diff --git a/Core/API/SsoAPI.class.php b/Core/API/SsoAPI.class.php
index 97f0413..97d8617 100644
--- a/Core/API/SsoAPI.class.php
+++ b/Core/API/SsoAPI.class.php
@@ -3,6 +3,7 @@
 namespace Core\API {
   
   use Core\Objects\Context;
+  use Core\Objects\DatabaseEntity\SsoProvider;
   use Core\Objects\DatabaseEntity\User;
 
   abstract class SsoAPI extends Request {
@@ -10,16 +11,18 @@ namespace Core\API {
       parent::__construct($context, $externalCall, $params);
     }
 
-    protected function processLogin(User $user, ?string $redirectUrl): bool {
+    protected function processLogin(SsoProvider $provider, User $user, ?string $redirectUrl): bool {
       $sql = $this->context->getSQL();
       if ($user->getId() === null) {
         // user didn't exit yet. try to insert into database
         if (!$user->save($sql)) {
           return $this->createError("Could not create user: " . $sql->getLastError());
         }
-      }
-
-      if (!$this->createSession($user)) {
+      } else if (!$user->isActive()) {
+        return $this->createError("This user is currently disabled. Contact the server administrator, if you believe this is a mistake.");
+      } else if ($user->getSsoProvider()?->getIdentifier() !== $provider->getIdentifier()) {
+        return $this->createError("An existing user is not managed by the used identity provider");
+      } else if (!$this->createSession($user)) {
         return false;
       }
 
@@ -221,7 +224,7 @@ namespace Core\API\Sso {
       if (!$parsedResponse->wasSuccessful()) {
         return $this->createError("Error parsing SAMLResponse: " . $parsedResponse->getError());
       } else {
-        return $this->processLogin($parsedResponse->getUser(), $parsedResponse->getRedirectURL());
+        return $this->processLogin($parsedResponse->getProvider(), $parsedResponse->getUser(), $parsedResponse->getRedirectURL());
       }
 
       $sql = $this->context->getSQL();
diff --git a/Core/Objects/DatabaseEntity/User.class.php b/Core/Objects/DatabaseEntity/User.class.php
index c215c70..62296ff 100644
--- a/Core/Objects/DatabaseEntity/User.class.php
+++ b/Core/Objects/DatabaseEntity/User.class.php
@@ -176,4 +176,8 @@ class User extends DatabaseEntity {
   public function isLocalAccount(): bool {
     return $this->ssoProvider === null;
   }
+
+  public function getSsoProvider(): ?SsoProvider {
+    return $this->ssoProvider;
+  }
 }
\ No newline at end of file
diff --git a/Core/Objects/SSO/SAMLResponse.class.php b/Core/Objects/SSO/SAMLResponse.class.php
index d55b64d..590a0fd 100644
--- a/Core/Objects/SSO/SAMLResponse.class.php
+++ b/Core/Objects/SSO/SAMLResponse.class.php
@@ -2,6 +2,7 @@
 
 namespace Core\Objects\SSO;
 
+use Core\Driver\Logger\Logger;
 use Core\Driver\SQL\Condition\Compare;
 use Core\Objects\Context;
 use Core\Objects\DatabaseEntity\SsoProvider;
@@ -16,6 +17,9 @@ class SAMLResponse {
   private ?User $user;
   private ?SsoRequest $request;
 
+  private function __construct() {
+  }
+
   private static function createSuccess(SsoRequest $request, User $user) : SAMLResponse {
     $response = new SAMLResponse();
     $response->user = $user;
@@ -34,6 +38,7 @@ class SAMLResponse {
 
   public static function parseResponse(Context $context, string $response) : SAMLResponse {
     $sql = $context->getSQL();
+    $logger = new Logger("SAML", $sql);
     $xml = new DOMDocument();
     $xml->loadXML($response);
 
@@ -90,6 +95,7 @@ class SAMLResponse {
     $issuer = $xml->getElementsByTagName('Issuer')->item(0)->nodeValue;
     // TODO: validate issuer
 
+    // TODO: create a possibility to map attribute values to user properties
     $username = $xml->getElementsByTagName('NameID')->item(0)->nodeValue;
     $attributes = [];
     foreach ($xml->getElementsByTagName('Attribute') as $attribute) {
@@ -111,7 +117,8 @@ class SAMLResponse {
 
     $fullName = implode(" ", $fullName);
     $user = User::findBy(User::createBuilder($context->getSQL(), true)
-      ->where(new Compare("email", $email), new Compare("name", $username)));
+      ->where(new Compare("email", $email), new Compare("name", $username))
+      ->fetchEntities());
 
     if ($user === false) {
       return self::createError($ssoRequest, "Error fetching user: " . $sql->getLastError());
@@ -146,4 +153,8 @@ class SAMLResponse {
     return $this->request->getRedirectUrl();
   }
 
+  public function getProvider(): SSOProvider {
+    return $this->request->getProvider();
+  }
+
 }
\ No newline at end of file