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Bonding doesn't work with fee-on transfer tokens #251

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code423n4 opened this issue Dec 1, 2021 · 1 comment
Open

Bonding doesn't work with fee-on transfer tokens #251

code423n4 opened this issue Dec 1, 2021 · 1 comment
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2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value bug Something isn't working sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity")

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@code423n4
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cmichel

Vulnerability details

Certain ERC20 tokens make modifications to their ERC20's transfer or balanceOf functions.
One type of these tokens is deflationary tokens that charge a certain fee for every transfer() or transferFrom().

Impact

The Bonding._bond() function will revert in the _balanceCheck when transferring a fee-on-transfer token as it assumes the entire amount was received.

Recommended Mitigation Steps

To support fee-on-transfer tokens, measure the asset change right before and after the asset-transferring calls and use the difference as the actual bonded amount.
@code423n4 code423n4 added 2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value bug Something isn't working labels Dec 1, 2021
code423n4 added a commit that referenced this issue Dec 1, 2021
@code423n4
cmichel issue #251
fbaa52e
@0xScotch 0xScotch added the sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity") label Dec 8, 2021
@GalloDaSballo
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Agree with the finding, the check will revert on a token that takes fees as the system assumes that amount is the amount that will be received

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2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value bug Something isn't working sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity")
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@GalloDaSballo @0xScotch @code423n4