| /* |
| * EAP server/peer: EAP-pwd shared routines |
| * Copyright (c) 2010, Dan Harkins <dharkins@lounge.org> |
| * |
| * This software may be distributed under the terms of the BSD license. |
| * See README for more details. |
| */ |
| |
| #include "includes.h" |
| #include "common.h" |
| #include "utils/const_time.h" |
| #include "common/dragonfly.h" |
| #include "crypto/sha256.h" |
| #include "crypto/crypto.h" |
| #include "eap_defs.h" |
| #include "eap_pwd_common.h" |
| |
| #define MAX_ECC_PRIME_LEN 66 |
| |
| |
| /* The random function H(x) = HMAC-SHA256(0^32, x) */ |
| struct crypto_hash * eap_pwd_h_init(void) |
| { |
| u8 allzero[SHA256_MAC_LEN]; |
| os_memset(allzero, 0, SHA256_MAC_LEN); |
| return crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256, allzero, |
| SHA256_MAC_LEN); |
| } |
| |
| |
| void eap_pwd_h_update(struct crypto_hash *hash, const u8 *data, size_t len) |
| { |
| crypto_hash_update(hash, data, len); |
| } |
| |
| |
| void eap_pwd_h_final(struct crypto_hash *hash, u8 *digest) |
| { |
| size_t len = SHA256_MAC_LEN; |
| crypto_hash_finish(hash, digest, &len); |
| } |
| |
| |
| /* a counter-based KDF based on NIST SP800-108 */ |
| static int eap_pwd_kdf(const u8 *key, size_t keylen, const u8 *label, |
| size_t labellen, u8 *result, size_t resultbitlen) |
| { |
| struct crypto_hash *hash; |
| u8 digest[SHA256_MAC_LEN]; |
| u16 i, ctr, L; |
| size_t resultbytelen, len = 0, mdlen; |
| |
| resultbytelen = (resultbitlen + 7) / 8; |
| ctr = 0; |
| L = htons(resultbitlen); |
| while (len < resultbytelen) { |
| ctr++; |
| i = htons(ctr); |
| hash = crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256, |
| key, keylen); |
| if (hash == NULL) |
| return -1; |
| if (ctr > 1) |
| crypto_hash_update(hash, digest, SHA256_MAC_LEN); |
| crypto_hash_update(hash, (u8 *) &i, sizeof(u16)); |
| crypto_hash_update(hash, label, labellen); |
| crypto_hash_update(hash, (u8 *) &L, sizeof(u16)); |
| mdlen = SHA256_MAC_LEN; |
| if (crypto_hash_finish(hash, digest, &mdlen) < 0) |
| return -1; |
| if ((len + mdlen) > resultbytelen) |
| os_memcpy(result + len, digest, resultbytelen - len); |
| else |
| os_memcpy(result + len, digest, mdlen); |
| len += mdlen; |
| } |
| |
| /* since we're expanding to a bit length, mask off the excess */ |
| if (resultbitlen % 8) { |
| u8 mask = 0xff; |
| mask <<= (8 - (resultbitlen % 8)); |
| result[resultbytelen - 1] &= mask; |
| } |
| |
| return 0; |
| } |
| |
| |
| EAP_PWD_group * get_eap_pwd_group(u16 num) |
| { |
| EAP_PWD_group *grp; |
| |
| if (!dragonfly_suitable_group(num, 1)) { |
| wpa_printf(MSG_INFO, "EAP-pwd: unsuitable group %u", num); |
| return NULL; |
| } |
| grp = os_zalloc(sizeof(EAP_PWD_group)); |
| if (!grp) |
| return NULL; |
| grp->group = crypto_ec_init(num); |
| if (!grp->group) { |
| wpa_printf(MSG_INFO, "EAP-pwd: unable to create EC group"); |
| os_free(grp); |
| return NULL; |
| } |
| |
| grp->group_num = num; |
| wpa_printf(MSG_INFO, "EAP-pwd: provisioned group %d", num); |
| |
| return grp; |
| } |
| |
| |
| /* |
| * compute a "random" secret point on an elliptic curve based |
| * on the password and identities. |
| */ |
| int compute_password_element(EAP_PWD_group *grp, u16 num, |
| const u8 *password, size_t password_len, |
| const u8 *id_server, size_t id_server_len, |
| const u8 *id_peer, size_t id_peer_len, |
| const u8 *token) |
| { |
| struct crypto_bignum *qr = NULL, *qnr = NULL; |
