Linux pairing registry delegate implementation

BUG=156182

Review URL: https://chromiumcodereview.appspot.com/15709005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@208123 0039d316-1c4b-4281-b951-d872f2087c98

14 files changed, 520 insertions, 115 deletions

diff --git a/remoting/host/pairing_registry_delegate.h b/remoting/host/pairing_registry_delegate.h
new file mode 100644
index 0000000..95a4907
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate.h
@@ -0,0 +1,23 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_HOST_PAIRING_REGISTRY_DELEGATE_H_
+#define REMOTING_HOST_PAIRING_REGISTRY_DELEGATE_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "remoting/protocol/pairing_registry.h"
+
+namespace base {
+class TaskRunner;
+}  // namespace base
+
+namespace remoting {
+// Returns a platform-specific pairing registry delegate that will save to
+// permanent storage using the specified TaskRunner. Returns NULL on platforms
+// that don't support pairing.
+scoped_ptr<protocol::PairingRegistry::Delegate>
+CreatePairingRegistryDelegate(scoped_refptr<base::TaskRunner> task_runner);
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_PAIRING_REGISTRY_DELEGATE_H_
diff --git a/remoting/host/pairing_registry_delegate_linux.cc b/remoting/host/pairing_registry_delegate_linux.cc
new file mode 100644
index 0000000..bca9b4f
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate_linux.cc
@@ -0,0 +1,132 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/pairing_registry_delegate_linux.h"
+
+#include "base/bind.h"
+#include "base/file_util.h"
+#include "base/files/important_file_writer.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
+#include "remoting/host/branding.h"
+
+namespace {
+const char kRegistryFilename[] = "paired-clients.json";
+}  // namespace
+
+namespace remoting {
+
+using protocol::PairingRegistry;
+
+PairingRegistryDelegateLinux::PairingRegistryDelegateLinux(
+    scoped_refptr<base::TaskRunner> task_runner)
+    : task_runner_(task_runner),
+      weak_factory_(this) {
+}
+
+PairingRegistryDelegateLinux::~PairingRegistryDelegateLinux() {
+}
+
+void PairingRegistryDelegateLinux::Save(
+    const std::string& pairings_json,
+    const PairingRegistry::SaveCallback& callback) {
+  // If a callback was supplied, wrap it in a helper function that will
+  // run it on this thread.
+  PairingRegistry::SaveCallback run_callback_on_this_thread;
+  if (!callback.is_null()) {
+    run_callback_on_this_thread =
+        base::Bind(&PairingRegistryDelegateLinux::RunSaveCallbackOnThread,
+                   base::ThreadTaskRunnerHandle::Get(),
+                   callback);
+  }
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&PairingRegistryDelegateLinux::DoSave,
+                 weak_factory_.GetWeakPtr(),
+                 pairings_json,
+                 run_callback_on_this_thread));
+}
+
+void PairingRegistryDelegateLinux::Load(
+    const PairingRegistry::LoadCallback& callback) {
+  // Wrap the callback in a helper function that will run it on this thread.
+  // Note that, unlike AddPairing, the GetPairing callback is mandatory.
+  PairingRegistry::LoadCallback run_callback_on_this_thread =
+      base::Bind(&PairingRegistryDelegateLinux::RunLoadCallbackOnThread,
+                 base::ThreadTaskRunnerHandle::Get(),
+                 callback);
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&PairingRegistryDelegateLinux::DoLoad,
+                 weak_factory_.GetWeakPtr(),
+                 run_callback_on_this_thread));
+}
+
+void PairingRegistryDelegateLinux::RunSaveCallbackOnThread(
+    scoped_refptr<base::TaskRunner> task_runner,
+    const PairingRegistry::SaveCallback& callback,
+    bool success) {
+  task_runner->PostTask(FROM_HERE, base::Bind(callback, success));
+}
+
+void PairingRegistryDelegateLinux::RunLoadCallbackOnThread(
+      scoped_refptr<base::TaskRunner> task_runner,
+      const PairingRegistry::LoadCallback& callback,
+      const std::string& pairings_json) {
+  task_runner->PostTask(FROM_HERE, base::Bind(callback, pairings_json));
+}
+
+void PairingRegistryDelegateLinux::DoSave(
+    const std::string& pairings_json,
+    const PairingRegistry::SaveCallback& callback) {
+  base::FilePath registry_path = GetRegistryFilePath();
+  base::FilePath parent_directory = registry_path.DirName();
+  base::PlatformFileError error;
+  if (!file_util::CreateDirectoryAndGetError(parent_directory, &error)) {
