git.delta.rocks / unique-network / refs/commits / a90a9da574c3

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/mod.rs
@@ -0,0 +1,44 @@
+use pallet_evm::{Precompile, PrecompileHandle, PrecompileResult, PrecompileSet};
+use sp_core::H160;
+use sp_std::marker::PhantomData;
+
+use pallet_evm_precompile_simple::{ECRecover};
+use sr25519::Sr25519Precompile;
+
+mod sr25519;
+mod utils;
+
+pub struct UniquePrecompiles<R>(PhantomData<R>);
+
+impl<R> UniquePrecompiles<R>
+where
+	R: pallet_evm::Config,
+{
+	pub fn new() -> Self {
+		Self(Default::default())
+	}
+	pub fn used_addresses() -> [H160; 2] {
+		[hash(1), hash(20482)]
+	}
+}
+impl<R> PrecompileSet for UniquePrecompiles<R>
+where
+	R: pallet_evm::Config,
+{
+	fn execute(&self, handle: &mut impl PrecompileHandle) -> Option<PrecompileResult> {
+		match handle.code_address() {
+			a if a == hash(1) => Some(ECRecover::execute(handle)),
+			// Sr25519     0x5002
+			a if a == hash(20482) => Some(Sr25519Precompile::<R>::execute(handle)),
+			_ => None,
+		}
+	}
+
+	fn is_precompile(&self, address: H160) -> bool {
+		Self::used_addresses().contains(&address)
+	}
+}
+
+fn hash(a: u64) -> H160 {
+	H160::from_low_u64_be(a)
+}

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/sr25519.rs
@@ -0,0 +1,87 @@
+use fp_evm::{Context, ExitSucceed, PrecompileHandle, PrecompileOutput};
+use pallet_evm::Precompile;
+use sp_core::{crypto::UncheckedFrom, sr25519, H256};
+use sp_std::marker::PhantomData;
+use sp_std::prelude::*;
+
+use super::utils::{Bytes, EvmDataReader, EvmDataWriter, EvmResult, FunctionModifier, Gasometer};
+
+#[precompile_utils_macro::generate_function_selector]
+#[derive(Debug, PartialEq)]
+pub enum Action {
+	Verify = "verify(bytes32,bytes,bytes)",
+}
+
+/// A precompile to wrap substrate sr25519 functions.
+pub struct Sr25519Precompile<Runtime>(PhantomData<Runtime>);
+
+impl<Runtime: pallet_evm::Config> Precompile for Sr25519Precompile<Runtime> {
+	fn execute(handle: &mut impl PrecompileHandle) -> EvmResult<PrecompileOutput> {
+		log::trace!(target: "sr25519-precompile", "In sr25519 precompile");
+
+		let gasometer = Gasometer::new();
+
+		let (mut input, selector) = EvmDataReader::new_with_selector(&gasometer, handle.input())?;
+		let input = &mut input;
+
+		gasometer.check_function_modifier(
+			handle.context(),
+			handle.is_static(),
+			FunctionModifier::View,
+		)?;
+
+		match selector {
+			// Dispatchables
+			Action::Verify => Self::verify(input, &gasometer, handle.context()),
+		}
+	}
+}
+
+impl<Runtime: pallet_evm::Config> Sr25519Precompile<Runtime> {
+	fn verify(
+		input: &mut EvmDataReader,
+		gasometer: &Gasometer,
+		_: &Context,
+	) -> EvmResult<PrecompileOutput> {
+		// Bound check
+		input.expect_arguments(gasometer, 3)?;
+
+		// Parse arguments
+		let public: sr25519::Public =
+			sr25519::Public::unchecked_from(input.read::<H256>(gasometer)?).into();
+		let signature_bytes: Vec<u8> = input.read::<Bytes>(gasometer)?.into();
+		let message: Vec<u8> = input.read::<Bytes>(gasometer)?.into();
+
+		// Parse signature
+		let signature_opt = sr25519::Signature::from_slice(&signature_bytes[..]);
+
+		let signature = if let Some(sig) = signature_opt {
+			sig
+		} else {
+			// Return `false` if signature length is wrong
+			return Ok(PrecompileOutput {
+				exit_status: ExitSucceed::Returned,
+				output: EvmDataWriter::new().write(false).build(),
+			});
+		};
+
+		log::trace!(
+			target: "sr25519-precompile",
+			"Verify signature {:?} for public {:?} and message {:?}",
+			signature, public, message,
+		);
+
+		let is_confirmed = sp_io::crypto::sr25519_verify(&signature, &message[..], &public);
+
+		log::trace!(
+			target: "sr25519-precompile",
+			"Verified signature {:?} is {:?}",
+			signature, is_confirmed,
+		);
+
+		Ok(PrecompileOutput {
+			exit_status: ExitSucceed::Returned,
+			output: EvmDataWriter::new().write(is_confirmed).build(),
+		})
+	}
+}

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/utils/data.rs
@@ -0,0 +1,486 @@
+// Copyright 2019-2022 PureStake Inc.
