2014-12-16 17:47:57 -08:00
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// Copyright (c) 2009-2014 The Bitcoin Core developers
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2014-10-31 01:36:30 -07:00
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// Distributed under the MIT software license, see the accompanying
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2014-10-21 12:04:03 -07:00
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include "ecwrapper.h"
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#include "serialize.h"
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#include "uint256.h"
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#include <openssl/bn.h>
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#include <openssl/obj_mac.h>
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namespace {
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2015-08-17 21:54:19 -07:00
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class ecgroup_order
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{
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public:
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static const EC_GROUP* get()
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{
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static const ecgroup_order wrapper;
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return wrapper.pgroup;
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}
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private:
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ecgroup_order()
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: pgroup(EC_GROUP_new_by_curve_name(NID_secp256k1))
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{
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}
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~ecgroup_order()
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{
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EC_GROUP_free(pgroup);
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}
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EC_GROUP* pgroup;
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};
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2014-10-30 17:43:19 -07:00
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/**
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* Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
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* recid selects which key is recovered
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* if check is non-zero, additional checks are performed
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*/
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2014-10-21 12:04:03 -07:00
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int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
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{
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if (!eckey) return 0;
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int ret = 0;
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BN_CTX *ctx = NULL;
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BIGNUM *x = NULL;
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BIGNUM *e = NULL;
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BIGNUM *order = NULL;
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BIGNUM *sor = NULL;
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BIGNUM *eor = NULL;
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BIGNUM *field = NULL;
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EC_POINT *R = NULL;
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EC_POINT *O = NULL;
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EC_POINT *Q = NULL;
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BIGNUM *rr = NULL;
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BIGNUM *zero = NULL;
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int n = 0;
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int i = recid / 2;
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2016-09-21 01:35:31 -07:00
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const BIGNUM *sig_r, *sig_s;
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ECDSA_SIG_get0(ecsig, &sig_r, &sig_s);
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2014-10-21 12:04:03 -07:00
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const EC_GROUP *group = EC_KEY_get0_group(eckey);
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if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
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BN_CTX_start(ctx);
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order = BN_CTX_get(ctx);
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if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
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x = BN_CTX_get(ctx);
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if (!BN_copy(x, order)) { ret=-1; goto err; }
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if (!BN_mul_word(x, i)) { ret=-1; goto err; }
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2016-09-21 01:35:31 -07:00
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if (!BN_add(x, x, sig_r)) { ret=-1; goto err; }
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2014-10-21 12:04:03 -07:00
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field = BN_CTX_get(ctx);
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if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
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if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
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if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
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if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
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if (check)
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{
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if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
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if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
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if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
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}
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if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
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n = EC_GROUP_get_degree(group);
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e = BN_CTX_get(ctx);
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if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
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if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
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zero = BN_CTX_get(ctx);
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if (!BN_zero(zero)) { ret=-1; goto err; }
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if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
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rr = BN_CTX_get(ctx);
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2016-09-21 01:35:31 -07:00
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if (!BN_mod_inverse(rr, sig_r, order, ctx)) { ret=-1; goto err; }
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2014-10-21 12:04:03 -07:00
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sor = BN_CTX_get(ctx);
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2016-09-21 01:35:31 -07:00
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if (!BN_mod_mul(sor, sig_s, rr, order, ctx)) { ret=-1; goto err; }
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2014-10-21 12:04:03 -07:00
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eor = BN_CTX_get(ctx);
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if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
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if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
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if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
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ret = 1;
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err:
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if (ctx) {
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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}
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if (R != NULL) EC_POINT_free(R);
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if (O != NULL) EC_POINT_free(O);
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if (Q != NULL) EC_POINT_free(Q);
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return ret;
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}
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} // anon namespace
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CECKey::CECKey() {
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2015-08-17 21:54:19 -07:00
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pkey = EC_KEY_new();
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2014-10-21 12:04:03 -07:00
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assert(pkey != NULL);
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2015-08-17 21:54:19 -07:00
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int result = EC_KEY_set_group(pkey, ecgroup_order::get());
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assert(result);
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2014-10-21 12:04:03 -07:00
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}
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CECKey::~CECKey() {
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EC_KEY_free(pkey);
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}
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void CECKey::GetPubKey(std::vector<unsigned char> &pubkey, bool fCompressed) {
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EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
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int nSize = i2o_ECPublicKey(pkey, NULL);
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assert(nSize);
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assert(nSize <= 65);
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pubkey.clear();
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pubkey.resize(nSize);
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unsigned char *pbegin(begin_ptr(pubkey));
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int nSize2 = i2o_ECPublicKey(pkey, &pbegin);
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assert(nSize == nSize2);
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}
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bool CECKey::SetPubKey(const unsigned char* pubkey, size_t size) {
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return o2i_ECPublicKey(&pkey, &pubkey, size) != NULL;
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}
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bool CECKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
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2015-01-09 19:06:08 -08:00
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if (vchSig.empty())
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return false;
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2015-01-09 13:39:12 -08:00
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// New versions of OpenSSL will reject non-canonical DER signatures. de/re-serialize first.
