Line data Source code
1 : // Copyright (c) 2009-2019 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 <key.h>
7 :
8 : #include <crypto/common.h>
9 : #include <crypto/hmac_sha512.h>
10 : #include <random.h>
11 :
12 : #include <secp256k1.h>
13 : #include <secp256k1_recovery.h>
14 :
15 : static secp256k1_context* secp256k1_context_sign = nullptr;
16 :
17 : /** These functions are taken from the libsecp256k1 distribution and are very ugly. */
18 :
19 : /**
20 : * This parses a format loosely based on a DER encoding of the ECPrivateKey type from
21 : * section C.4 of SEC 1 <http://www.secg.org/sec1-v2.pdf>, with the following caveats:
22 : *
23 : * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not
24 : * required to be encoded as one octet if it is less than 256, as DER would require.
25 : * * The octet-length of the SEQUENCE must not be greater than the remaining
26 : * length of the key encoding, but need not match it (i.e. the encoding may contain
27 : * junk after the encoded SEQUENCE).
28 : * * The privateKey OCTET STRING is zero-filled on the left to 32 octets.
29 : * * Anything after the encoding of the privateKey OCTET STRING is ignored, whether
30 : * or not it is validly encoded DER.
31 : *
32 : * out32 must point to an output buffer of length at least 32 bytes.
33 : */
34 10907 : int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) {
35 10907 : const unsigned char *end = seckey + seckeylen;
36 10907 : memset(out32, 0, 32);
37 : /* sequence header */
38 10907 : if (end - seckey < 1 || *seckey != 0x30u) {
39 0 : return 0;
40 : }
41 10907 : seckey++;
42 : /* sequence length constructor */
43 10907 : if (end - seckey < 1 || !(*seckey & 0x80u)) {
44 0 : return 0;
45 : }
46 10907 : ptrdiff_t lenb = *seckey & ~0x80u; seckey++;
47 10907 : if (lenb < 1 || lenb > 2) {
48 0 : return 0;
49 : }
50 10907 : if (end - seckey < lenb) {
51 0 : return 0;
52 : }
53 : /* sequence length */
54 10907 : ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);
55 10907 : seckey += lenb;
56 10907 : if (end - seckey < len) {
57 0 : return 0;
58 : }
59 : /* sequence element 0: version number (=1) */
60 10907 : if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) {
61 0 : return 0;
62 : }
63 10907 : seckey += 3;
64 : /* sequence element 1: octet string, up to 32 bytes */
65 10907 : if (end - seckey < 2 || seckey[0] != 0x04u) {
66 0 : return 0;
67 : }
68 10907 : ptrdiff_t oslen = seckey[1];
69 10907 : seckey += 2;
70 10907 : if (oslen > 32 || end - seckey < oslen) {
71 0 : return 0;
72 : }
73 10907 : memcpy(out32 + (32 - oslen), seckey, oslen);
74 10907 : if (!secp256k1_ec_seckey_verify(ctx, out32)) {
75 0 : memset(out32, 0, 32);
76 0 : return 0;
77 : }
78 10907 : return 1;
79 10907 : }
80 :
81 : /**
82 : * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1
83 : * <http://www.secg.org/sec1-v2.pdf>. The optional parameters and publicKey fields are
84 : * included.
85 : *
86 : * seckey must point to an output buffer of length at least CKey::SIZE bytes.
87 : * seckeylen must initially be set to the size of the seckey buffer. Upon return it
88 : * will be set to the number of bytes used in the buffer.
89 : * key32 must point to a 32-byte raw private key.
