src/eap_server/eap_psk.c

   1 /*
   2  * hostapd / EAP-PSK (RFC 4764) server
   3  * Copyright (c) 2005-2007, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  *
  14  * Note: EAP-PSK is an EAP authentication method and as such, completely
  15  * different from WPA-PSK. This file is not needed for WPA-PSK functionality.
  16  */
  17
  18 #include "includes.h"
  19
  20 #include "common.h"
  21 #include "crypto/aes_wrap.h"
  22 #include "eap_common/eap_psk_common.h"
  23 #include "eap_server/eap_i.h"
  24
  25
  26 struct eap_psk_data {
  27         enum { PSK_1, PSK_3, SUCCESS, FAILURE } state;
  28         u8 rand_s[EAP_PSK_RAND_LEN];
  29         u8 rand_p[EAP_PSK_RAND_LEN];
  30         u8 *id_p, *id_s;
  31         size_t id_p_len, id_s_len;
  32         u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
  33         u8 msk[EAP_MSK_LEN];
  34         u8 emsk[EAP_EMSK_LEN];
  35 };
  36
  37
  38 static void * eap_psk_init(struct eap_sm *sm)
  39 {
  40         struct eap_psk_data *data;
  41
  42         data = os_zalloc(sizeof(*data));
  43         if (data == NULL)
  44                 return NULL;
  45         data->state = PSK_1;
  46         data->id_s = (u8 *) "hostapd";
  47         data->id_s_len = 7;
  48
  49         return data;
  50 }
  51
  52
  53 static void eap_psk_reset(struct eap_sm *sm, void *priv)
  54 {
  55         struct eap_psk_data *data = priv;
  56         os_free(data->id_p);
  57         os_free(data);
  58 }
  59
  60
  61 static struct wpabuf * eap_psk_build_1(struct eap_sm *sm,
  62                                        struct eap_psk_data *data, u8 id)
  63 {
  64         struct wpabuf *req;
  65         struct eap_psk_hdr_1 *psk;
  66
  67         wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-1 (sending)");
  68
  69         if (os_get_random(data->rand_s, EAP_PSK_RAND_LEN)) {
  70                 wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
  71                 data->state = FAILURE;
  72                 return NULL;
  73         }
  74         wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_S (server rand)",
  75                     data->rand_s, EAP_PSK_RAND_LEN);
  76
  77         req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
  78                             sizeof(*psk) + data->id_s_len,
  79                             EAP_CODE_REQUEST, id);
  80         if (req == NULL) {
  81                 wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
  82                            "request");
  83                 data->state = FAILURE;
  84                 return NULL;
  85         }
  86
  87         psk = wpabuf_put(req, sizeof(*psk));
  88         psk->flags = EAP_PSK_FLAGS_SET_T(0); /* T=0 */
  89         os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);
  90         wpabuf_put_data(req, data->id_s, data->id_s_len);
  91
  92         return req;
  93 }
  94
  95
  96 static struct wpabuf * eap_psk_build_3(struct eap_sm *sm,
  97                                        struct eap_psk_data *data, u8 id)
  98 {
  99         struct wpabuf *req;
 100         struct eap_psk_hdr_3 *psk;
 101         u8 *buf, *pchannel, nonce[16];
 102         size_t buflen;
 103
 104         wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-3 (sending)");
 105
 106         req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
 107                             sizeof(*psk) + 4 + 16 + 1, EAP_CODE_REQUEST, id);
 108         if (req == NULL) {
 109                 wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
 110                            "request");
 111                 data->state = FAILURE;
 112                 return NULL;
 113         }
 114
 115         psk = wpabuf_put(req, sizeof(*psk));
 116         psk->flags = EAP_PSK_FLAGS_SET_T(2); /* T=2 */
 117         os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);
 118
 119         /* MAC_S = OMAC1-AES-128(AK, ID_S||RAND_P) */
 120         buflen = data->id_s_len + EAP_PSK_RAND_LEN;
 121         buf = os_malloc(buflen);
 122         if (buf == NULL)
 123                 goto fail;
 124
 125         os_memcpy(buf, data->id_s, data->id_s_len);
 126         os_memcpy(buf + data->id_s_len, data->rand_p, EAP_PSK_RAND_LEN);
 127         if (omac1_aes_128(data->ak, buf, buflen, psk->mac_s))
 128                 goto fail;
 129         os_free(buf);
 130
 131         if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek, data->msk,
 132                                 data->emsk))
 133                 goto fail;
 134         wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: TEK", data->tek, EAP_PSK_TEK_LEN);
 135         wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: MSK", data->msk, EAP_MSK_LEN);
 136         wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: EMSK", data->emsk, EAP_EMSK_LEN);
