bypassing-mobile-pinning

Bypassing Mobile Pinning

Most time lost here is spent bypassing pinning that was never there. An empty proxy has at least six causes, and the fix for each is different — one of them is not pinning at all but Android's default distrust of user CAs, and another is that the app has its own TLS stack and never saw your proxy. Diagnose before you reach for a bypass script.

Use only against apps you are authorized to test.

When to Use

• Burp/mitmproxy/Charles shows a TLS handshake failure from a mobile app
• The proxy shows nothing while the app clearly reaches the network
• The app reports "network error", "connection insecure", or similar with the proxy configured
• You know the target pins, and need the right hook for its stack

When NOT to Use

• Flutter targets — use reversing-flutter-apps; Flutter's failure looks identical but the cause and fix are specific to its engine
• The wider mobile assessment — use testing-mobile-applications
• The backend once traffic is visible — use testing-apis
• Reversing a native .so in depth — use analyzing-binaries

Diagnose First

Run this before installing anything. The symptom tells you the cause.

Symptom	Likely cause	Fix
Proxy sees the CONNECT, then TLS alert unknown_ca / bad_certificate	Your CA is not trusted	Install as system CA, or patch Network Security Config
Proxy sees the CONNECT, then alert only for some domains	Real pinning, scoped to those hosts	Hook the pinning check
Proxy sees nothing at all, app works	App ignores the system proxy	Force traffic at the network layer (Flutter, gRPC, some SDKs)
Proxy sees the handshake, server rejects the client	Mutual TLS — the app presents a client certificate	Extract the client cert; this is not pinning
Works on emulator, fails on device (or vice versa)	Root/emulator detection, not TLS	Different problem — see the detection section
Fails only after login	Pinning applied to the API host only	Hook, then re-check

# What does the app actually declare?
apktool d target.apk -o out
cat out/res/xml/network_security_config.xml 2>/dev/null
rg -n 'networkSecurityConfig|usesCleartextTraffic' out/AndroidManifest.xml

# Which TLS stack is in play?
rg -l 'okhttp3|CertificatePinner|TrustKit|AFNetworking|Alamofire' out/ 2>/dev/null | head
unzip -l target.apk | rg 'libssl|libcrypto|libconscrypt|libflutter|libil2cpp|libmonodroid'

Check Network Security Config before assuming pinning. Since Android 7, apps do not trust user-installed CAs by default. An app with no pinning code at all will still fail interception. Two fixes:

# A. Install your CA as a SYSTEM certificate (no app modification — preferred)
#    Emulator:
emulator -avd <name> -writable-system
adb root && adb remount
openssl x509 -inform PEM -subject_hash_old -in burp.pem | head -1   # → e.g. 9a5ba580
cp burp.pem 9a5ba580.0 && adb push 9a5ba580.0 /system/etc/security/cacerts/
adb shell chmod 644 /system/etc/security/cacerts/9a5ba580.0
#    Rooted device: use a Magisk module so the change survives reboot

# B. Patch the config and repack (when you cannot get a system CA)
#    Add to network_security_config.xml:
#      <base-config><trust-anchors>
#        <certificates src="system"/><certificates src="user"/>
#      </trust-anchors></base-config>
apktool b out -o patched.apk && apksigner sign --ks debug.keystore patched.apk

Option A is better: it modifies nothing in the app, so integrity checks, signature checks, and Play Integrity are unaffected. Reach for B only when you cannot get a system CA onto the device.

Android: Hook by Stack

Identify the stack, then hook it. A generic script that misses will look like "the bypass failed" when it simply targeted the wrong layer.

# Start here — covers the common Java-layer stacks in one shot
objection -g com.target.app explore
# then: android sslpinning disable

# Or a maintained universal script
frida -U -f com.target.app -l android-ssl-bypass.js --no-pause

Stack	Marker	Hook point
OkHttp 3/4	okhttp3.CertificatePinner	CertificatePinner.check() — return normally
HttpURLConnection	javax.net.ssl.*	Custom X509TrustManager.checkServerTrusted()
Conscrypt	libconscrypt_jni.so	Platform.checkServerTrusted, or the native layer
Apache HttpClient	org.apache.http	SSLSocketFactory verifier
WebView	onReceivedSslError	Force handler.proceed()
Native / BoringSSL	libssl.so, custom .so	SSL_CTX_set_custom_verify, ssl_verify_peer_cert
Xamarin	libmonodroid.so, libxamarin*	Mono-level ServicePointManager / HttpClientHandler
Unity	libil2cpp.so	UnityWebRequest cert handler, or BestHTTP's verifier
gRPC	libgrpc.so	Channel credentials; often also ignores the proxy

