| 1 | /*
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| 2 | * Copyright 2002-2017 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <string.h>
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| 11 | #include <openssl/err.h>
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| 12 | #include <openssl/obj_mac.h>
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| 13 | #include <openssl/bn.h>
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| 14 | #include <openssl/rand.h>
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| 15 | #include <openssl/ec.h>
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| 16 | #include "ec_lcl.h"
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| 17 |
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| 18 | int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
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| 19 | unsigned char *sig, unsigned int *siglen,
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| 20 | const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
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| 21 | {
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| 22 | ECDSA_SIG *s;
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| 23 | RAND_seed(dgst, dlen);
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| 24 | s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
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| 25 | if (s == NULL) {
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| 26 | *siglen = 0;
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| 27 | return 0;
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| 28 | }
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| 29 | *siglen = i2d_ECDSA_SIG(s, &sig);
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| 30 | ECDSA_SIG_free(s);
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| 31 | return 1;
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| 32 | }
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| 33 |
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| 34 | static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
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| 35 | BIGNUM **kinvp, BIGNUM **rp,
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| 36 | const unsigned char *dgst, int dlen)
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| 37 | {
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| 38 | BN_CTX *ctx = NULL;
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| 39 | BIGNUM *k = NULL, *r = NULL, *X = NULL;
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| 40 | const BIGNUM *order;
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| 41 | EC_POINT *tmp_point = NULL;
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| 42 | const EC_GROUP *group;
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| 43 | int ret = 0;
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| 44 | int order_bits;
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| 45 |
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| 46 | if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
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| 47 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
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| 48 | return 0;
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| 49 | }
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| 50 |
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| 51 | if (!EC_KEY_can_sign(eckey)) {
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| 52 | ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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| 53 | return 0;
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| 54 | }
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| 55 |
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| 56 | if (ctx_in == NULL) {
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| 57 | if ((ctx = BN_CTX_new()) == NULL) {
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| 58 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
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| 59 | return 0;
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| 60 | }
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| 61 | } else
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| 62 | ctx = ctx_in;
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| 63 |
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| 64 | k = BN_new(); /* this value is later returned in *kinvp */
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| 65 | r = BN_new(); /* this value is later returned in *rp */
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| 66 | X = BN_new();
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| 67 | if (k == NULL || r == NULL || X == NULL) {
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| 68 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
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| 69 | goto err;
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| 70 | }
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| 71 | if ((tmp_point = EC_POINT_new(group)) == NULL) {
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| 72 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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| 73 | goto err;
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| 74 | }
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| 75 | order = EC_GROUP_get0_order(group);
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| 76 | if (order == NULL) {
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| 77 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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| 78 | goto err;
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| 79 | }
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| 80 |
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| 81 | /* Preallocate space */
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| 82 | order_bits = BN_num_bits(order);
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| 83 | if (!BN_set_bit(k, order_bits)
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| 84 | || !BN_set_bit(r, order_bits)
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| 85 | || !BN_set_bit(X, order_bits))
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| 86 | goto err;
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| 87 |
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| 88 | do {
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| 89 | /* get random k */
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| 90 | do
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| 91 | if (dgst != NULL) {
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| 92 | if (!BN_generate_dsa_nonce
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| 93 | (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
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| 94 | ctx)) {
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| 95 | ECerr(EC_F_ECDSA_SIGN_SETUP,
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| 96 | EC_R_RANDOM_NUMBER_GENERATION_FAILED);
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| 97 | goto err;
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| 98 | }
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| 99 | } else {
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| 100 | if (!BN_rand_range(k, order)) {
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| 101 | ECerr(EC_F_ECDSA_SIGN_SETUP,
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| 102 | EC_R_RANDOM_NUMBER_GENERATION_FAILED);
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| 103 | goto err;
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| 104 | }
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| 105 | }
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| 106 | while (BN_is_zero(k));
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| 107 |
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| 108 | /*
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| 109 | * We do not want timing information to leak the length of k, so we
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| 110 | * compute G*k using an equivalent scalar of fixed bit-length.
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| 111 | *
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| 112 | * We unconditionally perform both of these additions to prevent a
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| 113 | * small timing information leakage. We then choose the sum that is
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| 114 | * one bit longer than the order. This guarantees the code
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| 115 | * path used in the constant time implementations elsewhere.
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| 116 | *
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| 117 | * TODO: revisit the BN_copy aiming for a memory access agnostic
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| 118 | * conditional copy.
