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 const char base64_lookup_table[] =
209 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
210 
211 static int chap_base64_decode(u8 *dst, const char *src, size_t len)
212 {
213 	int i, bits = 0, ac = 0;
214 	const char *p;
215 	u8 *cp = dst;
216 
217 	for (i = 0; i < len; i++) {
218 		if (src[i] == '=')
219 			return cp - dst;
220 
221 		p = strchr(base64_lookup_table, src[i]);
222 		if (p == NULL || src[i] == 0)
223 			return -2;
224 
225 		ac <<= 6;
226 		ac += (p - base64_lookup_table);
227 		bits += 6;
228 		if (bits >= 8) {
229 			*cp++ = (ac >> (bits - 8)) & 0xff;
230 			ac &= ~(BIT(16) - BIT(bits - 8));
231 			bits -= 8;
232 		}
233 	}
234 	if (ac)
235 		return -1;
236 
237 	return cp - dst;
238 }
239 
240 static int chap_server_compute_hash(
241 	struct iscsit_conn *conn,
242 	struct iscsi_node_auth *auth,
243 	char *nr_in_ptr,
244 	char *nr_out_ptr,
245 	unsigned int *nr_out_len)
246 {
247 	unsigned long id;
248 	unsigned char id_as_uchar;
249 	unsigned char type;
250 	unsigned char identifier[10], *initiatorchg = NULL;
251 	unsigned char *initiatorchg_binhex = NULL;
252 	unsigned char *digest = NULL;
253 	unsigned char *response = NULL;
254 	unsigned char *client_digest = NULL;
255 	unsigned char *server_digest = NULL;
256 	unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
257 	size_t compare_len;
258 	struct iscsi_chap *chap = conn->auth_protocol;
259 	struct crypto_shash *tfm = NULL;
260 	struct shash_desc *desc = NULL;
261 	int auth_ret = -1, ret, initiatorchg_len;
262 
263 	digest = kzalloc(chap->digest_size, GFP_KERNEL);
264 	if (!digest) {
265 		pr_err("Unable to allocate the digest buffer\n");
266 		goto out;
267 	}
268 
269 	response = kzalloc(chap->digest_size * 2 + 2, GFP_KERNEL);
270 	if (!response) {
271 		pr_err("Unable to allocate the response buffer\n");
272 		goto out;
273 	}
274 
275 	client_digest = kzalloc(chap->digest_size, GFP_KERNEL);
276 	if (!client_digest) {
277 		pr_err("Unable to allocate the client_digest buffer\n");
278 		goto out;
279 	}
280 
281 	server_digest = kzalloc(chap->digest_size, GFP_KERNEL);
282 	if (!server_digest) {
283 		pr_err("Unable to allocate the server_digest buffer\n");
284 		goto out;
285 	}
286 
287 	memset(identifier, 0, 10);
288 	memset(chap_n, 0, MAX_CHAP_N_SIZE);
289 	memset(chap_r, 0, MAX_RESPONSE_LENGTH);
290 
291 	initiatorchg = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
292 	if (!initiatorchg) {
293 		pr_err("Unable to allocate challenge buffer\n");
294 		goto out;
295 	}
296 
297 	initiatorchg_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
298 	if (!initiatorchg_binhex) {
299 		pr_err("Unable to allocate initiatorchg_binhex buffer\n");
300 		goto out;
301 	}
302 	/*
303 	 * Extract CHAP_N.
304 	 */
305 	if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
306 				&type) < 0) {
307 		pr_err("Could not find CHAP_N.\n");
308 		goto out;
309 	}
310 	if (type == HEX) {
311 		pr_err("Could not find CHAP_N.\n");
312 		goto out;
313 	}
314 
315 	/* Include the terminating NULL in the compare */
316 	compare_len = strlen(auth->userid) + 1;
317 	if (strncmp(chap_n, auth->userid, compare_len) != 0) {
318 		pr_err("CHAP_N values do not match!\n");
319 		goto out;
320 	}
321 	pr_debug("[server] Got CHAP_N=%s\n", chap_n);
322 	/*
323 	 * Extract CHAP_R.
