ChunkIterator.cpp revision 19c3315ce0ec83c4e7db1ba2eb5fd7ef2a50ccc5 
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    if (VerifyNextChunkNonFatal()) {
36      VerifyNextChunk();
37    }
38  }
39  return Chunk(this_chunk);
40}
41
42// TODO(b/111401637) remove this and have full resource file verification
43// Returns false if there was an error.
44bool ChunkIterator::VerifyNextChunkNonFatal() {
45  if (len_ < sizeof(ResChunk_header)) {
46    last_error_ = "not enough space for header";
47    last_error_was_fatal_ = false;
48    return false;
49  }
50  const size_t size = dtohl(next_chunk_->size);
51  if (size > len_) {
52    last_error_ = "chunk size is bigger than given data";
53    last_error_was_fatal_ = false;
54    return false;
55  }
56  return true;
57}
58
59// Returns false if there was an error.
60bool ChunkIterator::VerifyNextChunk() {
61  const uintptr_t header_start = reinterpret_cast<uintptr_t>(next_chunk_);
62
63  // This data must be 4-byte aligned, since we directly
64  // access 32-bit words, which must be aligned on
65  // certain architectures.
66  if (header_start & 0x03) {
67    last_error_ = "header not aligned on 4-byte boundary";
68    return false;
69  }
70
71  if (len_ < sizeof(ResChunk_header)) {
72    last_error_ = "not enough space for header";
73    return false;
74  }
75
76  const size_t header_size = dtohs(next_chunk_->headerSize);
77  const size_t size = dtohl(next_chunk_->size);
78  if (header_size < sizeof(ResChunk_header)) {
79    last_error_ = "header size too small";
80    return false;
81  }
82
83  if (header_size > size) {
84    last_error_ = "header size is larger than entire chunk";
85    return false;
86  }
87
88  if (size > len_) {
89    last_error_ = "chunk size is bigger than given data";
90    return false;
91  }
92
93  if ((size | header_size) & 0x03) {
94    last_error_ = "header sizes are not aligned on 4-byte boundary";
95    return false;
96  }
97  return true;
98}
99
100}  // namespace android
101