Bootloader unlocking

An unlocked bootloader, showing additional available options

Bootloader unlocking is the process of disabling the bootloader security that makes secure boot possible. It can make advanced customizations possible, such as installing custom firmware. On smartphones, this can be a custom Android distribution or another mobile operating system. Some bootloaders are not locked at all and some are locked, but can be unlocked with a command or with 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.

Background

Unlocking the bootloader usually voids any warranties and may make the device susceptible to data theft.^[1] On Chromebooks, enabling developer mode makes the system less secure than a standard laptop running Linux.^[2] Unlocking the bootloader may lead to data loss on Android and ChromeOS devices, as some data is impossible to back up without root permission. This will also lead to certain security apps not working, such as Samsung Knox for which the counter would be stuck at "0x1."

Sascha Segan from PCMag considered a locked bootloader a mistake on the Qualcomm Snapdragon Insiders phone, which is targeted at advanced users.^[3]

Platforms

Android

Unlocking the bootloader is typically done during the process of obtaining root access and/or installing a custom ROM.

Android bootloader unlocking as of 2024

Manufacturer	Difficulty level	Method
Google	Easy (non-Verizon) Impossible (Verizon)	Command-line (unlocked variant, not restricted to carrier, and non-Verizon carrier variants when paid off fully)
Samsung	Easy (EU and others) Impossible (US)	Development settings (except North American cellular variants), however, if modified or custom firmware is flashed, Samsung Knox will be permanently tripped, so Samsung Wallet, Secure Folder and applications made use of the Knox framework will be permanently unusable even if the bootloader is re-locked. (Not all Samsungs device have Knox, for example: J7 Prime do not have Knox eFuse.) [4]
OnePlus	Easy (non-T-Mobile) Medium (T-Mobile)	Command-line, except on T-Mobile US variants where an unlock code is needed
Xiaomi	Hard (outside China Mainland) Very Hard (China Mainland)	Add Mi account, request code via Windows-only software, wait for 3 days on HyperOS or 1 week for MIUI (limited to one device per month and three devices per year). On devices with HyperOS outside mainland China, you need to request for bootloader unlock permission in the Xiaomi Community app before you can add your account. Your Xiaomi account needs to be at least 1 month old to be eligible. For Mainland China devices with HyperOS, you need to reach Xiaomi Community Level 5 and take an exam and pass the manual grading before you can add your account. On some devices with Mediatek system on a chip it might be possible to unlock using MTKClient, a third-party tool.
Asus	Impossible	Unlocking was performed via a first-party unlocking tool, but servers and app were removed.
Sony	Medium	Command-line, request code at Sony website
Fairphone	Medium	Command-line, request code at Fairphone website or forum
Motorola	Medium (non Verizon, AT&T, Tracfone) Impossible (Verizon, AT&T, Tracfone)	Command-line, request code at Motorola website
Realme	Medium-Hard (China Mainland and India) Impossible (global)	Command-line, after installation of the in-depth test app and submitting an application for in-depth testing.
Nothing	Easy	Command-line
Huawei	Medium-Hard (Kirin SoCs, select Huawei phones) Impossible, due to unlocking services being shut down (Other devices)	Select Huawei phones using the Kirin SoC can have their bootloader unlocked via potatonv: https://www.xda-developers.com/huawei-honor-bootloader-unlock-potatonv/ Other devices: N/A
OPPO	Easy (MediaTek) or phones that bought in mainland China[5] Medium (Snapdragon) Only any phones in support list are possible to unlock Snapdragon-powered OPPO phone,[6] any phones that's not in support lists is still possible if using paid tool also known as UnlockTool, without paid tool. It would be impossible to unlock. Unlocking is possible on some mediatek SoCs via MTKClient. Note that about fastboot binaries were removed, or locked by RSA key	Snapdragon: https://us.docs.wps.com/l/sIIS95rToAcW2x7AG?v=v2[7] MediaTek: MTKClient, sometimes MTK bypass utility are required beforehand Any phones that's bought from mainland China and in device support lists of depth-test: Unlock by depth test regardless of SoC, depth test app can be downloaded from https://www.oppo.cn/thread-397164526-1 then unlock via adb with simple command line while in fastboot state If you are getting "Handshake failed" on MTKCilent, then it is necessary to test point to force boot into boot ROM
HMD-Nokia	Impossible	N/A
vivo	Impossible[8] Unless there are XDA forums that have methods to unlock, but some method cannot be used after updated phone patched exploit. The user can access fastboot, but the manufacturer has modified the bootloader so that it does not respond to any commands to unlock bootloader.	Vivo X70 Pro+ https://xdaforums.com/t/vivo-x70-pro-bootloader-unlock-how-to-guide.4444989/ Vivo Y31 2021 https://xdaforums.com/t/unlocking-bootloader-rebooting-in-edl-without-testpoint-vivo-y31-2021.4440801/
LG	Hard	Possible, with the help of leaked engineering bootloaders available to be flashed via QFIL utility
Tecno	Medium	Command-line, (requires Tecno ID account on the phone, registered in two weeks or more, to activate OEM unlocking.)
Infinix	Medium	Command-line, (requires Infinix ID account on the phone, registered in two weeks or more, to activate OEM unlocking.)
Itel	Medium	Command-line, (requires Itel ID account on the phone, registered in two weeks or more, to activate OEM unlocking.)
TCL	Medium (Ion V only) Unknown (other phones)	For the Ion V mobile phone, you can use a Python tool to reboot to a normally hidden fastboot, then use the fastboot command 'fastboot flashing unlock' to unlock it.
Amazon (fire hd)	Medium	Brick while fastbooting via adb command line (only Linux)