324 	 */
325 	if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
326 				&type) < 0) {
327 		pr_err("Could not find CHAP_R.\n");
328 		goto out;
329 	}
330 
331 	switch (type) {
332 	case HEX:
333 		if (strlen(chap_r) != chap->digest_size * 2) {
334 			pr_err("Malformed CHAP_R\n");
335 			goto out;
336 		}
337 		if (hex2bin(client_digest, chap_r, chap->digest_size) < 0) {
338 			pr_err("Malformed CHAP_R: invalid HEX\n");
339 			goto out;
340 		}
341 		break;
342 	case BASE64:
343 		if (chap_base64_decode(client_digest, chap_r, strlen(chap_r)) !=
344 		    chap->digest_size) {
345 			pr_err("Malformed CHAP_R: invalid BASE64\n");
346 			goto out;
347 		}
348 		break;
349 	default:
350 		pr_err("Could not find CHAP_R\n");
351 		goto out;
352 	}
353 
354 	pr_debug("[server] Got CHAP_R=%s\n", chap_r);
355 
356 	tfm = crypto_alloc_shash(chap->digest_name, 0, 0);
357 	if (IS_ERR(tfm)) {
358 		tfm = NULL;
359 		pr_err("Unable to allocate struct crypto_shash\n");
360 		goto out;
361 	}
362 
363 	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
364 	if (!desc) {
365 		pr_err("Unable to allocate struct shash_desc\n");
366 		goto out;
367 	}
368 
369 	desc->tfm = tfm;
370 
371 	ret = crypto_shash_init(desc);
372 	if (ret < 0) {
373 		pr_err("crypto_shash_init() failed\n");
374 		goto out;
375 	}
376 
377 	ret = crypto_shash_update(desc, &chap->id, 1);
378 	if (ret < 0) {
379 		pr_err("crypto_shash_update() failed for id\n");
380 		goto out;
381 	}
382 
383 	ret = crypto_shash_update(desc, (char *)&auth->password,
384 				  strlen(auth->password));
385 	if (ret < 0) {
386 		pr_err("crypto_shash_update() failed for password\n");
387 		goto out;
388 	}
389 
390 	ret = crypto_shash_finup(desc, chap->challenge,
391 				 chap->challenge_len, server_digest);
392 	if (ret < 0) {
393 		pr_err("crypto_shash_finup() failed for challenge\n");
394 		goto out;
395 	}
396 
397 	bin2hex(response, server_digest, chap->digest_size);
398 	pr_debug("[server] %s Server Digest: %s\n",
399 		chap->digest_name, response);
400 
401 	if (memcmp(server_digest, client_digest, chap->digest_size) != 0) {
402 		pr_debug("[server] %s Digests do not match!\n\n",
403 			chap->digest_name);
404 		goto out;
405 	} else
406 		pr_debug("[server] %s Digests match, CHAP connection"
407 				" successful.\n\n", chap->digest_name);
408 	/*
409 	 * One way authentication has succeeded, return now if mutual
410 	 * authentication is not enabled.
411 	 */
412 	if (!auth->authenticate_target) {
413 		auth_ret = 0;
414 		goto out;
415 	}
416 	/*
417 	 * Get CHAP_I.
418 	 */
419 	ret = extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type);
420 	if (ret == -ENOENT) {
421 		pr_debug("Could not find CHAP_I. Initiator uses One way authentication.\n");
422 		auth_ret = 0;
423 		goto out;
424 	}
425 	if (ret < 0) {
426 		pr_err("Could not find CHAP_I.\n");
427 		goto out;
428 	}
429 
430 	if (type == HEX)
431 		ret = kstrtoul(&identifier[2], 0, &id);
432 	else
433 		ret = kstrtoul(identifier, 0, &id);
434 
435 	if (ret < 0) {
436 		pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
437 		goto out;
438 	}
439 	if (id > 255) {
440 		pr_err("chap identifier: %lu greater than 255\n", id);
441 		goto out;
442 	}
443 	/*
444 	 * RFC 1994 says Identifier is no more than octet (8 bits).
445 	 */
446 	pr_debug("[server] Got CHAP_I=%lu\n", id);
447 	/*
448 	 * Get CHAP_C.
