1 /*******************************************************************************
2  * This file houses the main functions for the iSCSI CHAP support
3  *
4  * (c) Copyright 2007-2013 Datera, Inc.
5  *
6  * Author: Nicholas A. Bellinger <nab@linux-iscsi.org>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  ******************************************************************************/
18 
19 #include <crypto/hash.h>
20 #include <linux/kernel.h>
21 #include <linux/string.h>
22 #include <linux/err.h>
23 #include <linux/random.h>
24 #include <linux/scatterlist.h>
25 #include <target/iscsi/iscsi_target_core.h>
26 #include "iscsi_target_nego.h"
27 #include "iscsi_target_auth.h"
28 
29 static int chap_string_to_hex(unsigned char *dst, unsigned char *src, int len)
30 {
31 	int j = DIV_ROUND_UP(len, 2), rc;
32 
33 	rc = hex2bin(dst, src, j);
34 	if (rc < 0)
35 		pr_debug("CHAP string contains non hex digit symbols\n");
36 
37 	dst[j] = '\0';
38 	return j;
39 }
40 
41 static void chap_binaryhex_to_asciihex(char *dst, char *src, int src_len)
42 {
43 	int i;
44 
45 	for (i = 0; i < src_len; i++) {
46 		sprintf(&dst[i*2], "%02x", (int) src[i] & 0xff);
47 	}
48 }
49 
50 static int chap_gen_challenge(
51 	struct iscsi_conn *conn,
52 	int caller,
53 	char *c_str,
54 	unsigned int *c_len)
55 {
56 	int ret;
57 	unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
58 	struct iscsi_chap *chap = conn->auth_protocol;
59 
60 	memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
61 
62 	ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH);
63 	if (unlikely(ret))
64 		return ret;
65 	chap_binaryhex_to_asciihex(challenge_asciihex, chap->challenge,
66 				CHAP_CHALLENGE_LENGTH);
67 	/*
68 	 * Set CHAP_C, and copy the generated challenge into c_str.
69 	 */
70 	*c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
71 	*c_len += 1;
72 
73 	pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
74 			challenge_asciihex);
75 	return 0;
76 }
77 
78 static int chap_check_algorithm(const char *a_str)
79 {
80 	char *tmp, *orig, *token;
81 
82 	tmp = kstrdup(a_str, GFP_KERNEL);
83 	if (!tmp) {
84 		pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
85 		return CHAP_DIGEST_UNKNOWN;
86 	}
87 	orig = tmp;
88 
89 	token = strsep(&tmp, "=");
90 	if (!token)
91 		goto out;
92 
93 	if (strcmp(token, "CHAP_A")) {
94 		pr_err("Unable to locate CHAP_A key\n");
95 		goto out;
96 	}
97 	while (token) {
98 		token = strsep(&tmp, ",");
99 		if (!token)
100 			goto out;
101 
102 		if (!strncmp(token, "5", 1)) {
103 			pr_debug("Selected MD5 Algorithm\n");
104 			kfree(orig);
105 			return CHAP_DIGEST_MD5;
106 		}
107 	}
108 out:
109 	kfree(orig);
110 	return CHAP_DIGEST_UNKNOWN;
111 }
112 
113 static struct iscsi_chap *chap_server_open(
114 	struct iscsi_conn *conn,
115 	struct iscsi_node_auth *auth,
116 	const char *a_str,
117 	char *aic_str,
118 	unsigned int *aic_len)
119 {
120 	int ret;
121 	struct iscsi_chap *chap;
122 
123 	if (!(auth->naf_flags & NAF_USERID_SET) ||
124 	    !(auth->naf_flags & NAF_PASSWORD_SET)) {
125 		pr_err("CHAP user or password not set for"
126 				" Initiator ACL\n");
127 		return NULL;
128 	}
129 
130 	conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
131 	if (!conn->auth_protocol)
132 		return NULL;
133 
134 	chap = conn->auth_protocol;
135 	ret = chap_check_algorithm(a_str);
136 	switch (ret) {
137 	case CHAP_DIGEST_MD5:
138 		pr_debug("[server] Got CHAP_A=5\n");
139 		/*
140 		 * Send back CHAP_A set to MD5.