 137
 138         os_memset(nonce, 0, sizeof(nonce));
 139         pchannel = wpabuf_put(req, 4 + 16 + 1);
 140         os_memcpy(pchannel, nonce + 12, 4);
 141         os_memset(pchannel + 4, 0, 16); /* Tag */
 142         pchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;
 143         wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (plaintext)",
 144                     pchannel, 4 + 16 + 1);
 145         if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
 146                                 wpabuf_head(req), 22,
 147                                 pchannel + 4 + 16, 1, pchannel + 4))
 148                 goto fail;
 149         wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (encrypted)",
 150                     pchannel, 4 + 16 + 1);
 151
 152         return req;
 153
 154 fail:
 155         wpabuf_free(req);
 156         data->state = FAILURE;
 157         return NULL;
 158 }
 159
 160
 161 static struct wpabuf * eap_psk_buildReq(struct eap_sm *sm, void *priv, u8 id)
 162 {
 163         struct eap_psk_data *data = priv;
 164
 165         switch (data->state) {
 166         case PSK_1:
 167                 return eap_psk_build_1(sm, data, id);
 168         case PSK_3:
 169                 return eap_psk_build_3(sm, data, id);
 170         default:
 171                 wpa_printf(MSG_DEBUG, "EAP-PSK: Unknown state %d in buildReq",
 172                            data->state);
 173                 break;
 174         }
 175         return NULL;
 176 }
 177
 178
 179 static Boolean eap_psk_check(struct eap_sm *sm, void *priv,
 180                              struct wpabuf *respData)
 181 {
 182         struct eap_psk_data *data = priv;
 183         size_t len;
 184         u8 t;
 185         const u8 *pos;
 186
 187         pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
 188         if (pos == NULL || len < 1) {
 189                 wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
 190                 return TRUE;
 191         }
 192         t = EAP_PSK_FLAGS_GET_T(*pos);
 193
 194         wpa_printf(MSG_DEBUG, "EAP-PSK: received frame: T=%d", t);
 195
 196         if (data->state == PSK_1 && t != 1) {
 197                 wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-2 - "
 198                            "ignore T=%d", t);
 199                 return TRUE;
 200         }
 201
 202         if (data->state == PSK_3 && t != 3) {
 203                 wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-4 - "
 204                            "ignore T=%d", t);
 205                 return TRUE;
 206         }
 207
 208         if ((t == 1 && len < sizeof(struct eap_psk_hdr_2)) ||
 209             (t == 3 && len < sizeof(struct eap_psk_hdr_4))) {
 210                 wpa_printf(MSG_DEBUG, "EAP-PSK: Too short frame");
 211                 return TRUE;
 212         }
 213
 214         return FALSE;
 215 }
 216
 217
 218 static void eap_psk_process_2(struct eap_sm *sm,
 219                               struct eap_psk_data *data,
 220                               struct wpabuf *respData)
 221 {
 222         const struct eap_psk_hdr_2 *resp;
 223         u8 *pos, mac[EAP_PSK_MAC_LEN], *buf;
 224         size_t left, buflen;
 225         int i;
 226         const u8 *cpos;
 227
 228         if (data->state != PSK_1)
 229                 return;
 230
 231         wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-2");
 232
 233         cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData,
 234                                 &left);
 235         if (cpos == NULL || left < sizeof(*resp)) {
 236                 wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
 237                 return;
 238         }
 239         resp = (const struct eap_psk_hdr_2 *) cpos;
 240         cpos = (const u8 *) (resp + 1);
 241         left -= sizeof(*resp);
 242
 243         os_free(data->id_p);
 244         data->id_p = os_malloc(left);
 245         if (data->id_p == NULL) {
 246                 wpa_printf(MSG_INFO, "EAP-PSK: Failed to allocate memory for "
 247                            "ID_P");
 248                 return;
 249         }
 250         os_memcpy(data->id_p, cpos, left);
 251         data->id_p_len = left;
 252         wpa_hexdump_ascii(MSG_MSGDUMP, "EAP-PSK: ID_P",
 253                           data->id_p, data->id_p_len);
 254
 255         if (eap_user_get(sm, data->id_p, data->id_p_len, 0) < 0) {
 256                 wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: unknown ID_P",
 257                                   data->id_p, data->id_p_len);
 258                 data->state = FAILURE;
 259                 return;
 260         }
 261
 262         for (i = 0;
 263              i < EAP_MAX_METHODS &&
