[Sync] Add SyncEncryptionHandler

sync/internal_api/sync_encryption_handler_impl.cc

Index: sync/internal_api/sync_encryption_handler_impl.cc
diff --git a/sync/internal_api/sync_encryption_handler_impl.cc b/sync/internal_api/sync_encryption_handler_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6ebe4a9f231cf239f0e851c778a54842185651cb
--- /dev/null
+++ b/sync/internal_api/sync_encryption_handler_impl.cc
@@ -0,0 +1,678 @@
+// Copyright (c) 2012 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 "sync/internal_api/sync_encryption_handler_impl.h"
+
+#include <queue>
+#include <string>
+
+#include "base/bind.h"
+#include "base/message_loop.h"
+#include "base/tracked_objects.h"
+#include "base/metrics/histogram.h"
+#include "sync/internal_api/public/read_node.h"
+#include "sync/internal_api/public/read_transaction.h"
+#include "sync/internal_api/public/user_share.h"
+#include "sync/internal_api/public/util/experiments.h"
+#include "sync/internal_api/public/write_node.h"
+#include "sync/internal_api/public/write_transaction.h"
+#include "sync/protocol/encryption.pb.h"
+#include "sync/protocol/nigori_specifics.pb.h"
+#include "sync/syncable/base_transaction.h"
+#include "sync/syncable/directory.h"
+#include "sync/syncable/entry.h"
+#include "sync/syncable/nigori_util.h"
+#include "sync/util/cryptographer.h"
+
+namespace syncer {
+
+namespace {
+// The maximum number of times we will automatically overwrite the nigori node
+// because the encryption keys don't match (per chrome instantiation).
+// We protect ourselves against nigori rollbacks, but it's possible two
+// different clients might have contrasting view of what the nigori node state
+// should be, in which case they might ping pong (see crbug.com/119207).
+static const int kNigoriOverwriteLimit = 10;
+}
+
+SyncEncryptionHandlerImpl::SyncEncryptionHandlerImpl(
+    UserShare* user_share,
+    Cryptographer* cryptographer)
+    : weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)),
+      user_share_(user_share),
+      cryptographer_(cryptographer),
+      encrypted_types_(SensitiveTypes()),
+      encrypt_everything_(false),
+      explicit_passphrase_(false),
+      nigori_overwrite_count_(0) {
+}
+
+SyncEncryptionHandlerImpl::~SyncEncryptionHandlerImpl() {}
+
+void SyncEncryptionHandlerImpl::AddObserver(Observer* observer) {
+  DCHECK(!observers_.HasObserver(observer));
+  observers_.AddObserver(observer);
+}
+
+void SyncEncryptionHandlerImpl::RemoveObserver(Observer* observer) {
+  DCHECK(observers_.HasObserver(observer));
+  observers_.RemoveObserver(observer);
+}
+
+void SyncEncryptionHandlerImpl::Init() {
+  WriteTransaction trans(FROM_HERE, user_share_);
+  WriteNode node(&trans);
+  Cryptographer* cryptographer = trans.GetCryptographer();
+  cryptographer_ = cryptographer;
+
+  if (node.InitByTagLookup(kNigoriTag) != BaseNode::INIT_OK)
+    return;
+  if (!ApplyNigoriUpdateImpl(node.GetNigoriSpecifics(),
+                             trans.GetWrappedTrans())) {
+    WriteEncryptionStateToNigori(&trans);
+  }
+
+  FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                    OnCryptographerStateChanged(cryptographer));
+
+  // If the cryptographer is not ready (either it has pending keys or we
+  // failed to initialize it), we don't want to try and re-encrypt the data.
+  // If we had encrypted types, the DataTypeManager will block, preventing
+  // sync from happening until the the passphrase is provided.
+  if (cryptographer->is_ready())
+    ReEncryptEverything(&trans);
+}
+
+// Note: this is called from within a syncable transaction, so we need to post
+// tasks if we want to do any work that creates a new sync_api transaction.
+void SyncEncryptionHandlerImpl::ApplyNigoriUpdate(
+    const sync_pb::NigoriSpecifics& nigori,
+    syncable::BaseTransaction* const trans) {
+  DCHECK(trans);
+  if (!ApplyNigoriUpdateImpl(nigori, trans)) {
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&SyncEncryptionHandlerImpl::RewriteNigori,
+                   weak_ptr_factory_.GetWeakPtr()));
+  }
+
+  FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                    OnCryptographerStateChanged(cryptographer_));
+}
+
+// Note: this is always called via the Cryptographer interface right now,
+// so a transaction is already held. Once we remove that interface, we'll
+// need to enforce holding a transaction when calling this method.
