1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
|
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SANDBOX_LINUX_SYSCALL_BROKER_BROKER_COMMAND_H_
#define SANDBOX_LINUX_SYSCALL_BROKER_BROKER_COMMAND_H_
#include <fcntl.h>
#include <stddef.h>
#include <stdint.h>
#include <bitset>
#include <initializer_list>
#include <utility>
namespace sandbox {
namespace syscall_broker {
class BrokerPermissionList;
// Some flags are local to the current process and cannot be sent over a Unix
// socket. They need special treatment from the client.
// O_CLOEXEC is tricky because in theory another thread could call execve()
// before special treatment is made on the client, so a client needs to call
// recvmsg(2) with MSG_CMSG_CLOEXEC.
// To make things worse, there are two CLOEXEC related flags, FD_CLOEXEC (see
// F_GETFD in fcntl(2)) and O_CLOEXEC (see F_GETFL in fcntl(2)). O_CLOEXEC
// doesn't affect the semantics on execve(), it's merely a note that the
// descriptor was originally opened with O_CLOEXEC as a flag. And it is sent
// over unix sockets just fine, so a receiver that would (incorrectly) look at
// O_CLOEXEC instead of FD_CLOEXEC may be tricked in thinking that the file
// descriptor will or won't be closed on execve().
constexpr int kCurrentProcessOpenFlagsMask = O_CLOEXEC;
enum BrokerCommand {
COMMAND_INVALID = 0,
COMMAND_ACCESS,
COMMAND_MKDIR,
COMMAND_OPEN,
COMMAND_READLINK,
COMMAND_RENAME,
COMMAND_RMDIR,
COMMAND_STAT,
COMMAND_STAT64,
COMMAND_UNLINK,
COMMAND_INOTIFY_ADD_WATCH,
// NOTE: update when adding new commands.
COMMAND_MAX = COMMAND_INOTIFY_ADD_WATCH
};
using BrokerCommandSet = std::bitset<COMMAND_MAX + 1>;
// Helper function since std::bitset lacks an initializer list constructor.
inline BrokerCommandSet MakeBrokerCommandSet(
const std::initializer_list<BrokerCommand>& args) {
BrokerCommandSet result;
for (const auto& arg : args)
result.set(arg);
return result;
}
// Helper functions to perform the same permissions test on either side
// (client or broker process) of a broker IPC command. The implementations
// must be safe when called from an async signal handler.
// They all return nullptr when permission checks fail.
[[nodiscard]] const char* CommandAccessIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename,
int requested_mode // e.g. F_OK, R_OK, W_OK.
);
[[nodiscard]] const char* CommandMkdirIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename);
[[nodiscard]] std::pair<const char*, bool> CommandOpenIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename,
int requested_flags // e.g. O_RDONLY, O_RDWR.
);
[[nodiscard]] const char* CommandReadlinkIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename);
[[nodiscard]] std::pair<const char*, const char*> CommandRenameIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* old_filename,
const char* new_filename);
[[nodiscard]] const char* CommandRmdirIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename);
[[nodiscard]] const char* CommandStatIsSafe(const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename);
[[nodiscard]] const char* CommandUnlinkIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename);
[[nodiscard]] const char* CommandInotifyAddWatchIsSafe(
const BrokerCommandSet& command_set,
const BrokerPermissionList& policy,
const char* requested_filename,
uint32_t mask);
} // namespace syscall_broker
} // namespace sandbox
#endif // SANDBOX_LINUX_SYSCALL_BROKER_BROKER_COMMAND_H_
|
