Integrating Jira Service Desk with an external application

We want to show the jira service desk agent page inside an iframe in our application. The user is already logged into our application. So we don’t want to show the jira login again to access the jira page.

We don’t have any SSO in our organization. And our application is not connected to an LDAP. So don’t want to do it via SSO since it need some change in our existing website.User details are stored in db(IAM).
REST API gives only the data but we have to access the jira pages.
Is there any other methods to integrate such as any ticket (cookie) authentication(by appending a ticket to the url). Or Is there any SDK that provides an authorised ticket to access the jira?