+// Copyright 2022      Stake Technologies
+// This file is part of Utils package, originally developed by Purestake Inc.
+// Utils package used in Astar Network in terms of GPLv3.
+//
+// Utils is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Utils is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Utils.  If not, see <http://www.gnu.org/licenses/>.
+
+use super::{EvmResult, Gasometer};
+
+use sp_std::borrow::ToOwned;
+use core::{any::type_name, ops::Range};
+use sp_core::{H160, H256, U256};
+use sp_std::{convert::TryInto, vec, vec::Vec};
+
+/// The `address` type of Solidity.
+/// H160 could represent 2 types of data (bytes20 and address) that are not encoded the same way.
+/// To avoid issues writing H160 is thus not supported.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct Address(pub H160);
+
+impl From<H160> for Address {
+	fn from(a: H160) -> Address {
+		Address(a)
+	}
+}
+
+impl From<Address> for H160 {
+	fn from(a: Address) -> H160 {
+		a.0
+	}
+}
+
+/// The `bytes`/`string` type of Solidity.
+/// It is different from `Vec<u8>` which will be serialized with padding for each `u8` element
+/// of the array, while `Bytes` is tightly packed.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Bytes(pub Vec<u8>);
+
+impl From<&[u8]> for Bytes {
+	fn from(a: &[u8]) -> Self {
+		Self(a.to_owned())
+	}
+}
+
+impl From<&str> for Bytes {
+	fn from(a: &str) -> Self {
+		a.as_bytes().into()
+	}
+}
+
+impl Into<Vec<u8>> for Bytes {
+	fn into(self: Self) -> Vec<u8> {
+		self.0
+	}
+}
+
+/// Wrapper around an EVM input slice, helping to parse it.
+/// Provide functions to parse common types.
+#[derive(Clone, Copy, Debug)]
+pub struct EvmDataReader<'a> {
+	input: &'a [u8],
+	cursor: usize,
+}
+
+impl<'a> EvmDataReader<'a> {
+	/// Create a new input parser.
+	pub fn new(input: &'a [u8]) -> Self {
+		Self { input, cursor: 0 }
+	}
+
+	/// Create a new input parser from a selector-initial input.
+	pub fn new_with_selector<T>(gasometer: &Gasometer, input: &'a [u8]) -> EvmResult<(Self, T)>
+	where
+		T: num_enum::TryFromPrimitive<Primitive = u32>,
+	{
+		if input.len() < 4 {
+			return Err(gasometer.revert("tried to parse selector out of bounds"));
+		}
+
+		let mut buffer = [0u8; 4];
+		buffer.copy_from_slice(&input[0..4]);
+		let selector = T::try_from_primitive(u32::from_be_bytes(buffer)).map_err(|_| {
+			log::trace!(
+				target: "precompile-utils",
+				"Failed to match function selector for {}",
+				type_name::<T>()
+			);
+			gasometer.revert("unknown selector")
+		})?;
+
+		Ok((Self::new(&input[4..]), selector))
+	}
+
+	/// Check the input has at least the correct amount of arguments before the end (32 bytes values).
+	pub fn expect_arguments(&self, gasometer: &Gasometer, args: usize) -> EvmResult {
+		if self.input.len() >= self.cursor + args * 32 {
+			Ok(())
+		} else {
+			Err(gasometer.revert("input doesn't match expected length"))
+		}
+	}
+
+	/// Read data from the input.
+	/// Must be provided a gasometer to generate correct Revert errors.
+	/// TODO : Benchmark and add cost of parsing to gasometer ?
+	pub fn read<T: EvmData>(&mut self, gasometer: &Gasometer) -> EvmResult<T> {
+		T::read(self, gasometer)
+	}
+
+	/// Reads a pointer, returning a reader targetting the pointed location.
+	pub fn read_pointer(&mut self, gasometer: &Gasometer) -> EvmResult<Self> {
+		let offset: usize = self
+			.read::<U256>(gasometer)
+			.map_err(|_| gasometer.revert("tried to parse array offset out of bounds"))?
