// Copyright 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.
#ifndef SYNC_UTIL_CRYPTOGRAPHER_H_
#define SYNC_UTIL_CRYPTOGRAPHER_H_
#include <map>
#include <string>
#include "base/gtest_prod_util.h"
#include "base/memory/linked_ptr.h"
#include "base/memory/scoped_ptr.h"
#include "sync/base/sync_export.h"
#include "sync/protocol/encryption.pb.h"
#include "sync/util/nigori.h"
namespace sync_pb {
class NigoriKeyBag;
class NigoriSpecifics;
}
namespace syncer {
class Encryptor;
SYNC_EXPORT_PRIVATE extern const char kNigoriTag[];
// The parameters used to initialize a Nigori instance.
struct KeyParams {
std::string hostname;
std::string username;
std::string password;
};
// This class manages the Nigori objects used to encrypt and decrypt sensitive
// sync data (eg. passwords). Each Nigori object knows how to handle data
// protected with a particular passphrase.
//
// Whenever an update to the Nigori sync node is received from the server,
// SetPendingKeys should be called with the encrypted contents of that node.
// Most likely, an updated Nigori node means that a new passphrase has been set
// and that future node updates won't be decryptable. To remedy this, the user
// should be prompted for the new passphrase and DecryptPendingKeys be called.
//
// Whenever a update to an encrypted node is received from the server,
// CanDecrypt should be used to verify whether the Cryptographer can decrypt
// that node. If it cannot, then the application of that update should be
// delayed until after it can be decrypted.
class SYNC_EXPORT Cryptographer {
public:
// Does not take ownership of |encryptor|.
explicit Cryptographer(Encryptor* encryptor);
~Cryptographer();
// |restored_bootstrap_token| can be provided via this method to bootstrap
// Cryptographer instance into the ready state (is_ready will be true).
// It must be a string that was previously built by the
// GetSerializedBootstrapToken function. It is possible that the token is no
// longer valid (due to server key change), in which case the normal
// decryption code paths will fail and the user will need to provide a new
// passphrase.
// It is an error to call this if is_ready() == true, though it is fair to
// never call Bootstrap at all.
void Bootstrap(const std::string& restored_bootstrap_token);
// Returns whether we can decrypt |encrypted| using the keys we currently know
// about.
bool CanDecrypt(const sync_pb::EncryptedData& encrypted) const;
// Returns whether |encrypted| can be decrypted using the default encryption
// key.
bool CanDecryptUsingDefaultKey(const sync_pb::EncryptedData& encrypted) const;
// Encrypts |message| into |encrypted|. Does not overwrite |encrypted| if
// |message| already matches the decrypted data within |encrypted| and
// |encrypted| was encrypted with the current default key. This avoids
// unnecessarily modifying |encrypted| if the change had no practical effect.
// Returns true unless encryption fails or |message| isn't valid (e.g. a
// required field isn't set).
bool Encrypt(const ::google::protobuf::MessageLite& message,
sync_pb::EncryptedData* encrypted) const;
// Encrypted |serialized| into |encrypted|. Does not overwrite |encrypted| if
// |message| already matches the decrypted data within |encrypted| and
// |encrypted| was encrypted with the current default key. This avoids
// unnecessarily modifying |encrypted| if the change had no practical effect.
// Returns true unless encryption fails or |message| isn't valid (e.g. a
// required field isn't set).
bool EncryptString(const std::string& serialized,
sync_pb::EncryptedData* encrypted) const;
// Decrypts |encrypted| into |message|. Returns true unless decryption fails,
// or |message| fails to parse the decrypted data.
bool Decrypt(const sync_pb::EncryptedData& encrypted,
::google::protobuf::MessageLite* message) const;
// Decrypts |encrypted| and returns plaintext decrypted data. If decryption
// fails, returns empty string.
std::string DecryptToString(const sync_pb::EncryptedData& encrypted) const;
// Encrypts the set of currently known keys into |encrypted|. Returns true if
// successful.
bool GetKeys(sync_pb::EncryptedData* encrypted) const;
// Creates a new Nigori instance using |params|. If successful, |params| will
// become the default encryption key and be used for all future calls to
// Encrypt.
