sandbox/linux/services/proc_util.h

   1 // Copyright 2014 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_PROC_UTIL_H_
   6 #define SANDBOX_LINUX_SERVICES_PROC_UTIL_H_
   7
   8 #include "base/files/scoped_file.h"
   9 #include "base/macros.h"
  10 #include "sandbox/sandbox_export.h"
  11
  12 namespace sandbox {
  13
  14 class SANDBOX_EXPORT ProcUtil {
  15  public:
  16   // Returns the number of file descriptors in the current process's FD
  17   // table, excluding |proc_fd|, which should be a file descriptor for
  18   // /proc.
  19   static int CountOpenFds(int proc_fd);
  20
  21   // Checks whether the current process has any directory file descriptor open.
  22   // Directory file descriptors are "capabilities" that would let a process use
  23   // system calls such as openat() to bypass restrictions such as
  24   // DropFileSystemAccess().
  25   // Sometimes it's useful to call HasOpenDirectory() after file system access
  26   // has been dropped. In this case, |proc_fd| should be a file descriptor to
  27   // /proc. The file descriptor in |proc_fd| will be ignored by
  28   // HasOpenDirectory() and remains owned by the caller. It is very important
  29   // for the caller to close it.
  30   // If /proc is available, |proc_fd| can be passed as -1.
  31   // If |proc_fd| is -1 and /proc is not available, this function will return
  32   // false.
  33   static bool HasOpenDirectory(int proc_fd);
  34
  35   // Open /proc/self/task/ or crash if it cannot.
  36   static base::ScopedFD OpenProcSelfTask();
  37
  38  private:
  39   DISALLOW_IMPLICIT_CONSTRUCTORS(ProcUtil);
  40 };
  41
  42 }  // namespace sandbox
  43
  44 #endif  // SANDBOX_LINUX_SERVICES_PROC_UTIL_H_