+    LOG(ERROR) << "Could not create pairing registry directory: " << error;
+    return;
+  }
+  if (!base::ImportantFileWriter::WriteFileAtomically(registry_path,
+                                                      pairings_json)) {
+    LOG(ERROR) << "Could not save pairing registry.";
+  }
+
+  if (!callback.is_null()) {
+    callback.Run(true);
+  }
+}
+
+void PairingRegistryDelegateLinux::DoLoad(
+    const PairingRegistry::LoadCallback& callback) {
+  base::FilePath registry_path = GetRegistryFilePath();
+  std::string result;
+  if (!file_util::ReadFileToString(registry_path, &result)) {
+    LOG(ERROR) << "Load failed.";
+  }
+  callback.Run(result);
+}
+
+base::FilePath PairingRegistryDelegateLinux::GetRegistryFilePath() {
+  if (!filename_for_testing_.empty()) {
+    return filename_for_testing_;
+  }
+
+  base::FilePath config_dir = remoting::GetConfigDir();
+  return config_dir.Append(kRegistryFilename);
+}
+
+void PairingRegistryDelegateLinux::SetFilenameForTesting(
+    const base::FilePath &filename) {
+  filename_for_testing_ = filename;
+}
+
+
+scoped_ptr<PairingRegistry::Delegate> CreatePairingRegistryDelegate(
+    scoped_refptr<base::TaskRunner> task_runner) {
+  return scoped_ptr<PairingRegistry::Delegate>(
+      new PairingRegistryDelegateLinux(task_runner));
+}
+
+}  // namespace remoting
diff --git a/remoting/host/pairing_registry_delegate_linux.h b/remoting/host/pairing_registry_delegate_linux.h
new file mode 100644
index 0000000..08c073b
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate_linux.h
@@ -0,0 +1,73 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_PROTOCOL_PAIRING_REGISTRY_DELEGATE_LINUX_H_
+#define REMOTING_PROTOCOL_PAIRING_REGISTRY_DELEGATE_LINUX_H_
+
+#include "remoting/protocol/pairing_registry.h"
+
+#include "base/files/file_path.h"
+#include "base/memory/weak_ptr.h"
+
+namespace base {
+class ListValue;
+class TaskRunner;
+}  // namespace base
+
+namespace remoting {
+
+class PairingRegistryDelegateLinux
+    : public protocol::PairingRegistry::Delegate {
+ public:
+  explicit PairingRegistryDelegateLinux(
+      scoped_refptr<base::TaskRunner> task_runner);
+  virtual ~PairingRegistryDelegateLinux();
+
+  // PairingRegistry::Delegate interface
+  virtual void Save(
+      const std::string& pairings_json,
+      const protocol::PairingRegistry::SaveCallback& callback) OVERRIDE;
+  virtual void Load(
+      const protocol::PairingRegistry::LoadCallback& callback) OVERRIDE;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(PairingRegistryDelegateLinuxTest, SaveAndLoad);
+
+  // Blocking helper methods run using the TaskRunner passed to the ctor.
+  void DoSave(const std::string& pairings_json,
+              const protocol::PairingRegistry::SaveCallback& callback);
+  void DoLoad(const protocol::PairingRegistry::LoadCallback& callback);
+
+  // Run the delegate callbacks on their original thread.
+  static void RunSaveCallbackOnThread(
+      scoped_refptr<base::TaskRunner> task_runner,
+      const protocol::PairingRegistry::SaveCallback& callback,
+      bool success);
+  static void RunLoadCallbackOnThread(
+      scoped_refptr<base::TaskRunner> task_runner,
+      const protocol::PairingRegistry::LoadCallback& callback,
+      const std::string& pairings_json);
+
+  // Helper methods to load and save the pairing registry.
+  protocol::PairingRegistry::PairedClients LoadPairings();
+  void SavePairings(
+      const protocol::PairingRegistry::PairedClients& paired_clients);
+
+  // Return the path to the file to use for loading and saving paired clients.
+  base::FilePath GetRegistryFilePath();
+
+  // For testing purposes, set the path returned by |GetRegistryFilePath|.
+  void SetFilenameForTesting(const base::FilePath &filename);
+
+  scoped_refptr<base::TaskRunner> task_runner_;
+  base::FilePath filename_for_testing_;
+
+  base::WeakPtrFactory<PairingRegistryDelegateLinux> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PairingRegistryDelegateLinux);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_PROTOCOL_PAIRING_REGISTRY_DELEGATE_LINUX_H_
diff --git a/remoting/host/pairing_registry_delegate_linux_unittest.cc b/remoting/host/pairing_registry_delegate_linux_unittest.cc
new file mode 100644
index 0000000..4387f64
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate_linux_unittest.cc
@@ -0,0 +1,76 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/pairing_registry_delegate_linux.h"
