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Merge pull request #3793 from ethereum/rationalNumberLimit

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Rational number limit
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chriseth 2018-04-16 13:10:50 +02:00 committed by GitHub
commit 533d08517f
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11 changed files with 297 additions and 20 deletions
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1
Changelog.md
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@ -43,6 +43,7 @@ Bugfixes:
* Type System: Improve error message when attempting to shift by a fractional amount.
* Type System: Make external library functions accessible.
* Type System: Prevent encoding of weird types.
* Type System: Restrict rational numbers to 4096 bits.
* Static Analyzer: Fix non-deterministic order of unused variable warnings.
* Static Analyzer: Invalid arithmetic with constant expressions causes errors.

180
libsolidity/ast/Types.cpp
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@ -44,6 +44,85 @@ using namespace std;
using namespace dev;
using namespace dev::solidity;
namespace
{
unsigned int mostSignificantBit(bigint const& _number)
{
#if BOOST_VERSION < 105500
solAssert(_number > 0, "");
bigint number = _number;
unsigned int result = 0;
while (number != 0)
{
number >>= 1;
++result;
}
return --result;
#else
return boost::multiprecision::msb(_number);
#endif
}
/// Check whether (_base ** _exp) fits into 4096 bits.
bool fitsPrecisionExp(bigint const& _base, bigint const& _exp)
{
if (_base == 0)
return true;
solAssert(_base > 0, "");
size_t const bitsMax = 4096;
unsigned mostSignificantBaseBit = mostSignificantBit(_base);
if (mostSignificantBaseBit == 0) // _base == 1
return true;
if (mostSignificantBaseBit > bitsMax) // _base >= 2 ^ 4096
return false;
bigint bitsNeeded = _exp * (mostSignificantBaseBit + 1);
return bitsNeeded <= bitsMax;
}
/// Checks whether _mantissa * (X ** _exp) fits into 4096 bits,
/// where X is given indirectly via _log2OfBase = log2(X).
bool fitsPrecisionBaseX(
bigint const& _mantissa,
double _log2OfBase,
uint32_t _exp
)
{
if (_mantissa == 0)
return true;
solAssert(_mantissa > 0, "");
size_t const bitsMax = 4096;
unsigned mostSignificantMantissaBit = mostSignificantBit(_mantissa);
if (mostSignificantMantissaBit > bitsMax) // _mantissa >= 2 ^ 4096
return false;
bigint bitsNeeded = mostSignificantMantissaBit + bigint(floor(double(_exp) * _log2OfBase)) + 1;
return bitsNeeded <= bitsMax;
}
/// Checks whether _mantissa * (10 ** _expBase10) fits into 4096 bits.
bool fitsPrecisionBase10(bigint const& _mantissa, uint32_t _expBase10)
{
double const log2Of10AwayFromZero = 3.3219280948873624;
return fitsPrecisionBaseX(_mantissa, log2Of10AwayFromZero, _expBase10);
}
/// Checks whether _mantissa * (2 ** _expBase10) fits into 4096 bits.
bool fitsPrecisionBase2(bigint const& _mantissa, uint32_t _expBase2)
{
return fitsPrecisionBaseX(_mantissa, 1.0, _expBase2);
}
}
void StorageOffsets::computeOffsets(TypePointers const& _types)
{
bigint slotOffset = 0;
@ -689,31 +768,39 @@ tuple<bool, rational> RationalNumberType::isValidLiteral(Literal const& _literal
}
else if (expPoint != _literal.value().end())
{
// parse the exponent
// Parse base and exponent. Checks numeric limit.
bigint exp = bigint(string(expPoint + 1, _literal.value().end()));
if (exp > numeric_limits<int32_t>::max() || exp < numeric_limits<int32_t>::min())
return make_tuple(false, rational(0));
// parse the base
uint32_t expAbs = bigint(abs(exp)).convert_to<uint32_t>();
tuple<bool, rational> base = parseRational(string(_literal.value().begin(), expPoint));
if (!get<0>(base))
return make_tuple(false, rational(0));
value = get<1>(base);
if (exp < 0)
{
exp *= -1;
if (!fitsPrecisionBase10(abs(value.denominator()), expAbs))
return make_tuple(false, rational(0));
