1 files changed, 12 insertions, 1 deletions
diff --git a/libraries/classes/Plugins/Auth/AuthenticationCookie.php b/libraries/classes/Plugins/Auth/AuthenticationCookie.php
index b4a0b0bfde..c468223232 100644
--- a/libraries/classes/Plugins/Auth/AuthenticationCookie.php
+++ b/libraries/classes/Plugins/Auth/AuthenticationCookie.php
@@ -592,11 +592,21 @@ class AuthenticationCookie extends AuthenticationPlugin
      */
     private function getEncryptionSecret(): string
     {
+        /** @var mixed $key */
         $key = $GLOBALS['cfg']['blowfish_secret'] ?? null;
-        if (is_string($key) && mb_strlen($key, '8bit') === SODIUM_CRYPTO_SECRETBOX_KEYBYTES) {
+        if (! is_string($key)) {
+            return $this->getSessionEncryptionSecret();
+        }
+
+        $length = mb_strlen($key, '8bit');
+        if ($length === SODIUM_CRYPTO_SECRETBOX_KEYBYTES) {
             return $key;
         }
 
+        if ($length > SODIUM_CRYPTO_SECRETBOX_KEYBYTES) {
+            return mb_substr($key, 0, SODIUM_CRYPTO_SECRETBOX_KEYBYTES, '8bit');
+        }
+
         return $this->getSessionEncryptionSecret();
     }
 
@@ -605,6 +615,7 @@ class AuthenticationCookie extends AuthenticationPlugin
      */
     private function getSessionEncryptionSecret(): string
     {
+        /** @var mixed $key */
         $key = $_SESSION['encryption_key'] ?? null;
         if (is_string($key) && mb_strlen($key, '8bit') === SODIUM_CRYPTO_SECRETBOX_KEYBYTES) {
             return $key;