fix(sdk): map ReadAt plaintext offsets from cumulative segment sizes - #3933
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ChangesNon-uniform segment reading
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to This change improves variable-sized TDF segment reads, but its new negative-size test references unavailable symbols and will fail to compile until it expects the implemented ErrSegSizeMismatch behavior. Poem
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The zip writer only switched to ZIP64 once a value exceeded 4 GiB, but java-sdk reads the 32-bit central-directory fields as signed, so any container in the 2-4 GiB band was written as zip32 with a value that deployed Java clients read back as negative. Switch at 2 GiB (math.MaxInt32) to match java-sdk's MAX_NON_ZIP64_VALUE, apply the same rule to the local-header offset, and make the threshold injectable so the ZIP64 path can be exercised in a unit test without allocating gigabytes. The reader's ZIP64 extra-field parser assumed the field was first in the extra area and that all three values were always present. APPNOTE 4.5.3 says each value appears only when its central-directory counterpart holds the 0xFFFFFFFF sentinel, in the order original size, compressed size, local header offset. Walk the whole extra area, skip foreign tags, and read only the values the sentinels advertise. Also: detect ZIP64 from any of the three EOCD sentinel fields rather than the offset alone, honour a per-entry ZIP64 extra field in a zip32 EOCD archive, widen the central-directory cursor arithmetic to uint64 so a long name plus extra plus comment cannot wrap at uint16, include the file-comment length in that cursor, and return an explicit error instead of silently truncating when a value will not fit a 32-bit field. segmentSize and encryptedSegmentSize are optional per-segment overrides: manifest.schema.json requires only the integrityInformation defaults, and web-sdk omits the per-segment keys whenever they equal the default, so every web-sdk container over one segment failed to decrypt in go-sdk. Fall back to the manifest defaults in the payload-size computation, WriteTo and ReadAt. Rebased onto #3933 (map ReadAt plaintext offsets from cumulative segment sizes), which rewrote ReadAt's segment lookup from a uniform DefaultSegmentSize stride to a walk over each segment's actual plaintext/ciphertext size -- necessary for the non-uniform segments sdk/experimental/tdf can emit, and something this change's original ReadAt fix did not attempt. Reconciling the two surfaced a further bug: resolveSegmentSizes treated a per-segment size of 0 as "omitted, use the default" independently for Size and EncryptedSize, but JSON can't distinguish an omitted key from an explicit 0, and go-sdk's own CreateTDF already writes segmentSize: 0 for the sole segment of an empty-payload TDF (no omitempty on the field). That made an empty TDF round-trip to the wrong payloadSize. resolveSegmentSizes now resolves EncryptedSize first -- its zero value is never ambiguous, since ciphertext can never legitimately be zero bytes -- and disambiguates a zero Size by comparing the resolved EncryptedSize against DefaultEncryptedSegSize rather than assuming Size and EncryptedSize are only ever omitted together. Checking go-sdk, java-sdk and web-sdk's actual manifest-writing source confirmed go-sdk and java-sdk always set both fields together (so the joint-zero assumption happened to hold for them), but web-sdk's lib/tdf3/src/tdf.ts decides whether to omit segmentSize and encryptedSegmentSize with two independent equals-the-default comparisons, not one joint check -- so the joint-zero-only version would have mis-resolved a segment where only one of the two happened to be omitted. The corrected comparison needs no assumption about the cipher's per-segment overhead (nonce/tag size stays out of manifest.go entirely): the overhead is constant across every segment in one manifest, so if the resolved EncryptedSize equals its default, the plaintext size must too, regardless of what that overhead number actually is. Also gives calculateSignature's too-short-ciphertext-for-GMAC error (previously a bare, unclassified error) a proper ErrTampered-wrapped sentinel, consistent with the rest of this file's integrity failures. Verified against opentdf/tests' DSPX-4592-java-underflow branch (adds test_tdfs.py::test_chunky_roundtrip, a 5 MiB round-trip that forces a full-default-sized segment): with platform-ref and otdfctl-ref both pointed at this branch and XT_FORCE_SUPPORTS=chunky, js-encrypt -> go-decrypt passes (js omits per-segment sizes on the full-sized segment; go now defaults them back). The one remaining failure in that run, js-encrypt -> java-decrypt, is java-sdk's own pre-existing GMAC-on-empty- segment bug (DSPX-4589), unrelated to this change. Supersedes #3967, which is left open, unmodified, for reference. Signed-off-by: Dave Mihalcik <dmihalcik@virtru.com>
