JANG BYUNGKUNandgensokyo-dev
21e0c580e7
* feat(il2cpp): read member names, string literals and metadata versions 24 and 27 Adds field, property, event and parameter names with their owners, managed string literals, and the version 24 and 27 header layouts to inspect_il2cpp_metadata, with filtered pages for the new collections. Member decoding yields between row batches like the other row readers. * fix(il2cpp): bound metadata expansion and query parameter owners * test(il2cpp): cover nonempty property and event tables --------- Co-authored-by: gensokyo-dev <gensokyo-dev@users.noreply.github.com>
249 lines
12 KiB
Markdown
249 lines
12 KiB
Markdown
# IL2CPP metadata
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`inspect_il2cpp_metadata` / `inspect-il2cpp-metadata` decodes one selected local
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Unity IL2CPP `global-metadata.dat` file and returns its assembly images, type
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definitions, methods and named members with their owners, plus managed string
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literals, by stable index, namespace, range and count,
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with the header sections and serialized index widths. It reads the file without
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running it and requires no Unity installation, IL2CPP binary, active target,
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Hopper, Ghidra or IDA.
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Metadata versions 24, 27, 29, 31 and 39 are supported. For example, Unity 2019.4.41f2
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wrote version 24, 2020.3.49f1 version 27, 2022.3.30f1
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wrote version 29, 2022.3.62f3 wrote 31 and 6000.4.2f1 wrote 39; other Unity
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releases that write these numbers have not been checked. Other versions are
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rejected as unsupported. Version 24 decoding covers the 264-byte header layout
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used by the cited Unity 2019.4 build; earlier 24.x layouts are not inferred from
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the version number and are refused when their header or records differ. The path
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must name a regular file; directories and symbolic links are rejected.
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## MCP
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MCP defaults to a compact summary and retains the complete decoded Evidence in
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the session. MCP requires an absolute filesystem path:
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```json
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{
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"name": "inspect_il2cpp_metadata",
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"arguments": {
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"path": "/artifacts/Data/Managed/Metadata/global-metadata.dat"
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}
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}
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```
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The summary retains the complete decoded Evidence in the session and returns a
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linked `inspect_analysis_view` overview: artifact identity, metadata version,
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index widths and `counts` (`sections`, `images`, `types`, `methods`,
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`nested_types`, `fields`, `properties`, `events`, `parameters` and
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`string_literals`) without rows. Use `normalized_result.parent_evidence_id` to page
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the original rows without reopening or decoding the file:
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```json
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{
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"source": {
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"kind": "retained-evidence",
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"evidence_id": "<parent_evidence_id>"
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},
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"view": {
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"kind": "il2cpp-metadata",
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"collection": "types",
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"offset": 0,
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"limit": 64
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}
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}
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```
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Collections are `sections`, `images`, `types`, `methods`, `fields`,
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`properties`, `events`, `parameters` and `string_literals`. Every returned row includes
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its source `index`, scoped by artifact SHA-256 and collection. All collections
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accept batch `indices` and `fields`; collections whose rows have a `name` also
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accept exact `names`. Types also accept `image_indices`, `namespaces` and
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`declaring_types`; methods, fields, properties and events accept
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`declaring_types`. Parameters accept exact `method_indices`, so a batch of
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method indices retrieves their parameters without reading the entire parameter
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table. Filters intersect, duplicate indices are returned once, and
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rows retain metadata order. An empty filter selects no rows; `fields: []`
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returns indices only. Omitted fields return the complete selected rows.
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For example, after resolving a type index, retrieve selected method facts:
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```json
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{
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"source": {
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"kind": "retained-evidence",
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"evidence_id": "<parent_evidence_id>"
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},
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"view": {
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"kind": "il2cpp-metadata",
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"collection": "methods",
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"declaring_types": [1555],
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"names": ["SendMessage"],
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"fields": ["name", "declaring_type"]
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}
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}
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```
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After finding method indices, parameters can be requested directly:
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```json
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{
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"source": {
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"kind": "retained-evidence",
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"evidence_id": "<parent_evidence_id>"
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},
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"view": {
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"kind": "il2cpp-metadata",
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"collection": "parameters",
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"method_indices": [9785],
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"fields": ["name", "method"],
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"limit": 64
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}
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}
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```
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Historical Evidence that predates these member collections remains queryable.
