more dos protection (#8104)

ethcore/vm/src/schedule.rs

@@ -135,6 +135,8 @@ pub struct WasmCosts {
 	pub initial_mem: u32,
 	/// Grow memory cost, per page (64kb)
 	pub grow_mem: u32,
+	/// Memory copy cost, per byte
+	pub memcpy: u32,
 	/// Max stack height (native WebAssembly stack limiter)
 	pub max_stack_height: u32,
 	/// Cost of wasm opcode is calculated as TABLE_ENTRY_COST * `opcodes_mul` / `opcodes_div`
@@ -154,6 +156,7 @@ impl Default for WasmCosts {
 			static_address: 40,
 			initial_mem: 4096,
 			grow_mem: 8192,
+			memcpy: 1,
 			max_stack_height: 64*1024,
 			opcodes_mul: 3,
 			opcodes_div: 8,

ethcore/wasm/src/lib.rs

@@ -77,6 +77,12 @@ impl From<runtime::Error> for vm::Error {
 	}
 }
 
+enum ExecutionOutcome {
+	Suicide,
+	Return,
+	NotSpecial,
+}
+
 impl vm::Vm for WasmInterpreter {
 
 	fn exec(&mut self, params: ActionParams, ext: &mut vm::Ext) -> vm::Result<GasLeft> {
@@ -130,22 +136,24 @@ impl vm::Vm for WasmInterpreter {
 
 			let invoke_result = module_instance.invoke_export("call", &[], &mut runtime);
 
-			let mut suicide = false;
+			let mut execution_outcome = ExecutionOutcome::NotSpecial;
 			if let Err(InterpreterError::Trap(ref trap)) = invoke_result {
 				if let wasmi::TrapKind::Host(ref boxed) = *trap.kind() {
 					let ref runtime_err = boxed.downcast_ref::<runtime::Error>()
 						.expect("Host errors other than runtime::Error never produced; qed");
 
-					if let runtime::Error::Suicide = **runtime_err { suicide = true; }
+					match **runtime_err {
+						runtime::Error::Suicide => { execution_outcome = ExecutionOutcome::Suicide; },
+						runtime::Error::Return => { execution_outcome = ExecutionOutcome::Return; },
+						_ => {}
+					}
 				}
 			}
 
-			if !suicide {
-				if let Err(e) = invoke_result {
+			if let (ExecutionOutcome::NotSpecial, Err(e)) = (execution_outcome, invoke_result) {
 				trace!(target: "wasm", "Error executing contract: {:?}", e);
 				return Err(vm::Error::from(Error::from(e)));
 			}
-			}
 
 			(
 				runtime.gas_left().expect("Cannot fail since it was not updated since last charge"),

ethcore/wasm/src/runtime.rs

@@ -32,6 +32,8 @@ pub enum Error {
 	MemoryAccessViolation,
 	/// Native code resulted in suicide
 	Suicide,
+	/// Native code requested execution to finish
+	Return,
 	/// Suicide was requested but coudn't complete
 	SuicideAbort,
 	/// Invalid gas state inside interpreter
@@ -103,6 +105,7 @@ impl ::std::fmt::Display for Error {
 			Error::InvalidGasState => write!(f, "Invalid gas state"),
 			Error::BalanceQueryError => write!(f, "Balance query resulted in an error"),
 			Error::Suicide => write!(f, "Suicide result"),
+			Error::Return => write!(f, "Return result"),
 			Error::Unknown => write!(f, "Unknown runtime function invoked"),
 			Error::AllocationFailed => write!(f, "Memory allocation failed (OOM)"),
 			Error::BadUtf8 => write!(f, "String encoding is bad utf-8 sequence"),
@@ -289,7 +292,7 @@ impl<'a> Runtime<'a> {
 
 		self.result = self.memory.get(ptr, len as usize)?;
 
-		Ok(())
+		Err(Error::Return)
 	}
 
 	/// Destroy the runtime, returning currently recorded result of the execution
@@ -321,6 +324,10 @@ impl<'a> Runtime<'a> {
 	/// Write input bytes to the memory location using the passed pointer
 	fn fetch_input(&mut self, args: RuntimeArgs) -> Result<()> {
 		let ptr: u32 = args.nth_checked(0)?;
+
+		let args_len = self.args.len() as u64;
+		self.charge(|s| args_len * s.wasm().memcpy as u64)?;
+
 		self.memory.set(ptr, &self.args[..])?;
 		Ok(())
 	}

ethcore/wasm/src/tests.rs

@@ -207,7 +207,7 @@ fn dispersion() {
 		result,
 		vec![0u8, 0, 125, 11, 197, 7, 255, 8, 19, 0]
 	);
-	assert_eq!(gas_left, U256::from(93_972));
+	assert_eq!(gas_left, U256::from(94_013));
 }
 
 #[test]
@@ -235,7 +235,7 @@ fn suicide_not() {
 		result,
 		vec![0u8]
 	);
-	assert_eq!(gas_left, U256::from(94_970));
+	assert_eq!(gas_left, U256::from(94_984));
 }
 
 #[test]
@@ -267,7 +267,7 @@ fn suicide() {
 	};
 
 	assert!(ext.suicides.contains(&refund));
-	assert_eq!(gas_left, U256::from(94_933));
+	assert_eq!(gas_left, U256::from(94_925));
 }
 
 #[test]
@@ -297,7 +297,7 @@ fn create() {
 	assert!(ext.calls.contains(
 		&FakeCall {
 			call_type: FakeCallType::Create,
-			gas: U256::from(60_917),
+			gas: U256::from(60_914),
 			sender_address: None,
 			receive_address: None,
 			value: Some(1_000_000_000.into()),
@@ -305,7 +305,7 @@ fn create() {
 			code_address: None,
 		}
 	));
-	assert_eq!(gas_left, U256::from(60_903));
+	assert_eq!(gas_left, U256::from(60_900));
 }
 
 #[test]
@@ -465,7 +465,7 @@ fn realloc() {
 		}
 	};
 	assert_eq!(result, vec![0u8; 2]);
-	assert_eq!(gas_left, U256::from(94_352));
+	assert_eq!(gas_left, U256::from(94_372));
 }
 
 #[test]
@@ -541,7 +541,7 @@ fn keccak() {
 	};
 
 	assert_eq!(H256::from_slice(&result), H256::from("68371d7e884c168ae2022c82bd837d51837718a7f7dfb7aa3f753074a35e1d87"));
-	assert_eq!(gas_left, U256::from(84_223));
+	assert_eq!(gas_left, U256::from(84_240));
 }
 
 // math_* tests check the ability of wasm contract to perform big integer operations
@@ -570,7 +570,7 @@ fn math_add() {
 		U256::from_dec_str("1888888888888888888888888888887").unwrap(),
 		(&result[..]).into()
 	);
-	assert_eq!(gas_left, U256::from(93_818));
+	assert_eq!(gas_left, U256::from(93_814));
 }
 
 // multiplication
@@ -592,7 +592,7 @@ fn math_mul() {
 		U256::from_dec_str("888888888888888888888888888887111111111111111111111111111112").unwrap(),
 		(&result[..]).into()
 	);
-	assert_eq!(gas_left, U256::from(93_304));
+	assert_eq!(gas_left, U256::from(93_300));
 }
 
 // subtraction
@@ -614,7 +614,7 @@ fn math_sub() {
 		U256::from_dec_str("111111111111111111111111111111").unwrap(),
 		(&result[..]).into()
 	);
-	assert_eq!(gas_left, U256::from(93_831));
+	assert_eq!(gas_left, U256::from(93_826));
 }
 
 // subtraction with overflow
@@ -656,7 +656,7 @@ fn math_div() {
 		U256::from_dec_str("1125000").unwrap(),
 		(&result[..]).into()
 	);
-	assert_eq!(gas_left, U256::from(90_607));
+	assert_eq!(gas_left, U256::from(90_603));
 }
 
 #[test]
@@ -684,7 +684,7 @@ fn storage_metering() {
 	};
 
 	// 0 -> not 0
-	assert_eq!(gas_left, U256::from(74_410));
+	assert_eq!(gas_left, U256::from(74_338));
 
 	// #2
 
@@ -703,7 +703,7 @@ fn storage_metering() {
 	};
 
 	// not 0 -> not 0
-	assert_eq!(gas_left, U256::from(89_410));
+	assert_eq!(gas_left, U256::from(89_338));
 }
 
 // This test checks the ability of wasm contract to invoke
@@ -791,7 +791,7 @@ fn externs() {
 		"Gas limit requested and returned does not match"
 	);
 
-	assert_eq!(gas_left, U256::from(92_089));
+	assert_eq!(gas_left, U256::from(92_110));
 }
 
 #[test]
@@ -817,7 +817,7 @@ fn embedded_keccak() {
 	};
 
 	assert_eq!(H256::from_slice(&result), H256::from("68371d7e884c168ae2022c82bd837d51837718a7f7dfb7aa3f753074a35e1d87"));
-	assert_eq!(gas_left, U256::from(84_223));
+	assert_eq!(gas_left, U256::from(84_240));
 }
 
 /// This test checks the correctness of log extern
@@ -852,5 +852,5 @@ fn events() {
 	assert_eq!(&log_entry.data, b"gnihtemos");
 
 	assert_eq!(&result, b"gnihtemos");
-	assert_eq!(gas_left, U256::from(81_235));
+	assert_eq!(gas_left, U256::from(81_292));
 }