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| 119 | */
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| 120 | if (!BN_add(r, k, order)
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| 121 | || !BN_add(X, r, order)
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| 122 | || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
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| 123 | goto err;
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| 124 |
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| 125 | /* compute r the x-coordinate of generator * k */
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| 126 | if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
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| 127 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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| 128 | goto err;
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| 129 | }
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| 130 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
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| 131 | NID_X9_62_prime_field) {
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| 132 | if (!EC_POINT_get_affine_coordinates_GFp
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| 133 | (group, tmp_point, X, NULL, ctx)) {
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| 134 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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| 135 | goto err;
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| 136 | }
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| 137 | }
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| 138 | #ifndef OPENSSL_NO_EC2M
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| 139 | else { /* NID_X9_62_characteristic_two_field */
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| 140 |
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| 141 | if (!EC_POINT_get_affine_coordinates_GF2m(group,
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| 142 | tmp_point, X, NULL,
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| 143 | ctx)) {
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| 144 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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| 145 | goto err;
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| 146 | }
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| 147 | }
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| 148 | #endif
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| 149 | if (!BN_nnmod(r, X, order, ctx)) {
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| 150 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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| 151 | goto err;
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| 152 | }
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| 153 | }
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| 154 | while (BN_is_zero(r));
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| 155 |
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| 156 | /* compute the inverse of k */
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| 157 | if (EC_GROUP_get_mont_data(group) != NULL) {
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| 158 | /*
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| 159 | * We want inverse in constant time, therefore we utilize the fact
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| 160 | * order must be prime and use Fermats Little Theorem instead.
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| 161 | */
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| 162 | if (!BN_set_word(X, 2)) {
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| 163 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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| 164 | goto err;
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| 165 | }
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| 166 | if (!BN_mod_sub(X, order, X, order, ctx)) {
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| 167 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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| 168 | goto err;
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| 169 | }
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| 170 | BN_set_flags(X, BN_FLG_CONSTTIME);
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| 171 | if (!BN_mod_exp_mont_consttime
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| 172 | (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
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| 173 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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| 174 | goto err;
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| 175 | }
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| 176 | } else {
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| 177 | if (!BN_mod_inverse(k, k, order, ctx)) {
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| 178 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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| 179 | goto err;
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| 180 | }
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| 181 | }
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| 182 |
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| 183 | /* clear old values if necessary */
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| 184 | BN_clear_free(*rp);
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| 185 | BN_clear_free(*kinvp);
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| 186 | /* save the pre-computed values */
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| 187 | *rp = r;
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| 188 | *kinvp = k;
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| 189 | ret = 1;
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| 190 | err:
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| 191 | if (!ret) {
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| 192 | BN_clear_free(k);
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| 193 | BN_clear_free(r);
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| 194 | }
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| 195 | if (ctx != ctx_in)
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| 196 | BN_CTX_free(ctx);
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| 197 | EC_POINT_free(tmp_point);
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| 198 | BN_clear_free(X);
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| 199 | return (ret);
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| 200 | }
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| 201 |
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| 202 | int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
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| 203 | BIGNUM **rp)
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| 204 | {
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| 205 | return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
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| 206 | }
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| 207 |
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| 208 | ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
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| 209 | const BIGNUM *in_kinv, const BIGNUM *in_r,
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| 210 | EC_KEY *eckey)
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| 211 | {
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| 212 | int ok = 0, i;
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| 213 | BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL;
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| 214 | const BIGNUM *order, *ckinv;
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| 215 | BN_CTX *ctx = NULL;
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| 216 | const EC_GROUP *group;
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| 217 | ECDSA_SIG *ret;
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| 218 | const BIGNUM *priv_key;
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| 219 |
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| 220 | group = EC_KEY_get0_group(eckey);
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| 221 | priv_key = EC_KEY_get0_private_key(eckey);
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| 222 |
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| 223 | if (group == NULL || priv_key == NULL) {
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| 224 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
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| 225 | return NULL;
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| 226 | }
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| 227 |
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| 228 | if (!EC_KEY_can_sign(eckey)) {
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| 229 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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| 230 | return NULL;
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| 231 | }
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| 232 |
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| 233 | ret = ECDSA_SIG_new();
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| 234 | if (ret == NULL) {
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| 235 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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| 236 | return NULL;
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| 237 | }
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| 238 | ret->r = BN_new();
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| 239 | ret->s = BN_new();
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| 240 | if (ret->r == NULL || ret->s == NULL) {
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| 241 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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| 242 | goto err;
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| 243 | }
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| 244 | s = ret->s;
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| 245 |
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| 246 | if ((ctx = BN_CTX_new()) == NULL ||
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| 247 | (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
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| 248 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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| 249 | goto err;
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| 250 | }
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| 251 |
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| 252 | order = EC_GROUP_get0_order(group);
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| 253 | if (order == NULL) {
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| 254 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
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| 255 | goto err;
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| 256 | }
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| 257 | i = BN_num_bits(order);
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| 258 | /*
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| 259 | * Need to truncate digest if it is too long: first truncate whole bytes.