+			.try_into()
+			.map_err(|_| gasometer.revert("array offset is too large"))?;
+
+		if offset >= self.input.len() {
+			return Err(gasometer.revert("pointer points out of bounds"));
+		}
+
+		Ok(Self {
+			input: &self.input[offset..],
+			cursor: 0,
+		})
+	}
+
+	/// Move the reading cursor with provided length, and return a range from the previous cursor
+	/// location to the new one.
+	/// Checks cursor overflows.
+	fn move_cursor(&mut self, gasometer: &Gasometer, len: usize) -> EvmResult<Range<usize>> {
+		let start = self.cursor;
+		let end = self
+			.cursor
+			.checked_add(len)
+			.ok_or_else(|| gasometer.revert("data reading cursor overflow"))?;
+
+		self.cursor = end;
+
+		Ok(start..end)
+	}
+}
+
+/// Help build an EVM input/output data.
+///
+/// Functions takes `self` to allow chaining all calls like
+/// `EvmDataWriter::new().write(...).write(...).build()`.
+/// While it could be more ergonomic to take &mut self, this would
+/// prevent to have a `build` function that don't clone the output.
+#[derive(Clone, Debug)]
+pub struct EvmDataWriter {
+	pub(crate) data: Vec<u8>,
+	offset_data: Vec<OffsetDatum>,
+	selector: Option<u32>,
+}
+
+#[derive(Clone, Debug)]
+struct OffsetDatum {
+	// Offset location in the container data.
+	offset_position: usize,
+	// Data pointed by the offset that must be inserted at the end of container data.
+	data: Vec<u8>,
+	// Inside of arrays, the offset is not from the start of array data (length), but from the start
+	// of the item. This shift allow to correct this.
+	offset_shift: usize,
+}
+
+impl EvmDataWriter {
+	/// Creates a new empty output builder (without selector).
+	pub fn new() -> Self {
+		Self {
+			data: vec![],
+			offset_data: vec![],
+			selector: None,
+		}
+	}
+
+	/// Return the built data.
+	pub fn build(mut self) -> Vec<u8> {
+		Self::bake_offsets(&mut self.data, self.offset_data);
+
+		if let Some(selector) = self.selector {
+			let mut output = selector.to_be_bytes().to_vec();
+			output.append(&mut self.data);
+			output
+		} else {
+			self.data
+		}
+	}
+
+	/// Add offseted data at the end of this writer's data, updating the offsets.
+	fn bake_offsets(output: &mut Vec<u8>, offsets: Vec<OffsetDatum>) {
+		for mut offset_datum in offsets {
+			let offset_position = offset_datum.offset_position;
+			let offset_position_end = offset_position + 32;
+
+			// The offset is the distance between the start of the data and the
+			// start of the pointed data (start of a struct, length of an array).
+			// Offsets in inner data are relative to the start of their respective "container".
+			// However in arrays the "container" is actually the item itself instead of the whole
+			// array, which is corrected by `offset_shift`.
+			let free_space_offset = output.len() - offset_datum.offset_shift;
+
+			// Override dummy offset to the offset it will be in the final output.
+			U256::from(free_space_offset)
+				.to_big_endian(&mut output[offset_position..offset_position_end]);
+
+			// Append this data at the end of the current output.
+			output.append(&mut offset_datum.data);
+		}
+	}
+
+	/// Write arbitrary bytes.
+	/// Doesn't handle any alignement checks, prefer using `write` instead if possible.
+	fn write_raw_bytes(mut self, value: &[u8]) -> Self {
+		self.data.extend_from_slice(value);
+		self
+	}
+
+	/// Write data of requested type.
+	pub fn write<T: EvmData>(mut self, value: T) -> Self {
+		T::write(&mut self, value);
+		self
+	}
+
+	/// Writes a pointer to given data.
+	/// The data will be appended when calling `build`.
+	/// Initially write a dummy value as offset in this writer's data, which will be replaced by
+	/// the correct offset once the pointed data is appended.
+	///
+	/// Takes `&mut self` since its goal is to be used inside `EvmData` impl and not in chains.
+	pub fn write_pointer(&mut self, data: Vec<u8>) {
+		let offset_position = self.data.len();
+		H256::write(self, H256::repeat_byte(0xff));
+
+		self.offset_data.push(OffsetDatum {
+			offset_position,
+			data,
+			offset_shift: 0,
+		});
+	}
+}
+
+impl Default for EvmDataWriter {
+	fn default() -> Self {
+		Self::new()
+	}
+}
+
+/// Data that can be converted from and to EVM data types.
