Line data Source code
1 : // Copyright (c) 2009-2022 The Bitcoin Core developers
2 : // Copyright (c) 2017 The Zcash developers
3 : // Distributed under the MIT software license, see the accompanying
4 : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5 :
6 : #include <pubkey.h>
7 :
8 : #include <hash.h>
9 : #include <secp256k1.h>
10 : #include <secp256k1_ellswift.h>
11 : #include <secp256k1_extrakeys.h>
12 : #include <secp256k1_recovery.h>
13 : #include <secp256k1_schnorrsig.h>
14 : #include <span.h>
15 : #include <uint256.h>
16 :
17 : #include <algorithm>
18 : #include <cassert>
19 :
20 : namespace {
21 :
22 : struct Secp256k1SelfTester
23 : {
24 2 : Secp256k1SelfTester() {
25 : /* Run libsecp256k1 self-test before using the secp256k1_context_static. */
26 2 : secp256k1_selftest();
27 2 : }
28 2 : } SECP256K1_SELFTESTER;
29 :
30 : } // namespace
31 :
32 : /** This function is taken from the libsecp256k1 distribution and implements
33 : * DER parsing for ECDSA signatures, while supporting an arbitrary subset of
34 : * format violations.
35 : *
36 : * Supported violations include negative integers, excessive padding, garbage
37 : * at the end, and overly long length descriptors. This is safe to use in
38 : * Bitcoin because since the activation of BIP66, signatures are verified to be
39 : * strict DER before being passed to this module, and we know it supports all
40 : * violations present in the blockchain before that point.
41 : */
42 0 : int ecdsa_signature_parse_der_lax(secp256k1_ecdsa_signature* sig, const unsigned char *input, size_t inputlen) {
43 : size_t rpos, rlen, spos, slen;
44 0 : size_t pos = 0;
45 : size_t lenbyte;
46 0 : unsigned char tmpsig[64] = {0};
47 0 : int overflow = 0;
48 :
49 : /* Hack to initialize sig with a correctly-parsed but invalid signature. */
50 0 : secp256k1_ecdsa_signature_parse_compact(secp256k1_context_static, sig, tmpsig);
51 :
52 : /* Sequence tag byte */
53 0 : if (pos == inputlen || input[pos] != 0x30) {
54 0 : return 0;
55 : }
56 0 : pos++;
57 :
58 : /* Sequence length bytes */
59 0 : if (pos == inputlen) {
60 0 : return 0;
61 : }
62 0 : lenbyte = input[pos++];
63 0 : if (lenbyte & 0x80) {
64 0 : lenbyte -= 0x80;
65 0 : if (lenbyte > inputlen - pos) {
66 0 : return 0;
67 : }
68 0 : pos += lenbyte;
69 0 : }
70 :
71 : /* Integer tag byte for R */
72 0 : if (pos == inputlen || input[pos] != 0x02) {
73 0 : return 0;
74 : }
75 0 : pos++;
76 :
77 : /* Integer length for R */
78 0 : if (pos == inputlen) {
79 0 : return 0;
80 : }
81 0 : lenbyte = input[pos++];
82 0 : if (lenbyte & 0x80) {
83 0 : lenbyte -= 0x80;
84 0 : if (lenbyte > inputlen - pos) {
85 0 : return 0;
86 : }
87 0 : while (lenbyte > 0 && input[pos] == 0) {
88 0 : pos++;
89 0 : lenbyte--;
90 : }
91 : static_assert(sizeof(size_t) >= 4, "size_t too small");
92 0 : if (lenbyte >= 4) {
93 0 : return 0;
94 : }
95 0 : rlen = 0;
96 0 : while (lenbyte > 0) {
97 0 : rlen = (rlen << 8) + input[pos];
98 0 : pos++;
99 0 : lenbyte--;
100 : }
101 0 : } else {
102 0 : rlen = lenbyte;
103 : }
104 0 : if (rlen > inputlen - pos) {
105 0 : return 0;
106 : }
107 0 : rpos = pos;
108 0 : pos += rlen;
109 :
110 : /* Integer tag byte for S */
111 0 : if (pos == inputlen || input[pos] != 0x02) {
112 0 : return 0;
113 : }
114 0 : pos++;
115 :
116 : /* Integer length for S */
117 0 : if (pos == inputlen) {
118 0 : return 0;
119 : }
120 0 : lenbyte = input[pos++];
