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Merge pull request #145 from gavofyork/evm

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Handling all possible overflows
This commit is contained in:
Arkadiy Paronyan 2016-01-17 15:58:26 +01:00
commit 2c0d84e2c7
1 changed files with 116 additions and 145 deletions
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261
src/evm/interpreter.rs
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@ -27,6 +27,14 @@ fn color(instruction: Instruction, name: &'static str) -> String {
format!("\x1B[1;{}m{}\x1B[0m", colors[c], name) format!("\x1B[1;{}m{}\x1B[0m", colors[c], name)
} }
macro_rules! overflowing {
($x: expr) => {{
let (v, overflow) = $x;
if overflow { return Err(evm::Error::OutOfGas); }
v
}}
}
type CodePosition = usize; type CodePosition = usize;
type Gas = U256; type Gas = U256;
type ProgramCounter = usize; type ProgramCounter = usize;
@ -136,7 +144,7 @@ trait Memory {
/// Checks whether offset and size is valid memory range /// Checks whether offset and size is valid memory range
fn is_valid_range(off: usize, size: usize) -> bool { fn is_valid_range(off: usize, size: usize) -> bool {
// When size is zero we haven't actually expanded the memory // When size is zero we haven't actually expanded the memory
let (_a, overflow) = off.overflowing_add(size); let overflow = off.overflowing_add(size).1;
size > 0 && !overflow size > 0 && !overflow
} }
@ -235,15 +243,10 @@ impl<'a> CodeReader<'a> {
} }
} }
enum RequiredMem {
Mem(U256),
OutOfMemory
}
enum InstructionCost { enum InstructionCost {
Gas(U256), Gas(U256),
GasMem(U256, RequiredMem), GasMem(U256, U256),
GasMemCopy(U256, RequiredMem, U256) GasMemCopy(U256, U256, U256)
} }
enum InstructionResult { enum InstructionResult {
@ -373,35 +376,31 @@ impl Interpreter {
InstructionCost::Gas(U256::from(schedule.sload_gas)) InstructionCost::Gas(U256::from(schedule.sload_gas))
}, },
instructions::MSTORE => { instructions::MSTORE => {
InstructionCost::GasMem(default_gas, self.mem_needed_const(stack.peek(0), 32)) InstructionCost::GasMem(default_gas, try!(self.mem_needed_const(stack.peek(0), 32)))
}, },
instructions::MLOAD => { instructions::MLOAD => {
InstructionCost::GasMem(default_gas, self.mem_needed_const(stack.peek(0), 32)) InstructionCost::GasMem(default_gas, try!(self.mem_needed_const(stack.peek(0), 32)))
}, },
instructions::MSTORE8 => { instructions::MSTORE8 => {
InstructionCost::GasMem(default_gas, self.mem_needed_const(stack.peek(0), 1)) InstructionCost::GasMem(default_gas, try!(self.mem_needed_const(stack.peek(0), 1)))
}, },
instructions::RETURN => { instructions::RETURN => {
InstructionCost::GasMem(default_gas, self.mem_needed(stack.peek(0), stack.peek(1))) InstructionCost::GasMem(default_gas, try!(self.mem_needed(stack.peek(0), stack.peek(1))))
}, },
instructions::SHA3 => { instructions::SHA3 => {
match add_u256_usize(stack.peek(1), 31) { let w = overflowing!(add_u256_usize(stack.peek(1), 31));
(_w, true) => InstructionCost::GasMem(U256::zero(), RequiredMem::OutOfMemory), let words = w >> 5;
(w, false) => { let gas = U256::from(schedule.sha3_gas) + (U256::from(schedule.sha3_word_gas) * words);
let words = w >> 5; InstructionCost::GasMem(gas, try!(self.mem_needed(stack.peek(0), stack.peek(1))))
let gas = U256::from(schedule.sha3_gas) + (U256::from(schedule.sha3_word_gas) * words);
InstructionCost::GasMem(gas, self.mem_needed(stack.peek(0), stack.peek(1)))
}
}
}, },
instructions::CALLDATACOPY => { instructions::CALLDATACOPY => {
