| // SPDX-License-Identifier: BSD-2-Clause |
| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| */ |
| |
| #include "tomcrypt_private.h" |
| |
| #ifdef LTC_MECC |
| |
| /** |
| @file ecc_verify_hash.c |
| ECC Crypto, Tom St Denis |
| */ |
| |
| /** |
| Verify an ECC signature in RFC7518 format |
| @param sig The signature to verify |
| @param siglen The length of the signature (octets) |
| @param hash The hash (message digest) that was signed |
| @param hashlen The length of the hash (octets) |
| @param sigformat The format of the signature (ecc_signature_type) |
| @param stat Result of signature, 1==valid, 0==invalid |
| @param key The corresponding public ECC key |
| @return CRYPT_OK if successful (even if the signature is not valid) |
| */ |
| int ecc_verify_hash_ex(const unsigned char *sig, unsigned long siglen, |
| const unsigned char *hash, unsigned long hashlen, |
| ecc_signature_type sigformat, int *stat, const ecc_key *key) |
| { |
| ecc_point *mG = NULL, *mQ = NULL; |
| void *r, *s, *v, *w, *u1, *u2, *e, *p, *m, *a, *a_plus3; |
| void *mu = NULL, *ma = NULL; |
| void *mp = NULL; |
| int err; |
| unsigned long pbits, pbytes, i, shift_right; |
| unsigned char ch, buf[MAXBLOCKSIZE]; |
| |
| LTC_ARGCHK(sig != NULL); |
| LTC_ARGCHK(hash != NULL); |
| LTC_ARGCHK(stat != NULL); |
| LTC_ARGCHK(key != NULL); |
| |
| /* default to invalid signature */ |
| *stat = 0; |
| |
| /* allocate ints */ |
| if ((err = mp_init_multi(&r, &s, &v, &w, &u1, &u2, &e, &a_plus3, NULL)) != CRYPT_OK) { |
| return err; |
| } |
| |
| p = key->dp.order; |
| m = key->dp.prime; |
| a = key->dp.A; |
| if ((err = mp_add_d(a, 3, a_plus3)) != CRYPT_OK) { |
| goto error; |
| } |
| |
| /* allocate points */ |
| mG = ltc_ecc_new_point(); |
| mQ = ltc_ecc_new_point(); |
| if (mQ == NULL || mG == NULL) { |
| err = CRYPT_MEM; |
| goto error; |
| } |
| |
| if (sigformat == LTC_ECCSIG_ANSIX962) { |
| /* ANSI X9.62 format - ASN.1 encoded SEQUENCE{ INTEGER(r), INTEGER(s) } */ |
| if ((err = der_decode_sequence_multi_ex(sig, siglen, LTC_DER_SEQ_SEQUENCE | LTC_DER_SEQ_STRICT, |
| LTC_ASN1_INTEGER, 1UL, r, |
| LTC_ASN1_INTEGER, 1UL, s, |
| LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { goto error; } |
| } |
| else if (sigformat == LTC_ECCSIG_RFC7518) { |
| /* RFC7518 format - raw (r,s) */ |
| i = mp_unsigned_bin_size(key->dp.order); |
| if (siglen != (2 * i)) { |
| err = CRYPT_INVALID_PACKET; |
| goto error; |
| } |
| if ((err = mp_read_unsigned_bin(r, (unsigned char *)sig, i)) != CRYPT_OK) { goto error; } |
| if ((err = mp_read_unsigned_bin(s, (unsigned char *)sig+i, i)) != CRYPT_OK) { goto error; } |
| } |
| else if (sigformat == LTC_ECCSIG_ETH27) { |
| /* Ethereum (v,r,s) format */ |
| if (pk_oid_cmp_with_ulong("1.3.132.0.10", key->dp.oid, key->dp.oidlen) != CRYPT_OK) { |
| /* Only valid for secp256k1 - OID 1.3.132.0.10 */ |
| err = CRYPT_ERROR; goto error; |
| } |
| if (siglen != 65) { /* Only secp256k1 curves use this format, so must be 65 bytes long */ |
| err = CRYPT_INVALID_PACKET; |
| goto error; |
| } |
| if ((err = mp_read_unsigned_bin(r, (unsigned char *)sig, 32)) != CRYPT_OK) { goto error; } |
| if ((err = mp_read_unsigned_bin(s, (unsigned char *)sig+32, 32)) != CRYPT_OK) { goto error; } |
| } |
| #ifdef LTC_SSH |
| else if (sigformat == LTC_ECCSIG_RFC5656) { |
| char name[64], name2[64]; |
| unsigned long namelen = sizeof(name2); |
| |
| /* Decode as SSH data sequence, per RFC4251 */ |
| if ((err = ssh_decode_sequence_multi(sig, siglen, |
