[libcalamares] Introduce redaction-of-names class for logging

- redacted names are stable inside of one run of Calamares
- random, private displays of a given string for a context

SEE #1593

src/libcalamares/utils/Logger.cpp

@@ -20,6 +20,8 @@
 #include <QDir>
 #include <QFileInfo>
 #include <QMutex>
+#include <QRandomGenerator>
+#include <QTextStream>
 #include <QTime>
 #include <QVariant>
 
@@ -252,4 +254,34 @@ operator<<( QDebug& s, const RedactedCommand& l )
     return s;
 }
 
+/** @brief Returns a stable-but-private hash of @p context and @p s
+ *
+ * Identical strings with the same context will be hashed the same,
+ * so that they can be logged and still recognized as the-same.
+ */
+static uint insertRedactedName( const QString& context, const QString& s )
+{
+    static uint salt = QRandomGenerator::global()->generate();  // Just once
+
+    uint val = qHash(context, salt);
+    return qHash(s, val);
+}
+
+RedactedName::RedactedName( const QString& context, const QString& s )
+    : m_id( insertRedactedName(context, s) ),
+      m_context(context)
+{
+}
+
+RedactedName::RedactedName(const char *context, const QString& s )
+    : RedactedName( QString::fromLatin1(context), s )
+{
+}
+
+QDebug&
+operator<< ( QDebug& s, const RedactedName& n )
+{
+    return s << NoQuote << n.m_context << '$' << n.m_id << Quote;
+}
+
 }  // namespace Logger

src/libcalamares/utils/Logger.h

@@ -226,6 +226,23 @@ struct RedactedCommand
 
 QDebug& operator<<( QDebug& s, const RedactedCommand& l );
 
+/** @brief When logging "private" identifiers, keep them consistent but private
+ *
+ * Send a string to a logger in such a way that each time it is logged,
+ * it logs the same way, but without revealing the actual contents.
+ * This can be applied to user names, UUIDs, etc.
+ */
+struct RedactedName
+{
+    RedactedName( const char* context, const QString& s );
+    RedactedName( const QString& context, const QString& s );
+
+    const uint m_id;
+    const QString m_context;
+};
+
+QDebug& operator<<( QDebug& s, const RedactedName& n );
+
 /**
  * @brief Formatted logging of a pointer
  *