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 <linux/kernel.h>
20 #include <linux/string.h>
21 #include <linux/crypto.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
chap_gen_challenge(struct iscsi_conn * conn,int caller,char * c_str,unsigned int * c_len)29 static void chap_gen_challenge(
30 struct iscsi_conn *conn,
31 int caller,
32 char *c_str,
33 unsigned int *c_len)
34 {
35 unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
36 struct iscsi_chap *chap = conn->auth_protocol;
37
38 memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
39
40 get_random_bytes(chap->challenge, CHAP_CHALLENGE_LENGTH);
41 bin2hex(challenge_asciihex, chap->challenge,
42 CHAP_CHALLENGE_LENGTH);
43 /*
44 * Set CHAP_C, and copy the generated challenge into c_str.
45 */
46 *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
47 *c_len += 1;
48
49 pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
50 challenge_asciihex);
51 }
52
chap_check_algorithm(const char * a_str)53 static int chap_check_algorithm(const char *a_str)
54 {
55 char *tmp, *orig, *token;
56
57 tmp = kstrdup(a_str, GFP_KERNEL);
58 if (!tmp) {
59 pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
60 return CHAP_DIGEST_UNKNOWN;
61 }
62 orig = tmp;
63
64 token = strsep(&tmp, "=");
65 if (!token)
66 goto out;
67
68 if (strcmp(token, "CHAP_A")) {
69 pr_err("Unable to locate CHAP_A key\n");
70 goto out;
71 }
72 while (token) {
73 token = strsep(&tmp, ",");
74 if (!token)
75 goto out;
76
77 if (!strcmp(token, "5")) {
78 pr_debug("Selected MD5 Algorithm\n");
79 kfree(orig);
80 return CHAP_DIGEST_MD5;
81 }
82 }
83 out:
84 kfree(orig);
85 return CHAP_DIGEST_UNKNOWN;
86 }
87
chap_server_open(struct iscsi_conn * conn,struct iscsi_node_auth * auth,const char * a_str,char * aic_str,unsigned int * aic_len)88 static struct iscsi_chap *chap_server_open(
89 struct iscsi_conn *conn,
90 struct iscsi_node_auth *auth,
91 const char *a_str,
92 char *aic_str,
93 unsigned int *aic_len)
94 {
95 int ret;
96 struct iscsi_chap *chap;
97
98 if (!(auth->naf_flags & NAF_USERID_SET) ||
99 !(auth->naf_flags & NAF_PASSWORD_SET)) {
100 pr_err("CHAP user or password not set for"
101 " Initiator ACL\n");
102 return NULL;
103 }
104
105 conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
106 if (!conn->auth_protocol)
107 return NULL;
108
109 chap = conn->auth_protocol;
110 ret = chap_check_algorithm(a_str);
111 switch (ret) {
112 case CHAP_DIGEST_MD5:
113 pr_debug("[server] Got CHAP_A=5\n");
114 /*
115 * Send back CHAP_A set to MD5.
116 */
117 *aic_len = sprintf(aic_str, "CHAP_A=5");
118 *aic_len += 1;
119 chap->digest_type = CHAP_DIGEST_MD5;
120 pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type);
121 break;
122 case CHAP_DIGEST_UNKNOWN:
123 default:
124 pr_err("Unsupported CHAP_A value\n");
125 return NULL;
126 }
127
128 /*
129 * Set Identifier.
130 */
131 chap->id = conn->tpg->tpg_chap_id++;
132 *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
133 *aic_len += 1;
134 pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
135 /*
136 * Generate Challenge.
