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proof.go
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proof.go
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// (c) 2020-2021, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package trie
import (
"bytes"
"errors"
"fmt"
"github.com/ava-labs/subnet-evm/core/rawdb"
"github.com/ava-labs/subnet-evm/ethdb"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/log"
)
// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
// Collect all nodes on the path to key.
var (
prefix []byte
nodes []node
tn = t.root
)
key = keybytesToHex(key)
for len(key) > 0 && tn != nil {
switch n := tn.(type) {
case *shortNode:
if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
// The trie doesn't contain the key.
tn = nil
} else {
tn = n.Val
prefix = append(prefix, n.Key...)
key = key[len(n.Key):]
}
nodes = append(nodes, n)
case *fullNode:
tn = n.Children[key[0]]
prefix = append(prefix, key[0])
key = key[1:]
nodes = append(nodes, n)
case hashNode:
var err error
tn, err = t.resolveHash(n, prefix)
if err != nil {
log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
return err
}
default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
hasher := newHasher(false)
defer returnHasherToPool(hasher)
for i, n := range nodes {
if fromLevel > 0 {
fromLevel--
continue
}
var hn node
n, hn = hasher.proofHash(n)
if hash, ok := hn.(hashNode); ok || i == 0 {
// If the node's database encoding is a hash (or is the
// root node), it becomes a proof element.
enc := nodeToBytes(n)
if !ok {
hash = hasher.hashData(enc)
}
proofDb.Put(hash, enc)
}
}
return nil
}
// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *StateTrie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
return t.trie.Prove(key, fromLevel, proofDb)
}
// VerifyProof checks merkle proofs. The given proof must contain the value for
// key in a trie with the given root hash. VerifyProof returns an error if the
// proof contains invalid trie nodes or the wrong value.
func VerifyProof(rootHash common.Hash, key []byte, proofDb ethdb.KeyValueReader) (value []byte, err error) {
key = keybytesToHex(key)
wantHash := rootHash
for i := 0; ; i++ {
buf, _ := proofDb.Get(wantHash[:])
if buf == nil {
return nil, fmt.Errorf("proof node %d (hash %064x) missing", i, wantHash)
}
n, err := decodeNode(wantHash[:], buf)
if err != nil {
return nil, fmt.Errorf("bad proof node %d: %v", i, err)
}
keyrest, cld := get(n, key, true)
switch cld := cld.(type) {
case nil:
// The trie doesn't contain the key.
return nil, nil
case hashNode:
key = keyrest
copy(wantHash[:], cld)
case valueNode:
return cld, nil
}
}
}
// proofToPath converts a merkle proof to trie node path. The main purpose of
// this function is recovering a node path from the merkle proof stream. All
// necessary nodes will be resolved and leave the remaining as hashnode.
//
// The given edge proof is allowed to be an existent or non-existent proof.
func proofToPath(rootHash common.Hash, root node, key []byte, proofDb ethdb.KeyValueReader, allowNonExistent bool) (node, []byte, error) {
// resolveNode retrieves and resolves trie node from merkle proof stream
resolveNode := func(hash common.Hash) (node, error) {
buf, _ := proofDb.Get(hash[:])
if buf == nil {
return nil, fmt.Errorf("proof node (hash %064x) missing", hash)
}
n, err := decodeNode(hash[:], buf)
if err != nil {
return nil, fmt.Errorf("bad proof node %v", err)
}
return n, err
}
// If the root node is empty, resolve it first.
// Root node must be included in the proof.
if root == nil {
n, err := resolveNode(rootHash)
if err != nil {
return nil, nil, err
}
root = n
}
var (
err error
child, parent node
keyrest []byte
valnode []byte
)
key, parent = keybytesToHex(key), root
for {
keyrest, child = get(parent, key, false)
switch cld := child.(type) {
case nil:
// The trie doesn't contain the key. It's possible
// the proof is a non-existing proof, but at least
// we can prove all resolved nodes are correct, it's
// enough for us to prove range.
if allowNonExistent {
return root, nil, nil
}
return nil, nil, errors.New("the node is not contained in trie")
case *shortNode:
key, parent = keyrest, child // Already resolved
continue
case *fullNode:
key, parent = keyrest, child // Already resolved
continue
case hashNode:
child, err = resolveNode(common.BytesToHash(cld))
if err != nil {
return nil, nil, err
}
case valueNode:
valnode = cld
}
// Link the parent and child.
switch pnode := parent.(type) {
case *shortNode:
pnode.Val = child
case *fullNode:
pnode.Children[key[0]] = child
default:
panic(fmt.Sprintf("%T: invalid node: %v", pnode, pnode))
}
if len(valnode) > 0 {
return root, valnode, nil // The whole path is resolved
}
key, parent = keyrest, child
}
}
// unsetInternal removes all internal node references(hashnode, embedded node).
