SMSC Guard

Deterministic, privacy-first Android LSPosed module that guarantees correct Short Message Service Center (SMSC) routing on dual-SIM devices.

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Overview

On dual-SIM Android smartphones, modern messaging applications and telephony frameworks frequently suffer from silent SMS dispatch failures. When sending text messages from secondary SIM slots, the system may inadvertently query the active data SIM's Service Center Address (SMSC) or supply an empty routing address, resulting in carrier error code 28/38 or silent transmission drops.

SMSC Guard (io.github.lonevertex.smscguard) resolves this by intercepting public android.telephony.SmsManager dispatch calls at the framework level via LSPosed. It deterministically verifies the active subscription and physical SIM slot, maps it to the verified carrier SMSC, and replaces the routing address in-flight before the packet reaches the Radio Interface Layer (RIL).

If carrier signals are conflicting or slot evidence is indeterminate, SMSC Guard enforces a strict fail-safe preservation policy: the original SMSC is never modified or guessed.

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Architectural Highlights

• Libxposed API 102 Native: Completely modernized to io.github.libxposed:api:102.0.0 and service:102.0.0, leveraging protective exception modes, modern dex hook engines, and OkHttp-style composable interceptor chains (SmscGuardModule.kt).
• Secure Service-Based IPC: Permanently eliminates deprecated xposedsharedprefs and obsolete Context.MODE_WORLD_READABLE filesystem permissions. Cross-process configuration is synchronized via io.github.libxposed.service.XposedProvider and RemotePreferences.
• Zero-Dependency Reflection Engine (ReflectUtils): Clean separation from legacy XposedHelpers. Built on thread-safe, cached Java reflection with comprehensive primitive-to-wrapper assignability and null-argument resolution.
• Material 3 Dynamic Settings UI: A modern Jetpack Compose dashboard (SettingsDashboard.kt, SettingsViewModel.kt) supporting dynamic theming (Material You), live LSPosed framework connection telemetry badges, per-slot E.164 phone number validation, and target scope management.
• Privacy by Design (Zero PII): SMS message content, recipient phone numbers, IMSI/IMEI, and personal data are never inspected, captured, or logged. Diagnostic logs are strictly redacted and throttled.
• Hermetic Testing Gate: Verified by 81 automated unit tests, strict Android Lint analysis, and signed release verification scripts.

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Default Carrier Configuration

While fully customizable for any worldwide carrier, SMSC Guard comes pre-configured with default values for Egyptian dual-SIM setups:

SIM Slot	Default Carrier	Default SMSC (E.164)	MCC / MNC
SIM 1 (Slot 0)	Vodafone Egypt	+20105996500	602 02
SIM 2 (Slot 1)	Orange Egypt	+20122000020	602 01

Custom carrier addresses can be entered directly in the settings dashboard using international E.164 notation (e.g. +1..., +44..., +20...).

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Installation & Setup

Prerequisites

1. Rooted Android device running Android 5.0 (API 21) up to Android 16 Developer Preview (Platform API 36).
2. An active LSPosed framework installation (e.g., LSPosed or modern Zygisk-based variants).

Quick Start

1. Download the latest official signed release APK (smscguard-v2.1.0-release-signed.apk) from GitHub Releases.
2. Install the APK onto your device.
3. Open LSPosed Manager, navigate to the Modules tab, and toggle SMSC Guard ON.
4. LSPosed Manager will automatically detect the declared xposedscope and pre-select the recommended applications (System Framework (android), Google Messages (com.google.android.apps.messaging), and MMS (com.android.mms)). Confirm the scope or add custom OEM messaging packages if applicable.
5. Open SMSC Guard from your app launcher.
6. Verify the LSPosed Active status badge in the header, review your per-slot SMSC numbers, and tap Save Configuration.
7. Reboot your device or restart the scoped processes to activate hooks.

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Cryptographic Release Verification

All official production builds are signed using a dedicated 4096-bit RSA release key. You can independently verify the integrity and authenticity of downloaded APKs:

# Verify signature schemes (v1, v2, v3) and certificate fingerprint
apksigner verify --verbose --print-certs smscguard-v2.1.0-release-signed.apk

Official Signer Certificate Identity:

Signer #1 certificate DN: CN=LoneVertex, OU=Android Security, O=LoneVertex, C=EG
Signer #1 key algorithm: RSA 4096-bit
Signer #1 certificate SHA-256: 80:5F:3E:1F:6C:04:E5:A2:0F:10:20:54:85:E7:E5:F0:72:E1:E9:EE:CA:F4:06:92:E5:5C:DB:2D:34:FD:29:53
Signer #1 certificate SHA-1:   DB:13:52:64:A2:8F:40:C7:7A:DE:E4:15:26:E2:11:F3:95:14:C0:C4

v2.1.0 Artifact Checksums

a2ba366c924892d5350626c59301bdc5eec6f57957e178d6a68b91450fc43bda  smscguard-v2.1.0-release-signed.apk
d8765a6adacfe309058491755caaf35ed20165c482545b970049359bedaae06f  app-release-unsigned.apk
932dcfdad129fd70b74f46c940c0838891a3323c551cb8d04c03f7f34f8de949  smscguard-v2.1.0-debug.apk
cc153281882b5a61f82c135a5efa73caa3a6357e7158d8ef9054c2390692f9db  smscguard-release-candidate.json

