[LZR-01C] Cross-Chain Amount Truncation

[dkuppitz]

LZR-01C: Cross-Chain Amount Truncation

Type	Severity	Location
Code Style		LayerZeroRebaseTokenUpgradeable.sol:L154, L159

Description:

The SendToChain event's amount emitted during the LayerZeroRebaseTokenUpgradeable::_send function may not be equal to the actual amount transferred by the function due to potential truncation in the LayerZeroRebaseTokenUpgradeable::_debitFrom function.

Impact:

In contrast to the EIP-20 related exhibit, this one relates to a custom event and thus is of minimal impact.

Example:

Message memory message = Message({
    shares: _debitFrom(from, dstChainId, toAddress, amount),
    rebaseIndex: rebaseIndex(),
    nonce: _rebaseNonce()
});

emit SendToChain(dstChainId, from, toAddress, amount);

Recommendation:

We advise the amount value emitted in the SendToChain event within LayerZeroRebaseTokenUpgradeable::_send to be set to the message.shares.toTokens(message.rebaseIndex) value, ensuring that the amount emitted matches the actual one transferred by the cross-chain transfer.

[dkuppitz]

Resolved in 33a61b3.