// Pseudocode of patch bool verifySignature(const char* ipa_path) // Original: call MIGetSignatureStatus() // Patched: always return 0 (success) return 0; // kMISuccess
| Daemon | Process Name | Function Patched | |--------|--------------|------------------| | installd | /usr/libexec/installd | MIInstall::verifySignature | | mobile_installation_proxy | mobile_installation_proxy | validateSignature | The .dylib overrides the return value of signature verification functions: appsync unified deb file
$ dpkg -l | grep appsync ii com.angelxwind.appsyncunified 110.0 iphoneos-arm Check hook injection: Depends: firmware (>
appsync-unified.deb/ ├── DEBIAN/ │ ├── control # Metadata: Package, Version, Architecture, Depends, Conflicts │ ├── preinst # Pre-installation checks (iOS version, jailbreak detection) │ ├── postinst # Post-install hooks (chmod, restart installd) │ ├── prerm # Pre-removal cleanup │ └── postrm # Post-removal restoration ├── Library/ │ └── MobileSubstrate/DynamicLibraries/ │ ├── AppSyncUnified.dylib # Tweak binary (injected into installd) │ └── AppSyncUnified.plist # Filter: com.apple.mobile.installation_proxy, com.apple.installd └── usr/ └── libexec/ └── appsync_patch.dylib # Standalone patch for installd (fallback) Package: com.angelxwind.appsyncunified Version: 110.0 Architecture: iphoneos-arm Maintainer: Karen Tsai <angela@angelxwind.net> Depends: firmware (>= 5.0), mobilesubstrate (>= 0.9.5000), preferenceloader Conflicts: com.iresh.skater.appsync, com.linusyang.appsync Description: Allows unsigned/fakesigned IPA installation. Section: Tweaks 3. Core Mechanism 3.1 Patch Targets AppSync Unified hooks into two key daemons via Cydia Substrate : preferenceloader Conflicts: com.iresh.skater.appsync