""" ERC20 Token Transfer Validator Validates that an ERC20 token transfer transaction is correctly executed """ from typing import Dict, Any class ERC20TransferValidator: """Validator for ERC20 token transfers""" def __init__(self, token_address: str, to_address: str, amount: float, token_decimals: int = 18): """ Initialize validator Args: token_address: ERC20 token contract address to_address: Expected recipient address amount: Expected transfer amount in tokens (float) token_decimals: Token decimals (default: 18) """ from decimal import Decimal self.expected_token = token_address.lower() self.expected_to = to_address.lower() # Convert token amount to smallest unit self.expected_amount = int(Decimal(str(amount)) * Decimal(10 ** token_decimals)) self.token_decimals = token_decimals self.max_score = 100 def validate( self, tx: Dict[str, Any], receipt: Dict[str, Any], state_before: Dict[str, Any], state_after: Dict[str, Any] ) -> Dict[str, Any]: """ Validate the transaction execution results Args: tx: Transaction object receipt: Transaction receipt state_before: Blockchain state before transaction state_after: Blockchain state after transaction Returns: Validation results including score and details """ score = 0 details = {} checks = [] # Check 1: Transaction success (30 points) tx_success = receipt.get('status') == 1 if tx_success: score += 30 checks.append({ 'name': 'Transaction Success', 'passed': True, 'points': 30, 'message': 'Transaction executed successfully' }) else: checks.append({ 'name': 'Transaction Success', 'passed': False, 'points': 0, 'message': f"Transaction failed with status: {receipt.get('status')}" }) return { 'score': score, 'max_score': self.max_score, 'passed': False, 'checks': checks, 'details': details } # Check 2: Contract address correct (20 points) actual_to = tx.get('to', '').lower() contract_correct = actual_to == self.expected_token if contract_correct: score += 20 checks.append({ 'name': 'Contract Address', 'passed': True, 'points': 20, 'message': f'Correct token contract: {self.expected_token}' }) else: checks.append({ 'name': 'Contract Address', 'passed': False, 'points': 0, 'message': f'Expected: {self.expected_token}, Got: {actual_to}' }) details['expected_token'] = self.expected_token details['actual_to'] = actual_to # Check 3: Function signature (20 points) # ERC20 transfer function selector: 0xa9059cbb (first 4 bytes of keccak256("transfer(address,uint256)")) tx_data = tx.get('data', '0x') if tx_data and len(tx_data) >= 10: # 0x + 8 hex chars (4 bytes) function_selector = tx_data[:10].lower() expected_selector = '0xa9059cbb' # transfer(address,uint256) if function_selector == expected_selector: score += 20 checks.append({ 'name': 'Function Signature', 'passed': True, 'points': 20, 'message': 'Correct ERC20 transfer function signature' }) # Decode parameters from data try: # Data format: 0x + function_selector (8 chars) + address (64 chars) + amount (64 chars) if len(tx_data) >= 138: # 0x(2) + selector(8) + address(64) + amount(64) = 138 recipient_hex = tx_data[10:74] # Skip 0x and selector amount_hex = tx_data[74:138] # Convert to addresses and amounts recipient_address = '0x' + recipient_hex[-40:] # Last 40 chars (20 bytes) amount_value = int(amount_hex, 16) details['decoded_recipient'] = recipient_address.lower() details['decoded_amount'] = amount_value except Exception as e: details['decode_error'] = str(e) else: checks.append({ 'name': 'Function Signature', 'passed': False, 'points': 0, 'message': f'Expected: {expected_selector}, Got: {function_selector}' }) else: checks.append({ 'name': 'Function Signature', 'passed': False, 'points': 0, 'message': 'No data field or too short' }) details['function_selector'] = tx_data[:10] if tx_data else None # Check 4: Token balance changes (30 points) sender_balance_before = state_before.get('token_balance', 0) sender_balance_after = state_after.get('token_balance', 0) receiver_balance_before = state_before.get('target_token_balance', 0) receiver_balance_after = state_after.get('target_token_balance', 0) sender_change = sender_balance_after - sender_balance_before receiver_change = receiver_balance_after - receiver_balance_before # Check if changes match expected sender_correct = sender_change == -self.expected_amount receiver_correct = receiver_change == self.expected_amount if sender_correct and receiver_correct: score += 30 checks.append({ 'name': 'Token Balance Changes', 'passed': True, 'points': 30, 'message': f'Correct token balance changes: -{self.expected_amount} (sender), +{self.expected_amount} (receiver)' }) else: # Balance changes incorrect - no partial credit for consistency error_parts = [] if not sender_correct: error_parts.append(f'Sender: expected -{self.expected_amount}, got {sender_change}') if not receiver_correct: error_parts.append(f'Receiver: expected +{self.expected_amount}, got {receiver_change}') checks.append({ 'name': 'Token Balance Changes', 'passed': False, 'points': 0, 'message': ' | '.join(error_parts) if error_parts else 'Balance changes incorrect' }) details['sender_balance_before'] = sender_balance_before details['sender_balance_after'] = sender_balance_after details['sender_change'] = sender_change details['receiver_balance_before'] = receiver_balance_before details['receiver_balance_after'] = receiver_balance_after details['receiver_change'] = receiver_change details['expected_amount'] = self.expected_amount # Final result passed = score >= self.max_score * 0.8 # 80% threshold return { 'score': score, 'max_score': self.max_score, 'passed': passed, 'checks': checks, 'details': details }