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code-423n4 / 2023-01-biconomy-findings

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Allows malleable `SECP256K1` signatures #453

Closed code423n4 closed 1 year ago

code423n4 commented 1 year ago

Lines of code

https://github.com/code-423n4/2023-01-biconomy/blob/53c8c3823175aeb26dee5529eeefa81240a406ba/scw-contracts/contracts/smart-contract-wallet/paymasters/verifying/singleton/VerifyingSingletonPaymaster.sol#L107 https://github.com/code-423n4/2023-01-biconomy/blob/53c8c3823175aeb26dee5529eeefa81240a406ba/scw-contracts/contracts/smart-contract-wallet/interfaces/IERC1271Wallet.sol#L18 https://github.com/code-423n4/2023-01-biconomy/blob/53c8c3823175aeb26dee5529eeefa81240a406ba/scw-contracts/contracts/smart-contract-wallet/interfaces/IERC1271Wallet.sol#L34 https://github.com/code-423n4/2023-01-biconomy/blob/53c8c3823175aeb26dee5529eeefa81240a406ba/scw-contracts/contracts/smart-contract-wallet/SmartAccount.sol#L347-L350

Vulnerability details

Impact

It is possible to use compact signatures and this allows malleability of the signature.

Description

Here, the ecrecover() method doesn't check the s range and also compact signatures must not be allowed in order to prevent signature malleability.

Homestead (EIP-2) added this limitation, however the precompile remained unaltered. The majority of libraries, including OpenZeppelin, do this check.

Since an order can only be confirmed once and its hash is saved, there doesn't seem to be a serious danger in existing use cases.

Reference:

Affected source code:

Additionally, the following interfaces are susceptible to being implemented incorrectly:

ecrecover:

Recommended Mitigation Steps

As Open Zeppelin did, it's better to remove the compact signatures features.

c4-judge commented 1 year ago

gzeon-c4 marked the issue as primary issue

gzeoneth commented 1 year ago

194 suggested the OZ lib used prevented this from happening

c4-judge commented 1 year ago

gzeon-c4 marked the issue as unsatisfactory: Invalid