text: /*
      Copyright © 2017 by The qTox Project Contributors
  
      This file is part of qTox, a Qt-based graphical interface for Tox.
  
      qTox is libre software: you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation, either version 3 of the License, or
      (at your option) any later version.
  
      qTox is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.
  
      You should have received a copy of the GNU General Public License
      along with qTox.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  #include "toxencrypt.h"
  #include <tox/tox.h>  // TOX_VERSION_IS_API_COMPATIBLE
  #include <tox/toxencryptsave.h>
  
  #include <QByteArray>
  #include <QDebug>
  #include <QString>
  #include <memory>
  
  // functions for nice debug output
  static QString getKeyDerivationError(TOX_ERR_KEY_DERIVATION error);
  static QString getEncryptionError(TOX_ERR_ENCRYPTION error);
  static QString getDecryptionError(TOX_ERR_DECRYPTION error);
  static QString getSaltError(TOX_ERR_GET_SALT error);
  
  /**
    * @class ToxEncrypt
    * @brief Encapsulates the toxencrypsave API.
    * Since key derivation is work intensive and to avoid storing plaintext
    * passwords in memory, use a ToxEncrypt object and encrypt() or decrypt()
    * when you have to encrypt or decrypt more than once with the same password.
    */
  
  /**
   * @brief Frees the passKey before destruction.
   */
  ToxEncrypt::~ToxEncrypt()
  {
      tox_pass_key_free(passKey);
  }
  
  /**
   * @brief Constructs a ToxEncrypt object from a Tox_Pass_Key.
   * @param key Derived key to use for encryption and decryption.
   */
  ToxEncrypt::ToxEncrypt(Tox_Pass_Key* key)
      : passKey{key}
  {
  }
  
  /**
   * @brief  Gets the minimum number of bytes needed for isEncrypted()
   * @return Minimum number of bytes needed to check if data was encrypted
   *         using this module.
   */
  int ToxEncrypt::getMinBytes()
  {
      return TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
  }
  
  /**
   * @brief Checks if the data was encrypted by this module.
   * @param ciphertext The data to check.
   * @return True if the data was encrypted using this module, false otherwise.
   */
  bool ToxEncrypt::isEncrypted(const QByteArray& ciphertext)
  {
      if (ciphertext.length() < TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
          return false;
      }
  
      return tox_is_data_encrypted(reinterpret_cast<const uint8_t*>(ciphertext.constData()));
  }
  
  
  /**
   * @brief  Encrypts the plaintext with the given password.
   * @return Encrypted data or empty QByteArray on failure.
   * @param  password Password to encrypt the data.
   * @param  plaintext The data to encrypt.
   */
  QByteArray ToxEncrypt::encryptPass(const QString& password, const QByteArray& plaintext)
  {
      if (password.length() == 0) {
          qWarning() << "Empty password supplied, probably not what you intended.";
      }
  
      QByteArray pass = password.toUtf8();
      QByteArray ciphertext(plaintext.length() + TOX_PASS_ENCRYPTION_EXTRA_LENGTH, 0x00);
      TOX_ERR_ENCRYPTION error;
      tox_pass_encrypt(reinterpret_cast<const uint8_t*>(plaintext.constData()),
                       static_cast<size_t>(plaintext.size()),
                       reinterpret_cast<const uint8_t*>(pass.constData()),
                       static_cast<size_t>(pass.size()),
                       reinterpret_cast<uint8_t*>(ciphertext.data()), &error);
  
      if (error != TOX_ERR_ENCRYPTION_OK) {
          qCritical() << getEncryptionError(error);
          return QByteArray{};
      }
  
      return ciphertext;
  }
  
  
  /**
   * @brief  Decrypts data encrypted with this module.
   * @return The plaintext or an empty QByteArray on failure.
   * @param  password The password used to encrypt the data.
   * @param  ciphertext The encrypted data.
   */
  QByteArray ToxEncrypt::decryptPass(const QString& password, const QByteArray& ciphertext)
  {
      if (!isEncrypted(ciphertext)) {
          qWarning() << "The data was not encrypted using this module or it's corrupted.";
          return QByteArray{};
      }
  
      if (password.length() == 0) {
          qDebug() << "Empty password supplied, probably not what you intended.";
      }
  
