From 5947d433f7cee90f76c2ef2043af0ce932faedb1 Mon Sep 17 00:00:00 2001
From: Wei Tang <wei@that.world>
Date: Thu, 30 Jul 2020 15:52:16 +0200
Subject: [PATCH] pallet-evm: add builtin support for the four basic Ethereum
 precompiles (#6743)

* pallet-evm: add builtin support for the four basic Ethereum precompiles

* linear_cost -> ensure_linear_cost to directly return OutOfGas error
---
 Cargo.toml         |  2 +
 src/lib.rs         |  2 +-
 src/precompiles.rs | 99 +++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 101 insertions(+), 2 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index a5ec28ddf9c3b..43ecc6f3688cf 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,6 +27,7 @@ rlp = { version = "0.4", default-features = false }
 evm = { version = "0.17", default-features = false }
 sha3 = { version = "0.8", default-features = false }
 impl-trait-for-tuples = "0.1"
+ripemd160 = { version = "0.9", default-features = false }
 
 [features]
 default = ["std"]
@@ -45,4 +46,5 @@ std = [
 	"primitive-types/std",
 	"evm/std",
 	"pallet-timestamp/std",
+	"ripemd160/std",
 ]
diff --git a/src/lib.rs b/src/lib.rs
index 0cbeac6fe2d6f..0dcc4526c7fbc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -21,8 +21,8 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 mod backend;
-mod precompiles;
 mod tests;
+pub mod precompiles;
 
 pub use crate::precompiles::{Precompile, Precompiles};
 pub use crate::backend::{Account, Log, Vicinity, Backend};
diff --git a/src/precompiles.rs b/src/precompiles.rs
index a6a10d45a2083..987724285d7b8 100644
--- a/src/precompiles.rs
+++ b/src/precompiles.rs
@@ -15,9 +15,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use sp_std::vec::Vec;
+//! Builtin precompiles.
+
+use sp_std::{cmp::min, vec::Vec};
 use sp_core::H160;
 use evm::{ExitError, ExitSucceed};
+use ripemd160::Digest;
 use impl_trait_for_tuples::impl_for_tuples;
 
 /// Custom precompiles to be used by EVM engine.
@@ -67,3 +70,97 @@ impl Precompiles for Tuple {
 		None
 	}
 }
+
+/// Linear gas cost
+fn ensure_linear_cost(
+	target_gas: Option<usize>,
+	len: usize,
+	base: usize,
+	word: usize
+) -> Result<usize, ExitError> {
+	let cost = base.checked_add(
+		word.checked_mul(len.saturating_add(31) / 32).ok_or(ExitError::OutOfGas)?
+	).ok_or(ExitError::OutOfGas)?;
+
+	if let Some(target_gas) = target_gas {
+		if cost > target_gas {
+			return Err(ExitError::OutOfGas)
+		}
+	}
+
+	Ok(cost)
+}
+
+/// The identity precompile.
+pub struct Identity;
+
+impl Precompile for Identity {
+	fn execute(
+		input: &[u8],
+		target_gas: Option<usize>,
+	) -> core::result::Result<(ExitSucceed, Vec<u8>, usize), ExitError> {
+		let cost = ensure_linear_cost(target_gas, input.len(), 15, 3)?;
+
+		Ok((ExitSucceed::Returned, input.to_vec(), cost))
+	}
+}
+
+/// The ecrecover precompile.
+pub struct ECRecover;
+
+impl Precompile for ECRecover {
+	fn execute(
+		i: &[u8],
+		target_gas: Option<usize>,
+	) -> core::result::Result<(ExitSucceed, Vec<u8>, usize), ExitError> {
+		let cost = ensure_linear_cost(target_gas, i.len(), 3000, 0)?;
+
+		let mut input = [0u8; 128];
+		input[..min(i.len(), 128)].copy_from_slice(&i[..min(i.len(), 128)]);
+
+		let mut msg = [0u8; 32];
+		let mut sig = [0u8; 65];
+
+		msg[0..32].copy_from_slice(&input[0..32]);
+		sig[0..32].copy_from_slice(&input[64..96]);
+		sig[32..64].copy_from_slice(&input[96..128]);
+		sig[64] = input[63];
+
+		let pubkey = sp_io::crypto::secp256k1_ecdsa_recover(&sig, &msg)
+			.map_err(|_| ExitError::Other("Public key recover failed"))?;
+		let mut address = sp_io::hashing::keccak_256(&pubkey);
+		address[0..12].copy_from_slice(&[0u8; 12]);
+
+		Ok((ExitSucceed::Returned, address.to_vec(), cost))
+	}
+}
+
+/// The ripemd precompile.
+pub struct Ripemd160;
+
+impl Precompile for Ripemd160 {
+	fn execute(
+		input: &[u8],
+		target_gas: Option<usize>,
+	) -> core::result::Result<(ExitSucceed, Vec<u8>, usize), ExitError> {
+		let cost = ensure_linear_cost(target_gas, input.len(), 600, 120)?;
+
+		let ret = ripemd160::Ripemd160::digest(input).to_vec();
+		Ok((ExitSucceed::Returned, ret, cost))
+	}
+}
+
+/// The sha256 precompile.
+pub struct Sha256;
+
+impl Precompile for Sha256 {
+	fn execute(
+		input: &[u8],
+		target_gas: Option<usize>,
+	) -> core::result::Result<(ExitSucceed, Vec<u8>, usize), ExitError> {
+		let cost = ensure_linear_cost(target_gas, input.len(), 60, 12)?;
+
+		let ret = sp_io::hashing::sha2_256(input);
+		Ok((ExitSucceed::Returned, ret.to_vec(), cost))
+	}
+}