Updating iPhone firmware using OTA zip files

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Updating iPhone firmware using OTA zip files

Postby ITguy » Wed Sep 28, 2016 9:54 am

Hello everyone, I'm an iOS newbie so forgive me if this question comes out sounding dumber than I think it is.

I own an iPhone 5c currently running iOS 8.4.1. I decided to upgrade the firmware to freshen things up a little bit, but I'd like to update it to the last jailbreakable firmware version for my device, which happens to be 9.0.2. However, from my research so far (and after many fruitless attempts) I found out that I can't use the iPSW file for an unsigned version to update with iTunes. I can either update through OTA to the latest stable version or using an iPSW file to a version still signed by Apple.

I just recently discovered that I can get OTA zip files online and download them to my computer. This is where I had this crazy idea: if I know where the OTA update process places the file it uses to perform the update, can I download the OTA zip files, each version incrementally, one after the other, copy to the device and install manually until I get to version 9.0.2?

TL;DR Is there a means of copying OTA zip files for older iOS versions from my computer to my iphone and manually install to update the firmware?
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Re: Updating iPhone firmware using OTA zip files

Postby NJJN » Wed Sep 28, 2016 1:29 pm

Hi,

Stick to 8.4.1 JB for the time being & learn your things for 32bit iOS.
Latest is 64bit world but iPhone 5c is 32bit only.
Just my 2 cent.

Regards, NJJN
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Re: Updating iPhone firmware using OTA zip files

Postby ITguy » Wed Sep 28, 2016 2:28 pm

NJJN wrote:Hi,

Stick to 8.4.1 JB for the time being & learn your things for 32bit iOS.
Latest is 64bit world but iPhone 5c is 32bit only.
Just my 2 cent.

Regards, NJJN


Well, thanks for the advice. There are 32bit releases for 9.0.2 as well though. Even iOS 10 has releases for 32bit devices.
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Re: Updating iPhone firmware using OTA zip files

Postby Siguza » Wed Sep 28, 2016 4:03 pm

ITguy wrote:TL;DR Is there a means of copying OTA zip files for older iOS versions from my computer to my iphone and manually install to update the firmware?

No, not like that.
The reason is the same as why you can't update to an older version with iTunes: APTicket.
The APTicket is not only checked on restore, but also saved on your device and checked on every boot. If you can't get a valid APTicket for the versions of iLLB, iBoot and the kernel you're using, your device isn't gonna boot.
You should theoretically be able to replace everything but the bootloaders and the kernelcache, but then you'd be running iOS 9 with an iOS 8 kernel, which seems like the perfect recipe for a disaster to me.

What you might be able to do, however (with an actual chance of success), since you're still on 8 and thus pre-KPP, is a dual-boot.
The concept would basically be:
Boot iOS 8 -> pwn kernel -> initiate pwned boot sequence from kernel -> boot into pwned iOS 9
If I'm not mistaken, that should be doable without an APTicket, so long as the firmware keys for the target version (iOS 9) are available for your device (or they're unencrypted as in 10), and you have a working patchfinder for the target kernel and either also for the bootloaders, or have a custom bootloader that sets up an environment which the kernel can work with.
However, finding a working patchfinder might prove difficult to impossible. I found this Reddit post on how to do dual-boot, but it requires valid blobs for the target OS, since it uses the stock bootloaders.
Bottom line: It's a hell of a lot of work, I don't think there's some "out of the box" software that does it all for you, and most importantly: it's very easy to mess up and have your device boot-loop.

My advice? Stay on 8.4.1 ;)
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Re: Updating iPhone firmware using OTA zip files

Postby ITguy » Thu Sep 29, 2016 10:01 am

Siguza wrote:No, not like that.
The reason is the same as why you can't update to an older version with iTunes: APTicket.
The APTicket is not only checked on restore, but also saved on your device and checked on every boot. If you can't get a valid APTicket for the versions of iLLB, iBoot and the kernel you're using, your device isn't gonna boot.
You should theoretically be able to replace everything but the bootloaders and the kernelcache, but then you'd be running iOS 9 with an iOS 8 kernel, which seems like the perfect recipe for a disaster to me.

What you might be able to do, however (with an actual chance of success), since you're still on 8 and thus pre-KPP, is a dual-boot.
The concept would basically be:
Boot iOS 8 -> pwn kernel -> initiate pwned boot sequence from kernel -> boot into pwned iOS 9
If I'm not mistaken, that should be doable without an APTicket, so long as the firmware keys for the target version (iOS 9) are available for your device (or they're unencrypted as in 10), and you have a working patchfinder for the target kernel and either also for the bootloaders, or have a custom bootloader that sets up an environment which the kernel can work with.
However, finding a working patchfinder might prove difficult to impossible. I found this Reddit post on how to do dual-boot, but it requires valid blobs for the target OS, since it uses the stock bootloaders.
Bottom line: It's a hell of a lot of work, I don't think there's some "out of the box" software that does it all for you, and most importantly: it's very easy to mess up and have your device boot-loop.


Thanks a lot for your reply. That was really very helpful indeed!
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