InstructionCost::GasMemCopy(default_gas, self.mem_needed(stack.peek(0), stack.peek(2)), stack.peek(2).clone()) InstructionCost::GasMemCopy(default_gas, try!(self.mem_needed(stack.peek(0), stack.peek(2))), stack.peek(2).clone())
}, },
instructions::CODECOPY => { instructions::CODECOPY => {
InstructionCost::GasMemCopy(default_gas, self.mem_needed(stack.peek(0), stack.peek(2)), stack.peek(2).clone()) InstructionCost::GasMemCopy(default_gas, try!(self.mem_needed(stack.peek(0), stack.peek(2))), stack.peek(2).clone())
}, },
instructions::EXTCODECOPY => { instructions::EXTCODECOPY => {
InstructionCost::GasMemCopy(default_gas, self.mem_needed(stack.peek(1), stack.peek(3)), stack.peek(3).clone()) InstructionCost::GasMemCopy(default_gas, try!(self.mem_needed(stack.peek(1), stack.peek(3))), stack.peek(3).clone())
}, },
instructions::JUMPDEST => { instructions::JUMPDEST => {
InstructionCost::Gas(U256::one()) InstructionCost::Gas(U256::one())
@ -409,50 +408,41 @@ impl Interpreter {
instructions::LOG0...instructions::LOG4 => { instructions::LOG0...instructions::LOG4 => {
let no_of_topics = instructions::get_log_topics(instruction); let no_of_topics = instructions::get_log_topics(instruction);
let log_gas = schedule.log_gas + schedule.log_topic_gas * no_of_topics; let log_gas = schedule.log_gas + schedule.log_topic_gas * no_of_topics;
// TODO [todr] potential overflow of datagass
let data_gas = stack.peek(1).clone() * U256::from(schedule.log_data_gas); let data_gas = overflowing!(stack.peek(1).overflowing_mul(U256::from(schedule.log_data_gas)));
let gas = try!(self.gas_add(data_gas, U256::from(log_gas))); let gas = overflowing!(data_gas.overflowing_add(U256::from(log_gas)));
InstructionCost::GasMem(gas, self.mem_needed(stack.peek(0), stack.peek(1))) InstructionCost::GasMem(gas, try!(self.mem_needed(stack.peek(0), stack.peek(1))))
}, },
instructions::CALL | instructions::CALLCODE => { instructions::CALL | instructions::CALLCODE => {
match add_u256_usize(stack.peek(0), schedule.call_gas) { let mut gas = overflowing!(add_u256_usize(stack.peek(0), schedule.call_gas));
(_gas, true) => InstructionCost::GasMem(U256::zero(), RequiredMem::OutOfMemory), let mem = cmp::max(
(mut gas, false) => { try!(self.mem_needed(stack.peek(5), stack.peek(6))),
let mem = self.mem_max( try!(self.mem_needed(stack.peek(3), stack.peek(4)))
self.mem_needed(stack.peek(5), stack.peek(6)), );
self.mem_needed(stack.peek(3), stack.peek(4))
); let address = u256_to_address(stack.peek(1));
let address = u256_to_address(stack.peek(1));
// TODO [todr] Potential overflows if instruction == instructions::CALL && !ext.exists(&address) {
if instruction == instructions::CALL && !ext.exists(&address) { gas = overflowing!(gas.overflowing_add(U256::from(schedule.call_new_account_gas)));
gas = gas + U256::from(schedule.call_new_account_gas); };
};
if stack.peek(2).clone() > U256::zero() { if stack.peek(2).clone() > U256::zero() {
gas = gas + U256::from(schedule.call_value_transfer_gas) gas = overflowing!(gas.overflowing_add(U256::from(schedule.call_value_transfer_gas)));
}; };
InstructionCost::GasMem(gas,mem) InstructionCost::GasMem(gas,mem)
}
}
}, },
instructions::DELEGATECALL => { instructions::DELEGATECALL => {
match add_u256_usize(stack.peek(0), schedule.call_gas) { let gas = overflowing!(add_u256_usize(stack.peek(0), schedule.call_gas));
(_gas, true) => InstructionCost::GasMem(U256::zero(), RequiredMem::OutOfMemory), let mem = cmp::max(
(gas, false) => { try!(self.mem_needed(stack.peek(4), stack.peek(5))),
