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Re-lock bootloader without erase?

I really hate that boot screen that makes you think your phone is going to blow up because the bootloader is unlocked... I realize that having it unlocked is perfectly fine, and with Magisk, all the Google security stuff still works just fine.. I also know that an unlocked booloader makes it much easier to flash updates (flash-all but remove the -w) ... So please don't try to explain why I should leave my bootloader unlocked.
WIth my HTC phones, unlocking the bootloader would erase the phone (obviously, and just like the Pixel 2). Locking the bootloader wouldn't erase the phone on the HTC, but with the Pixel 2, the instructions say that it WILL ERASE THE PHONE.
With the HTC, the wipe happened in recovery, so if I had TWRP installed, the phone wouldn't erase... I could easily switch between locked and unlocked, and as long as I had TWRP installed, the phone would "think" it was going to erase, but I stopped it.
So my question is... Does the Pixel 2 wipe the phone on lock/unlock through recovery? If so, can I lock the phone with TWRP installed in recovery and prevent that lock? I know I can make a backup and try it and see, but since the Feb update, getting into a decrypted recovery has become a pain (remove pin/password, reboot, reboot to recovery, do what you want, reboot to system, add the pin/password, add fingerprint, open EVERY SINGLE APP THAT USES FINGERPRINT AND SET LOGIN AND REGISTER THE FINGERPRINT - it frustrates me, in case you can't tell).

You cannot flash TWRP unless you are unlocked so at this time there is no way to unlock the bootloader without a full wipe.

I think you misunderstood the question. I have unlocked the bootloader (let it wipe) and installed TWRP. I want to know if the re-lock will wipe through recovery (and therefore be stopped by TWRP) or if it does the wipe using some other method (and therefore wiping regardless).

1. You won't be able to maintain your userdata while switching between locked and unlocked states.
2. You will likely not be able to boot your device either after locking your phone.
For 1)
The Pixel 2 enables FBE (filesystem-based encryption) by default for your userdata partition. The encryption keys are derived from a hardware secret (accessible only from TrustZone), the RSA public key that was used to sign the boot image and a flag (whether it is locked or unlocked). The latter parameters are provided by the bootloader (lk) to the Keymaster trustlet (running in TrustZone).
If any of these parameters change, then the encryption keys will change as well. As a result, your files will remain inaccessible even if you were hypothetically able to flip the lock state.
For 2)
Unlocking the bootloader (fastboot flashing unlock) will disable verification of the boot image. TWRP is installed by modifying the boot image (in both the "a" and "b" slots) which invalidates the Verified Boot signature that covers this boot image (stored in the vbmeta partition). When the device is locked again, the bootloader will fail to pass the signature check and stay in the "red" boot state. At that point I guess you have a brick (I have not tried this myself for obvious reasons).
Source: reading the lk source code and various Android documentation such as https://source.android.com/security/encryption/file-based

Lekensteyn said:
When the device is locked again, the bootloader will fail to pass the signature check and stay in the "red" boot state. At that point I guess you have a brick (I have not tried this myself for obvious reasons).
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The signature of the Custom ROM (Official LineageOS) can be integrated into the bootloader before re-locking the bootloader.
But this is the problem: "Lineage Recovery is also built in userdebug mode, that's a problem. When Lineage recovery is built this way, it allows any package, signed or unsigned, to be installed on your phone. This effectively negates the benefits of locking the bootloader. [...] In fact most custom ROMs simply use TWRP or another third party recovery which has the same issues as they are designed to never even look at the signatures of the packages they are flashing to your device."
"A discussion about bootloader locking/unlocking... AKA I want to relock my bootloader, should I?: LineageOS"
https://www.reddit.com/r/LineageOS/comments/n7yo7u

Is it possible to have a locked bootloader and root simultaneously?

I was wondering if there is a way to disable the warning screen or relock the bootloader while keeping the root and recovery.
Everytime i try it it say it can no longer find a valid operating system.

plain and simple, not there is no way for our phones. if your bootloader is unlocked, the warning screen will always show and your bootloader must be unlocked in order for magisk to run and root to be allowed.

