iDeviceReRestore

iDeviceReRestore

Original author(s)	alitek123, Trevor, Jonathan Seals
Developer(s)	alitek123, Trevor, Jonathan Seals
Initial release	2 April 2017
Stable release	1.2 (macOS, Windows, Linux) / 6 August 2017
Development status	Active
Operating system	macOS / Windows / Linux
Available in	English
Type	Downgrading
License	GNU LGPL 2.1
Website	iDeviceReRestore

iDeviceReRestore is a tool based off of idevicerestore that can be used to downgrade 32-bit devices to any iOS 9 version, provided the user has SHSH blobs for the version. It uses a bug discovered in 32-bit versions of iOS 9.x iBoot's APTicket verification routines which allows valid cached tickets with a missing APNonce, regardless of the current nonce.

The bug only exists in iOS 9, but it does not require you to currently run iOS 9 to use it. The reasoning being, due to the fact that all 32-bit bootroms (other than Apple Watch) verify the next bootloader, iBSS, based on SHSH when in DFU Mode rather than with APTicket, with no enforcement of APNonce, you can always boot into your iBSS you have cached blobs for, via DFU mode, regardless of your current APNonce. Furthermore, 9.x iBSS has the same bug as all other 9.x 32-bit iBoot, and so you can continue a restore straight from there. On a firmware without the bug, or when using an iOS 9.x APTicket with an APNonce, iBSS will not accept your APTicket, and will not continue into the rest of the restore chain.

Notes

• iDeviceReRestore works for 32-bit iOS devices only. (Apple Watch is not included.)
• The initial firmware does not matter.
• The initial firmware does not require a jailbreak.
• The destination firmware must be iOS 9.x. SHSH blobs for the destination firmware are required.
• The process does not require keys, bundles, or nonces.
  • The SHSH blobs cannot be OTA blobs. They can be Erase or Update blobs, though not all of them will work.
  • They must have been saved without a nonce.
  • Restores from DFU require a cached iBSS SHSH blob (dumped blobs will not include this).
  • Most tickets saved by Cydia seem to be usable for this, and include iBSS SHSH blobs.
• The technique requires a signed baseband, like Prometheus. However, between the currently signed basebands for iOS 9 and 10, most devices (if not all) should be able to get a working baseband without issues. The tool automatically downloads the latest baseband available per device by default, but the user has the option of specifying their own OTA signed baseband.
• iOS 9 -> iOS 9 restores can be done from Recovery Mode. Devices on other firmwares must be restored from DFU Mode.
• On A6 devices (iPhone 5, iPad 4), Apple has blocked activations server-side on 9.x and lower if the device was previously on 10.x.