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
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
// This file is part of Substrate.

// Copyright (C) 2021-2021 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.

//! Compact proof support.
//!
//! This uses compact proof from trie crate and extends
//! it to substrate specific layout and child trie system.

use crate::{
	CompactProof, HashDBT, StorageProof, TrieConfiguration, TrieError, TrieHash, EMPTY_PREFIX,
};
use sp_std::{boxed::Box, vec::Vec};
#[cfg(feature = "std")]
use std::error::Error as StdError;
#[cfg(feature = "std")]
use std::fmt;
use trie_db::Trie;

/// Error for trie node decoding.
pub enum Error<L: TrieConfiguration> {
	/// Verification failed due to root mismatch.
	RootMismatch(TrieHash<L>, TrieHash<L>),
	/// Missing nodes in proof.
	IncompleteProof,
	/// Compact node is not needed.
	ExtraneousChildNode,
	/// Child content with root not in proof.
	ExtraneousChildProof(TrieHash<L>),
	/// Bad child trie root.
	InvalidChildRoot(Vec<u8>, Vec<u8>),
	/// Errors from trie crate.
	TrieError(Box<TrieError<L>>),
}

impl<L: TrieConfiguration> From<Box<TrieError<L>>> for Error<L> {
	fn from(error: Box<TrieError<L>>) -> Self {
		Error::TrieError(error)
	}
}

#[cfg(feature = "std")]
impl<L: TrieConfiguration> StdError for Error<L> {
	fn description(&self) -> &str {
		match self {
			Error::InvalidChildRoot(..) => "Invalid child root error",
			Error::TrieError(..) => "Trie db error",
			Error::RootMismatch(..) => "Trie db error",
			Error::IncompleteProof => "Incomplete proof",
			Error::ExtraneousChildNode => "Extraneous child node",
			Error::ExtraneousChildProof(..) => "Extraneous child proof",
		}
	}
}

#[cfg(feature = "std")]
impl<L: TrieConfiguration> fmt::Debug for Error<L> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		<Self as fmt::Display>::fmt(&self, f)
	}
}

#[cfg(feature = "std")]
impl<L: TrieConfiguration> fmt::Display for Error<L> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		match self {
			Error::InvalidChildRoot(k, v) => write!(f, "InvalidChildRoot at {:x?}: {:x?}", k, v),
			Error::TrieError(e) => write!(f, "Trie error: {}", e),
			Error::IncompleteProof => write!(f, "Incomplete proof"),
			Error::ExtraneousChildNode => write!(f, "Child node content with no root in proof"),
			Error::ExtraneousChildProof(root) => {
				write!(f, "Proof of child trie {:x?} not in parent proof", root.as_ref())
			},
			Error::RootMismatch(root, expected) => write!(
				f,
				"Verification error, root is {:x?}, expected: {:x?}",
				root.as_ref(),
				expected.as_ref(),
			),
		}
	}
}

/// Decode a compact proof.
///
/// Takes as input a destination `db` for decoded node and `encoded`
/// an iterator of compact encoded nodes.
///
/// Child trie are decoded in order of child trie root present
/// in the top trie.
pub fn decode_compact<'a, L, DB, I>(
	db: &mut DB,
	encoded: I,
	expected_root: Option<&TrieHash<L>>,
) -> Result<TrieHash<L>, Error<L>>
where
	L: TrieConfiguration,
	DB: HashDBT<L::Hash, trie_db::DBValue> + hash_db::HashDBRef<L::Hash, trie_db::DBValue>,
	I: IntoIterator<Item = &'a [u8]>,
{
	let mut nodes_iter = encoded.into_iter();
	let (top_root, _nb_used) =
		trie_db::decode_compact_from_iter::<L, _, _, _>(db, &mut nodes_iter)?;