137 */
138 chap_gen_challenge(conn, 1, aic_str, aic_len);
139
140 return chap;
141 }
142
chap_close(struct iscsi_conn * conn)143 static void chap_close(struct iscsi_conn *conn)
144 {
145 kfree(conn->auth_protocol);
146 conn->auth_protocol = NULL;
147 }
148
chap_server_compute_md5(struct iscsi_conn * conn,struct iscsi_node_auth * auth,char * nr_in_ptr,char * nr_out_ptr,unsigned int * nr_out_len)149 static int chap_server_compute_md5(
150 struct iscsi_conn *conn,
151 struct iscsi_node_auth *auth,
152 char *nr_in_ptr,
153 char *nr_out_ptr,
154 unsigned int *nr_out_len)
155 {
156 unsigned long id;
157 unsigned char id_as_uchar;
158 unsigned char digest[MD5_SIGNATURE_SIZE];
159 unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
160 unsigned char identifier[10], *challenge = NULL;
161 unsigned char *challenge_binhex = NULL;
162 unsigned char client_digest[MD5_SIGNATURE_SIZE];
163 unsigned char server_digest[MD5_SIGNATURE_SIZE];
164 unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
165 size_t compare_len;
166 struct iscsi_chap *chap = conn->auth_protocol;
167 struct crypto_hash *tfm;
168 struct hash_desc desc;
169 struct scatterlist sg;
170 int auth_ret = -1, ret, challenge_len;
171
172 memset(identifier, 0, 10);
173 memset(chap_n, 0, MAX_CHAP_N_SIZE);
174 memset(chap_r, 0, MAX_RESPONSE_LENGTH);
175 memset(digest, 0, MD5_SIGNATURE_SIZE);
176 memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
177 memset(client_digest, 0, MD5_SIGNATURE_SIZE);
178 memset(server_digest, 0, MD5_SIGNATURE_SIZE);
179
180 challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
181 if (!challenge) {
182 pr_err("Unable to allocate challenge buffer\n");
183 goto out;
184 }
185
186 challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
187 if (!challenge_binhex) {
188 pr_err("Unable to allocate challenge_binhex buffer\n");
189 goto out;
190 }
191 /*
192 * Extract CHAP_N.
193 */
194 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
195 &type) < 0) {
196 pr_err("Could not find CHAP_N.\n");
197 goto out;
198 }
199 if (type == HEX) {
200 pr_err("Could not find CHAP_N.\n");
201 goto out;
202 }
203
204 /* Include the terminating NULL in the compare */
205 compare_len = strlen(auth->userid) + 1;
206 if (strncmp(chap_n, auth->userid, compare_len) != 0) {
207 pr_err("CHAP_N values do not match!\n");
208 goto out;
209 }
210 pr_debug("[server] Got CHAP_N=%s\n", chap_n);
211 /*
212 * Extract CHAP_R.
213 */
214 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
215 &type) < 0) {
216 pr_err("Could not find CHAP_R.\n");
217 goto out;
218 }
219 if (type != HEX) {
220 pr_err("Could not find CHAP_R.\n");
221 goto out;
222 }
223 if (strlen(chap_r) != MD5_SIGNATURE_SIZE * 2) {
224 pr_err("Malformed CHAP_R\n");
225 goto out;
226 }
227 if (hex2bin(client_digest, chap_r, MD5_SIGNATURE_SIZE) < 0) {
228 pr_err("Malformed CHAP_R\n");
229 goto out;
230 }
231
232 pr_debug("[server] Got CHAP_R=%s\n", chap_r);
233
234 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
235 if (IS_ERR(tfm)) {
236 pr_err("Unable to allocate struct crypto_hash\n");
237 goto out;
238 }
239 desc.tfm = tfm;
240 desc.flags = 0;
241
242 ret = crypto_hash_init(&desc);
243 if (ret < 0) {
244 pr_err("crypto_hash_init() failed\n");
