refactoring

Resolve #7779

packages/backend/src/misc/secure-rndstr.ts

@@ -0,0 +1,21 @@
+import * as crypto from 'crypto';
+
+const L_CHARS = '0123456789abcdefghijklmnopqrstuvwxyz';
+const LU_CHARS = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
+
+export function secureRndstr(length = 32, useLU = true): string {
+	const chars = useLU ? LU_CHARS : L_CHARS;
+	const chars_len = chars.length;
+
+	let str = '';
+
+	for (let i = 0; i < length; i++) {
+		let rand = Math.floor((crypto.randomBytes(1).readUInt8(0) / 0xFF) * chars_len);
+		if (rand === chars_len) {
+			rand = chars_len - 1;
+		}
+		str += chars.charAt(rand);
+	}
+
+	return str;
+}