let mem = self.mem_max( try!(self.mem_needed(stack.peek(2), stack.peek(3)))
self.mem_needed(stack.peek(4), stack.peek(5)), );
self.mem_needed(stack.peek(2), stack.peek(3)) InstructionCost::GasMem(gas, mem)
);
InstructionCost::GasMem(gas, mem)
}
}
}, },
instructions::CREATE => { instructions::CREATE => {
let gas = U256::from(schedule.create_gas); let gas = U256::from(schedule.create_gas);
let mem = self.mem_needed(stack.peek(1), stack.peek(2)); let mem = try!(self.mem_needed(stack.peek(1), stack.peek(2)));
InstructionCost::GasMem(gas, mem) InstructionCost::GasMem(gas, mem)
}, },
instructions::EXP => { instructions::EXP => {
@ -468,84 +458,57 @@ impl Interpreter {
InstructionCost::Gas(gas) => { InstructionCost::Gas(gas) => {
Ok((gas, 0)) Ok((gas, 0))
}, },
InstructionCost::GasMem(gas, mem_size) => match mem_size { InstructionCost::GasMem(gas, mem_size) => {
RequiredMem::Mem(mem_size) => { let (mem_gas, new_mem_size) = try!(self.mem_gas_cost(schedule, mem.size(), &mem_size));
let (mem_gas, new_mem_size) = self.mem_gas_cost(schedule, mem.size(), &mem_size); let gas = overflowing!(gas.overflowing_add(mem_gas));
let gas = try!(self.gas_add(gas, mem_gas)); Ok((gas, new_mem_size))
Ok((gas, new_mem_size))
},
RequiredMem::OutOfMemory => Err(evm::Error::OutOfGas)
}, },
InstructionCost::GasMemCopy(gas, mem_size, copy) => match mem_size { InstructionCost::GasMemCopy(gas, mem_size, copy) => {
RequiredMem::Mem(mem_size) => { let (mem_gas, new_mem_size) = try!(self.mem_gas_cost(schedule, mem.size(), &mem_size));
let (mem_gas, new_mem_size) = self.mem_gas_cost(schedule, mem.size(), &mem_size); let copy = overflowing!(add_u256_usize(&copy, 31));
match add_u256_usize(&copy, 31) { let copy_gas = U256::from(schedule.copy_gas) * (copy / U256::from(32));
(_c, true) => Err(evm::Error::OutOfGas), let gas = overflowing!(gas.overflowing_add(copy_gas));
(copy, false) => { let gas = overflowing!(gas.overflowing_add(mem_gas));
let copy_gas = U256::from(schedule.copy_gas) * (copy / U256::from(32)); Ok((gas, new_mem_size))
let gas = try!(self.gas_add(try!(self.gas_add(gas, copy_gas)), mem_gas));
Ok((gas, new_mem_size))
}
}
},
RequiredMem::OutOfMemory => Err(evm::Error::OutOfGas)
} }
} }
} }
fn gas_add(&self, a: U256, b: U256) -> Result<U256, evm::Error> { fn mem_gas_cost(&self, schedule: &evm::Schedule, current_mem_size: usize, mem_size: &U256) -> Result<(U256, usize), evm::Error> {
match a.overflowing_add(b) {
(_val, true) => Err(evm::Error::OutOfGas),
(val, false) => Ok(val)
}
}
fn mem_gas_cost(&self, schedule: &evm::Schedule, current_mem_size: usize, mem_size: &U256) -> (U256, usize) {
let gas_for_mem = |mem_size: U256| { let gas_for_mem = |mem_size: U256| {
let s = mem_size >> 5; let s = mem_size >> 5;
s * U256::from(schedule.memory_gas) + s * s / U256::from(schedule.quad_coeff_div) // s * memory_gas + s * s / quad_coeff_div
let a = overflowing!(s.overflowing_mul(U256::from(schedule.memory_gas)));
// We need to go to U512 to calculate s*s/quad_coeff_div
let b = U512::from(s) * U512::from(s) / U512::from(schedule.quad_coeff_div);
if b > U512::from(!U256::zero()) {
Err(evm::Error::OutOfGas)
} else {
Ok(overflowing!(a.overflowing_add(U256::from(b))))
}
}; };
let current_mem_size = U256::from(current_mem_size); let current_mem_size = U256::from(current_mem_size);
let req_mem_size_rounded = ((mem_size.clone() + U256::from(31)) >> 5) << 5; let req_mem_size_rounded = (overflowing!(mem_size.overflowing_add(U256::from(31))) >> 5) << 5;