+pub trait EvmData: Sized {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self>;
+	fn write(writer: &mut EvmDataWriter, value: Self);
+}
+
+impl EvmData for H256 {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let range = reader.move_cursor(gasometer, 32)?;
+
+		let data = reader
+			.input
+			.get(range)
+			.ok_or_else(|| gasometer.revert("tried to parse H256 out of bounds"))?;
+
+		Ok(H256::from_slice(data))
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		writer.data.extend_from_slice(value.as_bytes());
+	}
+}
+
+impl EvmData for Address {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let range = reader.move_cursor(gasometer, 32)?;
+
+		let data = reader
+			.input
+			.get(range)
+			.ok_or_else(|| gasometer.revert("tried to parse H160 out of bounds"))?;
+
+		Ok(H160::from_slice(&data[12..32]).into())
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		H256::write(writer, value.0.into());
+	}
+}
+
+impl EvmData for U256 {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let range = reader.move_cursor(gasometer, 32)?;
+
+		let data = reader
+			.input
+			.get(range)
+			.ok_or_else(|| gasometer.revert("tried to parse U256 out of bounds"))?;
+
+		Ok(U256::from_big_endian(data))
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		let mut buffer = [0u8; 32];
+		value.to_big_endian(&mut buffer);
+		writer.data.extend_from_slice(&buffer);
+	}
+}
+
+macro_rules! impl_evmdata_for_uints {
+	($($uint:ty, )*) => {
+		$(
+			impl EvmData for $uint {
+				fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+					let range = reader.move_cursor(gasometer, 32)?;
+
+					let data = reader
+						.input
+						.get(range)
+						.ok_or_else(|| gasometer.revert(alloc::format!(
+							"tried to parse {} out of bounds", core::any::type_name::<Self>()
+						)))?;
+
+					let mut buffer = [0u8; core::mem::size_of::<Self>()];
+					buffer.copy_from_slice(&data[32 - core::mem::size_of::<Self>()..]);
+					Ok(Self::from_be_bytes(buffer))
+				}
+
+				fn write(writer: &mut EvmDataWriter, value: Self) {
+					let mut buffer = [0u8; 32];
+					buffer[32 - core::mem::size_of::<Self>()..].copy_from_slice(&value.to_be_bytes());
+					writer.data.extend_from_slice(&buffer);
+				}
+			}
+		)*
+	};
+}
+
+impl_evmdata_for_uints!(u16, u32, u64, u128,);
+
+// The implementation for u8 is specific, for performance reasons.
+impl EvmData for u8 {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let range = reader.move_cursor(gasometer, 32)?;
+
+		let data = reader
+			.input
+			.get(range)
+			.ok_or_else(|| gasometer.revert("tried to parse u64 out of bounds"))?;
+
+		Ok(data[31])
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		let mut buffer = [0u8; 32];
+		buffer[31] = value;
+
+		writer.data.extend_from_slice(&buffer);
+	}
+}
+
+impl EvmData for bool {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let h256 = H256::read(reader, gasometer)
+			.map_err(|_| gasometer.revert("tried to parse bool out of bounds"))?;
+
+		Ok(!h256.is_zero())
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		let mut buffer = [0u8; 32];
+		if value {
+			buffer[31] = 1;
+		}
+
+		writer.data.extend_from_slice(&buffer);
+	}
+}
+
+impl<T: EvmData> EvmData for Vec<T> {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let mut inner_reader = reader.read_pointer(gasometer)?;
+
+		let array_size: usize = inner_reader
+			.read::<U256>(gasometer)
+			.map_err(|_| gasometer.revert("tried to parse array length out of bounds"))?
+			.try_into()
+			.map_err(|_| gasometer.revert("array length is too large"))?;
+
+		let mut array = vec![];
+
+		let mut item_reader = EvmDataReader {
+			input: inner_reader
+				.input
+				.get(32..)
+				.ok_or_else(|| gasometer.revert("try to read array items out of bound"))?,
+			cursor: 0,
+		};
+
+		for _ in 0..array_size {
+			array.push(item_reader.read(gasometer)?);
+		}
+
+		Ok(array)
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		let mut inner_writer = EvmDataWriter::new().write(U256::from(value.len()));
+
+		for inner in value {
+			// Any offset in items are relative to the start of the item instead of the
+			// start of the array. However if there is offseted data it must but appended after
+			// all items (offsets) are written. We thus need to rely on `compute_offsets` to do
+			// that, and must store a "shift" to correct the offsets.
