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
|
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sandbox/linux/syscall_broker/broker_policy.h"
#include <fcntl.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <string>
#include <vector>
#include "base/logging.h"
#include "sandbox/linux/syscall_broker/broker_common.h"
namespace sandbox {
namespace syscall_broker {
BrokerPolicy::BrokerPolicy(int denied_errno,
const std::vector<BrokerFilePermission>& permissions)
: denied_errno_(denied_errno),
permissions_(permissions),
num_of_permissions_(permissions.size()) {
// The spec guarantees vectors store their elements contiguously
// so set up a pointer to array of element so it can be used
// in async signal safe code instead of vector operations.
if (num_of_permissions_ > 0) {
permissions_array_ = &permissions_[0];
} else {
permissions_array_ = NULL;
}
}
BrokerPolicy::~BrokerPolicy() {
}
// Check if calling access() should be allowed on |requested_filename| with
// mode |requested_mode|.
// Note: access() being a system call to check permissions, this can get a bit
// confusing. We're checking if calling access() should even be allowed with
// the same policy we would use for open().
// If |file_to_access| is not NULL, we will return the matching pointer from
// the whitelist. For paranoia a caller should then use |file_to_access|. See
// GetFileNameIfAllowedToOpen() for more explanation.
// return true if calling access() on this file should be allowed, false
// otherwise.
// Async signal safe if and only if |file_to_access| is NULL.
bool BrokerPolicy::GetFileNameIfAllowedToAccess(
const char* requested_filename,
int requested_mode,
const char** file_to_access) const {
if (file_to_access && *file_to_access) {
// Make sure that callers never pass a non-empty string. In case callers
// wrongly forget to check the return value and look at the string
// instead, this could catch bugs.
RAW_LOG(FATAL, "*file_to_access should be NULL");
return false;
}
for (size_t i = 0; i < num_of_permissions_; i++) {
if (permissions_array_[i].CheckAccess(requested_filename, requested_mode,
file_to_access)) {
return true;
}
}
return false;
}
// Check if |requested_filename| can be opened with flags |requested_flags|.
// If |file_to_open| is not NULL, we will return the matching pointer from the
// whitelist. For paranoia, a caller should then use |file_to_open| rather
// than |requested_filename|, so that it never attempts to open an
// attacker-controlled file name, even if an attacker managed to fool the
// string comparison mechanism.
// Return true if opening should be allowed, false otherwise.
// Async signal safe if and only if |file_to_open| is NULL.
bool BrokerPolicy::GetFileNameIfAllowedToOpen(const char* requested_filename,
int requested_flags,
const char** file_to_open,
bool* unlink_after_open) const {
if (file_to_open && *file_to_open) {
// Make sure that callers never pass a non-empty string. In case callers
// wrongly forget to check the return value and look at the string
// instead, this could catch bugs.
RAW_LOG(FATAL, "*file_to_open should be NULL");
return false;
}
for (size_t i = 0; i < num_of_permissions_; i++) {
if (permissions_array_[i].CheckOpen(requested_filename, requested_flags,
file_to_open, unlink_after_open)) {
return true;
}
}
return false;
}
} // namespace syscall_broker
} // namespace sandbox
|
