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
|
// Copyright (c) 2009-2021 The Bitcoin Core developers
// Copyright (c) 2017 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <pubkey.h>
#include <hash.h>
#include <secp256k1.h>
#include <secp256k1_extrakeys.h>
#include <secp256k1_recovery.h>
#include <secp256k1_schnorrsig.h>
#include <span.h>
#include <uint256.h>
#include <algorithm>
#include <cassert>
namespace
{
/* Global secp256k1_context object used for verification. */
secp256k1_context* secp256k1_context_verify = nullptr;
} // namespace
/** This function is taken from the libsecp256k1 distribution and implements
* DER parsing for ECDSA signatures, while supporting an arbitrary subset of
* format violations.
*
* Supported violations include negative integers, excessive padding, garbage
* at the end, and overly long length descriptors. This is safe to use in
* Bitcoin because since the activation of BIP66, signatures are verified to be
* strict DER before being passed to this module, and we know it supports all
* violations present in the blockchain before that point.
*/
int ecdsa_signature_parse_der_lax(const secp256k1_context* ctx, secp256k1_ecdsa_signature* sig, const unsigned char *input, size_t inputlen) {
size_t rpos, rlen, spos, slen;
size_t pos = 0;
size_t lenbyte;
unsigned char tmpsig[64] = {0};
int overflow = 0;
/* Hack to initialize sig with a correctly-parsed but invalid signature. */
secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
/* Sequence tag byte */
if (pos == inputlen || input[pos] != 0x30) {
return 0;
}
pos++;
/* Sequence length bytes */
if (pos == inputlen) {
return 0;
}
lenbyte = input[pos++];
if (lenbyte & 0x80) {
lenbyte -= 0x80;
if (lenbyte > inputlen - pos) {
return 0;
}
pos += lenbyte;
}
/* Integer tag byte for R */
if (pos == inputlen || input[pos] != 0x02) {
return 0;
}
pos++;
/* Integer length for R */
if (pos == inputlen) {
return 0;
}
lenbyte = input[pos++];
if (lenbyte & 0x80) {
lenbyte -= 0x80;
if (lenbyte > inputlen - pos) {
return 0;
}
while (lenbyte > 0 && input[pos] == 0) {
pos++;
lenbyte--;
}
static_assert(sizeof(size_t) >= 4, "size_t too small");
if (lenbyte >= 4) {
return 0;
}
rlen = 0;
while (lenbyte > 0) {
rlen = (rlen << 8) + input[pos];
pos++;
lenbyte--;
}
} else {
rlen = lenbyte;
}
if (rlen > inputlen - pos) {
return 0;
}
rpos = pos;
pos += rlen;
/* Integer tag byte for S */
if (pos == inputlen || input[pos] != 0x02) {
return 0;
}
pos++;
/* Integer length for S */
if (pos == inputlen) {
return 0;
}
lenbyte = input[pos++];
if (lenbyte & 0x80) {
lenbyte -= 0x80;
if (lenbyte > inputlen - pos) {
return 0;
}
while (lenbyte > 0 && input[pos] == 0) {
pos++;
lenbyte--;
}
static_assert(sizeof(size_t) >= 4, "size_t too small");
if (lenbyte >= 4) {
return 0;
}
slen = 0;
while (lenbyte > 0) {
slen = (slen << 8) + input[pos];
pos++;
lenbyte--;
}
} else {
slen = lenbyte;
}
if (slen > inputlen - pos) {
return 0;
}
spos = pos;
/* Ignore leading zeroes in R */
while (rlen > 0 && input[rpos] == 0) {
rlen--;
rpos++;
}
/* Copy R value */
if (rlen > 32) {
overflow = 1;
} else {
memcpy(tmpsig + 32 - rlen, input + rpos, rlen);
}
/* Ignore leading zeroes in S */
while (slen > 0 && input[spos] == 0) {
slen--;
spos++;
}
/* Copy S value */
if (slen > 32) {
overflow = 1;
} else {
memcpy(tmpsig + 64 - slen, input + spos, slen);
}
if (!overflow) {
overflow = !secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
}
if (overflow) {
/* Overwrite the result again with a correctly-parsed but invalid
signature if parsing failed. */
memset(tmpsig, 0, 64);
secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
}
return 1;
}
XOnlyPubKey::XOnlyPubKey(Span<const unsigned char> bytes)
{
assert(bytes.size() == 32);
std::copy(bytes.begin(), bytes.end(), m_keydata.begin());
}
std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
{
std::vector<CKeyID> out;
// For now, use the old full pubkey-based key derivation logic. As it is indexed by
// Hash160(full pubkey), we need to return both a version prefixed with 0x02, and one
// with 0x03.
