1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "chromeos/printing/ppd_cache.h"
#include <string_view>
#include <utility>
#include <vector>
#include "base/files/file_util.h"
#include "base/functional/bind.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/synchronization/lock.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/thread_pool.h"
#include "base/threading/scoped_blocking_call.h"
#include "base/time/time.h"
#include "base/values.h"
#include "chromeos/printing/printing_constants.h"
#include "crypto/sha2.h"
#include "net/base/io_buffer.h"
#include "net/filter/gzip_header.h"
namespace chromeos {
namespace {
// Return the (full) path to the file we expect to find the given key at.
base::FilePath FilePathForKey(const base::FilePath& base_dir,
const std::string& key) {
return base_dir.Append(base::HexEncode(crypto::SHA256HashString(key)));
}
// If the cache doesn't already exist, create it.
void MaybeCreateCache(const base::FilePath& base_dir) {
if (!base::PathExists(base_dir)) {
base::CreateDirectory(base_dir);
}
}
// Find implementation, blocks on file access. Must be run on a thread that
// allows I/O.
PpdCache::FindResult FindImpl(const base::FilePath& cache_dir,
const std::string& key) {
base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
base::BlockingType::MAY_BLOCK);
PpdCache::FindResult result;
result.success = false;
if (!base::PathExists(cache_dir)) {
// If the cache dir was missing, we'll miss anyway.
return result;
}
base::File file(FilePathForKey(cache_dir, key),
base::File::FLAG_OPEN | base::File::FLAG_READ);
base::File::Info info;
if (!file.IsValid() || !file.GetInfo(&info))
return result;
if (info.size < static_cast<int64_t>(crypto::kSHA256Length) ||
info.size > static_cast<int64_t>(kMaxPpdSizeBytes) +
static_cast<int64_t>(crypto::kSHA256Length)) {
return result;
}
std::vector<char> buf(info.size);
if (file.ReadAtCurrentPos(buf.data(), info.size) != info.size)
return result;
std::string_view contents(buf.data(), info.size - crypto::kSHA256Length);
std::string_view checksum(buf.data() + info.size - crypto::kSHA256Length,
crypto::kSHA256Length);
if (crypto::SHA256HashString(contents) != checksum) {
LOG(ERROR) << "Bad checksum for cache key " << key;
return result;
}
result.success = true;
result.age = base::Time::Now() - info.last_modified;
result.contents = std::string(contents);
return result;
}
// Store implementation, blocks on file access. Must be run on a thread that
// allows I/O. If |age| is non-zero, explicitly set the age of the resulting
// file to be |age| before Now.
void StoreImpl(const base::FilePath& cache_dir,
const std::string& key,
const std::string& contents,
base::TimeDelta age) {
base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
base::BlockingType::MAY_BLOCK);
MaybeCreateCache(cache_dir);
if (contents.size() > kMaxPpdSizeBytes) {
LOG(ERROR) << "Ignoring attempt to cache large object";
return;
}
auto path = FilePathForKey(cache_dir, key);
base::File file(path,
base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
std::string checksum = crypto::SHA256HashString(contents);
if (!file.IsValid() ||
!file.WriteAtCurrentPosAndCheck(base::as_byte_span(contents)) ||
!file.WriteAtCurrentPosAndCheck(base::as_byte_span(checksum))) {
LOG(ERROR) << "Failed to create ppd cache file";
file.Close();
if (!base::DeleteFile(path)) {
LOG(ERROR) << "Failed to cleanup failed creation.";
}
return;
}
// Successfully wrote the file, adjust the age if requested.
if (!age.is_zero()) {
base::Time mod_time = base::Time::Now() - age;
file.SetTimes(mod_time, mod_time);
}
}
// Implementation of the PpdCache that uses two separate task runners for Store
// and Fetch since the two operations have different priorities. Note that the
// two operations are not sequenced so there should be no expectation that a
// call to Find will return a file that was previously Stored until the Store
// callback is run.
class PpdCacheImpl : public PpdCache {
public:
explicit PpdCacheImpl(
const base::FilePath& cache_base_dir,
scoped_refptr<base::SequencedTaskRunner> fetch_task_runner,
scoped_refptr<base::SequencedTaskRunner> store_task_runner)
: cache_base_dir_(cache_base_dir),
fetch_task_runner_(std::move(fetch_task_runner)),
store_task_runner_(std::move(store_task_runner)) {}
PpdCacheImpl(const PpdCacheImpl&) = delete;
PpdCacheImpl& operator=(const PpdCacheImpl&) = delete;
// Public API functions.
void Find(const std::string& key, FindCallback cb) override {
fetch_task_runner_->PostTaskAndReplyWithResult(
FROM_HERE, base::BindOnce(&FindImpl, cache_base_dir_, key),
std::move(cb));
}
// Store the given contents at the given key. If cb is non-null, it will
// be invoked on completion.
void Store(const std::string& key, const std::string& contents) override {
store_task_runner_->PostTask(
FROM_HERE, base::BindOnce(&StoreImpl, cache_base_dir_, key, contents,
base::TimeDelta()));
}
void StoreForTesting(const std::string& key,
const std::string& contents,
base::TimeDelta age) override {
store_task_runner_->PostTask(
FROM_HERE,
base::BindOnce(&StoreImpl, cache_base_dir_, key, contents, age));
}
private:
~PpdCacheImpl() override = default;
base::FilePath cache_base_dir_;
scoped_refptr<base::SequencedTaskRunner> fetch_task_runner_;
scoped_refptr<base::SequencedTaskRunner> store_task_runner_;
};
} // namespace
// static
scoped_refptr<PpdCache> PpdCache::Create(const base::FilePath& cache_base_dir) {
return scoped_refptr<PpdCache>(
new PpdCacheImpl(cache_base_dir,
base::ThreadPool::CreateSequencedTaskRunner(
{base::TaskPriority::USER_VISIBLE, base::MayBlock(),
base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN}),
base::ThreadPool::CreateSequencedTaskRunner(
{base::TaskPriority::BEST_EFFORT, base::MayBlock(),
base::TaskShutdownBehavior::BLOCK_SHUTDOWN})));
}
scoped_refptr<PpdCache> PpdCache::CreateForTesting(
const base::FilePath& cache_base_dir,
scoped_refptr<base::SequencedTaskRunner> io_task_runner) {
return scoped_refptr<PpdCache>(
new PpdCacheImpl(cache_base_dir, io_task_runner, io_task_runner));
}
} // namespace chromeos
|
