Line data Source code
1 : /*
2 : * EAP server/peer: EAP-pwd shared routines
3 : * Copyright (c) 2010, Dan Harkins <dharkins@lounge.org>
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 : #include "common.h"
11 : #include "crypto/sha256.h"
12 : #include "crypto/crypto.h"
13 : #include "eap_defs.h"
14 : #include "eap_pwd_common.h"
15 :
16 : /* The random function H(x) = HMAC-SHA256(0^32, x) */
17 136 : struct crypto_hash * eap_pwd_h_init(void)
18 : {
19 : u8 allzero[SHA256_MAC_LEN];
20 136 : os_memset(allzero, 0, SHA256_MAC_LEN);
21 136 : return crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256, allzero,
22 : SHA256_MAC_LEN);
23 : }
24 :
25 :
26 730 : void eap_pwd_h_update(struct crypto_hash *hash, const u8 *data, size_t len)
27 : {
28 730 : crypto_hash_update(hash, data, len);
29 730 : }
30 :
31 :
32 136 : void eap_pwd_h_final(struct crypto_hash *hash, u8 *digest)
33 : {
34 136 : size_t len = SHA256_MAC_LEN;
35 136 : crypto_hash_finish(hash, digest, &len);
36 136 : }
37 :
38 :
39 : /* a counter-based KDF based on NIST SP800-108 */
40 68 : static int eap_pwd_kdf(const u8 *key, size_t keylen, const u8 *label,
41 : size_t labellen, u8 *result, size_t resultbitlen)
42 : {
43 : struct crypto_hash *hash;
44 : u8 digest[SHA256_MAC_LEN];
45 : u16 i, ctr, L;
46 68 : size_t resultbytelen, len = 0, mdlen;
47 :
48 68 : resultbytelen = (resultbitlen + 7) / 8;
49 68 : ctr = 0;
50 68 : L = htons(resultbitlen);
51 276 : while (len < resultbytelen) {
52 140 : ctr++;
53 140 : i = htons(ctr);
54 140 : hash = crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256,
55 : key, keylen);
56 140 : if (hash == NULL)
57 0 : return -1;
58 140 : if (ctr > 1)
59 72 : crypto_hash_update(hash, digest, SHA256_MAC_LEN);
60 140 : crypto_hash_update(hash, (u8 *) &i, sizeof(u16));
61 140 : crypto_hash_update(hash, label, labellen);
62 140 : crypto_hash_update(hash, (u8 *) &L, sizeof(u16));
63 140 : mdlen = SHA256_MAC_LEN;
64 140 : if (crypto_hash_finish(hash, digest, &mdlen) < 0)
65 0 : return -1;
66 140 : if ((len + mdlen) > resultbytelen)
67 18 : os_memcpy(result + len, digest, resultbytelen - len);
68 : else
69 122 : os_memcpy(result + len, digest, mdlen);
70 140 : len += mdlen;
71 : }
72 :
73 : /* since we're expanding to a bit length, mask off the excess */
74 68 : if (resultbitlen % 8) {
75 2 : u8 mask = 0xff;
76 2 : mask <<= (8 - (resultbitlen % 8));
77 2 : result[resultbytelen - 1] &= mask;
78 : }
79 :
80 68 : return 0;
81 : }
82 :
83 :
84 : /*
85 : * compute a "random" secret point on an elliptic curve based
86 : * on the password and identities.
87 : */
88 25 : int compute_password_element(EAP_PWD_group *grp, u16 num,
89 : u8 *password, int password_len,
90 : u8 *id_server, int id_server_len,
91 : u8 *id_peer, int id_peer_len, u8 *token)
92 : {
93 25 : BIGNUM *x_candidate = NULL, *rnd = NULL, *cofactor = NULL;
94 : struct crypto_hash *hash;
95 25 : unsigned char pwe_digest[SHA256_MAC_LEN], *prfbuf = NULL, ctr;
96 25 : int nid, is_odd, ret = 0;
97 : size_t primebytelen, primebitlen;
98 :
99 25 : switch (num) { /* from IANA registry for IKE D-H groups */
100 : case 19:
101 16 : nid = NID_X9_62_prime256v1;
102 16 : break;
103 : case 20:
104 2 : nid = NID_secp384r1;
105 2 : break;
106 : case 21:
107 2 : nid = NID_secp521r1;
108 2 : break;
109 : #ifndef OPENSSL_IS_BORINGSSL
110 : case 25:
111 2 : nid = NID_X9_62_prime192v1;
112 2 : break;
113 : #endif /* OPENSSL_IS_BORINGSSL */
114 : case 26:
115 2 : nid = NID_secp224r1;
116 2 : break;
117 : default:
118 1 : wpa_printf(MSG_INFO, "EAP-pwd: unsupported group %d", num);
119 1 : return -1;
120 : }
121 :
122 24 : grp->pwe = NULL;
123 24 : grp->order = NULL;
124 24 : grp->prime = NULL;
125 :
126 24 : if ((grp->group = EC_GROUP_new_by_curve_name(nid)) == NULL) {
