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53 lines
2.0 KiB
Markdown
53 lines
2.0 KiB
Markdown
# Firmware update and device wipe
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This document describes under which circumstances the device gets wiped during a firmware
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update.
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## Trezor 1
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The device gets **wiped**:
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- If the firmware to be installed is unsigned.
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- If the present firmware is unsigned.
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- If the firmware to be installed has lower version than the current firmware's
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_fix_version_ [1].
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The device gets **wiped on every reboot**:
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- If the firmware's debug mode is turned on.
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## Trezor T
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In Trezor T this works a bit differently, we have introduced so-called vendors headers.
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Each firmware has its vendor header and this vendor header is signed by SatoshiLabs. The
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actual firmware is signed by the vendor header's key. That means that all firmwares are
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signed by _someone_ to be able to run on Trezor T.
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We currently have two vendors:
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1. SatoshiLabs
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2. UNSAFE DO NOT USE
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As the names suggest, the first one is the official SatoshiLabs vendor header and all
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public firmwares are signed with that. The second one is meant for generic audience; if
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you build firmware this vendor header is automatically applied and the firmware is signed
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with it (see `tools/headertool.py`).
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The device gets **wiped**:
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- If the firmware to be installed is from different vendor than the present firmware [2].
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- If the firmware to be installed has lower version than the current firmware's
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_fix_version_ [1].
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The device gets **wiped on every reboot**:
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- If the firmware's debug mode is turned on.
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----
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[1] Firmware contains a _fix_version_, which is the lowest version to which that
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particular firmware can be downgraded without wiping storage. This is typically used in
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case the internal storage format is changed. For example, in version 2.2.0, we have
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introduced Wipe Code, which introduced some changes to storage that the older firmwares
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(e.g. 2.1.8) would not understand. It can also be used to enforce security fixes.
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[2] The most common example is if you have a device with the official firmware
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(SatoshiLabs) and you install the unofficial (UNSIGNED) firmware -> the device gets
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wiped. Same thing vice versa.
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