referrerpolicy=no-referrer-when-downgrade
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

// This file is part of Substrate.

// Copyright (C) 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 crate::builder::MetadataExtraInfo;
use codec::{Decode, Encode};
use frame_metadata::{RuntimeMetadata, RuntimeMetadataPrefixed};
use merkleized_metadata::{generate_metadata_digest, ExtraInfo};
use sc_executor::WasmExecutor;
use sp_core::traits::{CallContext, CodeExecutor, RuntimeCode, WrappedRuntimeCode};
use std::path::Path;

/// The host functions that we provide when calling into the wasm file.
///
/// Any other host function will return an error.
type HostFunctions = (
	// The allocator functions.
	sp_io::allocator::HostFunctions,
	// Logging is good to have for debugging issues.
	sp_io::logging::HostFunctions,
	// Give access to the "state", actually the state will be empty, but some chains put constants
	// into the state and this would panic at metadata generation. Thus, we give them an empty
	// state to not panic.
	sp_io::storage::HostFunctions,
	// The hashing functions.
	sp_io::hashing::HostFunctions,
);

/// Generate the metadata hash.
///
/// The metadata hash is generated as specced in
/// [RFC78](https://polkadot-fellows.github.io/RFCs/approved/0078-merkleized-metadata.html).
///
/// Returns the metadata hash.
pub fn generate_metadata_hash(wasm: &Path, extra_info: MetadataExtraInfo) -> [u8; 32] {
	sp_tracing::try_init_simple();

	let wasm = std::fs::read(wasm).expect("Wasm file was just created and should be readable.");

	let executor = WasmExecutor::<HostFunctions>::builder()
		.with_allow_missing_host_functions(true)
		.build();

	let runtime_code = RuntimeCode {
		code_fetcher: &WrappedRuntimeCode(wasm.into()),
		heap_pages: None,
		// The hash is only used for caching and thus, not that important for our use case here.
		hash: vec![1, 2, 3],
	};

	let metadata = executor
		.call(
			&mut sp_io::TestExternalities::default().ext(),
			&runtime_code,
			"Metadata_metadata_at_version",
			&15u32.encode(),
			CallContext::Offchain,
		)
		.0
		.expect("`Metadata::metadata_at_version` should exist.");

	let metadata = Option::<Vec<u8>>::decode(&mut &metadata[..])
		.ok()
		.flatten()
		.expect("Metadata V15 support is required.");

	let metadata = RuntimeMetadataPrefixed::decode(&mut &metadata[..])
		.expect("Invalid encoded metadata?")
		.1;

	let runtime_version = executor
		.call(
			&mut sp_io::TestExternalities::default().ext(),
			&runtime_code,
			"Core_version",
			&[],
			CallContext::Offchain,
		)
		.0
		.expect("`Core_version` should exist.");
	let runtime_version = sp_version::RuntimeVersion::decode(&mut &runtime_version[..])
		.expect("Invalid `RuntimeVersion` encoding");

	let base58_prefix = extract_ss58_prefix(&metadata);

	let extra_info = ExtraInfo {
		spec_version: runtime_version.spec_version,
		spec_name: runtime_version.spec_name.into(),
		base58_prefix,
		decimals: extra_info.decimals,
		token_symbol: extra_info.token_symbol,
	};

	generate_metadata_digest(&metadata, extra_info)
		.expect("Failed to generate the metadata digest")
		.hash()
}

/// Extract the `SS58` from the constants in the given `metadata`.
fn extract_ss58_prefix(metadata: &RuntimeMetadata) -> u16 {
	let RuntimeMetadata::V15(ref metadata) = metadata else {
		panic!("Metadata version 15 required")
	};

	let system = metadata
		.pallets
		.iter()
		.find(|p| p.name == "System")
		.expect("Each FRAME runtime has the `System` pallet; qed");

	system
		.constants
		.iter()
		.find_map(|c| {
			(c.name == "SS58Prefix")
				.then(|| u16::decode(&mut &c.value[..]).expect("SS58 is an `u16`; qed"))
		})
		.expect("`SS58PREFIX` exists in the `System` constants; qed")
}