rea/docs/binary-diagnostics.md

Offline binary diagnostics

inspect_binary_layout / inspect-binary-layout answers what an explicit file contains: section/segment layout, original symbols/relocations, static linkage names and mitigation indicators. It works without an active Hopper, Ghidra or IDA target. CTF is one possible use; crash triage, compatibility and ordinary binary inspection use the same modular capability.

Bring your own engine

Initial real verification covers Linux x64, ELF64 x86-64 little-endian EXEC/DYN/REL. Provide an absolute Python executable whose environment already contains unchanged pwntools 4.15.0, pyelftools 0.33 and Unicorn 2.1.2:

REA_PWNTOOLS_PYTHON=/absolute/isolated-env/bin/python \
  rea inspect-binary-layout ./selected.elf --json

{
  "name": "inspect_binary_layout",
  "arguments": { "path": "/artifacts/selected.elf" }
}

REA never installs Python, packages or GDB, changes a user init file, launches the selected object as a host process, or requests runtime library resolution. The Python process uses isolated mode and an owned cache. Exact upstream profiles are recorded in upstream provenance.

Interpreting results

• Artifact path, SHA-256 and size identify original selected bytes. All parsing reads an owned stable snapshot; the original is unchanged.
• Addresses, offsets, lengths and flags are hexadecimal strings. A linked address is not a runtime address. Runtime load base remains null. A zero EXEC/DYN entry means absent; a relocatable entry is not applicable.
• Each symbol retains its table and entry index. Its reported value can mean undefined, alignment, absolute value, no address, unknown section index, section offset, TLS offset or linked virtual address. Duplicate names remain separate entries. SHN_XINDEX remains unresolved in the selected upstream representation; its external index table is not silently treated as resolved.
• Relocatable objects have section-relative relocations and no executable entry claim. Signed REL/RELA relocation addends are decimal strings. Packed RELR tables retain full original bytes and upstream-decoded offsets as derived evidence, with per-offset packed-word locations and implicit addends unknown. Overall relocation inventory completeness remains unknown. A relocatable SHN_UNDEF target or inactive SHT_NULL header remains an explicit unknown with the original reported section index and offset.
• REL/RELA symbol references retain their original table and entry indices. Positive indices resolve through a validated symbol table; symbol index zero means a zero symbol value without a table lookup, including when no table is linked. Malformed references fail with the affected section and symbol index.
• Section-name and symbol tables require declared SHT_STRTAB links. SHN_UNDEF explicitly means no section names: display is empty, raw name and location unknown, with the original name offsets retained. Extended section-name indices resolve through section zero and undergo the same validation.
• Symbol tables require a declared SHT_STRTAB link. Name offsets and terminators must stay inside the declared string table; malformed references fail before unrelated bytes can become names. Dynamic dependencies use DT_STRTAB/DT_STRSZ with a unique file-backed mapping; ambiguous or unbacked mappings are explicitly unsupported.
• Name display strings use UTF-8 replacement for opaque bytes, including sectionless dependency names and interpreter paths. Raw name bytes and string-table ranges retain observed identity where resolvable; ranges include the terminating NUL and base64 bytes exclude it.
• NOBITS and NULL sections provide no file bytes. Reported file-backed ranges are checked against snapshot size again at the public boundary. PT_NULL payload fields are unused: reported numbers remain, file backing is none and interpreted permissions are null. Segments with zero file size also have no file bytes.
• Sectionless dynamic images still report dependency names with raw bytes and file locations where uniquely mapped. Missing symbol/relocation section tables do not establish that those runtime tables are absent. Upstream RELRO/canary heuristics rely on sections and can be incomplete in this case; their reported candidates retain an explicit coverage limitation.
• DT_NEEDED/PT_INTERP are reported names, not resolved runtime paths. GOT/PLT maps are derived convenience views and may collapse aliases. PLT inference can emulate selected instructions in Unicorn; its outputs are static candidates. Exec syscall tracing observes host process launches. Map completeness remains unknown and original upstream warnings are returned inline.
• Canary, PIE, NX, executable-stack and RELRO are static inferences. NX and executable-stack are separate upstream indicators: on x86-64 an executable stack can accompany an unknown (null) NX indicator. ET_DYN can be a shared library, and an absent canary symbol does not prove every function unprotected.

