View source for Preventing Baseband Update

== Edit <code>options.plist</code> ==
# Unpack custom [[IPSW File Format|IPSW]]
# Decrypt Restore Ramdisk using [[xpwntool]] and mount it
# Navigate to /usr/local/share/restore/
# Edit options.plist on the [[Restore Ramdisk]] (Ignore any other settings specified in the plist, don't edit them)
        <key>UpdateBaseband</key>
        <false/>
<ol start="5">
<li>Reencrypt the restore ramdisk</li>
<li>Repack the [[IPSW File Format|IPSW]]</li>
<li>Prepare device for custom firmware using [[redsn0w]]</li>
<li>Restore the [[IPSW File Format|IPSW]] to [[iTunes]] in pwned [[DFU Mode]] using the appropriate method (Look at Restoring The Modified IPSW Section)</li>
</ol>
You must load a patched [[iBSS]]/[[iBEC]] for this to work. Using an original [[IPSW File Format|IPSW]] will not work, because [[redsn0w]]'s pwned DFU Mode doesn't patch sigchecks in [[iBSS]] (which is loaded from the [[IPSW File Format|IPSW]]).

== Idea ==
One could hook the function HookAMRestorePerformRecoveryModeRestore in the [[MobileDevice Library]] that [[iTunes]] uses, overriding the restore options CFDictionaryRef object. This would *THEORETICALLY* allow for not updating baseband without patches/[[jailbreak]]. A practical application for this is if someone absolutely needs to update to the latest firmware for work or other reasons, and can't as they must wait for PwnageTool to provide support.

== Restoring The Modified IPSW ==
[[Firmware]]s like 4.2.1 and above have baseband checks on the [[Restore Ramdisk]]. If the modified [[IPSW File Format|IPSW]] is restored, [[iTunes]] will give an [[iTunes Errors|Error 1015]] and the iDevice will be in a recovery mode loop which cannot be exited by TinyUmbrella or the 'setenv auto-boot true' command

Fortunately, the [[Update Ramdisk]] does not contain that baseband check so if the Update Method is used which is mentioned below, [[iTunes]] will give an [[iTunes Errors|Error 1013]] and it can be exited by [[TinyUmbrella]] and the [[iRecovery]] command.
=== Update Method ===
* Windows Users, Open iTunes. hold the Shift button and click Update then select the modified IPSW
* Mac Users, Open iTunes, hold the Alt button and click Update then select the modified IPSW
=== Restore Method ===
* Windows Users, Open iTunes. hold the Shift button and click Restore then select the modified IPSW
* Mac Users, Open iTunes, hold the Alt button and click Restore then select the modified IPSW

== [[TinyUmbrella]]/[[Cydia Server]] Method ([[iPhone 4]]) ==
The [[iPhone 4]] requires a [[AT+XNONCE]] key signature from Apple in order to update the baseband. Pointing the hosts file to [[Cydia Server]] or running [[TinyUmbrella]] will allow this request for signature to be ignored, thus preventing a [[baseband]] update.

*'''This only works if [[Cydia Server]]/[[TinyUmbrella]] accepts the firmware's SHSH.'''
*'''This method 'works' with [[iOS]] 4.2.1, but in the restore ramdisk there is a baseband version check. If it doesn't match, it will crash before the Apple logo with the loading bar (the 2nd, first-boot  one, not the restore one) appears. It will boot and crash again. The old 'Kick out of recovery mode' methods or "setenv auto-boot true" won't work, because it's not the problem that the auto-boot is false. So this method is actually not useful for [[iOS]] 4.2.1+.'''
*'''[[greenpois0n (jailbreak)|greenpois0n]] RC6 will fix this as part of the jailbreaking process. The latest version of TinyUmbrella also features a new Fix Recovery function.'''
# Edit the hosts file and add the line "74.208.10.249 gs.apple.com" without the quotes, or run [[TinyUmbrella]] after saving the firmware's SHSH. If [[Cydia Server]] hasn't got your [[SHSH]], but you have it locally, use TSS Server method in [[TinyUmbrella]].
# Use the "Restore" button in [[iTunes]] to update if your firmware version is below 4.2 else use the "Update" button in [[iTunes]] to update.
# You will get Error 1013 and it can be easily bypassed by using the Exit Recovery Mode button in [[TinyUmbrella]] or typing 'setenv auto-boot true' and 'saveenv' in [[iRecovery]]

