Werk #11492: Auth cookies: Specify SameSite attribute to improve cookie security

Component	GUI
Title	Auth cookies: Specify SameSite attribute to improve cookie security
Date	Sep 11, 2020
Checkmk Editon	Checkmk Raw (CRE)
Checkmk Version	2.0.0i1
Level	Trivial Change
Class	Security Fix
Compatibility	Compatible - no manual interaction needed

The authentication cookies of the Checkmk GUI (auth_[site]) previously relied on the browsers default behaviour regarding the same site policy. This resulted in a) an inconsistent cookie handling across the different browsers and b) allow some sort of Cross-site request forgery (CSRF) attacks.

With this change we explicitly set the "SameSite=Lax" setting for all authentication cookies created by logins after updating Checkmk.

For more information about this HTTP cookie setting have a look at https://web.dev/samesite-cookies-explained/.

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