449 	 */
450 	if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
451 			initiatorchg, &type) < 0) {
452 		pr_err("Could not find CHAP_C.\n");
453 		goto out;
454 	}
455 
456 	switch (type) {
457 	case HEX:
458 		initiatorchg_len = DIV_ROUND_UP(strlen(initiatorchg), 2);
459 		if (!initiatorchg_len) {
460 			pr_err("Unable to convert incoming challenge\n");
461 			goto out;
462 		}
463 		if (initiatorchg_len > 1024) {
464 			pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
465 			goto out;
466 		}
467 
468 		if (hex2bin(initiatorchg_binhex, initiatorchg,
469 			    initiatorchg_len) < 0) {
470 			pr_err("Malformed CHAP_C: invalid HEX\n");
471 			goto out;
472 		}
473 		break;
474 	case BASE64:
475 		initiatorchg_len = chap_base64_decode(initiatorchg_binhex,
476 						      initiatorchg,
477 						      strlen(initiatorchg));
478 		if (initiatorchg_len < 0) {
479 			pr_err("Malformed CHAP_C: invalid BASE64\n");
480 			goto out;
481 		}
482 		if (!initiatorchg_len) {
483 			pr_err("Unable to convert incoming challenge\n");
484 			goto out;
485 		}
486 		if (initiatorchg_len > 1024) {
487 			pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
488 			goto out;
489 		}
490 		break;
491 	default:
492 		pr_err("Could not find CHAP_C.\n");
493 		goto out;
494 	}
495 
496 	pr_debug("[server] Got CHAP_C=%s\n", initiatorchg);
497 	/*
498 	 * During mutual authentication, the CHAP_C generated by the
499 	 * initiator must not match the original CHAP_C generated by
500 	 * the target.
501 	 */
502 	if (initiatorchg_len == chap->challenge_len &&
503 				!memcmp(initiatorchg_binhex, chap->challenge,
504 				initiatorchg_len)) {
505 		pr_err("initiator CHAP_C matches target CHAP_C, failing"
506 		       " login attempt\n");
507 		goto out;
508 	}
509 	/*
510 	 * Generate CHAP_N and CHAP_R for mutual authentication.
511 	 */
512 	ret = crypto_shash_init(desc);
513 	if (ret < 0) {
514 		pr_err("crypto_shash_init() failed\n");
515 		goto out;
516 	}
517 
518 	/* To handle both endiannesses */
519 	id_as_uchar = id;
520 	ret = crypto_shash_update(desc, &id_as_uchar, 1);
521 	if (ret < 0) {
522 		pr_err("crypto_shash_update() failed for id\n");
523 		goto out;
524 	}
525 
526 	ret = crypto_shash_update(desc, auth->password_mutual,
527 				  strlen(auth->password_mutual));
528 	if (ret < 0) {
529 		pr_err("crypto_shash_update() failed for"
530 				" password_mutual\n");
531 		goto out;
532 	}
533 	/*
534 	 * Convert received challenge to binary hex.
535 	 */
536 	ret = crypto_shash_finup(desc, initiatorchg_binhex, initiatorchg_len,
537 				 digest);
538 	if (ret < 0) {
539 		pr_err("crypto_shash_finup() failed for ma challenge\n");
540 		goto out;
541 	}
542 
543 	/*
544 	 * Generate CHAP_N and CHAP_R.
545 	 */
546 	*nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
547 	*nr_out_len += 1;
548 	pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
549 	/*
550 	 * Convert response from binary hex to ascii hext.
551 	 */
552 	bin2hex(response, digest, chap->digest_size);
553 	*nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
554 			response);
555 	*nr_out_len += 1;
556 	pr_debug("[server] Sending CHAP_R=0x%s\n", response);
557 	auth_ret = 0;
558 out:
559 	kfree_sensitive(desc);
560 	if (tfm)
561 		crypto_free_shash(tfm);
562 	kfree(initiatorchg);
563 	kfree(initiatorchg_binhex);
564 	kfree(digest);
565 	kfree(response);
566 	kfree(server_digest);
567 	kfree(client_digest);
568 	return auth_ret;
569 }
570 
571 u32 chap_main_loop(
572 	struct iscsit_conn *conn,
573 	struct iscsi_node_auth *auth,
574 	char *in_text,
575 	char *out_text,
576 	int *in_len,
577 	int *out_len)
578 {
579 	struct iscsi_chap *chap = conn->auth_protocol;
580 
581 	if (!chap) {
582 		chap = chap_server_open(conn, auth, in_text, out_text, out_len);
583 		if (!chap)
584 			return 2;
585 		chap->chap_state = CHAP_STAGE_SERVER_AIC;
586 		return 0;
587 	} else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
588 		convert_null_to_semi(in_text, *in_len);
589 		if (chap_server_compute_hash(conn, auth, in_text, out_text,
590 				out_len) < 0) {
591 			chap_close(conn);
592 			return 2;
593 		}
594 		if (auth->authenticate_target)
595 			chap->chap_state = CHAP_STAGE_SERVER_NR;
596 		else
597 			*out_len = 0;
598 		chap_close(conn);
599 		return 1;
600 	}
601 
602 	return 2;
603 }
604