Added ESP Unpacker #412
Added ESP Unpacker #412
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ofrak_core/ofrak/core/esp/app.py
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| def determine_chip(f: _TemporaryFileWrapper) -> str: | ||
| """ | ||
| Determines the chip type based on the firmware image. | ||
| :param f: A temporary file object containing the firmware image | ||
| :return: The chip name as a string, defaults to 'esp8266' if not determined | ||
| """ | ||
| extended_header = f.read(16) | ||
| if extended_header[-1] not in [0, 1]: | ||
| return "esp8266" | ||
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| chip_id = int.from_bytes(extended_header[4:5], "little") | ||
| for rom in [n for n in ROM_LIST if n.CHIP_NAME != "ESP8266"]: | ||
| if chip_id == rom.IMAGE_CHIP_ID: | ||
| return rom.CHIP_NAME.lower() | ||
| return "esp8266" |
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For type-checking purposes, this should probably return an enum instead of a string.
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Also, why use a temporary file wrapper instead of indexing into the data itself? All of the data is already stored in memory.
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Philosophically, there are a lot of child types here that we don't need to define.
To make an analogy: the OFRAK tar unpacker unpacks files, not tar blocks. We want to do the equivalent here and unpack only what will actually be semantically useful for further layers of unpacking or analysis. We don't necessarily need tagged children for each part of the file type, especially if those parts are metadata.
Unfortunately, this guiding philosophy isn't documented anywhere, so there isn't a way you could have known this before. Also if any of this is based on the Elf unpacker, that one deviates from this philosophy a bit.
4 participants
One sentence summary of this PR (This should go in the CHANGELOG!)
Added an ESP unpacker to support unpacking Espressif binaries.
Link to Related Issue(s)
#410
Please describe the changes in your request.
Added esp.py to ofrak_core/ofrak/core which contains multiple resource view for ESP binaries as well as identification and unpacking. Uses ESPTool.py for most of the work.
Anyone you think should look at this, specifically?
@rbs-jacob
There are multiple "TODO:"s located in the code, a few of which are notes for things I'm unsure about, and the rest are questions that I couldn't find answers to in the contribution guidelines.