feat(xtest): cross-SDK coverage for root and segment integrity algorithms (DSPX-4703, DSPX-4736) - #594
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📝 WalkthroughWalkthroughThe change adds root and segment integrity algorithm configuration across SDK test drivers. It adds manifest integrity helpers, GMAC root rejection checks, segment algorithm round-trip tests, tamper tests, and Java ZIP64 compatibility detection. ChangesIntegrity algorithm validation
Estimated code review effort: 4 (Complex) | ~75 minutes Severity of issue fixed: High Suggested reviewers: Merge Risk: 🟡 Moderate · up to The GMAC-root security tests may be skipped for SDKs that support rejection on read but do not expose the encryption flag, leaving reader-side forgery protection insufficiently covered. This should be addressed before merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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In `@spec/DSPX-4703.md`:
- Line 17: Remove the stale unresolved-status statement from the investigation
note while preserving the confirmed, reproducible exploit status documented in
the later section. Ensure the document presents a single consistent status and
does not describe the issue as merely a hypothesis.
In `@xtest/test_integrity_algs.py`:
- Line 284: Update both round-trip assertions using filecmp.cmp in the integrity
tests to pass shallow=False, ensuring each comparison checks file contents
byte-for-byte rather than relying on metadata.
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…thms (DSPX-4703, DSPX-4736) Adds the xtest side of the GMAC-root finding: the feature gates the SDKs advertise against, a keyless forgery helper, and 17 cases that exercise both the legitimate integrity-algorithm choices and the attack they make possible. A segment's GMAC hash is the AES-GCM tag the cipher just produced under the DEK over exactly those bytes, so it is a genuine MAC. The root signature covers the aggregate hash — every segment hash concatenated — which AES-GCM never processed, so the same trailing-16-bytes extraction yields a copy of the last segment hash: manifest data the attacker already holds. Since `rootSignature.alg` is read from the unauthenticated manifest, any HS256-rooted TDF can be downgraded onto that branch with no key at all, and the ordered segment list — the one thing only the root signature protects — stops being protected. AEAD tags bind no index, order, or count. Two feature gates, deliberately separate so the security repro can be forced on by itself with XT_FORCE_SUPPORTS: - `integrity_algs` (DSPX-4736) — the encrypt CLI takes `--segment-integrity-algorithm`. - `gmac_root_rejected` (DSPX-4703) — it also takes `--root-integrity-algorithm`, so `gmac` can be attempted and refused, and the reader rejects a manifest declaring a GMAC root in any casing. Each SDK shim grows `XT_WITH_ROOT_INTEGRITY_ALG` / `XT_WITH_SEGMENT_INTEGRITY_ALG`, passed only when a test asks for one so builds without the flags keep working. The fixture cache key includes both algorithms — without that, two callers differing only in integrity algorithm would silently share one ciphertext. `tdfs.py` gains the forgery primitives: `aggregate_hash`, `forge_gmac_root_signature` (mirroring `forgeGMACRootSignature` in platform's `tdf_root_signature_test.go`, including the 4.2.2 hex wrapper), `decode_integrity_value`, `is_legacy_manifest`, and `encrypted_segment_sizes` — the last because web-sdk omits `encryptedSegmentSize` when it matches the manifest default, so a caller slicing the payload cannot read the field directly. `test_integrity_algs.py` covers round-trips under GMAC and HS256 segments, the defaults, payload tampering, an accepted HS256 root and a refused GMAC root on encrypt, then the exploit: a forged GMAC root with segments intact, truncated, reordered, and repeated, plus the four casings of `GMAC`. Controls sit alongside each — an untouched file round-trips, and the same tampering without the forgery is caught — so a green run cannot come from decrypt failing for unrelated reasons. `test_tdfs.py`'s manifest validators stop accepting a 16-byte root signature: a GMAC root is a malformed container, not a variant to accommodate. `segmentHashAlg: GMAC` stays accepted. The empty-string case moves off the GMAC arm and onto HS256, matching what the readers actually default to. `test_tdfs_units.py` adds 7 cases pinning the helpers themselves — that the forgery is the trailing 16 bytes of the aggregate, that segment hashes are base64-decoded exactly once, that legacy containers hex-encode first, that casing survives, and that too short an aggregate raises. ruff check, ruff format, and pyright are clean; 289 tests collect and the 15 offline unit tests pass. Signed-off-by: Dave Mihalcik <dmihalcik@virtru.com>
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Review follow-ups on the DSPX-4703/DSPX-4736 coverage. Add a second positive control that pushes an untouched file through both update_payload and update_manifest and requires it to still decrypt. Every tamper case reaches the reader through that rewrite, so a rewrite that mangles the container would satisfy each "must fail" assertion for the wrong reason. Today the exploit cases disprove that incidentally -- an unfixed reader accepts the rewritten files -- but that evidence disappears once every SDK rejects them. The control failed immediately for web-sdk, which is the point: pydantic re-emitted "encryptedSegmentSize": null and "segmentSize": null on segments where web-sdk had omitted them, and its reader falls back to encryptedSegmentSizeDefault only when the field is absent, not when it is null. It died with "Failed to fetch entire segment" before reaching any integrity check. Dump with exclude_unset so the rewrite carries only what the original manifest said plus whatever the change touched. Screen decrypt failures in assert_decrypt_fails against a list of infrastructure-failure markers. A non-zero exit alone does not separate "the forgery was caught" from "KAS was unreachable", and both arrive as the same exception. The markers are observed from the CLIs rather than guessed. Also use [[ ]] in the two new cli.sh conditionals for go and java, matching js and clearing four sonarcloud shelldre:S7688 findings, and pass shallow=False to the two filecmp.cmp calls that were missing it.