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segmentSize and encryptedSegmentSize are optional per-segment overrides: manifest.schema.json requires only the integrityInformation defaults, and web-sdk omits the per-segment keys whenever they equal the default, so every web-sdk container over one segment failed to decrypt in go-sdk. Fall back to the manifest defaults in the payload-size computation, WriteTo and ReadAt. Rebased onto #3933 (map ReadAt plaintext offsets from cumulative segment sizes), which rewrote ReadAt's segment lookup from a uniform DefaultSegmentSize stride to a walk over each segment's actual plaintext/ciphertext size -- necessary for the non-uniform segments sdk/experimental/tdf can emit. Reconciling the two surfaced a further bug: resolveSegmentSizes treated a per-segment size of 0 as "omitted, use the default" independently for Size and EncryptedSize, but JSON can't distinguish an omitted key from an explicit 0, and go-sdk's own CreateTDF already writes segmentSize: 0 for the sole segment of an empty-payload TDF (no omitempty on the field). That made an empty TDF round-trip to the wrong payloadSize. resolveSegmentSizes now resolves EncryptedSize first -- its zero value is never ambiguous, since ciphertext can never legitimately be zero bytes -- and disambiguates a zero Size by comparing the resolved EncryptedSize against DefaultEncryptedSegSize rather than assuming Size and EncryptedSize are only ever omitted together. Checking go-sdk, java-sdk and web-sdk's actual manifest-writing source confirmed go-sdk and java-sdk always set both fields together (so a joint-zero assumption happened to hold for them), but web-sdk's lib/tdf3/src/tdf.ts decides whether to omit segmentSize and encryptedSegmentSize with two independent equals-the-default comparisons, not one joint check -- so a joint-zero- only version would have mis-resolved a segment where only one of the two happened to be omitted. The corrected comparison needs no assumption about the cipher's per-segment overhead (nonce/tag size stays out of manifest.go entirely): the overhead is constant across every segment in one manifest, so if the resolved EncryptedSize equals its default, the plaintext size must too, regardless of what that overhead number actually is. Also gives calculateSignature's too-short-ciphertext-for-GMAC error (previously a bare, unclassified error) a proper ErrTampered-wrapped sentinel, consistent with the rest of this file's integrity failures. Verified against opentdf/tests' DSPX-4592-java-underflow branch (adds test_tdfs.py::test_chunky_roundtrip, a 5 MiB round-trip that forces a full-default-sized segment): with platform-ref and otdfctl-ref both pointed at this branch and XT_FORCE_SUPPORTS=chunky, js-encrypt -> go-decrypt passes (js omits per-segment sizes on the full-sized segment; go now defaults them back). The one remaining failure in that run, js-encrypt -> java-decrypt, is java-sdk's own pre-existing GMAC-on-empty- segment bug (DSPX-4589), unrelated to this change. Note on #3933 standalone: without this fix, #3933's cumulative-walk ReadAt uses seg.Size directly, so an omitted (0) per-segment size stalls the plaintext cursor and desyncs the ciphertext offset for every segment after it. Reading a web-sdk multi-segment file then fails with a misleading "tamper detected: failed integrity check on segment hash" instead of main's current (also broken, but at least consistent) "fail to create gmac signature". #3933 should not be merged or relied on standalone for real multi-segment interop until this lands on top of it. The zip64/ZIP64-conformance findings originally bundled with this change (findings 1-6 of the DSPX-4590 investigation) now live in a separate PR stacked on top of this one, since they are independent of the segment- size defaulting fixed here. Signed-off-by: Dave Mihalcik <dmihalcik@virtru.com>
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Inline comments:
In `@sdk/tdf.go`:
- Around line 1083-1086: Validate every decrypted segment’s plaintext length
against seg.Size before using its extent, including prefix segments skipped by
the segEnd <= offset path and the corresponding later branch. Reject mismatches
before copying or advancing offsets, while preserving normal reads for valid
segments. Add tampering tests covering both over-declared and under-declared
prefix segments.
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Inline comments:
In `@sdk/tdf_readat_test.go`:
- Around line 244-247: Update the “negative” test case in the relevant test
table to expect ErrSegSizeMismatch instead of ErrSegSizeUnresolved, matching the
error returned by newNonUniformReader’s per-segment size validation.
