1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 // Most of this code is copied from various classes in
6 // src/chrome/browser/policy. In particular, look at
8 // file_based_policy_loader.{h,cc}
9 // config_dir_policy_provider.{h,cc}
11 // This is a reduction of the functionality in those classes.
15 #include "remoting/host/policy_hack/policy_watcher.h"
17 #include "base/bind.h"
18 #include "base/compiler_specific.h"
19 #include "base/file_util.h"
20 #include "base/files/file_enumerator.h"
21 #include "base/files/file_path.h"
22 #include "base/files/file_path_watcher.h"
23 #include "base/json/json_file_value_serializer.h"
24 #include "base/memory/scoped_ptr.h"
25 #include "base/memory/weak_ptr.h"
26 #include "base/single_thread_task_runner.h"
27 #include "base/synchronization/waitable_event.h"
28 #include "base/time/time.h"
29 #include "base/values.h"
32 namespace policy_hack {
36 const base::FilePath::CharType kPolicyDir[] =
37 // Always read the Chrome policies (even on Chromium) so that policy
38 // enforcement can't be bypassed by running Chromium.
39 FILE_PATH_LITERAL("/etc/opt/chrome/policies/managed");
41 // Amount of time we wait for the files on disk to settle before trying to load
42 // them. This alleviates the problem of reading partially written files and
43 // makes it possible to batch quasi-simultaneous changes.
44 const int kSettleIntervalSeconds = 5;
48 class PolicyWatcherLinux : public PolicyWatcher {
50 PolicyWatcherLinux(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
51 const base::FilePath& config_dir)
52 : PolicyWatcher(task_runner),
53 config_dir_(config_dir),
57 virtual ~PolicyWatcherLinux() {}
60 virtual void StartWatchingInternal() OVERRIDE {
61 DCHECK(OnPolicyWatcherThread());
62 watcher_.reset(new base::FilePathWatcher());
64 if (!config_dir_.empty() &&
67 base::Bind(&PolicyWatcherLinux::OnFilePathChanged,
68 weak_factory_.GetWeakPtr()))) {
69 OnFilePathChanged(config_dir_, true);
72 // There might have been changes to the directory in the time between
73 // construction of the loader and initialization of the watcher. Call reload
74 // to detect if that is the case.
77 ScheduleFallbackReloadTask();
80 virtual void StopWatchingInternal() OVERRIDE {
81 DCHECK(OnPolicyWatcherThread());
83 // Stop watching for changes to files in the policies directory.
86 // Orphan any pending OnFilePathChanged tasks.
87 weak_factory_.InvalidateWeakPtrs();
91 void OnFilePathChanged(const base::FilePath& path, bool error) {
92 DCHECK(OnPolicyWatcherThread());
97 LOG(ERROR) << "PolicyWatcherLinux on " << path.value() << " failed.";
100 base::Time GetLastModification() {
101 DCHECK(OnPolicyWatcherThread());
102 base::Time last_modification = base::Time();
103 base::PlatformFileInfo file_info;
105 // If the path does not exist or points to a directory, it's safe to load.
106 if (!file_util::GetFileInfo(config_dir_, &file_info) ||
107 !file_info.is_directory) {
108 return last_modification;
111 // Enumerate the files and find the most recent modification timestamp.
112 base::FileEnumerator file_enumerator(config_dir_,
114 base::FileEnumerator::FILES);
115 for (base::FilePath config_file = file_enumerator.Next();
116 !config_file.empty();
117 config_file = file_enumerator.Next()) {
118 if (file_util::GetFileInfo(config_file, &file_info) &&
119 !file_info.is_directory) {
120 last_modification = std::max(last_modification,
121 file_info.last_modified);
125 return last_modification;
128 // Returns NULL if the policy dictionary couldn't be read.
129 scoped_ptr<DictionaryValue> Load() {
130 DCHECK(OnPolicyWatcherThread());
131 // Enumerate the files and sort them lexicographically.
132 std::set<base::FilePath> files;
133 base::FileEnumerator file_enumerator(config_dir_, false,
134 base::FileEnumerator::FILES);
135 for (base::FilePath config_file_path = file_enumerator.Next();
136 !config_file_path.empty(); config_file_path = file_enumerator.Next())
137 files.insert(config_file_path);
139 // Start with an empty dictionary and merge the files' contents.
