Feat/stx validator

[filmakarov]

StxValidator: Modular ERC-7579 Validator for MEE SuperTransactions

Overview

This PR introduces StxValidator, a next-generation ERC-7579 compatible validator module that replaces the legacy K1MeeValidator with a modular, extensible architecture designed for validating MEE (Modular Execution Environment) SuperTransactions.

Key Innovation: While K1MeeValidator was tightly coupled to secp256k1 (EOA) signatures, StxValidator implements a signature-agnostic architecture that supports multiple signing schemes including EOA, Passkeys (P256/secp256r1), Safe multisig, and any custom signature format implementing ERC-7780.

What are MEE SuperTransactions?

MEE SuperTransactions (Stx) are versatile data structures that enable users to execute complex, multi-chain operations with a single signature. They can contain:

• Multiple ERC-4337 UserOperations
• Arbitrary signed EIP-712 data structures (intents, off-chain orders, permits)
• Cross-chain instructions with "elegant degradation" across execution environments

StxValidator validates both the UserOps and arbitrary signed data objects that comprise these SuperTransactions.

Architecture

Two-Layer Modular Design

StxValidator implements a clean separation of concerns through two distinct validation layers:

1️⃣ Stx Mode Verification (IStxModeVerifier)

Validates that a UserOp or data object is part of a SuperTransaction. Supported modes:

• Simple Mode (SimpleModeSubmodule.sol) - Direct EIP-712 signing of SuperTx struct
• Permit Mode (PermitSubmodule.sol) - ERC-2612 permit with Stx hash embedded in deadline field (gasless transactions)
• Tx Mode (TxSubmodule.sol) - On-chain transaction with Stx hash appended to calldata
• Safe Account Mode (SafeAccountSubmodule.sol) - Safe multisig transaction as trigger
• No-Stx Mode (NoStxModeVerifier.sol) - Fallback for vanilla ERC-4337 and ERC-1271 flows

2️⃣ Signature Verification (IStatelessValidator / ERC-7780)

Cryptographic validation of signatures, fully decoupled from signing scheme:

• EOA (secp256k1) (EOAStatelessValidator.sol) - Traditional Ethereum signatures
• Passkeys (P256/secp256r1) (P256StatelessValidator.sol) - WebAuthn/Passkey support with RIP-7212 precompile + Solidity fallback
• Safe Multisig - Built into SafeAccountSubmodule
• Custom Validators - Any contract implementing IStatelessValidator

Configuration Management

The validator uses a flexible per-account configuration system (ConfigManager.sol):

• Preconfigured Signature Types: Common combinations (EOA+Simple, P256+Simple, etc.) use optimized 4-byte prefixes
• Custom Configs: Accounts can enable custom (stxModeVerifier, statelessValidator) pairs via configId
• Multiple Configs: Each account can enable multiple validation strategies simultaneously
• Ownership Data: Per-account, per-validator storage for public keys/credentials

Major Changes

🗑️ Removed

• ❌ K1MeeValidator.sol - Replaced by modular StxValidator
• ❌ Legacy validation mode libraries (NoMeeFlowLib, PermitValidatorLib, SafeAccountValidatorLib, SimpleValidatorLib)

✨ Added

Core Validator

• ✅ StxValidator.sol - Main validator contract with ERC-7579, ERC-7780, and ERC-7739 support
• ✅ ConfigManager.sol - Flexible configuration management system
• ✅ ERC7739Validator.sol - Native ERC-7739 nested typed data sign support

Stx Mode Verifiers

• ✅ SimpleModeSubmodule.sol - Simple mode implementation
• ✅ PermitSubmodule.sol - Permit mode with ERC-2612 integration
• ✅ TxSubmodule.sol - On-chain transaction mode
• ✅ SafeAccountSubmodule.sol - Safe multisig mode (dual IStxModeVerifier + IStatelessValidator)
• ✅ NoStxModeVerifier.sol - Fallback for non-Stx flows

Stateless Validators

• ✅ EOAStatelessValidator.sol - EOA signature verification (secp256k1)
• ✅ P256StatelessValidator.sol - Passkey signature verification (secp256r1)
• ✅ P256Verifier.sol - Solidity implementation of P256 curve (Daimo's FCL library)

