fix: Extend SVG reference check

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/Preview/SVG.php

@@ -53,7 +53,7 @@ public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
 			}
 
 			// Do not parse SVG files with references
-			if (stripos($content, 'xlink:href') !== false) {
+			if (preg_match('/["\s](xlink:)?href\s*=/i', $content)) {
 				return null;
 			}
 

tests/lib/Preview/SVGTest.php

@@ -43,4 +43,33 @@ protected function setUp(): void {
 			$this->markTestSkipped('No SVG provider present');
 		}
 	}
+
+	public function dataGetThumbnailSVGHref(): array {
+		return [
+			['href'],
+			[' href'],
+			["\nhref"],
+			['xlink:href'],
+			[' xlink:href'],
+			["\nxlink:href"],
+		];
+	}
+
+	/**
+	 * @dataProvider dataGetThumbnailSVGHref
+	 * @requires extension imagick
+	 */
+	public function testGetThumbnailSVGHref(string $content): void {
+		$handle = fopen('php://temp', 'w+');
+		fwrite($handle, '<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
+  <image x="0" y="0"' . $content . '="fxlogo.png" height="100" width="100" />
+</svg>');
+		rewind($handle);
+
+		$file = $this->createMock(\OCP\Files\File::class);
+		$file->method('fopen')
+			->willReturn($handle);
+
+		self::assertNull($this->provider->getThumbnail($file, 512, 512));
+	}
 }