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fix: [asset-swapper] Catch Uint256BinOp which can occur (#2724)

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* fix: [asset-swapper] Catch Uint256BinOp which can occur

* Perform a local bounds check
This commit is contained in:
Jacob Evans
2020-10-07 17:36:44 +10:00
committed by GitHub
parent cd9e408ea3
commit 36546480b1
1 changed files with 24 additions and 3 deletions
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27
packages/asset-swapper/contracts/src/ApproximateBuys.sol
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@@ -78,16 +78,22 @@ contract ApproximateBuys {
for (uint256 i = 0; i < makerTokenAmounts.length; i++) {
for (uint256 iter = 0; iter < APPROXIMATE_BUY_MAX_ITERATIONS; iter++) {
// adjustedSellAmount = previousSellAmount * (target/actual) * JUMP_MULTIPLIER
sellAmount = LibMath.getPartialAmountCeil(
sellAmount = _safeGetPartialAmountCeil(
makerTokenAmounts[i],
buyAmount,
sellAmount
);
sellAmount = LibMath.getPartialAmountCeil(
if (sellAmount == 0) {
break;
}
sellAmount = _safeGetPartialAmountCeil(
(ONE_HUNDED_PERCENT_BPS + APPROXIMATE_BUY_TARGET_EPSILON_BPS),
ONE_HUNDED_PERCENT_BPS,
sellAmount
);
if (sellAmount == 0) {
break;
}
uint256 _buyAmount = opts.getSellQuoteCallback(
opts.takerTokenData,
opts.makerTokenData,
@@ -112,11 +118,26 @@ contract ApproximateBuys {
// We do our best to close in on the requested amount, but we can either over buy or under buy and exit
// if we hit a max iteration limit
// We scale the sell amount to get the approximate target
takerTokenAmounts[i] = LibMath.getPartialAmountCeil(
takerTokenAmounts[i] = _safeGetPartialAmountCeil(
makerTokenAmounts[i],
buyAmount,
sellAmount
);
}
}
function _safeGetPartialAmountCeil(
uint256 numerator,
uint256 denominator,
uint256 target
)
internal
view
returns (uint256 partialAmount)
{
if (numerator == 0 || target == 0 || denominator == 0) return 0;
uint256 c = numerator * target;
if (c / numerator != target) return 0;
return (c + (denominator - 1)) / denominator;
}
}