]>
gitweb.ps.run Git - ouroboros-slides/blob - pres.md
title: Ourosboros Flash Reader
author: Patrick Schönberger
date: 16.07.2025
transition: none
revealjs-url: https://cdn.jsdelivr.net/npm/reveal.js@5.2.1
slideNumber: true
Structure
- Start with the problem
- Work our way to the solution step by step
The Problem
- How to access data on Shelly devices?
- Most Shelly devices are based on ESPs
- They don't contain usable data like logs
- They do contain user-identifiable data
##
- Extract the flash memory and read the data
- Do it read-only and document the process
- Existing solutions (esptool, mos) can modify memory
- They are very complex, and thus hard to modify
- What about a custom tool?
Talking to the ESP
- What is the bare minimum needed to talk to an ESP?
- Two modes: boot and run
- Serial pins are exposed on some Shelly devices and accessible on others
- In boot mode they can be used to communicate using a custom protocol
##
- What can we do with the protocol?
- Synchronize
- Write RAM, flash and registers
- Configure memory etc.
- On the ESP32 it can read flash, but not on the ESP8266, ESP32C3 or ESP32C6
- How do other tools read flash?
Reading Flash Memory
- We cannot directly read flash, but we can write RAM
- Write a program for the ESP, load it into RAM and run
- This is called the flash loader or stub loader
- Esptool uses two versions:
- Legacy C version
- New Rust version
##
- The C version is getting replaced but it is much simpler and it supports ESP8266
- We customize this version by removing write and erase commands
- This way we technically have write access until the flash loader is activated
- The extraction tool is small and contains no write or erase commands
Serial Protocol
Demo
cloc
##
```sh
$ cloc esp-flasher-stub/
Language files blank comment code
Rust 12 327 78 1863
Logos 14 32 0 249
YAML 3 34 12 214
Markdown 1 34 0 89
TOML 4 8 2 61
SUM: 34 435 92 2476
```
##
```sh
$ cloc esp-hal
Language files blank comment code
Rust 492 18739 26120 115809
Linker Script 51 499 1404 11315
Markdown 66 2014 12 5262
TOML 43 505 412 4481
Logos 44 229 15 1105
YAML 13 151 67 1054
Jinja Template 3 52 0 255
JSON 2 0 0 48
CSV 3 0 0 21
SVG 1 0 0 4
SUM: 718 22189 28030 139354
```
##
```sh
$ cloc esptool-legacy-flasher-stub/
Language files blank comment code
Linker Script 32 787 1188 18751
C 6 1284 636 7689
C/C++ Header 8 463 557 1687
make 1 36 33 130
YAML 4 19 0 114
Python 2 25 21 80
Markdown 3 58 0 76
Bourne Shell 2 9 8 23
TOML 1 1 0 20
Jinja Template 1 4 2 14
SUM: 60 2686 2445 28584
```
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