+
+#include "base/file_util.h"
+#include "base/message_loop.h"
+#include "base/run_loop.h"
+#include "base/task_runner.h"
+#include "base/thread_task_runner_handle.h"
+#include "base/timer.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace remoting {
+
+using protocol::PairingRegistry;
+
+class PairingRegistryDelegateLinuxTest : public testing::Test {
+ public:
+  void SaveComplete(PairingRegistry::Delegate* delegate,
+                    const std::string& expected_json,
+                    bool success) {
+    EXPECT_TRUE(success);
+    // Load the pairings again to make sure we get what we've just written.
+    delegate->Load(
+        base::Bind(&PairingRegistryDelegateLinuxTest::VerifyLoad,
+                   base::Unretained(this),
+                   expected_json));
+  }
+
+  void VerifyLoad(const std::string& expected,
+                  const std::string& actual) {
+    EXPECT_EQ(actual, expected);
+    base::MessageLoop::current()->Quit();
+  }
+};
+
+TEST_F(PairingRegistryDelegateLinuxTest, SaveAndLoad) {
+  base::MessageLoop message_loop;
+  base::RunLoop run_loop;
+
+  // Create a temporary directory in order to get a unique name and use a
+  // subdirectory to ensure that the AddPairing method creates the parent
+  // directory if it doesn't exist.
+  base::FilePath temp_dir;
+  file_util::CreateNewTempDirectory("chromoting-test", &temp_dir);
+  base::FilePath temp_file = temp_dir.Append("dir").Append("registry.json");
+
+  scoped_refptr<base::TaskRunner> task_runner =
+      base::ThreadTaskRunnerHandle::Get();
+  scoped_ptr<PairingRegistryDelegateLinux> save_delegate(
+      new PairingRegistryDelegateLinux(task_runner));
+  scoped_ptr<PairingRegistryDelegateLinux> load_delegate(
+      new PairingRegistryDelegateLinux(task_runner));
+  save_delegate->SetFilenameForTesting(temp_file);
+  load_delegate->SetFilenameForTesting(temp_file);
+
+  // Save the pairings, then load them using a different delegate to ensure
+  // that the test isn't passing due to cached values. Note that the delegate
+  // doesn't require that the strings it loads and saves are valid JSON, so
+  // we can simplify the test a bit.
+  std::string test_data = "test data";
+  save_delegate->Save(
+      test_data,
+      base::Bind(&PairingRegistryDelegateLinuxTest::SaveComplete,
+                 base::Unretained(this),
+                 load_delegate.get(),
+                 test_data));
+
+  run_loop.Run();
+
+  file_util::Delete(temp_dir, true);
+};
+
+}  // namespace remoting
diff --git a/remoting/host/pairing_registry_delegate_mac.cc b/remoting/host/pairing_registry_delegate_mac.cc
new file mode 100644
index 0000000..602a068
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate_mac.cc
@@ -0,0 +1,18 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/pairing_registry_delegate.h"
+
+#include "base/task_runner.h"
+
+namespace remoting {
+
+using protocol::PairingRegistry;
+
+scoped_ptr<PairingRegistry::Delegate> CreatePairingRegistryDelegate(
+    scoped_refptr<base::TaskRunner> task_runner) {
+  return scoped_ptr<PairingRegistry::Delegate>();
+}
+
+}  // namespace remoting
diff --git a/remoting/host/pairing_registry_delegate_win.cc b/remoting/host/pairing_registry_delegate_win.cc
new file mode 100644
index 0000000..602a068
--- /dev/null
+++ b/remoting/host/pairing_registry_delegate_win.cc
@@ -0,0 +1,18 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/pairing_registry_delegate.h"
+
+#include "base/task_runner.h"
+
+namespace remoting {
+
+using protocol::PairingRegistry;
+
+scoped_ptr<PairingRegistry::Delegate> CreatePairingRegistryDelegate(
+    scoped_refptr<base::TaskRunner> task_runner) {
+  return scoped_ptr<PairingRegistry::Delegate>();
+}
+
+}  // namespace remoting
diff --git a/remoting/host/remoting_me2me_host.cc b/remoting/host/remoting_me2me_host.cc
index 9df3657..d684a86 100644
--- a/remoting/host/remoting_me2me_host.cc
+++ b/remoting/host/remoting_me2me_host.cc
@@ -57,6 +57,7 @@
 #include "remoting/host/log_to_server.h"
 #include "remoting/host/logging.h"
 #include "remoting/host/me2me_desktop_environment.h"
+#include "remoting/host/pairing_registry_delegate.h"
 #include "remoting/host/policy_hack/policy_watcher.h"
 #include "remoting/host/service_urls.h"
 #include "remoting/host/session_manager_factory.h"
@@ -478,12 +479,9 @@ void HostProcess::CreateAuthenticatorFactory() {
 
