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 
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 
37 static int chap_gen_challenge(
38 	struct iscsit_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 
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 
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 
131 static void chap_close(struct iscsit_conn *conn)
132 {
133 	kfree(conn->auth_protocol);
134 	conn->auth_protocol = NULL;
135 }
136 
137 static struct iscsi_chap *chap_server_open(
138 	struct iscsit_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 
208 static int chap_server_compute_hash(
209 	struct iscsit_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 
499 u32 chap_main_loop(
500 	struct iscsit_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