Using Self-Signed SSL Certificates
By default, all machines in a CircleCI Enterprise installation verify SSL
certs for the GitHub Enterprise instance. If you’re using a self-signed cert,
or using a custom CA root, you can select the
“HTTPS (with self-signed certificate)” option in the System Console at port 8800.
You also need to export
CIRCLE_IGNORE_CERT_HOST=insecure-ghe.example.com on builder machines
insecure-ghe.example.com below with the host of your GitHub Enterprise instance).
See this doc for details on setting builder machine environment variables.