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A missing collection has an unknown (`null`) summary count, and requesting it
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reports that it was not collected; it is never presented as an empty inventory.
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Existing empty collections retain a zero count. Full Evidence is preserved.
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`offset` counts matching rows, not source indices. `limit` defaults to 64;
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`coverage.next_offset` continues that filtered page. Coverage describes retained
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metadata facts only; runtime behavior and correspondence to native code remain
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unknown. Each view preserves the parent Evidence link, artifact identity and
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limitations. Queries work after the source file is removed. Select
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`detail: "complete"` to return every row inline within the separate MCP response
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budget.
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## CLI
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```bash
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rea inspect-il2cpp-metadata /absolute/path/global-metadata.dat --json
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```
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The CLI defaults to complete Evidence. For compact delivery, explicitly preserve
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the full Evidence in a new file:
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```bash
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rea inspect-il2cpp-metadata /absolute/path/global-metadata.dat \
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--detail summary --evidence_output /tmp/metadata-evidence.json --json
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jq -c '{source: {kind: "inline", evidence: .records[0]}, view: {kind: "il2cpp-metadata", collection: "methods", indices: [9785], fields: ["name", "declaring_type"]}}' \
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/tmp/metadata-evidence.json > /tmp/metadata-query.json
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rea inspect-analysis-view /tmp/metadata-query.json --json
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```
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Use the exported Evidence with the CLI's inline Evidence source format described
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in [CLI and Evidence](cli.md#run-a-command). Compact delivery requires
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`--evidence_output`; existing files are never overwritten. The full export
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preserves every decoded row for subsequent queries without the original file.
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## Observations
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The result contains:
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- `artifact`: path, SHA-256 and byte length;
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- `magic`: unsigned little-endian header signature (`0xFAB11BAF`, delivered as a JSON number);
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- `metadata_version`: `24`, `27`, `29`, `31` or `39`;
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- `index_widths`: the serialized widths (1, 2 or 4 bytes) of
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`type_definition`, `generic_container`, `parameter` and `type` indices, and
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`type_width_source`. Version 39 derives the type index width from the
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`interface-offsets-record` or the `type-definition-record`; versions 24, 27, 29
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and 31 always use 4-byte indices (`fixed-width-version`);
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- `sections`: all version-specific header sections in header order, each with `offset`, `size`
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and `count`. Versions 24 to 31 record no counts, so `count` is `null` and
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record counts come from the section sizes;
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- `images`: `name`, `type_start` and `type_count`;
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- `types`: `name`, `namespace`, `method_start`, `method_count`,
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`nested_type_start`, `nested_type_count` and `declaring_type`;
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- `methods`: `name` and `declaring_type`;
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- `fields`, `properties` and `events`: `name` and `declaring_type`, the type
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whose member range holds the row (`-1` when none does);
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- `parameters`: `name` and `method`, the method whose parameter range holds it;
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- `string_literals`: managed string literals as `value`, or `value_base64` with
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the exact bytes when they are not valid UTF-8;
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- `limitations`.
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A row's position in its collection is its metadata index, so `type_start`,
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`method_start` and `declaring_type` refer to positions in `types` or `methods`.
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`nested_type_start` instead indexes the metadata's `nestedTypes` table, which is
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not returned; each nested type's `declaring_type` carries that relationship.
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A type's `declaring_type` is derived from the `nestedTypes` section and is `-1`
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for top-level types. The start of an empty range can retain the original value
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`-1`.
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The complete inventory of a large game is several megabytes and can exceed
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the MCP response budget. Summary delivery and filtered, projected pages keep
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unneeded rows out of agent context without discarding the source Evidence.
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## Failures
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A file whose magic is not `0xFAB11BAF` fails as an unsupported target with
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`unrecognized-magic`. The file may be encrypted or may not be IL2CPP metadata.