140 scoped_ptr<DictionaryValue> policy(new DictionaryValue());
141 for (std::set<base::FilePath>::iterator config_file_iter = files.begin();
142 config_file_iter != files.end(); ++config_file_iter) {
143 JSONFileValueSerializer deserializer(*config_file_iter);
144 deserializer.set_allow_trailing_comma(true);
146 std::string error_msg;
147 scoped_ptr<Value> value(
148 deserializer.Deserialize(&error_code, &error_msg));
150 LOG(WARNING) << "Failed to read configuration file "
151 << config_file_iter->value() << ": " << error_msg;
152 return scoped_ptr<DictionaryValue>();
154 if (!value->IsType(Value::TYPE_DICTIONARY)) {
155 LOG(WARNING) << "Expected JSON dictionary in configuration file "
156 << config_file_iter->value();
157 return scoped_ptr<DictionaryValue>();
159 policy->MergeDictionary(static_cast<DictionaryValue*>(value.get()));
162 return policy.Pass();
165 virtual void Reload() OVERRIDE {
166 DCHECK(OnPolicyWatcherThread());
167 // Check the directory time in order to see whether a reload is required.
168 base::TimeDelta delay;
169 base::Time now = base::Time::Now();
170 if (!IsSafeToReloadPolicy(now, &delay)) {
171 ScheduleReloadTask(delay);
175 // Check again in case the directory has changed while reading it.
176 if (!IsSafeToReloadPolicy(now, &delay)) {
177 ScheduleReloadTask(delay);
181 // Load the policy definitions.
182 scoped_ptr<DictionaryValue> new_policy = Load();
183 if (new_policy.get()) {
184 UpdatePolicies(new_policy.get());
185 ScheduleFallbackReloadTask();
187 // A failure to load policy definitions is probably temporary, so try
189 ScheduleReloadTask(base::TimeDelta::FromSeconds(kSettleIntervalSeconds));
193 bool IsSafeToReloadPolicy(const base::Time& now, base::TimeDelta* delay) {
194 DCHECK(OnPolicyWatcherThread());
196 const base::TimeDelta kSettleInterval =
197 base::TimeDelta::FromSeconds(kSettleIntervalSeconds);
199 base::Time last_modification = GetLastModification();
200 if (last_modification.is_null())
203 if (last_modification_file_.is_null())
204 last_modification_file_ = last_modification;
206 // If there was a change since the last recorded modification, wait some
208 if (last_modification != last_modification_file_) {
209 last_modification_file_ = last_modification;
210 last_modification_clock_ = now;
211 *delay = kSettleInterval;
215 // Check whether the settle interval has elapsed.
216 base::TimeDelta age = now - last_modification_clock_;
217 if (age < kSettleInterval) {
218 *delay = kSettleInterval - age;
225 // Managed with a scoped_ptr rather than being declared as an inline member to
226 // decouple the watcher's life cycle from the PolicyWatcherLinux. This
227 // decoupling makes it possible to destroy the watcher before the loader's
228 // destructor is called (e.g. during Stop), since |watcher_| internally holds
229 // a reference to the loader and keeps it alive.
230 scoped_ptr<base::FilePathWatcher> watcher_;
232 // Records last known modification timestamp of |config_dir_|.
233 base::Time last_modification_file_;
235 // The wall clock time at which the last modification timestamp was
236 // recorded. It's better to not assume the file notification time and the
237 // wall clock times come from the same source, just in case there is some
238 // non-local filesystem involved.
239 base::Time last_modification_clock_;
241 const base::FilePath config_dir_;
243 // Allows us to cancel any inflight FileWatcher events or scheduled reloads.
244 base::WeakPtrFactory<PolicyWatcherLinux> weak_factory_;
247 PolicyWatcher* PolicyWatcher::Create(
248 scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
249 base::FilePath policy_dir(kPolicyDir);
250 return new PolicyWatcherLinux(task_runner, policy_dir);
253 } // namespace policy_hack
254 } // namespace remoting