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unsigned char *norm_der = NULL;
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ECDSA_SIG *norm_sig = ECDSA_SIG_new();
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const unsigned char* sigptr = &vchSig[0];
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2015-01-11 02:08:53 -08:00
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assert(norm_sig);
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if (d2i_ECDSA_SIG(&norm_sig, &sigptr, vchSig.size()) == NULL)
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{
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/* As of OpenSSL 1.0.0p d2i_ECDSA_SIG frees and nulls the pointer on
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* error. But OpenSSL's own use of this function redundantly frees the
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* result. As ECDSA_SIG_free(NULL) is a no-op, and in the absence of a
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* clear contract for the function behaving the same way is more
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* conservative.
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*/
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ECDSA_SIG_free(norm_sig);
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return false;
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}
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2015-01-09 13:39:12 -08:00
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int derlen = i2d_ECDSA_SIG(norm_sig, &norm_der);
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ECDSA_SIG_free(norm_sig);
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if (derlen <= 0)
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2014-10-21 12:04:03 -07:00
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return false;
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2015-01-09 13:39:12 -08:00
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// -1 = error, 0 = bad sig, 1 = good
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bool ret = ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), norm_der, derlen, pkey) == 1;
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OPENSSL_free(norm_der);
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return ret;
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2014-10-21 12:04:03 -07:00
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}
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bool CECKey::Recover(const uint256 &hash, const unsigned char *p64, int rec)
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{
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if (rec<0 || rec>=3)
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return false;
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2016-09-29 18:17:14 -07:00
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ECDSA_SIG *sig = ECDSA_SIG_new();
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BIGNUM *sig_r = BN_bin2bn(&p64[0], 32, nullptr);
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BIGNUM *sig_s = BN_bin2bn(&p64[32], 32, nullptr);
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assert(sig && sig_r && sig_s);
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2016-09-29 22:54:16 -07:00
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bool ret = ECDSA_SIG_set0(sig, sig_r, sig_s);
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assert(ret);
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ret = ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), rec, 0) == 1;
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2014-10-21 12:04:03 -07:00
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ECDSA_SIG_free(sig);
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return ret;
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}
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bool CECKey::TweakPublic(const unsigned char vchTweak[32]) {
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bool ret = true;
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BN_CTX *ctx = BN_CTX_new();
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BN_CTX_start(ctx);
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BIGNUM *bnTweak = BN_CTX_get(ctx);
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BIGNUM *bnOrder = BN_CTX_get(ctx);
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BIGNUM *bnOne = BN_CTX_get(ctx);
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const EC_GROUP *group = EC_KEY_get0_group(pkey);
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EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
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BN_bin2bn(vchTweak, 32, bnTweak);
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if (BN_cmp(bnTweak, bnOrder) >= 0)
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ret = false; // extremely unlikely
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EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group);
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BN_one(bnOne);
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EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx);
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if (EC_POINT_is_at_infinity(group, point))
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ret = false; // ridiculously unlikely
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EC_KEY_set_public_key(pkey, point);
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EC_POINT_free(point);
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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return ret;
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}
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bool CECKey::SanityCheck()
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{
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2015-08-17 21:54:19 -07:00
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const EC_GROUP *pgroup = ecgroup_order::get();
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if(pgroup == NULL)
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2014-10-21 12:04:03 -07:00
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return false;
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// TODO Is there more EC functionality that could be missing?
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return true;
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}
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