fix(prover): deterministic blob layout tag + continuation tamper coverage#851
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fix(prover): deterministic blob layout tag + continuation tamper coverage#851diegokingston wants to merge 3 commits into
diegokingston wants to merge 3 commits into
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…e input for continuation verify Mirrors #782's monolithic mechanism for the continuation path: a caller (the recursion guest) can supply the DECODE preprocessed root and each touched data page's genesis root instead of the verifier recomputing them from the ELF, skipping the in-VM FFT + Merkle build. Supplied roots are used verbatim; the binding shifts to the consumer's recompute-and-compare of the folded identity, exactly like the monolithic path. verify_global's genesis-page classification (ELF-backed vs zero-init) is derived from ELF segment address ranges instead of materializing a full byte-level image when roots are supplied, since the real bytes are never read once a root covers that page. Page lookups are keyed by page number (page_base >> log2(page_size)) rather than the raw page-aligned address, since the low bits are always zero. verify_continuation keeps its existing signature (trustless recompute); verify_continuation_with_roots is the new supplied-roots entry point, and continuation_precomputed_commitments lets a caller derive the roots to supply for a given bundle.
Adapts continuation verification to the same in-place rkyv pattern verify_recursion_blob already uses for the monolithic path (#769): verify_epoch/verify_global take a StarkProofView slice (owned or archived) instead of an owned MultiProof/EpochProof, so the new guest entry point (verify_continuation_and_attest_blob, via verify_continuation_archived) reads every per-epoch/global STARK proof straight out of the archive. Only small per-epoch metadata (table counts, reg_fini, l2g_root, public output) is materialized - the (large) per-epoch/global proof data is never copied into an owned MultiProof just to verify it. Adds the continuation guest's wire format (ContinuationGuestInput, encode_continuation_guest_input) mirroring GuestInput's magic-prefixed rkyv layout, and verify_continuation_and_attest[_blob] mirroring verify_and_attest_blob's program_id fold. replay_transcript_phase_a/compute_expected_commit_bus_balance (owned) lose their last production caller to this refactor; deleted rather than kept as compatibility wrappers now that every caller (production and test) goes through the _view variants already introduced by #769.
…ion tamper coverage Stacked on #845, addressing review findings: - Reuse the first reserved prefix byte as a layout kind (RECURSION_INPUT_KIND_MONOLITHIC=0, KIND_CONTINUATION=1). Both blob verifiers now check it at the prefix stage via the new recursion_archive_bytes_for_kind, so a blob of the wrong layout is rejected deterministically instead of relying on the rkyv bytecheck happening to fail on a differently-shaped archive. Backwards compatible: pre-kind blobs have zeros there (= KIND_MONOLITHIC). - New tests: test_recursion_continuation_rejects_corrupted_commitment (continuation analog of the monolithic corrupted-commitment guard) and test_recursion_blob_kind_byte_discriminates_layouts (both directions + kind-byte tamper). - KEEP IN SYNC notes between verify_continuation_with_roots and verify_continuation_archived; note that owned verify_continuation_and_attest is the host-side symmetric counterpart. - docs/continuations_design.md: update the deleted compute_expected_commit_bus_balance reference to the _view variant.
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Summary
Stacked on #845 — fixes for the findings from its review:
RECURSION_INPUT_KIND_MONOLITHIC = 0,RECURSION_INPUT_KIND_CONTINUATION = 1). Both blob verifiers check it at the prefix stage via the newrecursion_archive_bytes_for_kind, so a blob of the wrong layout is rejected deterministically instead of relying on the rkyv bytecheck happening to fail on a differently-shaped archive. Backwards compatible: blobs encoded before this change have zeros there, which is exactlyKIND_MONOLITHIC.test_recursion_continuation_rejects_corrupted_commitment— the continuation analog of the monolithic corrupted-commitment guard: honest bundle + corrupted DECODE root →Ok(None).test_recursion_blob_kind_byte_discriminates_layouts— continuation blob rejected by the monolithic verifier and vice versa at the prefix stage, plus kind-byte tamper rejection.verify_continuation_with_rootsandverify_continuation_archived(the two must apply the same validation in the same order), and a doc note that ownedverify_continuation_and_attestis the host-side symmetric counterpart of the_blobentry point.docs/continuations_design.mdnow referencescompute_expected_commit_bus_balance_view(the owned variant was deleted in perf(prover): verify continuation proofs in place via rkyv #845).Test plan
cargo test -p lambda-vm-prover --lib recursion_smoke— 5 passed, 0 failed (includes both new tests; pre-existing monolithic + continuation blob tests unaffected)cargo clippy -p lambda-vm-prover --all-targets -- -D warnings— clean