127 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to create EC_GROUP");
128 0 : goto fail;
129 : }
130 :
131 24 : if (((rnd = BN_new()) == NULL) ||
132 24 : ((cofactor = BN_new()) == NULL) ||
133 48 : ((grp->pwe = EC_POINT_new(grp->group)) == NULL) ||
134 48 : ((grp->order = BN_new()) == NULL) ||
135 48 : ((grp->prime = BN_new()) == NULL) ||
136 : ((x_candidate = BN_new()) == NULL)) {
137 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to create bignums");
138 0 : goto fail;
139 : }
140 :
141 24 : if (!EC_GROUP_get_curve_GFp(grp->group, grp->prime, NULL, NULL, NULL))
142 : {
143 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get prime for GFp "
144 : "curve");
145 0 : goto fail;
146 : }
147 24 : if (!EC_GROUP_get_order(grp->group, grp->order, NULL)) {
148 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get order for curve");
149 0 : goto fail;
150 : }
151 24 : if (!EC_GROUP_get_cofactor(grp->group, cofactor, NULL)) {
152 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get cofactor for "
153 : "curve");
154 0 : goto fail;
155 : }
156 24 : primebitlen = BN_num_bits(grp->prime);
157 24 : primebytelen = BN_num_bytes(grp->prime);
158 24 : if ((prfbuf = os_malloc(primebytelen)) == NULL) {
159 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf "
160 : "buffer");
161 0 : goto fail;
162 : }
163 24 : os_memset(prfbuf, 0, primebytelen);
164 24 : ctr = 0;
165 : while (1) {
166 46 : if (ctr > 30) {
167 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to find random "
168 : "point on curve for group %d, something's "
169 : "fishy", num);
170 0 : goto fail;
171 : }
172 46 : ctr++;
173 :
174 : /*
175 : * compute counter-mode password value and stretch to prime
176 : * pwd-seed = H(token | peer-id | server-id | password |
177 : * counter)
178 : */
179 46 : hash = eap_pwd_h_init();
180 46 : if (hash == NULL)
181 0 : goto fail;
182 46 : eap_pwd_h_update(hash, token, sizeof(u32));
183 46 : eap_pwd_h_update(hash, id_peer, id_peer_len);
184 46 : eap_pwd_h_update(hash, id_server, id_server_len);
185 46 : eap_pwd_h_update(hash, password, password_len);
186 46 : eap_pwd_h_update(hash, &ctr, sizeof(ctr));
187 46 : eap_pwd_h_final(hash, pwe_digest);
188 :
189 46 : BN_bin2bn(pwe_digest, SHA256_MAC_LEN, rnd);
190 :
191 46 : if (eap_pwd_kdf(pwe_digest, SHA256_MAC_LEN,
192 : (u8 *) "EAP-pwd Hunting And Pecking",
193 : os_strlen("EAP-pwd Hunting And Pecking"),
194 : prfbuf, primebitlen) < 0)
195 0 : goto fail;
196 :
197 46 : BN_bin2bn(prfbuf, primebytelen, x_candidate);
198 :
199 : /*
200 : * eap_pwd_kdf() returns a string of bits 0..primebitlen but
201 : * BN_bin2bn will treat that string of bits as a big endian
202 : * number. If the primebitlen is not an even multiple of 8
203 : * then excessive bits-- those _after_ primebitlen-- so now
204 : * we have to shift right the amount we masked off.
205 : */
206 46 : if (primebitlen % 8)
207 2 : BN_rshift(x_candidate, x_candidate,
208 : (8 - (primebitlen % 8)));
209 :
210 46 : if (BN_ucmp(x_candidate, grp->prime) >= 0)
211 0 : continue;
212 :
213 46 : wpa_hexdump(MSG_DEBUG, "EAP-pwd: x_candidate",
214 : prfbuf, primebytelen);
215 :
216 : /*
217 : * need to unambiguously identify the solution, if there is
218 : * one...
219 : */
220 46 : if (BN_is_odd(rnd))
221 25 : is_odd = 1;
222 : else
223 21 : is_odd = 0;
224 :
225 : /*
226 : * solve the quadratic equation, if it's not solvable then we
227 : * don't have a point
228 : */
229 46 : if (!EC_POINT_set_compressed_coordinates_GFp(grp->group,
230 : grp->pwe,
231 : x_candidate,
232 : is_odd, NULL))
233 22 : continue;
234 : /*
235 : * If there's a solution to the equation then the point must be
236 : * on the curve so why check again explicitly? OpenSSL code
237 : * says this is required by X9.62. We're not X9.62 but it can't
238 : * hurt just to be sure.