// Will decrypt the pending keys and install them if possible (pending key
// will not overwrite default).
bool AddKey(const KeyParams& params);
// Same as AddKey(..), but builds the new Nigori from a previously persisted
// bootstrap token. This can be useful when consuming a bootstrap token
// with a cryptographer that has already been initialized.
// Updates the default key.
// Will decrypt the pending keys and install them if possible (pending key
// will not overwrite default).
bool AddKeyFromBootstrapToken(const std::string restored_bootstrap_token);
// Creates a new Nigori instance using |params|. If successful, |params|
// will be added to the nigori keybag, but will not be the default encryption
// key (default_nigori_ will remain the same).
// Prereq: is_initialized() must be true.
// Will decrypt the pending keys and install them if possible (pending key
// will become the new default).
bool AddNonDefaultKey(const KeyParams& params);
// Decrypts |encrypted| and uses its contents to initialize Nigori instances.
// Returns true unless decryption of |encrypted| fails. The caller is
// responsible for checking that CanDecrypt(encrypted) == true.
// Does not modify the default key.
void InstallKeys(const sync_pb::EncryptedData& encrypted);
// Makes a local copy of |encrypted| to later be decrypted by
// DecryptPendingKeys. This should only be used if CanDecrypt(encrypted) ==
// false.
void SetPendingKeys(const sync_pb::EncryptedData& encrypted);
// Makes |pending_keys_| available to callers that may want to cache its
// value for later use on the UI thread. It is illegal to call this if the
// cryptographer has no pending keys. Like other calls that access the
// cryptographer, this method must be called from within a transaction.
const sync_pb::EncryptedData& GetPendingKeys() const;
// Attempts to decrypt the set of keys that was copied in the previous call to
// SetPendingKeys using |params|. Returns true if the pending keys were
// successfully decrypted and installed. If successful, the default key
// is updated.
bool DecryptPendingKeys(const KeyParams& params);
// Sets the default key to the nigori with name |key_name|. |key_name| must
// correspond to a nigori that has already been installed into the keybag.
void SetDefaultKey(const std::string& key_name);
bool is_initialized() const {
return !nigoris_.empty() && !default_nigori_name_.empty();
}
// Returns whether this Cryptographer is ready to encrypt and decrypt data.
bool is_ready() const {
return is_initialized() && !has_pending_keys();
}
// Returns whether there is a pending set of keys that needs to be decrypted.
bool has_pending_keys() const { return NULL != pending_keys_.get(); }
// Obtain a token that can be provided on construction to a future
// Cryptographer instance to bootstrap itself. Returns false if such a token
// can't be created (i.e. if this Cryptograhper doesn't have valid keys).
bool GetBootstrapToken(std::string* token) const;
Encryptor* encryptor() const { return encryptor_; }
// Returns true if |keybag| is decryptable and either is a subset of nigoris_
// and/or has a different default key.
bool KeybagIsStale(const sync_pb::EncryptedData& keybag) const;
// Returns a serialized sync_pb::NigoriKey version of current default
// encryption key.
std::string GetDefaultNigoriKey() const;
// Generates a new Nigori from |serialized_nigori_key|, and if successful
// installs the new nigori as the default key.
bool ImportNigoriKey(const std::string serialized_nigori_key);
private:
typedef std::map<std::string, linked_ptr<const Nigori> > NigoriMap;
// Helper method to instantiate Nigori instances for each set of key
// parameters in |bag|.
// Does not update the default nigori.
void InstallKeyBag(const sync_pb::NigoriKeyBag& bag);
// Helper method to add a nigori to the keybag, optionally making it the
// default as well.
bool AddKeyImpl(scoped_ptr<Nigori> nigori, bool set_as_default);
// Helper to unencrypt a bootstrap token into a serialized sync_pb::NigoriKey.
std::string UnpackBootstrapToken(const std::string& token) const;
Encryptor* const encryptor_;
// The Nigoris we know about, mapped by key name.
NigoriMap nigoris_;
// The key name associated with the default nigori. If non-empty, must
// correspond to a nigori within |nigoris_|.
std::string default_nigori_name_;
scoped_ptr<sync_pb::EncryptedData> pending_keys_;
DISALLOW_COPY_AND_ASSIGN(Cryptographer);
};
} // namespace syncer
#endif // SYNC_UTIL_CRYPTOGRAPHER_H_