141 		*/
142 		*aic_len = sprintf(aic_str, "CHAP_A=5");
143 		*aic_len += 1;
144 		chap->digest_type = CHAP_DIGEST_MD5;
145 		pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type);
146 		break;
147 	case CHAP_DIGEST_UNKNOWN:
148 	default:
149 		pr_err("Unsupported CHAP_A value\n");
150 		kfree(conn->auth_protocol);
151 		return NULL;
152 	}
153 
154 	/*
155 	 * Set Identifier.
156 	 */
157 	chap->id = conn->tpg->tpg_chap_id++;
158 	*aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
159 	*aic_len += 1;
160 	pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
161 	/*
162 	 * Generate Challenge.
163 	 */
164 	if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) {
165 		kfree(conn->auth_protocol);
166 		return NULL;
167 	}
168 
169 	return chap;
170 }
171 
172 static void chap_close(struct iscsi_conn *conn)
173 {
174 	kfree(conn->auth_protocol);
175 	conn->auth_protocol = NULL;
176 }
177 
178 static int chap_server_compute_md5(
179 	struct iscsi_conn *conn,
180 	struct iscsi_node_auth *auth,
181 	char *nr_in_ptr,
182 	char *nr_out_ptr,
183 	unsigned int *nr_out_len)
184 {
185 	unsigned long id;
186 	unsigned char id_as_uchar;
187 	unsigned char digest[MD5_SIGNATURE_SIZE];
188 	unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
189 	unsigned char identifier[10], *challenge = NULL;
190 	unsigned char *challenge_binhex = NULL;
191 	unsigned char client_digest[MD5_SIGNATURE_SIZE];
192 	unsigned char server_digest[MD5_SIGNATURE_SIZE];
193 	unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
194 	size_t compare_len;
195 	struct iscsi_chap *chap = conn->auth_protocol;
196 	struct crypto_shash *tfm = NULL;
197 	struct shash_desc *desc = NULL;
198 	int auth_ret = -1, ret, challenge_len;
199 
200 	memset(identifier, 0, 10);
201 	memset(chap_n, 0, MAX_CHAP_N_SIZE);
202 	memset(chap_r, 0, MAX_RESPONSE_LENGTH);
203 	memset(digest, 0, MD5_SIGNATURE_SIZE);
204 	memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
205 	memset(client_digest, 0, MD5_SIGNATURE_SIZE);
206 	memset(server_digest, 0, MD5_SIGNATURE_SIZE);
207 
208 	challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
209 	if (!challenge) {
210 		pr_err("Unable to allocate challenge buffer\n");
211 		goto out;
212 	}
213 
214 	challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
215 	if (!challenge_binhex) {
216 		pr_err("Unable to allocate challenge_binhex buffer\n");
217 		goto out;
218 	}
219 	/*
220 	 * Extract CHAP_N.
221 	 */
222 	if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
223 				&type) < 0) {
224 		pr_err("Could not find CHAP_N.\n");
225 		goto out;
226 	}
227 	if (type == HEX) {
228 		pr_err("Could not find CHAP_N.\n");
229 		goto out;
230 	}
231 
232 	/* Include the terminating NULL in the compare */
233 	compare_len = strlen(auth->userid) + 1;
234 	if (strncmp(chap_n, auth->userid, compare_len) != 0) {
235 		pr_err("CHAP_N values do not match!\n");
236 		goto out;
237 	}
238 	pr_debug("[server] Got CHAP_N=%s\n", chap_n);
239 	/*
240 	 * Extract CHAP_R.