When complete layout Evidence is already retained, inspect_analysis_view / inspect-analysis-view projects a summary, the mitigations or linkage facet, one section or symbol, or a stable page without re-running the decoder. CLI one-shot invocations pass portable inline Evidence JSON; an MCP session uses the retained evidence_id. Page limit is required and bounded by the measured MCP stdio budget documented on the tool contract.

Over MCP, inspect_binary_layout with "detail": "summary" retains the complete layout Evidence in the session and returns only its summary view. Its normalized_result.parent_evidence_id names the retained layout for later section, symbol, mitigation or linkage views. The default complete detail and CLI output are unchanged.

Complete results have a 32 MiB input, 64 MiB reply, 1 MiB combined diagnostics and 30-second owned command deadline. REA_PWNTOOLS_MAX_INPUT_BYTES raises the input bound alone, up to 1 GiB; the reply and deadline bounds are unchanged. The reply budget applies to the decoder record; the CLI/MCP Evidence envelope adds copies and encoding overhead. The pinned MCP SDK defaults to a 10 MiB receive buffer. Large complete results need a caller-configured StdioClientTransport({ maxBufferSize: ... }) and a matching server REA_MCP_MAX_RESPONSE_BYTES. See MCP delivery budgets. These settings affect delivery, not decoder coverage or limits. The large extended-index verification uses 256 MiB and an explicit five-minute request timeout in its separate opt-in MCP lane. REA does not silently truncate the result. Python lowers resource soft limits to at most 3 GiB virtual address space, 30 CPU seconds and 64 MiB file output. Inherited tighter soft/hard limits are retained, and the effective values are returned in the result limitations. Virtual address space is not RSS; Unicorn needs a large virtual map. Limits fail with no partial success, and owned process/root cleanup completes independently of cancellation.

Core files, GDB session/state/control, optional pwndbg enrichment and instruction inspection are separate increments tracked by #969. This increment makes no real support claim for those features or other operating systems/architectures.

Typed decoder failures retain bounded captured_output (stdout, stderr and an explicit truncation flag) alongside the original failure category and reason. Successful diagnostics also exposes the supervisor's truncated flag. Output beyond the complete diagnostic budget is rejected, including when the decoder writes a valid reply; cleanup and late cancellation reuse the observed flag. Memory allocation failures use resource_constraint, with effective resource limits (or an explicit unknown) and memory-specific recovery guidance. A MemoryError alone does not establish the exact failed allocation or that a particular budget was exhausted. Invalid undersized symbol entries are rejected before REA reports source ranges for them. The bridge reserves 1 MiB to report allocation failures. If even error reporting or serialization fails with MemoryError, its reserved exit status preserves the resource classification with unknown effective limits. Reserved exits require a matching private marker written by the bridge's actual failure branch. Bare launcher exits or missing/unwritable markers retain process diagnostics with the resource cause unverified. Signal termination alone is never classified as observed memory exhaustion. The small bootstrap also covers catchable MemoryError during adapter imports, compilation and initialization. Python interpreter startup failures before the bootstrap runs retain their observed process diagnostics without guessed causes. SIGXCPU retains a CPU resource diagnostic and CPU-specific recovery advice. Observed EFBIG writes or SIGXFSZ termination retain a file-size resource diagnostic and file-size-specific recovery advice. If a tight file limit also prevents writing the limit record, effective values remain unknown. The bridge records actual limits in owned storage before analysis; missing or malformed limit reports remain unknown with their read failure preserved. A received signal alone does not establish its exact cause. Dynamic tags require a complete DT_NULL inside PT_DYNAMIC; interpreter names and ranges end at the first NUL, with any padding still represented by the original segment range.

