Permanent DoS of external token deployments

[c4-bot-3]

Lines of code

https://github.com/code-423n4/2024-01-curves/blob/516aedb7b9a8d341d0d2666c23780d2bd8a9a600/contracts/Curves.sol#L338-L350

Vulnerability details

Vulnerability Details

Curves protocol introduces external token feature, allowing ERC20 compatibility for shares, which FriendTech lacks.

External ERC20 is deployed once per subject from _deployERC20, either in the same transaction when the first share is created (buyCurvesTokenWithName), or later, when someone actually needs ERC20 (withdraw or mint).

The _deployERC20 function contains a conditional revert, that can be exploited to prevent all users from using ERC20's completely.

DoS of withdraw and mint

withdraw and mint call _deployERC20 with default name and symbol.

As long as _deployERC20 is called with default name and symbol, it will deploy tokens with symbols "CURVES1", "CURVES2", etc.

When _curvesTokenCounter == X-1, if someone calls buyCurvesTokenWithName(symbol = "CURVESX"), _curvesTokenCounter will not be incremented, but symbolToSubject["CURVESX"] will be set to true.

After that, every time someone mints or withdraws a token that does not have an externalToken, the check

if (symbolToSubject[symbol] != address(0)) revert InvalidERC20Metadata();

will revert. Therefore, all existing and future collections that were not created via buyCurvesTokenWithName will never be able to have external ERC20 representation.

Attack steps

1. Adversary retrieves _curvesTokenCounter value from the Curves contract (e.g. via web3.js)
2. Adversary calls buyCurvesTokenWithName(symbol = "CURVESX"), where X = _curvesTokenCounter + 1

DoS of buyCurvesTokenWithName

To DoS future subjects that would use buyCurvesTokenWithName, a more demanding solution will be needed:

Each time someone is submitting buyCurvesTokenWithName transaction, the attacker will need to frontrun it with the same symbol, and repeat it for every new attempt. However, the fees on Form network are extremely cheap, so it may be feasible for someone to set up such griefing bot.

Attack steps

1. Alice submits buyCurvesTokenWithName(symbol = "ALICE")
2. Malicious Bob frontruns her with buyCurvesTokenWithName(symbol = "ALICE")
3. Alice's transaction reverts. Whenever she tries a different symbol, Bob will frontrun her with this symbol.

Proof of Concept

Foundry PoC

Adding Foundry to Hardhat

Impact

External ERC20 can not be deployed for any subject.

Recommended Mitigation Steps

Either remove buyCurvesTokenWithName, or allow multiple tokens to have the same symbol by removing symbolToSubject mapping and the conditional revert().

Assessed type

DoS

[c4-pre-sort]

raymondfam marked the issue as sufficient quality report

[c4-pre-sort]

raymondfam marked the issue as duplicate of #21

[c4-judge]

alcueca changed the severity to 2 (Med Risk)

[c4-judge]

alcueca marked the issue as satisfactory