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Tokens with fee on transfer are not supported #662

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code423n4 opened this issue Jan 30, 2023 · 8 comments
Closed

Tokens with fee on transfer are not supported #662

code423n4 opened this issue Jan 30, 2023 · 8 comments
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bug Something isn't working downgraded by judge Judge downgraded the risk level of this issue duplicate-454 QA (Quality Assurance) Assets are not at risk. State handling, function incorrect as to spec, issues with clarity, syntax satisfactory satisfies C4 submission criteria; eligible for awards sponsor acknowledged Technically the issue is correct, but we're not going to resolve it for XYZ reasons

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@code423n4
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Lines of code

https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L67
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L86
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L103

Vulnerability details

There are several ERC20 tokens that charge a transfer fee eg. STA, whereas some do not currently charge a fee but may do so in the future e.g. USDC.

The protocol does not appear to support rebasing/deflationary/inflationary tokens whose balance changes during transfers or over time. The necessary checks include at least verifying the amount of tokens transferred to contracts before and after the actual transfer to infer any fees/interest.

Proof of Concept

https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L67
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L86
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L103

Recommended Mitigation Steps

  • Ensure that to check previous balance/after balance equals to amount for any rebasing/inflation/deflation

  • Add support in contracts for such tokens before accepting user-supplied tokens

  • Consider supporting deflationary / rebasing / etc tokens by extra checking the balances before/after or strictly inform your users not to use such tokens if they don’t want to lose them.
@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 Jan 30, 2023
code423n4 added a commit that referenced this issue Jan 30, 2023
@code423n4
Diana issue #662
9606695
@c4-judge c4-judge added downgraded by judge Judge downgraded the risk level of this issue QA (Quality Assurance) Assets are not at risk. State handling, function incorrect as to spec, issues with clarity, syntax and removed 2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value labels Feb 6, 2023
@c4-judge
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c4-judge commented Feb 6, 2023

kirk-baird changed the severity to QA (Quality Assurance)

@waynehoover
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We do not plan on supporting rebasing tokens.

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waynehoover marked the issue as sponsor acknowledged

@c4-sponsor c4-sponsor added the sponsor acknowledged Technically the issue is correct, but we're not going to resolve it for XYZ reasons label Feb 7, 2023
@c4-judge c4-judge added 2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value and removed downgraded by judge Judge downgraded the risk level of this issue QA (Quality Assurance) Assets are not at risk. State handling, function incorrect as to spec, issues with clarity, syntax labels Feb 14, 2023
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This previously downgraded issue has been upgraded by kirk-baird

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@c4-judge
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This previously downgraded issue has been upgraded by kirk-baird

@c4-judge
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kirk-baird marked the issue as duplicate of #630

@c4-judge c4-judge added duplicate-630 satisfactory satisfies C4 submission criteria; eligible for awards labels Feb 14, 2023
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kirk-baird marked the issue as satisfactory

@c4-judge c4-judge added downgraded by judge Judge downgraded the risk level of this issue QA (Quality Assurance) Assets are not at risk. State handling, function incorrect as to spec, issues with clarity, syntax and removed 2 (Med Risk) Assets not at direct risk, but function/availability of the protocol could be impacted or leak value labels Feb 23, 2023
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kirk-baird changed the severity to QA (Quality Assurance)

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bug Something isn't working downgraded by judge Judge downgraded the risk level of this issue duplicate-454 QA (Quality Assurance) Assets are not at risk. State handling, function incorrect as to spec, issues with clarity, syntax satisfactory satisfies C4 submission criteria; eligible for awards sponsor acknowledged Technically the issue is correct, but we're not going to resolve it for XYZ reasons
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