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Building from Source

Requirements

• JDK: OpenJDK 17 or Eclipse Temurin 17
• Android SDK: Platform API 36 with Build-Tools 35.0.0+
• Gradle: 8.6 (managed automatically via ./gradlew)

Build Commands

# Clone the repository
git clone git@github.com:LoneVertex/SMSCFixer.git
cd SMSCFixer

# Run Android Lint, hermetic unit tests, and compile debug & release candidate APKs
./gradlew --no-daemon clean lint test assembleDebug assembleRelease assembleDebugAndroidTest

Outputs are generated under app/build/outputs/apk/:

• debug/app-debug.apk: Debug build with live debug logging.
• release/app-release-unsigned.apk: Unsigned release candidate.
• androidTest/debug/app-debug-androidTest.apk: Instrumentation test APK.

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Verification & Testing

Automated Quality Gate

The repository enforces a 100% hermetic unit testing gate covering all critical components:

./gradlew --no-daemon testDebugUnitTest

Test Class	Focus Area
SmscGuardHookInterceptorTest	LSPosed interceptor execution, short-circuiting, and argument replacement
RoutingSignalResolverTest	Cached reflection resolution of SIM slot / subId signals
ReflectUtilsTest	Cache concurrency, null safety, and method signature matching
SmscSelectorBoundaryTest	Dual-SIM boundary conditions, whitespace, and carrier normalizations
SmscConfigSecurityTest	Strict E.164 boundary validation and injection attack prevention
DiagnosticLoggerConcurrencyTest	Throttled memory ring buffer and multithreaded log safety
SettingsUiLogicTest	Jetpack Compose ViewModel state, telemetry transitions, and validation
BoundedTtlCacheTest	LRU eviction policies and TTL expiry

Smoke Testing on Rooted Devices

To run production-like verification on a connected rooted Android test device:

# Run non-interactive smoke test suite
./scripts/smoke_test_prod_like.sh --non-interactive

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Repository Structure

SMSCFixer/
├── app/
│   ├── src/main/
│   │   ├── java/io/github/lonevertex/smscguard/
│   │   │   ├── SmscGuardModule.kt          # Libxposed API 102 entry point & hook chains
│   │   │   ├── PreferencesManager.kt       # XposedService IPC & RemotePreferences StateFlow
│   │   │   ├── SettingsDashboard.kt        # Jetpack Compose Material 3 UI root
│   │   │   ├── SettingsViewModel.kt        # UI telemetry, state & validation logic
│   │   │   ├── ReflectUtils.java           # Zero-dependency cached Java reflection engine
│   │   │   ├── RoutingSignalResolver.java  # Reflection-based SIM slot signal resolver
│   │   │   ├── SmscConfigSchema.java       # Canonical schema keys & E.164 validation
│   │   │   ├── SmscSelector.java           # Core carrier routing decision policy
│   │   │   └── ui/components/              # Modular Compose UI cards & theme tokens
│   │   └── resources/META-INF/xposed/
│   │       ├── module.prop                 # API 102 module descriptor
│   │       ├── java_init.list              # Entry point registration
│   │       └── scope.list                  # Target process scope allowlist
│   └── src/test/                           # 81 hermetic unit test suites
├── docs/                                   # Architecture, security, operations & audit docs
│   ├── operations/                         # Device compatibility registry & runbooks
│   ├── production/                         # Migration & rollback evidence
│   ├── security/                           # Threat models & configuration sharing ADRs
│   └── testing/                            # Test strategies & validation matrices
├── scripts/                                # Verification, release, and signing scripts
├── .github/                                # GitHub Actions CI, release workflows & issue forms
├── CHANGELOG.md                            # Complete version changelog
├── CONTRIBUTING.md                         # Contributor onboarding & PR guidelines
├── CODE_OF_CONDUCT.md                      # Contributor Covenant v2.1
├── SECURITY.md                             # Vulnerability disclosure policy
└── LICENSE                                 # MIT License

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Community & Contributing

Contributions are welcome! Please review our Contributing Guidelines and Code of Conduct before opening issues or submitting pull requests.

• Found a bug? Submit a Bug Report.
• Need a new carrier preset? Request one via Feature Request.
• Verified a device or ROM? Help others by submitting a Device Compatibility Report.

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Security & Privacy

For vulnerability reporting procedures, please consult our Security Policy.

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License

SMSC Guard is licensed under the MIT License.
Copyright © 2026 LoneVertex. All rights reserved.