   // TODO(jamiewalch): Add a pairing registry here once all the code
   // is committed.
-  scoped_refptr<remoting::protocol::PairingRegistry> pairing_registry;
-  //scoped_refptr<protocol::PairingRegistry> pairing_registry(
-  //    new protocol::PairingRegistry(
-  //        scoped_ptr<protocol::PairingRegistry::Delegate>(
-  //            new protocol::NotImplementedPairingRegistryDelegate),
-  //        protocol::PairingRegistry::PairedClients()));
+  scoped_refptr<remoting::protocol::PairingRegistry> pairing_registry(
+      new remoting::protocol::PairingRegistry(
+          CreatePairingRegistryDelegate(NULL)));
 
   scoped_ptr<protocol::AuthenticatorFactory> factory;
 
diff --git a/remoting/protocol/negotiating_authenticator_unittest.cc b/remoting/protocol/negotiating_authenticator_unittest.cc
index fb7ed34..b746432 100644
--- a/remoting/protocol/negotiating_authenticator_unittest.cc
+++ b/remoting/protocol/negotiating_authenticator_unittest.cc
@@ -85,14 +85,14 @@ class NegotiatingAuthenticatorTest : public AuthenticatorTestBase {
 
   void CreatePairingRegistry(bool with_paired_client) {
     mock_delegate_ = new MockPairingRegistryDelegate;
+    pairing_registry_ = new PairingRegistry(
+        scoped_ptr<PairingRegistry::Delegate>(mock_delegate_));
     if (with_paired_client) {
       PairingRegistry::Pairing pairing(
           base::Time(), kTestClientName, kTestClientId, kTestPairedSecret);
-      mock_delegate_->AddPairing(pairing,
-                                 PairingRegistry::AddPairingCallback());
+      pairing_registry_->AddPairing(pairing);
+      mock_delegate_->RunCallback();
     }
-    pairing_registry_ = new PairingRegistry(
-        scoped_ptr<PairingRegistry::Delegate>(mock_delegate_));
   }
 
   static void FetchSecret(
diff --git a/remoting/protocol/pairing_registry.cc b/remoting/protocol/pairing_registry.cc
index 6c9cc66..558c302 100644
--- a/remoting/protocol/pairing_registry.cc
+++ b/remoting/protocol/pairing_registry.cc
@@ -7,8 +7,18 @@
 #include "base/base64.h"
 #include "base/bind.h"
 #include "base/guid.h"
+#include "base/json/json_string_value_serializer.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/values.h"
 #include "crypto/random.h"
 
+namespace {
+const char kCreatedTimeKey[] = "created-time";
+const char kClientIdKey[] = "client-id";
+const char kClientNameKey[] = "client-name";
+const char kSharedSecretKey[] = "shared-secret";
+}  // namespace
+
 namespace remoting {
 namespace protocol {
 