      QByteArray pass = password.toUtf8();
      QByteArray plaintext(ciphertext.length() - TOX_PASS_ENCRYPTION_EXTRA_LENGTH, 0x00);
      TOX_ERR_DECRYPTION error;
      tox_pass_decrypt(reinterpret_cast<const uint8_t*>(ciphertext.constData()),
                       static_cast<size_t>(ciphertext.size()),
                       reinterpret_cast<const uint8_t*>(pass.constData()),
                       static_cast<size_t>(pass.size()), reinterpret_cast<uint8_t*>(plaintext.data()),
                       &error);
  
      if (error != TOX_ERR_DECRYPTION_OK) {
          qWarning() << getDecryptionError(error);
          return QByteArray{};
      }
  
      return plaintext;
  }
  
  /**
   * @brief  Factory method for the ToxEncrypt object.
   * @param  password Password to use for encryption.
   * @return A std::unique_ptr containing a ToxEncrypt object on success, or an
   *         or an empty std::unique_ptr on failure.
   *
   *  Derives a key from the password and a new random salt.
   */
  std::unique_ptr<ToxEncrypt> ToxEncrypt::makeToxEncrypt(const QString& password)
  {
      const QByteArray pass = password.toUtf8();
      TOX_ERR_KEY_DERIVATION error;
  #if TOX_VERSION_IS_API_COMPATIBLE(0, 2, 0)
      Tox_Pass_Key* const passKey = tox_pass_key_derive(
          reinterpret_cast<const uint8_t*>(pass.constData()),
          static_cast<size_t>(pass.length()), &error);
  #else
      Tox_Pass_Key* const passKey = tox_pass_key_new();
      tox_pass_key_derive(passKey, reinterpret_cast<const uint8_t*>(pass.constData()),
                          static_cast<size_t>(pass.length()), &error);
  #endif
  
      if (error != TOX_ERR_KEY_DERIVATION_OK) {
          tox_pass_key_free(passKey);
          qCritical() << getKeyDerivationError(error);
          return std::unique_ptr<ToxEncrypt>{};
      }
  
      return std::unique_ptr<ToxEncrypt>(new ToxEncrypt(passKey));
  }
  
  /**
   * @brief  Factory method for the ToxEncrypt object.
   * @param  password Password to use for encryption.
   * @param  toxSave The data to read the salt for decryption from.
   * @return A std::unique_ptr containing a ToxEncrypt object on success, or an
   *         or an empty std::unique_ptr on failure.
   *
   *  Derives a key from the password and the salt read from toxSave.
   */
  std::unique_ptr<ToxEncrypt> ToxEncrypt::makeToxEncrypt(const QString& password, const QByteArray& toxSave)
  {
      if (!isEncrypted(toxSave)) {
          qWarning() << "The data was not encrypted using this module or it's corrupted.";
          return std::unique_ptr<ToxEncrypt>{};
      }
  
      TOX_ERR_GET_SALT saltError;
      uint8_t salt[TOX_PASS_SALT_LENGTH];
      tox_get_salt(reinterpret_cast<const uint8_t*>(toxSave.constData()), salt, &saltError);
  
      if (saltError != TOX_ERR_GET_SALT_OK) {
          qWarning() << getSaltError(saltError);
          return std::unique_ptr<ToxEncrypt>{};
      }
  
      QByteArray pass = password.toUtf8();
      TOX_ERR_KEY_DERIVATION keyError;
  #if TOX_VERSION_IS_API_COMPATIBLE(0, 2, 0)
      Tox_Pass_Key* const passKey = tox_pass_key_derive_with_salt(
          reinterpret_cast<const uint8_t*>(pass.constData()),
          static_cast<size_t>(pass.length()), salt, &keyError);
  #else
      Tox_Pass_Key* const passKey = tox_pass_key_new();
      tox_pass_key_derive_with_salt(passKey, reinterpret_cast<const uint8_t*>(pass.constData()),
                                    static_cast<size_t>(pass.length()), salt, &keyError);
  #endif
  
      if (keyError != TOX_ERR_KEY_DERIVATION_OK) {
          tox_pass_key_free(passKey);
          qWarning() << getKeyDerivationError(keyError);
          return std::unique_ptr<ToxEncrypt>{};
      }
  
      return std::unique_ptr<ToxEncrypt>(new ToxEncrypt(passKey));
  }
  
  /**
   * @brief  Encrypts the plaintext with the stored key.
   * @return Encrypted data or empty QByteArray on failure.
   * @param  plaintext The data to encrypt.
   */
  QByteArray ToxEncrypt::encrypt(const QByteArray& plaintext) const
  {
      if (!passKey) {
          qCritical() << "The passKey is invalid.";
          return QByteArray{};
      }
  
