1/*
2 * Copyright (C) 2016 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#include "androidfw/Chunk.h"
18
19#include "android-base/logging.h"
20
21namespace android {
22
23Chunk ChunkIterator::Next() {
24  CHECK(len_ != 0) << "called Next() after last chunk";
25
26  const ResChunk_header* this_chunk = next_chunk_;
27
28  // We've already checked the values of this_chunk, so safely increment.
29  next_chunk_ = reinterpret_cast<const ResChunk_header*>(
30      reinterpret_cast<const uint8_t*>(this_chunk) + dtohl(this_chunk->size));
31  len_ -= dtohl(this_chunk->size);
32
33  if (len_ != 0) {
34    // Prepare the next chunk.
35    VerifyNextChunk();
36  }
37  return Chunk(this_chunk);
38}
39
40// Returns false if there was an error.
41bool ChunkIterator::VerifyNextChunk() {
42  const uintptr_t header_start = reinterpret_cast<uintptr_t>(next_chunk_);
43
44  // This data must be 4-byte aligned, since we directly
45  // access 32-bit words, which must be aligned on
46  // certain architectures.
47  if (header_start & 0x03) {
48    last_error_ = "header not aligned on 4-byte boundary";
49    return false;
50  }
51
52  if (len_ < sizeof(ResChunk_header)) {
53    last_error_ = "not enough space for header";
54    return false;
55  }
56
57  const size_t header_size = dtohs(next_chunk_->headerSize);
58  const size_t size = dtohl(next_chunk_->size);
59  if (header_size < sizeof(ResChunk_header)) {
60    last_error_ = "header size too small";
61    return false;
62  }
63
64  if (header_size > size) {
65    last_error_ = "header size is larger than entire chunk";
66    return false;
67  }
68
69  if (size > len_) {
70    last_error_ = "chunk size is bigger than given data";
71    return false;
72  }
73
74  if ((size | header_size) & 0x03) {
75    last_error_ = "header sizes are not aligned on 4-byte boundary";
76    return false;
77  }
78  return true;
79}
80
81}  // namespace android
82