1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147

// This file overrides the default Substrate CheckNonce for Frequency.
// It only creates the token account for paid extrinsics.

// Copyright (C) 2017-2022 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.

use frame_system::Config;
use parity_scale_codec::{Decode, Encode};

use frame_support::{
	dispatch::{DispatchInfo, Pays},
	sp_runtime,
};
use scale_info::TypeInfo;
use sp_runtime::{
	traits::{DispatchInfoOf, Dispatchable, One, SignedExtension},
	transaction_validity::{
		InvalidTransaction, TransactionLongevity, TransactionValidity, TransactionValidityError,
		ValidTransaction,
	},
};
use sp_std::vec;

/// Nonce check and increment to give replay protection for transactions.
///
/// # Transaction Validity
///
/// This extension affects `requires` and `provides` tags of validity, but DOES NOT
/// set the `priority` field. Make sure that AT LEAST one of the signed extension sets
/// some kind of priority upon validating transactions.
#[derive(Encode, Decode, Clone, Eq, PartialEq, TypeInfo)]
#[scale_info(skip_type_params(T))]
pub struct CheckNonce<T: Config>(#[codec(compact)] pub T::Nonce);

impl<T: Config> CheckNonce<T> {
	/// utility constructor. Used only in client/factory code.
	pub fn from(nonce: T::Nonce) -> Self {
		Self(nonce)
	}
}

impl<T: Config> sp_std::fmt::Debug for CheckNonce<T> {
	#[cfg(feature = "std")]
	fn fmt(&self, f: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		write!(f, "CheckNonce({})", self.0)
	}

	#[cfg(not(feature = "std"))]
	fn fmt(&self, _: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
		Ok(())
	}
}

impl<T: Config> SignedExtension for CheckNonce<T>
where
	T::RuntimeCall: Dispatchable<Info = DispatchInfo>,
{
	type AccountId = T::AccountId;
	type Call = T::RuntimeCall;
	type AdditionalSigned = ();
	type Pre = ();
	const IDENTIFIER: &'static str = "CheckNonce";

	fn additional_signed(&self) -> sp_std::result::Result<(), TransactionValidityError> {
		Ok(())
	}

	fn pre_dispatch(
		self,
		who: &Self::AccountId,
		_call: &Self::Call,
		info: &DispatchInfoOf<Self::Call>,
		_len: usize,
	) -> Result<(), TransactionValidityError> {
		// Get TOKEN account from "who" key
		let mut account = frame_system::Account::<T>::get(who);

		// The default account (no account) has a nonce of 0.
		// If account nonce is not equal to the tx nonce (self.0), the tx is invalid.  Therefore, check if it is a stale or future tx.
		if self.0 != account.nonce {
			return Err(if self.0 < account.nonce {
				InvalidTransaction::Stale
			} else {
				InvalidTransaction::Future
			}
			.into())
		}

		// Is this an existing account?
		// extracted from the conditions in which an account gets reaped
		// https://github.com/paritytech/polkadot-sdk/commit/e993f884fc00f359dd8bf9c81422c5161f3447b5#diff-dff2afa7433478e36eb66a9fe319efe28cfbdf95104b30b03afa0a1c4e3239f3R1082
		let existing_account =
			account.providers > 0 || account.consumers > 0 || account.sufficients > 0;

		// Increment account nonce by 1
		account.nonce += T::Nonce::one();

		// Only create or update the token account if the caller is paying or
		// account already exists
		if info.pays_fee == Pays::Yes || existing_account {
			frame_system::Account::<T>::insert(who, account);
		}

		Ok(())
	}

	fn validate(
		&self,
		who: &Self::AccountId,
		_call: &Self::Call,
		_info: &DispatchInfoOf<Self::Call>,
		_len: usize,
	) -> TransactionValidity {
		// check index
		let account = frame_system::Account::<T>::get(who);
		if self.0 < account.nonce {
			return InvalidTransaction::Stale.into()
		}

		let provides = vec![Encode::encode(&(who, self.0))];
		let requires = if account.nonce < self.0 {
			vec![Encode::encode(&(who, self.0 - One::one()))]
		} else {
			vec![]
		};

		Ok(ValidTransaction {
			priority: 0,
			requires,
			provides,
			longevity: TransactionLongevity::max_value(),
			propagate: true,
		})
	}
}