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bitcoin/src/script/signingprovider.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <script/keyorigin.h>
#include <script/interpreter.h>
#include <script/signingprovider.h>
#include <logging.h>
const SigningProvider& DUMMY_SIGNING_PROVIDER = SigningProvider();
template<typename M, typename K, typename V>
bool LookupHelper(const M& map, const K& key, V& value)
{
auto it = map.find(key);
if (it != map.end()) {
value = it->second;
return true;
}
return false;
}
bool HidingSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const
{
return m_provider->GetCScript(scriptid, script);
}
bool HidingSigningProvider::GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const
{
return m_provider->GetPubKey(keyid, pubkey);
}
bool HidingSigningProvider::GetKey(const CKeyID& keyid, CKey& key) const
{
if (m_hide_secret) return false;
return m_provider->GetKey(keyid, key);
}
bool HidingSigningProvider::GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const
{
if (m_hide_origin) return false;
return m_provider->GetKeyOrigin(keyid, info);
}
bool HidingSigningProvider::GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const
{
return m_provider->GetTaprootSpendData(output_key, spenddata);
}
bool HidingSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const
{
return m_provider->GetTaprootBuilder(output_key, builder);
}
bool FlatSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const { return LookupHelper(scripts, scriptid, script); }
bool FlatSigningProvider::GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const { return LookupHelper(pubkeys, keyid, pubkey); }
bool FlatSigningProvider::GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const
{
std::pair<CPubKey, KeyOriginInfo> out;
bool ret = LookupHelper(origins, keyid, out);
if (ret) info = std::move(out.second);
return ret;
}
bool FlatSigningProvider::GetKey(const CKeyID& keyid, CKey& key) const { return LookupHelper(keys, keyid, key); }
bool FlatSigningProvider::GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const
{
TaprootBuilder builder;
if (LookupHelper(tr_trees, output_key, builder)) {
spenddata = builder.GetSpendData();
return true;
}
return false;
}
bool FlatSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const
{
return LookupHelper(tr_trees, output_key, builder);
}
FlatSigningProvider& FlatSigningProvider::Merge(FlatSigningProvider&& b)
{
scripts.merge(b.scripts);
pubkeys.merge(b.pubkeys);
keys.merge(b.keys);
origins.merge(b.origins);
tr_trees.merge(b.tr_trees);
return *this;
}
void FillableSigningProvider::ImplicitlyLearnRelatedKeyScripts(const CPubKey& pubkey)
{
AssertLockHeld(cs_KeyStore);
CKeyID key_id = pubkey.GetID();
// This adds the redeemscripts necessary to detect P2WPKH and P2SH-P2WPKH
// outputs. Technically P2WPKH outputs don't have a redeemscript to be
// spent. However, our current IsMine logic requires the corresponding
// P2SH-P2WPKH redeemscript to be present in the wallet in order to accept
// payment even to P2WPKH outputs.
// Also note that having superfluous scripts in the keystore never hurts.
// They're only used to guide recursion in signing and IsMine logic - if
// a script is present but we can't do anything with it, it has no effect.
// "Implicitly" refers to fact that scripts are derived automatically from
// existing keys, and are present in memory, even without being explicitly
// loaded (e.g. from a file).
if (pubkey.IsCompressed()) {
CScript script = GetScriptForDestination(WitnessV0KeyHash(key_id));
// This does not use AddCScript, as it may be overridden.
