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
|
// Copyright (c) 2009-2014 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "ecwrapper.h"
#include "serialize.h"
#include "uint256.h"
#include <openssl/bn.h>
#include <openssl/ecdsa.h>
#include <openssl/obj_mac.h>
namespace {
/**
* Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
* recid selects which key is recovered
* if check is non-zero, additional checks are performed
*/
int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
{
if (!eckey) return 0;
int ret = 0;
BN_CTX *ctx = NULL;
BIGNUM *x = NULL;
BIGNUM *e = NULL;
BIGNUM *order = NULL;
BIGNUM *sor = NULL;
BIGNUM *eor = NULL;
BIGNUM *field = NULL;
EC_POINT *R = NULL;
EC_POINT *O = NULL;
EC_POINT *Q = NULL;
BIGNUM *rr = NULL;
BIGNUM *zero = NULL;
int n = 0;
int i = recid / 2;
const EC_GROUP *group = EC_KEY_get0_group(eckey);
if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
BN_CTX_start(ctx);
order = BN_CTX_get(ctx);
if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
x = BN_CTX_get(ctx);
if (!BN_copy(x, order)) { ret=-1; goto err; }
if (!BN_mul_word(x, i)) { ret=-1; goto err; }
if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
field = BN_CTX_get(ctx);
if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
if (check)
{
if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
}
if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
n = EC_GROUP_get_degree(group);
e = BN_CTX_get(ctx);
if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
zero = BN_CTX_get(ctx);
if (!BN_zero(zero)) { ret=-1; goto err; }
if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
rr = BN_CTX_get(ctx);
if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
sor = BN_CTX_get(ctx);
if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
eor = BN_CTX_get(ctx);
if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
ret = 1;
err:
if (ctx) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
if (R != NULL) EC_POINT_free(R);
if (O != NULL) EC_POINT_free(O);
if (Q != NULL) EC_POINT_free(Q);
return ret;
}
} // anon namespace
CECKey::CECKey() {
pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
assert(pkey != NULL);
}
CECKey::~CECKey() {
EC_KEY_free(pkey);
}
void CECKey::GetPubKey(std::vector<unsigned char> &pubkey, bool fCompressed) {
EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
int nSize = i2o_ECPublicKey(pkey, NULL);
assert(nSize);
assert(nSize <= 65);
pubkey.clear();
pubkey.resize(nSize);
unsigned char *pbegin(begin_ptr(pubkey));
int nSize2 = i2o_ECPublicKey(pkey, &pbegin);
assert(nSize == nSize2);
}
bool CECKey::SetPubKey(const unsigned char* pubkey, size_t size) {
return o2i_ECPublicKey(&pkey, &pubkey, size) != NULL;
}
bool CECKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
// New versions of OpenSSL will reject non-canonical DER signatures. de/re-serialize first.
unsigned char *norm_der = NULL;
ECDSA_SIG *norm_sig = ECDSA_SIG_new();
const unsigned char* sigptr = &vchSig[0];
d2i_ECDSA_SIG(&norm_sig, &sigptr, vchSig.size());
int derlen = i2d_ECDSA_SIG(norm_sig, &norm_der);
ECDSA_SIG_free(norm_sig);
if (derlen <= 0)
return false;
// -1 = error, 0 = bad sig, 1 = good
bool ret = ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), norm_der, derlen, pkey) == 1;
OPENSSL_free(norm_der);
return ret;
}
bool CECKey::Recover(const uint256 &hash, const unsigned char *p64, int rec)
{
if (rec<0 || rec>=3)
return false;
ECDSA_SIG *sig = ECDSA_SIG_new();
BN_bin2bn(&p64[0], 32, sig->r);
BN_bin2bn(&p64[32], 32, sig->s);
bool ret = ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), rec, 0) == 1;
ECDSA_SIG_free(sig);
return ret;
}
bool CECKey::TweakPublic(const unsigned char vchTweak[32]) {
bool ret = true;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
BIGNUM *bnTweak = BN_CTX_get(ctx);
BIGNUM *bnOrder = BN_CTX_get(ctx);
BIGNUM *bnOne = BN_CTX_get(ctx);
const EC_GROUP *group = EC_KEY_get0_group(pkey);
EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
BN_bin2bn(vchTweak, 32, bnTweak);
if (BN_cmp(bnTweak, bnOrder) >= 0)
ret = false; // extremely unlikely
EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group);
BN_one(bnOne);
EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx);
if (EC_POINT_is_at_infinity(group, point))
ret = false; // ridiculously unlikely
EC_KEY_set_public_key(pkey, point);
EC_POINT_free(point);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
bool CECKey::SanityCheck()
{
EC_KEY *pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
if(pkey == NULL)
return false;
EC_KEY_free(pkey);
// TODO Is there more EC functionality that could be missing?
return true;
}
|
