Salesforce has the ability to function as an identity provider for Aha! using SAML 2.0. It is a popular option among customers that have an active customer community being run through Salesforce already and is commonly used to allow the Salesforce community users to authenticate into an Aha! ideas portal through single sign-on. Salesforce could also function as the identity provider to allow all users to authenticate into the actual Aha! application, although that is a much less common workflow.
The first step is to set up Salesforce to function as an identity provider. This is done within Salesforce: https://help.salesforce.com/articleView?id=identity_provider_enable.htm&language=en&type=0
With Salesforce set up as an identity provider, you can then go into Aha! and enable SSO for your idea portal (or account). The idea portal SSO is located under Settings > Account > Configure idea portals.
Salesforce will function as a SAML based identity provider, so select SAML from the dropdown menu. As a SAML provider, there are various configuration customizations that can be passed to Aha! These are outlined here: Single sign-on: SAML 2.0
Note: When configuring SSO with Salesforce, the Single sign-on endpoint field in Aha! needs to be populated with the "SP-Initiated Redirect Endpoint" URL from the "SAML Login Information" settings in Salesforce. The default endpoint provided by Salesforce utilizes a HTTP POST as opposed to a HTTP GET that is expected when running SSO.