int
compute_keys (pwd_session_t *sess, uint8_t *peer_confirm,
uint8_t *msk, uint8_t *emsk)
{
HMAC_CTX ctx;
uint8_t mk[SHA256_DIGEST_LENGTH], *cruft;
uint8_t session_id[SHA256_DIGEST_LENGTH + 1];
uint8_t msk_emsk[128]; /* 64 each */
int offset;
if ((cruft = talloc_array(sess, uint8_t, BN_num_bytes(sess->prime))) == NULL) {
DEBUG2("pwd: unable to allocate space to compute keys");
return -1;
}
/*
* first compute the session-id = TypeCode | H(ciphersuite | scal_p |
* scal_s)
*/
session_id[0] = PW_EAP_PWD;
H_Init(&ctx);
H_Update(&ctx, (uint8_t *)&sess->ciphersuite, sizeof(sess->ciphersuite));
offset = BN_num_bytes(sess->order) - BN_num_bytes(sess->peer_scalar);
memset(cruft, 0, BN_num_bytes(sess->prime));
BN_bn2bin(sess->peer_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->order));
offset = BN_num_bytes(sess->order) - BN_num_bytes(sess->my_scalar);
memset(cruft, 0, BN_num_bytes(sess->prime));
BN_bn2bin(sess->my_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->order));
H_Final(&ctx, (uint8_t *)&session_id[1]);
/* then compute MK = H(k | commit-peer | commit-server) */
H_Init(&ctx);
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->prime) - BN_num_bytes(sess->k);
BN_bn2bin(sess->k, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
H_Update(&ctx, peer_confirm, SHA256_DIGEST_LENGTH);
H_Update(&ctx, sess->my_confirm, SHA256_DIGEST_LENGTH);
H_Final(&ctx, mk);
/* stretch the mk with the session-id to get MSK | EMSK */
eap_pwd_kdf(mk, SHA256_DIGEST_LENGTH,
(const char *)session_id, SHA256_DIGEST_LENGTH+1,
msk_emsk, 1024); /* it's bits, ((64 + 64) * 8) */
memcpy(msk, msk_emsk, 64);
memcpy(emsk, msk_emsk + 64, 64);
talloc_free(cruft);
return 0;
}
int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, BIGNUM *k,
BIGNUM *peer_scalar, BIGNUM *server_scalar,
u8 *commit_peer, u8 *commit_server,
u32 *ciphersuite, u8 *msk, u8 *emsk)
{
HMAC_CTX ctx;
u8 mk[SHA256_DIGEST_LENGTH], *cruft;
u8 session_id[SHA256_DIGEST_LENGTH + 1];
u8 msk_emsk[EAP_MSK_LEN + EAP_EMSK_LEN];
int offset;
if ((cruft = os_malloc(BN_num_bytes(grp->prime))) == NULL)
return -1;
/*
* first compute the session-id = TypeCode | H(ciphersuite | scal_p |
* scal_s)
*/
session_id[0] = EAP_TYPE_PWD;
H_Init(&ctx);
H_Update(&ctx, (u8 *)ciphersuite, sizeof(u32));
offset = BN_num_bytes(grp->order) - BN_num_bytes(peer_scalar);
os_memset(cruft, 0, BN_num_bytes(grp->prime));
BN_bn2bin(peer_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(grp->order));
offset = BN_num_bytes(grp->order) - BN_num_bytes(server_scalar);
os_memset(cruft, 0, BN_num_bytes(grp->prime));
BN_bn2bin(server_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(grp->order));
H_Final(&ctx, &session_id[1]);
/* then compute MK = H(k | commit-peer | commit-server) */
H_Init(&ctx);
offset = BN_num_bytes(grp->prime) - BN_num_bytes(k);
os_memset(cruft, 0, BN_num_bytes(grp->prime));
BN_bn2bin(k, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(grp->prime));
H_Update(&ctx, commit_peer, SHA256_DIGEST_LENGTH);
H_Update(&ctx, commit_server, SHA256_DIGEST_LENGTH);
H_Final(&ctx, mk);
/* stretch the mk with the session-id to get MSK | EMSK */
eap_pwd_kdf(mk, SHA256_DIGEST_LENGTH,
session_id, SHA256_DIGEST_LENGTH+1,
msk_emsk, (EAP_MSK_LEN + EAP_EMSK_LEN) * 8);
os_memcpy(msk, msk_emsk, EAP_MSK_LEN);
os_memcpy(emsk, msk_emsk + EAP_MSK_LEN, EAP_EMSK_LEN);
os_free(cruft);
return 1;
}
int
compute_peer_confirm (pwd_session_t *sess, uint8_t *buf, BN_CTX *bnctx)
{
BIGNUM *x = NULL, *y = NULL;
HMAC_CTX ctx;
uint8_t *cruft = NULL;
int offset, req = -1;
/*
* Each component of the cruft will be at most as big as the prime
*/
if (((cruft = talloc_zero_array(sess, uint8_t, BN_num_bytes(sess->prime))) == NULL) ||
((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
DEBUG2("pwd: unable to allocate space to compute confirm!");
goto fin;
}
/*
* commit is H(k | server_element | server_scalar | peer_element |
* peer_scalar | ciphersuite)
*/
H_Init(&ctx);
/*
* Zero the memory each time because this is mod prime math and some
* value may start with a few zeros and the previous one did not.