value /= boost::multiprecision::pow(
bigint(10),
exp.convert_to<int32_t>()
expAbs
);
}
else
else if (exp > 0)
{
if (!fitsPrecisionBase10(abs(value.numerator()), expAbs))
return make_tuple(false, rational(0));
value *= boost::multiprecision::pow(
bigint(10),
exp.convert_to<int32_t>()
expAbs
);
}
}
else
{
@ -912,16 +999,49 @@ TypePointer RationalNumberType::binaryOperatorResult(Token::Value _operator, Typ
using boost::multiprecision::pow;
if (other.isFractional())
return TypePointer();
else if (abs(other.m_value) > numeric_limits<uint32_t>::max())
return TypePointer(); // This will need too much memory to represent.
uint32_t exponent = abs(other.m_value).numerator().convert_to<uint32_t>();
bigint numerator = pow(m_value.numerator(), exponent);
bigint denominator = pow(m_value.denominator(), exponent);
if (other.m_value >= 0)
value = rational(numerator, denominator);
solAssert(other.m_value.denominator() == 1, "");
bigint const& exp = other.m_value.numerator();
// x ** 0 = 1
// for 0, 1 and -1 the size of the exponent doesn't have to be restricted
if (exp == 0)
value = 1;
else if (m_value.numerator() == 0 || m_value == 1)
value = m_value;
else if (m_value == -1)
{
bigint isOdd = abs(exp) & bigint(1);
value = 1 - 2 * isOdd.convert_to<int>();
}
else
// invert
value = rational(denominator, numerator);
{
if (abs(exp) > numeric_limits<uint32_t>::max())
return TypePointer(); // This will need too much memory to represent.
uint32_t absExp = bigint(abs(exp)).convert_to<uint32_t>();
// Limit size to 4096 bits
if (!fitsPrecisionExp(abs(m_value.numerator()), absExp) || !fitsPrecisionExp(abs(m_value.denominator()), absExp))
return TypePointer();
static auto const optimizedPow = [](bigint const& _base, uint32_t _exponent) -> bigint {
if (_base == 1)
return 1;
else if (_base == -1)
return 1 - 2 * int(_exponent & 1);
else
return pow(_base, _exponent);
};
bigint numerator = optimizedPow(m_value.numerator(), absExp);
bigint denominator = optimizedPow(m_value.denominator(), absExp);
if (exp >= 0)
value = rational(numerator, denominator);
else
// invert
value = rational(denominator, numerator);
}
break;
}
case Token::SHL:
@ -933,28 +1053,48 @@ TypePointer RationalNumberType::binaryOperatorResult(Token::Value _operator, Typ
return TypePointer();
else if (other.m_value > numeric_limits<uint32_t>::max())
return TypePointer();
uint32_t exponent = other.m_value.numerator().convert_to<uint32_t>();
value = m_value.numerator() * pow(bigint(2), exponent);
if (m_value.numerator() == 0)
value = 0;
else
{
uint32_t exponent = other.m_value.numerator().convert_to<uint32_t>();
if (!fitsPrecisionBase2(abs(m_value.numerator()), exponent))
return TypePointer();
value = m_value.numerator() * pow(bigint(2), exponent);
}
break;
}
// NOTE: we're using >> (SAR) to denote right shifting. The type of the LValue
// determines the resulting type and the type of shift (SAR or SHR).
case Token::SAR:
{
using boost::multiprecision::pow;
namespace mp = boost::multiprecision;
if (fractional)
return TypePointer();
else if (other.m_value < 0)
return TypePointer();
else if (other.m_value > numeric_limits<uint32_t>::max())
return TypePointer();
uint32_t exponent = other.m_value.numerator().convert_to<uint32_t>();
value = rational(m_value.numerator() / pow(bigint(2), exponent), 1);
if (m_value.numerator() == 0)
value = 0;
else
{
uint32_t exponent = other.m_value.numerator().convert_to<uint32_t>();
if (exponent > mostSignificantBit(mp::abs(m_value.numerator())))
value = 0;
else
value = rational(m_value.numerator() / mp::pow(bigint(2), exponent), 1);
}
break;
}
default:
return TypePointer();
}
// verify that numerator and denominator fit into 4096 bit after every operation
if (value.numerator() != 0 && max(mostSignificantBit(abs(value.numerator())), mostSignificantBit(abs(value.denominator()))) > 4096)
return TypePointer();
return make_shared<RationalNumberType>(value);
}
}

