CookieJar::set_cookie and set_cookie_from_js started from the request host but
blindly overwrote it with any Domain attribute, so a response from
attacker.test could plant a cookie scoped to victim.test, which was then sent
on later requests to victim.test. The same sink backs document.cookie, HTTP
Set-Cookie, and CookieStore::set.
Add resolve_cookie_domain: with no Domain the cookie is host-only (exact host
only); a Domain attribute is honored only when it domain-matches the origin
(equal or a parent domain) and is not an obvious public suffix, otherwise the
attribute is ignored and the cookie is stored host-only on the origin. Track
host_only on CookieEntry so host-only cookies are not sent to subdomains.
A full public suffix list is not bundled, so multi-label public suffixes
(co.uk, github.io) are not rejected; the domain-match check still blocks the
reported cross-domain attack, and single-label suffixes (com, local) are.
Tests cover the cross-domain rejection for both HTTP and document.cookie,
public-suffix rejection, host-only subdomain scoping, and that legitimate
parent-domain cookies still work.
Co-authored-by: DavidCarliez <DavidCarliez@users.noreply.github.com>