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Inline comments:
In `@xtest/sdk/go/cli.sh`:
- Around line 99-105: Add a reader-specific capability check for
gmac_root_rejected in the SDK.supports implementation, separate from the
encryption help check, so decrypt_sdk tests do not depend on writer-option
support. Apply the corresponding change in xtest/sdk/go/cli.sh lines 99-105,
xtest/sdk/java/cli.sh lines 128-134, and xtest/sdk/js/cli.sh lines 113-119,
using each shim’s reader/decrypt help path while preserving XT_FORCE_SUPPORTS
behavior.
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…writer flag The exploit cases gated on `gmac_root_rejected`, which every shim answered by grepping `encrypt --help` for `--root-integrity-algorithm`. That flag is the *writer* half, and it ships in DSPX-4736 -- one commit below the reader fix in platform, java-sdk and web-sdk. So the gate was wrong in both directions: a build with 4736 but not 4703 advertises a reader fix it does not have and turns all six cases red, and a reader fixed without the writer flag skips silently, which is the vacuous green this module exists to prevent. There is nothing better to ask. Root-signature validation needs the unwrapped payload key, so it runs after the KAS rewrap and adds no flag, subcommand or version field a `cli.sh supports` probe can reach. Instead forge one root per reader per session and see whether it is refused. No version numbers to maintain, correct under every release ordering. - `gmac_root_rejected` -> `gmac_root_option` for what the shims actually probe; the two writer tests keep using it. - `gmac_root_rejected` stays as a force-only feature that every shim answers no to, so `XT_FORCE_SUPPORTS=gmac_root_rejected` still produces a red repro against a vulnerable build instead of a skip. - `decrypt_failure` split out of `assert_decrypt_fails` so the probe reuses the infra-failure screening and a flaky KAS cannot cache a reader as vulnerable for the rest of the session. go@main: 7 passed, 14 skipped (6 exploit cases now skip on the observed reason). go@pr-4030: 21 passed -- previously 2 of those skipped because otdfctl carries no --root-integrity-algorithm. XT_FORCE_SUPPORTS against go@main: 6 failed, 7 passed.
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Merged most of this in #595. Can re-investigate if we want to support HS256 for segment hashes |
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## Summary ### The bug A ZTDF's root signature is the only thing that authenticates the manifest's **ordered list** of segment hashes. AES-GCM tags bind a segment's own bytes and say nothing about its index, its neighbours, or how many segments exist — so segment-level integrity structurally cannot notice a truncated, reordered, or duplicated segment list. One signature routine served both jobs. For a **segment**, "GMAC" correctly means reading back the AES-GCM tag the cipher just computed over that segment's ciphertext. For the **root** it means nothing: the aggregate hash never passes through AES-GCM, so there is no tag to recover, and the code returned a copy of the trailing bytes of its own input — the last segment hash. Manifest data compared against manifest data, with the payload key never used. ### Why this is not opt-in The algorithm was read from `rootSignature.alg` in the manifest, which is unauthenticated, and unknown values were *coerced* to HS256 rather than rejected. So an attacker **with no key** could take any HS256-rooted TDF, rewrite the root to `"GMAC"` with a signature copied from the last segment hash, and then truncate, reorder, or duplicate segments — with the file still verifying. ### The fix * Split the routine into `segmentIntegrity` (HS256 or GMAC) and `rootIntegrity` (**HS256 only**), so tag extraction can no longer be pointed at a non-AEAD input. * `rootIntegrityAlgorithmFromManifest` resolves the root algorithm against an allowlist and throws `SDK.RootSignatureValidationException` for anything else, instead of coercing. * `segmentIntegrityAlgorithmFromManifest` allows both algorithms, because both are meaningful in that position, but still refuses an unrecognised name rather than defaulting it. A GMAC segment hash proves nothing on its own; what makes it trustworthy is that it is bracketed by two keyed checks — the HS256 root signature over the whole hash list, validated in `loadTDF` before any payload is read, and the real AES-GCM tag check under the payload key at decrypt time. The root has neither backstop, which is why the asymmetry between the two positions is structural rather than stylistic. * `createTDF` validates both configured algorithms before writing a byte, so the SDK cannot emit a file it would refuse to read, and cannot leave a partial TDF behind on a bad config. ### On the guard inside `rootIntegrity` `rootIntegrity` validates its own argument even though `createTDF` and the manifest resolver have both already checked. That is deliberate: the check is what makes the function safe to call, so it belongs with the function rather than only at today's call sites. It is genuinely redundant today, though, and the mutation results below say so plainly — with the resolver in place, a GMAC root cannot reach `rootIntegrity` through any public entry point. It is defence against a future edit, not against a current input. Because nothing else exercises it, this PR adds tests that call the guards directly; without those, a regression that reintroduced tag extraction inside `rootIntegrity` would leave the entire suite green. The two guards throw `IllegalArgumentException` rather than `SDK.TamperException`, matching how the config layer already reports bad caller-supplied values (`Config.withSegmentSize`). On a read they are unreachable, so if one ever does fire it means a bug in `TDF`, not a hostile file — it should escape loudly rather than arrive at callers wearing an exception type they routinely catch. ## Compatibility **No well-formed file is affected.