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 your Motorola device.^[15]

A 2012 article by The Verge called the unlockable bootloaders a 'broken promise' and called for a fix.^[16]

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.^[17] In addition, some manufacturers prohibit unlocking on carrier locked phones. Although Samsung phones and cellular tablets sold in the US and Canada do not allow bootloader unlocks regardless of carrier status, a service has allowed users on an earlier version to unlock their US/Canadian Samsung phone(s) and/or tablet(s)^[18][19]

In 2018, a developer from XDA Developers launched a service which allowed users to unlock the bootloader of some Nokia smartphone models.^[20] 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.

Huawei announced plans to allow users to unlock the bootloader of the Mate 30 series, but later retracted that.^[21] Huawei has stopped providing bootloader unlock codes since 2018.^[22] A bootloader exploit named checkm30 has been developed for HiSilicon based Huawei phones.^{[23][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.^[24] This issue was later fixed by Samsung.^[25] For the Samsung Galaxy S22 series, unlocking the bootloader has no effect on the camera.^[26]

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.^[27][28] Version 1.0 was released in November 2015.^[29] In October 2018, the tool was released as open source software when the main developer René Lergner (also known as HeathCliff74) stepped down.^[30]

The slab bootloader used by Windows RT could be unlocked using a vulnerability, but was silently patched by Microsoft in 2016.^[31] 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.^[32]

The bootloader on Apple Silicon-based Macs can be unlocked.^[33] However, other Apple devices like the iPhone and iPad cannot be bootloader unlocked even when using the same chip used in a Mac.

Google

The equivalent of bootloader unlocking is called developer mode in Chromebooks.^[34] Chromebooks use custom bootloaders that can be modified or overwritten by removing a Write-protect screw.^[35] Some models lack a screw and instead may or may not require disabling the onboard Cr50 chip.[1]

In 2013, the bootloader of the Chromecast was hacked using an exploit.^[36] In 2021, it was hacked again for newer versions.^[37] In 2023, it was reported that the Chromecast HD could be unlocked without exploit.^[38]

Asus

Asus used to provide an Unlocking tool for both of their smartphone lines, the Zenfone and ROG Phone. This worked as an installable .apk file that the user could install on their phone, then unlock the bootloader. The app worked by contacting Asus unlocking servers, then prompting the user to perform a factory reset.

In 2023 Asus removed the tool from their website and closed the unlocking servers, so even phones with the .apk file installed couldn't unlock their bootloaders. Representatives on the Asus forums claimed the tool would be available again, but as of March 2024 no additional information has been provided, even after the release of their latest device the ROG Phone 8 and the upcoming release of the Zenfone 11 Ultra.