== [[User:Ih8sn0w|iH8Sn0w]]'s Method==
[[sn0wbreeze]] has a "Baseband Preservation Mode" since version 2.2. [[User:Ih8sn0w|iH8sn0w]] [http://twitter.com/iH8sn0w/status/19453808090288128 confirmed] that his method is not the same as the above mentioned methods.

This method can also be used on the [[N88AP|iPhone 3GS]] and the [[iPhone 4]] to downgrade from the 4.3 betas and above back to 4.2.1, as long as the device can be restored (and activated) to iOS 4.1 or an earlier version.

To get some more details about what [[sn0wbreeze]] with the option "Baseband Preservation Mode" does, here a short analysis - a comparison of the generated ipsw for iOS 4.3 (iPhone 4):
=== [[:/|Root Filesystem]] (038-0688-006.dmg) ===
(Details to be added.)
=== [[Restore Ramdisk]] (038-0715-006.dmg) ===
==== options.plist ====
The file options.plist in the folder \ramdisk\usr\local\share\restore is changed. These are the changes:
*first entry added: CreateFilesystemPartitions = true
*changed value: SystemPartitionSize 1024 changed to 1050
*added last entry: UpdateBaseband = false
==== [[ASR]] ====
In the folder \ramdisk\usr\sbin\ the file asr has been renamed to asr_orig and a patched file of size 180832 bytes added. The patches are:
 0001321A: DF F8
 0001321A: FD E7

 0002BFC6: ED B7 6C AA D3 AF A0 B4 90 08 6D 63 51 46 17 0B 8A 40 8D C4
 0002BFC6: 6E DB 54 D3 DB 60 A8 FB 74 47 28 EB 02 33 EA FA 20 B6 7E B5

 0002C1BA: FA DE 0C 01
 0002C1BA: F6 B6 D0 8F
==== Images ====
Two files were changed from the Apple logo to the iH8sn0w logo. Both are called applelogo.png and they are located in \ramdisk\usr\share\progressui\images-1x\ and in \ramdisk\usr\share\progressui\images-2x\.
=== Patches in [[iBSS]] ===
There are several patches in [[iBSS]] (first line is original, second line is the patched version):
 000000FC: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 000000FC: 03 A2 13 68 1B B1 50 68 C8 50 08 32 F9 E7 70 47 E0 A9 8C 00 30 E0 00 20 A4 AC 92 00 06 9B 0B B1 A8 AC 92 00 00 23 04 D0 D8 D3 71 00 EA D1 01 20 E4 A9 8C 00 00 20 2D E0 5C DB 27 00 01
 
 00012C26: FF F7 73 FE
 00012C26: 00 20 00 20
 
 00012C4C: FF F7 60 FE
 00012C4C: 00 20 00 20
 
 00012C70: FF F7 B6 FE
 00012C70: 00 20 00 20
 
 00012C98: FF F7 3A FE
 00012C98: 00 20 00 20
 
 00012CBA: FF F7 29 00
 00012CBA: 00 20 00 20
 
 00012CDE: FF F7 17 FE
 00012CDE: 00 20 00 20
 
 00012D02: FF F7 05 FE
 00012D02: 00 20 00 20
 
 00012D20: FF F7 F6 FD
 00012D20: 00 20 00 20
 
 00012D44: FF F7 E4 FD
 00012D44: 00 20 00 20
 
 0001345A: 08 F0 0D
 0001345A: EC F7 4F
 
 0001AD38: 4F F0 FF 30
 0001AD38: 00 20 00 20

[[Category:Baseband]]