** Every golden TDF in the cross-SDK corpus is `rootSignature.alg = "HS256"` with `segmentHashAlg = "GMAC"`. Nothing in the ecosystem emits a GMAC root: * **Go SDK** — uses position-specific types. `RootIntegrityAlg` admits only `RootHS256`; the GMAC constant is deprecated there and annotated as not a legal root algorithm. * **JS SDK** — `type RootIntegrityAlgorithm = 'HS256'`, so it is not expressible. * **Java SDK** — `Config` has never exposed a setter for the root algorithm, and `newTDFConfig` defaults it to HS256. The one way to have produced such a file is a caller who reached past the builder and assigned `TDFConfig.integrityAlgorithm = GMAC` on the public field. Those callers now get an `IllegalArgumentException` from `createTDF` instead of silently writing an unverifiable file. **There is no escape hatch, by design** — no flag, no compatibility mode, no target-mode exemption. A file this rejects is one no honest writer produces, and accepting it would restore the vulnerability for every reader. Anyone holding such a file must re-encrypt it. The legacy hex-encoded root path is still supported, and is covered by a test that confirms it did not become a way around the allowlist. ## Test plan ```bash mvn -q compiler:compile compiler:testCompile -pl sdk,cmdline mvn -q surefire:test -pl sdk # 261 tests, 0 failures, 8 skipped mvn -q surefire:test -pl cmdline # 13 tests, 0 failures ``` > Note: `mvn test` runs `generateSources`, which shells out to `buf` against the BSR and is rate-limited. Invoking the plugin goals directly, as above, skips that phase. Note also that `-pl sdk` on a *lifecycle phase* trips the `ReactorModuleConvergence` enforcer rule, since the parent is then outside the reactor; direct goal invocation avoids that too. `TDFRootSignatureTest`: **30 tests, 0 failures**, in two groups. **25 behavioural tests** drive the public API end to end — truncation, reordering, GMAC in several casings, an unknown root algorithm that must not be coerced, an unknown segment algorithm, a legacy hex-encoded GMAC root, a config-level GMAC root, plus controls that must keep passing for reasons unrelated to this change. **5 guard tests** call `rootIntegrity` / `segmentIntegrity` and their argument checks directly. These reference methods this PR introduces, so unlike the group above they cannot be run against `main`. ### Verified by reverting, and by mutation With this commit's `TDF.java` reverted to `main` and the test file otherwise untouched, the 25 behavioural tests **compile unmodified** and **9 fail** across 7 methods — the vulnerability is live and reproducible, and the tests are not merely asserting the shape of the new code: ``` gmacRootIsRejected gmacRootIsRejectedInAnyCasing[1..3] gmacDowngradeWithTruncatedSegmentsIsRejected gmacDowngradeWithReorderedSegmentsIsRejected unknownRootAlgorithmIsRejected unknownSegmentAlgorithmIsRejected # wrong type on main: SegmentSignatureMismatch, by coercion accident createTdfRefusesAGmacRootSetDirectlyOnTheConfig ``` The other 16 stay green, so the suite is discriminating rather than strict. Mutating one layer at a time locates which check is load-bearing: | variant | `TDFRootSignatureTest` | | --- | --- | | baseline | 30 pass | | resolver coerces unknown → HS256, `rootIntegrity` intact | **3 fail** | | `rootIntegrity` accepts GMAC again, resolver intact | **1 fail** (the new direct guard test) | | both reverted (`main`) | **9 of 25 fail** | The resolver is the layer that actually stops a hostile file. The `rootIntegrity` guard is caught only by the test written for it — which is the argument for having written it, and an honest statement of what that check is and is not doing. ## Related * Cross-SDK coverage and the attack corpus: `spec/DSPX-4703.md` in `opentdf/tests`, and opentdf/tests#594 * Write-side controls: #400 (DSPX-4736) — independent, no longer stacked; this PR targets `main` <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **Bug Fixes** * Strengthened integrity verification for encrypted segments and TDF root signatures. * Rejected unknown, missing, unsupported, or invalid integrity algorithm declarations. * Prevented GMAC-based root-signature downgrades during TDF creation and verification. * Improved detection of modified or tampered TDF content, including legacy signature formats. * Added validation for configured integrity algorithms while preserving support for valid HS256 root signatures. <!-- end of auto-generated comment: release notes by coderabbit.ai --> Signed-off-by: Dave Mihalcik <dmihalcik@virtru.com>
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What
The xtest side of the GMAC-root finding: the feature gates the SDKs advertise
against, a keyless forgery helper, and 17 cross-SDK cases covering both the
legitimate integrity-algorithm choices and the attack they make possible.