| LTC_SSHDATA_STRING, name, 64, |
| LTC_SSHDATA_MPINT, r, |
| LTC_SSHDATA_MPINT, s, |
| LTC_SSHDATA_EOL, NULL)) != CRYPT_OK) { goto error; } |
| |
| |
| /* Check curve matches identifier string */ |
| if ((err = ecc_ssh_ecdsa_encode_name(name2, &namelen, key)) != CRYPT_OK) { goto error; } |
| if (XSTRCMP(name,name2) != 0) { |
| err = CRYPT_INVALID_ARG; |
| goto error; |
| } |
| } |
| #endif |
| else { |
| /* Unknown signature format */ |
| err = CRYPT_ERROR; |
| goto error; |
| } |
| |
| /* check for zero */ |
| if (mp_cmp_d(r, 0) != LTC_MP_GT || mp_cmp_d(s, 0) != LTC_MP_GT || |
| mp_cmp(r, p) != LTC_MP_LT || mp_cmp(s, p) != LTC_MP_LT) { |
| err = CRYPT_INVALID_PACKET; |
| goto error; |
| } |
| |
| /* read hash - truncate if needed */ |
| pbits = mp_count_bits(p); |
| pbytes = (pbits+7) >> 3; |
| if (pbits > hashlen*8) { |
| if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; } |
| } |
| else if (pbits % 8 == 0) { |
| if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, pbytes)) != CRYPT_OK) { goto error; } |
| } |
| else { |
| shift_right = 8 - pbits % 8; |
| for (i=0, ch=0; i<pbytes; i++) { |
| buf[i] = ch; |
| ch = (hash[i] << (8-shift_right)); |
| buf[i] = buf[i] ^ (hash[i] >> shift_right); |
| } |
| if ((err = mp_read_unsigned_bin(e, (unsigned char *)buf, pbytes)) != CRYPT_OK) { goto error; } |
| } |
| |
| /* w = s^-1 mod n */ |
| if ((err = mp_invmod(s, p, w)) != CRYPT_OK) { goto error; } |
| |
| /* u1 = ew */ |
| if ((err = mp_mulmod(e, w, p, u1)) != CRYPT_OK) { goto error; } |
| |
| /* u2 = rw */ |
| if ((err = mp_mulmod(r, w, p, u2)) != CRYPT_OK) { goto error; } |
| |
| /* find mG and mQ */ |
| if ((err = ltc_ecc_copy_point(&key->dp.base, mG)) != CRYPT_OK) { goto error; } |
| if ((err = ltc_ecc_copy_point(&key->pubkey, mQ)) != CRYPT_OK) { goto error; } |
| |
| /* find the montgomery mp */ |
| if ((err = mp_montgomery_setup(m, &mp)) != CRYPT_OK) { goto error; } |
| |
| /* for curves with a == -3 keep ma == NULL */ |
| if (mp_cmp(a_plus3, m) != LTC_MP_EQ) { |
| if ((err = mp_init_multi(&mu, &ma, NULL)) != CRYPT_OK) { goto error; } |
| if ((err = mp_montgomery_normalization(mu, m)) != CRYPT_OK) { goto error; } |
| if ((err = mp_mulmod(a, mu, m, ma)) != CRYPT_OK) { goto error; } |
| } |
| |
| /* compute u1*mG + u2*mQ = mG */ |
| if (ltc_mp.ecc_mul2add == NULL) { |
| if ((err = ltc_mp.ecc_ptmul(u1, mG, mG, a, m, 0)) != CRYPT_OK) { goto error; } |
| if ((err = ltc_mp.ecc_ptmul(u2, mQ, mQ, a, m, 0)) != CRYPT_OK) { goto error; } |
| |
| /* add them */ |
| if ((err = ltc_mp.ecc_ptadd(mQ, mG, mG, ma, m, mp)) != CRYPT_OK) { goto error; } |
| |
| /* reduce */ |
| if ((err = ltc_mp.ecc_map(mG, m, mp)) != CRYPT_OK) { goto error; } |
| } else { |
| /* use Shamir's trick to compute u1*mG + u2*mQ using half of the doubles */ |
| if ((err = ltc_mp.ecc_mul2add(mG, u1, mQ, u2, mG, ma, m)) != CRYPT_OK) { goto error; } |
| } |
| |
| /* v = X_x1 mod n */ |
| if ((err = mp_mod(mG->x, p, v)) != CRYPT_OK) { goto error; } |
| |
| /* does v == r */ |
| if (mp_cmp(v, r) == LTC_MP_EQ) { |
| *stat = 1; |
| } |
| |
| /* clear up and return */ |
| err = CRYPT_OK; |
| error: |
| if (mG != NULL) ltc_ecc_del_point(mG); |
| if (mQ != NULL) ltc_ecc_del_point(mQ); |
| if (mu != NULL) mp_clear(mu); |
| if (ma != NULL) mp_clear(ma); |
| mp_clear_multi(r, s, v, w, u1, u2, e, a_plus3, NULL); |
| if (mp != NULL) mp_montgomery_free(mp); |
| return err; |
| } |
| |
| #endif |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |
