[stable] Fixed modexp gas calculation overflow (#6741) (#6746)

* Fixed modexp gas calculation overflow (#6741)

* v1.7.6

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 description = "Parity Ethereum client"
 name = "parity"
-version = "1.7.5"
+version = "1.7.6"
 license = "GPL-3.0"
 authors = ["Parity Technologies <[email protected]>"]
 build = "build.rs"

ethcore/src/builtin.rs

@@ -120,7 +120,11 @@ impl Pricer for ModexpPricer {
 
 		let adjusted_exp_len = Self::adjusted_exp_len(exp_len, exp_low);
 
-		(Self::mult_complexity(m) * max(adjusted_exp_len, 1) / self.divisor as u64).into()
+		let (gas, overflow) = Self::mult_complexity(m).overflowing_mul(max(adjusted_exp_len, 1));
+		if overflow {
+			return U256::max_value();
+		}
+		(gas / self.divisor as u64).into()
 	}
 }
 
@@ -711,6 +715,14 @@ mod tests {
 			activate_at: 0,
 		};
 
+		// test for potential gas cost multiplication overflow
+		{
+			let input = FromHex::from_hex("0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000003b27bafd00000000000000000000000000000000000000000000000000000000503c8ac3").unwrap();
+			let expected_cost = U256::max_value();
+			assert_eq!(f.cost(&input[..]), expected_cost.into());
+		}
+
+
 		// test for potential exp len overflow
 		{
 			let input = FromHex::from_hex("\

mac/Parity.pkgproj

@@ -462,7 +462,7 @@
 				<key>OVERWRITE_PERMISSIONS</key>
 				<false/>
 				<key>VERSION</key>
-				<string>1.7.5</string>
+				<string>1.7.6</string>
 			</dict>
 			<key>UUID</key>
 			<string>2DCD5B81-7BAF-4DA1-9251-6274B089FD36</string>

nsis/installer.nsi

@@ -10,7 +10,7 @@
 !define DESCRIPTION "Fast, light, robust Ethereum implementation"
 !define VERSIONMAJOR 1
 !define VERSIONMINOR 7
-!define VERSIONBUILD 5
+!define VERSIONBUILD 6
 !define ARGS "--warp"
 !define FIRST_START_ARGS "ui --warp --mode=passive"
 

util/Cargo.toml

@@ -3,7 +3,7 @@ description = "Ethcore utility library"
 homepage = "http://parity.io"
 license = "GPL-3.0"
 name = "ethcore-util"
-version = "1.7.5"
+version = "1.7.6"
 authors = ["Parity Technologies <[email protected]>"]
 build = "build.rs"