HTTPS SSH
setup:

install http://pear.php.net/package/Services_Atlassian_Crowd

Configure your parameters. You will need crowd_wsdl, crowd_application_user, and crowd_application_password. I added them to my parameters.ini. The crowd_wsdl will look something like "https://crowd.example.com/crowd/services/SecurityServer?wsdl".

Configure your firewall.
security:
    providers:
        crowd: ~
        # All of a user's Crowd groups will become ROLE_${group_name} with spaces and dashes converted to underscores.
        # crowd-administorators becomes ROLE_CROWD_ADMINISTRATORS
    firewalls:
        secured_area:
            crowd_sso: true
            crowd: true
            logout:
                delete_cookies:
                    crowd.token_key: { path: /, domain: example.com }

With the above configuration if crowd and your symfony site are both hosted at subdomains under example.com, logging into either one will log you into the other.