@@ -68,30 +78,101 @@ PairingRegistry::Pairing PairingRegistry::CreatePairing(
     const std::string& client_name) {
   DCHECK(CalledOnValidThread());
   Pairing result = Pairing::Create(client_name);
-  delegate_->AddPairing(result, AddPairingCallback());
+  AddPairing(result);
   return result;
 }
 
 void PairingRegistry::GetPairing(const std::string& client_id,
                                  const GetPairingCallback& callback) {
   DCHECK(CalledOnValidThread());
-  delegate_->GetPairing(client_id, callback);
+  delegate_->Load(
+      base::Bind(&PairingRegistry::DoGetPairing, this, client_id, callback));
+}
+
+void PairingRegistry::AddPairing(const Pairing& pairing) {
+  delegate_->Load(
+      base::Bind(&PairingRegistry::MergePairingAndSave, this, pairing));
+}
+
+void PairingRegistry::MergePairingAndSave(const Pairing& pairing,
+                                          const std::string& pairings_json) {
+  DCHECK(CalledOnValidThread());
+  PairedClients clients = DecodeJson(pairings_json);
+  clients[pairing.client_id()] = pairing;
+  std::string new_pairings_json = EncodeJson(clients);
+  delegate_->Save(new_pairings_json, SaveCallback());
 }
 
-void NotImplementedPairingRegistryDelegate::AddPairing(
-    const PairingRegistry::Pairing& new_paired_client,
-    const PairingRegistry::AddPairingCallback& callback) {
-  NOTIMPLEMENTED();
-  if (!callback.is_null()) {
-    callback.Run(false);
+void PairingRegistry::DoGetPairing(const std::string& client_id,
+                                   const GetPairingCallback& callback,
+                                   const std::string& pairings_json) {
+  PairedClients clients = DecodeJson(pairings_json);
+  Pairing result = clients[client_id];
+  callback.Run(result);
+}
+
+PairingRegistry::PairedClients PairingRegistry::DecodeJson(
+    const std::string& pairings_json) {
+  PairedClients result;
+
+  if (pairings_json.empty()) {
+    return result;
+  }
+
+  JSONStringValueSerializer registry(pairings_json);
+  int error_code;
+  std::string error_message;
+  scoped_ptr<base::Value> root(
+      registry.Deserialize(&error_code, &error_message));
+  if (!root) {
+    LOG(ERROR) << "Failed to load paired clients: " << error_message
+               << " (" << error_code << ").";
+    return result;
   }
+
+  base::ListValue* root_list = NULL;
+  if (!root->GetAsList(&root_list)) {
+    LOG(ERROR) << "Failed to load paired clients: root node is not a list.";
+    return result;
+  }
+
+  for (size_t i = 0; i < root_list->GetSize(); ++i) {
+    base::DictionaryValue* pairing = NULL;
+    std::string client_name, client_id, shared_secret;
+    double created_time_value;
+    if (root_list->GetDictionary(i, &pairing) &&
+        pairing->GetDouble(kCreatedTimeKey, &created_time_value) &&
+        pairing->GetString(kClientNameKey, &client_name) &&
+        pairing->GetString(kClientIdKey, &client_id) &&
+        pairing->GetString(kSharedSecretKey, &shared_secret)) {
+      base::Time created_time = base::Time::FromJsTime(created_time_value);
+      result[client_id] = Pairing(
+          created_time, client_name, client_id, shared_secret);
+    } else {
+      LOG(ERROR) << "Paired client " << i << " has unexpected format.";
+    }
+  }
+
+  return result;
 }
 
-void NotImplementedPairingRegistryDelegate::GetPairing(
-    const std::string& client_id,
-    const PairingRegistry::GetPairingCallback& callback) {
-  NOTIMPLEMENTED();
-  callback.Run(PairingRegistry::Pairing());
+std::string PairingRegistry::EncodeJson(const PairedClients& clients) {
+  base::ListValue root;
+  for (PairedClients::const_iterator i = clients.begin();
+       i != clients.end(); ++i) {
+    base::DictionaryValue* pairing = new base::DictionaryValue();
+    pairing->SetDouble(kCreatedTimeKey, i->second.created_time().ToJsTime());
+    pairing->SetString(kClientNameKey, i->second.client_name());
+    pairing->SetString(kClientIdKey, i->second.client_id());
+    pairing->SetString(kSharedSecretKey, i->second.shared_secret());
+    root.Append(pairing);
+  }
+
+  std::string result;
+  JSONStringValueSerializer serializer(&result);
+  serializer.Serialize(root);
+
+  return result;
 }
 