Ghidra process failures

When output from the failing Ghidra startup or operation reports java.lang.OutOfMemoryError, REA returns resource_constraint. Java heap or GC overhead exhaustion includes heap-specific recovery advice. Metaspace and array size failures do not recommend increasing the heap; native-thread exhaustion is reported as a capacity constraint with unknown limits.

configured_jvm_max_heap records the explicit -Xmx value selected by REA's launch builder. It is a configuration fact, not measured memory use or proof of the effective JVM limit; JVM environment options may affect that limit. When a Windows script wrapper selects the JVM, this value remains unknown. Historical stdout and stderr remain available, but classification uses only the failing operation's failure_output. Retained stdout and stderr share an 8 MiB budget, but every drained byte is scanned for java.lang.OutOfMemoryError: failure_output.observed_oome records the latest confirmed token's bounded line per stream from the failing operation, with its byte offset, even after the budget is spent. These observations own OOME detection; retained text that ends at a class-name prefix cannot confirm a complete token. line_complete distinguishes a known line end from an incomplete trailing context; invalid_utf8 marks replacement-decoded context. Incomplete operation output without an observed OOME keeps the original failure code and explains that a memory cause cannot be ruled out. Incompleteness alone does not confirm a memory constraint or justify heap-specific advice. Token context stays within the failing operation's checkpoint; a class-name prefix in a different identifier is not OOME evidence. A trailing bare token requires an observed stream EOF to establish its boundary. Output draining waits at most one second, subject to earlier cancellation or the startup deadline. output_incomplete marks a snapshot taken before stream closure; cleanup ownership remains with the session until release succeeds.

Portable PE resources

inspect_pe_resources / inspect-pe-resources inspects an explicit PE32 or PE32+ file without an active target, native engine, Python, or Windows SDK:

rea inspect-pe-resources ./selected.exe --json

{
  "name": "inspect_pe_resources",
  "arguments": { "path": "/artifacts/selected.exe" }
}

The complete Evidence identifies the stable artifact snapshot by path, byte count and SHA-256. Resources retain separate type, name and language identities: numeric IDs are distinct from UTF-16 names, whose original bytes are also reported. Directory headers, entries, data entries and payloads retain original file offsets and lengths. Each opaque payload has its own SHA-256; code page and reserved data-entry fields are preserved.

RT_GROUP_ICON records expose original image descriptors and RT_ICON candidates. A reference resolves only when an icon with the same numeric ID and language exists. Missing references, other-language candidates and declared-size mismatch remain explicit. Encoded dimensions are preserved (zero denotes 256 pixels). This is static reference inspection; no image decoding, language fallback, resource loading or selected-file execution occurs.

An absent resource data directory is a complete empty inventory. Malformed headers, truncated tables, cycles, duplicate sibling identities, unbacked or ambiguous RVA mappings, nonidentical overlapping ranges and unsupported tree shapes fail explicitly, rather than returning partial inventories. Exact shared payload ranges are supported. The supported tree has three levels: type, name, and language. Other resource payload formats remain opaque.

max_file_bytes defaults to 64 MiB (maximum 512 MiB); max_entries defaults to 16384, the largest stock Windows resource image measured with headroom (maximum 65536). CLI options are --max-file-bytes and --max-entries. Metadata is bounded to 8 MiB; exceeding any budget fails without truncation. Large Evidence envelopes may require a caller-configured MCP transport receive buffer because envelope copies add overhead. Requests honor cancellation during snapshot reading, directory traversal and payload hashing. The operation reads regular files only and rejects symbolic links.

