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      1 /*
      2  * EAP server/peer: EAP-SAKE shared routines
      3  * Copyright (c) 2006-2007, Jouni Malinen <j (at) w1.fi>
      4  *
      5  * This software may be distributed under the terms of the BSD license.
      6  * See README for more details.
      7  */
      8 
      9 #include "includes.h"
     10 
     11 #include "common.h"
     12 #include "wpabuf.h"
     13 #include "crypto/sha1.h"
     14 #include "eap_defs.h"
     15 #include "eap_sake_common.h"
     16 
     17 
     18 static int eap_sake_parse_add_attr(struct eap_sake_parse_attr *attr,
     19 				   const u8 *pos)
     20 {
     21 	size_t i;
     22 
     23 	switch (pos[0]) {
     24 	case EAP_SAKE_AT_RAND_S:
     25 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_RAND_S");
     26 		if (pos[1] != 2 + EAP_SAKE_RAND_LEN) {
     27 			wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_RAND_S with "
     28 				   "invalid length %d", pos[1]);
     29 			return -1;
     30 		}
     31 		attr->rand_s = pos + 2;
     32 		break;
     33 	case EAP_SAKE_AT_RAND_P:
     34 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_RAND_P");
     35 		if (pos[1] != 2 + EAP_SAKE_RAND_LEN) {
     36 			wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_RAND_P with "
     37 				   "invalid length %d", pos[1]);
     38 			return -1;
     39 		}
     40 		attr->rand_p = pos + 2;
     41 		break;
     42 	case EAP_SAKE_AT_MIC_S:
     43 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_MIC_S");
     44 		if (pos[1] != 2 + EAP_SAKE_MIC_LEN) {
     45 			wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_MIC_S with "
     46 				   "invalid length %d", pos[1]);
     47 			return -1;
     48 		}
     49 		attr->mic_s = pos + 2;
     50 		break;
     51 	case EAP_SAKE_AT_MIC_P:
     52 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_MIC_P");
     53 		if (pos[1] != 2 + EAP_SAKE_MIC_LEN) {
     54 			wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_MIC_P with "
     55 				   "invalid length %d", pos[1]);
     56 			return -1;
     57 		}
     58 		attr->mic_p = pos + 2;
     59 		break;
     60 	case EAP_SAKE_AT_SERVERID:
     61 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_SERVERID");
     62 		attr->serverid = pos + 2;
     63 		attr->serverid_len = pos[1] - 2;
     64 		break;
     65 	case EAP_SAKE_AT_PEERID:
     66 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_PEERID");
     67 		attr->peerid = pos + 2;
     68 		attr->peerid_len = pos[1] - 2;
     69 		break;
     70 	case EAP_SAKE_AT_SPI_S:
     71 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_SPI_S");
     72 		attr->spi_s = pos + 2;
     73 		attr->spi_s_len = pos[1] - 2;
     74 		break;
     75 	case EAP_SAKE_AT_SPI_P:
     76 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_SPI_P");
     77 		attr->spi_p = pos + 2;
     78 		attr->spi_p_len = pos[1] - 2;
     79 		break;
     80 	case EAP_SAKE_AT_ANY_ID_REQ:
     81 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_ANY_ID_REQ");
     82 		if (pos[1] != 4) {
     83 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Invalid AT_ANY_ID_REQ"
     84 				   " length %d", pos[1]);
     85 			return -1;
     86 		}
     87 		attr->any_id_req = pos + 2;
     88 		break;
     89 	case EAP_SAKE_AT_PERM_ID_REQ:
     90 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_PERM_ID_REQ");
     91 		if (pos[1] != 4) {
     92 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Invalid "
     93 				   "AT_PERM_ID_REQ length %d", pos[1]);
     94 			return -1;
     95 		}
     96 		attr->perm_id_req = pos + 2;
     97 		break;
     98 	case EAP_SAKE_AT_ENCR_DATA:
     99 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_ENCR_DATA");
