domainMatch() breaks for URLs with TLD in substring of subdomain

[davidofwatkins]

There's a bug where domainMatch() returns false unexpectedly when the domStr argument (top-level-domain) can be found elsewhere in the domain (str argument). For example:

❌ Broken:

require('tough-cookie').domainMatch('computer.com', 'com'); // false - should be true

✅ Working:

require('tough-cookie').domainMatch('c0mputer.com', 'com'); // true

The issue appears to come from the indexOf() check here:

tough-cookie/lib/cookie.js

Line 371 in 30246e6

const idx = str.indexOf(domStr);

...causing this calculation to fail:

tough-cookie/lib/cookie.js

Lines 379 to 381 in 30246e6

	if (str.length !== domStr.length + idx) {
	return false; // it's not a suffix
	}

[colincasey]

Thanks for the bug report @davidofwatkins. I'll look into this as soon as possible. But don't let that deter you from submitting your own PR with a fix if you have one.