1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*******************************************************************************
3 * This file houses the main functions for the iSCSI CHAP support
4 *
5 * (c) Copyright 2007-2013 Datera, Inc.
6 *
7 * Author: Nicholas A. Bellinger <nab@linux-iscsi.org>
8 *
9 ******************************************************************************/
10
11 #include <crypto/hash.h>
12 #include <linux/kernel.h>
13 #include <linux/string.h>
14 #include <linux/err.h>
15 #include <linux/random.h>
16 #include <linux/scatterlist.h>
17 #include <target/iscsi/iscsi_target_core.h>
18 #include "iscsi_target_nego.h"
19 #include "iscsi_target_auth.h"
20
chap_get_digest_name(const int digest_type)21 static char *chap_get_digest_name(const int digest_type)
22 {
23 switch (digest_type) {
24 case CHAP_DIGEST_MD5:
25 return "md5";
26 case CHAP_DIGEST_SHA1:
27 return "sha1";
28 case CHAP_DIGEST_SHA256:
29 return "sha256";
30 case CHAP_DIGEST_SHA3_256:
31 return "sha3-256";
32 default:
33 return NULL;
34 }
35 }
36
chap_gen_challenge(struct iscsi_conn * conn,int caller,char * c_str,unsigned int * c_len)37 static int chap_gen_challenge(
38 struct iscsi_conn *conn,
39 int caller,
40 char *c_str,
41 unsigned int *c_len)
42 {
43 int ret;
44 unsigned char *challenge_asciihex;
45 struct iscsi_chap *chap = conn->auth_protocol;
46
47 challenge_asciihex = kzalloc(chap->challenge_len * 2 + 1, GFP_KERNEL);
48 if (!challenge_asciihex)
49 return -ENOMEM;
50
51 memset(chap->challenge, 0, MAX_CHAP_CHALLENGE_LEN);
52
53 ret = get_random_bytes_wait(chap->challenge, chap->challenge_len);
54 if (unlikely(ret))
55 goto out;
56
57 bin2hex(challenge_asciihex, chap->challenge,
58 chap->challenge_len);
59 /*
60 * Set CHAP_C, and copy the generated challenge into c_str.
61 */
62 *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
63 *c_len += 1;
64
65 pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
66 challenge_asciihex);
67
68 out:
69 kfree(challenge_asciihex);
70 return ret;
71 }
72
chap_test_algorithm(const char * name)73 static int chap_test_algorithm(const char *name)
74 {
75 struct crypto_shash *tfm;
76
77 tfm = crypto_alloc_shash(name, 0, 0);
78 if (IS_ERR(tfm))
79 return -1;
80
81 crypto_free_shash(tfm);
82 return 0;
83 }
84
chap_check_algorithm(const char * a_str)85 static int chap_check_algorithm(const char *a_str)
86 {
87 char *tmp, *orig, *token, *digest_name;
88 long digest_type;
89 int r = CHAP_DIGEST_UNKNOWN;
90
91 tmp = kstrdup(a_str, GFP_KERNEL);
92 if (!tmp) {
93 pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
94 return CHAP_DIGEST_UNKNOWN;
95 }
96 orig = tmp;
97
98 token = strsep(&tmp, "=");
99 if (!token)
100 goto out;
101
102 if (strcmp(token, "CHAP_A")) {
103 pr_err("Unable to locate CHAP_A key\n");
104 goto out;
105 }
106 while (token) {
107 token = strsep(&tmp, ",");
108 if (!token)
109 goto out;
110
111 if (kstrtol(token, 10, &digest_type))
112 continue;
113
114 digest_name = chap_get_digest_name(digest_type);
115 if (!digest_name)
116 continue;
117
118 pr_debug("Selected %s Algorithm\n", digest_name);
119 if (chap_test_algorithm(digest_name) < 0) {
120 pr_err("failed to allocate %s algo\n", digest_name);
121 } else {
122 r = digest_type;
123 goto out;
124 }
125 }
126 out:
127 kfree(orig);
128 return r;
129 }
130
chap_close(struct iscsi_conn * conn)131 static void chap_close(struct iscsi_conn *conn)
132 {
133 kfree(conn->auth_protocol);
134 conn->auth_protocol = NULL;
135 }
136
chap_server_open(struct iscsi_conn * conn,struct iscsi_node_auth * auth,const char * a_str,char * aic_str,unsigned int * aic_len)137 static struct iscsi_chap *chap_server_open(
138 struct iscsi_conn *conn,
139 struct iscsi_node_auth *auth,
140 const char *a_str,
141 char *aic_str,
142 unsigned int *aic_len)
