yv1ing/z3r0/jadx

Claude Code and agent skill by yv1ing/z3r0

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Use jadx for authorized Android APK, DEX, AAR, and JAR decompilation, app logic review, endpoint discovery, embedded-secret review, and mobile reverse engineering.

Install

npx vskill@latest install yv1ing/z3r0/jadx

SKILL.md

jadx

Use jadx to decompile Android APK, DEX, AAR, and JAR inputs into readable Java source and decoded resources. Prefer CLI output that can be searched, scripted, and archived.

Help first

Before constructing commands, run the installed help and use it as the source of truth:

bash
jadx --help

Usage rules

  • Work only on provided Android artifacts or explicitly authorized mobile applications.
  • Prefer task-scoped output directories and preserve the original input file.
  • Ensure the output directory is writable and has enough space because decompiled output can be several times larger than the input.
  • Start from resources/AndroidManifest.xml, then inspect entry points and security-sensitive packages under sources/.
  • Use --deobf for obfuscated apps and --show-bad-code when partial decompilation is useful.
  • Use apktool when manifest, resources, smali, or packaging fidelity matters more than readable Java-like source.
  • Save large grep results and decompiled snippets to files rather than streaming them into the conversation.

Common workflows

bash
# Standard decompilation
jadx app.apk -d app-jadx
 
# Recommended for obfuscated production apps
jadx --deobf app.apk -d app-jadx
 
# Faster code-only pass
jadx --no-res --deobf app.apk -d app-code
 
# Resources-only pass
jadx --no-src app.apk -d app-resources
 
# Preserve partially decompiled methods when errors occur
jadx --show-bad-code app.apk -d app-jadx
 
# Fallback mode for difficult inputs
jadx --fallback --show-bad-code app.apk -d app-jadx

Output layout

text
app-jadx/
├── sources/                 # Decompiled Java source
│   └── com/example/app/
└── resources/               # Decoded Android resources
    ├── AndroidManifest.xml
    ├── res/
    └── assets/

Start analysis from resources/AndroidManifest.xml, then inspect entry points and security-sensitive packages under sources/.

Recommended workflow

bash
apk=app.apk
out=app-jadx
 
jadx --deobf --show-bad-code "$apk" -d "$out"
 
# Entry points and components
grep -r "extends Activity\|extends AppCompatActivity\|extends Application\|extends Service\|extends BroadcastReceiver" "$out/sources/"
 
# URLs and API declarations
grep -rE 'https?://[^"'"'"']+' "$out/sources/" "$out/resources/"
grep -r "@GET\|@POST\|@PUT\|@DELETE\|@PATCH\|baseUrl\|BASE_URL\|API_URL" "$out/sources/"
 
# Embedded secrets and authentication material
grep -ri "api.*key\|apikey\|secret\|password\|passwd\|token\|bearer" "$out/sources/" "$out/resources/"
 
# Crypto, storage, WebView, TLS handling
grep -r "Cipher.getInstance\|MessageDigest\|DES\|MD5\|SHA1\|SecureRandom" "$out/sources/"
grep -r "SharedPreferences\|SQLite\|openFileOutput\|MODE_WORLD_READABLE\|MODE_WORLD_WRITABLE" "$out/sources/"
grep -r "setJavaScriptEnabled.*true\|addJavascriptInterface\|WebView.*loadUrl" "$out/sources/"
grep -r "TrustManager\|HostnameVerifier\|CertificatePinner\|checkServerTrusted" "$out/sources/"

Common analysis tasks

API endpoint discovery
bash
jadx --deobf app.apk -d app-jadx
 
find app-jadx/sources \
  -name '*Api*.java' -o \
  -name '*Service*.java' -o \
  -name '*Client*.java'
 
grep -r "@GET\|@POST\|@PUT\|@DELETE\|@PATCH" app-jadx/sources/ | sort -u
grep -r "baseUrl\|BASE_URL\|API_BASE\|API_URL" app-jadx/sources/ app-jadx/resources/ | sort -u
Embedded secret review
bash
jadx --no-res --deobf app.apk -d app-code
 
grep -ri "api.*key\|apikey\|client.*secret\|secret.*key" app-code/sources/
grep -ri "username.*password\|user.*pass\|password\|passwd\|pwd" app-code/sources/
grep -ri "token\|jwt\|bearer\|authorization" app-code/sources/
IoT companion app review
bash
jadx --deobf iot.apk -d iot-jadx
 
grep -rE 'https?://[^"'"'"']+' iot-jadx/sources/ iot-jadx/resources/ | grep -vi "google\|android\|facebook"
grep -ri "discover\|scan\|broadcast\|mdns\|udp\|mqtt\|coap\|onvif" iot-jadx/sources/
grep -ri "Authorization\|apiKey\|token\|login\|authenticate" iot-jadx/sources/
grep -r "CertificatePinner\|TrustManager\|HostnameVerifier" iot-jadx/sources/
Batch processing
bash
for apk in *.apk; do
  name=$(basename "$apk" .apk)
  out="jadx-$name"
  jadx --no-res --deobf "$apk" -d "$out"
  grep -ri "api.*key\|password\|secret\|token\|baseUrl" "$out/sources/" > "findings-$name.txt" || true
done

Useful options

  • --deobf: rename obfuscated classes and members where possible.
  • --use-source-name-as-class-name-alias: use source file names as deobfuscation hints; valid values include always, if-better, and never.
  • --show-bad-code: emit partial code for methods jadx cannot cleanly decompile.
  • --fallback: use fallback decompilation when normal output fails.
  • --no-res: skip resources for faster source-only analysis.
  • --no-src: decode resources without Java source output.
  • --export-gradle: export a Gradle project layout.
  • -j <threads>: set decompilation thread count.

Troubleshooting

bash
# Obfuscated names make code hard to follow
jadx --deobf --use-source-name-as-class-name-alias if-better app.apk -d app-jadx
 
# Decompiler errors hide important logic
jadx --show-bad-code --fallback app.apk -d app-jadx
 
# Large APK is slow
jadx --no-res -j 8 app.apk -d app-code
 
# Need build-like project structure
jadx --export-gradle app.apk -d app-project

Output

Report the APK or artifact path, hash if available, jadx command used, output directory, relevant paths under sources/ or resources/, exact constants/URLs/methods/components found, why the finding matters, and limitations such as decompiler errors or obfuscation.

Security

  • Security scanPassed, 100 of 100Pattern checks on the skill's files.
  • Model reviewNot runA model review is scheduled for the next rescan.

See the full security report

Quality evaluation

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Source

Popularity

Repository stars
572
Repository forks
96
7-day trend score
32

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