cros: Implement cryptohome backend for pin.

chrome/browser/chromeos/login/quick_unlock/pin_backend.cc

+// Copyright 2017 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 "chrome/browser/chromeos/login/quick_unlock/pin_backend.h"
+
+#include "base/bind.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "chrome/browser/chromeos/login/quick_unlock/pin_storage_prefs.h"
+#include "chrome/browser/chromeos/login/quick_unlock/quick_unlock_factory.h"
+#include "chrome/browser/chromeos/login/quick_unlock/quick_unlock_storage.h"
+#include "chrome/browser/chromeos/login/quick_unlock/quick_unlock_utils.h"
+#include "chromeos/cryptohome/cryptohome_parameters.h"
+#include "chromeos/cryptohome/homedir_methods.h"
+#include "chromeos/cryptohome/system_salt_getter.h"
+#include "chromeos/login/auth/user_context.h"
+#include "components/signin/core/account_id/account_id.h"
+
+namespace chromeos {
+namespace quick_unlock {
+
+namespace {
+
+constexpr const char* kCryptohomePinLabel = "pin_label";
+
+void DoNothingCryptohome(bool success, cryptohome::MountError return_code) {}
+
+class CryptohomeBackend {
+ public:
+  CryptohomeBackend();
+  ~CryptohomeBackend();
+
+  void EnsurePinIsNotInCryptohome(const AccountId& account_id,
+                                  const UserContext& user_context) const;
+  void IsPinSetInCryptohome(const AccountId& account_id,
+                            const PinBackend::BoolCallback& result) const;
+  void SetPin(const UserContext& user_context, const std::string& pin);
+  void RemovePin(const UserContext& user_context);
+  bool NeedsStrongAuth() const;
+
+ private:
+  void OnSystemSaltObtained(const std::string& system_salt);
+  // Called when we add or remove a key from cryptohome.
+  void OnCryptohomeKeyChange(bool success, cryptohome::MountError return_code);
+
+  void SetIsPinSet(bool is_set);
+
+ private:
+  bool salt_obtained_ = false;
+  std::string system_salt_;
+  std::vector<base::Closure> system_salt_callbacks_;
+
+  base::WeakPtrFactory<CryptohomeBackend> weak_factory_;

[achuithb, 2017/05/13 01:01:58]

You can do weak_factory_{this};
https://cs.chromium.org/chromium/src/chrome/browser/ui/views/chrome_views_del...

[jdufault, 2017/06/06 18:17:06]

Done - that's a nice pattern.

+
+  DISALLOW_COPY_AND_ASSIGN(CryptohomeBackend);
+};
+
+CryptohomeBackend::CryptohomeBackend() : weak_factory_(this) {
+  SystemSaltGetter::Get()->GetSystemSalt(base::Bind(
+      &CryptohomeBackend::OnSystemSaltObtained, weak_factory_.GetWeakPtr()));
+}
+
+CryptohomeBackend::~CryptohomeBackend() {}
+
+void CryptohomeBackend::IsPinSetInCryptohome(
+    const AccountId& account_id,
+    const PinBackend::BoolCallback& callback) const {
+  auto on_key_data =

[achuithb, 2017/05/13 01:01:58]

Let's maybe pull this out into a named callback? I haven't seen this many
lambdas in one CL.

[jdufault, 2017/06/06 18:17:06]

Done.

+      [](const PinBackend::BoolCallback& callback, bool success,
+         cryptohome::MountError return_code,
+         const std::vector<cryptohome::KeyDefinition>& key_definitions) {
+
+        for (const cryptohome::KeyDefinition& definition : key_definitions) {
+          if (definition.label == kCryptohomePinLabel) {
+            callback.Run(true);
+            return;
+          }
+        }
+
+        callback.Run(false);
+      };
+
+  cryptohome::HomedirMethods::GetInstance()->GetKeyDataEx(
+      cryptohome::Identification(account_id), kCryptohomePinLabel,
+      base::Bind(on_key_data, callback));
+}
+
+void CryptohomeBackend::SetPin(const UserContext& user_context,
+                               const std::string& pin) {
+  // Rerun this method only after we have system salt.
+  if (!salt_obtained_) {
+    system_salt_callbacks_.push_back(base::Bind(&CryptohomeBackend::SetPin,
+                                                weak_factory_.GetWeakPtr(),
+                                                user_context, pin));
+    return;
+  }
+
+  const std::string pin_secret = PinBackend::ComputeSecret(pin, system_salt_);
+
+  cryptohome::Identification id(user_context.GetAccountId());

[achuithb, 2017/05/13 01:01:58]

nit all const

[jdufault, 2017/06/06 18:17:06]

Done.

+  cryptohome::Authorization auth(user_context.GetKey()->GetSecret(), "");
+  cryptohome::KeyDefinition key_def(pin_secret, kCryptohomePinLabel,
+                                    cryptohome::PRIV_DEFAULT);
+  cryptohome::HomedirMethods::GetInstance()->AddKeyEx(
+      id, auth, key_def, true /*replace_existing*/,
+      base::Bind(&DoNothingCryptohome));
+}
+
+void CryptohomeBackend::OnSystemSaltObtained(const std::string& system_salt) {
+  salt_obtained_ = true;
+  system_salt_ = system_salt;
+  for (std::vector<base::Closure>::const_iterator it =

[achuithb, 2017/05/13 01:01:58]

Does range-based loop not work here?

[jdufault, 2017/06/06 18:17:06]

Done - not sure why I wasn't using it.