 }  // namespace protocol
diff --git a/remoting/protocol/pairing_registry.h b/remoting/protocol/pairing_registry.h
index 3544524..0938d4e 100644
--- a/remoting/protocol/pairing_registry.h
+++ b/remoting/protocol/pairing_registry.h
@@ -17,9 +17,6 @@
 namespace remoting {
 namespace protocol {
 
-// TODO(jamiewalch): This class is little more than a wrapper around the
-// Pairing and Delegate classes. Refactor it away.
-
 // PairingRegistry holds information about paired clients to support
 // PIN-less authentication. For each paired client, the registry holds
 // the following information:
@@ -62,62 +59,63 @@ class PairingRegistry : public base::RefCountedThreadSafe<PairingRegistry>,
   typedef std::map<std::string, Pairing> PairedClients;
 
   // Delegate callbacks.
-  typedef base::Callback<void(Pairing client_information)> GetPairingCallback;
-  typedef base::Callback<void(bool success)> AddPairingCallback;
+  typedef base::Callback<void(const std::string& pairings_json)> LoadCallback;
+  typedef base::Callback<void(bool success)> SaveCallback;
+  typedef base::Callback<void(Pairing pariring)> GetPairingCallback;
 
   // Interface representing the persistent storage back-end.
   class Delegate {
    public:
     virtual ~Delegate() {}
 
-    // Add pairing information to persistent storage. If a non-NULL callback
-    // is provided, invoke it on completion to indicate success or failure.
-    // Must not block.
-    //
-    // TODO(jamiewalch): Plumb the callback into the RequestPairing flow so
-    // that the client isn't sent the pairing information until it has been
-    // saved.
-    virtual void AddPairing(const Pairing& new_paired_client,
-                            const AddPairingCallback& callback) = 0;
-
-    // Retrieve the Pairing for the specified client id. If none is found,
-    // invoke the callback with a default pairing. Must not block.
-    virtual void GetPairing(const std::string& client_id,
-                            const GetPairingCallback& callback) = 0;
+    // Save JSON-encoded pairing information to persistent storage. If
+    // a non-NULL callback is provided, invoke it on completion to
+    // indicate success or failure. Must not block.
+    virtual void Save(const std::string& pairings_json,
+                      const SaveCallback& callback) = 0;
+
+    // Retrieve the JSON-encoded pairing information from persistent
+    // storage. Must not block.
+    virtual void Load(const LoadCallback& callback) = 0;
   };
 
   explicit PairingRegistry(scoped_ptr<Delegate> delegate);
 
-  // Create a pairing for a new client and save it to disk.
+  // Creates a pairing for a new client and saves it to disk.
+  //
+  // TODO(jamiewalch): Plumb the Save callback into the RequestPairing flow
+  // so that the client isn't sent the pairing information until it has been
+  // saved.
   Pairing CreatePairing(const std::string& client_name);
 
-  // Get the pairing for the specified client id. See the corresponding
-  // Delegate method for details.
+  // Gets the pairing for the specified client id. See the corresponding
+  // Delegate method for details. If none is found, the callback is invoked
+  // with an invalid Pairing.
   void GetPairing(const std::string& client_id,
                   const GetPairingCallback& callback);
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(PairingRegistryTest, AddPairing);
+  friend class NegotiatingAuthenticatorTest;
   friend class base::RefCountedThreadSafe<PairingRegistry>;
 
   virtual ~PairingRegistry();
 
+  void AddPairing(const Pairing& pairing);;
+  void MergePairingAndSave(const Pairing& pairing,
+                           const std::string& pairings_json);
+  void DoGetPairing(const std::string& client_id,
+                    const GetPairingCallback& callback,
+                    const std::string& pairings_json);
+
+  static PairedClients DecodeJson(const std::string& pairings_json);
+  static std::string EncodeJson(const PairedClients& clients);
+
   scoped_ptr<Delegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(PairingRegistry);
 };
 
