[bugfix] DecodeQR: handle Compact SeedQR byte data that can be decoded to str

[kdmukai]

Description

Fixes #656

The bug

The QR decoder (decode_qr.py) starts by interpreting QR data as str as it tries to figure out the QR format that was just scanned (e.g. animated psbt, address to verify, SeedQR, etc). In most cases, Compact SeedQR byte data will fail the conversion to str (raises UnicodeDecodeError; all good, we expect that) and the code will carry on to its next step where it assumes the data is still in bytes format.

But in the edge cases where the Compact SeedQR byte data CAN be converted to str (e.g. "abandon" x11 + "about" as reported in #656), the successful conversion to str then runs into errors in the Compact SeedQR decoding: the data isn't bytes, it's str at this point, and so the byte manipulation code errors out. The error is caught and the decoder reports the Compact SeedQR as invalid (even though it IS actually valid).

The fix

This PR simply checks and ensures that the data is in bytes format before the Compact SeedQR processing begins.

TODO: Longer term, the conversion to str should be eliminated altogether. But that approach was NOT taken in this PR in order to minimize the impact of this PR and minimize the amount of testing needed.

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• Additional test case added with the Error reading Compact SeedQR generated by SeedSigner itself. #656 byte data as well as randomly generated 12- and 24-word entropy byte data that are able to pass the conversion to str.

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Testing

12-word Compact SeedQR that will fail with dev but succeed with this PR:

And a 24-word Compact SeedQR:

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This pull request is categorized as a:

• Bug fix

Checklist

• I’ve run pytest and made sure all unit tests pass before sumbitting the PR

If you modified or added functionality/workflow, did you add new unit tests?

• Yes

I have tested this PR on the following platforms/os:

• Raspberry Pi OS Manual Build
• SeedSigner OS on a Pi0/Pi0W board
• Other

[fedebuyito]

Hi, @kdmukai . Well tested below and passed, thank you Keith!

[kdmukai]

@fedebuyito as a sanity check, can you run the new test on your dev device:

pytest tests/test_seedqr.py::test_compact_seedqr_bytes_interpretable_as_str

(see the README in tests/ if you don't have pytest or other test suite dependencies installed)

[fedebuyito]

Good, it passed on both 3.10 and 3.12:

[kdmukai]

@fedebuyito that looks like it's running on your local dev machine. I want to see if you can run the test on your dev SeedSigner -- on the Pi Zero.

[fedebuyito]

I am sorry Keith, I just saw that img on Pi Zero is not this commit PR version. Yes NOW!

[jdlcdl]

ACK tested, this all worked for me at cf83ebe

• on Ubuntu Dev Desktop for automated tests
• on RPi02w with RaspiOS manual build for automated tests
• on RPi02w with RaspiOS manual build scanning 12w and 24w seeds (which confirmed to raise error on pi0 0.8.5-rc1)