+ModelTypeSet SyncEncryptionHandlerImpl::GetEncryptedTypes() const {
+  return encrypted_types_;
+}
+
+void SyncEncryptionHandlerImpl::SetEncryptionPassphrase(
+    const std::string& passphrase,
+    bool is_explicit) {
+  // We do not accept empty passphrases.
+  if (passphrase.empty()) {
+    NOTREACHED() << "Cannot encrypt with an empty passphrase.";
+    return;
+  }
+
+  // All accesses to the cryptographer are protected by a transaction.
+  WriteTransaction trans(FROM_HERE, user_share_);
+  Cryptographer* cryptographer = trans.GetCryptographer();
+  KeyParams key_params = {"localhost", "dummy", passphrase};
+  WriteNode node(&trans);
+  if (node.InitByTagLookup(kNigoriTag) != BaseNode::INIT_OK) {
+    NOTREACHED();
+    return;
+  }
+
+  bool nigori_has_explicit_passphrase =
+      node.GetNigoriSpecifics().using_explicit_passphrase();
+  std::string bootstrap_token;
+  sync_pb::EncryptedData pending_keys;
+  if (cryptographer->has_pending_keys())
+    pending_keys = cryptographer->GetPendingKeys();
+  bool success = false;
+
+
+  // There are six cases to handle here:
+  // 1. The user has no pending keys and is setting their current GAIA password
+  //    as the encryption passphrase. This happens either during first time sync
+  //    with a clean profile, or after re-authenticating on a profile that was
+  //    already signed in with the cryptographer ready.
+  // 2. The user has no pending keys, and is overwriting an (already provided)
+  //    implicit passphrase with an explicit (custom) passphrase.
+  // 3. The user has pending keys for an explicit passphrase that is somehow set
+  //    to their current GAIA passphrase.
+  // 4. The user has pending keys encrypted with their current GAIA passphrase
+  //    and the caller passes in the current GAIA passphrase.
+  // 5. The user has pending keys encrypted with an older GAIA passphrase
+  //    and the caller passes in the current GAIA passphrase.
+  // 6. The user has previously done encryption with an explicit passphrase.
+  // Furthermore, we enforce the fact that the bootstrap encryption token will
+  // always be derived from the newest GAIA password if the account is using
+  // an implicit passphrase (even if the data is encrypted with an old GAIA
+  // password). If the account is using an explicit (custom) passphrase, the
+  // bootstrap token will be derived from the most recently provided explicit
+  // passphrase (that was able to decrypt the data).
+  if (!nigori_has_explicit_passphrase) {
+    if (!cryptographer->has_pending_keys()) {
+      if (cryptographer->AddKey(key_params)) {
+        // Case 1 and 2. We set a new GAIA passphrase when there are no pending
+        // keys (1), or overwriting an implicit passphrase with a new explicit
+        // one (2) when there are no pending keys.
+        DVLOG(1) << "Setting " << (is_explicit ? "explicit" : "implicit" )
+                 << " passphrase for encryption.";
+        cryptographer->GetBootstrapToken(&bootstrap_token);
+        success = true;
+      } else {
+        NOTREACHED() << "Failed to add key to cryptographer.";
+        success = false;
+      }
+    } else {  // cryptographer->has_pending_keys() == true
+      if (is_explicit) {
+        // This can only happen if the nigori node is updated with a new
+        // implicit passphrase while a client is attempting to set a new custom
+        // passphrase (race condition).
+        DVLOG(1) << "Failing because an implicit passphrase is already set.";
+        success = false;
+      } else {  // is_explicit == false
+        if (cryptographer->DecryptPendingKeys(key_params)) {
+          // Case 4. We successfully decrypted with the implicit GAIA passphrase
+          // passed in.
+          DVLOG(1) << "Implicit internal passphrase accepted for decryption.";
+          cryptographer->GetBootstrapToken(&bootstrap_token);
+          success = true;
+        } else {
+          // Case 5. Encryption was done with an old GAIA password, but we were
+          // provided with the current GAIA password. We need to generate a new
+          // bootstrap token to preserve it. We build a temporary cryptographer
+          // to allow us to extract these params without polluting our current
+          // cryptographer.
