Never try to login as the user SDDM

src/auth/Auth.cpp

@@ -64,6 +64,7 @@ namespace SDDM {
         QString sessionPath { };
         QString user { };
         bool autologin { false };
+        bool greeter { false };
         QProcessEnvironment environment { };
         qint64 id { 0 };
         static qint64 lastId;
@@ -237,6 +238,11 @@ namespace SDDM {
         return d->autologin;
     }
 
+    bool Auth::isGreeter() const
+    {
+        return d->greeter;
+    }
+
     const QString &Auth::session() const {
         return d->sessionPath;
     }
@@ -275,6 +281,14 @@ namespace SDDM {
         }
     }
 
+    void Auth::setGreeter(bool on)
+    {
+        if (on != d->greeter) {
+            d->greeter = on;
+            Q_EMIT greeterChanged();
+        }
+    }
+
     void Auth::setSession(const QString& path) {
         if (path != d->sessionPath) {
             d->sessionPath = path;
@@ -302,6 +316,8 @@ namespace SDDM {
             args << "--user" << d->user;
         if (d->autologin)
             args << "--autologin";
+        if (d->greeter)
+            args << "--greeter";
         d->child->start(QString("%1/sddm-helper").arg(LIBEXEC_INSTALL_DIR), args);
     }
 }

src/auth/Auth.h

@@ -52,6 +52,7 @@ namespace SDDM {
         Q_OBJECT
         // not setting NOTIFY for the properties - they should be set only once before calling start
         Q_PROPERTY(bool autologin READ autologin WRITE setAutologin NOTIFY autologinChanged)
+        Q_PROPERTY(bool greeter READ isGreeter WRITE setGreeter NOTIFY greeterChanged)
         Q_PROPERTY(bool verbose READ verbose WRITE setVerbose NOTIFY verboseChanged)
         Q_PROPERTY(QString user READ user WRITE setUser NOTIFY userChanged)
         Q_PROPERTY(QString session READ session WRITE setSession NOTIFY sessionChanged)
@@ -86,6 +87,7 @@ namespace SDDM {
         static void registerTypes();
 
         bool autologin() const;
+        bool isGreeter() const;
         bool verbose() const;
         const QString &user() const;
         const QString &session() const;
@@ -113,6 +115,12 @@ namespace SDDM {
         */
         void setAutologin(bool on = true);
 
+        /**
+         * Set mode to greeter
+         * This will bypass authentication checks
+         */
+        void setGreeter(bool on = true);
+
         /**
         * Forwards the output of the underlying authenticator to the current process
         * @param on true if should forward the output
@@ -139,6 +147,7 @@ namespace SDDM {
 
     Q_SIGNALS:
         void autologinChanged();
+        void greeterChanged();
         void verboseChanged();
         void userChanged();
         void sessionChanged();

src/daemon/Display.cpp

@@ -184,6 +184,13 @@ namespace SDDM {
 
     void Display::login(QLocalSocket *socket, const QString &user, const QString &password, const QString &session) {
         m_socket = socket;
+
+        //the SDDM user has special priveledges that skip password checking so that we can load the greeter
+        //block ever trying to log in as the SDDM user
+        if (user == "sddm") {
+            return;
+        }
+
         startAuth(user, password, session);
     }
 

src/daemon/Greeter.cpp

@@ -140,6 +140,7 @@ namespace SDDM {
 
             // start greeter
             m_auth->setUser("sddm");
+            m_auth->setGreeter(true);
             m_auth->setSession(args.join(" "));
             m_auth->start();
         }

src/helper/Backend.cpp

@@ -48,6 +48,10 @@ namespace SDDM {
         m_autologin = on;
     }
 
+    void Backend::setGreeter(bool on) {
+        m_greeter = on;
+    }
+
     bool Backend::openSession() {
         struct passwd *pw;
         pw = getpwnam(qPrintable(qobject_cast<HelperApp*>(parent())->user()));

src/helper/Backend.h

@@ -36,6 +36,7 @@ namespace SDDM {
         static Backend *get(HelperApp *parent);
 
         void setAutologin(bool on = true);
+        void setGreeter(bool on = true);
 
     public slots:
         virtual bool start(const QString &user = QString()) = 0;
@@ -48,6 +49,7 @@ namespace SDDM {
         Backend(HelperApp *parent);
         HelperApp *m_app;
         bool m_autologin { false };
+        bool m_greeter { false };
     };
 }
 

src/helper/HelperApp.cpp

@@ -90,6 +90,10 @@ namespace SDDM {
             m_backend->setAutologin(true);
         }
 
+        if ((pos == args.indexOf("--greeter")) >= 0) {
+            m_backend->setGreeter(true);
+        }
+
         if (server.isEmpty() || m_id <= 0) {
             qCritical() << "This application is not supposed to be executed manually";
             exit(Auth::HELPER_OTHER_ERROR);

src/helper/backend/PamBackend.cpp

@@ -217,7 +217,7 @@ namespace SDDM {
 
         QString service = "sddm";
 
-        if (user == "sddm")
+        if (m_greeter)
             service = "sddm-greeter";
         else if (m_app->session()->path().isEmpty())
             service = "sddm-check";