Stop rejecting cookies which have a domain that matches a TLD

... but only if the host it came from is an EXACT match. Also only apply
the cookie if the url is an EXACT match.

[ChangeLog][QtNetwork][QNetworkCookieJar] Cookies will no longer be
rejected when the domain matches a TLD. However (to avoid problems
with TLDs), such cookies are only accepted, or sent, when the host name
matches exactly.

Task-number: QTBUG-52040
Change-Id: Ic2ebd9211c48891beb669032591234b57713c31d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/network/access/qnetworkcookiejar.cpp

@@ -241,6 +241,17 @@ QList<QNetworkCookie> QNetworkCookieJar::cookiesForUrl(const QUrl &url) const
         if ((*it).isSecure() && !isEncrypted)
             continue;
 
+        QString domain = it->domain();
+        if (domain.startsWith(QLatin1Char('.'))) /// Qt6?: remove when compliant with RFC6265
+            domain = domain.mid(1);
+#if QT_CONFIG(topleveldomain)
+        if (qIsEffectiveTLD(domain) && url.host() != domain)
+            continue;
+#else
+        if (!domain.contains(QLatin1Char('.')) && url.host() != domain)
+            continue;
+#endif // topleveldomain
+
         // insert this cookie into result, sorted by path
         QList<QNetworkCookie>::Iterator insertIt = result.begin();
         while (insertIt != result.end()) {
@@ -340,6 +351,11 @@ bool QNetworkCookieJar::validateCookie(const QNetworkCookie &cookie, const QUrl
     if (domain.startsWith(QLatin1Char('.')))
         domain = domain.mid(1);
 
+    // We shouldn't reject if:
+    // "[...] the domain-attribute is identical to the canonicalized request-host"
+    // https://tools.ietf.org/html/rfc6265#section-5.3 step 5
+    if (host == domain)
+        return true;
 #if QT_CONFIG(topleveldomain)
     // the check for effective TLDs makes the "embedded dot" rule from RFC 2109 section 4.3.2
     // redundant; the "leading dot" rule has been relaxed anyway, see QNetworkCookie::normalize()

tests/auto/network/access/qnetworkcookiejar/tst_qnetworkcookiejar.cpp

@@ -164,7 +164,9 @@ void tst_QNetworkCookieJar::setCookiesFromUrl_data()
     result.clear();
     preset.clear();
     cookie.setDomain(".foo.ck");
-    QTest::newRow("effective-tld2-denied") << preset << cookie << "http://foo.ck" << result << false;
+    result += cookie;
+    QTest::newRow("effective-tld2-accepted2") << preset << cookie << "http://foo.ck" << result << true;
+    result.clear();
     QTest::newRow("effective-tld2-denied2") << preset << cookie << "http://www.foo.ck" << result << false;
     QTest::newRow("effective-tld2-denied3") << preset << cookie << "http://www.anything.foo.ck" << result << false;
     cookie.setDomain(".www.ck");
@@ -208,6 +210,22 @@ void tst_QNetworkCookieJar::setCookiesFromUrl_data()
     preset.clear();
     cookie.setDomain(".com.");
     QTest::newRow("rfc2109-4.3.2-ex3-2") << preset << cookie << "http://x.foo.com" << result << false;
+
+    // When using a TLD as a hostname the hostname should still get cookies (QTBUG-52040)
+    // ... and nothing else should get the cookies.
+    result.clear();
+    preset.clear();
+    cookie.setPath("/");
+    cookie.setDomain(".support");
+    result += cookie;
+    QTest::newRow("TLD-as-domain-accepted") << preset << cookie << "http://support" << result << true;
+    result.clear();
+    QTest::newRow("TLD-as-domain-rejected") << preset << cookie << "http://a.support" << result << false;
+    // Now test with no domain in the cookie, use the domain from the url (matching TLD)
+    cookie.setDomain("support");
+    result += cookie;
+    cookie.setDomain("");
+    QTest::newRow("TLD-as-domain-accepted2") << preset << cookie << "http://support" << result << true;
 }
 
 void tst_QNetworkCookieJar::setCookiesFromUrl()
@@ -351,6 +369,19 @@ void tst_QNetworkCookieJar::cookiesForUrl_data()
     result.clear();
     result += rootCookie;
     QTest::newRow("root-path-match") << allCookies << "http://qt-project.org" << result;
+
+    // Domain in cookie happens to match a TLD
+    allCookies.clear();
+    QNetworkCookie tldCookie;
+    tldCookie.setDomain(".support");
+    tldCookie.setName("a");
+    tldCookie.setValue("b");
+    allCookies += tldCookie;
+    result.clear();
+    result += tldCookie;
+    QTest::newRow("tld-cookie-match") << allCookies << "http://support/" << result;
+    result.clear();
+    QTest::newRow("tld-cookie-no-match") << allCookies << "http://a.support/" << result;
 }
 
 void tst_QNetworkCookieJar::cookiesForUrl()