Interfaces

• ✅ IStxModeVerifier.sol - Interface for Stx mode verification modules
• ✅ IERC7739Multiplexer.sol - Interface for ERC-7739 hash/signature multiplexing

🔄 Modified

• HashLib.sol - Enhanced to support new modular architecture
• MEEUserOpHashLib.sol - Updated for new UserOp hashing flows
• EcdsaHelperLib.sol - Signature malleability fixes
• Constants.sol - New signature type constants for all mode combinations

Testing

Comprehensive test coverage with 23 test files covering:

End-to-End Tests

• ✅ All Stx modes (Simple, Permit, Tx, Safe Account, No-Stx)
• ✅ Multi-chain scenarios (Simple Mode)
• ✅ P256 passkey integration
• ✅ Fork tests against live Safe deployments

Unit Tests

• ✅ Configuration management (add, replace, delete configs)
• ✅ Signature type routing
• ✅ ERC-7739 multiplexer
• ✅ Module initialization/uninstallation
• ✅ Safe senders management
• ✅ Individual submodule validation logic
• ✅ Ownership data management

Test Structure: Reorganized from test/unit/ to test/unit-and-e2e/ to better reflect test types.

Key Features

🔐 Signature Agnostic

Unlike K1MeeValidator (EOA-only), StxValidator supports:

• Traditional EOA wallets
• Passkey/WebAuthn (P256) - enabling passwordless authentication
• Safe multisig wallets
• Any custom signature scheme via ERC-7780

🎯 Modular & Extensible

• Plug-and-play Stx mode verifiers
• Plug-and-play signature validators
• Easy to add new modes or signature schemes without touching core logic

🌐 ERC-7739 Support

Full nested typed data sign support for:

• Safe caller detection (MulticallerWithSigner)
• Nested EIP-712 workflow
• RPC-based signature validation
• Custom safe senders registry

⚙️ Flexible Configuration

• Multiple validation strategies per account
• Runtime config management (add/replace/delete)
• Preconfigured common patterns with optimized gas
• Support for custom configurations

🔄 Backwards Compatible

• Maintains support for vanilla ERC-4337 UserOps (via NoStxModeVerifier)
• ERC-1271 signature validation without Stx (via signature type 0x177eee05)
• EIP-7702 delegation support for EOA smart accounts

Deployment

Updated deployment scripts with:

• ✅ All submodule deployments
• ✅ Deterministic deployment via Safe Singleton Deployer
• ✅ Comprehensive artifact generation
• ✅ Multi-chain deployment support

Deployment Artifacts: See script/deploy/artifacts/stx-validator/ for all deployed contract addresses and verification data.

Migration from K1MeeValidator

For existing users of K1MeeValidator:

1. Same Modes Supported: All existing MEE modes are preserved (Simple, Permit, Tx, Safe Account)
2. Enhanced Capabilities: Now with P256/Passkey support
3. Same Integration: ERC-7579 compatible, drop-in replacement
4. New Features: Multiple configs, ERC-7739, better modularity

Related Standards & Documentation

• ERC-7579: Minimal Modular Smart Accounts
• ERC-7780: Stateless Signature Validators
• ERC-7739: Nested Typed Data Sign
• RIP-7212: Precompile for secp256r1 Curve Support
• MEE Specification
• Elegant Degradation
• Biconomy Network Launch

Statistics

• 193 files changed: 10,540 insertions(+), 2,005 deletions(-)
• 23 comprehensive test files
• 8 new submodules implementing modular architecture
• 7 deployment artifacts for all submodules

Breaking Changes

⚠️ K1MeeValidator.sol has been removed. Users should migrate to StxValidator which provides all the same functionality plus extensibility for additional signature types.

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Checklist

• All MEE modes implemented and tested
• P256/Passkey support added
• Comprehensive unit and E2E tests
• Deployment scripts updated
• ERC-7739 support implemented
• Configuration management system
• Documentation and NatSpec complete
• Gas optimizations applied
• Security considerations addressed

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This PR represents a significant architectural improvement that positions the validator for future extensibility while maintaining full backwards compatibility with existing MEE SuperTransaction flows.