Beanstalk: The Finale
Beanstalk
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250,000 USDC
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Submission Details
Severity: high
Invalid

publisher would be drained once set

kodyvim

Summary

LibTractor._user() always returns publisher address once the address have been set.

Vulnerability Details

TokenFaucet uses LibTractor._user() to determine the context of the msg.sender.
The issue is that when a publisher is set the function always returns the address of the publisher instead of the current msg.sender.
https://github.com/Cyfrin/2024-05-beanstalk-the-finale/blob/main/protocol/contracts/libraries/LibTractor.sol#L116C4-L121C6

function _user() internal view returns (address payable user) {
user = _getActivePublisher();//@audit-info once a publisher is set this always return here
if (uint160(bytes20(address(user))) <= 1) {
user = payable(msg.sender);
}
}

The consequence is that when a users calls any functions that depends on LibTractor._user() this would return the address of the publisher.
https://github.com/Cyfrin/2024-05-beanstalk-the-finale/blob/main/protocol/contracts/beanstalk/farm/TokenFacet.sol#L67

function transferInternalTokenFrom(
IERC20 token,
address sender,
address recipient,
uint256 amount,
LibTransfer.To toMode
) external payable fundsSafu noSupplyChange oneOutFlow(address(token)) nonReentrant {
LibTransfer.transferToken(
token,
sender,
recipient,
amount,
LibTransfer.From.INTERNAL,
toMode
);
​
if (sender != LibTractor._user()) {//@audit-info
LibTokenApprove.spendAllowance(sender, LibTractor._user(), token, amount);
}
}

in the above case if the user passes the address of the publisher as sender it would bypass the check(sender != LibTractor._user()) and the spendAllowance would not be invoked.
Multiple functions which depends on LibTractor._user() would be affected once a publisher is set.

Impact

Tokens own by a publisher can be drained

Tools Used

Manual Review

Recommendations

Explictly check that the caller is the publisher within LibTractor._user()

Updates

Lead Judging Commences

inallhonesty Lead Judge over 1 year ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement

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