UniswapV4KEMHook Manual Review Findings

UVK-01M: Inexistent Restriction of Signature Submitter

Type	Severity	Location
Logical Fault		UniswapV4KEMHook.sol:L124-L135

Description:

The signature validation process in the UniswapV4KEMHook::beforeSwap function will not incorporate the whitelisted sender into the signed payload, permitting any of the multiple whitelisted senders to utilize a single signature.

Impact:

Any whitelisted member can presently utilize any signature as long as it is valid which we consider incorrect.

If signatures were being consumed, this exhibit would have been considered to be of medium severity, however, the present flaw simply permits a higher degree of access than expected.

Example:

Copy
102function beforeSwap(
103  address sender,
104  PoolKey calldata key,
105  IPoolManager.SwapParams calldata params,
106  bytes calldata hookData
107) external view onlyPoolManager returns (bytes4, BeforeSwapDelta, uint24) {
108  require(whitelisted[sender], NonWhitelistedAccount(sender));
109  require(params.amountSpecified < 0, ExactOutputDisabled());
110
111  (
112    int256 maxAmountIn,
113    int256 maxExchangeRate,
114    int256 exchangeRateDenom,
115    uint256 expiryTime,
116    bytes memory signature
117  ) = HookDataDecoder.decodeAllHookData(hookData);
118
119  require(block.timestamp <= expiryTime, ExpiredSignature(expiryTime, block.timestamp));
120  require(
121    -params.amountSpecified <= maxAmountIn,
122    ExceededMaxAmountIn(maxAmountIn, -params.amountSpecified)
123  );
124  require(
125    SignatureChecker.isValidSignatureNow(
126      quoteSigner,
127      keccak256(
128        abi.encode(
129          key, params.zeroForOne, maxAmountIn, maxExchangeRate, exchangeRateDenom, expiryTime
130        )
131      ),
132      signature
133    ),
134    InvalidSignature()
135  );
136
137  return (this.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0);
138}

Recommendation:

We advise the sender to be incorporated into the signed payload so as to prevent the consumption of signatures meant for different senders.

Alleviation:

The sender has been incorporated within the signature payload itself, rendering the original whitelisted enforcement redundant and alleviating the vulnerability described.

UVK-02M: Inexistent Consumption of Signature

Type	Severity	Location
Logical Fault		UniswapV4KEMHook.sol:L124-L135

Description:

The quoteSigner signature can be replayed indefinitely before its expiryTime as it is not consumed.

Impact:

A signed payload can be repeated an infinite number of times, effectively bypassing the maxAmountIn restriction.

Example:

Copy
124require(
125  SignatureChecker.isValidSignatureNow(
126    quoteSigner,
127    keccak256(
128      abi.encode(
129        key, params.zeroForOne, maxAmountIn, maxExchangeRate, exchangeRateDenom, expiryTime
130      )
131    ),
132    signature
133  ),
134  InvalidSignature()
135);
136
137return (this.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0);

Recommendation:

We advise the signature to be marked as consumed by utilizing a nonce per quoteSigner, preventing signature replay attacks.

Alleviation:

An UnorderedNonce implementation has been introduced to the codebase that permits nonces to be marked as consumed, allowing nonces to be incorporated to the signed payload consumed for each UniswapV4KEMHook::beforeSwap operation.