let new_mem_gas = gas_for_mem(U256::from(req_mem_size_rounded)); let new_mem_gas = try!(gas_for_mem(U256::from(req_mem_size_rounded)));
let current_mem_gas = gas_for_mem(current_mem_size); let current_mem_gas = try!(gas_for_mem(current_mem_size));
(if req_mem_size_rounded > current_mem_size { Ok((if req_mem_size_rounded > current_mem_size {
new_mem_gas - current_mem_gas new_mem_gas - current_mem_gas
} else { } else {
U256::zero() U256::zero()
}, req_mem_size_rounded.low_u64() as usize) }, req_mem_size_rounded.low_u64() as usize))
} }
fn mem_max(&self, m_a: RequiredMem, m_b: RequiredMem) -> RequiredMem { fn mem_needed_const(&self, mem: &U256, add: usize) -> Result<U256, evm::Error> {
match (m_a, m_b) { Ok(overflowing!(mem.overflowing_add(U256::from(add))))
(RequiredMem::Mem(a), RequiredMem::Mem(b)) => {
RequiredMem::Mem(cmp::max(a, b))
},
(RequiredMem::OutOfMemory, _) | (_, RequiredMem::OutOfMemory) => {
RequiredMem::OutOfMemory
}
}
} }
fn mem_needed_const(&self, mem: &U256, add: usize) -> RequiredMem { fn mem_needed(&self, offset: &U256, size: &U256) -> Result<U256, ::evm::Error> {
match mem.overflowing_add(U256::from(add)) {
(_, true) => RequiredMem::OutOfMemory,
(mem, false) => RequiredMem::Mem(mem)
}
}
fn mem_needed(&self, offset: &U256, size: &U256) -> RequiredMem {
if self.is_zero(size) { if self.is_zero(size) {
return RequiredMem::Mem(U256::zero()); return Ok(U256::zero());
} }
match offset.clone().overflowing_add(size.clone()) { Ok(overflowing!(offset.overflowing_add(size.clone())))
(_result, true) => RequiredMem::OutOfMemory,
(result, false) => {
RequiredMem::Mem(result)
}
}
} }
fn exec_instruction(&self, fn exec_instruction(&self,
@ -646,7 +609,6 @@ impl Interpreter {
return match call_result { return match call_result {
MessageCallResult::Success(gas_left) => { MessageCallResult::Success(gas_left) => {
println!("Unused: {}", gas_left);
stack.push(U256::one()); stack.push(U256::one());
Ok(InstructionResult::UnusedGas(gas_left)) Ok(InstructionResult::UnusedGas(gas_left))
}, },
@ -906,41 +868,34 @@ impl Interpreter {
instructions::ADD => { instructions::ADD => {
let a = stack.pop_back(); let a = stack.pop_back();
let b = stack.pop_back(); let b = stack.pop_back();
let (c, _overflow) = a.overflowing_add(b); stack.push(a.overflowing_add(b).0);
stack.push(c);
}, },
instructions::MUL => { instructions::MUL => {
let a = stack.pop_back(); let a = stack.pop_back();
let b = stack.pop_back(); let b = stack.pop_back();
let (c, _overflow) = a.overflowing_mul(b); stack.push(a.overflowing_mul(b).0);
stack.push(c);
}, },
instructions::SUB => { instructions::SUB => {
let a = stack.pop_back(); let a = stack.pop_back();
let b = stack.pop_back(); let b = stack.pop_back();
let (c, _overflow) = a.overflowing_sub(b); stack.push(a.overflowing_sub(b).0);
stack.push(c);
}, },
instructions::DIV => { instructions::DIV => {
let a = stack.pop_back(); let a = stack.pop_back();
let b = stack.pop_back(); let b = stack.pop_back();
stack.push(match !self.is_zero(&b) { stack.push(if !self.is_zero(&b) {
true => { a.overflowing_div(b).0
let (c, _overflow) = a.overflowing_div(b); } else {
c U256::zero()
},
false => U256::zero()
}); });
}, },
instructions::MOD => { instructions::MOD => {
let a = stack.pop_back(); let a = stack.pop_back();
let b = stack.pop_back(); let b = stack.pop_back();
stack.push(match !self.is_zero(&b) { stack.push(if !self.is_zero(&b) {
true => { a.overflowing_rem(b).0
let (c, _overflow) = a.overflowing_rem(b); } else {
c U256::zero()
},
false => U256::zero()
