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) */
17 149 : struct crypto_hash * eap_pwd_h_init(void)
18 : {
19 : u8 allzero[SHA256_MAC_LEN];
20 149 : os_memset(allzero, 0, SHA256_MAC_LEN);
21 149 : return crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256, allzero,
22 : SHA256_MAC_LEN);
23 : }
24 :
25 :
26 803 : void eap_pwd_h_update(struct crypto_hash *hash, const u8 *data, size_t len)
27 : {
28 803 : crypto_hash_update(hash, data, len);
29 803 : }
30 :
31 :
32 149 : void eap_pwd_h_final(struct crypto_hash *hash, u8 *digest)
33 : {
34 149 : size_t len = SHA256_MAC_LEN;
35 149 : crypto_hash_finish(hash, digest, &len);
36 149 : }
37 :
38 :
39 : /* a counter-based KDF based on NIST SP800-108 */
40 69 : 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 69 : size_t resultbytelen, len = 0, mdlen;
47 :
48 69 : resultbytelen = (resultbitlen + 7) / 8;
49 69 : ctr = 0;
50 69 : L = htons(resultbitlen);
51 293 : while (len < resultbytelen) {
52 155 : ctr++;
53 155 : i = htons(ctr);
54 155 : hash = crypto_hash_init(CRYPTO_HASH_ALG_HMAC_SHA256,
55 : key, keylen);
56 155 : if (hash == NULL)
57 0 : return -1;
58 155 : if (ctr > 1)
59 86 : crypto_hash_update(hash, digest, SHA256_MAC_LEN);
60 155 : crypto_hash_update(hash, (u8 *) &i, sizeof(u16));
61 155 : crypto_hash_update(hash, label, labellen);
62 155 : crypto_hash_update(hash, (u8 *) &L, sizeof(u16));
63 155 : mdlen = SHA256_MAC_LEN;
64 155 : if (crypto_hash_finish(hash, digest, &mdlen) < 0)
65 0 : return -1;
66 155 : if ((len + mdlen) > resultbytelen)
67 12 : os_memcpy(result + len, digest, resultbytelen - len);
68 : else
69 143 : os_memcpy(result + len, digest, mdlen);
70 155 : len += mdlen;
71 : }
72 :
73 : /* since we're expanding to a bit length, mask off the excess */
74 69 : if (resultbitlen % 8) {
75 2 : u8 mask = 0xff;
76 2 : mask <<= (8 - (resultbitlen % 8));
77 2 : result[resultbytelen - 1] &= mask;
78 : }
79 :
80 69 : 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 29 : int compute_password_element(EAP_PWD_group *grp, u16 num,
89 : const u8 *password, size_t password_len,
90 : const u8 *id_server, size_t id_server_len,
91 : const u8 *id_peer, size_t id_peer_len,
92 : const u8 *token)
93 : {
94 29 : BIGNUM *x_candidate = NULL, *rnd = NULL, *cofactor = NULL;
95 : struct crypto_hash *hash;
96 29 : unsigned char pwe_digest[SHA256_MAC_LEN], *prfbuf = NULL, ctr;
97 29 : int nid, is_odd, ret = 0;
98 : size_t primebytelen, primebitlen;
99 :
100 29 : switch (num) { /* from IANA registry for IKE D-H groups */
101 : case 19:
102 20 : nid = NID_X9_62_prime256v1;
103 20 : break;
104 : case 20:
105 2 : nid = NID_secp384r1;
106 2 : break;
107 : case 21:
108 2 : nid = NID_secp521r1;
109 2 : break;
110 : #ifndef OPENSSL_IS_BORINGSSL
111 : case 25:
112 2 : nid = NID_X9_62_prime192v1;
113 2 : break;
114 : #endif /* OPENSSL_IS_BORINGSSL */
115 : case 26:
116 2 : nid = NID_secp224r1;
117 2 : break;
118 : default:
119 1 : wpa_printf(MSG_INFO, "EAP-pwd: unsupported group %d", num);
120 1 : return -1;
121 : }
122 :
123 28 : grp->pwe = NULL;
124 28 : grp->order = NULL;
125 28 : grp->prime = NULL;
126 :
127 28 : if ((grp->group = EC_GROUP_new_by_curve_name(nid)) == NULL) {
128 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to create EC_GROUP");
129 0 : goto fail;
130 : }
131 :
132 28 : if (((rnd = BN_new()) == NULL) ||
133 28 : ((cofactor = BN_new()) == NULL) ||
134 56 : ((grp->pwe = EC_POINT_new(grp->group)) == NULL) ||
135 56 : ((grp->order = BN_new()) == NULL) ||
