sandbox/linux/services/credentials.h

   1 // Copyright (c) 2013 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_CREDENTIALS_H_
   6 #define SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
   7
   8 #include "build/build_config.h"
   9 // Link errors are tedious to track, raise a compile-time error instead.
  10 #if defined(OS_ANDROID)
  11 #error "Android is not supported."
  12 #endif  // defined(OS_ANDROID).
  13
  14 #include <string>
  15
  16 #include "base/basictypes.h"
  17 #include "base/memory/scoped_ptr.h"
  18 #include "sandbox/sandbox_export.h"
  19
  20 namespace sandbox {
  21
  22 // This class should be used to manipulate the current process' credentials.
  23 // It is currently a stub used to manipulate POSIX.1e capabilities as
  24 // implemented by the Linux kernel.
  25 class SANDBOX_EXPORT Credentials {
  26  public:
  27   Credentials();
  28   ~Credentials();
  29
  30   // Returns the number of file descriptors in the current process's FD
  31   // table, excluding |proc_fd|, which should be a file descriptor for
  32   // /proc.
  33   int CountOpenFds(int proc_fd);
  34
  35   // Checks whether the current process has any directory file descriptor open.
  36   // Directory file descriptors are "capabilities" that would let a process use
  37   // system calls such as openat() to bypass restrictions such as
  38   // DropFileSystemAccess().
  39   // Sometimes it's useful to call HasOpenDirectory() after file system access
  40   // has been dropped. In this case, |proc_fd| should be a file descriptor to
  41   // /proc. The file descriptor in |proc_fd| will be ignored by
  42   // HasOpenDirectory() and remains owned by the caller. It is very important
  43   // for the caller to close it.
  44   // If /proc is available, |proc_fd| can be passed as -1.
  45   // If |proc_fd| is -1 and /proc is not available, this function will return
  46   // false.
  47   bool HasOpenDirectory(int proc_fd);
  48
  49   // Drop all capabilities in the effective, inheritable and permitted sets for
  50   // the current process.
  51   bool DropAllCapabilities();
  52   // Return true iff there is any capability in any of the capabilities sets
  53   // of the current process.
  54   bool HasAnyCapability() const;
  55   // Returns the capabilities of the current process in textual form, as
  56   // documented in libcap2's cap_to_text(3). This is mostly useful for
  57   // debugging and tests.
  58   scoped_ptr<std::string> GetCurrentCapString() const;
  59
  60   // Returns whether the kernel supports CLONE_NEWUSER and whether it would be
  61   // possible to immediately move to a new user namespace. There is no point
  62   // in using this method right before calling MoveToNewUserNS(), simply call
  63   // MoveToNewUserNS() immediately. This method is only useful to test kernel
  64   // support ahead of time.
  65   static bool SupportsNewUserNS();
  66
  67   // Move the current process to a new "user namespace" as supported by Linux
  68   // 3.8+ (CLONE_NEWUSER).
  69   // The uid map will be set-up so that the perceived uid and gid will not
  70   // change.
  71   // If this call succeeds, the current process will be granted a full set of
  72   // capabilities in the new namespace.
  73   bool MoveToNewUserNS();
  74
  75   // Remove the ability of the process to access the file system. File
  76   // descriptors which are already open prior to calling this API remain
  77   // available.
  78   // The implementation currently uses chroot(2) and requires CAP_SYS_CHROOT.
  79   // CAP_SYS_CHROOT can be acquired by using the MoveToNewUserNS() API.
  80   // Make sure to call DropAllCapabilities() after this call to prevent
  81   // escapes.
  82   // To be secure, it's very important for this API to not be called while the
  83   // process has any directory file descriptor open.
  84   bool DropFileSystemAccess();
  85
  86  private:
  87   DISALLOW_COPY_AND_ASSIGN(Credentials);
  88 };
  89
  90 }  // namespace sandbox.
  91
  92 #endif  // SANDBOX_LINUX_SERVICES_CREDENTIALS_H_