-// Temporary delegate that just logs NOTIMPLEMENTED for Load/Save.
-// TODO(jamiewalch): Delete once Delegates are implemented for all platforms.
-class NotImplementedPairingRegistryDelegate : public PairingRegistry::Delegate {
- public:
-  virtual void AddPairing(
-      const PairingRegistry::Pairing& paired_clients,
-      const PairingRegistry::AddPairingCallback& callback) OVERRIDE;
-  virtual void GetPairing(
-      const std::string& client_id,
-      const PairingRegistry::GetPairingCallback& callback) OVERRIDE;
-};
-
 }  // namespace protocol
 }  // namespace remoting
 
diff --git a/remoting/protocol/pairing_registry_unittest.cc b/remoting/protocol/pairing_registry_unittest.cc
index a5d8bf2..460acbe 100644
--- a/remoting/protocol/pairing_registry_unittest.cc
+++ b/remoting/protocol/pairing_registry_unittest.cc
@@ -17,57 +17,47 @@ namespace protocol {
 
 class PairingRegistryTest : public testing::Test {
  public:
-  virtual void SetUp() OVERRIDE {
-    got_secret_ = false;
-  }
-
   void CompareSecret(const std::string& expected,
                      PairingRegistry::Pairing actual) {
-    EXPECT_EQ(actual.shared_secret(), expected);
+    EXPECT_EQ(expected, actual.shared_secret());
+    secret_ = actual.shared_secret();
     got_secret_ = true;
   }
 
  protected:
+  std::string secret_;
   bool got_secret_;
 };
 
-TEST_F(PairingRegistryTest, GetPairing) {
-  PairingRegistry::Pairing client_info =
-      PairingRegistry::Pairing::Create("client_name");
+TEST_F(PairingRegistryTest, CreateAndGetPairings) {
   MockPairingRegistryDelegate* mock_delegate =
       new MockPairingRegistryDelegate();
-  mock_delegate->AddPairing(client_info, PairingRegistry::AddPairingCallback());
   scoped_ptr<PairingRegistry::Delegate> delegate(mock_delegate);
 
   scoped_refptr<PairingRegistry> registry(new PairingRegistry(delegate.Pass()));
+  PairingRegistry::Pairing pairing_1 = registry->CreatePairing("client_name");
+  mock_delegate->RunCallback();
+  PairingRegistry::Pairing pairing_2 = registry->CreatePairing("client_name");
+  mock_delegate->RunCallback();
 
-  registry->GetPairing(client_info.client_id(),
+  registry->GetPairing(pairing_1.client_id(),
                        base::Bind(&PairingRegistryTest::CompareSecret,
                                   base::Unretained(this),
-                                  client_info.shared_secret()));
+                                  pairing_1.shared_secret()));
+  got_secret_ = false;
   mock_delegate->RunCallback();
   EXPECT_TRUE(got_secret_);
-}
-
-TEST_F(PairingRegistryTest, AddPairing) {
-  MockPairingRegistryDelegate* mock_delegate =
-      new MockPairingRegistryDelegate();
-  scoped_ptr<PairingRegistry::Delegate> delegate(mock_delegate);
-
-  scoped_refptr<PairingRegistry> registry(new PairingRegistry(delegate.Pass()));
-
-  // Verify that we can create pairings from two clients with the same name, but
-  // that they aren't allocated the same client id.
-  PairingRegistry::Pairing pairing_1 = registry->CreatePairing("client_name");
-  PairingRegistry::Pairing pairing_2 = registry->CreatePairing("client_name");
+  std::string secret_1 = secret_;
 
-  const PairingRegistry::PairedClients& clients =
-      mock_delegate->paired_clients();
-  ASSERT_EQ(clients.size(), 2u);
-  PairingRegistry::Pairing first = clients.begin()->second;
-  PairingRegistry::Pairing second = (++clients.begin())->second;
-  EXPECT_EQ(first.client_name(), second.client_name());
-  EXPECT_NE(first.client_id(), second.client_id());
+  // Check that the second client is paired with a different shared secret.
+  registry->GetPairing(pairing_2.client_id(),
+                       base::Bind(&PairingRegistryTest::CompareSecret,
+                                  base::Unretained(this),
+                                  pairing_2.shared_secret()));
+  got_secret_ = false;
+  mock_delegate->RunCallback();
+  EXPECT_TRUE(got_secret_);
+  EXPECT_NE(secret_, secret_1);
 }
 
 }  // namespace protocol
diff --git a/remoting/protocol/protocol_mock_objects.cc b/remoting/protocol/protocol_mock_objects.cc
index 1902d83..f558769 100644
--- a/remoting/protocol/protocol_mock_objects.cc
+++ b/remoting/protocol/protocol_mock_objects.cc
@@ -54,31 +54,24 @@ MockPairingRegistryDelegate::MockPairingRegistryDelegate() {
 MockPairingRegistryDelegate::~MockPairingRegistryDelegate() {
 }
 