241 	 */
242 	if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
243 				&type) < 0) {
244 		pr_err("Could not find CHAP_R.\n");
245 		goto out;
246 	}
247 	if (type != HEX) {
248 		pr_err("Could not find CHAP_R.\n");
249 		goto out;
250 	}
251 
252 	pr_debug("[server] Got CHAP_R=%s\n", chap_r);
253 	chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
254 
255 	tfm = crypto_alloc_shash("md5", 0, 0);
256 	if (IS_ERR(tfm)) {
257 		tfm = NULL;
258 		pr_err("Unable to allocate struct crypto_shash\n");
259 		goto out;
260 	}
261 
262 	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
263 	if (!desc) {
264 		pr_err("Unable to allocate struct shash_desc\n");
265 		goto out;
266 	}
267 
268 	desc->tfm = tfm;
269 	desc->flags = 0;
270 
271 	ret = crypto_shash_init(desc);
272 	if (ret < 0) {
273 		pr_err("crypto_shash_init() failed\n");
274 		goto out;
275 	}
276 
277 	ret = crypto_shash_update(desc, &chap->id, 1);
278 	if (ret < 0) {
279 		pr_err("crypto_shash_update() failed for id\n");
280 		goto out;
281 	}
282 
283 	ret = crypto_shash_update(desc, (char *)&auth->password,
284 				  strlen(auth->password));
285 	if (ret < 0) {
286 		pr_err("crypto_shash_update() failed for password\n");
287 		goto out;
288 	}
289 
290 	ret = crypto_shash_finup(desc, chap->challenge,
291 				 CHAP_CHALLENGE_LENGTH, server_digest);
292 	if (ret < 0) {
293 		pr_err("crypto_shash_finup() failed for challenge\n");
294 		goto out;
295 	}
296 
297 	chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
298 	pr_debug("[server] MD5 Server Digest: %s\n", response);
299 
300 	if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
301 		pr_debug("[server] MD5 Digests do not match!\n\n");
302 		goto out;
303 	} else
304 		pr_debug("[server] MD5 Digests match, CHAP connection"
305 				" successful.\n\n");
306 	/*
307 	 * One way authentication has succeeded, return now if mutual
308 	 * authentication is not enabled.
309 	 */
310 	if (!auth->authenticate_target) {
311 		auth_ret = 0;
312 		goto out;
313 	}
314 	/*
315 	 * Get CHAP_I.
316 	 */
317 	if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
318 		pr_err("Could not find CHAP_I.\n");
319 		goto out;
320 	}
321 
322 	if (type == HEX)
323 		ret = kstrtoul(&identifier[2], 0, &id);
324 	else
325 		ret = kstrtoul(identifier, 0, &id);
326 
327 	if (ret < 0) {
328 		pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
329 		goto out;
330 	}
331 	if (id > 255) {
332 		pr_err("chap identifier: %lu greater than 255\n", id);
333 		goto out;
334 	}
335 	/*
336 	 * RFC 1994 says Identifier is no more than octet (8 bits).
337 	 */
338 	pr_debug("[server] Got CHAP_I=%lu\n", id);
339 	/*
340 	 * Get CHAP_C.
341 	 */
342 	if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
343 			challenge, &type) < 0) {
344 		pr_err("Could not find CHAP_C.\n");
345 		goto out;
346 	}
347 
348 	if (type != HEX) {
349 		pr_err("Could not find CHAP_C.\n");
350 		goto out;
351 	}
352 	pr_debug("[server] Got CHAP_C=%s\n", challenge);
353 	challenge_len = chap_string_to_hex(challenge_binhex, challenge,
354 				strlen(challenge));
355 	if (!challenge_len) {
356 		pr_err("Unable to convert incoming challenge\n");
357 		goto out;
358 	}
359 	if (challenge_len > 1024) {
360 		pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
361 		goto out;
362 	}
363 	/*
364 	 * During mutual authentication, the CHAP_C generated by the
365 	 * initiator must not match the original CHAP_C generated by
366 	 * the target.
