Bootloader unlocking[a] is the process of disabling the bootloader security that makes secure boot possible. It can make advanced customizations possible, such as installing a custom firmware. On smartphones this can be a custom Android distribution or another mobile operating system. Some bootloaders are not locked at all, others can be unlocked using a standard command, others need assistance from the manufacturer. Some do not include an unlocking method and can only be unlocked through a software exploit.
Bootloader unlocking is also done for mobile forensics purposes, to extract digital evidence from mobile devices, using tools such as Cellebrite UFED.[1]
Background
Unlocking the bootloader usually voids any warranties and may make the device susceptible to data theft.[2][3] On Chromebooks, enabling developer mode makes the system less secure than a standard laptop running Linux.[4] Unlocking the bootloader may lead to data loss on Android and ChromeOS devices, as some data is impossible to back up without root permission.
Sascha Segan from PCMag considered a locked bootloader a mistake on the Qualcomm Snapdragon Insiders phone, which is targeted at advanced users.[5]
Platforms
Android
Unlocking the bootloader is typically done during the process to obtain root access.
| Manufacturer | Difficulty level | Method |
|---|---|---|
| Easy | Command-line (unlocked variant, not restricted to carrier) | |
| Samsung | Easy | Development settings (except North America variants) |
| OnePlus | Easy | Command-line |
| Xiaomi | Very Hard | Add account, request code, wait a week |
| Sony | Hard | Command-line, request code at Sony website |
| Fairphone | Hard | Command-line, request code at Fairphone website |
| Motorola | Hard | Command-line, request code at Motorola website |
| Realme | Hard | Command-line, after installation of realme-app |
| Huawei | Impossible | N/A |
| OPPO | Impossible | N/A |
| HMD-Nokia | Impossible | N/A |
| vivo | Impossible[7] | N/A |
| LG | Impossible[8] | N/A |
| Tecno | Impossible | N/A |
| Infinix | Impossible | N/A |
| TCL | Impossible | N/A |
History
The bootloaders of Nexus and Pixel devices can be unlocked by using the fastboot command fastboot oem unlock or if it doesn't recognize the command fastboot flashing unlock.[9]
When Motorola released a bootloader unlocking tool for the Droid Razr, Verizon removed the tool from their models.[10]
In 2011, Sony Ericsson released an online bootloader unlocking tool.[11] Sony requires the IMEI number to be filled in on their website.[12] For the Asus Transformer Prime TF201, Asus has released a special bootloader unlock tool.[13]
In 2012, Motorola released a limited tool for unlocking bootloaders.[14] They require accepting terms and conditions and creating an account before the bootloader can be unlocked for a Moto G.[15]
HTC phones have an additional layer of lock called "S-OFF/S-ON".
Bootloaders can be unlocked using an exploit or using a way that the vendor supplied. The latter method usually requires wiping all data on the device.[1] In addition, some manufacturers prohibit unlocking on carrier locked phones. Samsung's US and Canadian Snapdragon phones do not allow unlocks regardless if the phone was bought from a carrier or not.
In 2018, a developer from XDA Developers launched a service which allowed users to unlock the bootloader of some Nokia smartphone models.[16] Similarly, another developer from XDA Developers launched a service to allow users to unlock the bootloaders of Samsung Galaxy S20 and Samsung Galaxy S21 Phones.[17]
Huawei announced plans to allow users to unlock the bootloader of the Mate 30 series, but later retracted that.[18] Huawei has stopped providing bootloader unlock codes since 2018.[19] A bootloader exploit named checkm30 has been developed for HiSilicon based Huawei phones.[20][non-primary source needed]
When the bootloader of the Samsung Galaxy Z Fold 3 was unlocked, the camera became less functional. This could be restored by re-locking the bootloader.[21] This issue was later fixed by Samsung.[22] For the Samsung Galaxy S22 series, unlocking the bootloader has no effect on the camera.[23]
Others
Microsoft
The WPInternals tool is able to unlock bootloaders of all Nokia Lumia phones running Windows Phone, but not phones like the Alcatel Idol 4 or HP Elite x3.[24][25] Version 1.0 was released in November 2015.[26] In October 2018, the tool was released as open source software when the main developer René Lergner (also known as HeathCliff74) stepped down.[27]
The slab bootloader used by Windows RT could be unlocked using a vulnerability, but was silently patched by Microsoft in 2016.[28] UEFI Secure Boot on x86 systems can generally be unlocked.
Apple
The boot ROM protection on iOS devices with an A11 processor or older can be bypassed with a hardware exploit known as checkm8, which makes it possible to run other operating systems including Linux.[29]
The bootloader on M1 based Macs can be unlocked.[30]
The equivalent of bootloader unlocking is called developer mode in Chromebooks.[31] Chromebooks use custom bootloaders that can be modified or overwritten by removing a Write-protect screw.[32]
In 2013, the bootloader of the Chromecast was hacked using an exploit.[33] In 2021, it was hacked again for newer versions.[34]
SpaceX
In August 2022, security researcher Lennert Wouters applied a voltage injection attack to bypass firmware verification of a Starlink satellite dish from SpaceX.[35]
Relocking
On Android, it is possible to relock the bootloader.[36]
Shutdown of online services
In 2018, Huawei stopped providing bootloader unlock codes.[37] On 31 December 2021, LG shut down their website which provided bootloader unlock codes.[38]
See also
Explanatory notes
- Also called developer mode, OEM unlock or jailbreaking
References
- "LG stopt eind dit jaar met tool voor unlocken van smartphonebootloaders". Tweakers (in Dutch). Retrieved 2023-05-07.
External links
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| Booting firmware |
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| Hybrid firmware bootloader | |||||||
| Bootloaders |
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| Partition layouts | |||||||
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| Utilities |
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| Network boot | |||||||
| ROM variants | |||||||
| Related | |||||||
https://en.wikipedia.org/wiki/Bootloader_unlocking
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