CScriptID id(script);
mapScripts[id] = std::move(script);
}
}
bool FillableSigningProvider::GetPubKey(const CKeyID &address, CPubKey &vchPubKeyOut) const
{
CKey key;
if (!GetKey(address, key)) {
return false;
}
vchPubKeyOut = key.GetPubKey();
return true;
}
bool FillableSigningProvider::AddKeyPubKey(const CKey& key, const CPubKey &pubkey)
{
LOCK(cs_KeyStore);
mapKeys[pubkey.GetID()] = key;
ImplicitlyLearnRelatedKeyScripts(pubkey);
return true;
}
bool FillableSigningProvider::HaveKey(const CKeyID &address) const
{
LOCK(cs_KeyStore);
return mapKeys.count(address) > 0;
}
std::set<CKeyID> FillableSigningProvider::GetKeys() const
{
LOCK(cs_KeyStore);
std::set<CKeyID> set_address;
for (const auto& mi : mapKeys) {
set_address.insert(mi.first);
}
return set_address;
}
bool FillableSigningProvider::GetKey(const CKeyID &address, CKey &keyOut) const
{
LOCK(cs_KeyStore);
KeyMap::const_iterator mi = mapKeys.find(address);
if (mi != mapKeys.end()) {
keyOut = mi->second;
return true;
}
return false;
}
bool FillableSigningProvider::AddCScript(const CScript& redeemScript)
{
if (redeemScript.size() > MAX_SCRIPT_ELEMENT_SIZE) {
LogError("FillableSigningProvider::AddCScript(): redeemScripts > %i bytes are invalid\n", MAX_SCRIPT_ELEMENT_SIZE);
return false;
}
LOCK(cs_KeyStore);
mapScripts[CScriptID(redeemScript)] = redeemScript;
return true;
}
bool FillableSigningProvider::HaveCScript(const CScriptID& hash) const
{
LOCK(cs_KeyStore);
return mapScripts.count(hash) > 0;
}
std::set<CScriptID> FillableSigningProvider::GetCScripts() const
{
LOCK(cs_KeyStore);
std::set<CScriptID> set_script;
for (const auto& mi : mapScripts) {
set_script.insert(mi.first);
}
return set_script;
}
bool FillableSigningProvider::GetCScript(const CScriptID &hash, CScript& redeemScriptOut) const
{
LOCK(cs_KeyStore);
ScriptMap::const_iterator mi = mapScripts.find(hash);
if (mi != mapScripts.end())
{
redeemScriptOut = (*mi).second;
return true;
}
return false;
}
CKeyID GetKeyForDestination(const SigningProvider& store, const CTxDestination& dest)
{
// Only supports destinations which map to single public keys:
// P2PKH, P2WPKH, P2SH-P2WPKH, P2TR
if (auto id = std::get_if<PKHash>(&dest)) {
return ToKeyID(*id);
}
if (auto witness_id = std::get_if<WitnessV0KeyHash>(&dest)) {
return ToKeyID(*witness_id);
}
if (auto script_hash = std::get_if<ScriptHash>(&dest)) {
CScript script;
CScriptID script_id = ToScriptID(*script_hash);
CTxDestination inner_dest;
if (store.GetCScript(script_id, script) && ExtractDestination(script, inner_dest)) {
if (auto inner_witness_id = std::get_if<WitnessV0KeyHash>(&inner_dest)) {
return ToKeyID(*inner_witness_id);
}
}
}
if (auto output_key = std::get_if<WitnessV1Taproot>(&dest)) {
TaprootSpendData spenddata;
CPubKey pub;
if (store.GetTaprootSpendData(*output_key, spenddata)
&& !spenddata.internal_key.IsNull()
&& spenddata.merkle_root.IsNull()
&& store.GetPubKeyByXOnly(spenddata.internal_key, pub)) {
return pub.GetID();
}
}
return CKeyID();
}
void MultiSigningProvider::AddProvider(std::unique_ptr<SigningProvider> provider)
{
m_providers.push_back(std::move(provider));
}
bool MultiSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const
{
for (const auto& provider: m_providers) {
if (provider->GetCScript(scriptid, script)) return true;
}
return false;
}
bool MultiSigningProvider::GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const
{
for (const auto& provider: m_providers) {
if (provider->GetPubKey(keyid, pubkey)) return true;
}
return false;
}
bool MultiSigningProvider::GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const
{
for (const auto& provider: m_providers) {
if (provider->GetKeyOrigin(keyid, info)) return true;
}
return false;
}
bool MultiSigningProvider::GetKey(const CKeyID& keyid, CKey& key) const
{
for (const auto& provider: m_providers) {
if (provider->GetKey(keyid, key)) return true;
}
return false;
}
bool MultiSigningProvider::GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const
{
for (const auto& provider: m_providers) {
if (provider->GetTaprootSpendData(output_key, spenddata)) return true;
}
return false;
}
bool MultiSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const
{
for (const auto& provider: m_providers) {
if (provider->GetTaprootBuilder(output_key, builder)) return true;
}
return false;
}
/*static*/ TaprootBuilder::NodeInfo TaprootBuilder::Combine(NodeInfo&& a, NodeInfo&& b)
{
NodeInfo ret;
/* Iterate over all tracked leaves in a, add b's hash to their Merkle branch, and move them to ret. */
for (auto& leaf : a.leaves) {
leaf.merkle_branch.push_back(b.hash);
ret.leaves.emplace_back(std::move(leaf));
}
/* Iterate over all tracked leaves in b, add a's hash to their Merkle branch, and move them to ret. */
for (auto& leaf : b.leaves) {
leaf.merkle_branch.push_back(a.hash);
ret.leaves.emplace_back(std::move(leaf));
}
ret.hash = ComputeTapbranchHash(a.hash, b.hash);
return ret;
}
void TaprootSpendData::Merge(TaprootSpendData other)
{
// TODO: figure out how to better deal with conflicting information
// being merged.
