where is Ruby looking for SSL_CERT_FILE?

I experienced the same problem under Ubuntu. There seems no longer to be a compiled in default (if it ever had, in theory it could also have been the distributors' work).

I opted to set the path in apache config (my rails app is controlled by passenger).

SetEnv SSL_CERT_DIR /usr/share/ca-certificates/mozilla

It now works.

There is also an SSL_CERT_FILE for a single certificate.

You have to adjust the paths.

Just check the main pages, and this page. Even line 4 over here says so: https://github.com/google/signet/blob/master/lib/signet/ssl_config.rb

I could also have set the path system-wide in /etc/environment and restarted the system.