ASiC-E verification has no completeness check: unlisted ZIP data files verify as valid

[stevehansen]

Problem

VerifyExtended iterates only the ASiCManifest's DataObjectReference elements. A data file that sits in the ZIP but is not referenced by the manifest is therefore:

• never hashed,
• never reported as a step, and
• does not prevent IsValid from being true.

Compounding it, ExtractAll walks ZIP entries (FindDataEntries) rather than the manifest, so it does return those unlisted files. A consumer that verifies a container, sees IsValid == true, and then calls ExtractAll will surface bytes that the proof of existence never covered — presented as though they were timestamped.

The listed files' proofs remain intact; this is not a break of the timestamp itself. The issue is that "valid container" currently says nothing about whether every file in it is covered.

Reproduction sketch

1. Create an ASiC-E container with file1.txt.
2. Add injected.txt to the ZIP without touching META-INF/ASiCManifest.xml.
3. Verify → IsValid == true, no step mentions injected.txt.
4. ExtractAll → returns both files.

Why this needs a decision, not just a patch

IsValid is the conjunction of every VerificationStep. Adding a completeness step means containers that verify today become invalid — including any third-party ASiC-E container that legitimately carries extra unreferenced entries. So the options differ in blast radius:

1. New failing step — strictest, but a breaking change for existing containers.
2. Passing-but-informational step — surfaces the fact without flipping IsValid; no break, weaker guarantee.
3. Report-only property on AsicVerifyResult (e.g. unlisted entry names) plus a documented caveat — no step, caller decides.
4. Fix ExtractAll only — have it return manifest-referenced files for ASiC-E, closing the dangerous half without touching the verdict.

Options 3 and 4 compose well and avoid the breaking change; option 1 is the strongest guarantee if a major-version bump is acceptable.

Tracking

• STRIDE.md T-9 (Tampering, score 6, status Open)
• Documented in docs/verification.md (gotchas) and docs/container.md (gotchas)

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