if (internal_key.IsNull() && !other.internal_key.IsNull()) {
internal_key = other.internal_key;
}
if (merkle_root.IsNull() && !other.merkle_root.IsNull()) {
merkle_root = other.merkle_root;
}
for (auto& [key, control_blocks] : other.scripts) {
scripts[key].merge(std::move(control_blocks));
}
}
void TaprootBuilder::Insert(TaprootBuilder::NodeInfo&& node, int depth)
{
assert(depth >= 0 && (size_t)depth <= TAPROOT_CONTROL_MAX_NODE_COUNT);
/* We cannot insert a leaf at a lower depth while a deeper branch is unfinished. Doing
* so would mean the Add() invocations do not correspond to a DFS traversal of a
* binary tree. */
if ((size_t)depth + 1 < m_branch.size()) {
m_valid = false;
return;
}
/* As long as an entry in the branch exists at the specified depth, combine it and propagate up.
* The 'node' variable is overwritten here with the newly combined node. */
while (m_valid && m_branch.size() > (size_t)depth && m_branch[depth].has_value()) {
node = Combine(std::move(node), std::move(*m_branch[depth]));
m_branch.pop_back();
if (depth == 0) m_valid = false; /* Can't propagate further up than the root */
--depth;
}
if (m_valid) {
/* Make sure the branch is big enough to place the new node. */
if (m_branch.size() <= (size_t)depth) m_branch.resize((size_t)depth + 1);
assert(!m_branch[depth].has_value());
m_branch[depth] = std::move(node);
}
}
/*static*/ bool TaprootBuilder::ValidDepths(const std::vector<int>& depths)
{
std::vector<bool> branch;
for (int depth : depths) {
// This inner loop corresponds to effectively the same logic on branch
// as what Insert() performs on the m_branch variable. Instead of
// storing a NodeInfo object, just remember whether or not there is one
// at that depth.
if (depth < 0 || (size_t)depth > TAPROOT_CONTROL_MAX_NODE_COUNT) return false;
if ((size_t)depth + 1 < branch.size()) return false;
while (branch.size() > (size_t)depth && branch[depth]) {
branch.pop_back();
if (depth == 0) return false;
--depth;
}
if (branch.size() <= (size_t)depth) branch.resize((size_t)depth + 1);
assert(!branch[depth]);
branch[depth] = true;
}
// And this check corresponds to the IsComplete() check on m_branch.
return branch.size() == 0 || (branch.size() == 1 && branch[0]);
}
TaprootBuilder& TaprootBuilder::Add(int depth, Span<const unsigned char> script, int leaf_version, bool track)
{
assert((leaf_version & ~TAPROOT_LEAF_MASK) == 0);
if (!IsValid()) return *this;
/* Construct NodeInfo object with leaf hash and (if track is true) also leaf information. */
NodeInfo node;
node.hash = ComputeTapleafHash(leaf_version, script);
if (track) node.leaves.emplace_back(LeafInfo{std::vector<unsigned char>(script.begin(), script.end()), leaf_version, {}});
/* Insert into the branch. */
Insert(std::move(node), depth);
return *this;
}
TaprootBuilder& TaprootBuilder::AddOmitted(int depth, const uint256& hash)
{
if (!IsValid()) return *this;
/* Construct NodeInfo object with the hash directly, and insert it into the branch. */
NodeInfo node;
node.hash = hash;
Insert(std::move(node), depth);
return *this;
}
TaprootBuilder& TaprootBuilder::Finalize(const XOnlyPubKey& internal_key)
{
/* Can only call this function when IsComplete() is true. */
assert(IsComplete());
m_internal_key = internal_key;
auto ret = m_internal_key.CreateTapTweak(m_branch.size() == 0 ? nullptr : &m_branch[0]->hash);
assert(ret.has_value());
std::tie(m_output_key, m_parity) = *ret;
return *this;
}
WitnessV1Taproot TaprootBuilder::GetOutput() { return WitnessV1Taproot{m_output_key}; }
TaprootSpendData TaprootBuilder::GetSpendData() const
{
assert(IsComplete());
assert(m_output_key.IsFullyValid());
TaprootSpendData spd;
spd.merkle_root = m_branch.size() == 0 ? uint256() : m_branch[0]->hash;
spd.internal_key = m_internal_key;
if (m_branch.size()) {
// If any script paths exist, they have been combined into the root m_branch[0]
// by now. Compute the control block for each of its tracked leaves, and put them in
// spd.scripts.