+			let shift = inner_writer.data.len();
+			let item_writer = EvmDataWriter::new().write(inner);
+
+			inner_writer = inner_writer.write_raw_bytes(&item_writer.data);
+			for mut offset_datum in item_writer.offset_data {
+				offset_datum.offset_shift += 32;
+				offset_datum.offset_position += shift;
+				inner_writer.offset_data.push(offset_datum);
+			}
+		}
+
+		writer.write_pointer(inner_writer.build());
+	}
+}
+
+impl EvmData for Bytes {
+	fn read(reader: &mut EvmDataReader, gasometer: &Gasometer) -> EvmResult<Self> {
+		let mut inner_reader = reader.read_pointer(gasometer)?;
+
+		// Read bytes/string size.
+		let array_size: usize = inner_reader
+			.read::<U256>(gasometer)
+			.map_err(|_| gasometer.revert("tried to parse bytes/string length out of bounds"))?
+			.try_into()
+			.map_err(|_| gasometer.revert("bytes/string length is too large"))?;
+
+		// Get valid range over the bytes data.
+		let range = inner_reader.move_cursor(gasometer, array_size)?;
+
+		let data = inner_reader
+			.input
+			.get(range)
+			.ok_or_else(|| gasometer.revert("tried to parse bytes/string out of bounds"))?;
+
+		let bytes = Self(data.to_owned());
+
+		Ok(bytes)
+	}
+
+	fn write(writer: &mut EvmDataWriter, value: Self) {
+		let length = value.0.len();
+
+		// Pad the data.
+		// Leave it as is if a multiple of 32, otherwise pad to next
+		// multiple or 32.
+		let chunks = length / 32;
+		let padded_size = match length % 32 {
+			0 => chunks * 32,
+			_ => (chunks + 1) * 32,
+		};
+
+		let mut value = value.0.to_vec();
+		value.resize(padded_size, 0);
+
+		writer.write_pointer(
+			EvmDataWriter::new()
+				.write(U256::from(length))
+				.write_raw_bytes(&value)
+				.build(),
+		);
+	}
+}

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/utils/macro/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "precompile-utils-macro"
+authors = [ "StakeTechnologies", "PureStake" ]
+description = ""
+edition = "2018"
+version = "0.1.0"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+num_enum = { version = "0.5.3", default-features = false }
+proc-macro2 = "1.0"
+quote = "1.0"
+sha3 = "0.8"
+syn = { version = "1.0", features = [ "extra-traits", "fold", "full", "visit" ] }

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/utils/macro/src/lib.rs
@@ -0,0 +1,115 @@
+// Copyright 2019-2022 PureStake Inc.
+// Copyright 2022      Stake Technologies
+// This file is part of Utils package, originally developed by Purestake Inc.
+// Utils package used in Astar Network in terms of GPLv3.
+//
+// Utils is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Utils is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Utils.  If not, see <http://www.gnu.org/licenses/>.
+
+#![crate_type = "proc-macro"]
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro2::Literal;
+use quote::{quote, quote_spanned};
+use sha3::{Digest, Keccak256};
+use std::convert::TryInto;
+use syn::{parse_macro_input, spanned::Spanned, Expr, ExprLit, Ident, ItemEnum, Lit};
+
+/// This macro allows to associate to each variant of an enumeration a discriminant (of type u32
+/// whose value corresponds to the first 4 bytes of the Hash Keccak256 of the character string
+///indicated by the user of this macro.
+///
+/// Usage:
+///
+/// ```ignore
+/// #[generate_function_selector]
+/// enum Action {
+/// 	Toto = "toto()",
+/// 	Tata = "tata()",
+/// }
+/// ```
+///
+/// Extanded to:
+///
+/// ```rust
+/// #[repr(u32)]
+/// enum Action {
+/// 	Toto = 119097542u32,
+/// 	Tata = 1414311903u32,
+/// }
+/// ```
+///
+#[proc_macro_attribute]
+pub fn generate_function_selector(_: TokenStream, input: TokenStream) -> TokenStream {
+	let item = parse_macro_input!(input as ItemEnum);
+
+	let ItemEnum {
+		attrs,
+		vis,
+		enum_token,
+		ident,
+		variants,
+		..
