The general way to login a https server or https proxy with below steps:
1. Client sends "get request" for the login page
2. Sever response the login page with a cookies/session id.
2. Client sends "post request" with username and password and session id.
3. Server response login successful
4. Client access new page or tear down...
In such a testing, please use traceplus(request from Spirent SE) or use Fillder2(SOL10829) to capture the action details. Copy the action into Avalanche, and enable http 1.1 persistence and user cookies under Avalanche profiles.
Send email to email@example.com for further assitence.