90 : */
91 26238 : int ec_seckey_export_der(const secp256k1_context *ctx, unsigned char *seckey, size_t *seckeylen, const unsigned char *key32, bool compressed) {
92 26238 : assert(*seckeylen >= CKey::SIZE);
93 26238 : secp256k1_pubkey pubkey;
94 26238 : size_t pubkeylen = 0;
95 26238 : if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
96 0 : *seckeylen = 0;
97 0 : return 0;
98 : }
99 26238 : if (compressed) {
100 : static const unsigned char begin[] = {
101 : 0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
102 : };
103 : static const unsigned char middle[] = {
104 : 0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
105 : 0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
106 : 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
107 : 0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
108 : 0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
109 : 0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
110 : 0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
111 : 0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
112 : 0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
113 : };
114 : unsigned char *ptr = seckey;
115 21226 : memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
116 21226 : memcpy(ptr, key32, 32); ptr += 32;
117 21226 : memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
118 21226 : pubkeylen = CPubKey::COMPRESSED_SIZE;
119 21226 : secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
120 21226 : ptr += pubkeylen;
121 21226 : *seckeylen = ptr - seckey;
122 21226 : assert(*seckeylen == CKey::COMPRESSED_SIZE);
123 21226 : } else {
124 : static const unsigned char begin[] = {
125 : 0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
126 : };
127 : static const unsigned char middle[] = {
128 : 0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
129 : 0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
130 : 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
131 : 0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
132 : 0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
133 : 0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
134 : 0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
135 : 0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
136 : 0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
137 : 0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
138 : 0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
139 : };
140 : unsigned char *ptr = seckey;
141 5012 : memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
142 5012 : memcpy(ptr, key32, 32); ptr += 32;
143 5012 : memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
144 5012 : pubkeylen = CPubKey::SIZE;
145 5012 : secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
146 5012 : ptr += pubkeylen;
147 5012 : *seckeylen = ptr - seckey;
148 5012 : assert(*seckeylen == CKey::SIZE);
149 : }
150 26238 : return 1;
151 26238 : }
152 :
153 30287 : bool CKey::Check(const unsigned char *vch) {
154 30287 : return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
155 : }
156 :
157 6042 : void CKey::MakeNewKey(bool fCompressedIn) {
158 6042 : do {
159 6042 : GetStrongRandBytes(keydata.data(), keydata.size());
160 6042 : } while (!Check(keydata.data()));
161 6042 : fValid = true;
162 6042 : fCompressed = fCompressedIn;
163 6042 : }
164 :
165 2 : bool CKey::Negate()
166 : {
167 2 : assert(fValid);
168 2 : return secp256k1_ec_seckey_negate(secp256k1_context_sign, keydata.data());
169 : }
170 :
171 26238 : CPrivKey CKey::GetPrivKey() const {
172 26238 : assert(fValid);
173 26238 : CPrivKey seckey;
174 : int ret;
175 26238 : size_t seckeylen;
176 26238 : seckey.resize(SIZE);
177 26238 : seckeylen = SIZE;
178 26238 : ret = ec_seckey_export_der(secp256k1_context_sign, seckey.data(), &seckeylen, begin(), fCompressed);
179 26238 : assert(ret);
180 26238 : seckey.resize(seckeylen);
181 : return seckey;
182 26238 : }
183 :
184 946786 : CPubKey CKey::GetPubKey() const {
185 946786 : assert(fValid);
186 946786 : secp256k1_pubkey pubkey;
187 946786 : size_t clen = CPubKey::SIZE;
188 946786 : CPubKey result;
189 946786 : int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
190 946786 : assert(ret);
191 946786 : secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
192 946786 : assert(result.size() == clen);
193 946786 : assert(result.IsValid());
194 : return result;
195 946786 : }
196 :
197 : // Check that the sig has a low R value and will be less than 71 bytes
198 108200 : bool SigHasLowR(const secp256k1_ecdsa_signature* sig)
199 : {
200 108200 : unsigned char compact_sig[64];
201 108200 : secp256k1_ecdsa_signature_serialize_compact(secp256k1_context_sign, compact_sig, sig);
202 :
203 : // In DER serialization, all values are interpreted as big-endian, signed integers. The highest bit in the integer indicates
204 : // its signed-ness; 0 is positive, 1 is negative. When the value is interpreted as a negative integer, it must be converted
205 : // to a positive value by prepending a 0x00 byte so that the highest bit is 0. We can avoid this prepending by ensuring that
206 : // our highest bit is always 0, and thus we must check that the first byte is less than 0x80.
207 216400 : return compact_sig[0] < 0x80;
208 108200 : }
209 :
210 54875 : bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool grind, uint32_t test_case) const {
211 54875 : if (!fValid)
212 0 : return false;
213 54875 : vchSig.resize(CPubKey::SIGNATURE_SIZE);
214 54875 : size_t nSigLen = CPubKey::SIGNATURE_SIZE;
215 54875 : unsigned char extra_entropy[32] = {0};
216 54875 : WriteLE32(extra_entropy, test_case);
217 54875 : secp256k1_ecdsa_signature sig;
218 : uint32_t counter = 0;
219 54875 : int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, (!grind && test_case) ? extra_entropy : nullptr);
220 :
221 : // Grind for low R