143 {
144 int digest_type;
145 struct iscsi_chap *chap;
146
147 if (!(auth->naf_flags & NAF_USERID_SET) ||
148 !(auth->naf_flags & NAF_PASSWORD_SET)) {
149 pr_err("CHAP user or password not set for"
150 " Initiator ACL\n");
151 return NULL;
152 }
153
154 conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
155 if (!conn->auth_protocol)
156 return NULL;
157
158 chap = conn->auth_protocol;
159 digest_type = chap_check_algorithm(a_str);
160 switch (digest_type) {
161 case CHAP_DIGEST_MD5:
162 chap->digest_size = MD5_SIGNATURE_SIZE;
163 break;
164 case CHAP_DIGEST_SHA1:
165 chap->digest_size = SHA1_SIGNATURE_SIZE;
166 break;
167 case CHAP_DIGEST_SHA256:
168 chap->digest_size = SHA256_SIGNATURE_SIZE;
169 break;
170 case CHAP_DIGEST_SHA3_256:
171 chap->digest_size = SHA3_256_SIGNATURE_SIZE;
172 break;
173 case CHAP_DIGEST_UNKNOWN:
174 default:
175 pr_err("Unsupported CHAP_A value\n");
176 chap_close(conn);
177 return NULL;
178 }
179
180 chap->digest_name = chap_get_digest_name(digest_type);
181
182 /* Tie the challenge length to the digest size */
183 chap->challenge_len = chap->digest_size;
184
185 pr_debug("[server] Got CHAP_A=%d\n", digest_type);
186 *aic_len = sprintf(aic_str, "CHAP_A=%d", digest_type);
187 *aic_len += 1;
188 pr_debug("[server] Sending CHAP_A=%d\n", digest_type);
189
190 /*
191 * Set Identifier.
192 */
193 chap->id = conn->tpg->tpg_chap_id++;
194 *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
195 *aic_len += 1;
196 pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
197 /*
198 * Generate Challenge.
199 */
200 if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) {
201 chap_close(conn);
202 return NULL;
203 }
204
205 return chap;
206 }
207
chap_server_compute_hash(struct iscsi_conn * conn,struct iscsi_node_auth * auth,char * nr_in_ptr,char * nr_out_ptr,unsigned int * nr_out_len)208 static int chap_server_compute_hash(
209 struct iscsi_conn *conn,
210 struct iscsi_node_auth *auth,
211 char *nr_in_ptr,
212 char *nr_out_ptr,
213 unsigned int *nr_out_len)
214 {
215 unsigned long id;
216 unsigned char id_as_uchar;
217 unsigned char type;
218 unsigned char identifier[10], *initiatorchg = NULL;
219 unsigned char *initiatorchg_binhex = NULL;
220 unsigned char *digest = NULL;
221 unsigned char *response = NULL;
222 unsigned char *client_digest = NULL;
223 unsigned char *server_digest = NULL;
224 unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
225 size_t compare_len;
226 struct iscsi_chap *chap = conn->auth_protocol;
227 struct crypto_shash *tfm = NULL;
228 struct shash_desc *desc = NULL;
229 int auth_ret = -1, ret, initiatorchg_len;
230
231 digest = kzalloc(chap->digest_size, GFP_KERNEL);
232 if (!digest) {
233 pr_err("Unable to allocate the digest buffer\n");
234 goto out;
235 }
236
237 response = kzalloc(chap->digest_size * 2 + 2, GFP_KERNEL);
238 if (!response) {
239 pr_err("Unable to allocate the response buffer\n");
240 goto out;
241 }
242
243 client_digest = kzalloc(chap->digest_size, GFP_KERNEL);
244 if (!client_digest) {
245 pr_err("Unable to allocate the client_digest buffer\n");
246 goto out;
247 }
248
249 server_digest = kzalloc(chap->digest_size, GFP_KERNEL);
250 if (!server_digest) {
251 pr_err("Unable to allocate the server_digest buffer\n");
252 goto out;
253 }
254
255 memset(identifier, 0, 10);
256 memset(chap_n, 0, MAX_CHAP_N_SIZE);
257 memset(chap_r, 0, MAX_RESPONSE_LENGTH);
258
259 initiatorchg = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
260 if (!initiatorchg) {
261 pr_err("Unable to allocate challenge buffer\n");
262 goto out;
263 }
264
265 initiatorchg_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
266 if (!initiatorchg_binhex) {
267 pr_err("Unable to allocate initiatorchg_binhex buffer\n");
268 goto out;
269 }
270 /*
271 * Extract CHAP_N.
