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Difference between revisions of "Firmware downgrading"
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| − | Downgrading is the process of restoring to an older [[firmware]]. Apple does not allow downgrading unless the firmware is being signed. |
+ | Downgrading is the process of restoring to an older [[firmware]]. Apple does not allow downgrading unless the firmware is being signed. Previously, downgrading was only possible on older devices that have SHSHs saved and are vulnerable to [[bootrom]] exploits such as the [[limera1n Exploit]]. However, it has become possible to downgrade devices with no (known) bootrom exploits to certain firmware versions, such as remaining on iOS 5.x or downgrading to iOS 6.1.3. It is also possible to downgrade an [[iPad 2]] to 5.x with 4.x and 5.x SHSH or 4.x with only 4.x SHSH blobs. iPhone 4s and iPad 2 downgrading will require [[redsn0w]]. [[Odysseus]] can be used on some devices to downgrade to certain iOS versions providing the user has SHSH blobs and the device is jailbroken. OdysseusOTA can be used to downgrade an iPhone 4s or iPad 2 to 6.1.3 from any firmware providing the device is jailbroken even without SHSH blobs due to Apple not closing the signing of 6.1.3 OTA's for those devices. [https://www.youtube.com/watch?v=fh0tB6fp0Sc&feature=youtu.be&a OdysseusOTA2] can be used to downgrade an iPhone5,2 to 8.4.1 the same way that OdysseusOTA did with iPhone 4s and iPad 2. |
== Reason for downgrading == |
== Reason for downgrading == |
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| − | Some users downgrade since iOS 7 does not run well |
+ | Some users downgrade to older iOS versions since, for example, iOS 7.x does not run as well as older versions on outdated devices such as the iPhone 4, or iOS 9.x on the iPhone 4S. This could also be for nostalgia. There are many reasons as to why one would prefer an older version of iOS. |
| + | ==Restoring to Older Firmwares via Any Method== |
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| − | == Issues == |
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| + | Downgrade iTunes to 11.0 or 10.7 and then restore when in PwnDFU. |
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| − | Devices without a [[ramdisk]] change will have an issue in which when iOS reboots or goes into deep sleep, it will verify the [[LLB]] and since the LLB is part of the bootchain it will not be overwritten and therefore causes iOS to disable the LCD. To circumvent this, users will have to disable the power management daemon. |
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| + | [[Category:Downgrading]] |
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| − | ==Tethered downgrades== |
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| − | Create an IPSW to make Apple's TSS server think the IPSW you're restoring to is on a signed version or build one with blobs from the same device model and iOS version you want to go to (you can do this with redsn0w). This means you can use another person's SHSH blobs. For example, GeekGrade is iFaith IPSWs with prevent sleep preinstalled in them or a modified [[ramdisk]]. (Keep in mind this was done with iH8sn0w's work and also violates Apple's copyright by redistributing their iOS.) Also, to fix the dead LCD and DFU loop, you can use xpwntool to disable the flashing of a new iOS bootchain. |
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| − | ==Restoring to custom firmwares== |
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| − | Downgrade iTunes to 11.0 and then restore in PwnDFU. If you did not change anything in the [[ramdisk]], you should get Error 37 and then get kicked into [[DFU Mode]]. If you did, it should show what usually happens after any restore and go into Recovery Mode. |
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| − | ==Booting== |
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| − | [[Limera1n]] allows us to skip SHSH blob verification during boot time. Therefore a downgraded device with invalid SHSH blobs can boot into iOS without issues. For devices with just the blobs signed without [[ramdisk]] modification, you will need to select your IPSW in redsn0w and then select "Recovery fix". Afterwards, you can use the tether boot option. For the ones with a modified [[ramdisk]], you can simply select the stock IPSW needed for that iOS version and then tether boot. Using these methods, your device will boot into iOS. For an iOS 7 tethered downgrade, you require [[opensn0w]] to boot the device. |
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Latest revision as of 10:45, 27 September 2021
Downgrading is the process of restoring to an older firmware. Apple does not allow downgrading unless the firmware is being signed. Previously, downgrading was only possible on older devices that have SHSHs saved and are vulnerable to bootrom exploits such as the limera1n Exploit. However, it has become possible to downgrade devices with no (known) bootrom exploits to certain firmware versions, such as remaining on iOS 5.x or downgrading to iOS 6.1.3. It is also possible to downgrade an iPad 2 to 5.x with 4.x and 5.x SHSH or 4.x with only 4.x SHSH blobs. iPhone 4s and iPad 2 downgrading will require redsn0w. Odysseus can be used on some devices to downgrade to certain iOS versions providing the user has SHSH blobs and the device is jailbroken. OdysseusOTA can be used to downgrade an iPhone 4s or iPad 2 to 6.1.3 from any firmware providing the device is jailbroken even without SHSH blobs due to Apple not closing the signing of 6.1.3 OTA's for those devices. OdysseusOTA2 can be used to downgrade an iPhone5,2 to 8.4.1 the same way that OdysseusOTA did with iPhone 4s and iPad 2.
Reason for downgrading
Some users downgrade to older iOS versions since, for example, iOS 7.x does not run as well as older versions on outdated devices such as the iPhone 4, or iOS 9.x on the iPhone 4S. This could also be for nostalgia. There are many reasons as to why one would prefer an older version of iOS.
Restoring to Older Firmwares via Any Method
Downgrade iTunes to 11.0 or 10.7 and then restore when in PwnDFU.
