A friend of mine came to me yesterday with his 3G and said that he was sick of ATT and wants to move to T-Mobile. His iphone was updated to 4.2.1 through the legitimate iPhone/Itunes route.

We have no SHSH on file for this phone and his update to 4.2.1 updated the baseband to the most recent.

What are my options here:

1: I think I can have him revert to an earlier iOS since I really don't need the SHSH to do this. There are other posts on how to do this here, so I can get him back to iOS 4.1 with a custom FW bundle using Pwnage

2: I don't think that we can go back on the baseband though, which means that unlock may be out of reach. however, I think we can install the iPad baseband and use the old exploit to unlock. I understand the risks of doing this but if I build him the custom firmware bundle for "restoring" his phone, and give it to him and he understands that he cannot update to any future version without asking me first will he be OK?

other options?

Originally Posted by unclemiltie

We have no SHSH on file for this phone and his update to 4.2.1 updated the baseband to the most recent.

What are my options here:

1: I think I can have him revert to an earlier iOS since I really don't need the SHSH to do this. There are other posts on how to do this here, so I can get him back to iOS 4.1 with a custom FW bundle using Pwnage

probably will be okay, looks like the 3G bundle in pwnagetool 4.1.2 uses the old pwnage2 exploit and pwns the whole boot-chain. I haven't tested how iTunes handles the soft-shsh requirement in this situation - so I cannot guarantee this will work. (and this is definitely NOT true for the 3GS)

Originally Posted by unclemiltie

˙2: I don't think that we can go back on the baseband though, which means that unlock may be out of reach. however, I think we can install the iPad baseband and use the old exploit to unlock. I understand the risks of doing this but if I build him the custom firmware bundle for "restoring" his phone, and give it to him and he understands that he cannot update to any future version without asking me first will he be OK?

My suggestion, test restoring to a pwnagetool 4.1 custom IPSW before you take the drastic step of updating the baseband to 6.15 - also, I'd start by redsn0w jailbreaking the device on 4.2.1 and then try to restore the custom 4.1 IPSW.