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Merge pull request #13130 from ethereum/check-overflow-after-add-sub-operations

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Check overflow after add sub operations
This commit is contained in:
chriseth
2022-06-27 15:33:57 +02:00
committed by GitHub
parent 2397f09b79 4fd5c11af7
commit b70e064e8f
49 changed files with 450 additions and 434 deletions
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libsolidity/codegen/YulUtilFunctions.cpp
+44 -20
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@@ -615,25 +615,34 @@ string YulUtilFunctions::divide32CeilFunction()
string YulUtilFunctions::overflowCheckedIntAddFunction(IntegerType const& _type)
{
string functionName = "checked_add_" + _type.identifier();
// TODO: Consider to add a special case for unsigned 256-bit integers
// and use the following instead:
// sum := add(x, y) if lt(sum, x) { <panic>() }
return m_functionCollector.createFunction(functionName, [&]() {
return
Whiskers(R"(
function <functionName>(x, y) -> sum {
x := <cleanupFunction>(x)
y := <cleanupFunction>(y)
<?signed>
// overflow, if x >= 0 and y > (maxValue - x)
if and(iszero(slt(x, 0)), sgt(y, sub(<maxValue>, x))) { <panic>() }
// underflow, if x < 0 and y < (minValue - x)
if and(slt(x, 0), slt(y, sub(<minValue>, x))) { <panic>() }
<!signed>
// overflow, if x > (maxValue - y)
if gt(x, sub(<maxValue>, y)) { <panic>() }
</signed>
sum := add(x, y)
<?signed>
<?256bit>
// overflow, if x >= 0 and sum < y
// underflow, if x < 0 and sum >= y
if or(
and(iszero(slt(x, 0)), slt(sum, y)),
and(slt(x, 0), iszero(slt(sum, y)))
) { <panic>() }
<!256bit>
if or(
sgt(sum, <maxValue>),
slt(sum, <minValue>)
) { <panic>() }
</256bit>
<!signed>
<?256bit>
if gt(x, sum) { <panic>() }
<!256bit>
if gt(sum, <maxValue>) { <panic>() }
</256bit>
</signed>
}
)")
("functionName", functionName)
@@ -642,6 +651,7 @@ string YulUtilFunctions::overflowCheckedIntAddFunction(IntegerType const& _type)
("minValue", toCompactHexWithPrefix(u256(_type.minValue())))
("cleanupFunction", cleanupFunction(_type))
("panic", panicFunction(PanicCode::UnderOverflow))
("256bit", _type.numBits() == 256)
.render();
});
}
@@ -795,15 +805,28 @@ string YulUtilFunctions::overflowCheckedIntSubFunction(IntegerType const& _type)
function <functionName>(x, y) -> diff {
x := <cleanupFunction>(x)
y := <cleanupFunction>(y)
<?signed>
// underflow, if y >= 0 and x < (minValue + y)
if and(iszero(slt(y, 0)), slt(x, add(<minValue>, y))) { <panic>() }
// overflow, if y < 0 and x > (maxValue + y)
if and(slt(y, 0), sgt(x, add(<maxValue>, y))) { <panic>() }
<!signed>
if lt(x, y) { <panic>() }
</signed>
diff := sub(x, y)
<?signed>
<?256bit>
// underflow, if y >= 0 and diff > x
// overflow, if y < 0 and diff < x
if or(
and(iszero(slt(y, 0)), sgt(diff, x)),
and(slt(y, 0), slt(diff, x))
) { <panic>() }
<!256bit>
if or(
slt(diff, <minValue>),
sgt(diff, <maxValue>)
) { <panic>() }
</256bit>
<!signed>
<?256bit>
if gt(diff, x) { <panic>() }
<!256bit>
if gt(diff, <maxValue>) { <panic>() }
</256bit>
</signed>
}
)")
("functionName", functionName)
@@ -812,6 +835,7 @@ string YulUtilFunctions::overflowCheckedIntSubFunction(IntegerType const& _type)
("minValue", toCompactHexWithPrefix(u256(_type.minValue())))
("cleanupFunction", cleanupFunction(_type))
("panic", panicFunction(PanicCode::UnderOverflow))
("256bit", _type.numBits() == 256)
.render();
});
}