245 crypto_free_hash(tfm);
246 goto out;
247 }
248
249 sg_init_one(&sg, &chap->id, 1);
250 ret = crypto_hash_update(&desc, &sg, 1);
251 if (ret < 0) {
252 pr_err("crypto_hash_update() failed for id\n");
253 crypto_free_hash(tfm);
254 goto out;
255 }
256
257 sg_init_one(&sg, &auth->password, strlen(auth->password));
258 ret = crypto_hash_update(&desc, &sg, strlen(auth->password));
259 if (ret < 0) {
260 pr_err("crypto_hash_update() failed for password\n");
261 crypto_free_hash(tfm);
262 goto out;
263 }
264
265 sg_init_one(&sg, chap->challenge, CHAP_CHALLENGE_LENGTH);
266 ret = crypto_hash_update(&desc, &sg, CHAP_CHALLENGE_LENGTH);
267 if (ret < 0) {
268 pr_err("crypto_hash_update() failed for challenge\n");
269 crypto_free_hash(tfm);
270 goto out;
271 }
272
273 ret = crypto_hash_final(&desc, server_digest);
274 if (ret < 0) {
275 pr_err("crypto_hash_final() failed for server digest\n");
276 crypto_free_hash(tfm);
277 goto out;
278 }
279 crypto_free_hash(tfm);
280
281 bin2hex(response, server_digest, MD5_SIGNATURE_SIZE);
282 pr_debug("[server] MD5 Server Digest: %s\n", response);
283
284 if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
285 pr_debug("[server] MD5 Digests do not match!\n\n");
286 goto out;
287 } else
288 pr_debug("[server] MD5 Digests match, CHAP connetication"
289 " successful.\n\n");
290 /*
291 * One way authentication has succeeded, return now if mutual
292 * authentication is not enabled.
293 */
294 if (!auth->authenticate_target) {
295 kfree(challenge);
296 kfree(challenge_binhex);
297 return 0;
298 }
299 /*
300 * Get CHAP_I.
301 */
302 if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
303 pr_err("Could not find CHAP_I.\n");
304 goto out;
305 }
306
307 if (type == HEX)
308 ret = kstrtoul(&identifier[2], 0, &id);
309 else
310 ret = kstrtoul(identifier, 0, &id);
311
312 if (ret < 0) {
313 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
314 goto out;
315 }
316 if (id > 255) {
317 pr_err("chap identifier: %lu greater than 255\n", id);
318 goto out;
319 }
320 /*
321 * RFC 1994 says Identifier is no more than octet (8 bits).
322 */
323 pr_debug("[server] Got CHAP_I=%lu\n", id);
324 /*
325 * Get CHAP_C.
326 */
327 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
328 challenge, &type) < 0) {
329 pr_err("Could not find CHAP_C.\n");
330 goto out;
331 }
332
333 if (type != HEX) {
334 pr_err("Could not find CHAP_C.\n");
335 goto out;
336 }
337 challenge_len = DIV_ROUND_UP(strlen(challenge), 2);
338 if (!challenge_len) {
339 pr_err("Unable to convert incoming challenge\n");
340 goto out;
341 }
342 if (challenge_len > 1024) {
343 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
344 goto out;
345 }
346 if (hex2bin(challenge_binhex, challenge, challenge_len) < 0) {
347 pr_err("Malformed CHAP_C\n");
348 goto out;
349 }
350 pr_debug("[server] Got CHAP_C=%s\n", challenge);
351 /*
352 * During mutual authentication, the CHAP_C generated by the
353 * initiator must not match the original CHAP_C generated by
354 * the target.
355 */
356 if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
357 pr_err("initiator CHAP_C matches target CHAP_C, failing"
358 " login attempt\n");
359 goto out;
360 }
361 /*
362 * Generate CHAP_N and CHAP_R for mutual authentication.