272 */
273 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
274 &type) < 0) {
275 pr_err("Could not find CHAP_N.\n");
276 goto out;
277 }
278 if (type == HEX) {
279 pr_err("Could not find CHAP_N.\n");
280 goto out;
281 }
282
283 /* Include the terminating NULL in the compare */
284 compare_len = strlen(auth->userid) + 1;
285 if (strncmp(chap_n, auth->userid, compare_len) != 0) {
286 pr_err("CHAP_N values do not match!\n");
287 goto out;
288 }
289 pr_debug("[server] Got CHAP_N=%s\n", chap_n);
290 /*
291 * Extract CHAP_R.
292 */
293 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
294 &type) < 0) {
295 pr_err("Could not find CHAP_R.\n");
296 goto out;
297 }
298 if (type != HEX) {
299 pr_err("Could not find CHAP_R.\n");
300 goto out;
301 }
302 if (strlen(chap_r) != chap->digest_size * 2) {
303 pr_err("Malformed CHAP_R\n");
304 goto out;
305 }
306 if (hex2bin(client_digest, chap_r, chap->digest_size) < 0) {
307 pr_err("Malformed CHAP_R\n");
308 goto out;
309 }
310
311 pr_debug("[server] Got CHAP_R=%s\n", chap_r);
312
313 tfm = crypto_alloc_shash(chap->digest_name, 0, 0);
314 if (IS_ERR(tfm)) {
315 tfm = NULL;
316 pr_err("Unable to allocate struct crypto_shash\n");
317 goto out;
318 }
319
320 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
321 if (!desc) {
322 pr_err("Unable to allocate struct shash_desc\n");
323 goto out;
324 }
325
326 desc->tfm = tfm;
327
328 ret = crypto_shash_init(desc);
329 if (ret < 0) {
330 pr_err("crypto_shash_init() failed\n");
331 goto out;
332 }
333
334 ret = crypto_shash_update(desc, &chap->id, 1);
335 if (ret < 0) {
336 pr_err("crypto_shash_update() failed for id\n");
337 goto out;
338 }
339
340 ret = crypto_shash_update(desc, (char *)&auth->password,
341 strlen(auth->password));
342 if (ret < 0) {
343 pr_err("crypto_shash_update() failed for password\n");
344 goto out;
345 }
346
347 ret = crypto_shash_finup(desc, chap->challenge,
348 chap->challenge_len, server_digest);
349 if (ret < 0) {
350 pr_err("crypto_shash_finup() failed for challenge\n");
351 goto out;
352 }
353
354 bin2hex(response, server_digest, chap->digest_size);
355 pr_debug("[server] %s Server Digest: %s\n",
356 chap->digest_name, response);
357
358 if (memcmp(server_digest, client_digest, chap->digest_size) != 0) {
359 pr_debug("[server] %s Digests do not match!\n\n",
360 chap->digest_name);
361 goto out;
362 } else
363 pr_debug("[server] %s Digests match, CHAP connection"
364 " successful.\n\n", chap->digest_name);
365 /*
366 * One way authentication has succeeded, return now if mutual
367 * authentication is not enabled.
368 */
369 if (!auth->authenticate_target) {
370 auth_ret = 0;
371 goto out;
372 }
373 /*
374 * Get CHAP_I.
375 */
376 if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
377 pr_err("Could not find CHAP_I.\n");
378 goto out;
379 }
380
381 if (type == HEX)
382 ret = kstrtoul(&identifier[2], 0, &id);
383 else
384 ret = kstrtoul(identifier, 0, &id);
385
386 if (ret < 0) {
387 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
388 goto out;
389 }
390 if (id > 255) {
391 pr_err("chap identifier: %lu greater than 255\n", id);
392 goto out;
393 }
394 /*
395 * RFC 1994 says Identifier is no more than octet (8 bits).
