src/key.cpp

   1 // Copyright (c) 2009-2012 The Bitcoin developers
   2 // Distributed under the MIT/X11 software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include <map>
   6
   7 #include <openssl/ecdsa.h>
   8 #include <openssl/obj_mac.h>
   9
  10 #include "key.h"
  11
  12 // Generate a private key from just the secret parameter
  13 int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
  14 {
  15     int ok = 0;
  16     BN_CTX *ctx = NULL;
  17     EC_POINT *pub_key = NULL;
  18
  19     if (!eckey) return 0;
  20
  21     const EC_GROUP *group = EC_KEY_get0_group(eckey);
  22
  23     if ((ctx = BN_CTX_new()) == NULL)
  24         goto err;
  25
  26     pub_key = EC_POINT_new(group);
  27
  28     if (pub_key == NULL)
  29         goto err;
  30
  31     if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
  32         goto err;
  33
  34     EC_KEY_set_private_key(eckey,priv_key);
  35     EC_KEY_set_public_key(eckey,pub_key);
  36
  37     ok = 1;
  38
  39 err:
  40
  41     if (pub_key)
  42         EC_POINT_free(pub_key);
  43     if (ctx != NULL)
  44         BN_CTX_free(ctx);
  45
  46     return(ok);
  47 }
  48
  49 // Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
  50 // recid selects which key is recovered
  51 // if check is non-zero, additional checks are performed
  52 int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
  53 {
  54     if (!eckey) return 0;
  55
  56     int ret = 0;
  57     BN_CTX *ctx = NULL;
  58
  59     BIGNUM *x = NULL;
  60     BIGNUM *e = NULL;
  61     BIGNUM *order = NULL;
  62     BIGNUM *sor = NULL;
  63     BIGNUM *eor = NULL;
  64     BIGNUM *field = NULL;
  65     EC_POINT *R = NULL;
  66     EC_POINT *O = NULL;
  67     EC_POINT *Q = NULL;
  68     BIGNUM *rr = NULL;
  69     BIGNUM *zero = NULL;
  70     int n = 0;
  71     int i = recid / 2;
  72
  73     const EC_GROUP *group = EC_KEY_get0_group(eckey);
  74     if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
  75     BN_CTX_start(ctx);
  76     order = BN_CTX_get(ctx);
  77     if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
  78     x = BN_CTX_get(ctx);
  79     if (!BN_copy(x, order)) { ret=-1; goto err; }
  80     if (!BN_mul_word(x, i)) { ret=-1; goto err; }
  81     if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
  82     field = BN_CTX_get(ctx);
  83     if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
  84     if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
  85     if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
  86     if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
  87     if (check)
  88     {
  89         if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
  90         if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
  91         if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
  92     }
  93     if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
  94     n = EC_GROUP_get_degree(group);
  95     e = BN_CTX_get(ctx);
  96     if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
  97     if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
  98     zero = BN_CTX_get(ctx);
  99     if (!BN_zero(zero)) { ret=-1; goto err; }
 100     if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
 101     rr = BN_CTX_get(ctx);
 102     if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
 103     sor = BN_CTX_get(ctx);
 104     if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
 105     eor = BN_CTX_get(ctx);
 106     if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
 107     if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
 108     if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
 109
 110     ret = 1;
 111
 112 err:
 113     if (ctx) {
 114         BN_CTX_end(ctx);
 115         BN_CTX_free(ctx);
 116     }
 117     if (R != NULL) EC_POINT_free(R);
 118     if (O != NULL) EC_POINT_free(O);
 119     if (Q != NULL) EC_POINT_free(Q);
 120     return ret;
 121 }
 122
 123 void CKey::SetCompressedPubKey()
 124 {
 125     EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
 126     fCompressedPubKey = true;
 127 }
 128
 129 void CKey::Reset()
 130 {
 131     fCompressedPubKey = false;
 132     if (pkey != NULL)
 133         EC_KEY_free(pkey);
 134     pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
 135     if (pkey == NULL)
 136         throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
 137     fSet = false;
 138 }
 139
 140 CKey::CKey()
 141 {
 142     pkey = NULL;
 143     Reset();
 144 }
 145
 146 CKey::CKey(const CKey& b)
 147 {
 148     pkey = EC_KEY_dup(b.pkey);
 149     if (pkey == NULL)
 150         throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
 151     fSet = b.fSet;
 152 }
 153
 154 CKey& CKey::operator=(const CKey& b)
 155 {
 156     if (!EC_KEY_copy(pkey, b.pkey))
 157         throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
 158     fSet = b.fSet;
 159     return (*this);
 160 }
 161
 162 CKey::~CKey()
 163 {
 164     EC_KEY_free(pkey);
 165 }
 166
 167 bool CKey::IsNull() const
 168 {
 169     return !fSet;
 170 }
 171
 172 bool CKey::IsCompressed() const
 173 {
 174     return fCompressedPubKey;
 175 }
 176
 177 void CKey::MakeNewKey(bool fCompressed)
 178 {
 179     if (!EC_KEY_generate_key(pkey))
 180         throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
 181     if (fCompressed)
 182         SetCompressedPubKey();
 183     fSet = true;
 184 }
 185
 186 bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
 187 {
 188     const unsigned char* pbegin = &vchPrivKey[0];
 189     if (!d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
 190         return false;
 191     fSet = true;
 192     return true;
 193 }
 194
 195 bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
 196 {
 197     EC_KEY_free(pkey);
 198     pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
 199     if (pkey == NULL)
 200         throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
 201     if (vchSecret.size() != 32)
 202         throw key_error("CKey::SetSecret() : secret must be 32 bytes");
 203     BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
 204     if (bn == NULL)