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| 260 | */
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| 261 | if (8 * dgst_len > i)
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| 262 | dgst_len = (i + 7) / 8;
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| 263 | if (!BN_bin2bn(dgst, dgst_len, m)) {
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| 264 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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| 265 | goto err;
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| 266 | }
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| 267 | /* If still too long truncate remaining bits with a shift */
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| 268 | if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
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| 269 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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| 270 | goto err;
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| 271 | }
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| 272 | do {
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| 273 | if (in_kinv == NULL || in_r == NULL) {
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| 274 | if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
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| 275 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
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| 276 | goto err;
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| 277 | }
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| 278 | ckinv = kinv;
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| 279 | } else {
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| 280 | ckinv = in_kinv;
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| 281 | if (BN_copy(ret->r, in_r) == NULL) {
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| 282 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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| 283 | goto err;
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| 284 | }
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| 285 | }
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| 286 |
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| 287 | if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
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| 288 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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| 289 | goto err;
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| 290 | }
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| 291 | if (!BN_mod_add_quick(s, tmp, m, order)) {
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| 292 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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| 293 | goto err;
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| 294 | }
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| 295 | if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
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| 296 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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| 297 | goto err;
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| 298 | }
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| 299 | if (BN_is_zero(s)) {
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| 300 | /*
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| 301 | * if kinv and r have been supplied by the caller don't to
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| 302 | * generate new kinv and r values
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| 303 | */
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| 304 | if (in_kinv != NULL && in_r != NULL) {
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| 305 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
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| 306 | goto err;
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| 307 | }
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| 308 | } else
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| 309 | /* s != 0 => we have a valid signature */
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| 310 | break;
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| 311 | }
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| 312 | while (1);
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| 313 |
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| 314 | ok = 1;
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| 315 | err:
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| 316 | if (!ok) {
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| 317 | ECDSA_SIG_free(ret);
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| 318 | ret = NULL;
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| 319 | }
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| 320 | BN_CTX_free(ctx);
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| 321 | BN_clear_free(m);
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| 322 | BN_clear_free(tmp);
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| 323 | BN_clear_free(kinv);
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| 324 | return ret;
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| 325 | }
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| 326 |
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| 327 | /*-
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| 328 | * returns
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| 329 | * 1: correct signature
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| 330 | * 0: incorrect signature
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| 331 | * -1: error
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| 332 | */
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| 333 | int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
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| 334 | const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
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| 335 | {
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| 336 | ECDSA_SIG *s;
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| 337 | const unsigned char *p = sigbuf;
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| 338 | unsigned char *der = NULL;
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| 339 | int derlen = -1;
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| 340 | int ret = -1;
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| 341 |
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| 342 | s = ECDSA_SIG_new();
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| 343 | if (s == NULL)
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| 344 | return (ret);
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| 345 | if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
