4.0 and Back Again

Perhaps many of you have made the same mistake I have: upgrading to iPhone OS 4.0 thinking there will be a jailbreak soon, then realizing it won’t happen until summer. And to make things worse, it’s buggy.

Well, I got myself into this mess, I got myself out. I’ll explain how and hope it’ll help some people out there. This information does NOT apply to the iPod Touch (as it doesn’t have a baseband) or the iPhone 3GS with the new boot ROM (since 3.1.3 can’t be jailbroken on it, and the combination of a jailbreak and 3.1.3 are required for this guide).

First off, here’s what you need:

1. An iPhone that isn’t a 3GS with the new bootrom (I did this on my 3GS with the old bootrom)

2. An iPhone OS 3.1.2 IPSW

3. An iPhone OS 3.1.3 IPSW

4. blackra1n

5. A Mac (sorry; see the next requirement, it’s Mac-only; ah well, it’s always fun to rub the occasional Mac-only application in the face of Windows users )

6. Pwnage Tool

7. [3GS only] SHSH’s on file on Saurik’s server

I know there’s other guides for downgrading from 4.0 out there, but they all involve iRecovery, which as far as I know isn’t supposed to work on the 3GS. Maybe someone can correct me on this. Either way, if you happen to have all the prerequisites I’ve listed, this should work for you.

Sorry I don’t have screenshots, but this obviously isn’t something that’s easy to do at will. This was something I had to do once and hopefully never again.

Now, let’s get started, shall we?

1. Make sure you have the entry for Saurik’s SHSH server in your hosts file.

74.208.10.249     gs.apple.com

2. Open iTunes, connect your iPhone, and Control-click on Restore. Then, select your 3.1.2 IPSW to restore to it. Let it restore. It’ll quit with an error in the middle of “Restoring iPhone firmware.”

Why?

It quits with an error while attempting to restore the baseband. It won’t let you replace the 4.0 beta’s 05.13.03 baseband with 3.1.2’s (or 3.1.3’s for that matter, which is why we’re going the indirect route).

3. Your iPhone will now be in recovery mode, demanding you connect it to iTunes. But, it’s actually running a fully-functional 3.1.2. Let’s get it to work now. Run blackra1n on it. Once it finishes, you’ll be greeted by a functional 3.1.2, but it can’t communicate with the new baseband so it can’t function on a cellular network. Time to fix that.

4. Run Pwnage Tool, using your 3.1.3 IPSW. Select your iPhone model, and when it asks that it’s already pwned select yes. In theory, you could just put it in DFU mode while you were still in 4.0 and answered no to this, but I didn’t get to test that method, so I can’t say if it works in practice or not. Assuming you have a regular AT&T contract, answer yes to that as well (or whatever the supported carriers in other countries are if that applies to you). Now, build the firmware and wait for it to finish.

Why Pwnage Tool here?

Pwnage Tool, especially the newest release, rebuilds the firmware and removes the baseband update, since it’s assumed by default that baseband updates are bad for people who want to use Pwnage Tool. Meaning it will restore without an error this time since it won’t try to overwrite the baseband. And yes, we’re almost done.

5. Place your iPhone in recovery mode.

Not sure how?

6. Open iTunes, and restore to your new custom firmware.

7. You should now have a jailbroken 3.1.3 that can communicate with the 4.0 beta’s baseband that you’ll unfortunately never be able to downgrade from.

8. Restore from your latest backup to get all your precious settings, contacts, and messages back.

Having trouble?

If you’re like me, you’ll encounter the misfortune of getting an error that says something about “the backup operation failed.” I have no idea what causes this, but disconnect your iPhone and reconnect it. Somewhere in all this, it should have re-activated your iPhone. Now, right-click your iPhone in iTunes and select “Restore from backup.” Now restore. It should work this time.

I hope this helps some of you who were in the same boat as I was.

Two announcements.

1. A picture is worth a thousand words.

Needless to say, this opens numerous review and tutorial opportunities.

2. Speaking of pictures, my school’s prom was Saturday. I should have a picture from it to post here soon.

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