 264                      (sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
 265                       sm->user->methods[i].method != EAP_TYPE_NONE);
 266              i++) {
 267                 if (sm->user->methods[i].vendor == EAP_VENDOR_IETF &&
 268                     sm->user->methods[i].method == EAP_TYPE_PSK)
 269                         break;
 270         }
 271
 272         if (i >= EAP_MAX_METHODS ||
 273             sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
 274             sm->user->methods[i].method != EAP_TYPE_PSK) {
 275                 wpa_hexdump_ascii(MSG_DEBUG,
 276                                   "EAP-PSK: EAP-PSK not enabled for ID_P",
 277                                   data->id_p, data->id_p_len);
 278                 data->state = FAILURE;
 279                 return;
 280         }
 281
 282         if (sm->user->password == NULL ||
 283             sm->user->password_len != EAP_PSK_PSK_LEN) {
 284                 wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: invalid password in "
 285                                   "user database for ID_P",
 286                                   data->id_p, data->id_p_len);
 287                 data->state = FAILURE;
 288                 return;
 289         }
 290         if (eap_psk_key_setup(sm->user->password, data->ak, data->kdk)) {
 291                 data->state = FAILURE;
 292                 return;
 293         }
 294         wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: AK", data->ak, EAP_PSK_AK_LEN);
 295         wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: KDK", data->kdk, EAP_PSK_KDK_LEN);
 296
 297         wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_P (client rand)",
 298                     resp->rand_p, EAP_PSK_RAND_LEN);
 299         os_memcpy(data->rand_p, resp->rand_p, EAP_PSK_RAND_LEN);
 300
 301         /* MAC_P = OMAC1-AES-128(AK, ID_P||ID_S||RAND_S||RAND_P) */
 302         buflen = data->id_p_len + data->id_s_len + 2 * EAP_PSK_RAND_LEN;
 303         buf = os_malloc(buflen);
 304         if (buf == NULL) {
 305                 data->state = FAILURE;
 306                 return;
 307         }
 308         os_memcpy(buf, data->id_p, data->id_p_len);
 309         pos = buf + data->id_p_len;
 310         os_memcpy(pos, data->id_s, data->id_s_len);
 311         pos += data->id_s_len;
 312         os_memcpy(pos, data->rand_s, EAP_PSK_RAND_LEN);
 313         pos += EAP_PSK_RAND_LEN;
 314         os_memcpy(pos, data->rand_p, EAP_PSK_RAND_LEN);
 315         if (omac1_aes_128(data->ak, buf, buflen, mac)) {
 316                 os_free(buf);
 317                 data->state = FAILURE;
 318                 return;
 319         }
 320         os_free(buf);
 321         wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", resp->mac_p, EAP_PSK_MAC_LEN);
 322         if (os_memcmp(mac, resp->mac_p, EAP_PSK_MAC_LEN) != 0) {
 323                 wpa_printf(MSG_INFO, "EAP-PSK: Invalid MAC_P");
 324                 wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Expected MAC_P",
 325                             mac, EAP_PSK_MAC_LEN);
 326                 data->state = FAILURE;
 327                 return;
 328         }
 329
 330         data->state = PSK_3;
 331 }
 332
 333
 334 static void eap_psk_process_4(struct eap_sm *sm,
 335                               struct eap_psk_data *data,
 336                               struct wpabuf *respData)
 337 {
 338         const struct eap_psk_hdr_4 *resp;
 339         u8 *decrypted, nonce[16];
 340         size_t left;
 341         const u8 *pos, *tag;
 342
 343         if (data->state != PSK_3)
 344                 return;
 345
 346         wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-4");
 347
 348         pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &left);
 349         if (pos == NULL || left < sizeof(*resp)) {
 350                 wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
 351                 return;
 352         }
 353         resp = (const struct eap_psk_hdr_4 *) pos;
 354         pos = (const u8 *) (resp + 1);
 355         left -= sizeof(*resp);
 356
 357         wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Encrypted PCHANNEL", pos, left);
 358
 359         if (left < 4 + 16 + 1) {
 360                 wpa_printf(MSG_INFO, "EAP-PSK: Too short PCHANNEL data in "
 361                            "PSK-4 (len=%lu, expected 21)",
 362                            (unsigned long) left);
 363                 return;
 364         }
 365
 366         if (pos[0] == 0 && pos[1] == 0 && pos[2] == 0 && pos[3] == 0) {
 367                 wpa_printf(MSG_DEBUG, "EAP-PSK: Nonce did not increase");
 368                 return;
 369         }
 370
 371         os_memset(nonce, 0, 12);
