sandbox/mac/bootstrap_sandbox.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_MAC_BOOTSTRAP_SANDBOX_H_
   6 #define SANDBOX_MAC_BOOTSTRAP_SANDBOX_H_
   7
   8 #include <mach/mach.h>
   9
  10 #include <map>
  11 #include <string>
  12
  13 #include "base/mac/scoped_mach_port.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "base/process/process_handle.h"
  16 #include "base/synchronization/lock.h"
  17 #include "sandbox/mac/policy.h"
  18 #include "sandbox/sandbox_export.h"
  19
  20 namespace sandbox {
  21
  22 class LaunchdInterceptionServer;
  23
  24 // The BootstrapSandbox is a second-layer sandbox for Mac. It is used to limit
  25 // the bootstrap namespace attack surface of child processes. The parent
  26 // process creates an instance of this class and registers policies that it
  27 // can enforce on its children.
  28 //
  29 // With this sandbox, the parent process must replace the bootstrap port prior
  30 // to the sandboxed target's execution. This should be done by setting the
  31 // base::LaunchOptions.replacement_bootstrap_name to the
  32 // server_bootstrap_name() of this class. Requests from the child that would
  33 // normally go to launchd are filtered based on the specified per-process
  34 // policies. If a request is permitted by the policy, it is forwarded on to
  35 // launchd for servicing. If it is not, then the sandbox will reply with a
  36 // primitive that does not grant additional capabilities to the receiver.
  37 //
  38 // Clients that which to use the sandbox must inform it of the creation and
  39 // death of child processes for which the sandbox should be enforced. The
  40 // client of the sandbox is intended to be an unsandboxed parent process that
  41 // fork()s sandboxed (and other unsandboxed) child processes.
  42 //
  43 // When the parent is ready to fork a new child process with this sandbox
  44 // being enforced, it should use the pair of methods PrepareToForkWithPolicy()
  45 // and FinishedFork(), and call fork() between them. The first method will
  46 // set the policy for the new process, and the second will finialize the
  47 // association between the process ID and sandbox policy ID.
  48 //
  49 // All methods of this class may be called from any thread, but
  50 // PrepareToForkWithPolicy() and FinishedFork() must be non-nested and balanced.
  51 class SANDBOX_EXPORT BootstrapSandbox {
  52  public:
  53   // Creates a new sandbox manager. Returns NULL on failure.
  54   static scoped_ptr<BootstrapSandbox> Create();
  55
  56   ~BootstrapSandbox();
  57
  58   // Registers a bootstrap policy associated it with an identifier. The
  59   // |sandbox_policy_id| must be greater than 0.
  60   void RegisterSandboxPolicy(int sandbox_policy_id,
  61                              const BootstrapSandboxPolicy& policy);
  62
  63   // Called in the parent prior to fork()ing a child. The policy registered
  64   // to |sandbox_policy_id| will be enforced on the new child. This must be
  65   // followed by a call to FinishedFork().
  66   void PrepareToForkWithPolicy(int sandbox_policy_id);
  67
  68   // Called in the parent after fork()ing a child. It records the |handle|
  69   // and associates it with the specified-above |sandbox_policy_id|.
  70   // If fork() failed and a new child was not created, pass kNullProcessHandle.
  71   void FinishedFork(base::ProcessHandle handle);
  72
  73   // Called in the parent when a process has died. It cleans up the references
  74   // to the process.
  75   void ChildDied(base::ProcessHandle handle);
  76
  77   // Looks up the policy for a given process ID. If no policy is associated
  78   // with the |pid|, this returns NULL.
  79   const BootstrapSandboxPolicy* PolicyForProcess(pid_t pid) const;
  80
  81   std::string server_bootstrap_name() const { return server_bootstrap_name_; }
  82   mach_port_t real_bootstrap_port() const { return real_bootstrap_port_; }
  83
  84  private:
  85   BootstrapSandbox();
  86
  87   // The name in the system bootstrap server by which the |server_|'s port
  88   // is known.
  89   const std::string server_bootstrap_name_;
  90
  91   // The original bootstrap port of the process, which is connected to the
  92   // real launchd server.
  93   base::mac::ScopedMachSendRight real_bootstrap_port_;
  94
  95   // The |lock_| protects all the following variables.
  96   mutable base::Lock lock_;
  97
  98   // The sandbox_policy_id that will be enforced for the new child.
  99   int effective_policy_id_;
 100
 101   // All the policies that have been registered with this sandbox manager.
 102   std::map<int, const BootstrapSandboxPolicy> policies_;
 103
 104   // The association between process ID and sandbox policy ID.
 105   std::map<base::ProcessHandle, int> sandboxed_processes_;
 106
 107   // A Mach IPC message server that is used to intercept and filter bootstrap
 108   // requests.
 109   scoped_ptr<LaunchdInterceptionServer> server_;
 110 };
 111
 112 }  // namespace sandbox
 113
 114 #endif  // SANDBOX_MAC_BOOTSTRAP_SANDBOX_H_