    100 		attr->encr_data = pos + 2;
    101 		attr->encr_data_len = pos[1] - 2;
    102 		break;
    103 	case EAP_SAKE_AT_IV:
    104 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_IV");
    105 		attr->iv = pos + 2;
    106 		attr->iv_len = pos[1] - 2;
    107 		break;
    108 	case EAP_SAKE_AT_PADDING:
    109 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_PADDING");
    110 		for (i = 2; i < pos[1]; i++) {
    111 			if (pos[i]) {
    112 				wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_PADDING "
    113 					   "with non-zero pad byte");
    114 				return -1;
    115 			}
    116 		}
    117 		break;
    118 	case EAP_SAKE_AT_NEXT_TMPID:
    119 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_NEXT_TMPID");
    120 		attr->next_tmpid = pos + 2;
    121 		attr->next_tmpid_len = pos[1] - 2;
    122 		break;
    123 	case EAP_SAKE_AT_MSK_LIFE:
    124 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Parse: AT_IV");
    125 		if (pos[1] != 6) {
    126 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Invalid "
    127 				   "AT_MSK_LIFE length %d", pos[1]);
    128 			return -1;
    129 		}
    130 		attr->msk_life = pos + 2;
    131 		break;
    132 	default:
    133 		if (pos[0] < 128) {
    134 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Unknown non-skippable"
    135 				   " attribute %d", pos[0]);
    136 			return -1;
    137 		}
    138 		wpa_printf(MSG_DEBUG, "EAP-SAKE: Ignoring unknown skippable "
    139 			   "attribute %d", pos[0]);
    140 		break;
    141 	}
    142 
    143 	if (attr->iv && !attr->encr_data) {
    144 		wpa_printf(MSG_DEBUG, "EAP-SAKE: AT_IV included without "
    145 			   "AT_ENCR_DATA");
    146 		return -1;
    147 	}
    148 
    149 	return 0;
    150 }
    151 
    152 
    153 /**
    154  * eap_sake_parse_attributes - Parse EAP-SAKE attributes
    155  * @buf: Packet payload (starting with the first attribute)
    156  * @len: Payload length
    157  * @attr: Structure to be filled with found attributes
    158  * Returns: 0 on success or -1 on failure
    159  */
    160 int eap_sake_parse_attributes(const u8 *buf, size_t len,
    161 			      struct eap_sake_parse_attr *attr)
    162 {
    163 	const u8 *pos = buf, *end = buf + len;
    164 
    165 	os_memset(attr, 0, sizeof(*attr));
    166 	while (pos < end) {
    167 		if (end - pos < 2) {
    168 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Too short attribute");
    169 			return -1;
    170 		}
    171 
    172 		if (pos[1] < 2) {
    173 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Invalid attribute "
    174 				   "length (%d)", pos[1]);
    175 			return -1;
    176 		}
    177 
    178 		if (pos + pos[1] > end) {
    179 			wpa_printf(MSG_DEBUG, "EAP-SAKE: Attribute underflow");
    180 			return -1;
    181 		}
    182 
    183 		if (eap_sake_parse_add_attr(attr, pos))
    184 			return -1;
    185 
    186 		pos += pos[1];
    187 	}
    188 
    189 	return 0;
    190 }
    191 
    192 
    193 /**
    194  * eap_sake_kdf - EAP-SAKE Key Derivation Function (KDF)
    195  * @key: Key for KDF
    196  * @key_len: Length of the key in bytes
    197  * @label: A unique label for each purpose of the KDF
    198  * @data: Extra data (start) to bind into the key
    199  * @data_len: Length of the data
    200  * @data2: Extra data (end) to bind into the key
    201  * @data2_len: Length of the data2
    202  * @buf: Buffer for the generated pseudo-random key
    203  * @buf_len: Number of bytes of key to generate
    204  *
    205  * This function is used to derive new, cryptographically separate keys from a
    206  * given key (e.g., SMS). This is identical to the PRF used in IEEE 802.11i.