+	} = item;
+
+	let mut ident_expressions: Vec<Ident> = vec![];
+	let mut variant_expressions: Vec<Expr> = vec![];
+	for variant in variants {
+		match variant.discriminant {
+			Some((_, Expr::Lit(ExprLit { lit, .. }))) => {
+				if let Lit::Str(lit_str) = lit {
+					let selector = u32::from_be_bytes(
+						Keccak256::digest(lit_str.value().as_ref())[..4]
+							.try_into()
+							.unwrap(),
+					);
+					ident_expressions.push(variant.ident);
+					variant_expressions.push(Expr::Lit(ExprLit {
+						lit: Lit::Verbatim(Literal::u32_suffixed(selector)),
+						attrs: Default::default(),
+					}));
+				} else {
+					return quote_spanned! {
+						lit.span() => compile_error("Expected literal string");
+					}
+					.into();
+				}
+			}
+			Some((_eg, expr)) => {
+				return quote_spanned! {
+					expr.span() => compile_error("Expected literal");
+				}
+				.into()
+			}
+			None => {
+				return quote_spanned! {
+					variant.span() => compile_error("Each variant must have a discriminant");
+				}
+				.into()
+			}
+		}
+	}
+
+	(quote! {
+		#(#attrs)*
+		#[derive(num_enum::TryFromPrimitive, num_enum::IntoPrimitive)]
+		#[repr(u32)]
+		#vis #enum_token #ident {
+			#(
+				#ident_expressions = #variant_expressions,
+			)*
+		}
+	})
+	.into()
+}

--- /dev/null
+++ b/runtime/common/ethereum/precompiles/utils/mod.rs
@@ -0,0 +1,95 @@
+// Copyright 2019-2022 PureStake Inc.
+// Copyright 2022      Stake Technologies
+// This file is part of Utils package, originally developed by Purestake Inc.
+// Utils package used in Astar Network in terms of GPLv3.
+//
+// Utils is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Utils is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Utils.  If not, see <http://www.gnu.org/licenses/>.
+
+use sp_std::borrow::ToOwned;
+use fp_evm::{Context, ExitRevert, PrecompileFailure};
+use sp_core::U256;
+use sp_std::marker::PhantomData;
+
+mod data;
+
+pub use data::{Bytes, EvmData, EvmDataReader, EvmDataWriter};
+
+/// Alias for Result returning an EVM precompile error.
+pub type EvmResult<T = ()> = Result<T, PrecompileFailure>;
+
+/// Helper functions requiring a Runtime.
+/// This runtime must of course implement `pallet_evm::Config`.
+#[derive(Clone, Copy, Debug)]
+pub struct RuntimeHelper<Runtime>(PhantomData<Runtime>);
+
+/// Represents modifiers a Solidity function can be annotated with.
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum FunctionModifier {
+	/// Function that doesn't modify the state.
+	View,
+	/// Function that modifies the state and accept funds.
+	Payable,
+}
+
+/// Custom Gasometer to record costs in precompiles.
+/// It is advised to record known costs as early as possible to
+/// avoid unecessary computations if there is an Out of Gas.
+///
+/// Provides functions related to reverts, as reverts takes the recorded amount
+/// of gas into account.
+#[derive(Clone, Copy, Debug)]
+pub struct Gasometer();
+
+impl Gasometer {
+	/// Create a new Gasometer with provided gas limit.
+	/// None is no limit.
+	pub fn new() -> Self {
+		Self()
+	}
+
+	/// Revert the execution, making the user pay for the the currently
+	/// recorded cost. It is better to **revert** instead of **error** as
+	/// erroring consumes the entire gas limit, and **revert** returns an error
+	/// message to the calling contract.
+	///
+	/// TODO : Record cost of the input based on its size and handle Out of Gas ?
+	/// This might be required if we format revert messages using user data.
+	#[must_use]
+	pub fn revert(&self, output: impl AsRef<[u8]>) -> PrecompileFailure {
+		PrecompileFailure::Revert {
+			exit_status: ExitRevert::Reverted,
+			output: output.as_ref().to_owned(),
+		}
+	}
+
+	#[must_use]
+	/// Check that a function call is compatible with the context it is
+	/// called into.
+	pub fn check_function_modifier(
+		&self,
+		context: &Context,
+		is_static: bool,
+		modifier: FunctionModifier,
+	) -> EvmResult {
+		if is_static && modifier != FunctionModifier::View {
+			return Err(self.revert("can't call non-static function in static context"));
+		}
+
+		if modifier != FunctionModifier::Payable && context.apparent_value > U256::zero() {
+			return Err(self.revert("function is not payable"));
+		}
+
+		Ok(())
+	}
+}