72 lines
4.0 KiB
Markdown
72 lines
4.0 KiB
Markdown
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# U-Boot legacy uImage containers
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`inspect-artifact` and `extract-artifact` recognize the big-endian
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`0x27051956` legacy uImage signature regardless of filename. They read local
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stored bytes without booting, executing, decompressing or modifying the image.
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FIT is a different format; its analysis is outside this reader.
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The same domain header/table facts and artifact reader serve CLI and MCP.
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The root is an archive with unknown executable architecture. The header's CPU,
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OS, type, compression, load address and entry address are declarations, not proof of
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compatible or executable payloads. Raw numeric identifiers remain available
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alongside names; unrecognized identifiers have the name `unknown`.
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The header's CRC32 and the declared payload's CRC32 must verify before a
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successful inventory. `payload.bin` contains the complete stored payload.
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Multi-file images also expose `image-0.bin`, `image-1.bin`, and so on. These
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component names are generated from table order. Components follow the zero-terminated big-endian size table, with four-byte
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padding after every nonfinal component. Their physical source ranges and
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content hashes retain precise provenance. Extraction writes the complete
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payload and every component, so multi-file output can approach twice the input
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size. Compressed payloads remain compressed.
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The fixed 32-byte name field is retained as `name_bytes_hex`. `name` contains
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the UTF-8 bytes before the first NUL, or null when those bytes cannot be decoded
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exactly. For example, a producer can truncate a multibyte character at the
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32-byte boundary; replacement characters do not establish a source name.
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## Bounded work and retained facts
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The reader admits at most 4,096 components, a resource policy rather than a
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format maximum. It reads at most 16,388 bytes for the size table and refuses an
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excess count as a capacity limit before its remaining payload CRC scan.
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Shared artifact identity hashing has separate cost. The
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same prefix participates in the native incremental CRC32 calculation; no
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custom bytewise CRC table or full-payload buffer is retained. Remaining CRC
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reads and member streams use 64 KiB chunks. Parsed facts are cached for one reader. Carrier state is checked during
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directory preparation, at member open and after stream completion; metadata
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getters return the retained facts. Close joins active member
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pipelines and final validation before releasing the descriptor; failed cleanup
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remains owned for retry.
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Prefer a retained summary when only a few facts are needed:
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```sh
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rea inspect-artifact firmware.bin --detail summary \
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--evidence_output firmware.evidence.json --json
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rea extract-artifact firmware.bin --json
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```
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With MCP, `inspect_artifact` with `detail: "summary"` retains the complete
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Evidence. Use `inspect_analysis_view` and its `parent_evidence_id` for exact
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logical paths, batches of occurrence/content IDs, selected fields and pages.
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Coverage and limitations remain attached. Retained views are historical
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observations tied to the saved Evidence. Complete Evidence remains available;
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these views do not narrow the examined inventory.
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## Verification scope
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The public OpenWrt 24.10.0 GL-AR150 initramfs kernel is checked against its
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[published digest](https://downloads.openwrt.org/releases/24.10.0/targets/ath79/generic/sha256sums):
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`027c60a7061462d8145b11efa23ab02b334acb9a23a215f9095860b632ace4ff`.
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Independent `mkimage`/`dumpimage` 2023.01 provide producer and extraction
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oracles. Generated containers use real host ELF files, system metadata and
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stored gzip bytes; their declared ARM64, VxWorks or RISC-V labels do not prove
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boot/runtime compatibility. U-Boot's identifier and alignment definitions are
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pinned to commit `ece349ade2973e220f524ce59e59711cc919263f`.
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Source and compiled CLI/full/compact MCP tests cover aligned component ranges,
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unknown identifiers/text, malformed/truncated inputs, CRC failures, capacity,
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source changes, cancellation, pending reads, final validation and cleanup
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retry. Real producer results, complete-task cost measurements and limitations
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are reported in the PR. No target runtime or decompressor behavior is verified.
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