+          DVLOG(1) << "Implicit internal passphrase failed to decrypt, adding "
+                   << "anyways as default passphrase and persisting via "
+                   << "bootstrap token.";
+          Cryptographer temp_cryptographer(cryptographer->encryptor());
+          temp_cryptographer.AddKey(key_params);
+          temp_cryptographer.GetBootstrapToken(&bootstrap_token);
+          // We then set the new passphrase as the default passphrase of the
+          // real cryptographer, even though we have pending keys. This is safe,
+          // as although Cryptographer::is_initialized() will now be true,
+          // is_ready() will remain false due to having pending keys.
+          cryptographer->AddKey(key_params);
+          success = false;
+        }
+      }  // is_explicit
+    }  // cryptographer->has_pending_keys()
+  } else {  // nigori_has_explicit_passphrase == true
+    // Case 6. We do not want to override a previously set explicit passphrase,
+    // so we return a failure.
+    DVLOG(1) << "Failing because an explicit passphrase is already set.";
+    success = false;
+  }
+
+  DVLOG_IF(1, !success)
+      << "Failure in SetEncryptionPassphrase; notifying and returning.";
+  DVLOG_IF(1, success)
+      << "Successfully set encryption passphrase; updating nigori and "
+         "reencrypting.";
+
+  FinishSetPassphrase(
+      success, bootstrap_token, is_explicit, &trans, &node);
+}
+
+void SyncEncryptionHandlerImpl::SetDecryptionPassphrase(
+    const std::string& passphrase) {
+  // We do not accept empty passphrases.
+  if (passphrase.empty()) {
+    NOTREACHED() << "Cannot decrypt with an empty passphrase.";
+    return;
+  }
+
+  // All accesses to the cryptographer are protected by a transaction.
+  WriteTransaction trans(FROM_HERE, user_share_);
+  Cryptographer* cryptographer = trans.GetCryptographer();
+  KeyParams key_params = {"localhost", "dummy", passphrase};
+  WriteNode node(&trans);
+  if (node.InitByTagLookup(kNigoriTag) != BaseNode::INIT_OK) {
+    NOTREACHED();
+    return;
+  }
+
+  if (!cryptographer->has_pending_keys()) {
+    // Note that this *can* happen in a rare situation where data is
+    // re-encrypted on another client while a SetDecryptionPassphrase() call is
+    // in-flight on this client. It is rare enough that we choose to do nothing.
+    NOTREACHED() << "Attempt to set decryption passphrase failed because there "
+                 << "were no pending keys.";
+    return;
+  }
+
+  bool nigori_has_explicit_passphrase =
+      node.GetNigoriSpecifics().using_explicit_passphrase();
+  std::string bootstrap_token;
+  sync_pb::EncryptedData pending_keys;
+  pending_keys = cryptographer->GetPendingKeys();
+  bool success = false;
+
+  // There are three cases to handle here:
+  // 7. We're using the current GAIA password to decrypt the pending keys. This
+  //    happens when signing in to an account with a previously set implicit
+  //    passphrase, where the data is already encrypted with the newest GAIA
+  //    password.
+  // 8. The user is providing an old GAIA password to decrypt the pending keys.
+  //    In this case, the user is using an implicit passphrase, but has changed
+  //    their password since they last encrypted their data, and therefore
+  //    their current GAIA password was unable to decrypt the data. This will
+  //    happen when the user is setting up a new profile with a previously
+  //    encrypted account (after changing passwords).
+  // 9. The user is providing a previously set explicit passphrase to decrypt
+  //    the pending keys.
+  if (!nigori_has_explicit_passphrase) {
+    if (cryptographer->is_initialized()) {
+      // We only want to change the default encryption key to the pending
+      // one if the pending keybag already contains the current default.
+      // This covers the case where a different client re-encrypted
+      // everything with a newer gaia passphrase (and hence the keybag
+      // contains keys from all previously used gaia passphrases).
+      // Otherwise, we're in a situation where the pending keys are
+      // encrypted with an old gaia passphrase, while the default is the
+      // current gaia passphrase. In that case, we preserve the default.