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Reader.ReadAt derived every segment's plaintext extent from manifest.DefaultSegmentSize, assuming a uniform stride. The TDF manifest records a per-segment Size and does not require the segments to be equal sized, and sdk/experimental/tdf already emits variable-length segments. Against such a payload the uniform stride selects the wrong segment (wrong bytes returned, no error) or slices past the decrypted buffer. Walk manifest.Segments accumulating seg.Size instead, and return ErrSegSizeMismatch when a segment's declared Size disagrees with what it actually decrypts to rather than panicking on the slice. WriteTo already walked cumulative sizes; the two now agree. SDK.CreateTDF only ever emits uniform segments, so this is not reachable through it -- the new sweep over segment sizes 1/2/7/62/64 is regression coverage and passes before and after. The non-uniform tests build the archive directly on internal/zipstream and fail before this change. Peeled out of the DSPX-2604 stack; it stands on its own. Signed-off-by: David Mihalcik <dmihalcik@virtru.com>
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Proposed Changes
Reader.ReadAt derived every segment's plaintext extent from
manifest.DefaultSegmentSize, assuming a uniform stride. The TDF manifest
records a per-segment Size and does not require the segments to be equal
sized, and sdk/experimental/tdf already emits variable-length segments.
Against such a payload the uniform stride selects the wrong segment
(wrong bytes returned, no error) or slices past the decrypted buffer.
Walk manifest.Segments accumulating seg.Size instead. WriteTo already
walked cumulative sizes; the two now agree.
That promotes Segment.Size to sole control of the offset mapping, so
check it before trusting it. Nothing authenticates Size -- the root
signature aggregates only Segment.Hash -- and a manifest that understates
one segment shifts every plaintext offset after it, returning the wrong
bytes under a valid signature. AES-GCM frames each segment with a 12-byte
nonce and a 16-byte tag, so the plaintext size is pinned by the ciphertext
size: every segment now has to satisfy that relation, which is the
per-segment form of the check doPayloadKeyUnwrap already applies to the
manifest defaults. Segments the request skips over are checked too, since
their declared sizes still position everything that follows them.
SDK.CreateTDF only ever emits uniform segments, so the mapping bug is not
reachable through it. The non-uniform tests build the archive directly on
internal/zipstream and fail before this change.
Peeled out of the DSPX-2604 stack; it stands on its own.
Checklist
Testing Instructions
New coverage, all in
sdk/tdf_readat_test.go:TestReaderReadAtNonUniform/...Edges/TestReaderNonUniformSeekReadWriteTobuild the archive directly on
internal/zipstreamwith segment shapesCreateTDFcannot emit, and sweep every(offset, length)pair. These failbefore this change and pass after.
TestReaderReadAtDeclaredSizeMismatchtampers with a declaredSegment.Size(understated, overstated, and negative-with-overflow) and requires
ErrSegSizeMismatch. Understating the size of a segment the read skips overis the case that silently returned shifted plaintext.
Test_TDFReaderReadAtBoundariesandTest_TDFReaderMultiSegmentSeekReadWriteToprobe every segment boundary of agenuinely multi-segment TDF built through the ordinary
CreateTDF->LoadTDF-> key-unwrap path.The last two replace an earlier
tdf_test.gosweep over segment sizes1/2/7/62/64, which tested nothing:
WithSegmentSizeclamps up tominSegmentSize(16 KiB), so all five iterations built the samesingle-segment TDF and no interior boundary was ever crossed. The
replacements assert the segment shape they depend on so they cannot
degenerate the same way, and they no longer touch
tdf_test.go.The full DSPX-2604 stack — 20 PRs
mainmainmainmainmainmainmaindspx-2604-base-11= #3932 + #3934 + #3935dspx-2604-base-17= #3944 + #3945dspx-2604-base-19= #3947 + #3939Reviewable in parallel right now, since they sit directly on
mainand depend onnothing else: 01, 02, 04, 05, 06, 07, 08.
Why three PRs have a
dspx-2604-base-*base. A GitHub PR takes one base branch,but 11, 17 and 19 each build on more than one parent. The
base-*branches are emptymerge commits that exist only to join those parents so the PR diff shows exactly its
own change and nothing else. They contain no code, have no PR of their own, and go
away once their parents land — retarget the child onto
mainat that point.Wants a cross-SDK xtest run before merge: 15, 17 (and therefore 20), which touch
the KAS wire format, and 04, which tightens what the Go reader will accept from a
manifest another SDK wrote.
Red checks you may see are network flakes, not this stack. Four distinct ones hit
this batch and all clear on re-run:
golangci-lint config verifytiming out onhttps://golangci-lint.run/.../golangci.v2.8.jsonschema.json(fails the wholego (<module>)job and fail-fast cancels its siblings), the bats installer getting a 403,Docker Hub timing out on
keycloak/keycloak:26.4, andbufreporting "the serverhosted at that remote is unavailable" while the Java SDK generates sources. The
govulncheckstep also emits##[error]annotations against the go1.25.11 stdlib, butit is
continue-on-error: trueand never fails a job — 01 bumps the toolchain andclears those annotations.
Summary by CodeRabbit
Bug Fixes
Tests