| u8 qr_bin[MAX_ECC_PRIME_LEN]; |
| u8 qnr_bin[MAX_ECC_PRIME_LEN]; |
| u8 qr_or_qnr_bin[MAX_ECC_PRIME_LEN]; |
| u8 x_bin[MAX_ECC_PRIME_LEN]; |
| u8 prime_bin[MAX_ECC_PRIME_LEN]; |
| struct crypto_bignum *tmp2 = NULL; |
| struct crypto_hash *hash; |
| unsigned char pwe_digest[SHA256_MAC_LEN], *prfbuf = NULL, ctr; |
| int ret = 0, res; |
| u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_* |
| * mask */ |
| size_t primebytelen = 0, primebitlen; |
| struct crypto_bignum *x_candidate = NULL; |
| const struct crypto_bignum *prime; |
| u8 found_ctr = 0, is_odd = 0; |
| int cmp_prime; |
| unsigned int in_range; |
| |
| if (grp->pwe) |
| return -1; |
| |
| os_memset(x_bin, 0, sizeof(x_bin)); |
| |
| prime = crypto_ec_get_prime(grp->group); |
| primebitlen = crypto_ec_prime_len_bits(grp->group); |
| primebytelen = crypto_ec_prime_len(grp->group); |
| if (crypto_bignum_to_bin(prime, prime_bin, sizeof(prime_bin), |
| primebytelen) < 0) |
| return -1; |
| grp->pwe = crypto_ec_point_init(grp->group); |
| if (!grp->pwe) { |
| wpa_printf(MSG_INFO, "EAP-pwd: unable to create bignums"); |
| goto fail; |
| } |
| |
| if ((prfbuf = os_malloc(primebytelen)) == NULL) { |
| wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf " |
| "buffer"); |
| goto fail; |
| } |
| |
| /* get a random quadratic residue and nonresidue */ |
| if (dragonfly_get_random_qr_qnr(prime, &qr, &qnr) < 0 || |
| crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin), |
| primebytelen) < 0 || |
| crypto_bignum_to_bin(qnr, qnr_bin, sizeof(qnr_bin), |
| primebytelen) < 0) |
| goto fail; |
| |
| os_memset(prfbuf, 0, primebytelen); |
| ctr = 0; |
| |
| /* |
| * Run through the hunting-and-pecking loop 40 times to mask the time |
| * necessary to find PWE. The odds of PWE not being found in 40 loops is |
| * roughly 1 in 1 trillion. |
| */ |
| while (ctr < 40) { |
| ctr++; |
| |
| /* |
| * compute counter-mode password value and stretch to prime |
| * pwd-seed = H(token | peer-id | server-id | password | |
| * counter) |
| */ |
| hash = eap_pwd_h_init(); |
| if (hash == NULL) |
| goto fail; |
| eap_pwd_h_update(hash, token, sizeof(u32)); |
| eap_pwd_h_update(hash, id_peer, id_peer_len); |
| eap_pwd_h_update(hash, id_server, id_server_len); |
| eap_pwd_h_update(hash, password, password_len); |
| eap_pwd_h_update(hash, &ctr, sizeof(ctr)); |
| eap_pwd_h_final(hash, pwe_digest); |
| |
| is_odd = const_time_select_u8( |
| found, is_odd, pwe_digest[SHA256_MAC_LEN - 1] & 0x01); |
| if (eap_pwd_kdf(pwe_digest, SHA256_MAC_LEN, |
| (u8 *) "EAP-pwd Hunting And Pecking", |
| os_strlen("EAP-pwd Hunting And Pecking"), |
| prfbuf, primebitlen) < 0) |
| goto fail; |
| if (primebitlen % 8) |
| buf_shift_right(prfbuf, primebytelen, |
| 8 - primebitlen % 8); |
| cmp_prime = const_time_memcmp(prfbuf, prime_bin, primebytelen); |
| /* Create a const_time mask for selection based on prf result |
| * being smaller than prime. */ |
| in_range = const_time_fill_msb((unsigned int) cmp_prime); |
| /* The algorithm description would skip the next steps if |
| * cmp_prime >= 0, but go through them regardless to minimize |
| * externally observable differences in behavior. */ |
| |
| crypto_bignum_deinit(x_candidate, 1); |
| x_candidate = crypto_bignum_init_set(prfbuf, primebytelen); |
| if (!x_candidate) { |
| wpa_printf(MSG_INFO, |
| "EAP-pwd: unable to create x_candidate"); |