    207  */
    208 static void eap_sake_kdf(const u8 *key, size_t key_len, const char *label,
    209 			 const u8 *data, size_t data_len,
    210 			 const u8 *data2, size_t data2_len,
    211 			 u8 *buf, size_t buf_len)
    212 {
    213 	u8 counter = 0;
    214 	size_t pos, plen;
    215 	u8 hash[SHA1_MAC_LEN];
    216 	size_t label_len = os_strlen(label) + 1;
    217 	const unsigned char *addr[4];
    218 	size_t len[4];
    219 
    220 	addr[0] = (u8 *) label; /* Label | Y */
    221 	len[0] = label_len;
    222 	addr[1] = data; /* Msg[start] */
    223 	len[1] = data_len;
    224 	addr[2] = data2; /* Msg[end] */
    225 	len[2] = data2_len;
    226 	addr[3] = &counter; /* Length */
    227 	len[3] = 1;
    228 
    229 	pos = 0;
    230 	while (pos < buf_len) {
    231 		plen = buf_len - pos;
    232 		if (plen >= SHA1_MAC_LEN) {
    233 			hmac_sha1_vector(key, key_len, 4, addr, len,
    234 					 &buf[pos]);
    235 			pos += SHA1_MAC_LEN;
    236 		} else {
    237 			hmac_sha1_vector(key, key_len, 4, addr, len,
    238 					 hash);
    239 			os_memcpy(&buf[pos], hash, plen);
    240 			break;
    241 		}
    242 		counter++;
    243 	}
    244 }
    245 
    246 
    247 /**
    248  * eap_sake_derive_keys - Derive EAP-SAKE keys
    249  * @root_secret_a: 16-byte Root-Secret-A
    250  * @root_secret_b: 16-byte Root-Secret-B
    251  * @rand_s: 16-byte RAND_S
    252  * @rand_p: 16-byte RAND_P
    253  * @tek: Buffer for Temporary EAK Keys (TEK-Auth[16] | TEK-Cipher[16])
    254  * @msk: Buffer for 64-byte MSK
    255  * @emsk: Buffer for 64-byte EMSK
    256  *
    257  * This function derives EAP-SAKE keys as defined in RFC 4763, section 3.2.6.
    258  */
    259 void eap_sake_derive_keys(const u8 *root_secret_a, const u8 *root_secret_b,
    260 			  const u8 *rand_s, const u8 *rand_p, u8 *tek, u8 *msk,
    261 			  u8 *emsk)
    262 {
    263 	u8 sms_a[EAP_SAKE_SMS_LEN];
    264 	u8 sms_b[EAP_SAKE_SMS_LEN];
    265 	u8 key_buf[EAP_MSK_LEN + EAP_EMSK_LEN];
    266 
    267 	wpa_printf(MSG_DEBUG, "EAP-SAKE: Deriving keys");
    268 
    269 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: Root-Secret-A",
    270 			root_secret_a, EAP_SAKE_ROOT_SECRET_LEN);
    271 	eap_sake_kdf(root_secret_a, EAP_SAKE_ROOT_SECRET_LEN,
    272 		     "SAKE Master Secret A",
    273 		     rand_p, EAP_SAKE_RAND_LEN, rand_s, EAP_SAKE_RAND_LEN,
    274 		     sms_a, EAP_SAKE_SMS_LEN);
    275 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: SMS-A", sms_a, EAP_SAKE_SMS_LEN);
    276 	eap_sake_kdf(sms_a, EAP_SAKE_SMS_LEN, "Transient EAP Key",
    277 		     rand_s, EAP_SAKE_RAND_LEN, rand_p, EAP_SAKE_RAND_LEN,
    278 		     tek, EAP_SAKE_TEK_LEN);
    279 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: TEK-Auth",
    280 			tek, EAP_SAKE_TEK_AUTH_LEN);
    281 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: TEK-Cipher",
    282 			tek + EAP_SAKE_TEK_AUTH_LEN, EAP_SAKE_TEK_CIPHER_LEN);
    283 
    284 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: Root-Secret-B",
    285 			root_secret_b, EAP_SAKE_ROOT_SECRET_LEN);
    286 	eap_sake_kdf(root_secret_b, EAP_SAKE_ROOT_SECRET_LEN,
    287 		     "SAKE Master Secret B",
    288 		     rand_p, EAP_SAKE_RAND_LEN, rand_s, EAP_SAKE_RAND_LEN,
    289 		     sms_b, EAP_SAKE_SMS_LEN);
    290 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: SMS-B", sms_b, EAP_SAKE_SMS_LEN);