// It should be called after a trie is constructed with two edge paths. Also
// the given boundary keys must be the one used to construct the edge paths.
//
// It's the key step for range proof. All visited nodes should be marked dirty
// since the node content might be modified. Besides it can happen that some
// fullnodes only have one child which is disallowed. But if the proof is valid,
// the missing children will be filled, otherwise it will be thrown anyway.
//
// Note we have the assumption here the given boundary keys are different
// and right is larger than left.
func unsetInternal(n node, left []byte, right []byte) (bool, error) {
left, right = keybytesToHex(left), keybytesToHex(right)
// Step down to the fork point. There are two scenarios can happen:
// - the fork point is a shortnode: either the key of left proof or
// right proof doesn't match with shortnode's key.
// - the fork point is a fullnode: both two edge proofs are allowed
// to point to a non-existent key.
var (
pos = 0
parent node
// fork indicator, 0 means no fork, -1 means proof is less, 1 means proof is greater
shortForkLeft, shortForkRight int
)
findFork:
for {
switch rn := (n).(type) {
case *shortNode:
rn.flags = nodeFlag{dirty: true}
// If either the key of left proof or right proof doesn't match with
// shortnode, stop here and the forkpoint is the shortnode.
if len(left)-pos < len(rn.Key) {
shortForkLeft = bytes.Compare(left[pos:], rn.Key)
} else {
shortForkLeft = bytes.Compare(left[pos:pos+len(rn.Key)], rn.Key)
}
if len(right)-pos < len(rn.Key) {
shortForkRight = bytes.Compare(right[pos:], rn.Key)
} else {
shortForkRight = bytes.Compare(right[pos:pos+len(rn.Key)], rn.Key)
}
if shortForkLeft != 0 || shortForkRight != 0 {
break findFork
}
parent = n
n, pos = rn.Val, pos+len(rn.Key)
case *fullNode:
rn.flags = nodeFlag{dirty: true}
// If either the node pointed by left proof or right proof is nil,
// stop here and the forkpoint is the fullnode.
leftnode, rightnode := rn.Children[left[pos]], rn.Children[right[pos]]
if leftnode == nil || rightnode == nil || leftnode != rightnode {
break findFork
}
parent = n
n, pos = rn.Children[left[pos]], pos+1
default:
panic(fmt.Sprintf("%T: invalid node: %v", n, n))
}
}
switch rn := n.(type) {
case *shortNode:
// There can have these five scenarios:
// - both proofs are less than the trie path => no valid range
// - both proofs are greater than the trie path => no valid range
// - left proof is less and right proof is greater => valid range, unset the shortnode entirely
// - left proof points to the shortnode, but right proof is greater
// - right proof points to the shortnode, but left proof is less
if shortForkLeft == -1 && shortForkRight == -1 {
return false, errors.New("empty range")
}
if shortForkLeft == 1 && shortForkRight == 1 {
return false, errors.New("empty range")
}
if shortForkLeft != 0 && shortForkRight != 0 {
// The fork point is root node, unset the entire trie
if parent == nil {
return true, nil
}
parent.(*fullNode).Children[left[pos-1]] = nil
return false, nil
}
// Only one proof points to non-existent key.
if shortForkRight != 0 {
if _, ok := rn.Val.(valueNode); ok {
// The fork point is root node, unset the entire trie
if parent == nil {
return true, nil
}
parent.(*fullNode).Children[left[pos-1]] = nil
return false, nil
}
return false, unset(rn, rn.Val, left[pos:], len(rn.Key), false)
}
if shortForkLeft != 0 {
if _, ok := rn.Val.(valueNode); ok {
// The fork point is root node, unset the entire trie
if parent == nil {
return true, nil
}
parent.(*fullNode).Children[right[pos-1]] = nil
return false, nil
}
return false, unset(rn, rn.Val, right[pos:], len(rn.Key), true)
}
return false, nil
case *fullNode:
// unset all internal nodes in the forkpoint
for i := left[pos] + 1; i < right[pos]; i++ {
rn.Children[i] = nil
}
if err := unset(rn, rn.Children[left[pos]], left[pos:], 1, false); err != nil {
return false, err
}
if err := unset(rn, rn.Children[right[pos]], right[pos:], 1, true); err != nil {
return false, err
}
return false, nil
default:
panic(fmt.Sprintf("%T: invalid node: %v", n, n))
}
}
// unset removes all internal node references either the left most or right most.
