1 files changed, 51 insertions, 0 deletions
diff --git a/lib/classes/Services/ImageValidator.php b/lib/classes/Services/ImageValidator.php
new file mode 100644
index 0000000..c26377c
--- /dev/null
+++ b/lib/classes/Services/ImageValidator.php
@@ -0,0 +1,51 @@
+<?php
+namespace Studip\Services;
+
+final class ImageValidator
+{
+    public const VALID_EXTENSIONS = [
+        'gif',
+        'jpeg', 'jpg',
+        'png',
+        'webp',
+    ];
+
+    public const VALID_MIMETYPES = [
+        'image/gif',
+        'image/jpeg',
+        'image/png',
+        'image/webp',
+    ];
+
+    public function validate(string $filename): bool
+    {
+        return $this->validateName($filename)
+            && $this->validateMimeType(get_mime_type($filename))
+            && $this->validateContents($filename);
+    }
+
+    public function validateMimeType(string $mime_type): bool
+    {
+        return str_starts_with($mime_type, 'image/')
+            && in_array($mime_type, self::VALID_MIMETYPES);
+    }
+
+    public function validateName(string $filename): bool
+    {
+        $extension = pathinfo($filename, PATHINFO_EXTENSION);
+        $extension = strtolower($extension);
+        return in_array($extension, self::VALID_EXTENSIONS);
+    }
+
+    public function validateContents(string $filename): bool
+    {
+        $check = imagecreatefromstring(file_get_contents($filename));
+        if ($check === false) {
+            return false;
+        }
+
+        imagedestroy($check);
+
+        return true;
+    }
+}