Why
A ZTDF records two integrity algorithms and only one of them can be
GMAC.A segment's GMAC hash is the AES-GCM tag the cipher just produced under the
DEK over exactly those bytes — a genuine MAC. The root signature covers the
aggregate hash, every segment hash concatenated, which AES-GCM never
processed. Applying the same trailing-16-bytes extraction there returns a copy
of the last segment hash: manifest data the attacker already holds.
rootSignature.algis read from the manifest, which is unauthenticated untilthe root signature validates. So any HS256-rooted TDF can be downgraded onto
the GMAC branch with no key at all, and the ordered segment list — the one
thing only the root signature protects — stops being protected. AEAD tags bind
no index, order, or count: each says "this ciphertext is intact," never "this
is segment 3 of 7."
Feature gates
Two, deliberately separate so the security repro can be forced on by itself
with
XT_FORCE_SUPPORTS:integrity_algs--segment-integrity-algorithmgmac_root_rejected--root-integrity-algorithm, sogmaccan be attempted and refused — and the reader rejects a GMAC root in any casingEach SDK shim (
sdk/{go,java,js}/cli.sh) growsXT_WITH_ROOT_INTEGRITY_ALGand
XT_WITH_SEGMENT_INTEGRITY_ALG, passed only when a test asks for one soSDK builds without the flags keep working.
test_sdk_commands.pypins boththe pass-through and the omission.
The fixture cache key now includes both algorithms. Without that, two callers
differing only in integrity algorithm would silently share the first
ciphertext, and half the matrix would be testing the wrong file.
Helpers (
tdfs.py)aggregate_hash— the bytes a reader signs at the root. Base64-decoded butnot hex-decoded even for a legacy container, because that is exactly how
every SDK builds the buffer.
forge_gmac_root_signature— the keyless rewrite, mirroringforgeGMACRootSignaturein platform'stdf_root_signature_test.go,including the 4.2.2 hex wrapper.
decode_integrity_value,is_legacy_manifestencrypted_segment_sizes— web-sdk omitsencryptedSegmentSizewhen itequals the manifest default, so a caller slicing
0.payloadinto segmentscan't read the field directly.
Tests
test_integrity_algs.py(new, 17 cases):chunky/multi-segment variant, the defaults, payload tampering still caught
under both, an HS256 root accepted on encrypt and a GMAC root refused.
reordered, and repeated, plus all four casings of
GMAC.tampering without the forgery is caught. A green run can't come from
decrypt failing for unrelated reasons.
test_tdfs.py— the manifest validators stop accepting a 16-byte rootsignature; a GMAC root is a malformed container, not a variant to accommodate.
segmentHashAlg: GMACstays accepted. The empty-string case moves off theGMAC arm onto HS256, matching what the readers actually default to.
test_tdfs_units.py— 7 offline cases pinning the helpers: the forgery is thetrailing 16 bytes of the aggregate, segment hashes are base64-decoded exactly
once, legacy containers hex-encode first, casing survives, too short an
aggregate raises.
How to test
All clean; 289 tests collect.
The full matrix needs the SDK PRs, which are stacked two-deep per SDK:
The split is what makes this suite useful as a measurement: with only the
first PR of each stack merged, the SDKs advertise
integrity_algsbut notgmac_root_rejected, so the exploit cases can be run against known-vulnerablereaders to confirm they genuinely fail. Each SDK's unit-level baseline is
recorded in its own fix PR (platform 7 failures, java 8/29, web-sdk 9/23,
controls green in all three).
DSPX-4703, DSPX-4736
Summary by CodeRabbit
New Features
Bug Fixes
Tests