367 	 */
368 	if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
369 		pr_err("initiator CHAP_C matches target CHAP_C, failing"
370 		       " login attempt\n");
371 		goto out;
372 	}
373 	/*
374 	 * Generate CHAP_N and CHAP_R for mutual authentication.
375 	 */
376 	ret = crypto_shash_init(desc);
377 	if (ret < 0) {
378 		pr_err("crypto_shash_init() failed\n");
379 		goto out;
380 	}
381 
382 	/* To handle both endiannesses */
383 	id_as_uchar = id;
384 	ret = crypto_shash_update(desc, &id_as_uchar, 1);
385 	if (ret < 0) {
386 		pr_err("crypto_shash_update() failed for id\n");
387 		goto out;
388 	}
389 
390 	ret = crypto_shash_update(desc, auth->password_mutual,
391 				  strlen(auth->password_mutual));
392 	if (ret < 0) {
393 		pr_err("crypto_shash_update() failed for"
394 				" password_mutual\n");
395 		goto out;
396 	}
397 	/*
398 	 * Convert received challenge to binary hex.
399 	 */
400 	ret = crypto_shash_finup(desc, challenge_binhex, challenge_len,
401 				 digest);
402 	if (ret < 0) {
403 		pr_err("crypto_shash_finup() failed for ma challenge\n");
404 		goto out;
405 	}
406 
407 	/*
408 	 * Generate CHAP_N and CHAP_R.
409 	 */
410 	*nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
411 	*nr_out_len += 1;
412 	pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
413 	/*
414 	 * Convert response from binary hex to ascii hext.
415 	 */
416 	chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE);
417 	*nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
418 			response);
419 	*nr_out_len += 1;
420 	pr_debug("[server] Sending CHAP_R=0x%s\n", response);
421 	auth_ret = 0;
422 out:
423 	kzfree(desc);
424 	crypto_free_shash(tfm);
425 	kfree(challenge);
426 	kfree(challenge_binhex);
427 	return auth_ret;
428 }
429 
430 static int chap_got_response(
431 	struct iscsi_conn *conn,
432 	struct iscsi_node_auth *auth,
433 	char *nr_in_ptr,
434 	char *nr_out_ptr,
435 	unsigned int *nr_out_len)
436 {
437 	struct iscsi_chap *chap = conn->auth_protocol;
438 
439 	switch (chap->digest_type) {
440 	case CHAP_DIGEST_MD5:
441 		if (chap_server_compute_md5(conn, auth, nr_in_ptr,
442 				nr_out_ptr, nr_out_len) < 0)
443 			return -1;
444 		return 0;
445 	default:
446 		pr_err("Unknown CHAP digest type %d!\n",
447 				chap->digest_type);
448 		return -1;
449 	}
450 }
451 
452 u32 chap_main_loop(
453 	struct iscsi_conn *conn,
454 	struct iscsi_node_auth *auth,
455 	char *in_text,
456 	char *out_text,
457 	int *in_len,
458 	int *out_len)
459 {
460 	struct iscsi_chap *chap = conn->auth_protocol;
461 
462 	if (!chap) {
463 		chap = chap_server_open(conn, auth, in_text, out_text, out_len);
464 		if (!chap)
465 			return 2;
466 		chap->chap_state = CHAP_STAGE_SERVER_AIC;
467 		return 0;
468 	} else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
469 		convert_null_to_semi(in_text, *in_len);
470 		if (chap_got_response(conn, auth, in_text, out_text,
471 				out_len) < 0) {
472 			chap_close(conn);
473 			return 2;
474 		}
475 		if (auth->authenticate_target)
476 			chap->chap_state = CHAP_STAGE_SERVER_NR;
477 		else
478 			*out_len = 0;
479 		chap_close(conn);
480 		return 1;
481 	}
482 
483 	return 2;
484 }
485