unsigned char b[33] = {0x02};
std::copy(m_keydata.begin(), m_keydata.end(), b + 1);
CPubKey fullpubkey;
fullpubkey.Set(b, b + 33);
out.push_back(fullpubkey.GetID());
b[0] = 0x03;
fullpubkey.Set(b, b + 33);
out.push_back(fullpubkey.GetID());
return out;
}
bool XOnlyPubKey::IsFullyValid() const
{
secp256k1_xonly_pubkey pubkey;
return secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &pubkey, m_keydata.data());
}
bool XOnlyPubKey::VerifySchnorr(const uint256& msg, Span<const unsigned char> sigbytes) const
{
assert(sigbytes.size() == 64);
secp256k1_xonly_pubkey pubkey;
if (!secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &pubkey, m_keydata.data())) return false;
return secp256k1_schnorrsig_verify(secp256k1_context_verify, sigbytes.data(), msg.begin(), 32, &pubkey);
}
static const CHashWriter HASHER_TAPTWEAK = TaggedHash("TapTweak");
uint256 XOnlyPubKey::ComputeTapTweakHash(const uint256* merkle_root) const
{
if (merkle_root == nullptr) {
// We have no scripts. The actual tweak does not matter, but follow BIP341 here to
// allow for reproducible tweaking.
return (CHashWriter(HASHER_TAPTWEAK) << m_keydata).GetSHA256();
} else {
return (CHashWriter(HASHER_TAPTWEAK) << m_keydata << *merkle_root).GetSHA256();
}
}
bool XOnlyPubKey::CheckTapTweak(const XOnlyPubKey& internal, const uint256& merkle_root, bool parity) const
{
secp256k1_xonly_pubkey internal_key;
if (!secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &internal_key, internal.data())) return false;
uint256 tweak = internal.ComputeTapTweakHash(&merkle_root);
return secp256k1_xonly_pubkey_tweak_add_check(secp256k1_context_verify, m_keydata.begin(), parity, &internal_key, tweak.begin());
}
std::optional<std::pair<XOnlyPubKey, bool>> XOnlyPubKey::CreateTapTweak(const uint256* merkle_root) const
{
secp256k1_xonly_pubkey base_point;
if (!secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &base_point, data())) return std::nullopt;
secp256k1_pubkey out;
uint256 tweak = ComputeTapTweakHash(merkle_root);
if (!secp256k1_xonly_pubkey_tweak_add(secp256k1_context_verify, &out, &base_point, tweak.data())) return std::nullopt;
int parity = -1;
std::pair<XOnlyPubKey, bool> ret;
secp256k1_xonly_pubkey out_xonly;
if (!secp256k1_xonly_pubkey_from_pubkey(secp256k1_context_verify, &out_xonly, &parity, &out)) return std::nullopt;
secp256k1_xonly_pubkey_serialize(secp256k1_context_verify, ret.first.begin(), &out_xonly);
assert(parity == 0 || parity == 1);
ret.second = parity;
return ret;
}
bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
if (!IsValid())
return false;
secp256k1_pubkey pubkey;
secp256k1_ecdsa_signature sig;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
return false;
}
if (!ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig, vchSig.data(), vchSig.size())) {
return false;
}
/* libsecp256k1's ECDSA verification requires lower-S signatures, which have
* not historically been enforced in Bitcoin, so normalize them first. */
secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, &sig, &sig);
return secp256k1_ecdsa_verify(secp256k1_context_verify, &sig, hash.begin(), &pubkey);
}
bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
if (vchSig.size() != COMPACT_SIGNATURE_SIZE)
return false;
int recid = (vchSig[0] - 27) & 3;
bool fComp = ((vchSig[0] - 27) & 4) != 0;
secp256k1_pubkey pubkey;
secp256k1_ecdsa_recoverable_signature sig;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_verify, &sig, &vchSig[1], recid)) {
return false;
}
if (!secp256k1_ecdsa_recover(secp256k1_context_verify, &pubkey, &sig, hash.begin())) {
return false;
