How do you authenticate a user with the SSO using who is accessing the network through an IPAD?

As an IPAD will not respond either to NetAPI or WMI queries, and does not typically log into a windows domain controller like a windows desktop does, other options need to be used to have an IPAD authenticate the local or LDAP user to the firewall. 

There are a number of workarounds possible to accomplish this:

NTLM authentication via the web browser is one way to allow the device to login to the Domain.  Instructions to configure the firewall side for NTLM Authentication can be found here:
UTM: Single-sign-on (SSO) using NTLM Browser Authentication in SonicOS 5.8. and above

Another is to configure radius authentication for a wireless access point or virtual access point so a user can authenticate to the wireless using their domain credentials. This is discussed here:
Configuring a Virtual Access Point (VAP) Profile

Still another workaround is to have the user on the wireless network VPN to the firewall via a GroupVPN policy or an SSLVPN policy configured on a guest network or some other wireless network that has been modified to allow VPN users to authenticate.  Note that GroupVPN policies would only be useful for L2TP connections on the iPad, which would require configuration of the iPad's internal client that we could not support, so it is recommended instead to use SSLVPN for this via the mobile connect app.  Instructions on configuration of mobile connect are found here:
How to create a connection in SonicWall Mobile Connect (iOS 4.2 and above)

L2TP instructions can be found here if desired instead
Authenticating iPads and iPhones to Windows via L2TP Server and RADIUS.