Before Go 1.20, the RSA based TLS key exchanges used the math/big library, which is not constant time. RSA blinding was applied to prevent timing attacks, but analysis shows this may not have been fully effective. In particular it appears as if the removal of PKCS#1 padding may leak timing information, which in turn could be used to recover session key bits. In Go 1.20, the crypto/tls library switched to a fully constant time RSA implementation, which we do not believe exhibits any timing side channels.
Antes de Go 1.20, los intercambios de claves TLS basados en RSA utilizaban la librería math/big, que no es un tiempo constante. Se aplicó blinding RSA para prevenir ataques sincronizados, pero el análisis muestra que esto puede no haber sido completamente efectivo. En particular, parece que la eliminación del relleno PKCS#1 puede filtrar información de tiempo, que a su vez podría usarse para recuperar bits de clave de sesión. En Go 1.20, la librería crypto/tls cambió a una implementación RSA de tiempo completamente constante, que no creemos que muestre ningún canal lateral de temporización.
A flaw was found in the Golang crypto/tls standard library. In previous versions, the package was vulnerable to a Timing Side Channel attack by observing the time it took for RSA-based TLS key exchanges, which was not constant. This flaw allows a malicious user to gather information from the environment.
