Summary
The IBlockHashRetain.vyi interface's block hash retention mechanism is vulnerable to manipulation through MEV and validator collusion. This creates opportunities for malicious actors to influence oracle prices.
Vulnerability Details
The current implementation allows block hash commitments without proper validation:
@external
def commit() -> uint256:
"""
@notice Commit (and apply) a block hash/state root.
@dev Same as `apply()` but saves committer
"""
# No MEV protection
# No validator collusion prevention
# No minimum confirmation checks
...
@external
def apply() -> uint256:
"""
@notice Apply a block hash/state root.
"""
# No price deviation checks
# No timestamp validation
# No sandwich attack protection
...
Attack vectors:
MEV searchers can front-run commits
Validators can manipulate block hashes
No minimum confirmations required
Missing price deviation bounds
Vulnerable to sandwich attacks
Impact
Price manipulation possible
Unfair liquidations
MEV extraction
System-wide price oracle manipulation
Financial losses for users
Tools Used
Manual Review
MEV simulation analysis
Recommendations
Implement MEV protection:
struct CommitmentWindow:
start_block: uint256
end_block: uint256
min_confirmations: uint256
max_deviation: uint256
# Commitment windows
current_window: public(CommitmentWindow)
next_window: public(CommitmentWindow)
@external
def initialize_commitment_windows():
"""
@notice Initialize commitment windows with MEV protection
"""
self.current_window = CommitmentWindow({
start_block: block.number,
end_block: block.number + 100,
min_confirmations: 12,
max_deviation: 100 # 1% max deviation
})
Add price deviation checks:
struct PricePoint:
value: uint256
timestamp: uint256
confirmations: uint256
validator_count: uint256
price_history: public(HashMap[uint256, PricePoint])
@view
@external
def validate_price(_new_price: uint256) -> bool:
"""
@notice Validate price against historical data
"""
last_price: PricePoint = self.price_history[block.number - 1]
# Check minimum confirmations
if last_price.confirmations < self.current_window.min_confirmations:
return False
# Calculate deviation
max_change: uint256 = last_price.value * self.current_window.max_deviation / 10000
if abs(_new_price - last_price.value) > max_change:
return False
return True
@internal
def _calculate_twap(_start_block: uint256, _end_block: uint256) -> uint256:
"""
@notice Calculate TWAP to prevent manipulation
"""
assert _end_block > _start_block, "Invalid blocks"
assert _end_block - _start_block <= 100, "Too long interval"
total: uint256 = 0
count: uint256 = 0
for block_number in range(_start_block, _end_block + 1):
price_point: PricePoint = self.price_history[block_number]
if price_point.validator_count >= self.current_window.min_confirmations:
total += price_point.value
count += 1
assert count > 0, "No valid prices"
return total / count
Implement sandwich attack protection:
struct TransactionGuard:
min_blocks_before: uint256
min_blocks_after: uint256
max_price_impact: uint256
tx_guard: public(TransactionGuard)
@external
def set_transaction_guard(_guard: TransactionGuard):
"""
@notice Set transaction guard parameters
"""
assert msg.sender == self.admin, "Not admin"
assert _guard.min_blocks_before > 0, "Invalid before blocks"
assert _guard.min_blocks_after > 0, "Invalid after blocks"
self.tx_guard = _guard
@view
@external
def is_transaction_safe(_price: uint256, _block_number: uint256) -> bool:
"""
@notice Check if transaction is safe from sandwich attacks
"""
guard: TransactionGuard = self.tx_guard
# Check blocks before
before_price: uint256 = self._calculate_twap(
_block_number - guard.min_blocks_before,
_block_number - 1
)
# Check blocks after
after_price: uint256 = self._calculate_twap(
_block_number + 1,
_block_number + guard.min_blocks_after
)
# Calculate price impact
max_impact: uint256 = _price * guard.max_price_impact / 10000
return (
abs(before_price - _price) <= max_impact and
abs(after_price - _price) <= max_impact
)
Add validator consensus requirements:
struct ValidatorConsensus:
min_validators: uint256
consensus_threshold: uint256
max_staleness: uint256
consensus_config: public(ValidatorConsensus)
validator_submissions: public(HashMap[uint256, HashMap[address, uint256]])
@external
def submit_price(_block_number: uint256, _price: uint256) -> bool:
"""
@notice Submit price with validator consensus
"""
assert self.is_validator[msg.sender], "Not validator"
assert block.number - _block_number <= self.consensus_config.max_staleness, "Stale"
self.validator_submissions[_block_number][msg.sender] = _price
# Check consensus
if self._check_price_consensus(_block_number, _price):
self._finalize_price(_block_number, _price)
return True
return False
@view
@internal
def _check_price_consensus(_block_number: uint256, _price: uint256) -> bool:
"""
@notice Check if price has reached consensus
"""
consensus_count: uint256 = 0
for validator in self.validators:
if self.validator_submissions[_block_number][validator] == _price:
consensus_count += 1
return (
consensus_count >= self.consensus_config.min_validators and
consensus_count * 100 >= self.validator_count * self.consensus_config.consensus_threshold
)
These enhancements provide:
MEV protection mechanisms
Price deviation controls
Sandwich attack prevention
Validator consensus requirements
TWAP calculations
Staleness checks