121 0 : if (lenbyte & 0x80) {
122 0 : lenbyte -= 0x80;
123 0 : if (lenbyte > inputlen - pos) {
124 0 : return 0;
125 : }
126 0 : while (lenbyte > 0 && input[pos] == 0) {
127 0 : pos++;
128 0 : lenbyte--;
129 : }
130 : static_assert(sizeof(size_t) >= 4, "size_t too small");
131 0 : if (lenbyte >= 4) {
132 0 : return 0;
133 : }
134 0 : slen = 0;
135 0 : while (lenbyte > 0) {
136 0 : slen = (slen << 8) + input[pos];
137 0 : pos++;
138 0 : lenbyte--;
139 : }
140 0 : } else {
141 0 : slen = lenbyte;
142 : }
143 0 : if (slen > inputlen - pos) {
144 0 : return 0;
145 : }
146 0 : spos = pos;
147 :
148 : /* Ignore leading zeroes in R */
149 0 : while (rlen > 0 && input[rpos] == 0) {
150 0 : rlen--;
151 0 : rpos++;
152 : }
153 : /* Copy R value */
154 0 : if (rlen > 32) {
155 0 : overflow = 1;
156 0 : } else {
157 0 : memcpy(tmpsig + 32 - rlen, input + rpos, rlen);
158 : }
159 :
160 : /* Ignore leading zeroes in S */
161 0 : while (slen > 0 && input[spos] == 0) {
162 0 : slen--;
163 0 : spos++;
164 : }
165 : /* Copy S value */
166 0 : if (slen > 32) {
167 0 : overflow = 1;
168 0 : } else {
169 0 : memcpy(tmpsig + 64 - slen, input + spos, slen);
170 : }
171 :
172 0 : if (!overflow) {
173 0 : overflow = !secp256k1_ecdsa_signature_parse_compact(secp256k1_context_static, sig, tmpsig);
174 0 : }
175 0 : if (overflow) {
176 : /* Overwrite the result again with a correctly-parsed but invalid
177 : signature if parsing failed. */
178 0 : memset(tmpsig, 0, 64);
179 0 : secp256k1_ecdsa_signature_parse_compact(secp256k1_context_static, sig, tmpsig);
180 0 : }
181 0 : return 1;
182 0 : }
183 :
184 0 : XOnlyPubKey::XOnlyPubKey(Span<const unsigned char> bytes)
185 : {
186 0 : assert(bytes.size() == 32);
187 0 : std::copy(bytes.begin(), bytes.end(), m_keydata.begin());
188 0 : }
189 :
190 0 : std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
191 : {
192 0 : std::vector<CKeyID> out;
193 : // For now, use the old full pubkey-based key derivation logic. As it is indexed by
194 : // Hash160(full pubkey), we need to return both a version prefixed with 0x02, and one
195 : // with 0x03.
196 0 : unsigned char b[33] = {0x02};
197 0 : std::copy(m_keydata.begin(), m_keydata.end(), b + 1);
198 0 : CPubKey fullpubkey;
199 0 : fullpubkey.Set(b, b + 33);
200 0 : out.push_back(fullpubkey.GetID());
201 0 : b[0] = 0x03;
202 0 : fullpubkey.Set(b, b + 33);
203 0 : out.push_back(fullpubkey.GetID());
204 0 : return out;
205 0 : }
206 :
207 0 : bool XOnlyPubKey::IsFullyValid() const
208 : {
209 : secp256k1_xonly_pubkey pubkey;
210 0 : return secp256k1_xonly_pubkey_parse(secp256k1_context_static, &pubkey, m_keydata.data());
211 : }
212 :
213 0 : bool XOnlyPubKey::VerifySchnorr(const uint256& msg, Span<const unsigned char> sigbytes) const
214 : {
215 0 : assert(sigbytes.size() == 64);
216 : secp256k1_xonly_pubkey pubkey;
217 0 : if (!secp256k1_xonly_pubkey_parse(secp256k1_context_static, &pubkey, m_keydata.data())) return false;
218 0 : return secp256k1_schnorrsig_verify(secp256k1_context_static, sigbytes.data(), msg.begin(), 32, &pubkey);
219 0 : }
220 :
221 2 : static const HashWriter HASHER_TAPTWEAK{TaggedHash("TapTweak")};
222 :
223 0 : uint256 XOnlyPubKey::ComputeTapTweakHash(const uint256* merkle_root) const
224 : {
225 0 : if (merkle_root == nullptr) {
226 : // We have no scripts. The actual tweak does not matter, but follow BIP341 here to
227 : // allow for reproducible tweaking.