}
unsigned char pub[SIZE];
size_t publen = SIZE;
secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, fComp ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
Set(pub, pub + publen);
return true;
}
bool CPubKey::IsFullyValid() const {
if (!IsValid())
return false;
secp256k1_pubkey pubkey;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
return secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size());
}
bool CPubKey::Decompress() {
if (!IsValid())
return false;
secp256k1_pubkey pubkey;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
return false;
}
unsigned char pub[SIZE];
size_t publen = SIZE;
secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
Set(pub, pub + publen);
return true;
}
bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
assert(IsValid());
assert((nChild >> 31) == 0);
assert(size() == COMPRESSED_SIZE);
unsigned char out[64];
BIP32Hash(cc, nChild, *begin(), begin()+1, out);
memcpy(ccChild.begin(), out+32, 32);
secp256k1_pubkey pubkey;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, vch, size())) {
return false;
}
if (!secp256k1_ec_pubkey_tweak_add(secp256k1_context_verify, &pubkey, out)) {
return false;
}
unsigned char pub[COMPRESSED_SIZE];
size_t publen = COMPRESSED_SIZE;
secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_COMPRESSED);
pubkeyChild.Set(pub, pub + publen);
return true;
}
void CExtPubKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
code[0] = nDepth;
memcpy(code+1, vchFingerprint, 4);
WriteBE32(code+5, nChild);
memcpy(code+9, chaincode.begin(), 32);
assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
memcpy(code+41, pubkey.begin(), CPubKey::COMPRESSED_SIZE);
}
void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
nDepth = code[0];
memcpy(vchFingerprint, code+1, 4);
nChild = ReadBE32(code+5);
memcpy(chaincode.begin(), code+9, 32);
pubkey.Set(code+41, code+BIP32_EXTKEY_SIZE);
if ((nDepth == 0 && (nChild != 0 || ReadLE32(vchFingerprint) != 0)) || !pubkey.IsFullyValid()) pubkey = CPubKey();
}
void CExtPubKey::EncodeWithVersion(unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE]) const
{
memcpy(code, version, 4);
Encode(&code[4]);
}
void CExtPubKey::DecodeWithVersion(const unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE])
{
memcpy(version, code, 4);
Decode(&code[4]);
}
bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
if (nDepth == std::numeric_limits<unsigned char>::max()) return false;
out.nDepth = nDepth + 1;
CKeyID id = pubkey.GetID();
memcpy(out.vchFingerprint, &id, 4);
out.nChild = _nChild;
return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
}
/* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
secp256k1_ecdsa_signature sig;
assert(secp256k1_context_verify && "secp256k1_context_verify must be initialized to use CPubKey.");
if (!ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig, vchSig.data(), vchSig.size())) {
return false;
}
return (!secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, nullptr, &sig));
}
/* static */ int ECCVerifyHandle::refcount = 0;
ECCVerifyHandle::ECCVerifyHandle()
{
if (refcount == 0) {
assert(secp256k1_context_verify == nullptr);
secp256k1_context_verify = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
assert(secp256k1_context_verify != nullptr);
}
refcount++;
}
ECCVerifyHandle::~ECCVerifyHandle()
{
refcount--;
if (refcount == 0) {
assert(secp256k1_context_verify != nullptr);
secp256k1_context_destroy(secp256k1_context_verify);
secp256k1_context_verify = nullptr;
}
}
const secp256k1_context* GetVerifyContext() {
return secp256k1_context_verify;
}
|