1// Copyright (c) 2012 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_BROKER_PROCESS_H_
6#define SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
7
8#include <string>
9#include <vector>
10
11#include "base/basictypes.h"
12#include "base/callback_forward.h"
13#include "base/pickle.h"
14#include "base/process/process.h"
15#include "sandbox/sandbox_export.h"
16
17namespace sandbox {
18
19// Create a new "broker" process to which we can send requests via an IPC
20// channel.
21// This is a low level IPC mechanism that is suitable to be called from a
22// signal handler.
23// A process would typically create a broker process before entering
24// sandboxing.
25// 1. BrokerProcess open_broker(read_whitelist, write_whitelist);
26// 2. CHECK(open_broker.Init(NULL));
27// 3. Enable sandbox.
28// 4. Use open_broker.Open() to open files.
29class SANDBOX_EXPORT BrokerProcess {
30 public:
31  // |denied_errno| is the error code returned when methods such as Open()
32  // or Access() are invoked on a file which is not in the whitelist. EACCESS
33  // would be a typical value.
34  // |allowed_r_files| and |allowed_w_files| are white lists of files that can
35  // be opened later via the Open() API, respectively for reading and writing.
36  // A file available read-write should be listed in both.
37  // |fast_check_in_client| and |quiet_failures_for_tests| are reserved for
38  // unit tests, don't use it.
39  explicit BrokerProcess(int denied_errno,
40                         const std::vector<std::string>& allowed_r_files,
41                         const std::vector<std::string>& allowed_w_files,
42                         bool fast_check_in_client = true,
43                         bool quiet_failures_for_tests = false);
44  ~BrokerProcess();
45  // Will initialize the broker process. There should be no threads at this
46  // point, since we need to fork().
47  // broker_process_init_callback will be called in the new broker process,
48  // after fork() returns.
49  bool Init(const base::Callback<bool(void)>& broker_process_init_callback);
50
51  // Can be used in place of access(). Will be async signal safe.
52  // X_OK will always return an error in practice since the broker process
53  // doesn't support execute permissions.
54  // It's similar to the access() system call and will return -errno on errors.
55  int Access(const char* pathname, int mode) const;
56  // Can be used in place of open(). Will be async signal safe.
57  // The implementation only supports certain white listed flags and will
58  // return -EPERM on other flags.
59  // It's similar to the open() system call and will return -errno on errors.
60  int Open(const char* pathname, int flags) const;
61
62  int broker_pid() const { return broker_pid_; }
63
64 private:
65  enum IPCCommands {
66    kCommandInvalid = 0,
67    kCommandOpen,
68    kCommandAccess,
69  };
70  int PathAndFlagsSyscall(enum IPCCommands command_type,
71                          const char* pathname,
72                          int flags) const;
73  bool HandleRequest() const;
74  bool HandleRemoteCommand(IPCCommands command_type,
75                           int reply_ipc,
76                           const Pickle& read_pickle,
77                           PickleIterator iter) const;
78
79  void AccessFileForIPC(const std::string& requested_filename,
80                        int mode,
81                        Pickle* write_pickle) const;
82  void OpenFileForIPC(const std::string& requested_filename,
83                      int flags,
84                      Pickle* write_pickle,
85                      std::vector<int>* opened_files) const;
86  bool GetFileNameIfAllowedToAccess(const char*, int, const char**) const;
87  bool GetFileNameIfAllowedToOpen(const char*, int, const char**) const;
88  const int denied_errno_;
89  bool initialized_;               // Whether we've been through Init() yet.
90  bool is_child_;                  // Whether we're the child (broker process).
91  bool fast_check_in_client_;      // Whether to forward a request that we know
92                                   // will be denied to the broker.
93  bool quiet_failures_for_tests_;  // Disable certain error message when
94                                   // testing for failures.
95  pid_t broker_pid_;               // The PID of the broker (child).
96  const std::vector<std::string> allowed_r_files_;  // Files allowed for read.
97  const std::vector<std::string> allowed_w_files_;  // Files allowed for write.
98  int ipc_socketpair_;  // Our communication channel to parent or child.
99  DISALLOW_IMPLICIT_CONSTRUCTORS(BrokerProcess);
100
101  friend class BrokerProcessTestHelper;
102};
103
104}  // namespace sandbox
105
106#endif  // SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
107