*
* First is k
*/
offset = BN_num_bytes(sess->prime) - BN_num_bytes(sess->k);
BN_bn2bin(sess->k, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
/*
* then peer element: x, y
*/
if (!EC_POINT_get_affine_coordinates_GFp(sess->group,
sess->peer_element, x, y,
bnctx)) {
DEBUG2("pwd: unable to get coordinates of peer's element");
goto fin;
}
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->prime) - BN_num_bytes(x);
BN_bn2bin(x, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->prime) - BN_num_bytes(y);
BN_bn2bin(y, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
/*
* and peer scalar
*/
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->order) - BN_num_bytes(sess->peer_scalar);
BN_bn2bin(sess->peer_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->order));
/*
* then server element: x, y
*/
if (!EC_POINT_get_affine_coordinates_GFp(sess->group,
sess->my_element, x, y,
bnctx)) {
DEBUG2("pwd: unable to get coordinates of server element");
goto fin;
}
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->prime) - BN_num_bytes(x);
BN_bn2bin(x, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->prime) - BN_num_bytes(y);
BN_bn2bin(y, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->prime));
/*
* and server scalar
*/
memset(cruft, 0, BN_num_bytes(sess->prime));
offset = BN_num_bytes(sess->order) - BN_num_bytes(sess->my_scalar);
BN_bn2bin(sess->my_scalar, cruft + offset);
H_Update(&ctx, cruft, BN_num_bytes(sess->order));
/*
* finally, ciphersuite
*/
H_Update(&ctx, (uint8_t *)&sess->ciphersuite, sizeof(sess->ciphersuite));
H_Final(&ctx, buf);
req = 0;
fin:
if (cruft != NULL) {
talloc_free(cruft);
}
BN_free(x);
BN_free(y);
return req;
}
int
compute_password_element (pwd_session_t *sess, uint16_t grp_num,
char *password, int password_len,
char *id_server, int id_server_len,
char *id_peer, int id_peer_len,
uint32_t *token)
{
BIGNUM *x_candidate = NULL, *rnd = NULL, *cofactor = NULL;
HMAC_CTX ctx;
uint8_t pwe_digest[SHA256_DIGEST_LENGTH], *prfbuf = NULL, ctr;
int nid, is_odd, primebitlen, primebytelen, ret = 0;
switch (grp_num) { /* from IANA registry for IKE D-H groups */
case 19:
nid = NID_X9_62_prime256v1;
break;
case 20:
nid = NID_secp384r1;
break;
case 21:
nid = NID_secp521r1;
break;
case 25:
nid = NID_X9_62_prime192v1;
break;
case 26:
nid = NID_secp224r1;
break;
default:
DEBUG("unknown group %d", grp_num);
goto fail;
}
sess->pwe = NULL;
sess->order = NULL;
sess->prime = NULL;
if ((sess->group = EC_GROUP_new_by_curve_name(nid)) == NULL) {
DEBUG("unable to create EC_GROUP");
goto fail;
}
if (((rnd = BN_new()) == NULL) ||
((cofactor = BN_new()) == NULL) ||
((sess->pwe = EC_POINT_new(sess->group)) == NULL) ||
((sess->order = BN_new()) == NULL) ||
((sess->prime = BN_new()) == NULL) ||
((x_candidate = BN_new()) == NULL)) {
DEBUG("unable to create bignums");
goto fail;
}
if (!EC_GROUP_get_curve_GFp(sess->group, sess->prime, NULL, NULL, NULL))
{
DEBUG("unable to get prime for GFp curve");
goto fail;
}
if (!EC_GROUP_get_order(sess->group, sess->order, NULL)) {
DEBUG("unable to get order for curve");
goto fail;
}
if (!EC_GROUP_get_cofactor(sess->group, cofactor, NULL)) {
DEBUG("unable to get cofactor for curve");
goto fail;
}
primebitlen = BN_num_bits(sess->prime);
primebytelen = BN_num_bytes(sess->prime);
if ((prfbuf = talloc_zero_array(sess, uint8_t, primebytelen)) == NULL) {
DEBUG("unable to alloc space for prf buffer");
goto fail;
}
ctr = 0;
while (1) {
if (ctr > 10) {
DEBUG("unable to find random point on curve for group %d, something's fishy", grp_num);
goto fail;
}
ctr++;
/*
* compute counter-mode password value and stretch to prime
* pwd-seed = H(token | peer-id | server-id | password |
