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   static_assert((base::is_same<uid_t, gid_t>::value),
21                 "uid_t and gid_t must be the same type");
22   // generic_id_t can be used for either uid_t or gid_t.
23   typedef uid_t generic_id_t;
24 
25   // Write a uid or gid mapping from |id| to |id| in |map_file|. This function
26   // is async-signal-safe.
27   static bool WriteToIdMapFile(const char* map_file,
28                                generic_id_t id) WARN_UNUSED_RESULT;
29 
30   // Returns true if unprivileged namespaces of type |type| is supported
31   // (meaning that both CLONE_NEWUSER and type are are supported).  |type| must
32   // be one of CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWNS, CLONE_NEWPID,
33   // CLONE_NEWUSER, or CLONE_NEWUTS. This relies on access to /proc, so it will
34   // not work from within a sandbox.
35   static bool KernelSupportsUnprivilegedNamespace(int type);
36 
37   // Returns true if the kernel supports denying setgroups in a user namespace.
38   // On kernels where this is supported, DenySetgroups must be called before a
39   // gid mapping can be added.
40   static bool KernelSupportsDenySetgroups();
41 
42   // Disables setgroups() within the current user namespace. On Linux 3.18.2 and
43   // later, this is required in order to write to /proc/self/gid_map without
44   // having CAP_SETGID. Callers can determine whether is this needed with
45   // KernelSupportsDenySetgroups. This function is async-signal-safe.
46   static bool DenySetgroups() WARN_UNUSED_RESULT;
47 
48  private:
49   DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceUtils);
50 };
51 
52 }  // namespace sandbox
53 
54 #endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_UTILS_H_
55