1 //
2 // Copyright (C) 2018 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 "update_engine/payload_consumer/verity_writer_android.h"
18
19 #include <fcntl.h>
20
21 #include <algorithm>
22 #include <memory>
23
24 #include <base/logging.h>
25 #include <base/posix/eintr_wrapper.h>
26 #include <fec/ecc.h>
27 extern "C" {
28 #include <fec.h>
29 }
30
31 #include "update_engine/common/utils.h"
32 #include "update_engine/payload_consumer/cached_file_descriptor.h"
33 #include "update_engine/payload_consumer/file_descriptor.h"
34
35 namespace chromeos_update_engine {
36
37 namespace verity_writer {
CreateVerityWriter()38 std::unique_ptr<VerityWriterInterface> CreateVerityWriter() {
39 return std::make_unique<VerityWriterAndroid>();
40 }
41 } // namespace verity_writer
42
Init(const InstallPlan::Partition & partition)43 bool VerityWriterAndroid::Init(const InstallPlan::Partition& partition) {
44 partition_ = &partition;
45
46 if (partition_->hash_tree_size != 0) {
47 auto hash_function =
48 HashTreeBuilder::HashFunction(partition_->hash_tree_algorithm);
49 if (hash_function == nullptr) {
50 LOG(ERROR) << "Verity hash algorithm not supported: "
51 << partition_->hash_tree_algorithm;
52 return false;
53 }
54 hash_tree_builder_ = std::make_unique<HashTreeBuilder>(
55 partition_->block_size, hash_function);
56 TEST_AND_RETURN_FALSE(hash_tree_builder_->Initialize(
57 partition_->hash_tree_data_size, partition_->hash_tree_salt));
58 if (hash_tree_builder_->CalculateSize(partition_->hash_tree_data_size) !=
59 partition_->hash_tree_size) {
60 LOG(ERROR) << "Verity hash tree size does not match, stored: "
61 << partition_->hash_tree_size << ", calculated: "
62 << hash_tree_builder_->CalculateSize(
63 partition_->hash_tree_data_size);
64 return false;
65 }
66 }
67 total_offset_ = 0;
68 return true;
69 }
70
Update(const uint64_t offset,const uint8_t * buffer,size_t size)71 bool VerityWriterAndroid::Update(const uint64_t offset,
72 const uint8_t* buffer,
73 size_t size) {
74 if (offset != total_offset_) {
75 LOG(ERROR) << "Sequential read expected, expected to read at: "
76 << total_offset_ << " actual read occurs at: " << offset;
77 return false;
78 }
79 if (partition_->hash_tree_size != 0) {
80 const uint64_t hash_tree_data_end =
81 partition_->hash_tree_data_offset + partition_->hash_tree_data_size;
82 const uint64_t start_offset =
83 std::max(offset, partition_->hash_tree_data_offset);
84 if (offset + size > hash_tree_data_end) {
85 LOG(WARNING)
86 << "Reading past hash_tree_data_end, something is probably "
87 "wrong, might cause incorrect hash of partitions. offset: "
88 << offset << " size: " << size
89 << " hash_tree_data_end: " << hash_tree_data_end;
90 }
91 const uint64_t end_offset = std::min(offset + size, hash_tree_data_end);
92 if (start_offset < end_offset) {
93 TEST_AND_RETURN_FALSE(hash_tree_builder_->Update(
94 buffer + start_offset - offset, end_offset - start_offset));
95
96 if (end_offset == hash_tree_data_end) {
97 LOG(INFO)
98 << "Read everything before hash tree. Ready to write hash tree.";
99 }
100 }
101 }
102 total_offset_ += size;
103
104 return true;
105 }
106
Finalize(FileDescriptorPtr read_fd,FileDescriptorPtr write_fd)107 bool VerityWriterAndroid::Finalize(FileDescriptorPtr read_fd,
108 FileDescriptorPtr write_fd) {
109 const auto hash_tree_data_end =
110 partition_->hash_tree_data_offset + partition_->hash_tree_data_size;
111 if (total_offset_ < hash_tree_data_end) {
112 LOG(ERROR) << "Read up to " << total_offset_
113 << " when we are expecting to read everything "
114 "before "
115 << hash_tree_data_end;
116 return false;
117 }
118 // All hash tree data blocks has been hashed, write hash tree to disk.
119 LOG(INFO) << "Writing verity hash tree to " << partition_->target_path;
120 TEST_AND_RETURN_FALSE(hash_tree_builder_->BuildHashTree());
121 TEST_AND_RETURN_FALSE_ERRNO(
122 write_fd->Seek(partition_->hash_tree_offset, SEEK_SET));
123 auto success =
124 hash_tree_builder_->WriteHashTree([write_fd](auto data, auto size) {
125 return utils::WriteAll(write_fd, data, size);
126 });
127 // hashtree builder already prints error messages.
