ServiceNow connection with Ansible Tower Via HTTPS

 https://www.ansible.com/blog/ansible-servicenow-howto-part-3-making-outbound-restful-api-calls-to-ansible-tower

The key step is 

Preparing ServiceNow

4) Moving over to ServiceNow, Navigate to System Definition->Certificates. This will take you to a screen of all the certificates Service Now uses. Click on the blue New button, and fill in these details:

• Name: Descriptive name of the certificate
• Format: PEM
• Type: Trust Store Cert
• PEM Certificate: The certificate to authenticate against Ansible Tower with. You can use the built-in certificate on your Tower server, located at /etc/tower/tower.cert. Copy the contents of this file into the field in ServiceNow.

Click the Submit button at the bottom.

The reason for this step is :

For outboud HTTPS calls , ServiceNow requires two steps:

1) Upload server's SSL certificate to ensure it is trusted

https://docs.servicenow.com/bundle/paris-platform-administration/page/administer/general/task/t_UploadATrustedServerCertificate.htm

Paris

By uploading the service provider's trusted server certificate, the instance ensures it is connecting to a valid and secure service.

Before you begin

Role required: admin

About this task

The instance validates outbound Web Service calls by using the certificate provided by the service provider.

Procedure

1. Create a new Certificate record with the type "Trust Store Cert".
2. Do one of the following actions:
   • Attach the service provider's DER formatted certificate.
   • Copy and paste the service provider's PEM format certificate into the PEM Certificate field.

2) It then uses OPEN SSL to validate