396 */
397 pr_debug("[server] Got CHAP_I=%lu\n", id);
398 /*
399 * Get CHAP_C.
400 */
401 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
402 initiatorchg, &type) < 0) {
403 pr_err("Could not find CHAP_C.\n");
404 goto out;
405 }
406
407 if (type != HEX) {
408 pr_err("Could not find CHAP_C.\n");
409 goto out;
410 }
411 initiatorchg_len = DIV_ROUND_UP(strlen(initiatorchg), 2);
412 if (!initiatorchg_len) {
413 pr_err("Unable to convert incoming challenge\n");
414 goto out;
415 }
416 if (initiatorchg_len > 1024) {
417 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
418 goto out;
419 }
420 if (hex2bin(initiatorchg_binhex, initiatorchg, initiatorchg_len) < 0) {
421 pr_err("Malformed CHAP_C\n");
422 goto out;
423 }
424 pr_debug("[server] Got CHAP_C=%s\n", initiatorchg);
425 /*
426 * During mutual authentication, the CHAP_C generated by the
427 * initiator must not match the original CHAP_C generated by
428 * the target.
429 */
430 if (initiatorchg_len == chap->challenge_len &&
431 !memcmp(initiatorchg_binhex, chap->challenge,
432 initiatorchg_len)) {
433 pr_err("initiator CHAP_C matches target CHAP_C, failing"
434 " login attempt\n");
435 goto out;
436 }
437 /*
438 * Generate CHAP_N and CHAP_R for mutual authentication.
439 */
440 ret = crypto_shash_init(desc);
441 if (ret < 0) {
442 pr_err("crypto_shash_init() failed\n");
443 goto out;
444 }
445
446 /* To handle both endiannesses */
447 id_as_uchar = id;
448 ret = crypto_shash_update(desc, &id_as_uchar, 1);
449 if (ret < 0) {
450 pr_err("crypto_shash_update() failed for id\n");
451 goto out;
452 }
453
454 ret = crypto_shash_update(desc, auth->password_mutual,
455 strlen(auth->password_mutual));
456 if (ret < 0) {
457 pr_err("crypto_shash_update() failed for"
458 " password_mutual\n");
459 goto out;
460 }
461 /*
462 * Convert received challenge to binary hex.
463 */
464 ret = crypto_shash_finup(desc, initiatorchg_binhex, initiatorchg_len,
465 digest);
466 if (ret < 0) {
467 pr_err("crypto_shash_finup() failed for ma challenge\n");
468 goto out;
469 }
470
471 /*
472 * Generate CHAP_N and CHAP_R.
473 */
474 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
475 *nr_out_len += 1;
476 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
477 /*
478 * Convert response from binary hex to ascii hext.
479 */
480 bin2hex(response, digest, chap->digest_size);
481 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
482 response);
483 *nr_out_len += 1;
484 pr_debug("[server] Sending CHAP_R=0x%s\n", response);
485 auth_ret = 0;
486 out:
487 kfree_sensitive(desc);
488 if (tfm)
489 crypto_free_shash(tfm);
490 kfree(initiatorchg);
491 kfree(initiatorchg_binhex);
492 kfree(digest);
493 kfree(response);
494 kfree(server_digest);
495 kfree(client_digest);
496 return auth_ret;
497 }
498
chap_main_loop(struct iscsi_conn * conn,struct iscsi_node_auth * auth,char * in_text,char * out_text,int * in_len,int * out_len)499 u32 chap_main_loop(
500 struct iscsi_conn *conn,
501 struct iscsi_node_auth *auth,
502 char *in_text,
503 char *out_text,
504 int *in_len,
505 int *out_len)
506 {
507 struct iscsi_chap *chap = conn->auth_protocol;
508
509 if (!chap) {
510 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
511 if (!chap)
512 return 2;
513 chap->chap_state = CHAP_STAGE_SERVER_AIC;
514 return 0;
515 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
516 convert_null_to_semi(in_text, *in_len);
517 if (chap_server_compute_hash(conn, auth, in_text, out_text,
518 out_len) < 0) {
519 chap_close(conn);
520 return 2;
521 }
522 if (auth->authenticate_target)
523 chap->chap_state = CHAP_STAGE_SERVER_NR;
524 else
525 *out_len = 0;
526 chap_close(conn);
527 return 1;
528 }
529
530 return 2;
531 }
532