for (const auto& leaf : m_branch[0]->leaves) {
std::vector<unsigned char> control_block;
control_block.resize(TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * leaf.merkle_branch.size());
control_block[0] = leaf.leaf_version | (m_parity ? 1 : 0);
std::copy(m_internal_key.begin(), m_internal_key.end(), control_block.begin() + 1);
if (leaf.merkle_branch.size()) {
std::copy(leaf.merkle_branch[0].begin(),
leaf.merkle_branch[0].begin() + TAPROOT_CONTROL_NODE_SIZE * leaf.merkle_branch.size(),
control_block.begin() + TAPROOT_CONTROL_BASE_SIZE);
}
spd.scripts[{leaf.script, leaf.leaf_version}].insert(std::move(control_block));
}
}
return spd;
}
std::optional<std::vector<std::tuple<int, std::vector<unsigned char>, int>>> InferTaprootTree(const TaprootSpendData& spenddata, const XOnlyPubKey& output)
{
// Verify that the output matches the assumed Merkle root and internal key.
auto tweak = spenddata.internal_key.CreateTapTweak(spenddata.merkle_root.IsNull() ? nullptr : &spenddata.merkle_root);
if (!tweak || tweak->first != output) return std::nullopt;
// If the Merkle root is 0, the tree is empty, and we're done.
std::vector<std::tuple<int, std::vector<unsigned char>, int>> ret;
if (spenddata.merkle_root.IsNull()) return ret;
/** Data structure to represent the nodes of the tree we're going to build. */
struct TreeNode {
/** Hash of this node, if known; 0 otherwise. */
uint256 hash;
/** The left and right subtrees (note that their order is irrelevant). */
std::unique_ptr<TreeNode> sub[2];
/** If this is known to be a leaf node, a pointer to the (script, leaf_ver) pair.
* nullptr otherwise. */
const std::pair<std::vector<unsigned char>, int>* leaf = nullptr;
/** Whether or not this node has been explored (is known to be a leaf, or known to have children). */
bool explored = false;
/** Whether or not this node is an inner node (unknown until explored = true). */
bool inner;
/** Whether or not we have produced output for this subtree. */
bool done = false;
};
// Build tree from the provided branches.
TreeNode root;
root.hash = spenddata.merkle_root;
for (const auto& [key, control_blocks] : spenddata.scripts) {
const auto& [script, leaf_ver] = key;
for (const auto& control : control_blocks) {
// Skip script records with nonsensical leaf version.
if (leaf_ver < 0 || leaf_ver >= 0x100 || leaf_ver & 1) continue;
// Skip script records with invalid control block sizes.
if (control.size() < TAPROOT_CONTROL_BASE_SIZE || control.size() > TAPROOT_CONTROL_MAX_SIZE ||
((control.size() - TAPROOT_CONTROL_BASE_SIZE) % TAPROOT_CONTROL_NODE_SIZE) != 0) continue;
// Skip script records that don't match the control block.
if ((control[0] & TAPROOT_LEAF_MASK) != leaf_ver) continue;
// Skip script records that don't match the provided Merkle root.
const uint256 leaf_hash = ComputeTapleafHash(leaf_ver, script);
const uint256 merkle_root = ComputeTaprootMerkleRoot(control, leaf_hash);
if (merkle_root != spenddata.merkle_root) continue;
TreeNode* node = &root;
size_t levels = (control.size() - TAPROOT_CONTROL_BASE_SIZE) / TAPROOT_CONTROL_NODE_SIZE;
for (size_t depth = 0; depth < levels; ++depth) {
// Can't descend into a node which we already know is a leaf.