23
test/libsolidity/SolidityEndToEndTest.cpp
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@ -102,6 +102,29 @@ BOOST_AUTO_TEST_CASE(exp_operator_const_signed)
ABI_CHECK(callContractFunction("f()", bytes()), toBigEndian(u256(-8)));
}
BOOST_AUTO_TEST_CASE(exp_zero)
{
char const* sourceCode = R"(
contract test {
function f(uint a) returns(uint d) { return a ** 0; }
}
)";
compileAndRun(sourceCode);
testContractAgainstCppOnRange("f(uint256)", [](u256 const&) -> u256 { return u256(1); }, 0, 16);
}
BOOST_AUTO_TEST_CASE(exp_zero_literal)
{
char const* sourceCode = R"(
contract test {
function f() returns(uint d) { return 0 ** 0; }
}
)";
compileAndRun(sourceCode);
ABI_CHECK(callContractFunction("f()", bytes()), toBigEndian(u256(1)));
}
BOOST_AUTO_TEST_CASE(conditional_expression_true_literal)
{
char const* sourceCode = R"(

5
test/libsolidity/syntaxTests/types/rational_number_array_index_limit.sol Normal file
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@ -0,0 +1,5 @@
contract c {
uint[2**253] data;
}
// ----
// Warning: (17-34): Variable covers a large part of storage and thus makes collisions likely. Either use mappings or dynamic arrays and allow their size to be increased only in small quantities per transaction.

13
test/libsolidity/syntaxTests/types/rational_number_bitshift_limit.sol Normal file
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@ -0,0 +1,13 @@
contract c {
function f() public pure {
int a;
a = 1 << 4095; // shift is fine, but result too large
a = 1 << 4096; // too large
a = (1E1233) << 2; // too large
}
}
// ----
// TypeError: (71-80): Type int_const 5221...(1225 digits omitted)...5168 is not implicitly convertible to expected type int256.
// TypeError: (133-142): Operator << not compatible with types int_const 1 and int_const 4096
// TypeError: (169-182): Operator << not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 2
// TypeError: (169-182): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.

9
test/libsolidity/syntaxTests/types/rational_number_div_limit.sol Normal file
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@ -0,0 +1,9 @@
contract c {
function f() public pure {
int a;
a = 1/(2<<4094)/(2<<4094);
}
}
// ----
// TypeError: (71-92): Operator / not compatible with types rational_const 1 / 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168
// TypeError: (71-92): Type rational_const 1 / 5221...(1225 digits omitted)...5168 is not implicitly convertible to expected type int256. Try converting to type ufixed8x80 or use an explicit conversion.

