Security fixes

Co-Authored-By: dakkar <dakkar@thenautilus.net>

packages/frontend-shared/js/math.ts

@@ -0,0 +1,10 @@
+/*
+ * SPDX-FileCopyrightText: dakkar and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export function clamp(value: number, min: number, max: number) {
+	if (value > max) return max;
+	if (value < min) return min;
+	return value;
+}

packages/frontend-shared/js/url.ts

@@ -26,3 +26,20 @@ export function extractDomain(url: string) {
 	const match = url.match(/^(?:https?:)?(?:\/\/)?(?:[^@\n]+@)?([^:\/\n]+)/im);
 	return match ? match[1] : null;
 }
+
+export function maybeMakeRelative(urlStr: string, baseStr: string): string {
+	try {
+		const baseObj = new URL(baseStr);
+		const urlObj = new URL(urlStr);
+		/* in all places where maybeMakeRelative is used, baseStr is the
+		 * instance's public URL, which can't have path components, so the
+		 * relative URL will always have the whole path from the urlStr
+		*/
+		if (urlObj.origin === baseObj.origin) {
+			return urlObj.pathname + urlObj.search + urlObj.hash;
+		}
+		return urlStr;
+	} catch (e) {
+		return '';
+	}
+}