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A version other than 24, 27, 29, 31 or 39 fails as an unsupported target with
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`unsupported-version`.
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Damaged metadata returns an input error (`invalid_format`) whose
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message names one reason:
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| Reason | Meaning |
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| ------------------------- | ---------------------------------------------------------------------------------------------------------------- |
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| `truncated-header` | The file is shorter than the header. |
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| `unexpected-header-size` | `stringLiterals.offset` is not the header size: 264 bytes for version 24, 256 for 27, 29 and 31, 380 for 39. |
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| `section-out-of-bounds` | A section extends beyond the file, or a non-empty section starts inside the header. |
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| `section-overlap` | Two sections overlap. Zero-size sections are exempt and gaps are allowed. |
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| `record-size-mismatch` | A section size does not divide into its records, or the record size differs from the one the index widths imply. |
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| `type-index-width` | The record used to derive the type index width implies no 1, 2 or 4 byte width. |
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| `index-out-of-range` | A serialized index or range points outside its target collection. |
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| `nested-type-conflict` | A type is listed as nested in two types, in itself, or in a cycle of declaring types. |
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| `declaring-type-mismatch` | A method inside a type's method range names a different type, or a method lies outside its type's range. |
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| `image-range-overlap` | Two images claim the same type definitions. |
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| `invalid-string` | A name index does not start a string, or the name is unterminated or not valid UTF-8. |
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A version field that disagrees with the file's layout, for example a version
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39 file relabeled as 29, usually surfaces as `unexpected-header-size` or
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`record-size-mismatch`.
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Two checks are stricter than the IL2CPP runtime: a name index must start a
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string, and an empty range's start must lie between -1 and the collection size.
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Every Unity-written file checked so far satisfies both; metadata rewritten by
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other tools may be rejected.
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An incomplete inventory is never reported as complete. Failures after a verified
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snapshot retain partial source Evidence with its SHA-256, byte length and any
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validated section row counts; these counts do not establish that names and
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relationships were decoded. A file that changes during reading and a cancelled
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request keep distinct errors. Decode checkpoints yield for cancellation, and
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close waits for active work. Each reader admits one inspection at a time.
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Resource guards bound the selected file to 256 MiB and the encoded complete
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report to 64 MiB, checking row counts before allocation and JSON/UTF-8/base64 expansion during
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decoding, before serialization. Names and identical literal spans are decoded
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once within one stable file snapshot; no filesystem results are cached across
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inspections. Ownership assignment also yields to cancellation. MCP also applies its
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[response transport budget](mcp-contracts.md); a complete report within the
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report limit can still require the summary and paging path.
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## Outside this tool
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- Decrypting or deobfuscating protected metadata.
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- Native code addresses, member types and method signatures; use the
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[native workflow](native-investigation.md) for native code.
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- Metadata versions other than 24, 27, 29, 31 and 39.
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Names come from the metadata file only. They do not establish which methods
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were compiled into the native binary or how they behave at runtime.
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## Real producer verification
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`npm run verify:il2cpp:metadata -- --metadata PATH` exercises a caller-supplied
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`global-metadata.dat` through the public CLI and MCP. It is opt-in, like
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`verify:pcap`, because no real game metadata ships with the repository. Normal
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inspection does not need it.
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The follow-up was checked against the public Cpp2IL
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[`Simple_2022_3_35` sample](https://github.com/SamboyCoding/Cpp2IL/tree/b5ad444b82267cb1e4b88b8b373c008105bdea52/TestFiles/Simple_2022_3_35):
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version 31, 1,892,268 bytes, SHA-256
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`2441635a7c234a1a34deccc6a9906d6f5abcbdab078a38b2bf488a52a4962c48`.
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An independent byte-layout oracle matched all 36 images, 2,468 types and 12,409
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methods. Corresponding managed DLLs independently matched names and ownership
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for 35 images, 2,463 types and 12,406 methods; the generated image has no matching
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DLL. This does not establish real-producer coverage for versions 29 or 39.
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