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