rea/docs/apple-application-analysis.md

Apple Application Inventory Projection

REA can project one or more authenticated inventory_artifact Evidence records for the same IPA, macOS .app directory, ZIP, or DMG into an Apple application inventory. The projection is execution-free: it reports exact paths, content hashes, detected formats, bundle anatomy, runtime-family hints, and path-based bridge hypotheses. It does not parse plist or CMS semantics or claim observed runtime calls.

rea project-apple-application-graph '{"inventory_evidence":[<inventory_artifact Evidence>]}'

{
  "name": "project_apple_application_graph",
  "arguments": {
    "inventory_evidence": ["<inventory_artifact Evidence>"]
  }
}

The result includes every component in each inventory category and every JavaScript-to-native bridge candidate pair. It has no caller-selected component budget, prefix truncation, or omitted-count fields. Duplicate inventory pages are merged by artifact identity and occurrence path; their Evidence IDs remain attached as source Evidence.

Coverage is complete-within-inventory when the supplied pages reconstruct the complete authenticated inventory, and partial otherwise. A partial result states that absence is unknown. Component and bridge-candidate arrays are still the complete projection of the inventory that was supplied.

Application roots

Inventory root	Application root
IPA	Each Payload/<Name>.app
.app directory	., the inventoried bundle itself
Directory, ZIP, or DMG containing apps	Each outermost <Name>.app followed by Contents/

ZIP archives made with ditto -c -k --keepParent report <Name>.app. A DMG reports <image>.dmg/<Volume>/<Name>.app; DMG child inventory needs the native macOS mounting adapter. When a DMG has only its root identity, the projection is partial and says that bundle absence is unknown. Other inventory formats, such as APK or ASAR, are rejected as input errors.

An inventoried directory whose name ends in .app is its own root even when its inventory is partial or lacks Contents/. For directory, ZIP, and DMG inventories, components outside every application root are not attributed to the application. This covers installers, disk-image extras, and AppleDouble sidecars, which therefore stay out of runtime families and bridge candidates. A limitation reports how many inventoried entries were left out. IPA projection still lists every archive component, including SwiftSupport/.

platforms lists macos for application roots with Contents/. It lists ios for shallow application roots that have an Info.plist. An application root with neither, such as an empty inventory, has no platform.

macOS bundle anatomy

bundles lists each application root and every nested bundle under it. Each bundle reports its parent_path, layout, info_plist_path, executable_candidates, and signing_paths.

Layout	Meaning	Content directory
macos-deep	Has Contents/	Contents/, executables in Contents/MacOS/
versioned-framework	Has Versions/	Each real Versions/<version>/
shallow	Neither	The bundle directory itself

Roles are path conventions (role_basis: "path-convention"):

Role	Path
app-extension	*.appex
xpc-service	*.xpc, including XPC services inside frameworks
framework	*.framework
system-extension	*.systemextension
driver-extension	*.dext
plug-in	PlugIns/*.bundle, *.plugin, *.qlgenerator, *.mdimporter
resource-bundle	Resources/*.bundle, such as SwiftPM resource bundles
bundle	Any other *.bundle
login-item	Contents/Library/LoginItems/*.app
helper-application	Contents/Helpers/*.app
nested-application	Any other nested *.app

The components also list:

• privileged_helpers: files directly in Contents/Library/LaunchServices/, where SMJobBless helpers live;
• launchd_plists: .plist files directly in Contents/Library/LaunchAgents/ (domain: "agent") or Contents/Library/LaunchDaemons/ (domain: "daemon"), as used by SMAppService;
• helpers: files directly in Contents/Helpers/.

Symlinks are reported by path in symlinks. Their targets are not inventoried, so a versioned framework is described through its real Versions/<version>/ directories rather than Versions/Current. A framework's info_plist_path is null, with a limitation explaining why, when it has more than one real Versions/<version>/ directory (even if only one of them holds a plist, because Versions/Current decides which one applies) or when its single version directory has no Resources/Info.plist.

AppleDouble sidecar files (._* and __MACOSX/) are inventory facts, but they describe neighbouring files. They are excluded from roots, bundle roles, and the anatomy components.

The projection does not read plists. Use inspect_plist on a bundle's info_plist_path or a launchd plist to read CFBundleExecutable, identifiers, SMPrivilegedExecutables, BundleProgram, URL schemes, and usage descriptions. Use inspect_signature on an executable candidate for code-signing claims.

Dylib load resolution

trace_dylib_resolution answers which file each Mach-O dylib load reaches. It runs on the active Mach-O, or on every executable in the active .app. Each executable in a bundle (the main app, XPC services, app extensions, login items, privileged helpers, and helper tools) is a separate process root with its own @executable_path.

rea trace-dylib-resolution MyApp.app --json
rea trace-dylib-resolution MyApp.app --root Contents/MacOS/MyApp --architecture arm64 --json

{
  "name": "trace_dylib_resolution",
  "arguments": { "roots": ["Contents/MacOS/MyApp"], "architecture": "arm64" }
}

Load commands are parsed in TypeScript from Mach-O and FAT headers, including the dylib_use_command encoding newer linkers emit for flags such as delayed initialization. Nothing is executed and no Apple tool is required, so the tool also works off macOS.

