allow login using hashed passwords (#4464)

* Support getting a user's password salt via initial websocket connection (added to Event_ServerIdentification)

* Nonsense stuff to figure out later

* move passwordhasher to correct location

* protobuf changes

* add ext to protobuf

* implement request password salt server side

* add supportspasswordhash to server identification

* check backwards compatibility

* reset some changes to master

* implement get password salt client side

* implement checking hashed passwords on server login

* check for registration requirement on getting password salt

* properly check password salt response and show errors

* remove unused property

* add password salt to list of response types

Co-authored-by: ZeldaZach <zahalpern+github@gmail.com>

common/passwordhasher.cpp

@@ -0,0 +1,44 @@
+#include "passwordhasher.h"
+
+#include "rng_sfmt.h"
+
+#include <QCryptographicHash>
+
+void PasswordHasher::initialize()
+{
+    // dummy
+}
+
+QString PasswordHasher::computeHash(const QString &password, const QString &salt)
+{
+    QCryptographicHash::Algorithm algo = QCryptographicHash::Sha512;
+    const int rounds = 1000;
+
+    QByteArray hash = (salt + password).toUtf8();
+    for (int i = 0; i < rounds; ++i) {
+        hash = QCryptographicHash::hash(hash, algo);
+    }
+    QString hashedPass = salt + QString(hash.toBase64());
+    return hashedPass;
+}
+
+QString PasswordHasher::generateRandomSalt(const int len)
+{
+    static const char alphanum[] = "0123456789"
+                                   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                                   "abcdefghijklmnopqrstuvwxyz";
+
+    QString ret;
+    int size = sizeof(alphanum) - 1;
+
+    for (int i = 0; i < len; ++i) {
+        ret.append(alphanum[rng->rand(0, size)]);
+    }
+
+    return ret;
+}
+
+QString PasswordHasher::generateActivationToken()
+{
+    return QCryptographicHash::hash(generateRandomSalt().toUtf8(), QCryptographicHash::Md5).toBase64().left(16);
+}