 372         os_memcpy(nonce + 12, pos, 4);
 373         pos += 4;
 374         left -= 4;
 375         tag = pos;
 376         pos += 16;
 377         left -= 16;
 378
 379         decrypted = os_malloc(left);
 380         if (decrypted == NULL)
 381                 return;
 382         os_memcpy(decrypted, pos, left);
 383
 384         if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
 385                                 wpabuf_head(respData), 22, decrypted, left,
 386                                 tag)) {
 387                 wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
 388                 os_free(decrypted);
 389                 data->state = FAILURE;
 390                 return;
 391         }
 392         wpa_hexdump(MSG_DEBUG, "EAP-PSK: Decrypted PCHANNEL message",
 393                     decrypted, left);
 394
 395         /* Verify R flag */
 396         switch (decrypted[0] >> 6) {
 397         case EAP_PSK_R_FLAG_CONT:
 398                 wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - CONT - unsupported");
 399                 data->state = FAILURE;
 400                 break;
 401         case EAP_PSK_R_FLAG_DONE_SUCCESS:
 402                 wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
 403                 data->state = SUCCESS;
 404                 break;
 405         case EAP_PSK_R_FLAG_DONE_FAILURE:
 406                 wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
 407                 data->state = FAILURE;
 408                 break;
 409         }
 410         os_free(decrypted);
 411 }
 412
 413
 414 static void eap_psk_process(struct eap_sm *sm, void *priv,
 415                             struct wpabuf *respData)
 416 {
 417         struct eap_psk_data *data = priv;
 418         const u8 *pos;
 419         size_t len;
 420
 421         if (sm->user == NULL || sm->user->password == NULL) {
 422                 wpa_printf(MSG_INFO, "EAP-PSK: Plaintext password not "
 423                            "configured");
 424                 data->state = FAILURE;
 425                 return;
 426         }
 427
 428         pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
 429         if (pos == NULL || len < 1)
 430                 return;
 431
 432         switch (EAP_PSK_FLAGS_GET_T(*pos)) {
 433         case 1:
 434                 eap_psk_process_2(sm, data, respData);
 435                 break;
 436         case 3:
 437                 eap_psk_process_4(sm, data, respData);
 438                 break;
 439         }
 440 }
 441
 442
 443 static Boolean eap_psk_isDone(struct eap_sm *sm, void *priv)
 444 {
 445         struct eap_psk_data *data = priv;
 446         return data->state == SUCCESS || data->state == FAILURE;
 447 }
 448
 449
 450 static u8 * eap_psk_getKey(struct eap_sm *sm, void *priv, size_t *len)
 451 {
 452         struct eap_psk_data *data = priv;
 453         u8 *key;
 454
 455         if (data->state != SUCCESS)
 456                 return NULL;
 457
 458         key = os_malloc(EAP_MSK_LEN);
 459         if (key == NULL)
 460                 return NULL;
 461         os_memcpy(key, data->msk, EAP_MSK_LEN);
 462         *len = EAP_MSK_LEN;
 463
 464         return key;
 465 }
 466
 467
 468 static u8 * eap_psk_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
 469 {
 470         struct eap_psk_data *data = priv;
 471         u8 *key;
 472
 473         if (data->state != SUCCESS)
 474                 return NULL;
 475
 476         key = os_malloc(EAP_EMSK_LEN);
 477         if (key == NULL)
 478                 return NULL;
 479         os_memcpy(key, data->emsk, EAP_EMSK_LEN);
 480         *len = EAP_EMSK_LEN;
 481
 482         return key;
 483 }
 484
 485
 486 static Boolean eap_psk_isSuccess(struct eap_sm *sm, void *priv)
 487 {
 488         struct eap_psk_data *data = priv;
 489         return data->state == SUCCESS;
 490 }
 491
 492
 493 int eap_server_psk_register(void)
 494 {
 495         struct eap_method *eap;
 496         int ret;
 497
 498         eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
 499                                       EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
 500         if (eap == NULL)
 501                 return -1;
 502
 503         eap->init = eap_psk_init;
 504         eap->reset = eap_psk_reset;
 505         eap->buildReq = eap_psk_buildReq;
 506         eap->check = eap_psk_check;
 507         eap->process = eap_psk_process;
 508         eap->isDone = eap_psk_isDone;
 509         eap->getKey = eap_psk_getKey;
 510         eap->isSuccess = eap_psk_isSuccess;
 511         eap->get_emsk = eap_psk_get_emsk;
 512
 513         ret = eap_server_method_register(eap);
 514         if (ret)
 515                 eap_server_method_free(eap);
 516         return ret;
 517 }