Added first version of the validate functions, now to test them

Signed-off-by: Slava Bezgachev <bezgachev@gmail.com>

src/validate.js

@@ -1,10 +1,45 @@
+/* Pi-hole: A black hole for Internet advertisements
+*  (c) 2017 Pi-hole, LLC (https://pi-hole.net)
+*  Network-wide ad blocking via your own hardware.
+*
+*  Web Interface
+*  Various utilities including the API
+*
+*  This file is copyright under the latest version of the EUPL.
+*  Please see LICENSE file for your rights under this license. */
+
 export const validate = {
   domain(domain) {
-    try {
-      if (domain.length < 3) return false;
-      return !!domain.match(/([a-zA-Z0-9]+(-[a-zA-Z0-9]+)*)+(\.([a-zA-Z0-9]+(-[a-zA-Z0-9]+)*))*$/);
-    } catch (err) {
-      return false;
-    }
+    // Make sure it's a fully qualified domain
+    const split = domain.split(".");
+    // Has to have at least 2 segments, of at least 1 character each
+    if (split.length < 2) return false;
+    split.forEach(segment => {
+      if (segment.length < 1) return false;
+    });
+    return validate.hostname(domain);
+  },
+  hostname(hostname) {
+    // Must not exceed 253 characters total
+    if (hostname.length > 253) return false;
+    // Each segment must not exceed 63 characters
+    const segments = hostname.split(".");
+    segments.forEach(segment => {
+      // Also check it's not empty
+      if (!segment || segment.length > 63) return false;
+    });
+    // Must not be all numbers and periods
+    const joined = segments.join("");
+    // If the hostname without periods make a number, deny
+    if (!validate.isStrictNumeric(joined)) return false;
+
+    return /([a-zA-Z0-9]+(-[a-zA-Z0-9]+)*)+(\.([a-zA-Z0-9]+(-[a-zA-Z0-9]+)*))*$/.test(
+      hostname
+    );
+  },
+  isStrictNumeric(input) {
+    // Because parseInt has limitations, e.g. parseInt("15ex") is parsed to 15
+    // Caution, does not work with negative numbers, replace with /^(\-|\+)?([0-9])$/ if needed
+    return /^([0-9])$/.test(input);
   }
 };