Byte entropy triage

inspect_byte_entropy / inspect-byte-entropy profiles any local regular file without an analysis engine, execution, extraction or network access.

rea inspect-byte-entropy ./firmware.bin --block-size 4096 --json
rea inspect-byte-entropy ./firmware.bin --offset 4096 --length 65536 --json

{
  "name": "inspect_byte_entropy",
  "arguments": { "path": "/artifacts/firmware.bin", "detail": "summary" }
}

Complete Evidence includes artifact (original path, byte size and SHA-256), block_size, window, file_entropy, thresholds, blocks, runs and limitations. For a 4096-byte zero-filled file, the entropy fields are:

{
  "block_size": 4096,
  "window": { "offset": 0, "length": 4096 },
  "file_entropy": 0,
  "thresholds": { "high": 7.2, "low": 1 },
  "blocks": [{ "offset": 0, "length": 4096, "entropy": 0 }],
  "runs": [{ "offset": 0, "length": 4096, "classification": "low" }]
}

Offsets and lengths are decimal byte counts. Blocks begin at the requested offset (default zero); omitted length extends to EOF. Explicit windows past EOF fail rather than silently clipping. The final block may be shorter. block_size must be a power of two from 256 through 65536, default 4096. A window may produce at most 32,768 block rows; larger requests fail before the file scan with a capacity error. Choose a shorter window or larger block size. SHA-256 and file_entropy always cover the entire file, including when a window is selected. Empty files and empty windows are accepted; empty entropy is zero by convention. The tool reads the size the file reports. A file that reports size 0, such as a Linux /proc entry, returns no blocks with a limitation that the result does not show the file is empty. File identity, size and timestamps are checked across the read; detected changes produce an error rather than Evidence.

Shannon entropy is reported in bits per byte from 0 to 8, rounded to four decimal places. Adjacent blocks with reported entropy at least 7.2 form high runs; blocks at most 1.0 form low runs. Other blocks interrupt runs. Entropy does not prove encryption, and this measure cannot distinguish encrypted from compressed data. Small blocks can underestimate entropy; the result is a triage clue.

MCP detail: "summary" retains complete Evidence in the session and returns file entropy, block/run counts, thresholds, the selected window, and the ten longest runs (ties ordered by file offset). Use its parent_evidence_id to retrieve complete Evidence, or request its summary with inspect_analysis_view. The CLI returns complete Evidence through the same service. Summary detail requires a session capable of retaining Evidence.

Reads use one block-sized buffer and a 256-entry histogram. Complete output can become very large because it includes one row per selected block, and summary delivery still retains that full list. Use a shorter length or a larger block size to reduce it. Full Evidence and its serialization require memory proportional to the number of selected blocks. The 32,768-row ceiling bounds the actual retained block objects and their serialized representation: a cap-sized run below produced 1,514,877 serialized bytes and increased V8 heap use by 21.2 MiB on the measured host. The cap therefore bounds this output independently of file size; it is not a portable process-memory guarantee. Narrow the window or increase block size to reduce retained rows further.

Local service measurement (macOS arm64, Node 24.18.0, 100,000,000-byte file, 4096-byte blocks, file already in the OS cache): first process run took 1.113 s wall / 1.148 s CPU with 145.3 MiB peak RSS; a second run in the same process took 1.015 s / 1.035 s CPU, with cumulative peak RSS 155.8 MiB. Each read 100,000,000 bytes and produced 24,415 blocks. Measurements include Evidence construction, summary projection and JSON serialization, with no child processes. Complete Evidence serialized to 1,122,303 bytes and its summary to 2,705 bytes. A cap-sized 134,217,728-byte sparse file with 4096-byte blocks produced 32,768 rows and 1,514,877 serialized bytes; V8 heap use increased by 21.2 MiB and RSS by 18.1 MiB in that process. This separate measurement used the same macOS arm64 host and Node version. Cold disk I/O, token counts and an agent investigation were not measured; there was no previous equivalent tool to benchmark. These figures do not establish a portable peak-memory bound, constant memory for retained Evidence or faster agent task completion.