sandbox/linux/services/namespace_sandbox.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_SANDBOX_H_
   6 #define SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
   7
   8 #include <sys/types.h>
   9
  10 #include <string>
  11 #include <vector>
  12
  13 #include "base/command_line.h"
  14 #include "base/macros.h"
  15 #include "base/process/launch.h"
  16 #include "base/process/process.h"
  17 #include "sandbox/sandbox_export.h"
  18
  19 namespace sandbox {
  20
  21 // Helper class for starting a process inside a new user, PID, and network
  22 // namespace. Before using a namespace sandbox, check for namespaces support
  23 // using Credentials::CanCreateProcessInNewUserNS.
  24 //
  25 // A typical use for "A" launching a sandboxed process "B" would be:
  26 // 1. A sets up a command line and launch options for process B.
  27 // 2. A launches B with LaunchProcess.
  28 // 3. B should be prepared to assume the role of init(1). In particular, apart
  29 //    from SIGKILL and SIGSTOP, B cannot receive any signal for which it does
  30 //    not have an explicit signal handler registered.
  31 //    If B dies, all the processes in the namespace will die.
  32 //    B can fork() and the parent can assume the role of init(1), by using
  33 //    CreateInitProcessReaper().
  34 // 4. B chroots using Credentials::MoveToNewUserNS() and
  35 //    Credentials::DropFileSystemAccess()
  36 // 5. B drops capabilities gained by entering the new user namespace with
  37 //    Credentials::DropAllCapabilities().
  38 class SANDBOX_EXPORT NamespaceSandbox {
  39  public:
  40 #if !defined(OS_NACL_NONSFI)
  41   // Launch a new process inside its own user/PID/network namespaces (depending
  42   // on kernel support). Requires at a minimum that user namespaces are
  43   // supported (use Credentials::CanCreateProcessInNewUserNS to check this).
  44   //
  45   // pre_exec_delegate and clone_flags fields of LaunchOptions should be nullptr
  46   // and 0, respectively, since this function makes a copy of options and
  47   // overrides them.
  48   static base::Process LaunchProcess(const base::CommandLine& cmdline,
  49                                      const base::LaunchOptions& options);
  50   static base::Process LaunchProcess(const std::vector<std::string>& argv,
  51                                      const base::LaunchOptions& options);
  52 #endif  // !defined(OS_NACL_NONSFI)
  53
  54   // Forks a process in its own PID namespace. The child process is the init
  55   // process inside of the PID namespace, so if the child needs to fork further,
  56   // it should call CreateInitProcessReaper, which turns the init process into a
  57   // reaper process.
  58   //
  59   // Otherwise, the child should setup handlers for signals which should
  60   // terminate the process using InstallDefaultTerminationSignalHandlers or
  61   // InstallTerminationSignalHandler. This works around the fact that init
  62   // processes ignore such signals unless they have an explicit handler set.
  63   //
  64   // This function requries CAP_SYS_ADMIN. If |drop_capabilities_in_child| is
  65   // true, then capabilities are dropped in the child.
  66   static pid_t ForkInNewPidNamespace(bool drop_capabilities_in_child);
  67
  68   // Installs a signal handler for:
  69   //
  70   // SIGHUP, SIGINT, SIGABRT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
  71   //
  72   // that exits with SignalExitCode(sig). These are signals whose default action
  73   // is to terminate the program (apart from SIGILL, SIGFPE, and SIGSEGV, which
  74   // will still terminate the process if e.g. an illegal instruction is
  75   // encountered, etc.).
  76   //
  77   // If any of these already had a signal handler installed, this function will
  78   // not override them.
  79   static void InstallDefaultTerminationSignalHandlers();
  80
  81   // Installs a signal handler for |sig| which exits with |exit_code|. If a
  82   // signal handler was already present for |sig|, does nothing and returns
  83   // false.
  84   static bool InstallTerminationSignalHandler(int sig, int exit_code);
  85
  86   // Returns an exit code corresponding to the process being killed by sig. This
  87   // is the same as exit code that NaCl's default signal handler uses.
  88   static int SignalExitCode(int sig) { return -sig & 0xff; }
  89
  90   // Returns whether the namespace sandbox created a new user, PID, and network
  91   // namespace. In particular, InNewUserNamespace should return true iff the
  92   // process was started via this class.
  93   static bool InNewUserNamespace();
  94   static bool InNewPidNamespace();
  95   static bool InNewNetNamespace();
  96
  97  private:
  98   DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceSandbox);
  99 };
 100
 101 }  // namespace sandbox
 102
 103 #endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_