    291 	eap_sake_kdf(sms_b, EAP_SAKE_SMS_LEN, "Master Session Key",
    292 		     rand_s, EAP_SAKE_RAND_LEN, rand_p, EAP_SAKE_RAND_LEN,
    293 		     key_buf, sizeof(key_buf));
    294 	os_memcpy(msk, key_buf, EAP_MSK_LEN);
    295 	os_memcpy(emsk, key_buf + EAP_MSK_LEN, EAP_EMSK_LEN);
    296 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: MSK", msk, EAP_MSK_LEN);
    297 	wpa_hexdump_key(MSG_DEBUG, "EAP-SAKE: EMSK", emsk, EAP_EMSK_LEN);
    298 }
    299 
    300 
    301 /**
    302  * eap_sake_compute_mic - Compute EAP-SAKE MIC for an EAP packet
    303  * @tek_auth: 16-byte TEK-Auth
    304  * @rand_s: 16-byte RAND_S
    305  * @rand_p: 16-byte RAND_P
    306  * @serverid: SERVERID
    307  * @serverid_len: SERVERID length
    308  * @peerid: PEERID
    309  * @peerid_len: PEERID length
    310  * @peer: MIC calculation for 0 = Server, 1 = Peer message
    311  * @eap: EAP packet
    312  * @eap_len: EAP packet length
    313  * @mic_pos: MIC position in the EAP packet (must be [eap .. eap + eap_len])
    314  * @mic: Buffer for the computed 16-byte MIC
    315  */
    316 int eap_sake_compute_mic(const u8 *tek_auth,
    317 			 const u8 *rand_s, const u8 *rand_p,
    318 			 const u8 *serverid, size_t serverid_len,
    319 			 const u8 *peerid, size_t peerid_len,
    320 			 int peer, const u8 *eap, size_t eap_len,
    321 			 const u8 *mic_pos, u8 *mic)
    322 {
    323 	u8 _rand[2 * EAP_SAKE_RAND_LEN];
    324 	u8 *tmp, *pos;
    325 	size_t tmplen;
    326 
    327 	tmplen = serverid_len + 1 + peerid_len + 1 + eap_len;
    328 	tmp = os_malloc(tmplen);
    329 	if (tmp == NULL)
    330 		return -1;
    331 	pos = tmp;
    332 	if (peer) {
    333 		if (peerid) {
    334 			os_memcpy(pos, peerid, peerid_len);
    335 			pos += peerid_len;
    336 		}
    337 		*pos++ = 0x00;
    338 		if (serverid) {
    339 			os_memcpy(pos, serverid, serverid_len);
    340 			pos += serverid_len;
    341 		}
    342 		*pos++ = 0x00;
    343 
    344 		os_memcpy(_rand, rand_s, EAP_SAKE_RAND_LEN);
    345 		os_memcpy(_rand + EAP_SAKE_RAND_LEN, rand_p,
    346 			  EAP_SAKE_RAND_LEN);
    347 	} else {
    348 		if (serverid) {
    349 			os_memcpy(pos, serverid, serverid_len);
    350 			pos += serverid_len;
    351 		}
    352 		*pos++ = 0x00;
    353 		if (peerid) {
    354 			os_memcpy(pos, peerid, peerid_len);
    355 			pos += peerid_len;
    356 		}
    357 		*pos++ = 0x00;
    358 
    359 		os_memcpy(_rand, rand_p, EAP_SAKE_RAND_LEN);
    360 		os_memcpy(_rand + EAP_SAKE_RAND_LEN, rand_s,
    361 			  EAP_SAKE_RAND_LEN);
    362 	}
    363 
    364 	os_memcpy(pos, eap, eap_len);
    365 	os_memset(pos + (mic_pos - eap), 0, EAP_SAKE_MIC_LEN);
    366 
    367 	eap_sake_kdf(tek_auth, EAP_SAKE_TEK_AUTH_LEN,
    368 		     peer ? "Peer MIC" : "Server MIC",
    369 		     _rand, 2 * EAP_SAKE_RAND_LEN, tmp, tmplen,
    370 		     mic, EAP_SAKE_MIC_LEN);
    371 
    372 	os_free(tmp);
    373 
    374 	return 0;
    375 }
    376 
    377 
    378 void eap_sake_add_attr(struct wpabuf *buf, u8 type, const u8 *data,
    379 		       size_t len)
    380 {
    381 	wpabuf_put_u8(buf, type);
    382 	wpabuf_put_u8(buf, 2 + len); /* Length; including attr header */
    383 	if (data)
    384 		wpabuf_put_data(buf, data, len);
    385 	else
    386 		os_memset(wpabuf_put(buf, len), 0, len);
    387 }
    388