-void MockPairingRegistryDelegate::AddPairing(
-    const PairingRegistry::Pairing& new_paired_client,
-    const PairingRegistry::AddPairingCallback& callback) {
-  paired_clients_[new_paired_client.client_id()] = new_paired_client;
+void MockPairingRegistryDelegate::Save(
+    const std::string& pairings_json,
+    const PairingRegistry::SaveCallback& callback) {
+  pairings_json_ = pairings_json;
   if (!callback.is_null()) {
     callback.Run(true);
   }
 }
 
-void MockPairingRegistryDelegate::GetPairing(
-    const std::string& client_id,
-    const PairingRegistry::GetPairingCallback& callback) {
-  PairingRegistry::Pairing result;
-  PairingRegistry::PairedClients::const_iterator i =
-      paired_clients_.find(client_id);
-  if (i != paired_clients_.end()) {
-    result = i->second;
-  }
-  saved_callback_ = base::Bind(base::Bind(callback), result);
+void MockPairingRegistryDelegate::Load(
+    const PairingRegistry::LoadCallback& callback) {
+  load_callback_ = base::Bind(base::Bind(callback), pairings_json_);
 }
 
 void MockPairingRegistryDelegate::RunCallback() {
-  DCHECK(!saved_callback_.is_null());
-  saved_callback_.Run();
-  saved_callback_.Reset();
+  DCHECK(!load_callback_.is_null());
+  load_callback_.Run();
+  load_callback_.Reset();
 }
 
 }  // namespace protocol
diff --git a/remoting/protocol/protocol_mock_objects.h b/remoting/protocol/protocol_mock_objects.h
index 0f1e24d..84960fd 100644
--- a/remoting/protocol/protocol_mock_objects.h
+++ b/remoting/protocol/protocol_mock_objects.h
@@ -211,23 +211,22 @@ class MockPairingRegistryDelegate : public PairingRegistry::Delegate {
   MockPairingRegistryDelegate();
   virtual ~MockPairingRegistryDelegate();
 
-  const PairingRegistry::PairedClients& paired_clients() const {
-    return paired_clients_;
+  const std::string& pairings_json() const {
+    return pairings_json_;
   }
 
   // PairingRegistry::Delegate implementation.
-  virtual void AddPairing(
-      const PairingRegistry::Pairing& new_paired_client,
-      const PairingRegistry::AddPairingCallback& callback) OVERRIDE;
-  virtual void GetPairing(
-      const std::string& client_id,
-      const PairingRegistry::GetPairingCallback& callback) OVERRIDE;
+  virtual void Save(
+      const std::string& pairings_json,
+      const PairingRegistry::SaveCallback& callback) OVERRIDE;
+  virtual void Load(
+      const PairingRegistry::LoadCallback& callback) OVERRIDE;
 
   void RunCallback();
 
  private:
-  base::Closure saved_callback_;
-  PairingRegistry::PairedClients paired_clients_;
+  base::Closure load_callback_;
+  std::string pairings_json_;
 };
 
 }  // namespace protocol
diff --git a/remoting/remoting.gyp b/remoting/remoting.gyp
index f442e6e..6a3f099 100644
--- a/remoting/remoting.gyp
+++ b/remoting/remoting.gyp
@@ -413,6 +413,11 @@
             'host/me2me_desktop_environment.h',
             'host/mouse_clamping_filter.cc',
             'host/mouse_clamping_filter.h',
+            'host/pairing_registry_delegate.h',
+            'host/pairing_registry_delegate_linux.cc',
+            'host/pairing_registry_delegate_linux.h',
+            'host/pairing_registry_delegate_mac.cc',
+            'host/pairing_registry_delegate_win.cc',
             'host/pam_authorization_factory_posix.cc',
             'host/pam_authorization_factory_posix.h',
             'host/pin_hash.cc',
@@ -2647,6 +2652,7 @@
         'host/linux/x_server_clipboard_unittest.cc',
         'host/local_input_monitor_unittest.cc',
         'host/log_to_server_unittest.cc',
+        'host/pairing_registry_delegate_linux_unittest.cc',
         'host/pin_hash_unittest.cc',
         'host/policy_hack/fake_policy_watcher.cc',
         'host/policy_hack/fake_policy_watcher.h',