Resolution follows dyld:

• @executable_path is the directory of the process root's executable. It is undetermined when the root is a library.
• @loader_path is the directory of the image that holds the load command, or of the image that owns the LC_RPATH entry being expanded.
• @rpath tries each LC_RPATH of the loading image first, then those of the image that loaded it, up to the process root.
• Dependencies load dependents-first in load-command order, and each image loads once per process. A later request whose install name matches an already loaded image reuses it.
• Symlinks such as Versions/Current are followed inside the analyzed root. An escape through .. or an absolute link is escapes-target.

Each edge lists every candidate path tried, with its outcome: resolved, absent, not-mach-o, malformed, unsupported (recognized Mach-O outside parser coverage, such as big-endian images), architecture-missing, outside-target, shared-cache, escapes-target, or undetermined. Slices follow dyld's graded architectures, so an x86_64h process also loads x86_64. The edge's resolution is one of:

Status	Meaning
resolved	An image inside the analyzed root loads, and no earlier candidate was undeterminable.
conditional	An image inside the root, or in the supplied shared cache, resolves, but an earlier candidate that REA cannot decide (for example /opt/vendor/lib or /usr/lib/swift without a cache) would win if it exists on the running system.
unresolved	Every candidate is definitively absent or unusable inside the root.
undetermined	No candidate resolves inside the root, and some candidate lies outside it or depends on the environment.
shared-cache	An absolute install path, or an @rpath candidate outside the root, was found in the dyld shared cache passed as shared_cache (CLI --shared-cache). dyld loads the cached image, so later in-root candidates are unused.

A conditional image is still traced, because it is the image the analyzed root supplies. Every edge below it has loader_conditional: true, and a request that reuses it by install name is conditional too. Findings on those edges say that they apply only if the conditional image loads.

Absolute install names such as /usr/lib/libSystem.B.dylib are outside-target. On macOS 11 and later most of them live in the dyld shared cache rather than on disk, so REA does not check them against the host.

findings are derived, not observed:

• required-load-unresolved, weak-load-unresolved, and lazy-load-unresolved. LC_LAZY_LOAD_DYLIB dependencies are resolved but not traversed, because dyld loads them on first use; an unresolved one is not a launch failure.
• earlier-rpath-candidate-absent: a Mach-O placed at an earlier search path would load first. Whether code-signing library validation would reject it is not evaluated; use inspect_signature.
• dyld-environment-present: LC_DYLD_ENVIRONMENT search paths are not modeled.

verify:macos-bundle checks the parser against otool -l for every traced image. It also compares the predicted load order of two process roots with the images dyld actually loads (DYLD_PRINT_LIBRARIES).

With shared_cache, absolute candidates are looked up in that cache's image list. A process uses the cache only when both of these hold:

• the cache serves its CPU family (an arm64e cache serves arm64 and arm64e);
• one of its LC_BUILD_VERSION or LC_VERSION_MIN_* platforms (reported per slice as platforms) matches the cache's platform or alternate platform.

An iOS cache extracted from an IPSW is therefore not used for a macOS executable. A limitation names each process root the cache was not used for, and why. The result's shared_cache names the cache path, UUID, architecture and OS version. Cached images are not traversed.

An image listed in the cache but mapped in a missing or UUID-mismatched subcache is undetermined. It is listed in coverage.unverified_shared_cache_images and makes coverage partial. Without a cache, system paths stay undetermined.

dyld shared cache

inspect_dyld_shared_cache reads a dyld shared cache file set selected by path. On current macOS this is /System/Volumes/Preboot/Cryptexes/OS/System/Library/dyld/dyld_shared_cache_arm64e; a cache extracted from an IPSW also works. It runs without an open target.

rea inspect-dyld-shared-cache /System/Volumes/Preboot/Cryptexes/OS/System/Library/dyld/dyld_shared_cache_arm64e --image /usr/lib/libSystem.B.dylib --json

{
  "name": "inspect_dyld_shared_cache",
  "arguments": {
    "cache_path": "/System/Volumes/Preboot/Cryptexes/OS/System/Library/dyld/dyld_shared_cache_arm64e",
    "images": ["/usr/lib/libSystem.B.dylib"]
  }
}

The result reports:

• the magic, architecture, UUID, platform and OS version, any alternate platform (Mac Catalyst), cache type, the development/production subtype for multi-caches (including its raw ID when unknown), shared region and maximum slide;
• every VM mapping, with the file that holds it;
• every subcache by file suffix, with its UUID checked against the main cache. A missing or mismatched subcache makes coverage partial, and images mapped there are unmapped;
• the complete image list with addresses.

For each requested install path, the tool reads that image's load commands (install name, dependencies with their re-export, weak, upward and delayed-init flags, and rpaths) through the cache mappings. A path the cache does not contain is absent. Older single-file caches are read from their legacy header fields.

Nothing is executed, slid or extracted. Slide info, local symbols and the cache's code signature are not parsed. The Evidence subject is the main cache file, identified by its digest.