+      Cryptographer temp_cryptographer(cryptographer->encryptor());
+      temp_cryptographer.SetPendingKeys(cryptographer->GetPendingKeys());
+      if (temp_cryptographer.DecryptPendingKeys(key_params)) {
+        // Check to see if the pending bag of keys contains the current
+        // default key.
+        sync_pb::EncryptedData encrypted;
+        cryptographer->GetKeys(&encrypted);
+        if (temp_cryptographer.CanDecrypt(encrypted)) {
+          DVLOG(1) << "Implicit user provided passphrase accepted for "
+                   << "decryption, overwriting default.";
+          // Case 7. The pending keybag contains the current default. Go ahead
+          // and update the cryptographer, letting the default change.
+          cryptographer->DecryptPendingKeys(key_params);
+          cryptographer->GetBootstrapToken(&bootstrap_token);
+          success = true;
+        } else {
+          // Case 8. The pending keybag does not contain the current default
+          // encryption key. We decrypt the pending keys here, and in
+          // FinishSetPassphrase, re-encrypt everything with the current GAIA
+          // passphrase instead of the passphrase just provided by the user.
+          DVLOG(1) << "Implicit user provided passphrase accepted for "
+                   << "decryption, restoring implicit internal passphrase "
+                   << "as default.";
+          std::string bootstrap_token_from_current_key;
+          cryptographer->GetBootstrapToken(
+              &bootstrap_token_from_current_key);
+          cryptographer->DecryptPendingKeys(key_params);
+          // Overwrite the default from the pending keys.
+          cryptographer->AddKeyFromBootstrapToken(
+              bootstrap_token_from_current_key);
+          success = true;
+        }
+      } else {  // !temp_cryptographer.DecryptPendingKeys(..)
+        DVLOG(1) << "Implicit user provided passphrase failed to decrypt.";
+        success = false;
+      }  // temp_cryptographer.DecryptPendingKeys(...)
+    } else {  // cryptographer->is_initialized() == false
+      if (cryptographer->DecryptPendingKeys(key_params)) {
+        // This can happpen in two cases:
+        // - First time sync on android, where we'll never have a
+        //   !user_provided passphrase.
+        // - This is a restart for a client that lost their bootstrap token.
+        // In both cases, we should go ahead and initialize the cryptographer
+        // and persist the new bootstrap token.
+        //
+        // Note: at this point, we cannot distinguish between cases 7 and 8
+        // above. This user provided passphrase could be the current or the
+        // old. But, as long as we persist the token, there's nothing more
+        // we can do.
+        cryptographer->GetBootstrapToken(&bootstrap_token);
+        DVLOG(1) << "Implicit user provided passphrase accepted, initializing"
+                 << " cryptographer.";
+        success = true;
+      } else {
+        DVLOG(1) << "Implicit user provided passphrase failed to decrypt.";
+        success = false;
+      }
+    }  // cryptographer->is_initialized()
+  } else {  // nigori_has_explicit_passphrase == true
+    // Case 9. Encryption was done with an explicit passphrase, and we decrypt
+    // with the passphrase provided by the user.
+    if (cryptographer->DecryptPendingKeys(key_params)) {
+      DVLOG(1) << "Explicit passphrase accepted for decryption.";
+      cryptographer->GetBootstrapToken(&bootstrap_token);
+      success = true;
+    } else {
+      DVLOG(1) << "Explicit passphrase failed to decrypt.";
+      success = false;
+    }
+  }  // nigori_has_explicit_passphrase
+
+  DVLOG_IF(1, !success)
+      << "Failure in SetDecryptionPassphrase; notifying and returning.";
+  DVLOG_IF(1, success)
+      << "Successfully set decryption passphrase; updating nigori and "
+         "reencrypting.";
+
+  FinishSetPassphrase(success,
+                      bootstrap_token,
+                      nigori_has_explicit_passphrase,
+                      &trans,
+                      &node);
+}
+
+void SyncEncryptionHandlerImpl::EnableEncryptEverything() {
+  if (encrypt_everything_) {
+    DCHECK(encrypted_types_.Equals(ModelTypeSet::All()));
+    return;
+  }
+  WriteTransaction trans(FROM_HERE, user_share_);
+  encrypt_everything_ = true;
+  // Change |encrypted_types_| directly to avoid sending more than one
+  // notification.