* counter)
*/
H_Init(&ctx);
H_Update(&ctx, (uint8_t *)token, sizeof(*token));
H_Update(&ctx, (uint8_t *)id_peer, id_peer_len);
H_Update(&ctx, (uint8_t *)id_server, id_server_len);
H_Update(&ctx, (uint8_t *)password, password_len);
H_Update(&ctx, (uint8_t *)&ctr, sizeof(ctr));
H_Final(&ctx, pwe_digest);
BN_bin2bn(pwe_digest, SHA256_DIGEST_LENGTH, rnd);
eap_pwd_kdf(pwe_digest, SHA256_DIGEST_LENGTH,
"EAP-pwd Hunting And Pecking",
strlen("EAP-pwd Hunting And Pecking"),
prfbuf, primebitlen);
BN_bin2bn(prfbuf, primebytelen, x_candidate);
/*
* eap_pwd_kdf() returns a string of bits 0..primebitlen but
* BN_bin2bn will treat that string of bits as a big endian
* number. If the primebitlen is not an even multiple of 8
* then excessive bits-- those _after_ primebitlen-- so now
* we have to shift right the amount we masked off.
*/
if (primebitlen % 8) {
BN_rshift(x_candidate, x_candidate, (8 - (primebitlen % 8)));
}
if (BN_ucmp(x_candidate, sess->prime) >= 0) {
continue;
}
/*
* need to unambiguously identify the solution, if there is
* one...
*/
if (BN_is_odd(rnd)) {
is_odd = 1;
} else {
is_odd = 0;
}
/*
* solve the quadratic equation, if it's not solvable then we
* don't have a point
*/
if (!EC_POINT_set_compressed_coordinates_GFp(sess->group,
sess->pwe,
x_candidate,
is_odd, NULL)) {
continue;
}
/*
* 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 (!EC_POINT_is_on_curve(sess->group, sess->pwe, NULL)) {
DEBUG("EAP-pwd: point is not on curve");
continue;
}
if (BN_cmp(cofactor, BN_value_one())) {
/* make sure the point is not in a small sub-group */
if (!EC_POINT_mul(sess->group, sess->pwe, NULL, sess->pwe,
cofactor, NULL)) {
DEBUG("EAP-pwd: cannot multiply generator by order");
continue;
}
if (EC_POINT_is_at_infinity(sess->group, sess->pwe)) {
DEBUG("EAP-pwd: point is at infinity");
continue;
}
}
/* if we got here then we have a new generator. */
break;
}
sess->group_num = grp_num;
if (0) {
fail: /* DON'T free sess, it's in handler->opaque */
ret = -1;
}
/* cleanliness and order.... */
BN_free(cofactor);
BN_free(x_candidate);
BN_free(rnd);
talloc_free(prfbuf);
return ret;
}
static void
eap_pwd_process_confirm_resp(struct eap_sm *sm, struct eap_pwd_data *data,
const u8 *payload, size_t payload_len)
{
BIGNUM *x = NULL, *y = NULL;
HMAC_CTX ctx;
u32 cs;
u16 grp;
u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
/* build up the ciphersuite: group | random_function | prf */
grp = htons(data->group_num);
ptr = (u8 *) &cs;
os_memcpy(ptr, &grp, sizeof(u16));
ptr += sizeof(u16);
*ptr = EAP_PWD_DEFAULT_RAND_FUNC;
ptr += sizeof(u8);
*ptr = EAP_PWD_DEFAULT_PRF;
/* each component of the cruft will be at most as big as the prime */
if (((cruft = os_malloc(BN_num_bytes(data->grp->prime))) == NULL) ||
((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
wpa_printf(MSG_INFO, "EAP-PWD (peer): allocation fail");
goto fin;
}
/*
* commit is H(k | peer_element | peer_scalar | server_element |
* server_scalar | ciphersuite)
*/
H_Init(&ctx);
/* k */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->k, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* peer element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->peer_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* peer scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->peer_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* server element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->my_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->my_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* ciphersuite */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
H_Update(&ctx, (u8 *)&cs, sizeof(u32));
/* all done */