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| 346 | goto err;
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| 347 | /* Ensure signature uses DER and doesn't have trailing garbage */
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| 348 | derlen = i2d_ECDSA_SIG(s, &der);
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| 349 | if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
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| 350 | goto err;
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| 351 | ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
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| 352 | err:
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| 353 | OPENSSL_clear_free(der, derlen);
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| 354 | ECDSA_SIG_free(s);
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| 355 | return (ret);
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| 356 | }
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| 357 |
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| 358 | int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
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| 359 | const ECDSA_SIG *sig, EC_KEY *eckey)
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| 360 | {
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| 361 | int ret = -1, i;
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| 362 | BN_CTX *ctx;
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| 363 | const BIGNUM *order;
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| 364 | BIGNUM *u1, *u2, *m, *X;
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| 365 | EC_POINT *point = NULL;
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| 366 | const EC_GROUP *group;
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| 367 | const EC_POINT *pub_key;
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| 368 |
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| 369 | /* check input values */
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| 370 | if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
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| 371 | (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
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| 372 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
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| 373 | return -1;
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| 374 | }
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| 375 |
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| 376 | if (!EC_KEY_can_sign(eckey)) {
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| 377 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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| 378 | return -1;
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| 379 | }
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| 380 |
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| 381 | ctx = BN_CTX_new();
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| 382 | if (ctx == NULL) {
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| 383 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
|
|---|
| 384 | return -1;
|
|---|
| 385 | }
|
|---|
| 386 | BN_CTX_start(ctx);
|
|---|
| 387 | u1 = BN_CTX_get(ctx);
|
|---|
| 388 | u2 = BN_CTX_get(ctx);
|
|---|
| 389 | m = BN_CTX_get(ctx);
|
|---|
| 390 | X = BN_CTX_get(ctx);
|
|---|
| 391 | if (X == NULL) {
|
|---|
| 392 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 393 | goto err;
|
|---|
| 394 | }
|
|---|
| 395 |
|
|---|
| 396 | order = EC_GROUP_get0_order(group);
|
|---|
| 397 | if (order == NULL) {
|
|---|
| 398 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
|---|
| 399 | goto err;
|
|---|
| 400 | }
|
|---|
| 401 |
|
|---|
| 402 | if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
|
|---|
| 403 | BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
|
|---|
| 404 | BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
|
|---|
| 405 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
|
|---|
| 406 | ret = 0; /* signature is invalid */
|
|---|
| 407 | goto err;
|
|---|
| 408 | }
|
|---|
| 409 | /* calculate tmp1 = inv(S) mod order */
|
|---|
| 410 | if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
|
|---|
| 411 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 412 | goto err;
|
|---|
| 413 | }
|
|---|
| 414 | /* digest -> m */
|
|---|
| 415 | i = BN_num_bits(order);
|
|---|
| 416 | /*
|
|---|
| 417 | * Need to truncate digest if it is too long: first truncate whole bytes.
|
|---|
| 418 | */
|
|---|
| 419 | if (8 * dgst_len > i)
|
|---|
| 420 | dgst_len = (i + 7) / 8;
|
|---|
| 421 | if (!BN_bin2bn(dgst, dgst_len, m)) {
|
|---|
| 422 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 423 | goto err;
|
|---|
| 424 | }
|
|---|
| 425 | /* If still too long truncate remaining bits with a shift */
|
|---|
| 426 | if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
|
|---|
| 427 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 428 | goto err;
|
|---|
| 429 | }
|
|---|
| 430 | /* u1 = m * tmp mod order */
|
|---|
| 431 | if (!BN_mod_mul(u1, m, u2, order, ctx)) {
|
|---|
| 432 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 433 | goto err;
|
|---|
| 434 | }
|
|---|
| 435 | /* u2 = r * w mod q */
|
|---|
| 436 | if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
|
|---|
| 437 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 438 | goto err;
|
|---|
| 439 | }
|
|---|
| 440 |
|
|---|
| 441 | if ((point = EC_POINT_new(group)) == NULL) {
|
|---|
| 442 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
|
|---|
| 443 | goto err;
|
|---|
| 444 | }
|
|---|
| 445 | if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
|
|---|
| 446 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
|---|
| 447 | goto err;
|
|---|
| 448 | }
|
|---|
| 449 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
|
|---|
| 450 | NID_X9_62_prime_field) {
|
|---|
| 451 | if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
|
|---|
| 452 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
|---|
| 453 | goto err;
|
|---|
| 454 | }
|
|---|
| 455 | }
|
|---|
| 456 | #ifndef OPENSSL_NO_EC2M
|
|---|
| 457 | else { /* NID_X9_62_characteristic_two_field */
|
|---|
| 458 |
|
|---|
| 459 | if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
|
|---|
| 460 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
|---|
| 461 | goto err;
|
|---|
| 462 | }
|
|---|
| 463 | }
|
|---|
| 464 | #endif
|
|---|
| 465 | if (!BN_nnmod(u1, X, order, ctx)) {
|
|---|
| 466 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
|---|
| 467 | goto err;
|
|---|
| 468 | }
|
|---|
| 469 | /* if the signature is correct u1 is equal to sig->r */
|
|---|
| 470 | ret = (BN_ucmp(u1, sig->r) == 0);
|
|---|
| 471 | err:
|
|---|
| 472 | BN_CTX_end(ctx);
|
|---|
| 473 | BN_CTX_free(ctx);
|
|---|
| 474 | EC_POINT_free(point);
|
|---|
| 475 | return ret;
|
|---|
| 476 | }
|
|---|
