Problems with Cookies (session management with multiple authentication providers)

The web project I work on has an old-school login with username and password, check the hash in the database, and set a cookie design that we would like to improve on to support third party API access and multiple external authentication providers (OpenID-Connect, OATH2, SAML).

First, just setting an auth cookies sucks. Suppose a visitor to a web site has two login accounts A and B. He logs into account A in one tab, then, in another tab, signs out of the first account, and signs into account B. Now if the first tab is running a "single page application" javascript app, and the javascript code assumes that it is either signed into a valid session or signed out, then that code in the first tab can wind up inadvertently issuing updates to account B that were intended for account A. An application should not rely on a cookie to track its session, since that cookie can be changed out from under the app by code running in another tab; the app should instead explicitly pass some X-auth header or some similar trick to explicitly specify which session it intends to communicate in.

Second, the old prompt the visitor for a username and password that are validated against an app-maintained (JAAS style) authentication database sucks. A modern app should support multiple identity providers, so that a visitor can authenticate against an identity provider of her choice to establish a login session. An app has a session management service to manage the authentication handshake with different identity providers. This kind of infrastructure works equally well for both native and web apps.

Anyway - that's my current thinking on the subject of authentication and session management. Design-time ideas like these rarely survive implementation of working code.