NaCl Linux: create NaClSandbox class

components/nacl/loader/sandbox_linux/nacl_sandbox_linux.h

+// Copyright 2014 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.
+
+#ifndef COMPONENTS_NACL_LOADER_SANDBOX_LINUX_NACL_SANDBOX_LINUX_H_
+#define COMPONENTS_NACL_LOADER_SANDBOX_LINUX_NACL_SANDBOX_LINUX_H_
+
+#include "base/files/scoped_file.h"
+#include "base/macros.h"
+
+namespace nacl {
+
+// NaClSandbox supports two independent layers of sandboxing.
+// layer-1 uses a chroot. It requires both InitializeLayerOneSandbox() and
+// SealLayerOneSandbox() to have been called to be enforcing.
+// layer-2 uses seccomp-bpf. It requires the layer-1 sandbox to not yet be
+// sealed when being engaged.
+// For the layer-1 sandbox to work, the current process must be a child of
+// the setuid sandbox. InitializeLayerOneSandbox() can only be called once
+// per instance of the setuid sandbox.
+//
+// A typical use case of this class would be:
+// 1. Load libraries and do some pre-initialization
+// 2. InitializeLayerOneSandbox();
+// 3. Do some more initializations (it is ok to fork() here).
+// 4. CHECK(!HasOpenDirectory));
+//    (This check is not strictly necessary, as the only possibility for a
+//    new directory descriptor to exist after (2) has been called is via IPC)).
+// 5. InitializeLayerTwoSandbox();
+// 6. SealLayerOneSandbox();
+// 7. CheckSandboxingStateWithPolicy();
+class NaClSandbox {
+ public:
+  NaClSandbox();
+  ~NaClSandbox();
+
+  // This API will only work if the layer-1 sandbox is not sealed and the
+  // layer-2 sandbox is not engaged.
+  bool IsSingleThreaded();
+  // Check whether the current process owns any directory file descriptors. This
+  // will ignore any directory file descriptor owned by this object (i.e. those
+  // that will be closed after SealLayerOneSandbox()) is called.
+  // This API will only work if the layer-1 sandbox is not sealed and the
+  // layer-2 sandbox is not engaged.
+  bool HasOpenDirectory();
+  // Will attempt to initialize the layer-1 sandbox, depending on flags and the
+  // environment. It can only succeed if the current process is a child of the
+  // setuid sandbox.
+  void InitializeLayerOneSandbox();
+  // Will attempt to initialize the layer-2 sandbox, depending on flags and the
+  // environment. |uses_nonsfi_mode| describes which seccomp-bpf policy is
+  // appropriate.
+  void InitializeLayerTwoSandbox(bool uses_nonsfi_mode);
+  // Seal the layer-1 sandbox, making it enforcing.
+  void SealLayerOneSandbox();
+  // Check that the current sandboxing state matches the level of sandboxing
+  // expected for NaCl in the current configuration. Crash if it does not.
+  void CheckSandboxingStateWithPolicy();
+
+  bool layer_one_enabled() { return layer_one_enabled_; }
+  bool layer_two_enabled() { return layer_two_enabled_; }
+
+ private:
+  bool layer_one_enabled_;
+  bool layer_one_sealed_;
+  bool layer_two_enabled_;
+  bool layer_two_is_nonsfi_;
+  // |proc_fd_| must be released before the layer-1 sandbox is considered
+  // enforcing.
+  base::ScopedFD proc_fd_;
+  DISALLOW_COPY_AND_ASSIGN(NaClSandbox);
+};
+
+}  // namespace nacl
+
+#endif  // COMPONENTS_NACL_LOADER_SANDBOX_LINUX_NACL_SANDBOX_LINUX_H_