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// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <map>
#include <openssl/ecdsa.h>
#include <openssl/obj_mac.h>
#include "key.h"
// Generate a private key from just the secret parameter
int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
{
int ok = 0;
BN_CTX *ctx = NULL;
EC_POINT *pub_key = NULL;
if (!eckey) return 0;
const EC_GROUP *group = EC_KEY_get0_group(eckey);
if ((ctx = BN_CTX_new()) == NULL)
goto err;
pub_key = EC_POINT_new(group);
if (pub_key == NULL)
goto err;
if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
goto err;
EC_KEY_set_private_key(eckey,priv_key);
EC_KEY_set_public_key(eckey,pub_key);
ok = 1;
err:
if (pub_key)
EC_POINT_free(pub_key);
if (ctx != NULL)
BN_CTX_free(ctx);
return(ok);
}
// 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;
}
void CKey::SetCompressedPubKey()
{
EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
fCompressedPubKey = true;
}
void CKey::Reset()
{
fCompressedPubKey = false;
if (pkey != NULL)
EC_KEY_free(pkey);
pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
if (pkey == NULL)
throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
fSet = false;
}
CKey::CKey()
{
pkey = NULL;
Reset();
}
CKey::CKey(const CKey& b)
{
pkey = EC_KEY_dup(b.pkey);
if (pkey == NULL)
throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
fSet = b.fSet;
}
CKey& CKey::operator=(const CKey& b)
{
if (!EC_KEY_copy(pkey, b.pkey))
throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
fSet = b.fSet;
return (*this);
}
CKey::~CKey()
{
EC_KEY_free(pkey);
}
bool CKey::IsNull() const
{
return !fSet;
}
bool CKey::IsCompressed() const
{
return fCompressedPubKey;
}
void CKey::MakeNewKey(bool fCompressed)
{
if (!EC_KEY_generate_key(pkey))
throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
if (fCompressed)
SetCompressedPubKey();
fSet = true;
}
bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
{
const unsigned char* pbegin = &vchPrivKey[0];
if (d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
{
// In testing, d2i_ECPrivateKey can return true
// but fill in pkey with a key that fails
// EC_KEY_check_key, so:
if (EC_KEY_check_key(pkey))
{
fSet = true;
return true;
}
}
// If vchPrivKey data is bad d2i_ECPrivateKey() can
// leave pkey in a state where calling EC_KEY_free()
// crashes. To avoid that, set pkey to NULL and
// leak the memory (a leak is better than a crash)
pkey = NULL;
Reset();
return false;
}
bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
{
EC_KEY_free(pkey);
pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
if (pkey == NULL)
throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
if (vchSecret.size() != 32)
throw key_error("CKey::SetSecret() : secret must be 32 bytes");
BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
if (bn == NULL)
throw key_error("CKey::SetSecret() : BN_bin2bn failed");
if (!EC_KEY_regenerate_key(pkey,bn))
{
BN_clear_free(bn);
throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
}
BN_clear_free(bn);
fSet = true;
if (fCompressed || fCompressedPubKey)
SetCompressedPubKey();
return true;
}
CSecret CKey::GetSecret(bool &fCompressed) const
{
CSecret vchRet;
vchRet.resize(32);
const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
int nBytes = BN_num_bytes(bn);
if (bn == NULL)
throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
if (n != nBytes)
throw key_error("CKey::GetSecret(): BN_bn2bin failed");
fCompressed = fCompressedPubKey;
return vchRet;
}
CPrivKey CKey::GetPrivKey() const
{
int nSize = i2d_ECPrivateKey(pkey, NULL);
if (!nSize)
throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
CPrivKey vchPrivKey(nSize, 0);
unsigned char* pbegin = &vchPrivKey[0];
if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
return vchPrivKey;
}
bool CKey::SetPubKey(const CPubKey& vchPubKey)
{
const unsigned char* pbegin = &vchPubKey.vchPubKey[0];
if (o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
{
fSet = true;
if (vchPubKey.vchPubKey.size() == 33)
SetCompressedPubKey();
return true;
}
pkey = NULL;
Reset();
return false;
}
CPubKey CKey::GetPubKey() const
{
int nSize = i2o_ECPublicKey(pkey, NULL);
if (!nSize)
throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
std::vector<unsigned char> vchPubKey(nSize, 0);
unsigned char* pbegin = &vchPubKey[0];
if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
return CPubKey(vchPubKey);
}
bool CKey::Sign(uint256 hash, std::vector<unsigned char>& vchSig)
{
unsigned int nSize = ECDSA_size(pkey);
vchSig.resize(nSize); // Make sure it is big enough
if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
{
vchSig.clear();
return false;
}
vchSig.resize(nSize); // Shrink to fit actual size
return true;
}
// create a compact signature (65 bytes), which allows reconstructing the used public key
// The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
// The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
// 0x1D = second key with even y, 0x1E = second key with odd y
bool CKey::SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
{
bool fOk = false;
ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
if (sig==NULL)
return false;
vchSig.clear();
vchSig.resize(65,0);
int nBitsR = BN_num_bits(sig->r);
int nBitsS = BN_num_bits(sig->s);
if (nBitsR <= 256 && nBitsS <= 256)
{
int nRecId = -1;
for (int i=0; i<4; i++)
{
CKey keyRec;
keyRec.fSet = true;
if (fCompressedPubKey)
keyRec.SetCompressedPubKey();
if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
if (keyRec.GetPubKey() == this->GetPubKey())
{
nRecId = i;
break;
}
}
if (nRecId == -1)
throw key_error("CKey::SignCompact() : unable to construct recoverable key");
vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
fOk = true;
}
ECDSA_SIG_free(sig);
return fOk;
}
// reconstruct public key from a compact signature
// This is only slightly more CPU intensive than just verifying it.
// If this function succeeds, the recovered public key is guaranteed to be valid
// (the signature is a valid signature of the given data for that key)
bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
{
if (vchSig.size() != 65)
return false;
int nV = vchSig[0];
if (nV<27 || nV>=35)
return false;
ECDSA_SIG *sig = ECDSA_SIG_new();
BN_bin2bn(&vchSig[1],32,sig->r);
BN_bin2bn(&vchSig[33],32,sig->s);
EC_KEY_free(pkey);
pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
if (nV >= 31)
{
SetCompressedPubKey();
nV -= 4;
}
if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
{
fSet = true;
ECDSA_SIG_free(sig);
return true;
}
return false;
}
bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
{
// -1 = error, 0 = bad sig, 1 = good
if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
return false;
return true;
}
bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
{
CKey key;
if (!key.SetCompactSignature(hash, vchSig))
return false;
if (GetPubKey() != key.GetPubKey())
return false;
return true;
}
bool CKey::IsValid()
{
if (!fSet)
return false;
if (!EC_KEY_check_key(pkey))
return false;
bool fCompr;
CSecret secret = GetSecret(fCompr);
CKey key2;
key2.SetSecret(secret, fCompr);
return GetPubKey() == key2.GetPubKey();
}
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