H_Final(&ctx, conf);
ptr = (u8 *) payload;
if (os_memcmp(conf, ptr, SHA256_DIGEST_LENGTH)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm did not "
"verify");
goto fin;
}
wpa_printf(MSG_DEBUG, "EAP-pwd (server): confirm verified");
if (compute_keys(data->grp, data->bnctx, data->k,
data->peer_scalar, data->my_scalar, conf,
data->my_confirm, &cs, data->msk, data->emsk) < 0)
eap_pwd_state(data, FAILURE);
else
eap_pwd_state(data, SUCCESS);
fin:
os_free(cruft);
BN_free(x);
BN_free(y);
}
static struct wpabuf *
eap_pwd_build_confirm_req(struct eap_sm *sm, struct eap_pwd_data *data, u8 id)
{
struct wpabuf *req = NULL;
BIGNUM *x = NULL, *y = NULL;
HMAC_CTX ctx;
u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
u16 grp;
wpa_printf(MSG_DEBUG, "EAP-pwd: Confirm/Request");
/* Each component of the cruft will be at most as big as the prime */
if (((cruft = os_malloc(BN_num_bytes(data->grp->prime))) == NULL) ||
((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): debug allocation "
"fail");
goto fin;
}
/*
* commit is H(k | server_element | server_scalar | peer_element |
* peer_scalar | ciphersuite)
*/
H_Init(&ctx);
/*
* Zero the memory each time because this is mod prime math and some
* value may start with a few zeros and the previous one did not.
*
* First is k
*/
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->k, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->my_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->my_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* peer element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->peer_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* peer scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->peer_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* ciphersuite */
grp = htons(data->group_num);
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
ptr = cruft;
os_memcpy(ptr, &grp, sizeof(u16));
ptr += sizeof(u16);
*ptr = EAP_PWD_DEFAULT_RAND_FUNC;
ptr += sizeof(u8);
*ptr = EAP_PWD_DEFAULT_PRF;
ptr += sizeof(u8);
H_Update(&ctx, cruft, ptr-cruft);
/* all done with the random function */
H_Final(&ctx, conf);
os_memcpy(data->my_confirm, conf, SHA256_DIGEST_LENGTH);
req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
sizeof(struct eap_pwd_hdr) + SHA256_DIGEST_LENGTH,
EAP_CODE_REQUEST, id);
if (req == NULL)
goto fin;
wpabuf_put_u8(req, EAP_PWD_OPCODE_CONFIRM_EXCH);
wpabuf_put_data(req, conf, SHA256_DIGEST_LENGTH);
fin:
os_free(cruft);
BN_free(x);
BN_free(y);
if (req == NULL)
eap_pwd_state(data, FAILURE);
return req;
}
static struct wpabuf *
eap_pwd_perform_confirm_exchange(struct eap_sm *sm, struct eap_pwd_data *data,
struct eap_method_ret *ret,
const struct wpabuf *reqData,
const u8 *payload, size_t payload_len)
{
struct wpabuf *resp = NULL;
BIGNUM *x = NULL, *y = NULL;
HMAC_CTX ctx;
u32 cs;
u16 grp;
u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
/*
* first build up the ciphersuite which is group | random_function |
* prf
*/
grp = htons(data->group_num);
ptr = (u8 *) &cs;
os_memcpy(ptr, &grp, sizeof(u16));
ptr += sizeof(u16);
*ptr = EAP_PWD_DEFAULT_RAND_FUNC;
ptr += sizeof(u8);
*ptr = EAP_PWD_DEFAULT_PRF;
/* each component of the cruft will be at most as big as the prime */
if (((cruft = os_malloc(BN_num_bytes(data->grp->prime))) == NULL) ||
((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): debug allocation "
"fail");
goto fin;
}
/*
* server's commit is H(k | server_element | server_scalar |
* peer_element | peer_scalar | ciphersuite)
*/
H_Init(&ctx);
/*
* zero the memory each time because this is mod prime math and some
* value may start with a few zeros and the previous one did not.
