Redirect loop when URL have uppercase

Author: rogerdz

app/code/Magento/Config/Model/Config/Backend/Baseurl.php

@@ -5,8 +5,8 @@
  */
 namespace Magento\Config\Model\Config\Backend;
 
-use Magento\Framework\Validator\Url as UrlValidator;
 use Magento\Framework\App\ObjectManager;
+use Magento\Framework\Validator\Url as UrlValidator;
 
 /**
  * @api
@@ -56,7 +56,7 @@ public function __construct(
      */
     public function beforeSave()
     {
-        $value = $this->getValue();
+        $value = strtolower($this->getValue());
         try {
             if (!$this->_validateUnsecure($value) && !$this->_validateSecure($value)) {
                 $this->_validateFullyQualifiedUrl($value);
@@ -68,6 +68,7 @@ public function beforeSave()
             $error = new \Magento\Framework\Exception\LocalizedException($msg, $e);
             throw $error;
         }
+        $this->setValue($value);
     }
 
     /**
@@ -232,6 +233,7 @@ public function afterSave()
      * Get URL Validator
      *
      * @deprecated 100.1.12
+     * @see Nothing
      * @return UrlValidator
      */
     private function getUrlValidator()

app/code/Magento/Config/Test/Unit/Model/Config/Backend/BaseurlTest.php

@@ -61,4 +61,30 @@ public function testSaveMergedJsCssMustBeCleaned()
         $model->setValue('http://example.com/')->setPath(Store::XML_PATH_UNSECURE_BASE_URL);
         $model->afterSave();
     }
+
+    /**
+     * @dataProvider beforeSaveDataProvider
+     * @param string|null $value
+     * @param string|bool $expectedValue false if exception to be thrown
+     * @return void
+     */
+    public function testBeforeSaveConvertLowerCase($value, $expectedValue)
+    {
+        $model = (new ObjectManager($this))->getObject(Baseurl::class);
+        $model->setValue($value);
+        $model->beforeSave();
+        $this->assertEquals($expectedValue, $model->getValue());
+    }
+
+    /**
+     * @return array
+     */
+    public function beforeSaveDataProvider()
+    {
+        return [
+            ['https://Example1.com/', 'https://example1.com/'],
+            ['https://EXAMPLE2.COM/', 'https://example2.com/'],
+            ['HTtpS://ExamPLe3.COM/', 'https://example3.com/'],
+        ];
+    }
 }