136 56 : ((grp->prime = BN_new()) == NULL) ||
137 : ((x_candidate = BN_new()) == NULL)) {
138 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to create bignums");
139 0 : goto fail;
140 : }
141 :
142 28 : if (!EC_GROUP_get_curve_GFp(grp->group, grp->prime, NULL, NULL, NULL))
143 : {
144 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get prime for GFp "
145 : "curve");
146 0 : goto fail;
147 : }
148 28 : if (!EC_GROUP_get_order(grp->group, grp->order, NULL)) {
149 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get order for curve");
150 0 : goto fail;
151 : }
152 28 : if (!EC_GROUP_get_cofactor(grp->group, cofactor, NULL)) {
153 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to get cofactor for "
154 : "curve");
155 0 : goto fail;
156 : }
157 28 : primebitlen = BN_num_bits(grp->prime);
158 28 : primebytelen = BN_num_bytes(grp->prime);
159 28 : if ((prfbuf = os_malloc(primebytelen)) == NULL) {
160 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf "
161 : "buffer");
162 0 : goto fail;
163 : }
164 28 : os_memset(prfbuf, 0, primebytelen);
165 28 : ctr = 0;
166 : while (1) {
167 43 : if (ctr > 30) {
168 0 : wpa_printf(MSG_INFO, "EAP-pwd: unable to find random "
169 : "point on curve for group %d, something's "
170 : "fishy", num);
171 0 : goto fail;
172 : }
173 43 : ctr++;
174 :
175 : /*
176 : * compute counter-mode password value and stretch to prime
177 : * pwd-seed = H(token | peer-id | server-id | password |
178 : * counter)
179 : */
180 43 : hash = eap_pwd_h_init();
181 43 : if (hash == NULL)
182 0 : goto fail;
183 43 : eap_pwd_h_update(hash, token, sizeof(u32));
184 43 : eap_pwd_h_update(hash, id_peer, id_peer_len);
185 43 : eap_pwd_h_update(hash, id_server, id_server_len);
186 43 : eap_pwd_h_update(hash, password, password_len);
187 43 : eap_pwd_h_update(hash, &ctr, sizeof(ctr));
188 43 : eap_pwd_h_final(hash, pwe_digest);
189 :
190 43 : BN_bin2bn(pwe_digest, SHA256_MAC_LEN, rnd);
191 :
192 43 : if (eap_pwd_kdf(pwe_digest, SHA256_MAC_LEN,
193 : (u8 *) "EAP-pwd Hunting And Pecking",
194 : os_strlen("EAP-pwd Hunting And Pecking"),
195 : prfbuf, primebitlen) < 0)
196 0 : goto fail;
197 :
198 43 : BN_bin2bn(prfbuf, primebytelen, x_candidate);
199 :
200 : /*
201 : * eap_pwd_kdf() returns a string of bits 0..primebitlen but
202 : * BN_bin2bn will treat that string of bits as a big endian
203 : * number. If the primebitlen is not an even multiple of 8
204 : * then excessive bits-- those _after_ primebitlen-- so now
205 : * we have to shift right the amount we masked off.
206 : */
207 43 : if (primebitlen % 8)
208 2 : BN_rshift(x_candidate, x_candidate,
209 : (8 - (primebitlen % 8)));
210 :
211 43 : if (BN_ucmp(x_candidate, grp->prime) >= 0)
212 0 : continue;
213 :
214 43 : wpa_hexdump(MSG_DEBUG, "EAP-pwd: x_candidate",
215 : prfbuf, primebytelen);
216 :
217 : /*
218 : * need to unambiguously identify the solution, if there is
219 : * one...
220 : */
221 43 : if (BN_is_odd(rnd))
222 26 : is_odd = 1;
223 : else
224 17 : is_odd = 0;
225 :
226 : /*
227 : * solve the quadratic equation, if it's not solvable then we
228 : * don't have a point
229 : */
230 43 : if (!EC_POINT_set_compressed_coordinates_GFp(grp->group,
231 : grp->pwe,
232 : x_candidate,
233 : is_odd, NULL))
234 15 : continue;
235 : /*
236 : * If there's a solution to the equation then the point must be
237 : * on the curve so why check again explicitly? OpenSSL code
238 : * says this is required by X9.62. We're not X9.62 but it can't
239 : * hurt just to be sure.