239 : */
240 24 : if (!EC_POINT_is_on_curve(grp->group, grp->pwe, NULL)) {
241 0 : wpa_printf(MSG_INFO, "EAP-pwd: point is not on curve");
242 0 : continue;
243 : }
244 :
245 24 : if (BN_cmp(cofactor, BN_value_one())) {
246 : /* make sure the point is not in a small sub-group */
247 0 : if (!EC_POINT_mul(grp->group, grp->pwe, NULL, grp->pwe,
248 : cofactor, NULL)) {
249 0 : wpa_printf(MSG_INFO, "EAP-pwd: cannot "
250 : "multiply generator by order");
251 0 : continue;
252 : }
253 0 : if (EC_POINT_is_at_infinity(grp->group, grp->pwe)) {
254 0 : wpa_printf(MSG_INFO, "EAP-pwd: point is at "
255 : "infinity");
256 0 : continue;
257 : }
258 : }
259 : /* if we got here then we have a new generator. */
260 24 : break;
261 22 : }
262 24 : wpa_printf(MSG_DEBUG, "EAP-pwd: found a PWE in %d tries", ctr);
263 24 : grp->group_num = num;
264 : if (0) {
265 : fail:
266 0 : EC_GROUP_free(grp->group);
267 0 : grp->group = NULL;
268 0 : EC_POINT_clear_free(grp->pwe);
269 0 : grp->pwe = NULL;
270 0 : BN_clear_free(grp->order);
271 0 : grp->order = NULL;
272 0 : BN_clear_free(grp->prime);
273 0 : grp->prime = NULL;
274 0 : ret = 1;
275 : }
276 : /* cleanliness and order.... */
277 24 : BN_clear_free(cofactor);
278 24 : BN_clear_free(x_candidate);
279 24 : BN_clear_free(rnd);
280 24 : os_free(prfbuf);
281 :
282 24 : return ret;
283 : }
284 :
285 :
286 22 : int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, BIGNUM *k,
287 : BIGNUM *peer_scalar, BIGNUM *server_scalar,
288 : u8 *confirm_peer, u8 *confirm_server,
289 : u32 *ciphersuite, u8 *msk, u8 *emsk, u8 *session_id)
290 : {
291 : struct crypto_hash *hash;
292 : u8 mk[SHA256_MAC_LEN], *cruft;
293 : u8 msk_emsk[EAP_MSK_LEN + EAP_EMSK_LEN];
294 : int offset;
295 :
296 22 : if ((cruft = os_malloc(BN_num_bytes(grp->prime))) == NULL)
297 0 : return -1;
298 :
299 : /*
300 : * first compute the session-id = TypeCode | H(ciphersuite | scal_p |
301 : * scal_s)
302 : */
303 22 : session_id[0] = EAP_TYPE_PWD;
304 22 : hash = eap_pwd_h_init();
305 22 : if (hash == NULL) {
306 0 : os_free(cruft);
307 0 : return -1;
308 : }
309 22 : eap_pwd_h_update(hash, (u8 *) ciphersuite, sizeof(u32));
310 22 : offset = BN_num_bytes(grp->order) - BN_num_bytes(peer_scalar);
311 22 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
312 22 : BN_bn2bin(peer_scalar, cruft + offset);
313 22 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->order));
314 22 : offset = BN_num_bytes(grp->order) - BN_num_bytes(server_scalar);
315 22 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
316 22 : BN_bn2bin(server_scalar, cruft + offset);
317 22 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->order));
318 22 : eap_pwd_h_final(hash, &session_id[1]);
319 :
320 : /* then compute MK = H(k | confirm-peer | confirm-server) */
321 22 : hash = eap_pwd_h_init();
322 22 : if (hash == NULL) {
323 0 : os_free(cruft);
324 0 : return -1;
325 : }
326 22 : offset = BN_num_bytes(grp->prime) - BN_num_bytes(k);
327 22 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
328 22 : BN_bn2bin(k, cruft + offset);
329 22 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->prime));
330 22 : os_free(cruft);
331 22 : eap_pwd_h_update(hash, confirm_peer, SHA256_MAC_LEN);
332 22 : eap_pwd_h_update(hash, confirm_server, SHA256_MAC_LEN);
333 22 : eap_pwd_h_final(hash, mk);
334 :
335 : /* stretch the mk with the session-id to get MSK | EMSK */
336 22 : if (eap_pwd_kdf(mk, SHA256_MAC_LEN,
337 : session_id, SHA256_MAC_LEN + 1,
338 : msk_emsk, (EAP_MSK_LEN + EAP_EMSK_LEN) * 8) < 0) {
339 0 : return -1;
340 : }
341 :
342 22 : os_memcpy(msk, msk_emsk, EAP_MSK_LEN);
343 22 : os_memcpy(emsk, msk_emsk + EAP_MSK_LEN, EAP_EMSK_LEN);
344 :
345 22 : return 1;
346 : }
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