lib.rs

// Copyright 2018-2020 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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.

// Substrate 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 Substrate. If not, see <http://www.gnu.org/licenses/>.

//! # Contract Module
//!
//! The Contract module provides functionality for the runtime to deploy and execute WebAssembly smart-contracts.
//!
//! - [`contract::Trait`](./trait.Trait.html)
//! - [`Call`](./enum.Call.html)
//!
//! ## Overview
//!
//! This module extends accounts based on the `Currency` trait to have smart-contract functionality. It can
//! be used with other modules that implement accounts based on `Currency`. These "smart-contract accounts"
//! have the ability to instantiate smart-contracts and make calls to other contract and non-contract accounts.
//!
//! The smart-contract code is stored once in a `code_cache`, and later retrievable via its `code_hash`.
//! This means that multiple smart-contracts can be instantiated from the same `code_cache`, without replicating
//! the code each time.
//!
//! When a smart-contract is called, its associated code is retrieved via the code hash and gets executed.
//! This call can alter the storage entries of the smart-contract account, instantiate new smart-contracts,
//! or call other smart-contracts.
//!
//! Finally, when an account is reaped, its associated code and storage of the smart-contract account
//! will also be deleted.
//!
//! ### Gas
//!
//! Senders must specify a gas limit with every call, as all instructions invoked by the smart-contract require gas.
//! Unused gas is refunded after the call, regardless of the execution outcome.
//!
//! If the gas limit is reached, then all calls and state changes (including balance transfers) are only
//! reverted at the current call's contract level. For example, if contract A calls B and B runs out of gas mid-call,
//! then all of B's calls are reverted. Assuming correct error handling by contract A, A's other calls and state
//! changes still persist.
//!
//! ### Notable Scenarios
//!
//! Contract call failures are not always cascading. When failures occur in a sub-call, they do not "bubble up",
//! and the call will only revert at the specific contract level. For example, if contract A calls contract B, and B
//! fails, A can decide how to handle that failure, either proceeding or reverting A's changes.
//!
//! ## Interface
//!
//! ### Dispatchable functions
//!
//! * `put_code` - Stores the given binary Wasm code into the chain's storage and returns its `code_hash`.
//! * `instantiate` - Deploys a new contract from the given `code_hash`, optionally transferring some balance.
//! This instantiates a new smart contract account and calls its contract deploy handler to
//! initialize the contract.
//! * `call` - Makes a call to an account, optionally transferring some balance.
//!
//! ### Signed Extensions
//!
//! The contracts module defines the following extension:
//!
//!   - [`CheckBlockGasLimit`]: Ensures that the transaction does not exceeds the block gas limit.
//!
//! The signed extension needs to be added as signed extra to the transaction type to be used in the
//! runtime.
//!
//! ## Usage
//!
//! The Contract module is a work in progress. The following examples show how this Contract module
//! can be used to instantiate and call contracts.
//!
//! * [`ink`](https://github.com/paritytech/ink) is
//! an [`eDSL`](https://wiki.haskell.org/Embedded_domain_specific_language) that enables writing
//! WebAssembly based smart contracts in the Rust programming language. This is a work in progress.
//!
//! ## Related Modules
//!
//! * [Balances](../pallet_balances/index.html)

#![cfg_attr(not(feature = "std"), no_std)]

#[macro_use]
mod gas;

mod account_db;
mod exec;
mod wasm;
mod rent;

#[cfg(test)]
mod tests;

use crate::exec::ExecutionContext;
use crate::account_db::{AccountDb, DirectAccountDb};
use crate::wasm::{WasmLoader, WasmVm};

pub use crate::gas::{Gas, GasMeter};
pub use crate::exec::{ExecResult, ExecReturnValue, ExecError, StatusCode};

#[cfg(feature = "std")]
use serde::{Serialize, Deserialize};
use sp_core::crypto::UncheckedFrom;
use sp_std::{prelude::*, marker::PhantomData, fmt::Debug};
use codec::{Codec, Encode, Decode};
use sp_io::hashing::blake2_256;
use sp_runtime::{
	traits::{Hash, StaticLookup, Zero, MaybeSerializeDeserialize, Member, SignedExtension},
	transaction_validity::{
		ValidTransaction, InvalidTransaction, TransactionValidity, TransactionValidityError,
	},
	RuntimeDebug,
};
use frame_support::dispatch::{DispatchResult, Dispatchable};
use frame_support::{
	Parameter, decl_module, decl_event, decl_storage, decl_error, storage::child,
	parameter_types, IsSubType,
	weights::DispatchInfo,
};
use frame_support::traits::{OnFreeBalanceZero, OnUnbalanced, Currency, Get, Time, Randomness};
use frame_system::{self as system, ensure_signed, RawOrigin, ensure_root};
use sp_core::storage::well_known_keys::CHILD_STORAGE_KEY_PREFIX;

pub type CodeHash<T> = <T as frame_system::Trait>::Hash;
pub type TrieId = Vec<u8>;

/// A function that generates an `AccountId` for a contract upon instantiation.
pub trait ContractAddressFor<CodeHash, AccountId> {
	fn contract_address_for(code_hash: &CodeHash, data: &[u8], origin: &AccountId) -> AccountId;
}

/// A function that returns the fee for dispatching a `Call`.
pub trait ComputeDispatchFee<Call, Balance> {
	fn compute_dispatch_fee(call: &Call) -> Balance;
}

/// Information for managing an acocunt and its sub trie abstraction.
/// This is the required info to cache for an account
#[derive(Encode, Decode, RuntimeDebug)]
pub enum ContractInfo<T: Trait> {
	Alive(AliveContractInfo<T>),
	Tombstone(TombstoneContractInfo<T>),
}

impl<T: Trait> ContractInfo<T> {
	/// If contract is alive then return some alive info
	pub fn get_alive(self) -> Option<AliveContractInfo<T>> {
		if let ContractInfo::Alive(alive) = self {
			Some(alive)
		} else {
			None
		}
	}
	/// If contract is alive then return some reference to alive info
	pub fn as_alive(&self) -> Option<&AliveContractInfo<T>> {
		if let ContractInfo::Alive(ref alive) = self {
			Some(alive)
		} else {
			None
		}
	}
	/// If contract is alive then return some mutable reference to alive info
	pub fn as_alive_mut(&mut self) -> Option<&mut AliveContractInfo<T>> {
		if let ContractInfo::Alive(ref mut alive) = self {
			Some(alive)
		} else {
			None
		}
	}

	/// If contract is tombstone then return some tombstone info
	pub fn get_tombstone(self) -> Option<TombstoneContractInfo<T>> {
		if let ContractInfo::Tombstone(tombstone) = self {
			Some(tombstone)
		} else {
			None
		}
	}
	/// If contract is tombstone then return some reference to tombstone info
	pub fn as_tombstone(&self) -> Option<&TombstoneContractInfo<T>> {
		if let ContractInfo::Tombstone(ref tombstone) = self {
			Some(tombstone)
		} else {
			None
		}
	}
	/// If contract is tombstone then return some mutable reference to tombstone info
	pub fn as_tombstone_mut(&mut self) -> Option<&mut TombstoneContractInfo<T>> {
		if let ContractInfo::Tombstone(ref mut tombstone) = self {
			Some(tombstone)
		} else {
			None