*/
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->k, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->server_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->server_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* my element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->my_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* my scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->my_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* the ciphersuite */
H_Update(&ctx, (u8 *) &cs, sizeof(u32));
/* random function fin */
H_Final(&ctx, conf);
ptr = (u8 *) payload;
if (os_memcmp(conf, ptr, SHA256_DIGEST_LENGTH)) {
wpa_printf(MSG_INFO, "EAP-PWD (peer): confirm did not verify");
goto fin;
}
wpa_printf(MSG_DEBUG, "EAP-pwd (peer): confirm verified");
/*
* compute confirm:
* H(k | peer_element | peer_scalar | server_element | server_scalar |
* ciphersuite)
*/
H_Init(&ctx);
/* k */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->k, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* my element */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->my_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (peer): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* my scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->my_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* server element: x, y */
if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
data->server_element, x, y,
data->bnctx)) {
wpa_printf(MSG_INFO, "EAP-PWD (peer): confirm point "
"assignment fail");
goto fin;
}
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(x, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(y, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->prime));
/* server scalar */
os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
BN_bn2bin(data->server_scalar, cruft);
H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
/* the ciphersuite */
H_Update(&ctx, (u8 *) &cs, sizeof(u32));
/* all done */
H_Final(&ctx, conf);
resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
sizeof(struct eap_pwd_hdr) + SHA256_DIGEST_LENGTH,
EAP_CODE_RESPONSE, eap_get_id(reqData));
if (resp == NULL)
goto fin;
wpabuf_put_u8(resp, EAP_PWD_OPCODE_CONFIRM_EXCH);
wpabuf_put_data(resp, conf, SHA256_DIGEST_LENGTH);
if (compute_keys(data->grp, data->bnctx, data->k,
data->my_scalar, data->server_scalar, conf, ptr,
&cs, data->msk, data->emsk) < 0) {
wpa_printf(MSG_INFO, "EAP-PWD (peer): unable to compute MSK | "
"EMSK");
goto fin;
}
fin:
os_free(cruft);
BN_free(x);
BN_free(y);
ret->methodState = METHOD_DONE;
if (resp == NULL) {
ret->decision = DECISION_FAIL;
eap_pwd_state(data, FAILURE);
} else {
ret->decision = DECISION_UNCOND_SUCC;
eap_pwd_state(data, SUCCESS);
}
return resp;
}
/*
* 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,
u8 *password, int password_len,
u8 *id_server, int id_server_len,
u8 *id_peer, int id_peer_len, u8 *token)
{
BIGNUM *x_candidate = NULL, *rnd = NULL, *cofactor = NULL;
HMAC_CTX ctx;
unsigned char pwe_digest[SHA256_DIGEST_LENGTH], *prfbuf = NULL, ctr;
int nid, is_odd, primebitlen, primebytelen, ret = 0;
switch (num) { /* from IANA registry for IKE D-H groups */
case 19:
nid = NID_X9_62_prime256v1;
break;
case 20:
nid = NID_secp384r1;
break;
case 21:
nid = NID_secp521r1;
break;
case 25:
nid = NID_X9_62_prime192v1;
break;
case 26:
nid = NID_secp224r1;
break;
default:
wpa_printf(MSG_INFO, "EAP-pwd: unsupported group %d", num);
return -1;
}
grp->pwe = NULL;
grp->order = NULL;
grp->prime = NULL;
if ((grp->group = EC_GROUP_new_by_curve_name(nid)) == NULL) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to create EC_GROUP");
