""" ERC20 Transfer Max Amount Validator Validates that the entire ERC20 token balance was transferred """ from typing import Dict, Any class ERC20TransferMaxAmountValidator: """Validator for ERC20 maximum amount transfer""" def __init__(self, token_address: str, to_address: str, token_decimals: int = 18): """ Initialize validator Args: token_address: ERC20 token contract address to_address: Expected recipient address token_decimals: Token decimal places (default 18) """ self.expected_token = token_address.lower() self.expected_recipient = to_address.lower() 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: Token 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': 'Token Contract', 'passed': True, 'points': 20, 'message': f'Correct token contract: {self.expected_token}' }) else: checks.append({ 'name': 'Token Contract', '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 (10 points) # ERC20 transfer function selector: 0xa9059cbb (keccak256("transfer(address,uint256)")) tx_data = tx.get('data', '0x') if tx_data and len(tx_data) >= 10: function_selector = tx_data[:10].lower() expected_selector = '0xa9059cbb' # transfer(address,uint256) if function_selector == expected_selector: score += 10 checks.append({ 'name': 'Function Signature', 'passed': True, 'points': 10, 'message': 'Correct ERC20 transfer function signature' }) # Decode parameters from data try: if len(tx_data) >= 138: # 0x(2) + selector(8) + to(64) + amount(64) = 138 to_hex = tx_data[10:74] # Next 64 chars (32 bytes) amount_hex = tx_data[74:138] # Next 64 chars (32 bytes) # Extract address (last 40 hex chars of the 64 char field) to_addr = '0x' + to_hex[-40:].lower() amount_value = int(amount_hex, 16) details['decoded_to'] = to_addr details['decoded_amount'] = amount_value # Verify recipient address if to_addr == self.expected_recipient: details['recipient_address_correct'] = True else: details['recipient_address_correct'] = False details['recipient_mismatch'] = f'Expected: {self.expected_recipient}, Got: {to_addr}' 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: Maximum amount transferred (20 points) # Transfer amount should equal the initial balance balance_before = state_before.get('token_balance', 0) balance_after = state_after.get('token_balance', 0) # The transferred amount (from balance decrease) actual_transferred = balance_before - balance_after # Expected max transfer = entire balance expected_max_transfer = balance_before # Allow small tolerance (0.1% or 1 token unit, whichever is larger) tolerance = max(int(expected_max_transfer * 0.001), 1) transfer_correct = abs(actual_transferred - expected_max_transfer) <= tolerance if transfer_correct: score += 20 checks.append({ 'name': 'Maximum Amount Transferred', 'passed': True, 'points': 20, 'message': f'Transferred entire balance: {actual_transferred / 10**self.token_decimals:.6f} tokens' }) else: checks.append({ 'name': 'Maximum Amount Transferred', 'passed': False, 'points': 0, 'message': f'Expected: {expected_max_transfer / 10**self.token_decimals:.6f} tokens, Transferred: {actual_transferred / 10**self.token_decimals:.6f} tokens' }) details['balance_before'] = balance_before details['expected_max_transfer'] = expected_max_transfer details['actual_transferred'] = actual_transferred # Check 5: Sender balance zero or minimal (20 points) # After transferring max amount, balance should be 0 or very close to 0 # Allow up to 0.01 tokens remaining (10^(decimals-2)) max_remaining = 10**(self.token_decimals - 2) balance_minimal = balance_after <= max_remaining if balance_minimal: score += 20 checks.append({ 'name': 'Sender Balance Minimal', 'passed': True, 'points': 20, 'message': f'Sender token balance minimal: {balance_after / 10**self.token_decimals:.10f} tokens (< 0.01)' }) else: checks.append({ 'name': 'Sender Balance Minimal', 'passed': False, 'points': 0, 'message': f'Sender balance too high: {balance_after / 10**self.token_decimals:.6f} tokens (should be < 0.01)' }) details['balance_after'] = balance_after details['max_remaining_allowed'] = max_remaining # 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 }