contracts: Don't rely on reserved balances keeping an account alive (#13369)

* Move storage deposits to their own account

* Take ed for contract's account from origin

* Apply suggestions from code review

Co-authored-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

* Update stale docs

* Use 16 bytes prefix for address derivation

* Update frame/contracts/src/address.rs

Co-authored-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* Fix merge

* ".git/.scripts/commands/bench/bench.sh" pallet dev pallet_contracts

* Update frame/contracts/primitives/src/lib.rs

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

---------

Co-authored-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>
Co-authored-by: command-bot <>

substrate/frame/contracts/src/address.rs

@@ -0,0 +1,81 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2018-2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Functions that deal with address derivation.
+
+use crate::{CodeHash, Config};
+use codec::{Decode, Encode};
+use sp_runtime::traits::{Hash, TrailingZeroInput};
+
+/// Provides the contract address generation method.
+///
+/// See [`DefaultAddressGenerator`] for the default implementation.
+///
+/// # Note for implementors
+///
+/// 1. Make sure that there are no collisions, different inputs never lead to the same output.
+/// 2. Make sure that the same inputs lead to the same output.
+pub trait AddressGenerator<T: Config> {
+	/// The address of a contract based on the given instantiate parameters.
+	///
+	/// Changing the formular for an already deployed chain is fine as long as no collisons
+	/// with the old formular. Changes only affect existing contracts.
+	fn contract_address(
+		deploying_address: &T::AccountId,
+		code_hash: &CodeHash<T>,
+		input_data: &[u8],
+		salt: &[u8],
+	) -> T::AccountId;
+
+	/// The address of the deposit account of `contract_addr`.
+	///
+	/// The address is generated once on instantiation and then stored in the contracts
+	/// metadata. Hence changes do only affect newly created contracts.
+	fn deposit_address(contract_addr: &T::AccountId) -> T::AccountId;
+}
+
+/// Default address generator.
+///
+/// This is the default address generator used by contract instantiation. Its result
+/// is only dependent on its inputs. It can therefore be used to reliably predict the
+/// address of a contract. This is akin to the formula of eth's CREATE2 opcode. There
+/// is no CREATE equivalent because CREATE2 is strictly more powerful.
+/// Formula:
+/// `hash("contract_addr_v1" ++ deploying_address ++ code_hash ++ input_data ++ salt)`
+pub struct DefaultAddressGenerator;
+
+impl<T: Config> AddressGenerator<T> for DefaultAddressGenerator {
+	/// Formula: `hash("contract_addr_v1" ++ deploying_address ++ code_hash ++ input_data ++ salt)`
+	fn contract_address(
+		deploying_address: &T::AccountId,
+		code_hash: &CodeHash<T>,
+		input_data: &[u8],
+		salt: &[u8],
+	) -> T::AccountId {
+		let entropy = (b"contract_addr_v1", deploying_address, code_hash, input_data, salt)
+			.using_encoded(T::Hashing::hash);
+		Decode::decode(&mut TrailingZeroInput::new(entropy.as_ref()))
+			.expect("infinite length input; no invalid inputs for type; qed")
+	}
+
+	/// Formula: `hash("contract_depo_v1" ++ contract_addr)`
+	fn deposit_address(contract_addr: &T::AccountId) -> T::AccountId {
+		let entropy = (b"contract_depo_v1", contract_addr).using_encoded(T::Hashing::hash);
+		Decode::decode(&mut TrailingZeroInput::new(entropy.as_ref()))
+			.expect("infinite length input; no invalid inputs for type; qed")
+	}
+}