1 files changed, 373 insertions, 0 deletions
diff --git a/xpcom/io/FilePreferences.cpp b/xpcom/io/FilePreferences.cpp
new file mode 100644
index 0000000000..1d96c72810
--- /dev/null
+++ b/xpcom/io/FilePreferences.cpp
@@ -0,0 +1,373 @@
+/* -*- 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/Atomics.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TextUtils.h"
+#include "mozilla/Tokenizer.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsString.h"
+
+namespace mozilla {
+namespace FilePreferences {
+
+static StaticMutex sMutex;
+
+static bool sBlockUNCPaths = false;
+typedef nsTArray<nsString> WinPaths;
+
+static WinPaths& PathAllowlist() MOZ_REQUIRES(sMutex) {
+  sMutex.AssertCurrentThreadOwns();
+
+  static WinPaths sPaths MOZ_GUARDED_BY(sMutex);
+  return sPaths;
+}
+
+#ifdef XP_WIN
+const auto kDevicePathSpecifier = u"\\\\?\\"_ns;
+
+typedef char16_t char_path_t;
+#else
+typedef char char_path_t;
+#endif
+
+// Initially false to make concurrent consumers acquire the lock and sync.
+// The plain bool is synchronized with sMutex, the atomic one is for a quick
+// check w/o the need to acquire the lock on the hot path.
+static bool sForbiddenPathsEmpty = false;
+static Atomic<bool, Relaxed> sForbiddenPathsEmptyQuickCheck{false};
+
+typedef nsTArray<nsTString<char_path_t>> Paths;
+static StaticAutoPtr<Paths> sForbiddenPaths;
+
+static Paths& ForbiddenPaths() {
+  sMutex.AssertCurrentThreadOwns();
+  if (!sForbiddenPaths) {
+    sForbiddenPaths = new nsTArray<nsTString<char_path_t>>();
+    ClearOnShutdown(&sForbiddenPaths);
+  }
+  return *sForbiddenPaths;
+}
+
+static void AllowUNCDirectory(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 allowlist 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, u"\\\\"_ns)) {
+    return;
+  }
+
+  StaticMutexAutoLock lock(sMutex);
+
+  if (!PathAllowlist().Contains(path)) {
+    PathAllowlist().AppendElement(path);
+  }
+}
+
+void InitPrefs() {
+  sBlockUNCPaths =
+      Preferences::GetBool("network.file.disable_unc_paths", false);
+
+  nsTAutoString<char_path_t> forbidden;
+#ifdef XP_WIN
+  Preferences::GetString("network.file.path_blacklist", forbidden);
+#else
+  Preferences::GetCString("network.file.path_blacklist", forbidden);
+#endif
+
+  StaticMutexAutoLock lock(sMutex);
+
+  if (forbidden.IsEmpty()) {
+    sForbiddenPathsEmptyQuickCheck = (sForbiddenPathsEmpty = true);
+    return;
+  }
+
+  ForbiddenPaths().Clear();
+  TTokenizer<char_path_t> p(forbidden);
+  while (!p.CheckEOF()) {
+    nsTString<char_path_t> path;
+    Unused << p.ReadUntil(TTokenizer<char_path_t>::Token::Char(','), path);
+    path.Trim(" ");
+    if (!path.IsEmpty()) {
+      ForbiddenPaths().AppendElement(path);
+    }
+    Unused << p.CheckChar(',');
+  }
+
+  sForbiddenPathsEmptyQuickCheck =
+      (sForbiddenPathsEmpty = ForbiddenPaths().Length() == 0);
+}
+
+void InitDirectoriesAllowlist() {
+  // NS_GRE_DIR is the installation path where the binary resides.
+  AllowUNCDirectory(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.
+  AllowUNCDirectory(NS_APP_USER_PROFILE_50_DIR);
+  AllowUNCDirectory(NS_APP_USER_PROFILE_LOCAL_50_DIR);
+}
+
+namespace {  // anon
+
+template <typename TChar>
+class TNormalizer : public TTokenizer<TChar> {
+  typedef TTokenizer<TChar> base;
+
+ public:
+  typedef typename base::Token Token;
+
+  TNormalizer(const nsTSubstring<TChar>& aFilePath, const Token& aSeparator)
+      : TTokenizer<TChar>(aFilePath), mSeparator(aSeparator) {}
+
+  bool Get(nsTSubstring<TChar>& aNormalizedFilePath) {
+    aNormalizedFilePath.Truncate();
+
+    // Windows UNC paths begin with double separator (\\)
+    // Linux paths begin with just one separator (/)
+    // If we want to use the normalizer for regular windows paths this code
+    // will need to be updated.
