inliver233
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Progressive-disclosure skill for Android APK reverse engineering: recon, ad removal, membership limits, dex surgical patching, repack/sign, runtime data, Frida, environment setup, and a hard-won failure catalogue.
99 lines
4.7 KiB
Markdown
99 lines
4.7 KiB
Markdown
# apk-reverse
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An Agent Skill for Android APK reverse engineering, debloating, ad removal, surgical
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dex patching, repacking, and runtime/server analysis.
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It is a **skill**, not a tutorial: it is written to be loaded by an agent (Claude Code,
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Codex, or any harness that supports the Agent Skills format) while it works, so it is
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organized for progressive disclosure — a short decision-oriented `SKILL.md`, detailed
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references loaded only when a step needs them, and parameterized scripts you can run
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directly.
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## What it is good at
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- Deciding **fast** whether a request is even achievable client-side, instead of
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burning hours on a paywall that is enforced by a server.
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- Choosing the **safest patch layer** for a given change, and avoiding the layers that
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break the app.
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- Avoiding the specific mistakes that produce an APK that builds perfectly and dies at
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runtime.
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## Structure
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```
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SKILL.md decision tree, workflow, hard constraints, indexes
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references/ loaded on demand, one topic each
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recon.md identify packer, SDKs, code location, tamper checks
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ad-removal.md ad taxonomy, wrapper mapping, callback trap, verification
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membership-and-limits.md server vs client authority; what is and is not patchable
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server-api.md probe an app's API; prove who owns the gate
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dex-patching.md patch-layer table + dexlib2 technique in depth
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repack-and-sign.md repack rules, signing, install, post-install hazards
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runtime-data.md DataStore / SharedPreferences / SQLite / protobuf
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dynamic-frida.md Frida setup, hooking strategy, anti-instrumentation
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environment.md device/emulator setup, ADB, offline devices, log signals
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verification.md the claim ladder; what "done" means
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pitfalls.md the failure catalogue -- read before building
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scripts/ parameterized, path-agnostic
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smtool.py baksmali/smali wrapper with a configurable classpath
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dexpatch/ dexlib2 method-level surgical rewriter (preferred tool)
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patch_smali.py method-body replacement in a smali tree
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dex_strpatch.py byte-level string patch with a string_ids ordering guard
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dex_classdiff.py prove a dex edit was surgical
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dex_strings.py strings/URLs/SDK markers without a decompiler
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find_refs.py count callers of a method before patching it
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repack.py rebuild APK, strip only signatures, sign
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devsh.py quoting-safe ADB shell helper
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usb_net_proxy.py give an offline device network over USB
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datastore_inject.py encode/inject AndroidX DataStore preferences safely
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probe_api.py probe an HTTP API with the right headers
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grab_crash.py recover stacks hidden by a crash-reporter SDK
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install_test.py install + launch health check with logcat signal scan
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```
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## Install
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Drop this directory where your agent finds skills, e.g.:
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```
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<skills-dir>/apk-reverse/SKILL.md
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```
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The agent loads `SKILL.md` when a task matches its description, and pulls in
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`references/*` only as needed. No global state, no machine-specific paths.
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## Requirements
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Nothing is mandatory; each script checks what it needs.
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| Tool | Used for |
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| Python 3.9+ | all scripts |
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| `baksmali` / `smali` + `dexlib2` jars | disassembly, assembly, surgical patching |
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| JDK (`javac`, `java`) | building/running the dexlib2 patcher |
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| Android SDK build-tools (`aapt`, `zipalign`, `apksigner`) | manifest info, alignment, signing |
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| `uber-apk-signer` (optional) | one-step align + sign |
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| ADB | device work |
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| Frida (host package + matching on-device server) | dynamic analysis |
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| a rooted device or emulator | anything beyond static analysis |
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## Read this first
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`references/pitfalls.md`. It is the most valuable file here — every entry is a failure
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that produced a broken artifact while looking completely healthy.
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The three that hurt most:
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1. Stripping the whole `META-INF/` during a repack deletes ServiceLoader registrations
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and the app dies at startup with an error that names an unrelated library.
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2. Patching a byte-level string without preserving `string_ids` ordering gets the whole
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dex rejected, while checksums and signatures verify perfectly.
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3. Rebuilding a dex with a whole-tree smali round-trip damages R8 output invisibly —
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class tables compare clean, and it only blows up at runtime.
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## Scope
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Built for working on your own applications, on samples you are authorized to analyze,
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and in CTF/competition sandboxes. It contains no vendored third-party binaries and no
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target-specific data.
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