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
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
|
// 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)
return error("FillableSigningProvider::AddCScript(): redeemScripts > %i bytes are invalid", MAX_SCRIPT_ELEMENT_SIZE);
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();
}
/*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.push_back(std::make_tuple(depth, leaf_ver, leaf.script));
}
}
return tuples;
}
|