goto fail;
}
if (((rnd = BN_new()) == NULL) ||
((cofactor = BN_new()) == NULL) ||
((grp->pwe = EC_POINT_new(grp->group)) == NULL) ||
((grp->order = BN_new()) == NULL) ||
((grp->prime = BN_new()) == NULL) ||
((x_candidate = BN_new()) == NULL)) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to create bignums");
goto fail;
}
if (!EC_GROUP_get_curve_GFp(grp->group, grp->prime, NULL, NULL, NULL))
{
wpa_printf(MSG_INFO, "EAP-pwd: unable to get prime for GFp "
"curve");
goto fail;
}
if (!EC_GROUP_get_order(grp->group, grp->order, NULL)) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to get order for curve");
goto fail;
}
if (!EC_GROUP_get_cofactor(grp->group, cofactor, NULL)) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to get cofactor for "
"curve");
goto fail;
}
primebitlen = BN_num_bits(grp->prime);
primebytelen = BN_num_bytes(grp->prime);
if ((prfbuf = os_malloc(primebytelen)) == NULL) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf "
"buffer");
goto fail;
}
os_memset(prfbuf, 0, primebytelen);
ctr = 0;
while (1) {
if (ctr > 30) {
wpa_printf(MSG_INFO, "EAP-pwd: unable to find random "
"point on curve for group %d, something's "
"fishy", num);
goto fail;
}
ctr++;
/*
* compute counter-mode password value and stretch to prime
* pwd-seed = H(token | peer-id | server-id | password |
* counter)
*/
H_Init(&ctx);
H_Update(&ctx, token, sizeof(u32));
H_Update(&ctx, id_peer, id_peer_len);
H_Update(&ctx, id_server, id_server_len);
H_Update(&ctx, password, password_len);
H_Update(&ctx, &ctr, sizeof(ctr));
H_Final(&ctx, pwe_digest);
BN_bin2bn(pwe_digest, SHA256_DIGEST_LENGTH, rnd);
eap_pwd_kdf(pwe_digest, SHA256_DIGEST_LENGTH,
(unsigned char *) "EAP-pwd Hunting And Pecking",
os_strlen("EAP-pwd Hunting And Pecking"),
prfbuf, primebitlen);
BN_bin2bn(prfbuf, primebytelen, x_candidate);
/*
* eap_pwd_kdf() returns a string of bits 0..primebitlen but
* BN_bin2bn will treat that string of bits as a big endian
* number. If the primebitlen is not an even multiple of 8
* then excessive bits-- those _after_ primebitlen-- so now
* we have to shift right the amount we masked off.
*/
if (primebitlen % 8)
BN_rshift(x_candidate, x_candidate,
(8 - (primebitlen % 8)));
if (BN_ucmp(x_candidate, grp->prime) >= 0)
continue;
wpa_hexdump(MSG_DEBUG, "EAP-pwd: x_candidate",
prfbuf, primebytelen);
/*
* need to unambiguously identify the solution, if there is
* one...
*/
if (BN_is_odd(rnd))
is_odd = 1;
else
is_odd = 0;
/*
* solve the quadratic equation, if it's not solvable then we
* don't have a point
*/
if (!EC_POINT_set_compressed_coordinates_GFp(grp->group,
grp->pwe,
x_candidate,
is_odd, NULL))
continue;
/*
* 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 (!EC_POINT_is_on_curve(grp->group, grp->pwe, NULL)) {
wpa_printf(MSG_INFO, "EAP-pwd: point is not on curve");
continue;
}
if (BN_cmp(cofactor, BN_value_one())) {
/* make sure the point is not in a small sub-group */
if (!EC_POINT_mul(grp->group, grp->pwe, NULL, grp->pwe,
cofactor, NULL)) {
wpa_printf(MSG_INFO, "EAP-pwd: cannot "
"multiply generator by order");
continue;
}
if (EC_POINT_is_at_infinity(grp->group, grp->pwe)) {
wpa_printf(MSG_INFO, "EAP-pwd: point is at "
"infinity");
continue;
}
}
/* if we got here then we have a new generator. */
break;
}
wpa_printf(MSG_DEBUG, "EAP-pwd: found a PWE in %d tries", ctr);
grp->group_num = num;
if (0) {
fail:
EC_GROUP_free(grp->group);
EC_POINT_free(grp->pwe);
BN_free(grp->order);
BN_free(grp->prime);
os_free(grp);
grp = NULL;
ret = 1;
}
/* cleanliness and order.... */
BN_free(cofactor);
BN_free(x_candidate);
BN_free(rnd);
os_free(prfbuf);
return ret;
}