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

// SPDX-License-Identifier: Apache-2.0
// This file is part of Frontier.
//
// Copyright (c) 2020-2022 Parity Technologies (UK) Ltd.
//
// 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.

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

extern crate alloc;

#[cfg(test)]
mod mock;

#[cfg(test)]
mod tests;

use alloc::format;
use core::marker::PhantomData;
use fp_evm::{
    ExitError, ExitSucceed, Precompile, PrecompileFailure, PrecompileHandle, PrecompileOutput,
    PrecompileResult,
};
use frame_support::{
    codec::{Decode, DecodeLimit as _},
    dispatch::{DispatchClass, Dispatchable, GetDispatchInfo, Pays, PostDispatchInfo},
    traits::{ConstU32, Get},
};
use pallet_evm::{AddressMapping, GasWeightMapping};

// `DecodeLimit` specifies the max depth a call can use when decoding, as unbounded depth
// can be used to overflow the stack.
// Default value is 8, which is the same as in XCM call decoding.
pub struct Dispatch<T, DispatchValidator = (), DecodeLimit = ConstU32<8>> {
    _marker: PhantomData<(T, DispatchValidator, DecodeLimit)>,
}

impl<T, DispatchValidator, DecodeLimit> Precompile for Dispatch<T, DispatchValidator, DecodeLimit>
where
    T: pallet_evm::Config,
    T::RuntimeCall: Dispatchable<PostInfo = PostDispatchInfo> + GetDispatchInfo + Decode,
    <T::RuntimeCall as Dispatchable>::RuntimeOrigin: From<Option<T::AccountId>>,
    DispatchValidator: DispatchValidateT<T::AccountId, T::RuntimeCall>,
    DecodeLimit: Get<u32>,
{
    fn execute(handle: &mut impl PrecompileHandle) -> PrecompileResult {
        let input = handle.input();
        let target_gas = handle.gas_limit();
        let context = handle.context();

        let call = T::RuntimeCall::decode_with_depth_limit(DecodeLimit::get(), &mut &*input)
            .map_err(|_| PrecompileFailure::Error {
                exit_status: ExitError::Other("decode failed".into()),
            })?;
        let info = call.get_dispatch_info();

        if let Some(gas) = target_gas {
            let valid_weight =
                info.weight.ref_time() <= T::GasWeightMapping::gas_to_weight(gas, false).ref_time();
            if !valid_weight {
                return Err(PrecompileFailure::Error {
                    exit_status: ExitError::OutOfGas,
                })
            }
        }

        let origin = T::AddressMapping::into_account_id(context.caller);

        if let Some(err) = DispatchValidator::validate_before_dispatch(&origin, &call) {
            return Err(err)
        }

        handle
            .record_external_cost(Some(info.weight.ref_time()), Some(info.weight.proof_size()))?;

        match call.dispatch(Some(origin).into()) {
            Ok(post_info) => {
                if post_info.pays_fee(&info) == Pays::Yes {
                    let actual_weight = post_info.actual_weight.unwrap_or(info.weight);
                    let cost = T::GasWeightMapping::weight_to_gas(actual_weight);
                    handle.record_cost(cost)?;

                    handle.refund_external_cost(
                        Some(
                            info.weight
                                .ref_time()
                                .saturating_sub(actual_weight.ref_time()),
                        ),
                        Some(
                            info.weight
                                .proof_size()
                                .saturating_sub(actual_weight.proof_size()),
                        ),
                    );
                }

                Ok(PrecompileOutput {
                    exit_status: ExitSucceed::Stopped,
                    output: Default::default(),
                })
            },
            Err(e) => Err(PrecompileFailure::Error {
                exit_status: ExitError::Other(
                    format!("dispatch execution failed: {}", <&'static str>::from(e)).into(),
                ),
            }),
        }
    }
}

/// Dispatch validation trait.
pub trait DispatchValidateT<AccountId, RuntimeCall> {
    fn validate_before_dispatch(
        origin: &AccountId,
        call: &RuntimeCall,
    ) -> Option<PrecompileFailure>;
}

/// The default implementation of `DispatchValidateT`.
impl<AccountId, RuntimeCall> DispatchValidateT<AccountId, RuntimeCall> for ()
where
    RuntimeCall: GetDispatchInfo,
{
    fn validate_before_dispatch(
        _origin: &AccountId,
        call: &RuntimeCall,
    ) -> Option<PrecompileFailure> {
        let info = call.get_dispatch_info();
        if !(info.pays_fee == Pays::Yes && info.class == DispatchClass::Normal) {
            return Some(PrecompileFailure::Error {
                exit_status: ExitError::Other("invalid call".into()),
            })
        }
        None
    }
}