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Weak PRNG #2

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code423n4 opened this issue May 7, 2021 · 1 comment
Closed

Weak PRNG #2

code423n4 opened this issue May 7, 2021 · 1 comment
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2 (Med Risk) Acknowledged bug Something isn't working duplicate This issue or pull request already exists

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@code423n4
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maplesyrup

Vulnerability details

Impact

Using blockhash/blocknumber and randNone are subject to attack, particularly by malicious miners:

https://medium.com/coinmonks/attack-on-pseudo-random-number-generator-prng-used-in-1000-guess-an-ethereum-lottery-game-7b76655f953d

This could be used to the behavior of getRandomTokenIdFromFund to cause a preferential TokenId to be returned. It allows for gaming of the system by miners or a savvy attacker.

Proof of Concept

Code is at - https://github.com/code-423n4/2021-05-nftx/blob/f6d793c136d110774de259d9f3b25d003c4f8098/nftx-protocol-v2/contracts/solidity/NFTXVaultUpgradeable.sol#L418

Tools Used

Slither

Recommended Mitigation Steps

Use of an on-chain oracle for true randomness:

ChainLink- https://blog.chain.link/verifiable-random-functions-vrf-random-number-generation-rng-feature/
RanDAO - https://github.com/randao/randao
Provable - https://provable.xyz/
@code423n4 code423n4 added bug Something isn't working 3 (High Risk) labels May 7, 2021
code423n4 added a commit that referenced this issue May 7, 2021
@code423n4
maplesyrup issue #2
f51eba4
@code423n4 code423n4 mentioned this issue May 8, 2021
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@0xKiwi 0xKiwi closed this as completed May 20, 2021
@cemozerr
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Duplicate of #78

@cemozerr cemozerr marked this as a duplicate of #78 May 25, 2021
@cemozerr cemozerr added the duplicate This issue or pull request already exists label May 25, 2021
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@0xKiwi @cemozerr @code423n4