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Vulnerability allowing double spend #16

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poma opened this issue Jul 26, 2019 · 2 comments
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Vulnerability allowing double spend #16

poma opened this issue Jul 26, 2019 · 2 comments

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@poma
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poma commented Jul 26, 2019 •
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Looks like in Semaphore.sol#L83 we don't check that nullifier length is less than field modulus. So nullifier_hash + 21888242871839275222246405745257275088548364400416034343698204186575808495617 will also pass snark proof verification if it fits into uint256, allowing double spend.

Example of 2 transactions:

https://kovan.etherscan.io/tx/0x5e8bf35ad76a086b98698f9d20bd7b6397ccc90aa6f85c1c5debc0262be5458a
https://kovan.etherscan.io/tx/0x9a47cc8daec9d0a5e9a860ada77730190124f9864a5917dcb8f41773d94cfc1a
@HarryR HarryR mentioned this issue Jul 26, 2019
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@Schaeff Schaeff mentioned this issue Jul 26, 2019
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@kobigurk
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kobigurk commented Jul 26, 2019 •
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This is confirmed. Thanks a lot for this report. We'll reply here when it's fixed.

@HarryR HarryR mentioned this issue Jul 26, 2019
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@kendricktan kendricktan mentioned this issue Jul 26, 2019
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This was referenced Jul 26, 2019
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@kobigurk
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Fix merged!

@BlockHeader BlockHeader mentioned this issue Jul 29, 2019
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@AntoineRondelet AntoineRondelet mentioned this issue Aug 5, 2019
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@weijiekoh weijiekoh mentioned this issue Mar 21, 2020
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@skarred14 skarred14 mentioned this issue Mar 25, 2020
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@0xsaya 0xsaya mentioned this issue May 4, 2023
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@poma @kobigurk