mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-12-23 14:58:09 +00:00
109 lines
4.6 KiB
Markdown
109 lines
4.6 KiB
Markdown
# TREZOR Core Bootloader
|
|
|
|
TREZOR initialization in split into two stages. See [Memory Layout](memory.md) for info about in which sectors each stage is stored.
|
|
|
|
First stage (bootloader) is stored in write-protected area, which means it is non-upgradable.
|
|
Only second stage (loader) update is allowed.
|
|
|
|
## First Stage - Bootloader
|
|
|
|
First stage checks the integrity and signatures of the second stage and runs it if everything is OK.
|
|
|
|
If first stage bootloader finds a valid second stage loader image on the SD card (in raw format, no filesystem),
|
|
it will replace the internal second stage, allowing a second stage update via SD card.
|
|
|
|
## Second Stage - Loader
|
|
|
|
Second stage checks the integrity and signatures of the firmware and runs it if everything is OK.
|
|
|
|
If second stage loader detects a pressed finger on the display or there is no firmware loaded in the device,
|
|
it will start in a firmware update mode, allowing a firmware update via USB.
|
|
|
|
## Common notes
|
|
|
|
* Hash function used for computing data digest for signatures is BLAKE2s.
|
|
* Signature system is Ed25519 (allows combining signatures by multiple keys into one).
|
|
* All multibyte integer values are little endian.
|
|
* There is a tool called [firmwarectl](../tools/firmwarectl) which checks validity of the loader/firmware images including their headers.
|
|
|
|
## Loader Format
|
|
|
|
TREZOR Core (second stage) loader consists of 2 parts:
|
|
|
|
1. loader header
|
|
2. loader code
|
|
|
|
### Loader Header
|
|
|
|
Total length of loader header is always 256 bytes.
|
|
|
|
| offset | length | name | description |
|
|
|-------:|-------:|------|-------------|
|
|
| 0x0000 | 4 | magic | firmware magic `TRZL` |
|
|
| 0x0004 | 4 | hdrlen | length of the loader header |
|
|
| 0x0008 | 4 | expiry | valid until timestamp (0=infinity) |
|
|
| 0x000C | 4 | codelen | length of the loader code (without the header) |
|
|
| 0x0010 | 1 | vmajor | version (major) |
|
|
| 0x0011 | 1 | vminor | version (minor) |
|
|
| 0x0012 | 1 | vpatch | version (patch) |
|
|
| 0x0013 | 1 | vbuild | version (build) |
|
|
| 0x0014 | 171 | reserved | not used yet (zeroed) |
|
|
| 0x00BF | 1 | sigidx | SatoshiLabs signature indexes (bitmap) |
|
|
| 0x00C0 | 64 | sig | SatoshiLabs signature |
|
|
|
|
## Firmware Format
|
|
|
|
TREZOR Core firmware consists of 3 parts:
|
|
|
|
1. vendor header
|
|
2. firmware header
|
|
3. firmware code
|
|
|
|
### Vendor Header
|
|
|
|
Total length of vendor header is 84 + 32 * (number of pubkeys) + (length of vendor string) + (length of vendor image) bytes rounded up to the closest multiply of 256 bytes.
|
|
|
|
| offset | length | name | description |
|
|
|-------:|-------:|------|-------------|
|
|
| 0x0000 | 4 | magic | firmware magic `TRZV` |
|
|
| 0x0004 | 4 | hdrlen | length of the vendor header |
|
|
| 0x0008 | 4 | expiry | valid until timestamp (0=infinity) |
|
|
| 0x000C | 1 | vmajor | version (major) |
|
|
| 0x000D | 1 | vminor | version (minor) |
|
|
| 0x000E | 1 | vsig_m | number of signatures needed to run the firmware from this vendor |
|
|
| 0x000F | 1 | vsig_n | number of different pubkeys vendor provides for signing |
|
|
| 0x0010 | 32 | vpub1 | vendor pubkey 1 |
|
|
| ... | ... | ... | ... |
|
|
| ? | 32 | vpubn | vendor pubkey n |
|
|
| ? | 1 | vstr_len | vendor string length |
|
|
| ? | ? | vstr | vendor string |
|
|
| ? | 2 | vimg_len | vendor image length |
|
|
| ? | ? | vimg | vendor image (in [TOIf format](toif.md)) |
|
|
| ? | 1 | sigidx | SatoshiLabs signature indexes (bitmap) |
|
|
| ? | 64 | sig | SatoshiLabs signature |
|
|
|
|
### Firmware Header
|
|
|
|
Total length of firmware header is always 256 bytes.
|
|
|
|
| offset | length | name | description |
|
|
|-------:|-------:|------|-------------|
|
|
| 0x0000 | 4 | magic | firmware magic `TRZF` |
|
|
| 0x0004 | 4 | hdrlen | length of the firmware header |
|
|
| 0x0008 | 4 | expiry | valid until timestamp (0=infinity) |
|
|
| 0x000C | 4 | codelen | length of the firmware code (without the header) |
|
|
| 0x0010 | 1 | vmajor | version (major) |
|
|
| 0x0011 | 1 | vminor | version (minor) |
|
|
| 0x0012 | 1 | vpatch | version (patch) |
|
|
| 0x0013 | 1 | vbuild | version (build) |
|
|
| 0x0014 | 171 | reserved | not used yet (zeroed) |
|
|
| 0x00BF | 1 | sigidx | vendor signature indexes (bitmap) |
|
|
| 0x00C0 | 64 | sig | vendor signature |
|
|
|
|
## Various ideas
|
|
|
|
* Loader should be able to read vendor + firmware header and send info about FW to client in features message.
|
|
* Loader should not try to run firmware if there is not any.
|
|
* Storage wiping rule: Don't erase storage when old FW and new FW are signed using the same key set. Otherwise erase.
|
|
* Loader should send error to client when firmware update fails and allow client to try one more time. This prevents storage area erasure by accident.
|