+  encrypted_types_ = ModelTypeSet::All();
+  FOR_EACH_OBSERVER(
+      Observer, observers_,
+      OnEncryptedTypesChanged(encrypted_types_, encrypt_everything_));
+  WriteEncryptionStateToNigori(&trans);
+  ReEncryptEverything(&trans);
+}
+
+bool SyncEncryptionHandlerImpl::EncryptEverythingEnabled() const {
+  ReadTransaction trans(FROM_HERE, user_share_);
+  return encrypt_everything_;
+}
+
+bool SyncEncryptionHandlerImpl::IsUsingExplicitPassphrase() const {
+  ReadTransaction trans(FROM_HERE, user_share_);
+  return explicit_passphrase_;
+}
+
+// This function iterates over all encrypted types.  There are many scenarios in
+// which data for some or all types is not currently available.  In that case,
+// the lookup of the root node will fail and we will skip encryption for that
+// type.
+void SyncEncryptionHandlerImpl::ReEncryptEverything(
+    WriteTransaction* trans) {
+  Cryptographer* cryptographer = trans->GetCryptographer();
+  if (!cryptographer->is_ready())
+    return;
+  ModelTypeSet encrypted_types = GetEncryptedTypes();
+  for (ModelTypeSet::Iterator iter = encrypted_types.First();
+       iter.Good(); iter.Inc()) {
+    if (iter.Get() == PASSWORDS || iter.Get() == NIGORI)
+      continue; // These types handle encryption differently.
+
+    ReadNode type_root(trans);
+    std::string tag = ModelTypeToRootTag(iter.Get());
+    if (type_root.InitByTagLookup(tag) != BaseNode::INIT_OK)
+      continue; // Don't try to reencrypt if the type's data is unavailable.
+
+    // Iterate through all children of this datatype.
+    std::queue<int64> to_visit;
+    int64 child_id = type_root.GetFirstChildId();
+    to_visit.push(child_id);
+    while (!to_visit.empty()) {
+      child_id = to_visit.front();
+      to_visit.pop();
+      if (child_id == kInvalidId)
+        continue;
+
+      WriteNode child(trans);
+      if (child.InitByIdLookup(child_id) != BaseNode::INIT_OK) {
+        NOTREACHED();
+        continue;
+      }
+      if (child.GetIsFolder()) {
+        to_visit.push(child.GetFirstChildId());
+      }
+      if (child.GetEntry()->Get(syncable::UNIQUE_SERVER_TAG).empty()) {
+      // Rewrite the specifics of the node with encrypted data if necessary
+      // (only rewrite the non-unique folders).
+        child.ResetFromSpecifics();
+      }
+      to_visit.push(child.GetSuccessorId());
+    }
+  }
+
+  // Passwords are encrypted with their own legacy scheme.  Passwords are always
+  // encrypted so we don't need to check GetEncryptedTypes() here.
+  ReadNode passwords_root(trans);
+  std::string passwords_tag = ModelTypeToRootTag(PASSWORDS);
+  if (passwords_root.InitByTagLookup(passwords_tag) ==
+          BaseNode::INIT_OK) {
+    int64 child_id = passwords_root.GetFirstChildId();
+    while (child_id != kInvalidId) {
+      WriteNode child(trans);
+      if (child.InitByIdLookup(child_id) != BaseNode::INIT_OK) {
+        NOTREACHED();
+        return;
+      }
+      child.SetPasswordSpecifics(child.GetPasswordSpecifics());
+      child_id = child.GetSuccessorId();
+    }
+  }
+
+  // NOTE: We notify from within a transaction.
+  FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                    OnEncryptionComplete());
+}
+
+bool SyncEncryptionHandlerImpl::ApplyNigoriUpdateImpl(
+    const sync_pb::NigoriSpecifics& nigori,
+    syncable::BaseTransaction* const trans) {
+  Cryptographer* cryptographer = trans->directory()->GetCryptographer(trans);
+  bool nigori_types_need_update = !UpdateEncryptedTypesFromNigori(nigori);
+  if (nigori.using_explicit_passphrase())
+    explicit_passphrase_ = true;
+
+  bool nigori_needs_new_keys = false;
+  if (!nigori.encrypted().blob().empty()) {
+    if (cryptographer->CanDecrypt(nigori.encrypted())) {
+      cryptographer->InstallKeys(nigori.encrypted());
+      // We only update the default passphrase if this was a new explicit
+      // passphrase. Else, since it was decryptable, it must not have been a new
+      // key.