50
test/libsolidity/syntaxTests/types/rational_number_exp_limit.sol Normal file
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@ -0,0 +1,50 @@
contract c {
function f() public pure {
int a;
a = 4 ** 4 ** 2 ** 4 ** 4 ** 4 ** 4;
a = -4 ** 4 ** 2 ** 4 ** 4 ** 4 ** 4 ** 4;
a = 4 ** (-(2 ** 4 ** 4 ** 4 ** 4 ** 4));
a = 0 ** 1E1233; // fine
a = 1 ** 1E1233; // fine
a = -1 ** 1E1233; // fine
a = 2 ** 1E1233;
a = -2 ** 1E1233;
a = 2 ** -1E1233;
a = -2 ** -1E1233;
a = 1E1233 ** 2;
a = -1E1233 ** 2;
a = 1E1233 ** -2;
a = -1E1233 ** -2;
a = 1E1233 ** 1E1233;
a = 1E1233 ** -1E1233;
a = -1E1233 ** 1E1233;
a = -1E1233 ** -1E1233;
}
}
// ----
// TypeError: (71-102): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
// TypeError: (71-102): Type int_const 1797...(301 digits omitted)...7216 is not implicitly convertible to expected type int256.
// TypeError: (116-148): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
// TypeError: (116-153): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
// TypeError: (116-153): Type int_const 1797...(301 digits omitted)...7216 is not implicitly convertible to expected type int256.
// TypeError: (167-203): Operator ** not compatible with types int_const 4 and int_const -179...(302 digits omitted)...7216
// TypeError: (317-328): Operator ** not compatible with types int_const 2 and int_const 1000...(1226 digits omitted)...0000
// TypeError: (342-354): Operator ** not compatible with types int_const -2 and int_const 1000...(1226 digits omitted)...0000
// TypeError: (368-380): Operator ** not compatible with types int_const 2 and int_const -100...(1227 digits omitted)...0000
// TypeError: (394-407): Operator ** not compatible with types int_const -2 and int_const -100...(1227 digits omitted)...0000
// TypeError: (421-432): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 2
// TypeError: (421-432): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (446-458): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const 2
// TypeError: (446-458): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (472-484): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const -2
// TypeError: (472-484): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (498-511): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const -2
// TypeError: (498-511): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (525-541): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 1000...(1226 digits omitted)...0000
// TypeError: (525-541): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (555-572): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const -100...(1227 digits omitted)...0000
// TypeError: (555-572): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (586-603): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const 1000...(1226 digits omitted)...0000
// TypeError: (586-603): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.
// TypeError: (617-635): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const -100...(1227 digits omitted)...0000
// TypeError: (617-635): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.

9
test/libsolidity/syntaxTests/types/rational_number_literal_limit_1.sol Normal file
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@ -0,0 +1,9 @@
contract c {
function bignum() public {
uint256 a;
a = 1e1233 / 1e1233; // 1e1233 is still fine
a = 1e1234; // 1e1234 is too big
}
}
// ----
// TypeError: (128-134): Invalid literal value.

9
test/libsolidity/syntaxTests/types/rational_number_literal_limit_2.sol Normal file
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@ -0,0 +1,9 @@
contract c {
function bignum() public {
uint a;
a = 134562324532464234452335168163516E1200 / 134562324532464234452335168163516E1200; // still fine
a = 1345623245324642344523351681635168E1200; // too large
}
}
// ----
// TypeError: (179-218): Invalid literal value.

9
test/libsolidity/syntaxTests/types/rational_number_literal_limit_3.sol Normal file
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@ -0,0 +1,9 @@
contract c {
function bignum() public {
uint a;
a = 134562324532464.234452335168163517E1200 / 134562324532464.234452335168163517E1200; // still fine
a = 134562324532464.2344523351681635177E1200; // too large
}
}
// ----
// TypeError: (181-221): Invalid literal value.

9
test/libsolidity/syntaxTests/types/rational_number_mul_limit.sol Normal file
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@ -0,0 +1,9 @@
contract c {
function f() public pure {
int a;
a = (1<<4095)*(1<<4095);
}
}
// ----
// TypeError: (71-90): Operator * not compatible with types int_const 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168
// TypeError: (71-90): Type int_const 5221...(1225 digits omitted)...5168 is not implicitly convertible to expected type int256.