| goto fail; |
| } |
| |
| wpa_hexdump_key(MSG_DEBUG, "EAP-pwd: x_candidate", |
| prfbuf, primebytelen); |
| const_time_select_bin(found, x_bin, prfbuf, primebytelen, |
| x_bin); |
| |
| /* |
| * compute y^2 using the equation of the curve |
| * |
| * y^2 = x^3 + ax + b |
| */ |
| crypto_bignum_deinit(tmp2, 1); |
| tmp2 = crypto_ec_point_compute_y_sqr(grp->group, x_candidate); |
| if (!tmp2) |
| goto fail; |
| |
| res = dragonfly_is_quadratic_residue_blind(grp->group, qr_bin, |
| qnr_bin, tmp2); |
| if (res < 0) |
| goto fail; |
| found_ctr = const_time_select_u8(found, found_ctr, ctr); |
| /* found is 0 or 0xff here and res is 0 or 1. Bitwise OR of them |
| * (with res converted to 0/0xff and masked with prf being below |
| * prime) handles this in constant time. |
| */ |
| found |= (res & in_range) * 0xff; |
| } |
| if (found == 0) { |
| wpa_printf(MSG_INFO, |
| "EAP-pwd: unable to find random point on curve for group %d, something's fishy", |
| num); |
| goto fail; |
| } |
| |
| /* |
| * We know x_candidate is a quadratic residue so set it here. |
| */ |
| crypto_bignum_deinit(x_candidate, 1); |
| x_candidate = crypto_bignum_init_set(x_bin, primebytelen); |
| if (!x_candidate || |
| crypto_ec_point_solve_y_coord(grp->group, grp->pwe, x_candidate, |
| is_odd) != 0) { |
| wpa_printf(MSG_INFO, "EAP-pwd: Could not solve for y"); |
| goto fail; |
| } |
| |
| /* |
| * If there's a solution to the equation then the point must be on the |
| * curve so why check again explicitly? OpenSSL code says this is |
| * required by X9.62. We're not X9.62 but it can't hurt just to be sure. |
| */ |
| if (!crypto_ec_point_is_on_curve(grp->group, grp->pwe)) { |
| wpa_printf(MSG_INFO, "EAP-pwd: point is not on curve"); |
| goto fail; |
| } |
| |
| wpa_printf(MSG_DEBUG, "EAP-pwd: found a PWE in %02d tries", found_ctr); |
| |
| if (0) { |
| fail: |
| crypto_ec_point_deinit(grp->pwe, 1); |
| grp->pwe = NULL; |
| ret = 1; |
| } |
| /* cleanliness and order.... */ |
| crypto_bignum_deinit(x_candidate, 1); |
| crypto_bignum_deinit(tmp2, 1); |
| crypto_bignum_deinit(qr, 1); |
| crypto_bignum_deinit(qnr, 1); |
| bin_clear_free(prfbuf, primebytelen); |
| os_memset(qr_bin, 0, sizeof(qr_bin)); |
| os_memset(qnr_bin, 0, sizeof(qnr_bin)); |
| os_memset(qr_or_qnr_bin, 0, sizeof(qr_or_qnr_bin)); |
| os_memset(pwe_digest, 0, sizeof(pwe_digest)); |
| |
| return ret; |
| } |
| |
| |
| int compute_keys(EAP_PWD_group *grp, const struct crypto_bignum *k, |
| const struct crypto_bignum *peer_scalar, |
| const struct crypto_bignum *server_scalar, |
| const u8 *confirm_peer, const u8 *confirm_server, |
| const u32 *ciphersuite, u8 *msk, u8 *emsk, u8 *session_id) |
| { |
| struct crypto_hash *hash; |
| u8 mk[SHA256_MAC_LEN], *cruft; |
| u8 msk_emsk[EAP_MSK_LEN + EAP_EMSK_LEN]; |
| size_t prime_len, order_len; |
| |
| prime_len = crypto_ec_prime_len(grp->group); |
| order_len = crypto_ec_order_len(grp->group); |
| |
| cruft = os_malloc(prime_len); |
| if (!cruft) |
| return -1; |
| |
| /* |
| * first compute the session-id = TypeCode | H(ciphersuite | scal_p | |
| * scal_s) |
| */ |
| session_id[0] = EAP_TYPE_PWD; |
| hash = eap_pwd_h_init(); |
| if (hash == NULL) { |
| os_free(cruft); |
| return -1; |
| } |
| eap_pwd_h_update(hash, (const u8 *) ciphersuite, sizeof(u32)); |
| crypto_bignum_to_bin(peer_scalar, cruft, order_len, order_len); |
| eap_pwd_h_update(hash, cruft, order_len); |
