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-rw-r--r--src/ecwrapper.cpp333
1 files changed, 333 insertions, 0 deletions
diff --git a/src/ecwrapper.cpp b/src/ecwrapper.cpp
new file mode 100644
index 0000000000..e5db670927
--- /dev/null
+++ b/src/ecwrapper.cpp
@@ -0,0 +1,333 @@
+// Copyright (c) 2009-2014 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 "ecwrapper.h"
+
+#include "serialize.h"
+#include "uint256.h"
+
+#include <openssl/bn.h>
+#include <openssl/ecdsa.h>
+#include <openssl/obj_mac.h>
+
+namespace {
+
+// 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;
+}
+
+} // anon namespace
+
+CECKey::CECKey() {
+ pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
+ assert(pkey != NULL);
+}
+
+CECKey::~CECKey() {
+ EC_KEY_free(pkey);
+}
+
+void CECKey::GetSecretBytes(unsigned char vch[32]) const {
+ const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
+ assert(bn);
+ int nBytes = BN_num_bytes(bn);
+ int n=BN_bn2bin(bn,&vch[32 - nBytes]);
+ assert(n == nBytes);
+ memset(vch, 0, 32 - nBytes);
+}
+
+void CECKey::SetSecretBytes(const unsigned char vch[32]) {
+ bool ret;
+ BIGNUM bn;
+ BN_init(&bn);
+ ret = BN_bin2bn(vch, 32, &bn) != NULL;
+ assert(ret);
+ ret = EC_KEY_regenerate_key(pkey, &bn) != 0;
+ assert(ret);
+ BN_clear_free(&bn);
+}
+
+int CECKey::GetPrivKeySize(bool fCompressed) {
+ EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
+ return i2d_ECPrivateKey(pkey, NULL);
+}
+int CECKey::GetPrivKey(unsigned char* privkey, bool fCompressed) {
+ EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
+ return i2d_ECPrivateKey(pkey, &privkey);
+}
+
+bool CECKey::SetPrivKey(const unsigned char* privkey, size_t size, bool fSkipCheck) {
+ if (d2i_ECPrivateKey(&pkey, &privkey, size)) {
+ if(fSkipCheck)
+ return true;
+
+ // d2i_ECPrivateKey returns true if parsing succeeds.
+ // This doesn't necessarily mean the key is valid.
+ if (EC_KEY_check_key(pkey))
+ return true;
+ }
+ return false;
+}
+
+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::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool lowS) {
+ vchSig.clear();
+ ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
+ if (sig == NULL)
+ return false;
+ BN_CTX *ctx = BN_CTX_new();
+ BN_CTX_start(ctx);
+ const EC_GROUP *group = EC_KEY_get0_group(pkey);
+ BIGNUM *order = BN_CTX_get(ctx);
+ BIGNUM *halforder = BN_CTX_get(ctx);
+ EC_GROUP_get_order(group, order, ctx);
+ BN_rshift1(halforder, order);
+ if (lowS && BN_cmp(sig->s, halforder) > 0) {
+ // enforce low S values, by negating the value (modulo the order) if above order/2.
+ BN_sub(sig->s, order, sig->s);
+ }
+ BN_CTX_end(ctx);
+ BN_CTX_free(ctx);
+ unsigned int nSize = ECDSA_size(pkey);
+ vchSig.resize(nSize); // Make sure it is big enough
+ unsigned char *pos = &vchSig[0];
+ nSize = i2d_ECDSA_SIG(sig, &pos);
+ ECDSA_SIG_free(sig);
+ vchSig.resize(nSize); // Shrink to fit actual size
+ return true;
+}
+
+bool CECKey::Verify(const 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 CECKey::SignCompact(const uint256 &hash, unsigned char *p64, int &rec) {
+ bool fOk = false;
+ ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
+ if (sig==NULL)
+ return false;
+ memset(p64, 0, 64);
+ int nBitsR = BN_num_bits(sig->r);
+ int nBitsS = BN_num_bits(sig->s);
+ if (nBitsR <= 256 && nBitsS <= 256) {
+ std::vector<unsigned char> pubkey;
+ GetPubKey(pubkey, true);
+ for (int i=0; i<4; i++) {
+ CECKey keyRec;
+ if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1) {
+ std::vector<unsigned char> pubkeyRec;
+ keyRec.GetPubKey(pubkeyRec, true);
+ if (pubkeyRec == pubkey) {
+ rec = i;
+ fOk = true;
+ break;
+ }
+ }
+ }
+ assert(fOk);
+ BN_bn2bin(sig->r,&p64[32-(nBitsR+7)/8]);
+ BN_bn2bin(sig->s,&p64[64-(nBitsS+7)/8]);
+ }
+ ECDSA_SIG_free(sig);
+ return fOk;
+}
+
+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::TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32])
+{
+ bool ret = true;
+ BN_CTX *ctx = BN_CTX_new();
+ BN_CTX_start(ctx);
+ BIGNUM *bnSecret = BN_CTX_get(ctx);
+ BIGNUM *bnTweak = BN_CTX_get(ctx);
+ BIGNUM *bnOrder = BN_CTX_get(ctx);
+ EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_secp256k1);
+ 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
+ BN_bin2bn(vchSecretIn, 32, bnSecret);
+ BN_add(bnSecret, bnSecret, bnTweak);
+ BN_nnmod(bnSecret, bnSecret, bnOrder, ctx);
+ if (BN_is_zero(bnSecret))
+ ret = false; // ridiculously unlikely
+ int nBits = BN_num_bits(bnSecret);
+ memset(vchSecretOut, 0, 32);
+ BN_bn2bin(bnSecret, &vchSecretOut[32-(nBits+7)/8]);
+ EC_GROUP_free(group);
+ BN_CTX_end(ctx);
+ BN_CTX_free(ctx);
+ 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;
+}