A user on the popular forum XDA (website) filed a court claim application against Asus due to the unlock tool never being released and alleged that Asus censored comments about the unlock tool on their form.^[39]

SpaceX

In August 2022, security researcher Lennert Wouters applied a voltage injection attack to bypass firmware verification of a Starlink satellite dish from SpaceX.^[40]

Relocking

On Android, it is possible to relock the bootloader.^[41]

VNeID app changes

According to information from technology groups in Vietnam, after updating version 2.1.6 of the VNeID application released on May 30, 2024, some Android phone users have received warnings : "Your device is not safe, there is a risk of containing malicious code...". As a result, users are thrown to the main screen and cannot use the VNeID application, even though before the update they could still log in and use it normally.

This is because VNeID 2.1.6 update has added new security measures to stop working on Android devices with root access, unlocked bootloader and developer mode enabled. To use, users must disable root access to the device, relock bootloader and turn off developer options.^[42]

Shutdown of online services

In 2018, Huawei stopped providing bootloader unlock codes.^[43] On 31 December 2021, LG shut down their website which provided bootloader unlock codes.^[44] In August 2023, ASUS removed the unlocking tool from their website and shut down the servers used to unlock the bootloader.^[45]

See also

• Booting process of Android devices
• Odin
• Boot ROM § Security

References

1. Tamma, Rohit; Donnie Tindall (2015). Learning Android forensics: a hands-on guide to Android forensics, from setting up the forensic workstation to analyzing key forensic artifacts. Birmingham, UK. ISBN 978-1-78217-444-8. OCLC 910639389.
2. Porup, J. M. (2017-06-19). "How to install Linux on a Chromebook (and why you should)". Ars Technica. Archived from the original on 2017-06-19. Retrieved 2021-09-06.
3. "Qualcomm Smartphone for Snapdragon Insiders Review". PCMag. Archived from the original on 2021-08-16. Retrieved 2021-09-06.
4. https://www.samsungknox.com/en/knox-platform/supported-devices
5. "帖子详情 - Oppo社区".
6. "Proton Drive".
7. "Tutorial can be foun…". 12 May 2024.
8. "vivo Smartphone FAQs | vivo India". www.vivo.com. Retrieved 2022-11-29.
9. "Factory Images for Nexus and Pixel Devices | Google Play services". Google Developers. Retrieved 2022-11-07.
10. Ingraham, Nathan (2011-10-24). "GSM Motorola RAZR hits the FCC; Verizon model has locked bootloader". The Verge. Retrieved 2022-06-14.
11. By (2011-04-14). "Sony Ericsson Promotes Android Bootloader Unlocking". Hackaday. Retrieved 2022-06-14.
12. Kotipalli, Srinivasa Rao; Mohammed A. Imran (2016). Hacking Android: explore every nook and cranny of the Android OS to modify your device and guard it against security threats. Birmingham, UK. ISBN 978-1-78588-800-7. OCLC 957298786.
13. Tiefenthäler, Ronald (22 February 2012). "Asus: Bootloader Unlock Tool für Tablet Transformer Prime TF201 verfügbar". Notebookcheck (in German). Retrieved 2021-08-04.
14. Rodgers, Evan (2012-08-17). "Motorola unveils Android bootloader unlocking tool with limited device support". The Verge. Archived from the original on 2012-08-19. Retrieved 2021-09-10.
15. Viscomi, Rick; Andy Davies; Marcel Duran (2015). Using WebPageTest: web performance testing for novices and power users. Sebastopol, CA. ISBN 978-1-4919-0281-3. OCLC 927108295.
16. Kopfstein, Janus (2012-11-20). "Access Denied: why Android's broken promise of unlocked bootloaders needs to be fixed". The Verge. Retrieved 2024-11-22.
17. Afonin, Oleg (2016). Mobile Forensics ' Advanced Investigative Strategies (1 ed.). Packt Publishing. ISBN 978-1-78646-408-8. OCLC 960040717.