228 0 : return (HashWriter{HASHER_TAPTWEAK} << m_keydata).GetSHA256();
229 : } else {
230 0 : return (HashWriter{HASHER_TAPTWEAK} << m_keydata << *merkle_root).GetSHA256();
231 : }
232 0 : }
233 :
234 0 : bool XOnlyPubKey::CheckTapTweak(const XOnlyPubKey& internal, const uint256& merkle_root, bool parity) const
235 : {
236 : secp256k1_xonly_pubkey internal_key;
237 0 : if (!secp256k1_xonly_pubkey_parse(secp256k1_context_static, &internal_key, internal.data())) return false;
238 0 : uint256 tweak = internal.ComputeTapTweakHash(&merkle_root);
239 0 : return secp256k1_xonly_pubkey_tweak_add_check(secp256k1_context_static, m_keydata.begin(), parity, &internal_key, tweak.begin());
240 0 : }
241 :
242 0 : std::optional<std::pair<XOnlyPubKey, bool>> XOnlyPubKey::CreateTapTweak(const uint256* merkle_root) const
243 : {
244 : secp256k1_xonly_pubkey base_point;
245 0 : if (!secp256k1_xonly_pubkey_parse(secp256k1_context_static, &base_point, data())) return std::nullopt;
246 : secp256k1_pubkey out;
247 0 : uint256 tweak = ComputeTapTweakHash(merkle_root);
248 0 : if (!secp256k1_xonly_pubkey_tweak_add(secp256k1_context_static, &out, &base_point, tweak.data())) return std::nullopt;
249 0 : int parity = -1;
250 0 : std::pair<XOnlyPubKey, bool> ret;
251 : secp256k1_xonly_pubkey out_xonly;
252 0 : if (!secp256k1_xonly_pubkey_from_pubkey(secp256k1_context_static, &out_xonly, &parity, &out)) return std::nullopt;
253 0 : secp256k1_xonly_pubkey_serialize(secp256k1_context_static, ret.first.begin(), &out_xonly);
254 0 : assert(parity == 0 || parity == 1);
255 0 : ret.second = parity;
256 0 : return ret;
257 0 : }
258 :
259 :
260 0 : bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
261 0 : if (!IsValid())
262 0 : return false;
263 : secp256k1_pubkey pubkey;
264 : secp256k1_ecdsa_signature sig;
265 0 : if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, vch, size())) {
266 0 : return false;
267 : }
268 0 : if (!ecdsa_signature_parse_der_lax(&sig, vchSig.data(), vchSig.size())) {
269 0 : return false;
270 : }
271 : /* libsecp256k1's ECDSA verification requires lower-S signatures, which have
272 : * not historically been enforced in Bitcoin, so normalize them first. */
273 0 : secp256k1_ecdsa_signature_normalize(secp256k1_context_static, &sig, &sig);
274 0 : return secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pubkey);
275 0 : }
276 :
277 0 : bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
278 0 : if (vchSig.size() != COMPACT_SIGNATURE_SIZE)
279 0 : return false;
280 0 : int recid = (vchSig[0] - 27) & 3;
281 0 : bool fComp = ((vchSig[0] - 27) & 4) != 0;
282 : secp256k1_pubkey pubkey;
283 : secp256k1_ecdsa_recoverable_signature sig;
284 0 : if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_static, &sig, &vchSig[1], recid)) {
285 0 : return false;
286 : }
287 0 : if (!secp256k1_ecdsa_recover(secp256k1_context_static, &pubkey, &sig, hash.begin())) {
288 0 : return false;
289 : }
290 : unsigned char pub[SIZE];
291 0 : size_t publen = SIZE;
292 0 : secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, fComp ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
293 0 : Set(pub, pub + publen);
294 0 : return true;
295 0 : }
296 :
297 0 : bool CPubKey::IsFullyValid() const {
298 0 : if (!IsValid())
299 0 : return false;
300 : secp256k1_pubkey pubkey;
301 0 : return secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, vch, size());
302 0 : }
303 :
304 0 : bool CPubKey::Decompress() {
305 0 : if (!IsValid())
306 0 : return false;
307 : secp256k1_pubkey pubkey;
308 0 : if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, vch, size())) {
309 0 : return false;
310 : }
311 : unsigned char pub[SIZE];
