In AWS's direct postgres offering RDS Postgres, you can require SSL by setting the parameter group item
rds.force_ssl to 1.
This is as per the RDS postgres documentation: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_PostgreSQL.html#PostgreSQL.Concepts.General.SSL
However Aurora Postgres does not have this parameter item, and there is no ability to add new parameters either. How do you turn on require ssl for an Aurora instance?
I can see in the Aurora version that it supports SSL:
create extension sslinfo; select ssl_is_used(); select ssl_cipher();
And I can optionally connect via ssl:
psql -h my-ssl-test1.cwzhlddlylx.us-east-1.rds.amazonaws.com -p 5432 -U myuser -d mydb sslrootcert=rds-ca-2015-root.pem sslmode=verify-full