CVE-2023-29020

Date: April 21, 2023

@fastify/passport is a port of passport authentication library for the Fastify ecosystem. The CSRF (Cross-Site Request Forger) protection enforced by the "@fastify/csrf-protection" library, when combined with "@fastify/passport" in affected versions, can be bypassed by network and same-site attackers. "fastify/csrf-protection" implements the synchronizer token pattern (using plugins "@fastify/session" and "@fastify/secure-session") by storing a random value used for CSRF token generation in the "_csrf" attribute of a user's session. The "@fastify/passport" library does not clear the session object upon authentication, preserving the "_csrf" attribute between pre-login and authenticated sessions. Consequently, CSRF tokens generated before authentication are still valid. Network and same-site attackers can thus obtain a CSRF token for their pre-session, fixate that pre-session in the victim's browser via cookie tossing, and then perform a CSRF attack after the victim authenticates. As a solution, newer versions of "@fastify/passport" include the configuration options: "clearSessionOnLogin (default: true)" and "clearSessionIgnoreFields (default: ['passport', 'session'])" to clear all the session attributes by default, preserving those explicitly defined in "clearSessionIgnoreFields".

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