+      if (nigori.using_explicit_passphrase())
+        cryptographer->SetDefaultKey(nigori.encrypted().key_name());
+
+      // Check if the cryptographer's keybag is newer than the nigori's
+      // keybag. If so, we need to overwrite the nigori node.
+      sync_pb::EncryptedData new_keys = nigori.encrypted();
+      if (!cryptographer->GetKeys(&new_keys))
+        NOTREACHED();
+      if (nigori.encrypted().SerializeAsString() !=
+          new_keys.SerializeAsString())
+        nigori_needs_new_keys = true;
+    } else {
+      cryptographer->SetPendingKeys(nigori.encrypted());
+    }
+  } else {
+    nigori_needs_new_keys = true;
+  }
+
+  // If we've completed a sync cycle and the cryptographer isn't ready
+  // yet or has pending keys, prompt the user for a passphrase.
+  if (cryptographer->has_pending_keys()) {
+    DVLOG(1) << "OnPassphraseRequired Sent";
+    sync_pb::EncryptedData pending_keys = cryptographer->GetPendingKeys();
+    FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                      OnPassphraseRequired(REASON_DECRYPTION,
+                                           pending_keys));
+  } else if (!cryptographer->is_ready()) {
+    DVLOG(1) << "OnPassphraseRequired sent because cryptographer is not "
+             << "ready";
+    FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                      OnPassphraseRequired(REASON_ENCRYPTION,
+                                           sync_pb::EncryptedData()));
+  }
+
+  // Check if the current local encryption state is stricter/newer than the
+  // nigori state. If so, we need to overwrite the nigori node with the local
+  // state.
+  if (nigori.using_explicit_passphrase() != explicit_passphrase_ ||
+      nigori.encrypt_everything() != encrypt_everything_ ||
+      nigori_types_need_update ||
+      nigori_needs_new_keys) {
+    return false;
+  }
+  return true;
+}
+
+void SyncEncryptionHandlerImpl::RewriteNigori() {
+  WriteTransaction trans(FROM_HERE, user_share_);
+  WriteEncryptionStateToNigori(&trans);
+}
+
+void SyncEncryptionHandlerImpl::WriteEncryptionStateToNigori(
+    WriteTransaction* trans) {
+  WriteNode nigori_node(trans);
+  // This can happen in tests that don't have nigori nodes.
+  if (!nigori_node.InitByTagLookup(kNigoriTag) == BaseNode::INIT_OK)
+    return;
+  sync_pb::NigoriSpecifics nigori = nigori_node.GetNigoriSpecifics();
+  Cryptographer* cryptographer = trans->GetCryptographer();
+  if (cryptographer->is_ready() &&
+      nigori_overwrite_count_ < kNigoriOverwriteLimit) {
+    // Does not modify the encrypted blob if the unencrypted data already
+    // matches what is about to be written.
+    sync_pb::EncryptedData original_keys = nigori.encrypted();
+    if (!cryptographer->GetKeys(nigori.mutable_encrypted()))
+      NOTREACHED();
+
+    if (nigori.encrypted().SerializeAsString() !=
+        original_keys.SerializeAsString()) {
+      // We've updated the nigori node's encryption keys. In order to prevent
+      // a possible looping of two clients constantly overwriting each other,
+      // we limit the absolute number of overwrites per client instantiation.
+      nigori_overwrite_count_++;
+      UMA_HISTOGRAM_COUNTS("Sync.AutoNigoriOverwrites",
+                           nigori_overwrite_count_);
+    }
+
+    // Note: we don't try to set using_explicit_passphrase here since if that
+    // is lost the user can always set it again. The main point is to preserve
+    // the encryption keys so all data remains decryptable.
+  }
+  syncable::UpdateNigoriFromEncryptedTypes(encrypted_types_,
+                                           encrypt_everything_,
+                                           &nigori);
+
+  // If nothing has changed, this is a no-op.
