HIGH_ISSUE_ETH_POCgames.md

POCgames audit report.

1. Summary

This document is a security audit report performed by danbogd, where POCgames has been reviewed.

2. In scope

Сommit hash .

• FiftyFlip.sol.

3. Findings

In total, 3 issues were reported including:

• 1 high severity issues
• 1 medium severity issues
• 1 low severity issue.

No critical security issues were found.

3.1. Result Pre-Calculation

Severity: High

Description

wager function parameters ticketID and ticketLastBlock form a message that is signed externally using web3.eth.sign the signature is made of 3 variables v, r, s that are used as input parameters also to recover the secretSigner address and confirm that the ticketID was provided by the secretSigner address private key owner.

However, secretSigner state variable is assigned the value of ecrecover(signatureHash, v, r, s) output, then a requirement is set with:

require (secretSigner == ecrecover(signatureHash, v, r, s), "web3 vrs signature is not valid.");

The condition will always be true since secretSigner was assigned with the value of ecrecover(signatureHash, v, r, s), any user can call wager and put a bet.

If an attacker calculate ticketID using uint(keccak256(abi.encodePacked(ticketReveal))) with a value of ticketReveal of his choice, the attacker can call wager place a bet using the calculated ticketID. (using the setup ticketReveal will allow him to call play function and retrieve his ticketID)

play function result can be pre-calculated before calling it using the setup ticketReveal value, if the result allow the attacker to win, the attacker will call play otherwise he will wait 250 blocks and call refund.

The bot set up by the project team will not be able to call play to run the bet of the attacker since the ticketReveal will be unknown to it.

Code snippet

https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L136 https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L137 https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L160 https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L156-L201

3.2. Donation Withdrawal

Severity: medium

Description

If a donator withdraw an amount higher than address(this).balance - lockedInBets - jackpotSize - devFeeSize using withdrawDonation, checkContractHealth modifier will not allow multiple functions to execute, the contract will freeze most actions until a new donation is done or ether is sent to contract through the fallback function.

donator should not be allowed to withdraw an amount higher than address(this).balance - lockedInBets - jackpotSize - devFeeSize.

The consequences can vary widely for both the project team and users.

Code snippet

https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L211-L219

3.3. No checking for zero address.

Severity: low

Description

Functions member of FiftyFlip contract do not require the to address to be non null before transfer. Accidental token loss to address 0x0 can be applicable.

Code snippet

https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L74

https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L107

https://gist.github.com/yuriy77k/909d9541f30628d3a0e6c39af36a4cdf#file-fiftyflip-sol-L114

4. Conclusion

The contract is not safe, a direct exploit has been highlighted.