240 : */
241 28 : if (!EC_POINT_is_on_curve(grp->group, grp->pwe, NULL)) {
242 0 : wpa_printf(MSG_INFO, "EAP-pwd: point is not on curve");
243 0 : continue;
244 : }
245 :
246 28 : if (BN_cmp(cofactor, BN_value_one())) {
247 : /* make sure the point is not in a small sub-group */
248 0 : if (!EC_POINT_mul(grp->group, grp->pwe, NULL, grp->pwe,
249 : cofactor, NULL)) {
250 0 : wpa_printf(MSG_INFO, "EAP-pwd: cannot "
251 : "multiply generator by order");
252 0 : continue;
253 : }
254 0 : if (EC_POINT_is_at_infinity(grp->group, grp->pwe)) {
255 0 : wpa_printf(MSG_INFO, "EAP-pwd: point is at "
256 : "infinity");
257 0 : continue;
258 : }
259 : }
260 : /* if we got here then we have a new generator. */
261 28 : break;
262 15 : }
263 28 : wpa_printf(MSG_DEBUG, "EAP-pwd: found a PWE in %d tries", ctr);
264 28 : grp->group_num = num;
265 : if (0) {
266 : fail:
267 0 : EC_GROUP_free(grp->group);
268 0 : grp->group = NULL;
269 0 : EC_POINT_clear_free(grp->pwe);
270 0 : grp->pwe = NULL;
271 0 : BN_clear_free(grp->order);
272 0 : grp->order = NULL;
273 0 : BN_clear_free(grp->prime);
274 0 : grp->prime = NULL;
275 0 : ret = 1;
276 : }
277 : /* cleanliness and order.... */
278 28 : BN_clear_free(cofactor);
279 28 : BN_clear_free(x_candidate);
280 28 : BN_clear_free(rnd);
281 28 : os_free(prfbuf);
282 :
283 28 : return ret;
284 : }
285 :
286 :
287 26 : int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, const BIGNUM *k,
288 : const BIGNUM *peer_scalar, const BIGNUM *server_scalar,
289 : const u8 *confirm_peer, const u8 *confirm_server,
290 : const u32 *ciphersuite, u8 *msk, u8 *emsk, u8 *session_id)
291 : {
292 : struct crypto_hash *hash;
293 : u8 mk[SHA256_MAC_LEN], *cruft;
294 : u8 msk_emsk[EAP_MSK_LEN + EAP_EMSK_LEN];
295 : int offset;
296 :
297 26 : if ((cruft = os_malloc(BN_num_bytes(grp->prime))) == NULL)
298 0 : return -1;
299 :
300 : /*
301 : * first compute the session-id = TypeCode | H(ciphersuite | scal_p |
302 : * scal_s)
303 : */
304 26 : session_id[0] = EAP_TYPE_PWD;
305 26 : hash = eap_pwd_h_init();
306 26 : if (hash == NULL) {
307 0 : os_free(cruft);
308 0 : return -1;
309 : }
310 26 : eap_pwd_h_update(hash, (const u8 *) ciphersuite, sizeof(u32));
311 26 : offset = BN_num_bytes(grp->order) - BN_num_bytes(peer_scalar);
312 26 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
313 26 : BN_bn2bin(peer_scalar, cruft + offset);
314 26 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->order));
315 26 : offset = BN_num_bytes(grp->order) - BN_num_bytes(server_scalar);
316 26 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
317 26 : BN_bn2bin(server_scalar, cruft + offset);
318 26 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->order));
319 26 : eap_pwd_h_final(hash, &session_id[1]);
320 :
321 : /* then compute MK = H(k | confirm-peer | confirm-server) */
322 26 : hash = eap_pwd_h_init();
323 26 : if (hash == NULL) {
324 0 : os_free(cruft);
325 0 : return -1;
326 : }
327 26 : offset = BN_num_bytes(grp->prime) - BN_num_bytes(k);
328 26 : os_memset(cruft, 0, BN_num_bytes(grp->prime));
329 26 : BN_bn2bin(k, cruft + offset);
330 26 : eap_pwd_h_update(hash, cruft, BN_num_bytes(grp->prime));
331 26 : os_free(cruft);
332 26 : eap_pwd_h_update(hash, confirm_peer, SHA256_MAC_LEN);
333 26 : eap_pwd_h_update(hash, confirm_server, SHA256_MAC_LEN);
334 26 : eap_pwd_h_final(hash, mk);
335 :
336 : /* stretch the mk with the session-id to get MSK | EMSK */
337 26 : if (eap_pwd_kdf(mk, SHA256_MAC_LEN,
338 : session_id, SHA256_MAC_LEN + 1,
339 : msk_emsk, (EAP_MSK_LEN + EAP_EMSK_LEN) * 8) < 0) {
340 0 : return -1;
341 : }
342 :
343 26 : os_memcpy(msk, msk_emsk, EAP_MSK_LEN);
344 26 : os_memcpy(emsk, msk_emsk + EAP_MSK_LEN, EAP_EMSK_LEN);
345 :
346 26 : return 1;
347 : }
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