// It can meet these scenarios:
//
// - The given path is existent in the trie, unset the associated nodes with the
// specific direction
// - The given path is non-existent in the trie
// - the fork point is a fullnode, the corresponding child pointed by path
// is nil, return
// - the fork point is a shortnode, the shortnode is included in the range,
// keep the entire branch and return.
// - the fork point is a shortnode, the shortnode is excluded in the range,
// unset the entire branch.
func unset(parent node, child node, key []byte, pos int, removeLeft bool) error {
switch cld := child.(type) {
case *fullNode:
if removeLeft {
for i := 0; i < int(key[pos]); i++ {
cld.Children[i] = nil
}
cld.flags = nodeFlag{dirty: true}
} else {
for i := key[pos] + 1; i < 16; i++ {
cld.Children[i] = nil
}
cld.flags = nodeFlag{dirty: true}
}
return unset(cld, cld.Children[key[pos]], key, pos+1, removeLeft)
case *shortNode:
if len(key[pos:]) < len(cld.Key) || !bytes.Equal(cld.Key, key[pos:pos+len(cld.Key)]) {
// Find the fork point, it's an non-existent branch.
if removeLeft {
if bytes.Compare(cld.Key, key[pos:]) < 0 {
// The key of fork shortnode is less than the path
// (it belongs to the range), unset the entrie
// branch. The parent must be a fullnode.
fn := parent.(*fullNode)
fn.Children[key[pos-1]] = nil
}
//else {
// The key of fork shortnode is greater than the
// path(it doesn't belong to the range), keep
// it with the cached hash available.
//}
} else {
if bytes.Compare(cld.Key, key[pos:]) > 0 {
// The key of fork shortnode is greater than the
// path(it belongs to the range), unset the entrie
// branch. The parent must be a fullnode.
fn := parent.(*fullNode)
fn.Children[key[pos-1]] = nil
}
//else {
// The key of fork shortnode is less than the
// path(it doesn't belong to the range), keep
// it with the cached hash available.
//}
}
return nil
}
if _, ok := cld.Val.(valueNode); ok {
fn := parent.(*fullNode)
fn.Children[key[pos-1]] = nil
return nil
}
cld.flags = nodeFlag{dirty: true}
return unset(cld, cld.Val, key, pos+len(cld.Key), removeLeft)
case nil:
// If the node is nil, then it's a child of the fork point
// fullnode(it's a non-existent branch).
return nil
default:
panic("it shouldn't happen") // hashNode, valueNode
}
}
// hasRightElement returns the indicator whether there exists more elements
// on the right side of the given path. The given path can point to an existent
// key or a non-existent one. This function has the assumption that the whole
// path should already be resolved.
func hasRightElement(node node, key []byte) bool {
pos, key := 0, keybytesToHex(key)
for node != nil {
switch rn := node.(type) {
case *fullNode:
for i := key[pos] + 1; i < 16; i++ {
if rn.Children[i] != nil {
return true
}
}
node, pos = rn.Children[key[pos]], pos+1
case *shortNode:
if len(key)-pos < len(rn.Key) || !bytes.Equal(rn.Key, key[pos:pos+len(rn.Key)]) {
return bytes.Compare(rn.Key, key[pos:]) > 0
}
node, pos = rn.Val, pos+len(rn.Key)
case valueNode:
return false // We have resolved the whole path
default:
panic(fmt.Sprintf("%T: invalid node: %v", node, node)) // hashnode
}
}
return false
}
// VerifyRangeProof checks whether the given leaf nodes and edge proof
// can prove the given trie leaves range is matched with the specific root.
// Besides, the range should be consecutive (no gap inside) and monotonic
// increasing.
//
// Note the given proof actually contains two edge proofs. Both of them can
// be non-existent proofs. For example the first proof is for a non-existent
// key 0x03, the last proof is for a non-existent key 0x10. The given batch
// leaves are [0x04, 0x05, .. 0x09]. It's still feasible to prove the given
// batch is valid.
//
// The firstKey is paired with firstProof, not necessarily the same as keys[0]
// (unless firstProof is an existent proof). Similarly, lastKey and lastProof
// are paired.
//
// Expect the normal case, this function can also be used to verify the following
// range proofs:
//
// - All elements proof. In this case the proof can be nil, but the range should
// be all the leaves in the trie.
//
// - One element proof. In this case no matter the edge proof is a non-existent
// proof or not, we can always verify the correctness of the proof.
//
// - Zero element proof. In this case a single non-existent proof is enough to prove.
// Besides, if there are still some other leaves available on the right side, then
// an error will be returned.
