Cookies
Published by powerfulyang on Apr 8, 2022
Cookie
Cookie 是由 Set-Cookie: NAME=VALUE; Expires=DATE; Path=PATH; Domain=DOMAIN_NAME;SECURE 组成
SameSite
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The SameSite
attribute of the Set-Cookie
HTTP response header allows you to declare if your cookie should be restricted to a first-party or same-site context.
Note: Standards related to the Cookie SameSite
attribute recently changed such that:
- The cookie-sending behavior if
SameSite
is not specified isSameSite=Lax
. Previously the default was that cookies were sent for all requests. - Cookies with
SameSite=None
must now also specify theSecure
attribute (they require a secure context/HTTPS). - Cookies from the same domain are no longer considered to be from the same site if sent using a different scheme (
http:
orhttps:
).
The SameSite
attribute accepts three values:
Cookies are not sent on normal cross-site subrequests (for example to load images or frames into a third party site), but are sent when a user is navigating to the origin site (i.e., when following a link).
This is the default cookie value if SameSite
has not been explicitly specified in recent browser versions (see the "SameSite: Defaults to Lax" feature in the Browser Compatibility).
Note: Lax
replaced None
as the default value in order to ensure that users have reasonably robust defense against some classes of cross-site request forgery (CSRF) attacks.
Cookies will only be sent in a first-party context and not be sent along with requests initiated by third party websites.
Cookies will be sent in all contexts, i.e. in responses to both first-party and cross-origin requests. If SameSite=None
is set, the cookie Secure
attribute must also be set (or the cookie will be blocked).
Warnings like the ones below might appear in your console:
Cookie "myCookie" rejected because it has the "SameSite=None" attribute but is missing the "secure" attribute.
This Set-Cookie was blocked because it had the "SameSite=None" attribute but did not have the "Secure" attribute, which is required in order to use "SameSite=None".
The warning appears because any cookie that requests SameSite=None
but is not marked Secure
will be rejected.
Set-Cookie: flavor=choco; SameSite=None
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To fix this, you will have to add the Secure
attribute to your SameSite=None
cookies.
Set-Cookie: flavor=choco; SameSite=None; Secure
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A Secure
cookie is only sent to the server with an encrypted request over the HTTPS protocol. Note that insecure sites (http:
) can't set cookies with the Secure
directive.
Note: On older browser versions you might get a warning that the cookie will be blocked in future. For example:
Cookie myCookie
will be soon rejected because it has the SameSite
attribute set to None
or an invalid value, without the secure
attribute.
Recent versions of modern browsers provide a more secure default for SameSite
to your cookies and so the following message might appear in your console:
Cookie "myCookie" has "SameSite" policy set to "Lax" because it is missing a "SameSite" attribute, and "SameSite=Lax" is the default value for this attribute.
The warning appears because the SameSite
policy for a cookie was not explicitly specified:
Set-Cookie: flavor=choco
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You should explicitly communicate the intended SameSite
policy for your cookie (rather than relying on browsers to apply SameSite=Lax
automatically). This will also improve the experience across browsers as not all of them default to Lax
yet.
Set-Cookie: flavor=choco; SameSite=Lax