Manual:SameSite cookies/de
SameSite is a recent addition to the syntax of HTTP cookies.
If a cookie is marked as SameSite=Lax or SameSite=Strict, the browser will not send it with cross-domain requests.
(The difference between the two is in the interpretation of "cross-domain": for Lax, it only covers "hidden" requests such as AJAX or iframes, while for Strict, top-level user navigation such as clicking on a link going to another domain is also included.) Browsers are planning to default cookies with no SameSite specification to Lax; as of 2020 autumn, Chrome is the only one actually doing it.[1] Sites running over multiple domains that are not prepared for this change might experience various issues, such as authentication failures.
(Sites running on a single domain will not be affected.)
As of 1.34, MediaWiki supports setting the SameSite flag on cookies.
The default for authentication-related cookies is determined by the $wgCookieSameSite setting.
Setting this to None (and enabling $wgForceHTTPS, as use of secure HTTPS cookies is required by browsers for SameSite=None) can fix issues such as MediaWiki seeing the user as not logged in when using cross-domain features.
Setting the flag on non-authentication cookies is the responsibility of the code handling the cookie; this can only be decided individually, and in most cases it is not needed.
Browserkompatibilität
An older version of the standard defined SameSite as a boolean flag; older versions of browsers which implement this interpret SameSite=<anything> as SameSite=Strict.
To work around this, MediaWiki can set a second, fallback cookie which is compatible with old browsers but not new ones.
This behavior is enabled by setting $wgUseSameSiteLegacyCookies to true.
Browserwarnungen
Browsers can show various warnings on cookies which do not have the SameSite flag, e.g. Firefox tends to show errors like this in the developer console: Cookie “<name>” will be soon rejected because it has the “sameSite” attribute set to “none” or an invalid value, without the “secure” attribute. This is a confusing and poorly worded message; what it is supposed to mean is that the cookie will soon be treated as SameSite=Lax and thus not sent with cross-domain AJAX requests.
For most non-authentication cookies this is not a problem and the warning can be ignored.
It might be worth to explicitly set SameSite=Lax to get rid of the warning, though.
SameSite-Cookies in MediaWiki verwenden
In PHP, to set the SameSite flag on a cookie, use WebResponse::setCookie() with $options['sameSite'] = 'lax' or similar.
To take $wgUseSameSiteLegacyCookies compatibility cookie into account when reading cookies, use WebRequest::getCrossSiteCookie() instead of WebRequest::getCookie().
In Javascript, use the sameSite property of the options object passed to $.cookie to set the SameSite flag on a cookie.
Debugging und Fehlerberichte
- https://samesite-sandbox.glitch.me/ can be used to check a browser's standard compliance. With the new default-to-Lax SameSite behavior, it should be all green.
- Set specific SameSite handling behavior for testing:
- Chrome:
same-site-by-default-cookiesandcookies-without-same-site-must-be-secureflags (see also their debugging tutorial) - Firefox:
network.cookie.sameSite.laxByDefaultandnetwork.cookie.sameSite.noneRequiresSecureconfiguration keys
- Chrome:
Siehe auch
- Documentation on MDN
- caniuse browser stats and docs
- The draft standards for SameSite and for defaulting to Lax.
- Handbuch:HTTPS
- Main task for SameSite issues: T255366