+  nigori_node.SetNigoriSpecifics(nigori);
+}
+
+bool SyncEncryptionHandlerImpl::UpdateEncryptedTypesFromNigori(
+    const sync_pb::NigoriSpecifics& nigori) {
+  if (nigori.encrypt_everything()) {
+    if (!encrypt_everything_) {
+      encrypt_everything_ = true;
+      encrypted_types_ = ModelTypeSet::All();
+      FOR_EACH_OBSERVER(
+          Observer, observers_,
+          OnEncryptedTypesChanged(encrypted_types_, encrypt_everything_));
+    }
+    DCHECK(encrypted_types_.Equals(ModelTypeSet::All()));
+    return true;
+  }
+
+  ModelTypeSet encrypted_types;
+  encrypted_types = syncable::GetEncryptedTypesFromNigori(nigori);
+  encrypted_types.PutAll(SensitiveTypes());
+
+  // If anything more than the sensitive types were encrypted, and
+  // encrypt_everything is not explicitly set to false, we assume it means
+  // a client intended to enable encrypt everything.
+  if (!nigori.has_encrypt_everything() &&
+      !Difference(encrypted_types, SensitiveTypes()).Empty()) {
+    if (!encrypt_everything_) {
+      encrypt_everything_ = true;
+      encrypted_types_ = ModelTypeSet::All();
+      FOR_EACH_OBSERVER(
+          Observer, observers_,
+          OnEncryptedTypesChanged(encrypted_types_, encrypt_everything_));
+    }
+    DCHECK(encrypted_types_.Equals(ModelTypeSet::All()));
+    return false;
+  }
+
+  MergeEncryptedTypes(encrypted_types);
+  return encrypted_types_.Equals(encrypted_types);
+}
+
+void SyncEncryptionHandlerImpl::UpdateNigoriFromEncryptedTypes(
+    sync_pb::NigoriSpecifics* nigori,
+    syncable::BaseTransaction* const trans) const {
+  syncable::UpdateNigoriFromEncryptedTypes(encrypted_types_,
+                                           encrypt_everything_,
+                                           nigori);
+}
+
+void SyncEncryptionHandlerImpl::FinishSetPassphrase(
+    bool success,
+    const std::string& bootstrap_token,
+    bool is_explicit,
+    WriteTransaction* trans,
+    WriteNode* nigori_node) {
+  Cryptographer* cryptographer = trans->GetCryptographer();
+  FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                    OnCryptographerStateChanged(cryptographer));
+
+  // It's possible we need to change the bootstrap token even if we failed to
+  // set the passphrase (for example if we need to preserve the new GAIA
+  // passphrase).
+  if (!bootstrap_token.empty()) {
+    DVLOG(1) << "Bootstrap token updated.";
+    FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                      OnBootstrapTokenUpdated(bootstrap_token));
+  }
+
+  if (!success) {
+    if (cryptographer->is_ready()) {
+      LOG(ERROR) << "Attempt to change passphrase failed while cryptographer "
+                 << "was ready.";
+    } else if (cryptographer->has_pending_keys()) {
+      FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                        OnPassphraseRequired(REASON_DECRYPTION,
+                                             cryptographer->GetPendingKeys()));
+    } else {
+      FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                        OnPassphraseRequired(REASON_ENCRYPTION,
+                                             sync_pb::EncryptedData()));
+    }
+    return;
+  }
+
+  FOR_EACH_OBSERVER(SyncEncryptionHandler::Observer, observers_,
+                    OnPassphraseAccepted());
+  DCHECK(cryptographer->is_ready());
+
+  sync_pb::NigoriSpecifics specifics(nigori_node->GetNigoriSpecifics());
+  // Does not modify specifics.encrypted() if the original decrypted data was
+  // the same.
+  if (!cryptographer->GetKeys(specifics.mutable_encrypted())) {
+    NOTREACHED();
+    return;
+  }
+  explicit_passphrase_ = is_explicit;
+  specifics.set_using_explicit_passphrase(is_explicit);
+  nigori_node->SetNigoriSpecifics(specifics);
+
+  // Does nothing if everything is already encrypted or the cryptographer has
+  // pending keys.
+  ReEncryptEverything(trans);
+}
+
+void SyncEncryptionHandlerImpl::MergeEncryptedTypes(
+    ModelTypeSet encrypted_types) {
+  if (!encrypted_types_.HasAll(encrypted_types)) {
+    encrypted_types_ = encrypted_types;
+    FOR_EACH_OBSERVER(
+        Observer, observers_,
+        OnEncryptedTypesChanged(encrypted_types_, encrypt_everything_));
+  }
+}
+
+}  // namespace browser_sync