Currently no. The reason is that to have root, you have to have a patched boot image, and to have a patched boot image, you need to be able to have an unlocked bootloader to allow flashing of /boot from recovery. "Locked" rooting would involve an exploit that would undoubtedly get fixed quickly. Also, keep in mind that the Pixel 2/XL do not have dedicated recovery partitions, but that recovery itself also resides in /boot.

Lock/Unlock boot loader?

Can we re-lock the boot loader on Pixel devices if the device is rooted and modded with custom boot and recovery partitions? I heard that it will brick the device when you try to re-lock the boot loader.
Also what if recovery partition ever gets corrupted and a user never had enabled OEM unlocking for the boot loader in the developer option as set as default, and the boot loader is locked as is, user can'f flash the factory images and /or full OTA from ADB.

I'm no expert but from what I've read 'Never relock the bootloader unless you are 10000% sure it's full stuck' and if I remember correctly there is no recovery partition on A/B slot builds which is why a brick is a non recoverable scenario (check that out just in case I'm wrong)
I've unlocked my bootloader and it ain't getting relocked after reading through heaps of bricked pixel threads, best to be safe than bricked.

Yep @junglism93 is right, only re-lock bootloader if you are 100% stock and unrooted to avoid bricks. Also Pixel doesn't have a recovery partition, everything happens in the boot partition, that means that in case of problems if you don't want to reflash the whole factory image (which needs unlocked bootloader), you can just reflash boot.img on slot-a and slot-b (which needs unlocked bootloader anyway).
I unlocked my bootloader straight after the unboxing and I can tell it's like a life saviour, if any problem occurs you can always solve it with an unlocked bootloader.

TENN3R said:
Yep @junglism93 is right, only re-lock bootloader if you are 100% stock and unrooted to avoid bricks. Also Pixel doesn't have a recovery partition, everything happens in the boot partition, that means that in case of problems if you don't want to reflash the whole factory image (which needs unlocked bootloader), you can just reflash boot.img on slot-a and slot-b (which needs unlocked bootloader anyway).
I unlocked my bootloader straight after the unboxing and I can tell it's like a life saviour, if any problem occurs you can always solve it with an unlocked bootloader.
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That seems like a crazy partition scheme on the device. I can't stand that dreaded unlock screen at the startup. plus you never know for sure if that OEM unlock switch in the developer menu will stay enabled all the time and not accidentally get disabled after modding your device so you're just having a very vulnerable device if it is modded...eh?
I wonder if there is a pure Android device which does not have such restrictions and/or actually comes pre-rooted?

Lock Bootloader with TWRP and custom ROM?

Is it possible to lock the bootloader with TWRP and a custom ROM installed and still use the device? Can I still flash ROMs in TWRP without hard/soft bricking my POCO?

Ungeskriptet said:
Is it possible to lock the bootloader with TWRP and a custom ROM installed and still us the device? Can I still flash ROMs in TWRP without hard/soft bricking my POCO?
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Short Answer: No it's not feasible to do that, reason behind that is AVB 2.0 (Android Verified Boot). It checkes for a pre-existing hash of all paritions signed by the OEM key (in this case Xiaomi), If there are conflicts found and Bootloader is in Locked state, The result would be a Fatal Error and would skip booting The OS to go to repair mode (aka EDL mode), which you can access in Xiaomi devices only if you have a verified EDL account.
Besides, even if you modify the Bootloader Binery or signed the twrp.img with the oem key (which you don't have access to), you wouldn't be able to flash anything anyway, since the device would consider any modifications after that a fatal error as well and won't boot.
Long Answer: read up on the follwing topics:
1- Android verified boot https://android.googlesource.com/platform/external/avb/+/master/README.md
2- FROST attack on unlocked bootloader (The reason android implemented avb) https://www.cs1.tf.fau.de/research/system-security-group/frost/

How do i recover the imei after unlocking the bootloader?