128 TEST_AND_RETURN_FALSE(success);
129 hash_tree_builder_.reset();
130 if (partition_->fec_size != 0) {
131 LOG(INFO) << "Writing verity FEC to " << partition_->target_path;
132 TEST_AND_RETURN_FALSE(EncodeFEC(read_fd,
133 write_fd,
134 partition_->fec_data_offset,
135 partition_->fec_data_size,
136 partition_->fec_offset,
137 partition_->fec_size,
138 partition_->fec_roots,
139 partition_->block_size,
140 false /* verify_mode */));
141 }
142 return true;
143 }
144
EncodeFEC(FileDescriptorPtr read_fd,FileDescriptorPtr write_fd,uint64_t data_offset,uint64_t data_size,uint64_t fec_offset,uint64_t fec_size,uint32_t fec_roots,uint32_t block_size,bool verify_mode)145 bool VerityWriterAndroid::EncodeFEC(FileDescriptorPtr read_fd,
146 FileDescriptorPtr write_fd,
147 uint64_t data_offset,
148 uint64_t data_size,
149 uint64_t fec_offset,
150 uint64_t fec_size,
151 uint32_t fec_roots,
152 uint32_t block_size,
153 bool verify_mode) {
154 TEST_AND_RETURN_FALSE(data_size % block_size == 0);
155 TEST_AND_RETURN_FALSE(fec_roots >= 0 && fec_roots < FEC_RSM);
156 // This is the N in RS(M, N), which is the number of bytes for each rs block.
157 size_t rs_n = FEC_RSM - fec_roots;
158 uint64_t rounds = utils::DivRoundUp(data_size / block_size, rs_n);
159 TEST_AND_RETURN_FALSE(rounds * fec_roots * block_size == fec_size);
160
161 std::unique_ptr<void, decltype(&free_rs_char)> rs_char(
162 init_rs_char(FEC_PARAMS(fec_roots)), &free_rs_char);
163 TEST_AND_RETURN_FALSE(rs_char != nullptr);
164
165 // Cache at most 1MB of fec data, in VABC, we need to re-open fd if we
166 // perform a read() operation after write(). So reduce the number of writes
167 // can save unnecessary re-opens.
168 write_fd = std::make_shared<CachedFileDescriptor>(write_fd, 1 * (1 << 20));
169 for (size_t i = 0; i < rounds; i++) {
170 // Encodes |block_size| number of rs blocks each round so that we can read
171 // one block each time instead of 1 byte to increase random read
172 // performance. This uses about 1 MiB memory for 4K block size.
173 brillo::Blob rs_blocks(block_size * rs_n);
174 for (size_t j = 0; j < rs_n; j++) {
175 brillo::Blob buffer(block_size, 0);
176 uint64_t offset =
177 fec_ecc_interleave(i * rs_n * block_size + j, rs_n, rounds);
178 // Don't read past |data_size|, treat them as 0.
179 if (offset < data_size) {
180 ssize_t bytes_read = 0;
181 TEST_AND_RETURN_FALSE(utils::PReadAll(read_fd,
182 buffer.data(),
183 buffer.size(),
184 data_offset + offset,
185 &bytes_read));
186 TEST_AND_RETURN_FALSE(bytes_read >= 0);
187 TEST_AND_RETURN_FALSE(static_cast<size_t>(bytes_read) == buffer.size());
188 }
189 for (size_t k = 0; k < buffer.size(); k++) {
190 rs_blocks[k * rs_n + j] = buffer[k];
191 }
192 }
193 brillo::Blob fec(block_size * fec_roots);
194 for (size_t j = 0; j < block_size; j++) {
195 // Encode [j * rs_n : (j + 1) * rs_n) in |rs_blocks| and write |fec_roots|
196 // number of parity bytes to |j * fec_roots| in |fec|.
197 encode_rs_char(rs_char.get(),
198 rs_blocks.data() + j * rs_n,
199 fec.data() + j * fec_roots);
200 }
201
202 if (verify_mode) {
203 brillo::Blob fec_read(fec.size());
204 ssize_t bytes_read = 0;
205 TEST_AND_RETURN_FALSE(utils::PReadAll(
206 read_fd, fec_read.data(), fec_read.size(), fec_offset, &bytes_read));
207 TEST_AND_RETURN_FALSE(bytes_read >= 0);
208 TEST_AND_RETURN_FALSE(static_cast<size_t>(bytes_read) == fec_read.size());
209 TEST_AND_RETURN_FALSE(fec == fec_read);
210 } else {
211 CHECK(write_fd);
212 write_fd->Seek(fec_offset, SEEK_SET);
213 if (!utils::WriteAll(write_fd, fec.data(), fec.size())) {
214 PLOG(ERROR) << "EncodeFEC write() failed";
215 return false;
216 }
217 }
218 fec_offset += fec.size();
219 }
220 write_fd->Flush();
221 return true;
222 }
223
EncodeFEC(const std::string & path,uint64_t data_offset,uint64_t data_size,uint64_t fec_offset,uint64_t fec_size,uint32_t fec_roots,uint32_t block_size,bool verify_mode)224 bool VerityWriterAndroid::EncodeFEC(const std::string& path,
225 uint64_t data_offset,
226 uint64_t data_size,
227 uint64_t fec_offset,
228 uint64_t fec_size,
229 uint32_t fec_roots,
230 uint32_t block_size,
231 bool verify_mode) {
232 FileDescriptorPtr fd(new EintrSafeFileDescriptor());
233 TEST_AND_RETURN_FALSE(
234 fd->Open(path.c_str(), verify_mode ? O_RDONLY : O_RDWR));
235 return EncodeFEC(fd,
236 fd,
237 data_offset,
238 data_size,
239 fec_offset,
240 fec_size,
241 fec_roots,
242 block_size,
243 verify_mode);
244 }
245 } // namespace chromeos_update_engine
246