Replace "Master Key" with "Database Credentials"

Definitions:
* Database Key - Cryptographic hash used to perform encrypt/decrypt of the database.

* Database Credentials - User facing term to refer to the collection of Password, Key File, and/or Hardware Key used to derive the Database Key.

Changes:
* Remove the term "master" and "key" from the user's lexicon and clarify  the code base based on the definitions above.
* Clean up wording in the UI to be clearer to the end user.

src/gui/databasekey/KeyFileEditWidget.cpp

@@ -0,0 +1,148 @@
+/*
+ *  Copyright (C) 2018 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program is free 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 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "KeyFileEditWidget.h"
+#include "ui_KeyFileEditWidget.h"
+#include <gui/dbsettings/DatabaseSettingsWidget.h>
+
+#include "gui/FileDialog.h"
+#include "gui/MainWindow.h"
+#include "gui/MessageBox.h"
+#include "keys/CompositeKey.h"
+#include "keys/FileKey.h"
+
+KeyFileEditWidget::KeyFileEditWidget(DatabaseSettingsWidget* parent)
+    : KeyComponentWidget(parent)
+    , m_compUi(new Ui::KeyFileEditWidget())
+    , m_parent(parent)
+{
+    setComponentName(tr("Key File"));
+    setComponentDescription(tr("<p>You can add a key file containing random bytes for additional security.</p>"
+                               "<p>You must keep it secret and never lose it or you will be locked out!</p>"));
+}
+
+KeyFileEditWidget::~KeyFileEditWidget()
+{
+}
+
+bool KeyFileEditWidget::addToCompositeKey(QSharedPointer<CompositeKey> key)
+{
+    auto fileKey = QSharedPointer<FileKey>::create();
+    QString fileKeyName = m_compUi->keyFileCombo->currentText();
+    if (!fileKey->load(fileKeyName, nullptr)) {
+        return false;
+    }
+
+    if (fileKey->type() != FileKey::Hashed) {
+        QMessageBox::warning(getMainWindow(),
+                             tr("Legacy key file format"),
+                             tr("You are using a legacy key file format which may become\n"
+                                "unsupported in the future.\n\n"
+                                "Generate a new key file in the database security settings."),
+                             QMessageBox::Ok);
+    }
+
+    key->addKey(fileKey);
+    return true;
+}
+
+bool KeyFileEditWidget::validate(QString& errorMessage) const
+{
+    FileKey fileKey;
+    QString fileKeyError;
+    QString fileKeyName = m_compUi->keyFileCombo->currentText();
+    if (!fileKey.load(fileKeyName, &fileKeyError)) {
+        errorMessage = tr("Error loading the key file '%1'\nMessage: %2").arg(fileKeyName, fileKeyError);
+        return false;
+    }
+    return true;
+}
+
+QWidget* KeyFileEditWidget::componentEditWidget()
+{
+    m_compEditWidget = new QWidget();
+    m_compUi->setupUi(m_compEditWidget);
+
+    connect(m_compUi->createKeyFileButton, SIGNAL(clicked()), SLOT(createKeyFile()));
+    connect(m_compUi->browseKeyFileButton, SIGNAL(clicked()), SLOT(browseKeyFile()));
+
+    return m_compEditWidget;
+}
+
+void KeyFileEditWidget::initComponentEditWidget(QWidget* widget)
+{
+    Q_UNUSED(widget);
+    Q_ASSERT(m_compEditWidget);
+    m_compUi->keyFileCombo->setFocus();
+}
+
+void KeyFileEditWidget::createKeyFile()
+{
+    Q_ASSERT(m_compEditWidget);
+    if (!m_compEditWidget) {
+        return;
+    }
+    QString filters = QString("%1 (*.key);;%2 (*)").arg(tr("Key files"), tr("All files"));
+    QString fileName = fileDialog()->getSaveFileName(this, tr("Create Key File..."), QString(), filters);
+
+    if (!fileName.isEmpty()) {
+        QString errorMsg;
+        bool created = FileKey::create(fileName, &errorMsg);
+        if (!created) {
+            MessageBox::critical(getMainWindow(),
+                                 tr("Error creating key file"),
+                                 tr("Unable to create key file: %1").arg(errorMsg),
+                                 QMessageBox::Button::Ok);
+        } else {
+            m_compUi->keyFileCombo->setEditText(fileName);
+        }
+    }
+}
+
+void KeyFileEditWidget::browseKeyFile()
+{
+    Q_ASSERT(m_compEditWidget);
+    if (!m_compEditWidget) {
+        return;
+    }
+    QString filters = QString("%1 (*.key);;%2 (*)").arg(tr("Key files"), tr("All files"));
+    QString fileName = fileDialog()->getOpenFileName(this, tr("Select a key file"), QString(), filters);
+
+    if (QFileInfo(fileName).canonicalFilePath() == m_parent->getDatabase()->canonicalFilePath()) {
+        MessageBox::critical(getMainWindow(),
+                             tr("Invalid Key File"),
+                             tr("You cannot use the current database as its own keyfile. Please choose a different "
+                                "file or generate a new key file."));
+        return;
+    } else if (fileName.endsWith(".kdbx", Qt::CaseInsensitive)) {
+        auto response =
+            MessageBox::warning(getMainWindow(),
+                                tr("Suspicious Key File"),
+                                tr("The chosen key file looks like a password database file. A key file must be a "
+                                   "static file that never changes or you will lose access to your database "
+                                   "forever.\nAre you sure you want to continue with this file?"),
+                                MessageBox::Continue | MessageBox::Cancel,
+                                MessageBox::Cancel);
+        if (response != MessageBox::Continue) {
+            return;
+        }
+    }
+
+    if (!fileName.isEmpty()) {
+        m_compUi->keyFileCombo->setEditText(fileName);
+    }
+}