//
// Except returning the error to indicate the proof is valid or not, the function will
// also return a flag to indicate whether there exists more accounts/slots in the trie.
//
// Note: This method does not verify that the proof is of minimal form. If the input
// proofs are 'bloated' with neighbour leaves or random data, aside from the 'useful'
// data, then the proof will still be accepted.
func VerifyRangeProof(rootHash common.Hash, firstKey []byte, lastKey []byte, keys [][]byte, values [][]byte, proof ethdb.KeyValueReader) (bool, error) {
if len(keys) != len(values) {
return false, fmt.Errorf("inconsistent proof data, keys: %d, values: %d", len(keys), len(values))
}
// Ensure the received batch is monotonic increasing and contains no deletions
for i := 0; i < len(keys)-1; i++ {
if bytes.Compare(keys[i], keys[i+1]) >= 0 {
return false, errors.New("range is not monotonically increasing")
}
}
for _, value := range values {
if len(value) == 0 {
return false, errors.New("range contains deletion")
}
}
// Special case, there is no edge proof at all. The given range is expected
// to be the whole leaf-set in the trie.
if proof == nil {
tr := NewStackTrie(nil)
for index, key := range keys {
tr.TryUpdate(key, values[index])
}
if have, want := tr.Hash(), rootHash; have != want {
return false, fmt.Errorf("invalid proof, want hash %x, got %x", want, have)
}
return false, nil // No more elements
}
// Special case, there is a provided edge proof but zero key/value
// pairs, ensure there are no more accounts / slots in the trie.
if len(keys) == 0 {
root, val, err := proofToPath(rootHash, nil, firstKey, proof, true)
if err != nil {
return false, err
}
if val != nil || hasRightElement(root, firstKey) {
return false, errors.New("more entries available")
}
return false, nil
}
// Special case, there is only one element and two edge keys are same.
// In this case, we can't construct two edge paths. So handle it here.
if len(keys) == 1 && bytes.Equal(firstKey, lastKey) {
root, val, err := proofToPath(rootHash, nil, firstKey, proof, false)
if err != nil {
return false, err
}
if !bytes.Equal(firstKey, keys[0]) {
return false, errors.New("correct proof but invalid key")
}
if !bytes.Equal(val, values[0]) {
return false, errors.New("correct proof but invalid data")
}
return hasRightElement(root, firstKey), nil
}
// Ok, in all other cases, we require two edge paths available.
// First check the validity of edge keys.
if bytes.Compare(firstKey, lastKey) >= 0 {
return false, errors.New("invalid edge keys")
}
// todo(rjl493456442) different length edge keys should be supported
if len(firstKey) != len(lastKey) {
return false, fmt.Errorf("inconsistent edge keys (%d != %d)", len(firstKey), len(lastKey))
}
// Convert the edge proofs to edge trie paths. Then we can
// have the same tree architecture with the original one.
// For the first edge proof, non-existent proof is allowed.
root, _, err := proofToPath(rootHash, nil, firstKey, proof, true)
if err != nil {
return false, err
}
// Pass the root node here, the second path will be merged
// with the first one. For the last edge proof, non-existent
// proof is also allowed.
root, _, err = proofToPath(rootHash, root, lastKey, proof, true)
if err != nil {
return false, err
}
// Remove all internal references. All the removed parts should
// be re-filled(or re-constructed) by the given leaves range.
empty, err := unsetInternal(root, firstKey, lastKey)
if err != nil {
return false, err
}
// Rebuild the trie with the leaf stream, the shape of trie
// should be same with the original one.
tr := &Trie{root: root, db: NewDatabase(rawdb.NewMemoryDatabase())}
if empty {
tr.root = nil
}
for index, key := range keys {
tr.TryUpdate(key, values[index])
}
if tr.Hash() != rootHash {
return false, fmt.Errorf("invalid proof, want hash %x, got %x", rootHash, tr.Hash())
}
return hasRightElement(tr.root, keys[len(keys)-1]), nil
}
// get returns the child of the given node. Return nil if the
// node with specified key doesn't exist at all.
//
// There is an additional flag `skipResolved`. If it's set then
// all resolved nodes won't be returned.
func get(tn node, key []byte, skipResolved bool) ([]byte, node) {
for {
switch n := tn.(type) {
case *shortNode:
if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
return nil, nil
}
tn = n.Val
key = key[len(n.Key):]
if !skipResolved {
return key, tn
}
case *fullNode:
tn = n.Children[key[0]]
key = key[1:]
if !skipResolved {
return key, tn
}
case hashNode:
return key, n
case nil:
return key, nil
case valueNode:
return nil, n
default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
}