| crypto_bignum_to_bin(server_scalar, cruft, order_len, order_len); |
| eap_pwd_h_update(hash, cruft, order_len); |
| eap_pwd_h_final(hash, &session_id[1]); |
| |
| /* then compute MK = H(k | confirm-peer | confirm-server) */ |
| hash = eap_pwd_h_init(); |
| if (hash == NULL) { |
| os_free(cruft); |
| return -1; |
| } |
| crypto_bignum_to_bin(k, cruft, prime_len, prime_len); |
| eap_pwd_h_update(hash, cruft, prime_len); |
| os_free(cruft); |
| eap_pwd_h_update(hash, confirm_peer, SHA256_MAC_LEN); |
| eap_pwd_h_update(hash, confirm_server, SHA256_MAC_LEN); |
| eap_pwd_h_final(hash, mk); |
| |
| /* stretch the mk with the session-id to get MSK | EMSK */ |
| if (eap_pwd_kdf(mk, SHA256_MAC_LEN, |
| session_id, SHA256_MAC_LEN + 1, |
| msk_emsk, (EAP_MSK_LEN + EAP_EMSK_LEN) * 8) < 0) { |
| return -1; |
| } |
| |
| os_memcpy(msk, msk_emsk, EAP_MSK_LEN); |
| os_memcpy(emsk, msk_emsk + EAP_MSK_LEN, EAP_EMSK_LEN); |
| |
| return 1; |
| } |
| |
| |
| static int eap_pwd_element_coord_ok(const struct crypto_bignum *prime, |
| const u8 *buf, size_t len) |
| { |
| struct crypto_bignum *val; |
| int ok = 1; |
| |
| val = crypto_bignum_init_set(buf, len); |
| if (!val || crypto_bignum_is_zero(val) || |
| crypto_bignum_cmp(val, prime) >= 0) |
| ok = 0; |
| crypto_bignum_deinit(val, 0); |
| return ok; |
| } |
| |
| |
| struct crypto_ec_point * eap_pwd_get_element(EAP_PWD_group *group, |
| const u8 *buf) |
| { |
| struct crypto_ec_point *element; |
| const struct crypto_bignum *prime; |
| size_t prime_len; |
| |
| prime = crypto_ec_get_prime(group->group); |
| prime_len = crypto_ec_prime_len(group->group); |
| |
| /* RFC 5931, 2.8.5.2.2: 0 < x,y < p */ |
| if (!eap_pwd_element_coord_ok(prime, buf, prime_len) || |
| !eap_pwd_element_coord_ok(prime, buf + prime_len, prime_len)) { |
| wpa_printf(MSG_INFO, "EAP-pwd: Invalid coordinate in element"); |
| return NULL; |
| } |
| |
| element = crypto_ec_point_from_bin(group->group, buf); |
| if (!element) { |
| wpa_printf(MSG_INFO, "EAP-pwd: EC point from element failed"); |
| return NULL; |
| } |
| |
| /* RFC 5931, 2.8.5.2.2: on curve and not the point at infinity */ |
| if (!crypto_ec_point_is_on_curve(group->group, element) || |
| crypto_ec_point_is_at_infinity(group->group, element)) { |
| wpa_printf(MSG_INFO, "EAP-pwd: Invalid element"); |
| goto fail; |
| } |
| |
| out: |
| return element; |
| fail: |
| crypto_ec_point_deinit(element, 0); |
| element = NULL; |
| goto out; |
| } |
| |
| |
| struct crypto_bignum * eap_pwd_get_scalar(EAP_PWD_group *group, const u8 *buf) |
| { |
| struct crypto_bignum *scalar; |
| const struct crypto_bignum *order; |
| size_t order_len; |
| |
| order = crypto_ec_get_order(group->group); |
| order_len = crypto_ec_order_len(group->group); |
| |
| /* RFC 5931, 2.8.5.2: 1 < scalar < r */ |
| scalar = crypto_bignum_init_set(buf, order_len); |
| if (!scalar || crypto_bignum_is_zero(scalar) || |
| crypto_bignum_is_one(scalar) || |
| crypto_bignum_cmp(scalar, order) >= 0) { |
| wpa_printf(MSG_INFO, "EAP-pwd: received scalar is invalid"); |
| crypto_bignum_deinit(scalar, 0); |
| scalar = NULL; |
| } |
| |
| return scalar; |
| } |
| |
| |
| int eap_pwd_get_rand_mask(EAP_PWD_group *group, struct crypto_bignum *_rand, |
| struct crypto_bignum *_mask, |
| struct crypto_bignum *scalar) |
| { |
| return dragonfly_generate_scalar(crypto_ec_get_order(group->group), |
| _rand, _mask, scalar); |
| } |