222 108200 : while (ret && !SigHasLowR(&sig) && grind) {
223 53325 : WriteLE32(extra_entropy, ++counter);
224 53325 : ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, extra_entropy);
225 : }
226 54875 : assert(ret);
227 54875 : secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, vchSig.data(), &nSigLen, &sig);
228 54875 : vchSig.resize(nSigLen);
229 : return true;
230 54875 : }
231 :
232 30679 : bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
233 30679 : if (pubkey.IsCompressed() != fCompressed) {
234 8 : return false;
235 : }
236 30671 : unsigned char rnd[8];
237 30671 : std::string str = "Bitcoin key verification\n";
238 30671 : GetRandBytes(rnd, sizeof(rnd));
239 30671 : uint256 hash;
240 30671 : CHash256().Write(MakeUCharSpan(str)).Write(rnd).Finalize(hash);
241 30671 : std::vector<unsigned char> vchSig;
242 30671 : Sign(hash, vchSig);
243 30671 : return pubkey.Verify(hash, vchSig);
244 30679 : }
245 :
246 83 : bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
247 83 : if (!fValid)
248 1 : return false;
249 82 : vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE);
250 82 : int rec = -1;
251 82 : secp256k1_ecdsa_recoverable_signature sig;
252 82 : int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
253 82 : assert(ret);
254 82 : ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, &vchSig[1], &rec, &sig);
255 82 : assert(ret);
256 82 : assert(rec != -1);
257 82 : vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
258 : return true;
259 83 : }
260 :
261 10907 : bool CKey::Load(const CPrivKey &seckey, const CPubKey &vchPubKey, bool fSkipCheck=false) {
262 10907 : if (!ec_seckey_import_der(secp256k1_context_sign, (unsigned char*)begin(), seckey.data(), seckey.size()))
263 0 : return false;
264 10907 : fCompressed = vchPubKey.IsCompressed();
265 10907 : fValid = true;
266 :
267 10907 : if (fSkipCheck)
268 10907 : return true;
269 :
270 0 : return VerifyPubKey(vchPubKey);
271 10907 : }
272 :
273 82396 : bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
274 82396 : assert(IsValid());
275 82396 : assert(IsCompressed());
276 82396 : std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
277 82396 : if ((nChild >> 31) == 0) {
278 7355 : CPubKey pubkey = GetPubKey();
279 7355 : assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
280 7355 : BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
281 7355 : } else {
282 75041 : assert(size() == 32);
283 75041 : BIP32Hash(cc, nChild, 0, begin(), vout.data());
284 : }
285 82396 : memcpy(ccChild.begin(), vout.data()+32, 32);
286 82396 : memcpy((unsigned char*)keyChild.begin(), begin(), 32);
287 82396 : bool ret = secp256k1_ec_seckey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
288 82396 : keyChild.fCompressed = true;
289 82396 : keyChild.fValid = ret;
290 : return ret;
291 82396 : }
292 :
293 82396 : bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
294 82396 : out.nDepth = nDepth + 1;
295 82396 : CKeyID id = key.GetPubKey().GetID();
296 82396 : memcpy(&out.vchFingerprint[0], &id, 4);
297 82396 : out.nChild = _nChild;
298 164792 : return key.Derive(out.key, out.chaincode, _nChild, chaincode);
299 82396 : }
300 :
301 19968 : void CExtKey::SetSeed(const unsigned char *seed, unsigned int nSeedLen) {
302 : static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
303 19968 : std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
304 19968 : CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
305 19968 : key.Set(vout.data(), vout.data() + 32, true);
306 19968 : memcpy(chaincode.begin(), vout.data() + 32, 32);
307 19968 : nDepth = 0;
308 19968 : nChild = 0;
309 19968 : memset(vchFingerprint, 0, sizeof(vchFingerprint));
310 19968 : }
311 :
312 14374 : CExtPubKey CExtKey::Neuter() const {
313 14374 : CExtPubKey ret;
314 14374 : ret.nDepth = nDepth;
315 14374 : memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
316 14374 : ret.nChild = nChild;
317 14374 : ret.pubkey = key.GetPubKey();
318 14374 : ret.chaincode = chaincode;
319 14374 : return ret;
320 : }
321 :
322 139 : void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
323 139 : code[0] = nDepth;
324 139 : memcpy(code+1, vchFingerprint, 4);
325 139 : code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
326 139 : code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
327 139 : memcpy(code+9, chaincode.begin(), 32);
328 139 : code[41] = 0;
329 139 : assert(key.size() == 32);
330 139 : memcpy(code+42, key.begin(), 32);
331 139 : }
332 :
333 137 : void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
334 137 : nDepth = code[0];
335 137 : memcpy(vchFingerprint, code+1, 4);
336 137 : nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
337 137 : memcpy(chaincode.begin(), code+9, 32);
338 137 : key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
339 137 : }
340 :
341 531 : bool ECC_InitSanityCheck() {
342 531 : CKey key;
343 531 : key.MakeNewKey(true);
344 531 : CPubKey pubkey = key.GetPubKey();
345 531 : return key.VerifyPubKey(pubkey);
346 531 : }
347 :
348 1028 : void ECC_Start() {
349 1028 : assert(secp256k1_context_sign == nullptr);
350 :
351 1028 : secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
352 1028 : assert(ctx != nullptr);
353 :
354 : {
355 : // Pass in a random blinding seed to the secp256k1 context.
356 1028 : std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
357 1028 : GetRandBytes(vseed.data(), 32);
358 1028 : bool ret = secp256k1_context_randomize(ctx, vseed.data());
359 1028 : assert(ret);
360 1028 : }
361 :
362 1028 : secp256k1_context_sign = ctx;
363 1028 : }
364 :
365 1022 : void ECC_Stop() {
366 1022 : secp256k1_context *ctx = secp256k1_context_sign;
367 1022 : secp256k1_context_sign = nullptr;
368 :
369 1022 : if (ctx) {
370 1022 : secp256k1_context_destroy(ctx);
371 1022 : }
372 1022 : }
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