}); });
}, },
instructions::SDIV => { instructions::SDIV => {
@ -954,7 +909,7 @@ impl Interpreter {
} else if a == min && b == !U256::zero() { } else if a == min && b == !U256::zero() {
min min
} else { } else {
let (c, _overflow) = a.overflowing_div(b); let c = a.overflowing_div(b).0;
set_sign(c, sign_a ^ sign_b) set_sign(c, sign_a ^ sign_b)
}); });
}, },
@ -962,10 +917,10 @@ impl Interpreter {
let ua = stack.pop_back(); let ua = stack.pop_back();
let ub = stack.pop_back(); let ub = stack.pop_back();
let (a, sign_a) = get_and_reset_sign(ua); let (a, sign_a) = get_and_reset_sign(ua);
let (b, _sign_b) = get_and_reset_sign(ub); let b = get_and_reset_sign(ub).0;
stack.push(if !self.is_zero(&b) { stack.push(if !self.is_zero(&b) {
let (c, _overflow) = a.overflowing_rem(b); let c = a.overflowing_rem(b).0;
set_sign(c, sign_a) set_sign(c, sign_a)
} else { } else {
U256::zero() U256::zero()
@ -974,7 +929,7 @@ impl Interpreter {
instructions::EXP => { instructions::EXP => {
let base = stack.pop_back(); let base = stack.pop_back();
let expon = stack.pop_back(); let expon = stack.pop_back();
let (res, _overflow) = base.overflowing_pow(expon); let res = base.overflowing_pow(expon).0;
stack.push(res); stack.push(res);
}, },
instructions::NOT => { instructions::NOT => {
@ -1052,8 +1007,8 @@ impl Interpreter {
stack.push(if !self.is_zero(&c) { stack.push(if !self.is_zero(&c) {
// upcast to 512 // upcast to 512
let a5 = U512::from(a); let a5 = U512::from(a);
let (res, _overflow) = a5.overflowing_add(U512::from(b)); let res = a5.overflowing_add(U512::from(b)).0;
let (x, _overflow) = res.overflowing_rem(U512::from(c)); let x = res.overflowing_rem(U512::from(c)).0;
U256::from(x) U256::from(x)
} else { } else {
U256::zero() U256::zero()
@ -1066,8 +1021,8 @@ impl Interpreter {
stack.push(if !self.is_zero(&c) { stack.push(if !self.is_zero(&c) {
let a5 = U512::from(a); let a5 = U512::from(a);
let (res, _overflow) = a5.overflowing_mul(U512::from(b)); let res = a5.overflowing_mul(U512::from(b)).0;
let (x, _overflow) = res.overflowing_rem(U512::from(c)); let x = res.overflowing_rem(U512::from(c)).0;
U256::from(x) U256::from(x)
} else { } else {
U256::zero() U256::zero()
@ -1123,8 +1078,7 @@ fn get_and_reset_sign(value: U256) -> (U256, bool) {
fn set_sign(value: U256, sign: bool) -> U256 { fn set_sign(value: U256, sign: bool) -> U256 {
if sign { if sign {
let (val, _overflow) = (!U256::zero() ^ value).overflowing_add(U256::one()); (!U256::zero() ^ value).overflowing_add(U256::one()).0
val
} else { } else {
value value
} }
@ -1145,6 +1099,23 @@ fn address_to_u256(value: Address) -> U256 {
U256::from(H256::from(value).as_slice()) U256::from(H256::from(value).as_slice())
} }
#[test]
fn test_mem_gas_cost() {
// given
let interpreter = Interpreter;
let schedule = evm::Schedule::default();
let current_mem_size = 5;
let mem_size = !U256::zero();
// when
let result = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size);
// then
if let Ok(_) = result {
assert!(false, "Should fail with OutOfGas");
}
}
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
use common::*; use common::*;
@ -1173,7 +1144,7 @@ mod tests {
let mem_size = U256::from(5); let mem_size = U256::from(5);
// when // when
let (mem_cost, mem_size) = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size); let (mem_cost, mem_size) = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size).unwrap();
// then // then
assert_eq!(mem_cost, U256::from(3)); assert_eq!(mem_cost, U256::from(3));