312 0 : size_t publen = SIZE;
313 0 : secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
314 0 : Set(pub, pub + publen);
315 0 : return true;
316 0 : }
317 :
318 0 : bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
319 0 : assert(IsValid());
320 0 : assert((nChild >> 31) == 0);
321 0 : assert(size() == COMPRESSED_SIZE);
322 : unsigned char out[64];
323 0 : BIP32Hash(cc, nChild, *begin(), begin()+1, out);
324 0 : memcpy(ccChild.begin(), out+32, 32);
325 : secp256k1_pubkey pubkey;
326 0 : if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, vch, size())) {
327 0 : return false;
328 : }
329 0 : if (!secp256k1_ec_pubkey_tweak_add(secp256k1_context_static, &pubkey, out)) {
330 0 : return false;
331 : }
332 : unsigned char pub[COMPRESSED_SIZE];
333 0 : size_t publen = COMPRESSED_SIZE;
334 0 : secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, SECP256K1_EC_COMPRESSED);
335 0 : pubkeyChild.Set(pub, pub + publen);
336 0 : return true;
337 0 : }
338 :
339 0 : EllSwiftPubKey::EllSwiftPubKey(Span<const std::byte> ellswift) noexcept
340 : {
341 0 : assert(ellswift.size() == SIZE);
342 0 : std::copy(ellswift.begin(), ellswift.end(), m_pubkey.begin());
343 0 : }
344 :
345 0 : CPubKey EllSwiftPubKey::Decode() const
346 : {
347 : secp256k1_pubkey pubkey;
348 0 : secp256k1_ellswift_decode(secp256k1_context_static, &pubkey, UCharCast(m_pubkey.data()));
349 :
350 0 : size_t sz = CPubKey::COMPRESSED_SIZE;
351 : std::array<uint8_t, CPubKey::COMPRESSED_SIZE> vch_bytes;
352 :
353 0 : secp256k1_ec_pubkey_serialize(secp256k1_context_static, vch_bytes.data(), &sz, &pubkey, SECP256K1_EC_COMPRESSED);
354 0 : assert(sz == vch_bytes.size());
355 :
356 0 : return CPubKey{vch_bytes.begin(), vch_bytes.end()};
357 : }
358 :
359 0 : void CExtPubKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
360 0 : code[0] = nDepth;
361 0 : memcpy(code+1, vchFingerprint, 4);
362 0 : WriteBE32(code+5, nChild);
363 0 : memcpy(code+9, chaincode.begin(), 32);
364 0 : assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
365 0 : memcpy(code+41, pubkey.begin(), CPubKey::COMPRESSED_SIZE);
366 0 : }
367 :
368 0 : void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
369 0 : nDepth = code[0];
370 0 : memcpy(vchFingerprint, code+1, 4);
371 0 : nChild = ReadBE32(code+5);
372 0 : memcpy(chaincode.begin(), code+9, 32);
373 0 : pubkey.Set(code+41, code+BIP32_EXTKEY_SIZE);
374 0 : if ((nDepth == 0 && (nChild != 0 || ReadLE32(vchFingerprint) != 0)) || !pubkey.IsFullyValid()) pubkey = CPubKey();
375 0 : }
376 :
377 0 : void CExtPubKey::EncodeWithVersion(unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE]) const
378 : {
379 0 : memcpy(code, version, 4);
380 0 : Encode(&code[4]);
381 0 : }
382 :
383 0 : void CExtPubKey::DecodeWithVersion(const unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE])
384 : {
385 0 : memcpy(version, code, 4);
386 0 : Decode(&code[4]);
387 0 : }
388 :
389 0 : bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
390 0 : if (nDepth == std::numeric_limits<unsigned char>::max()) return false;
391 0 : out.nDepth = nDepth + 1;
392 0 : CKeyID id = pubkey.GetID();
393 0 : memcpy(out.vchFingerprint, &id, 4);
394 0 : out.nChild = _nChild;
395 0 : return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
396 0 : }
397 :
398 0 : /* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
399 : secp256k1_ecdsa_signature sig;
400 0 : if (!ecdsa_signature_parse_der_lax(&sig, vchSig.data(), vchSig.size())) {
401 0 : return false;
402 : }
403 0 : return (!secp256k1_ecdsa_signature_normalize(secp256k1_context_static, nullptr, &sig));
404 0 : }
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