18. "USA/Canada - Samsung Bootloader Unlock". Telegram. Retrieved 2024-06-18.
19. "[CLOSED][Android][UNSAMLOCK] Bootloader Unlock for Samsung US/Canada Devices". XDA Forums. 2021-01-08. Retrieved 2024-06-18.
20. Rox, Ricci (2 April 2018). "Nokia users can now unofficially unlock their bootloaders but the methodology is as sketchy as it gets". Notebookcheck. Retrieved 2021-09-06.
21. "Huawei Mate 30 will not have an unlocked bootloader". The Indian Express. 2019-09-25. Archived from the original on 2019-09-26. Retrieved 2021-09-06.
22. "Huawei will no longer offer bootloader unlock codes for its Android devices". 9to5Google. 2018-05-24. Retrieved 2021-09-06.
23. "Checkmate Mate 30 - Attack the bootrom of Huawei smartphones" (PDF). Archived (PDF) from the original on 2021-09-06.
24. Clark, Mitchell (2021-08-24). "Samsung will let you unlock your Z Fold 3's bootloader, but at the cost of your cameras". The Verge. Archived from the original on 2021-08-24. Retrieved 2021-09-06.
25. "Unlocking the bootloader no longer kills the Galaxy Z Fold 3's cameras". xda-developers. 2021-12-07. Retrieved 2022-03-14.
26. "Unlocking the bootloader doesn't break the camera on the Samsung Galaxy S22 series". xda-developers. 2022-02-26. Retrieved 2022-02-26.
27. "Tool van Nederlandse ontwikkelaar kan custom roms op alle Lumia's flashen". Tweakers (in Dutch). Retrieved 2021-08-04.
28. "Windows Phone Internals 2.2 Unlocks the Bootloader on all Windows 8 & 10 Lumia Smartphones". xda-developers. 2017-12-04. Retrieved 2021-08-04.
29. Andrew Orlowski. "Rooting and modding a Windows Phone is now child's play". The Register. Retrieved 2022-06-14.
30. "Windows 10 Mobile's bootloader unlocker is now open source". Neowin. Retrieved 2022-06-14.
31. Francisco, Shaun Nichols in San. "Microsoft silently kills dev backdoor that boots Linux on locked-down Windows RT slabs". www.theregister.com. Retrieved 2021-09-06.
32. Lundberg, Anders. "16-year-old runs Linux on iPhone 7". Macworld UK. Retrieved 2021-08-04.
33. January 2021, Michelle Ehrhardt 19 (2021-01-19). "Linux is Finally on Apple M1...Kind Of". Tom's Hardware. Retrieved 2021-08-04.
34. December 2014, Lucian Armasu 31 (2014-12-31). "You Can Now Run Full Linux Apps Inside A Chrome OS Window". Tom's Hardware. Retrieved 2021-09-06.
35. Robert, Foss (2017-03-08). "Quick hack: Removing the Chromebook Write-Protect screw". Collabora. Retrieved 2021-09-04.
36. "Chromecast bootloader exploit surfaces, opens up plenty of possibilities (video)". Engadget. 28 July 2013. Archived from the original on 2020-09-04. Retrieved 2021-09-06.
37. "Modders ontgrendelen bootloader van Google Chromecast met Google TV". Tweakers (in Dutch). Archived from the original on 2021-08-01. Retrieved 2021-09-06.
38. "Chromecast with Google TV HD bootloader can be unlocked by default". 9to5Google.
39. "Court Action against Asus' false promise on bootloader unlock tool". XDA Forums. 2024-02-18. Retrieved 2024-03-23.
40. Hardcastle, Jessica Lyons. "Starlink satellite dish cracked on stage at Black Hat". The Register. Retrieved 2022-11-22.
41. Wilde, Damien (2021-09-09). "How to downgrade from Android 12 Beta to Android 11 on Google Pixel [Video]". 9to5Google. Retrieved 2021-09-28.
42. "Người dùng Android Root/Unlock Bootloader không cập nhật được VNeID 2.1.6: Làm sao để khắc phục?". 24hstore.vn (in Vietnamese). 2024-05-30. Retrieved 2024-06-07.
43. "Huawei stopt met het uitdelen van codes om bootloader vrij te geven". Tweakers (in Dutch). Retrieved 2023-05-07.
44. "LG stopt eind dit jaar met tool voor unlocken van smartphonebootloaders". Tweakers (in Dutch). Retrieved 2023-05-07.
45. "ASUS is apparently killing the ability to root Zenfones". Android Authority. 8 August 2023. Retrieved 2024-01-30.

External links

• Locking/Unlocking the Bootloader, Android Open Source Project
• Qualcomm's Chain of Trust