1 /*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef A_BASE_H_
18
19 #define A_BASE_H_
20
21 #ifndef ARRAY_SIZE
22 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))
23 #endif
24
25 #define DISALLOW_EVIL_CONSTRUCTORS(name) \
26 name(const name &); \
27 name &operator=(const name &)
28
29 /* Returns true if the size parameter is safe for new array allocation (32-bit)
30 *
31 * Example usage:
32 *
33 * if (!isSafeArraySize<uint32_t>(arraySize)) {
34 * return BAD_VALUE;
35 * }
36 * ...
37 * uint32_t *myArray = new uint32_t[arraySize];
38 *
39 * There is a bug in gcc versions earlier than 4.8 where the new[] array allocation
40 * will overflow in the internal 32 bit heap allocation, resulting in an
41 * underallocated array. This is a security issue that allows potential overwriting
42 * of other heap data.
43 *
44 * An alternative to checking is to create a safe new array template function which
45 * either throws a std::bad_alloc exception or returns NULL/nullptr_t; NULL considered
46 * safe since normal access of NULL throws an exception.
47 *
48 * https://securityblog.redhat.com/2012/10/31/array-allocation-in-cxx/
49 */
50 template <typename T, typename S>
isSafeArraySize(S size)51 bool isSafeArraySize(S size) {
52 return size >= 0 // in case S is signed, ignored if not.
53 && size <= 0xffffffff / sizeof(T); // max-unsigned-32-bit-int / element-size.
54 }
55
56 #endif // A_BASE_H_
57