	// Only check root if expected root is passed as argument.
	if let Some(expected_root) = expected_root {
		if expected_root != &top_root {
			return Err(Error::RootMismatch(top_root.clone(), expected_root.clone()))
		}
	}

	let mut child_tries = Vec::new();
	{
		// fetch child trie roots
		let trie = crate::TrieDB::<L>::new(db, &top_root)?;

		let mut iter = trie.iter()?;

		let childtrie_roots = sp_core::storage::well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX;
		if iter.seek(childtrie_roots).is_ok() {
			loop {
				match iter.next() {
					Some(Ok((key, value))) if key.starts_with(childtrie_roots) => {
						// we expect all default child trie root to be correctly encoded.
						// see other child trie functions.
						let mut root = TrieHash::<L>::default();
						// still in a proof so prevent panic
						if root.as_mut().len() != value.as_slice().len() {
							return Err(Error::InvalidChildRoot(key, value))
						}
						root.as_mut().copy_from_slice(value.as_ref());
						child_tries.push(root);
					},
					// allow incomplete database error: we only
					// require access to data in the proof.
					Some(Err(error)) => match *error {
						trie_db::TrieError::IncompleteDatabase(..) => (),
						e => return Err(Box::new(e).into()),
					},
					_ => break,
				}
			}
		}
	}

	if !HashDBT::<L::Hash, _>::contains(db, &top_root, EMPTY_PREFIX) {
		return Err(Error::IncompleteProof)
	}

	let mut previous_extracted_child_trie = None;
	let mut nodes_iter = nodes_iter.peekable();
	for child_root in child_tries.into_iter() {
		if previous_extracted_child_trie.is_none() && nodes_iter.peek().is_some() {
			let (top_root, _) =
				trie_db::decode_compact_from_iter::<L, _, _, _>(db, &mut nodes_iter)?;
			previous_extracted_child_trie = Some(top_root);
		}

		// we do not early exit on root mismatch but try the
		// other read from proof (some child root may be
		// in proof without actual child content).
		if Some(child_root) == previous_extracted_child_trie {
			previous_extracted_child_trie = None;
		}
	}

	if let Some(child_root) = previous_extracted_child_trie {
		// A child root was read from proof but is not present
		// in top trie.
		return Err(Error::ExtraneousChildProof(child_root))
	}

	if nodes_iter.next().is_some() {
		return Err(Error::ExtraneousChildNode)
	}

	Ok(top_root)
}

/// Encode a compact proof.
///
/// Takes as input all full encoded node from the proof, and
/// the root.
/// Then parse all child trie root and compress main trie content first
/// then all child trie contents.
/// Child trie are ordered by the order of their roots in the top trie.
pub fn encode_compact<L>(proof: StorageProof, root: TrieHash<L>) -> Result<CompactProof, Error<L>>
where
	L: TrieConfiguration,
{
	let mut child_tries = Vec::new();
	let partial_db = proof.into_memory_db();
	let mut compact_proof = {
		let trie = crate::TrieDB::<L>::new(&partial_db, &root)?;

		let mut iter = trie.iter()?;

		let childtrie_roots = sp_core::storage::well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX;
		if iter.seek(childtrie_roots).is_ok() {
			loop {
				match iter.next() {
					Some(Ok((key, value))) if key.starts_with(childtrie_roots) => {
						let mut root = TrieHash::<L>::default();
						if root.as_mut().len() != value.as_slice().len() {
							// some child trie root in top trie are not an encoded hash.
							return Err(Error::InvalidChildRoot(key.to_vec(), value.to_vec()))
						}
						root.as_mut().copy_from_slice(value.as_ref());
						child_tries.push(root);
					},
					// allow incomplete database error: we only
					// require access to data in the proof.
					Some(Err(error)) => match *error {
						trie_db::TrieError::IncompleteDatabase(..) => (),
						e => return Err(Box::new(e).into()),
					},
					_ => break,
				}
			}
		}

		trie_db::encode_compact::<L>(&trie)?
	};

	for child_root in child_tries {
		if !HashDBT::<L::Hash, _>::contains(&partial_db, &child_root, EMPTY_PREFIX) {
			// child proof are allowed to be missing (unused root can be included
			// due to trie structure modification).
			continue
		}

		let trie = crate::TrieDB::<L>::new(&partial_db, &child_root)?;
		let child_proof = trie_db::encode_compact::<L>(&trie)?;

		compact_proof.extend(child_proof);
	}

	Ok(CompactProof { encoded_nodes: compact_proof })
}