+#ifdef XP_WIN
+    if (base::Check(mSeparator)) {
+      aNormalizedFilePath.Append(mSeparator.AsChar());
+    }
+#endif
+
+    if (base::Check(mSeparator)) {
+      aNormalizedFilePath.Append(mSeparator.AsChar());
+    }
+
+    while (base::HasInput()) {
+      if (!ConsumeName()) {
+        return false;
+      }
+    }
+
+    for (auto const& name : mStack) {
+      aNormalizedFilePath.Append(name);
+    }
+
+    return true;
+  }
+
+ private:
+  bool ConsumeName() {
+    if (base::CheckEOF()) {
+      return true;
+    }
+
+    if (CheckCurrentDir()) {
+      return true;
+    }
+
+    if (CheckParentDir()) {
+      if (!mStack.Length()) {
+        // This means there are more \.. than valid names
+        return false;
+      }
+
+      mStack.RemoveLastElement();
+      return true;
+    }
+
+    nsTDependentSubstring<TChar> name;
+    if (base::ReadUntil(mSeparator, name, base::INCLUDE_LAST) &&
+        name.Length() == 1) {
+      // this means an empty name (a lone slash), which is illegal
+      return false;
+    }
+    mStack.AppendElement(name);
+
+    return true;
+  }
+
+  bool CheckParentDir() {
+    typename nsTString<TChar>::const_char_iterator cursor = base::mCursor;
+    if (base::CheckChar('.') && base::CheckChar('.') && CheckSeparator()) {
+      return true;
+    }
+
+    base::mCursor = cursor;
+    return false;
+  }
+
+  bool CheckCurrentDir() {
+    typename nsTString<TChar>::const_char_iterator cursor = base::mCursor;
+    if (base::CheckChar('.') && CheckSeparator()) {
+      return true;
+    }
+
+    base::mCursor = cursor;
+    return false;
+  }
+
+  bool CheckSeparator() { return base::Check(mSeparator) || base::CheckEOF(); }
+
+  Token const mSeparator;
+  nsTArray<nsTDependentSubstring<TChar>> mStack;
+};
+
+#ifdef XP_WIN
+bool IsDOSDevicePathWithDrive(const nsAString& aFilePath) {
+  if (!StringBeginsWith(aFilePath, kDevicePathSpecifier)) {
+    return false;
+  }
+
+  const auto pathNoPrefix =
+      nsDependentSubstring(aFilePath, kDevicePathSpecifier.Length());
+
+  // After the device path specifier, the rest of file path can be:
+  // - starts with the volume or drive. e.g. \\?\C:\...
+  // - UNCs. e.g. \\?\UNC\Server\Share\Test\Foo.txt
+  // - device UNCs. e.g. \\?\server1\e:\utilities\\filecomparer\...
+  // The first case should not be blocked by IsBlockedUNCPath.
+  if (!StartsWithDiskDesignatorAndBackslash(pathNoPrefix)) {
+    return false;
+  }
+
+  return true;
+}
+#endif
+
+}  // namespace
+
+bool IsBlockedUNCPath(const nsAString& aFilePath) {
+  typedef TNormalizer<char16_t> Normalizer;
+  if (!sBlockUNCPaths) {
+    return false;
+  }
+
+  if (!StringBeginsWith(aFilePath, u"\\\\"_ns)) {
+    return false;
+  }
+
+#ifdef XP_WIN
+  // ToDo: We don't need to check this once we can check if there is a valid
+  // server or host name that is prefaced by "\\".
+  // https://docs.microsoft.com/en-us/dotnet/standard/io/file-path-formats
+  if (IsDOSDevicePathWithDrive(aFilePath)) {
+    return false;
+  }
+#endif
+
+  nsAutoString normalized;
+  if (!Normalizer(aFilePath, Normalizer::Token::Char('\\')).Get(normalized)) {
+    // Broken paths are considered invalid and thus inaccessible
+    return true;
+  }
+
+  StaticMutexAutoLock lock(sMutex);
+
+  for (const auto& allowedPrefix : PathAllowlist()) {
+    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;
+}
+
+#ifdef XP_WIN
+const char kPathSeparator = '\\';
+#else
+const char kPathSeparator = '/';
+#endif
+
+bool IsAllowedPath(const nsTSubstring<char_path_t>& aFilePath) {
+  typedef TNormalizer<char_path_t> Normalizer;
+
+  // An atomic quick check out of the lock, because this is mostly `true`.
+  if (sForbiddenPathsEmptyQuickCheck) {
+    return true;
+  }
+
+  StaticMutexAutoLock lock(sMutex);
+
+  if (sForbiddenPathsEmpty) {
+    return true;
+  }
+
+  // If sForbidden has been cleared at shutdown, we must avoid calling
+  // ForbiddenPaths() again, as that will recreate the array and we will leak.
+  if (!sForbiddenPaths) {
+    return true;
+  }
+
+  nsTAutoString<char_path_t> normalized;
+  if (!Normalizer(aFilePath, Normalizer::Token::Char(kPathSeparator))
+           .Get(normalized)) {
+    // Broken paths are considered invalid and thus inaccessible
+    return false;
+  }
+
+  for (const auto& prefix : ForbiddenPaths()) {
+    if (StringBeginsWith(normalized, prefix)) {
+      if (normalized.Length() > prefix.Length() &&
+          normalized[prefix.Length()] != kPathSeparator) {
+        continue;
+      }
+      return false;
+    }
+  }
+
+  return true;
+}
+
+#ifdef XP_WIN
+bool StartsWithDiskDesignatorAndBackslash(const nsAString& aAbsolutePath) {
+  // aAbsolutePath can only be (in regular expression):
+  // UNC path: ^\\\\.*
+  // A single backslash: ^\\.*
+  // A disk designator with a backslash: ^[A-Za-z]:\\.*
+  return aAbsolutePath.Length() >= 3 && IsAsciiAlpha(aAbsolutePath.CharAt(0)) &&
+         aAbsolutePath.CharAt(1) == L':' &&
+         aAbsolutePath.CharAt(2) == kPathSeparator;
+}
+#endif
+
+void testing::SetBlockUNCPaths(bool aBlock) { sBlockUNCPaths = aBlock; }
+
+void testing::AddDirectoryToAllowlist(nsAString const& aPath) {
+  StaticMutexAutoLock lock(sMutex);
+  PathAllowlist().AppendElement(aPath);
+}
+
+bool testing::NormalizePath(nsAString const& aPath, nsAString& aNormalized) {
+  typedef TNormalizer<char16_t> Normalizer;
+  Normalizer normalizer(aPath, Normalizer::Token::Char('\\'));
+  return normalizer.Get(aNormalized);
+}
+
+}  // namespace FilePreferences
+}  // namespace mozilla