      QByteArray ciphertext(plaintext.length() + TOX_PASS_ENCRYPTION_EXTRA_LENGTH, 0x00);
      TOX_ERR_ENCRYPTION error;
      tox_pass_key_encrypt(passKey, reinterpret_cast<const uint8_t*>(plaintext.constData()),
                           static_cast<size_t>(plaintext.size()),
                           reinterpret_cast<uint8_t*>(ciphertext.data()), &error);
  
      if (error != TOX_ERR_ENCRYPTION_OK) {
          qCritical() << getEncryptionError(error);
          return QByteArray{};
      }
  
      return ciphertext;
  }
  
  
  /**
   * @brief  Decrypts data encrypted with this module, using the stored key.
   * @return The plaintext or an empty QByteArray on failure.
   * @param  ciphertext The encrypted data.
   */
  QByteArray ToxEncrypt::decrypt(const QByteArray& ciphertext) const
  {
      if (!isEncrypted(ciphertext)) {
          qWarning() << "The data was not encrypted using this module or it's corrupted.";
          return QByteArray{};
      }
  
      QByteArray plaintext(ciphertext.length() - TOX_PASS_ENCRYPTION_EXTRA_LENGTH, 0x00);
      TOX_ERR_DECRYPTION error;
      tox_pass_key_decrypt(passKey, reinterpret_cast<const uint8_t*>(ciphertext.constData()),
                           static_cast<size_t>(ciphertext.size()),
                           reinterpret_cast<uint8_t*>(plaintext.data()), &error);
  
      if (error != TOX_ERR_DECRYPTION_OK) {
          qWarning() << getDecryptionError(error);
          return QByteArray{};
      }
  
      return plaintext;
  }
  
  /**
   * @brief Gets the error string for TOX_ERR_KEY_DERIVATION errors.
   * @param error The error number.
   * @return The verbose error message.
   */
  QString getKeyDerivationError(TOX_ERR_KEY_DERIVATION error)
  {
      switch (error) {
      case TOX_ERR_KEY_DERIVATION_OK:
          return QStringLiteral("The function returned successfully.");
      case TOX_ERR_KEY_DERIVATION_NULL:
          return QStringLiteral(
              "One of the arguments to the function was NULL when it was not expected.");
      case TOX_ERR_KEY_DERIVATION_FAILED:
          return QStringLiteral(
              "The crypto lib was unable to derive a key from the given passphrase.");
      default:
          return QStringLiteral("Unknown key derivation error.");
      }
  }
  
  /**
   * @brief Gets the error string for TOX_ERR_ENCRYPTION errors.
   * @param error The error number.
   * @return The verbose error message.
   */
  QString getEncryptionError(TOX_ERR_ENCRYPTION error)
  {
      switch (error) {
      case TOX_ERR_ENCRYPTION_OK:
          return QStringLiteral("The function returned successfully.");
      case TOX_ERR_ENCRYPTION_NULL:
          return QStringLiteral(
              "One of the arguments to the function was NULL when it was not expected.");
      case TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED:
          return QStringLiteral(
              "The crypto lib was unable to derive a key from the given passphrase.");
      case TOX_ERR_ENCRYPTION_FAILED:
          return QStringLiteral("The encryption itself failed.");
      default:
          return QStringLiteral("Unknown encryption error.");
      }
  }
  
  /**
   * @brief Gets the error string for TOX_ERR_DECRYPTION errors.
   * @param error The error number.
   * @return The verbose error message.
   */
  QString getDecryptionError(TOX_ERR_DECRYPTION error)
  {
      switch (error) {
      case TOX_ERR_DECRYPTION_OK:
          return QStringLiteral("The function returned successfully.");
      case TOX_ERR_DECRYPTION_NULL:
          return QStringLiteral(
              "One of the arguments to the function was NULL when it was not expected.");
      case TOX_ERR_DECRYPTION_INVALID_LENGTH:
          return QStringLiteral(
              "The input data was shorter than TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes.");
      case TOX_ERR_DECRYPTION_BAD_FORMAT:
          return QStringLiteral("The input data is missing the magic number or is corrupted.");
      default:
          return QStringLiteral("Unknown decryption error.");
      }
  }
  
  /**
   * @brief Gets the error string for TOX_ERR_GET_SALT errors.
   * @param error The error number.
   * @return The verbose error message.
   */
  QString getSaltError(TOX_ERR_GET_SALT error)
  {
      switch (error) {
      case TOX_ERR_GET_SALT_OK:
          return QStringLiteral("The function returned successfully.");
      case TOX_ERR_GET_SALT_NULL:
          return QStringLiteral(
              "One of the arguments to the function was NULL when it was not expected.");
      case TOX_ERR_GET_SALT_BAD_FORMAT:
          return QStringLiteral("The input data is missing the magic number or is corrupted.");
      default:
          return QStringLiteral("Unknown salt error.");
      }
  }
  