 205         throw key_error("CKey::SetSecret() : BN_bin2bn failed");
 206     if (!EC_KEY_regenerate_key(pkey,bn))
 207     {
 208         BN_clear_free(bn);
 209         throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
 210     }
 211     BN_clear_free(bn);
 212     fSet = true;
 213     if (fCompressed || fCompressedPubKey)
 214         SetCompressedPubKey();
 215     return true;
 216 }
 217
 218 CSecret CKey::GetSecret(bool &fCompressed) const
 219 {
 220     CSecret vchRet;
 221     vchRet.resize(32);
 222     const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
 223     int nBytes = BN_num_bytes(bn);
 224     if (bn == NULL)
 225         throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
 226     int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
 227     if (n != nBytes)
 228         throw key_error("CKey::GetSecret(): BN_bn2bin failed");
 229     fCompressed = fCompressedPubKey;
 230     return vchRet;
 231 }
 232
 233 CPrivKey CKey::GetPrivKey() const
 234 {
 235     int nSize = i2d_ECPrivateKey(pkey, NULL);
 236     if (!nSize)
 237         throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
 238     CPrivKey vchPrivKey(nSize, 0);
 239     unsigned char* pbegin = &vchPrivKey[0];
 240     if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
 241         throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
 242     return vchPrivKey;
 243 }
 244
 245 bool CKey::SetPubKey(const CPubKey& vchPubKey)
 246 {
 247     const unsigned char* pbegin = &vchPubKey.vchPubKey[0];
 248     if (!o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
 249         return false;
 250     fSet = true;
 251     if (vchPubKey.vchPubKey.size() == 33)
 252         SetCompressedPubKey();
 253     return true;
 254 }
 255
 256 CPubKey CKey::GetPubKey() const
 257 {
 258     int nSize = i2o_ECPublicKey(pkey, NULL);
 259     if (!nSize)
 260         throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
 261     std::vector<unsigned char> vchPubKey(nSize, 0);
 262     unsigned char* pbegin = &vchPubKey[0];
 263     if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
 264         throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
 265     return CPubKey(vchPubKey);
 266 }
 267
 268 bool CKey::Sign(uint256 hash, std::vector<unsigned char>& vchSig)
 269 {
 270     unsigned int nSize = ECDSA_size(pkey);
 271     vchSig.resize(nSize); // Make sure it is big enough
 272     if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
 273     {
 274         vchSig.clear();
 275         return false;
 276     }
 277     vchSig.resize(nSize); // Shrink to fit actual size
 278     return true;
 279 }
 280
 281 // create a compact signature (65 bytes), which allows reconstructing the used public key
 282 // The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
 283 // The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
 284 //                  0x1D = second key with even y, 0x1E = second key with odd y
 285 bool CKey::SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
 286 {
 287     bool fOk = false;
 288     ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
 289     if (sig==NULL)
 290         return false;
 291     vchSig.clear();
 292     vchSig.resize(65,0);
 293     int nBitsR = BN_num_bits(sig->r);
 294     int nBitsS = BN_num_bits(sig->s);
 295     if (nBitsR <= 256 && nBitsS <= 256)
 296     {
 297         int nRecId = -1;
 298         for (int i=0; i<4; i++)
 299         {
 300             CKey keyRec;
 301             keyRec.fSet = true;
 302             if (fCompressedPubKey)
 303                 keyRec.SetCompressedPubKey();
 304             if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
 305                 if (keyRec.GetPubKey() == this->GetPubKey())
 306                 {
 307                     nRecId = i;
 308                     break;
 309                 }
 310         }
 311
 312         if (nRecId == -1)
 313             throw key_error("CKey::SignCompact() : unable to construct recoverable key");
 314
 315         vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
 316         BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
 317         BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
 318         fOk = true;
 319     }
 320     ECDSA_SIG_free(sig);
 321     return fOk;
 322 }
 323
 324 // reconstruct public key from a compact signature
 325 // This is only slightly more CPU intensive than just verifying it.
 326 // If this function succeeds, the recovered public key is guaranteed to be valid
 327 // (the signature is a valid signature of the given data for that key)
 328 bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
 329 {
 330     if (vchSig.size() != 65)
 331         return false;
 332     int nV = vchSig[0];
 333     if (nV<27 || nV>=35)
 334         return false;
 335     ECDSA_SIG *sig = ECDSA_SIG_new();
 336     BN_bin2bn(&vchSig[1],32,sig->r);
 337     BN_bin2bn(&vchSig[33],32,sig->s);
 338
 339     EC_KEY_free(pkey);
 340     pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
 341     if (nV >= 31)
 342     {
 343         SetCompressedPubKey();
 344         nV -= 4;
 345     }
 346     if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
 347     {
 348         fSet = true;
 349         ECDSA_SIG_free(sig);
 350         return true;
 351     }
 352     return false;
 353 }
 354
 355 bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
 356 {
 357     // -1 = error, 0 = bad sig, 1 = good
 358     if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
 359         return false;
 360
 361     return true;
 362 }
 363
 364 bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
 365 {
 366     CKey key;
 367     if (!key.SetCompactSignature(hash, vchSig))
 368         return false;
 369     if (GetPubKey() != key.GetPubKey())
 370         return false;
 371
 372     return true;
 373 }
 374
 375 bool CKey::IsValid()
 376 {
 377     if (!fSet)
 378         return false;
 379
 380     bool fCompr;
 381     CSecret secret = GetSecret(fCompr);
 382     CKey key2;
 383     key2.SetSecret(secret, fCompr);
 384     return GetPubKey() == key2.GetPubKey();
 385 }