAString const & aPath, nsAString & aNormalized);
+
+}
+
+} // FilePreferences
+} // mozilla
diff --git a/xpcom/io/moz.build b/xpcom/io/moz.build
index 6f21e0a72..fdefa841b 100644
--- a/xpcom/io/moz.build
+++ b/xpcom/io/moz.build
@@ -84,6 +84,7 @@ EXPORTS += [
 
 EXPORTS.mozilla += [
     'Base64.h',
+    'FilePreferences.h',
     'SnappyCompressOutputStream.h',
     'SnappyFrameUtils.h',
     'SnappyUncompressInputStream.h',
@@ -119,6 +120,10 @@ UNIFIED_SOURCES += [
     'SpecialSystemDirectory.cpp',
 ]
 
+SOURCES += [
+    'FilePreferences.cpp',
+]
+
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'cocoa':
     SOURCES += [
         'CocoaFileUtils.mm',
diff --git a/xpcom/io/nsLocalFileWin.cpp b/xpcom/io/nsLocalFileWin.cpp
index 66e267807..5a72c750c 100644
--- a/xpcom/io/nsLocalFileWin.cpp
+++ b/xpcom/io/nsLocalFileWin.cpp
@@ -45,6 +45,7 @@
 #include "prproces.h"
 #include "prlink.h"
 
+#include "mozilla/FilePreferences.h"
 #include "mozilla/Mutex.h"
 #include "SpecialSystemDirectory.h"
 
@@ -1166,6 +1167,10 @@ nsLocalFile::InitWithPath(const nsAString& aFilePath)
     return NS_ERROR_FILE_UNRECOGNIZED_PATH;
   }
 
+  if (FilePreferences::IsBlockedUNCPath(aFilePath)) {
+    return NS_ERROR_FILE_ACCESS_DENIED;
+  }
+
   if (secondChar != L':' && (secondChar != L'\\' || firstChar != L'\\')) {
     return NS_ERROR_FILE_UNRECOGNIZED_PATH;
   }
@@ -1976,6 +1981,10 @@ nsLocalFile::CopySingleFile(nsIFile* aSourceFile, nsIFile* aDestParent,
     dwCopyFlags |= COPY_FILE_NO_BUFFERING;
   }
 
+  if (FilePreferences::IsBlockedUNCPath(destPath)) {
+    return NS_ERROR_FILE_ACCESS_DENIED;
+  }
+
   if (!move) {
     copyOK = ::CopyFileExW(filePath.get(), destPath.get(), nullptr,
                            nullptr, nullptr, dwCopyFlags);