+           system_salt_callbacks_.begin();
+       it != system_salt_callbacks_.end(); ++it) {
+    it->Run();
+  }
+  system_salt_callbacks_.clear();
+}
+
+void CryptohomeBackend::RemovePin(const UserContext& user_context) {
+  // Rerun this method only after we have system salt.
+  if (!salt_obtained_) {
+    system_salt_callbacks_.push_back(base::Bind(&CryptohomeBackend::RemovePin,
+                                                weak_factory_.GetWeakPtr(),
+                                                user_context));
+    return;
+  }
+
+  // Remove any PIN data from cryptohome.
+  cryptohome::Identification id(user_context.GetAccountId());

[achuithb, 2017/05/13 01:01:58]

nit const

[jdufault, 2017/06/06 18:17:06]

Done.

+  cryptohome::Authorization auth(user_context.GetKey()->GetSecret(), "");
+  cryptohome::HomedirMethods::GetInstance()->RemoveKeyEx(
+      id, auth, kCryptohomePinLabel, base::Bind(&DoNothingCryptohome));
+}
+
+CryptohomeBackend* g_cryptohome_backend_ = nullptr;
+
+CryptohomeBackend* GetCryptohomeBackend() {
+  if (!g_cryptohome_backend_)
+    g_cryptohome_backend_ = new CryptohomeBackend();
+  return g_cryptohome_backend_;

[achuithb, 2017/05/13 01:01:58]

it's ok to leak this? 

Isn't there a singleton class we can use here instead?

[jdufault, 2017/06/06 18:17:06]

I tried converting to a leaky base::Singleton instance. For tests, we need the
ability to reset/destroy the singleton which base::Singleton does not appear to
support.

I think leaking is fine.

+}
+
+QuickUnlockStorage* GetPrefsBackend(const AccountId& account_id) {
+  return QuickUnlockFactory::GetForAccountId(account_id);
+}
+
+void SendResponse(const PinBackend::BoolCallback& result, bool value) {
+  base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                base::Bind(result, value));
+}
+
+}  // namespace
+
+// static
+void PinBackend::IsSet(const AccountId& account_id,
+                       const BoolCallback& result) {
+  if (GetPinStorageType() == PinStorageType::kCryptohome) {
+    GetCryptohomeBackend()->IsPinSetInCryptohome(account_id, result);
+  } else {
+    QuickUnlockStorage* storage = GetPrefsBackend(account_id);
+    DCHECK(storage);
+    SendResponse(result, storage->pin_storage_prefs()->IsPinSet());
+  }
+}
+
+// static
+void PinBackend::Set(const UserContext& user_context, const std::string& pin) {
+  QuickUnlockStorage* storage = GetPrefsBackend(user_context.GetAccountId());
+  DCHECK(storage);
+
+  // Make sure to remove the other storage pin.
+  if (GetPinStorageType() == PinStorageType::kCryptohome) {
+    GetCryptohomeBackend()->SetPin(user_context, pin);
+    storage->pin_storage_prefs()->RemovePin();
+  } else {
+    storage->pin_storage_prefs()->SetPin(pin);
+    GetCryptohomeBackend()->RemovePin(user_context);
+  }
+}
+
+// static
+void PinBackend::Remove(const UserContext& user_context) {
+  GetCryptohomeBackend()->RemovePin(user_context);
+
+  QuickUnlockStorage* storage = GetPrefsBackend(user_context.GetAccountId());
+  DCHECK(storage);
+  storage->pin_storage_prefs()->RemovePin();
+}
+
+// static
+void PinBackend::CanAuthenticate(const AccountId& account_id,
+                                 const BoolCallback& result) {
+  if (GetPinStorageType() == PinStorageType::kCryptohome) {
+    GetCryptohomeBackend()->IsPinSetInCryptohome(account_id, result);
+  } else {
+    QuickUnlockStorage* storage = GetPrefsBackend(account_id);
+    if (!storage) {
+      SendResponse(result, false);
+    } else {
+      SendResponse(
+          result,
+          storage->HasStrongAuth() &&
+              storage->pin_storage_prefs()->IsPinAuthenticationAvailable());
+    }
+  }
+}
+
+// static
+void PinBackend::TryAuthenticate(const AccountId& account_id,
+                                 const std::string& pin,
+                                 const BoolCallback& result) {
+  if (GetPinStorageType() == PinStorageType::kCryptohome) {
+    // TODO(jdufalt): Refactor login auth such that typing a user password does
+    // not run crypthome check with wildcard key label. That means we will be
+    // forced to run an authentication check here.
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  base::Bind(result, false));
+  } else {
+    QuickUnlockStorage* storage = GetPrefsBackend(account_id);
+    DCHECK(storage);
+
+    if (!storage->HasStrongAuth()) {
+      SendResponse(result, false);
+    } else {
+      SendResponse(result,
+                   storage->pin_storage_prefs()->TryAuthenticatePin(pin));
+    }
+  }
+}
+
+// static
+void PinBackend::NotifyAuthentication(const AccountId& account_id) {
+  // Nothing to do for cryptohome backend.
+
+  if (GetPinStorageType() == PinStorageType::kPrefs) {
+    QuickUnlockStorage* storage = GetPrefsBackend(account_id);
+    if (!storage)
+      return;
+
+    storage->pin_storage_prefs()->ResetUnlockAttemptCount();
+  }
+}
+
+// static
+std::string PinBackend::ComputeSecret(const std::string& pin,
+                                      const std::string& salt) {
+  Key key(pin);
+  key.Transform(Key::KEY_TYPE_SALTED_SHA256_TOP_HALF, salt);
+  return key.GetSecret();
+}
+
+// static
+void PinBackend::ResetForTesting() {
+  if (g_cryptohome_backend_)
+    delete g_cryptohome_backend_;
+  g_cryptohome_backend_ = nullptr;
+}
+
+}  // namespace quick_unlock
+}  // namespace chromeos