sandbox/linux/services/namespace_utils.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
   6 #define SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
   7
   8 #include <sys/types.h>
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/macros.h"
  12 #include "base/template_util.h"
  13 #include "sandbox/sandbox_export.h"
  14
  15 namespace sandbox {
  16
  17 // Utility functions for using Linux namepaces.
  18 class SANDBOX_EXPORT NamespaceUtils {
  19  public:
  20   COMPILE_ASSERT((base::is_same<uid_t, gid_t>::value), UidAndGidAreSameType);
  21   // generic_id_t can be used for either uid_t or gid_t.
  22   typedef uid_t generic_id_t;
  23
  24   // Write a uid or gid mapping from |id| to |id| in |map_file|. This function
  25   // is async-signal-safe.
  26   static bool WriteToIdMapFile(const char* map_file,
  27                                generic_id_t id) WARN_UNUSED_RESULT;
  28
  29   // Returns true if unprivileged namespaces of type |type| is supported
  30   // (meaning that both CLONE_NEWUSER and type are are supported).  |type| must
  31   // be one of CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWNS, CLONE_NEWPID,
  32   // CLONE_NEWUSER, or CLONE_NEWUTS. This relies on access to /proc, so it will
  33   // not work from within a sandbox.
  34   static bool KernelSupportsUnprivilegedNamespace(int type);
  35
  36   // Returns true if the kernel supports denying setgroups in a user namespace.
  37   // On kernels where this is supported, DenySetgroups must be called before a
  38   // gid mapping can be added.
  39   static bool KernelSupportsDenySetgroups();
  40
  41   // Disables setgroups() within the current user namespace. On Linux 3.18.2 and
  42   // later, this is required in order to write to /proc/self/gid_map without
  43   // having CAP_SETGID. Callers can determine whether is this needed with
  44   // KernelSupportsDenySetgroups. This function is async-signal-safe.
  45   static bool DenySetgroups() WARN_UNUSED_RESULT;
  46
  47  private:
  48   DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceUtils);
  49 };
  50
  51 }  // namespace sandbox
  52
  53 #endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_