if (node->explored && !node->inner) return std::nullopt;
// Extract partner hash from Merkle branch in control block.
uint256 hash;
std::copy(control.begin() + TAPROOT_CONTROL_BASE_SIZE + (levels - 1 - depth) * TAPROOT_CONTROL_NODE_SIZE,
control.begin() + TAPROOT_CONTROL_BASE_SIZE + (levels - depth) * TAPROOT_CONTROL_NODE_SIZE,
hash.begin());
if (node->sub[0]) {
// Descend into the existing left or right branch.
bool desc = false;
for (int i = 0; i < 2; ++i) {
if (node->sub[i]->hash == hash || (node->sub[i]->hash.IsNull() && node->sub[1-i]->hash != hash)) {
node->sub[i]->hash = hash;
node = &*node->sub[1-i];
desc = true;
break;
}
}
if (!desc) return std::nullopt; // This probably requires a hash collision to hit.
} else {
// We're in an unexplored node. Create subtrees and descend.
node->explored = true;
node->inner = true;
node->sub[0] = std::make_unique<TreeNode>();
node->sub[1] = std::make_unique<TreeNode>();
node->sub[1]->hash = hash;
node = &*node->sub[0];
}
}
// Cannot turn a known inner node into a leaf.
if (node->sub[0]) return std::nullopt;
node->explored = true;
node->inner = false;
node->leaf = &key;
node->hash = leaf_hash;
}
}
// Recursive processing to turn the tree into flattened output. Use an explicit stack here to avoid
// overflowing the call stack (the tree may be 128 levels deep).
std::vector<TreeNode*> stack{&root};
while (!stack.empty()) {
TreeNode& node = *stack.back();
if (!node.explored) {
// Unexplored node, which means the tree is incomplete.
return std::nullopt;
} else if (!node.inner) {
// Leaf node; produce output.
ret.emplace_back(stack.size() - 1, node.leaf->first, node.leaf->second);
node.done = true;
stack.pop_back();
} else if (node.sub[0]->done && !node.sub[1]->done && !node.sub[1]->explored && !node.sub[1]->hash.IsNull() &&
ComputeTapbranchHash(node.sub[1]->hash, node.sub[1]->hash) == node.hash) {
// Whenever there are nodes with two identical subtrees under it, we run into a problem:
// the control blocks for the leaves underneath those will be identical as well, and thus
// they will all be matched to the same path in the tree. The result is that at the location
// where the duplicate occurred, the left child will contain a normal tree that can be explored
// and processed, but the right one will remain unexplored.
//
// This situation can be detected, by encountering an inner node with unexplored right subtree
// with known hash, and H_TapBranch(hash, hash) is equal to the parent node (this node)'s hash.
//
// To deal with this, simply process the left tree a second time (set its done flag to false;
// noting that the done flag of its children have already been set to false after processing
// those). To avoid ending up in an infinite loop, set the done flag of the right (unexplored)
// subtree to true.
node.sub[0]->done = false;
node.sub[1]->done = true;
} else if (node.sub[0]->done && node.sub[1]->done) {
// An internal node which we're finished with.
node.sub[0]->done = false;
node.sub[1]->done = false;
node.done = true;
stack.pop_back();
} else if (!node.sub[0]->done) {
// An internal node whose left branch hasn't been processed yet. Do so first.
stack.push_back(&*node.sub[0]);
} else if (!node.sub[1]->done) {
// An internal node whose right branch hasn't been processed yet. Do so first.
stack.push_back(&*node.sub[1]);
}
}
return ret;
}
std::vector<std::tuple<uint8_t, uint8_t, std::vector<unsigned char>>> TaprootBuilder::GetTreeTuples() const
{
assert(IsComplete());
std::vector<std::tuple<uint8_t, uint8_t, std::vector<unsigned char>>> tuples;
if (m_branch.size()) {
const auto& leaves = m_branch[0]->leaves;
for (const auto& leaf : leaves) {
assert(leaf.merkle_branch.size() <= TAPROOT_CONTROL_MAX_NODE_COUNT);
uint8_t depth = (uint8_t)leaf.merkle_branch.size();
uint8_t leaf_ver = (uint8_t)leaf.leaf_version;
tuples.emplace_back(depth, leaf_ver, leaf.script);
}
}
return tuples;
}
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