Native pinning is where the universal scripts stop working. When objection reports success but traffic still fails, the check is in a .so. BoringSSL's verification entry points are not exported, so scripts locate them by pattern scanning — and the pattern is version-specific. Confirm what you are dealing with:

# Is a native TLS stack even present?
unzip -j target.apk 'lib/arm64-v8a/*' -d libs && rg -l 'SSL_|BoringSSL|s2n' libs/
# Trace the native calls to see which library terminates TLS
frida-trace -U -f com.target.app -i 'SSL_*' -i '*verify*'

For Unity, Xamarin, and Flutter builds, recover symbols first — reversing-unity-il2cpp, reversing-flutter-apps — then hook the named function rather than pattern-scanning blind.

iOS

# Frida-based, covers NSURLSession and the common libraries
objection -g com.target.app explore
# then: ios sslpinning disable

# Jailbroken device, no Frida
# SSL Kill Switch 3 — system-wide, survives app updates

Library	Hook point
NSURLSession (default)	URLSession:didReceiveChallenge: → .useCredential with the server trust
TrustKit	TSKPinningValidator result
AFNetworking	AFSecurityPolicy.evaluateServerTrust:
Alamofire	ServerTrustManager / ServerTrustEvaluating
Native/BoringSSL	Same as Android — hook the verify callback

Non-jailbroken devices: repackage the IPA with the Frida gadget (objection patchipa), re-sign, and sideload. Expect this to trip integrity or attestation checks in hardened apps.

When It Still Fails

Work through these in order rather than trying more bypass scripts.

1. The app never used your proxy. Some stacks ignore system proxy settings entirely. Force traffic: transparent redirect with iptables, or a VPN/tun-based proxy.

   adb shell su -c 'iptables -t nat -A OUTPUT -p tcp --dport 443 -j DNAT --to <proxy>:8080'
   

2. Certificate Transparency enforcement. Some SDKs require SCTs; your CA has none. Look for CT libraries and hook the CT verifier specifically.
3. Mutual TLS. The server demands a client certificate. Extract the .p12 or keystore from the app bundle, recover its password (often in code or strings), and load it into your proxy's client-certificate settings. This is a separate mechanism from pinning and no pinning bypass will touch it.
4. Root/jailbreak or Frida detection. The app detects instrumentation and fails closed, which looks like a TLS problem. Check for a frida string scan, port 27042 probing, /proc/self/maps inspection, or Play Integrity. Bypass the detection first, then retry the pinning bypass.
5. The traffic is not HTTP. WebSockets, gRPC, MQTT, or a custom protocol over TLS. Your HTTP proxy will not show it — capture at the socket layer or with a protocol-aware proxy.
6. Pinning applied only to specific hosts. Analytics flows fine while the API fails. Confirm by comparing which hosts appear in the proxy.

Verify You Actually Won

A bypass is confirmed when you can see and modify a request end to end — not when the app merely stops erroring.

1. Proxy shows the API host, not just analytics and CDN traffic
2. Request and response bodies are readable
3. A modified request produces a different server response
4. Authenticated flows still work through the proxy

If only step 1 passes, you may be seeing a fallback path while the real API traffic goes elsewhere.

Rationalizations to Reject

• "The bypass failed, the app must use strong pinning." Six causes, one of which is pinning. Diagnose from the symptom table.
• "I installed the CA, so TLS should work." As a user certificate, on Android 7+, for an app that does not opt in — it will not.
• "objection said pinning disabled." It disabled the Java-layer checks it knows. Native pinning is untouched.
• "No traffic in the proxy means the app is offline." It means the app is not using your proxy.
• "I'll just patch the APK." Repacking breaks signatures and trips integrity checks. Prefer a system CA and runtime hooks; patch as a last resort.
• "Pinning bypassed, assessment done." Bypassing pinning is setup, not a finding. Pinning is a defense-in-depth control, and its absence is a low severity note — the findings are in the API behind it.

References

• testing-mobile-applications — the wider assessment this unblocks
• reversing-flutter-apps — Flutter's separate TLS stack and proxy behaviour
• reversing-unity-il2cpp, reversing-react-native-apps — symbol recovery before hooking framework-specific stacks
• testing-apis — where the actual findings are, once you can see the traffic
• objection, Frida, SSL Kill Switch 3, apktool, apksigner, Magisk