fix(tee): check the TSM provider before reading outblob

[Susanpdl]

The non-blocking follow-up from your review of #86.

What was wrong

collect_report read outblob and then checked provider:

(entry / "inblob").write_bytes(report_data)
outblob = (entry / "outblob").read_bytes()
provider = (entry / "provider").read_text().strip()

if provider != expect_provider:
    raise AttestationFailed(...)

Reading outblob is what makes the platform generate and sign the report, so on a mismatched provider the hardware signed a report over the caller's binding and it was then thrown away. As you said, nothing is returned and the entry is removed, so this is not a disclosure. It is asking the hardware to sign something no one can use, and the check costs nothing where it belongs.

The provider check now gates the read. The two failures also read differently now, since they are different problems: an entry that names no provider cannot be trusted to be the right platform, and a matching provider that returns nothing is a collection failure.

Making it stick

The interesting part was that the old test could not have caught this, because the fake configfs tree wrote outblob when inblob was written. That made the read a plain file read with no observable effect, which is exactly the property that matters here inverted.

The fake now generates the report when outblob is read, which is the kernel's actual sequence, and records which attributes were read. test_collect_report_refuses_the_wrong_platform then asserts reads == [], so a mismatch means the report was never produced rather than produced and discarded.

I checked the test fails against the old ordering rather than passing vacuously: restoring the previous sequence fails two tests, including that one.

Testing

429 passed, 3 skipped. ruff check, ruff format --check, mypy and bandit all clean.

[codecov-commenter]

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[imran-siddique]

Reviewed the provider-before-outblob ordering and the adversarial configfs test. The wrong-provider path now performs zero outblob reads, avoiding unnecessary hardware report generation. Hosted tests, CodeQL, analysis, governance, Windows/Linux matrices, Ruff, mypy, and bandit are green. Approving.