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