[HTC One Max] DVS_Sokar:
Source [MENTION=617884]Koush[/MENTION] (Original Article)

Source [MENTION=1676777]HTCDev[/MENTION] (Original Article)

Bootloader Locking, Unlocking, S-On, S-Off - Questions and Answers

It seems this is confusion in the community about what S-OFF is and why it's needed on some phones but not others. I endevour to educate and explain why some HTC devices need S-OFF while others do not to Flash Roms and recovery images.

[Q] What does S-ON/S-OFF mean? Is it on all phones?

[A] This is Manufacturer specific to HTC branded devices ONLY. S-On and S-Off means Security On/Security Off. HTC devices are set to S-ON by default for a good reason. There are partitions such as hboot which controls access to all other partitions which if made fully accessible could compromise security and very possibly allow for irreversible changes that could render your device inoperable. For warranty and device support purposes alone it would be to your benefit to keep Security-ON. Another partition that is secured is the radio. It is not advisable to alter or customize the radio and most custom roms will not need to. The radios are fine tuned to the specific carrier(s) they are designed to support and with the specifications as prescribed by law. Moreover altering them may not only also cause irreparable damage to your device but it could very well interfere with the normal communications possibly affecting other devices.

[Q] What does Unlock mean in the bootloader flag?

[A] What is meant by unlocking the bootloader is that certain partitions are unlocked to provide write access without turning device security off for all partitions. Specifically: Kernel, system and recovery partitions are allowed to be modified. There are more partitions (e.g. the radio and hboot) but these are the minimal necessary to overwrite a default stock rom with a custom built Android based rom.

[Q] Then why do Devs ask for S-OFF when flashing a Rom?

[A] Some carriers lock down the ability to Unlocked the partitions. For example US customers of Verizon are unable to use HTCDev to unlock their devices to access the needed partitions for Custom Rom and Recovery writing. In this Case S-OFF fixes this issue but also unlocks ALL partitions for writing. A Verizon phone with S-OFF will have the ability to now write to the Recovery and Boot partitions.

Devs ask for S-OFF for multiple reasons:

1. So that Devices Restricted by HTCDev whom normally can't get write access to the Boot and Recovery Paritions can use there ROM

2. Because forum behavior made S-Off appear to be needed

3. Laziness and/or ignorance (not trying to be rude)

[Q] So do I really need S-OFF to install ROMS or Recovery Images?

[A] Yes, If you have a HTCDev Restricted Device which will not allow you to use a Unlock Token you will need to S-OFF in order to write to your boot/system/Recovery partitions. NO, if you have a devices that can be unlocked using HTCDev Token to Unlock your device.

[Q] So Unlocking my devices has nothing to do with S-ON/S-OFF?

[A] A tricky question. Yes Unlocking a None Carrier restricted device with HTC Dev has Nothing to do with the Security of the Device from the S-OFF/S-ON perspective. If your on a Carrier Restricted HTCDev devices (I.E. Verizon HTC One Max) then in order to Write to the Partitions you need to you will need to be S-OFF as that is the only way to Unlock the bootloader.

[Q] So why do I need to Change my Bootloader Flag to get some things working?

[A] The short answer is that some hardware in the HTC Phones are told to look into the Security Partition to determine if the phone is Locked or Unlocked for Development. As an example on the HTC One Max the Fingerprint Reader will be disabled if the Bootloader Flag is set to "Unlocked" but function if the Flag is Set to "Locked". When your Bootloader is Flagged "Locked" the partitions are not accessible and will prevent Recovery and Boot Partition Modifications.

[Q] What if I want to return my device for warranty work how can I return it to S-ON and Locked Status?

[A] You will need to find your Model Phones RUU and Restore your phone to it original stock state. The RUU is used to restore a device to its Factory State. See the Question below about S-ON.

[Q] I would like to know if its still possible to achieve s-on after you have turned it off specially using the Rumrunner tool as I am Verizon device?

[A] Consumers that use Rumrunner to S-OFF will have the option of turning Device Security ON again. This typically is not a deal breaker for Warranty repairs if you restore the device software (Recovery, Room) back to it's default stock state and flag the bootloader Locked again as some devices are shipped S-OFF. It has been accomplished on the HTC One by running a command in Fastboot mode.

HTC One users achieve S-ON again by running this command with fastboot. I have not yet confirmed it works on the HTC One Max. (Note: If you are trying to return to a out of the box state use your device's RUU after S-ON to restore the Recovery, Kernel and Rom to Stock with a Encrypted/Signed RUU then run the command below) (If you want to test and report back on the HTC One Max please let us know.

[Q] What is the difference between an Encrypted RUU vs Decrypted RUU?

[A] A Encrypted RUU is a RUU file that has been signed by HTC (Carrier or Country). Encrypted RUU's can be run on S-ON or S-OFF devices to restore the device. A Decrypted RUU is a RUU that has had the signature stripped(in case of JB or older RUU's) and these can be typically ONLY run on S-OFF Devices. (Be careful to use the RUU for your device as these are hardware specific)

In conclusion:

S-OFF/S-ON is conditional based on your HTC device and carrier restrictions. If you are not able to unlock your partitions with HTCDev due to Carrier restrictions or country restrictions then S-OFF is you alternative.

If you can unlock your phones bootloader then you can flash kernels, roms and recovery images with S-ON. S-OFF is ONLY needed on devices that want full Partition access and/or HTCDev will not allow to unlock.

Do you you have a question? Reply with your question on this thread about S-ON/S-OFF/Bootloader Security. NOTE: This is not a General Question Thread.

P.S.

Please remember that unlocking your bootloader may void all or parts of your warranty and your device may not function as intended by HTC. Unlocking the bootloader is for development purposes only. :p