363 */
364 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
365 if (IS_ERR(tfm)) {
366 pr_err("Unable to allocate struct crypto_hash\n");
367 goto out;
368 }
369 desc.tfm = tfm;
370 desc.flags = 0;
371
372 ret = crypto_hash_init(&desc);
373 if (ret < 0) {
374 pr_err("crypto_hash_init() failed\n");
375 crypto_free_hash(tfm);
376 goto out;
377 }
378
379 /* To handle both endiannesses */
380 id_as_uchar = id;
381 sg_init_one(&sg, &id_as_uchar, 1);
382 ret = crypto_hash_update(&desc, &sg, 1);
383 if (ret < 0) {
384 pr_err("crypto_hash_update() failed for id\n");
385 crypto_free_hash(tfm);
386 goto out;
387 }
388
389 sg_init_one(&sg, auth->password_mutual,
390 strlen(auth->password_mutual));
391 ret = crypto_hash_update(&desc, &sg, strlen(auth->password_mutual));
392 if (ret < 0) {
393 pr_err("crypto_hash_update() failed for"
394 " password_mutual\n");
395 crypto_free_hash(tfm);
396 goto out;
397 }
398 /*
399 * Convert received challenge to binary hex.
400 */
401 sg_init_one(&sg, challenge_binhex, challenge_len);
402 ret = crypto_hash_update(&desc, &sg, challenge_len);
403 if (ret < 0) {
404 pr_err("crypto_hash_update() failed for ma challenge\n");
405 crypto_free_hash(tfm);
406 goto out;
407 }
408
409 ret = crypto_hash_final(&desc, digest);
410 if (ret < 0) {
411 pr_err("crypto_hash_final() failed for ma digest\n");
412 crypto_free_hash(tfm);
413 goto out;
414 }
415 crypto_free_hash(tfm);
416 /*
417 * Generate CHAP_N and CHAP_R.
418 */
419 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
420 *nr_out_len += 1;
421 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
422 /*
423 * Convert response from binary hex to ascii hext.
424 */
425 bin2hex(response, digest, MD5_SIGNATURE_SIZE);
426 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
427 response);
428 *nr_out_len += 1;
429 pr_debug("[server] Sending CHAP_R=0x%s\n", response);
430 auth_ret = 0;
431 out:
432 kfree(challenge);
433 kfree(challenge_binhex);
434 return auth_ret;
435 }
436
chap_got_response(struct iscsi_conn * conn,struct iscsi_node_auth * auth,char * nr_in_ptr,char * nr_out_ptr,unsigned int * nr_out_len)437 static int chap_got_response(
438 struct iscsi_conn *conn,
439 struct iscsi_node_auth *auth,
440 char *nr_in_ptr,
441 char *nr_out_ptr,
442 unsigned int *nr_out_len)
443 {
444 struct iscsi_chap *chap = conn->auth_protocol;
445
446 switch (chap->digest_type) {
447 case CHAP_DIGEST_MD5:
448 if (chap_server_compute_md5(conn, auth, nr_in_ptr,
449 nr_out_ptr, nr_out_len) < 0)
450 return -1;
451 return 0;
452 default:
453 pr_err("Unknown CHAP digest type %d!\n",
454 chap->digest_type);
455 return -1;
456 }
457 }
458
chap_main_loop(struct iscsi_conn * conn,struct iscsi_node_auth * auth,char * in_text,char * out_text,int * in_len,int * out_len)459 u32 chap_main_loop(
460 struct iscsi_conn *conn,
461 struct iscsi_node_auth *auth,
462 char *in_text,
463 char *out_text,
464 int *in_len,
465 int *out_len)
466 {
467 struct iscsi_chap *chap = conn->auth_protocol;
468
469 if (!chap) {
470 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
471 if (!chap)
472 return 2;
473 chap->chap_state = CHAP_STAGE_SERVER_AIC;
474 return 0;
475 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
476 convert_null_to_semi(in_text, *in_len);
477 if (chap_got_response(conn, auth, in_text, out_text,
478 out_len) < 0) {
479 chap_close(conn);
480 return 2;
481 }
482 if (auth->authenticate_target)
483 chap->chap_state = CHAP_STAGE_SERVER_NR;
484 else
485 *out_len = 0;
486 chap_close(conn);
487 return 1;
488 }
489
490 return 2;
491 }
492