Ondo Finance - seerether's results

Lines of code

https://github.com/code-423n4/2023-09-ondo/blob/47d34d6d4a5303af5f46e907ac2292e6a7745f6c/contracts/bridge/SourceBridge.sol#L30

Vulnerability details

Impact

The first few transactions becomes vulnerable to replay attacks, where an attacker can mint additional tokens. This can lead to loss of funds or token inflation.

Proof of Concept

The nonce is incremented on every call to burnAndCallAxelar(). It is used to prevent replay attacks - if someone sees a payload go through, they shouldn't be able to just re-send the same payload and have it go through again.

Starting the nonce at 0 means the first transaction will use a nonce of 0. If someone sees this payload, they could re-send it since the contract has no way of knowing this nonce was already used.

A proof of concept attack:

Alice calls burnAndCallAxelar() with amount 100 and nonce 0 Eve sees this transaction go through Eve calls burnAndCallAxelar() with amount 100 and nonce 0 The contract sees nonce 0 has not been used before, allows the transaction This effectively mints an extra 100 tokens for Eve by replaying Alice's transaction.

Tools Used

Recommended Mitigation Steps

The nonce should be initialized to a random number

Assessed type

Other