Hello again! I have a problem, i have the original firmware and the tool to flash it in case anything goes wrong (MTK Client), so i unlocked the bootloader, the problem is that when you unlock the bootloader, the baseband says (020null) and imei is unknown. I tried to restore my own nvcfg, nvram and nvdata to no luck, when I lock the bootloader, they appear again without flashing anything. So there must be something in the system that checks if you have the bootloader locked or not... I want to know how to disable it because I want to have root (I have rooted it with no issues, but i want my imei you know), i thought init.rc may have something to do with it, here is it (https://gist.github.com/ThePinkLyna/a43e65572896a57af2624610f74d00f2).
By the way my phone is an Alcatel 5007G, MTK 6762. Any ideas in where could be the block? The bootloader? An script in the system? There must be a way, right?

Re-lock the bootloader.
Android can get rooted without having the bootloader got unlocked before.
It's the Android kernel that checks if bootloader is locked or not.

xXx yYy said:
Re-lock the bootloader.
Android can get rooted without having the bootloader got unlocked before.
It's the Android kernel that checks if bootloader is locked or not.
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Click to collapse
How to get root without unlocking the bootloader? Because if i patch boot.img to use with magisk, then it goes into red state because secure boot. I know, the last thing you said, but i was talking about the system, there must be something which checks if the bootloader is unlocked or not and if its unlocked then it blocks the imei, i doubt android does that by default.

well, not answer to your original question, however try bootless-root method. but read warnings about limitations on locked bootloader (do not modify boot, system, ...)

TheAndrew579 said:
How to get root without unlocking the bootloader? Because if i patch boot.img to use with magisk, then it goes into red state because secure boot. I know, the last thing you said, but i was talking about the system, there must be something which checks if the bootloader is unlocked or not and if its unlocked then it blocks the imei, i doubt android does that by default.
Click to expand...
Click to collapse
You can doubt all, it's on you. Also take note that
1. every Android device comes shipped with a recovery partition by default,
2. you can't use a Custom Recovery like TWRP to restore lost IMEI.

are you sure it's bootloader lock state and not Magisk? I have same issue with Redmi 6, when booted in Magisk from fastboot baseband is unknown. normal boot baseband reappear (nothing flashed)
my suspect is magisk mount overlay (have to dig more into)
https://github.com/topjohnwu/Magisk/issues/426
What Magisk version you tried?
xXx yYy > /dev/null

aIecxs said:
are you sure it's bootloader lock state and not Magisk? I have same issue with Redmi 6, when booted in Magisk from fastboot baseband is unknown. normal boot baseband reappear (nothing flashed)
my suspect is magisk mount overlay (have to dig more into)
https://github.com/topjohnwu/Magisk/issues/426
What Magisk version you tried?
xXx yYy > /dev/null
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Click to collapse
Its not Magisk, because the problem starts happening when i unlock the bootloader, when i unlock it (Without installing magisk or flashing anything), and androids appears again, i go to info and it says baseband = 020null and imei unknown, if i flash magisk, then i get root but still no imei.
Im talking about the original firmware, unlocked bootloader = no imei, when i lock it again after uninstalling magisk (By flashing the original boot.img) then the imei appears again.

aIecxs said:
well, not answer to your original question, however try bootless-root method. but read warnings about limitations on locked bootloader (do not modify boot, system, ...)
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Click to collapse
And my android security version is newer, so that method wont work, still, i want root so i can uninstall system apps, so an unlocked bootloader is a must, but how exactly if when i unlock it i lose the imei? Thats the problem

you don't need root to get rid of system apps. this will do it. be careful what you're doing, in case of bootloop the only way left is factory reset. do a backup before.
Code:
adb shell cmd package disable --user 0 <pkgname>
How to disable any pre-installed system app bloatware on Android without root
If you hate the bloatware or pre-installed apps on your Android smartphone, here's how to disable them even if Android doesn't normally let you.
www.xda-developers.com