Loading...
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 "iscsi_target_core.h"
26#include "iscsi_target_nego.h"
27#include "iscsi_target_auth.h"
28
29static 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
41static 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
50static 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
75static struct iscsi_chap *chap_server_open(
76 struct iscsi_conn *conn,
77 struct iscsi_node_auth *auth,
78 const char *a_str,
79 char *aic_str,
80 unsigned int *aic_len)
81{
82 struct iscsi_chap *chap;
83
84 if (!(auth->naf_flags & NAF_USERID_SET) ||
85 !(auth->naf_flags & NAF_PASSWORD_SET)) {
86 pr_err("CHAP user or password not set for"
87 " Initiator ACL\n");
88 return NULL;
89 }
90
91 conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
92 if (!conn->auth_protocol)
93 return NULL;
94
95 chap = conn->auth_protocol;
96 /*
97 * We only support MD5 MDA presently.
98 */
99 if (strncmp(a_str, "CHAP_A=5", 8)) {
100 pr_err("CHAP_A is not MD5.\n");
101 return NULL;
102 }
103 pr_debug("[server] Got CHAP_A=5\n");
104 /*
105 * Send back CHAP_A set to MD5.
106 */
107 *aic_len = sprintf(aic_str, "CHAP_A=5");
108 *aic_len += 1;
109 chap->digest_type = CHAP_DIGEST_MD5;
110 pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type);
111 /*
112 * Set Identifier.
113 */
114 chap->id = conn->tpg->tpg_chap_id++;
115 *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
116 *aic_len += 1;
117 pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
118 /*
119 * Generate Challenge.
120 */
121 chap_gen_challenge(conn, 1, aic_str, aic_len);
122
123 return chap;
124}
125
126static void chap_close(struct iscsi_conn *conn)
127{
128 kfree(conn->auth_protocol);
129 conn->auth_protocol = NULL;
130}
131
132static int chap_server_compute_md5(
133 struct iscsi_conn *conn,
134 struct iscsi_node_auth *auth,
135 char *nr_in_ptr,
136 char *nr_out_ptr,
137 unsigned int *nr_out_len)
138{
139 char *endptr;
140 unsigned long id;
141 unsigned char id_as_uchar;
142 unsigned char digest[MD5_SIGNATURE_SIZE];
143 unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
144 unsigned char identifier[10], *challenge = NULL;
145 unsigned char *challenge_binhex = NULL;
146 unsigned char client_digest[MD5_SIGNATURE_SIZE];
147 unsigned char server_digest[MD5_SIGNATURE_SIZE];
148 unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
149 size_t compare_len;
150 struct iscsi_chap *chap = conn->auth_protocol;
151 struct crypto_hash *tfm;
152 struct hash_desc desc;
153 struct scatterlist sg;
154 int auth_ret = -1, ret, challenge_len;
155
156 memset(identifier, 0, 10);
157 memset(chap_n, 0, MAX_CHAP_N_SIZE);
158 memset(chap_r, 0, MAX_RESPONSE_LENGTH);
159 memset(digest, 0, MD5_SIGNATURE_SIZE);
160 memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
161 memset(client_digest, 0, MD5_SIGNATURE_SIZE);
162 memset(server_digest, 0, MD5_SIGNATURE_SIZE);
163
164 challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
165 if (!challenge) {
166 pr_err("Unable to allocate challenge buffer\n");
167 goto out;
168 }
169
170 challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
171 if (!challenge_binhex) {
172 pr_err("Unable to allocate challenge_binhex buffer\n");
173 goto out;
174 }
175 /*
176 * Extract CHAP_N.
177 */
178 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
179 &type) < 0) {
180 pr_err("Could not find CHAP_N.\n");
181 goto out;
182 }
183 if (type == HEX) {
184 pr_err("Could not find CHAP_N.\n");
185 goto out;
186 }
187
188 /* Include the terminating NULL in the compare */
189 compare_len = strlen(auth->userid) + 1;
190 if (strncmp(chap_n, auth->userid, compare_len) != 0) {
191 pr_err("CHAP_N values do not match!\n");
192 goto out;
193 }
194 pr_debug("[server] Got CHAP_N=%s\n", chap_n);
195 /*
196 * Extract CHAP_R.
197 */
198 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
199 &type) < 0) {
200 pr_err("Could not find CHAP_R.\n");
201 goto out;
202 }
203 if (type != HEX) {
204 pr_err("Could not find CHAP_R.\n");
205 goto out;
206 }
207
208 pr_debug("[server] Got CHAP_R=%s\n", chap_r);
209 chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
210
211 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
212 if (IS_ERR(tfm)) {
213 pr_err("Unable to allocate struct crypto_hash\n");
214 goto out;
215 }
216 desc.tfm = tfm;
217 desc.flags = 0;
218
219 ret = crypto_hash_init(&desc);
220 if (ret < 0) {
221 pr_err("crypto_hash_init() failed\n");
222 crypto_free_hash(tfm);
223 goto out;
224 }
225
226 sg_init_one(&sg, &chap->id, 1);
227 ret = crypto_hash_update(&desc, &sg, 1);
228 if (ret < 0) {
229 pr_err("crypto_hash_update() failed for id\n");
230 crypto_free_hash(tfm);
231 goto out;
232 }
233
234 sg_init_one(&sg, &auth->password, strlen(auth->password));
235 ret = crypto_hash_update(&desc, &sg, strlen(auth->password));
236 if (ret < 0) {
237 pr_err("crypto_hash_update() failed for password\n");
238 crypto_free_hash(tfm);
239 goto out;
240 }
241
242 sg_init_one(&sg, chap->challenge, CHAP_CHALLENGE_LENGTH);
243 ret = crypto_hash_update(&desc, &sg, CHAP_CHALLENGE_LENGTH);
244 if (ret < 0) {
245 pr_err("crypto_hash_update() failed for challenge\n");
246 crypto_free_hash(tfm);
247 goto out;
248 }
249
250 ret = crypto_hash_final(&desc, server_digest);
251 if (ret < 0) {
252 pr_err("crypto_hash_final() failed for server digest\n");
253 crypto_free_hash(tfm);
254 goto out;
255 }
256 crypto_free_hash(tfm);
257
258 chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
259 pr_debug("[server] MD5 Server Digest: %s\n", response);
260
261 if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
262 pr_debug("[server] MD5 Digests do not match!\n\n");
263 goto out;
264 } else
265 pr_debug("[server] MD5 Digests match, CHAP connetication"
266 " successful.\n\n");
267 /*
268 * One way authentication has succeeded, return now if mutual
269 * authentication is not enabled.
270 */
271 if (!auth->authenticate_target) {
272 kfree(challenge);
273 kfree(challenge_binhex);
274 return 0;
275 }
276 /*
277 * Get CHAP_I.
278 */
279 if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
280 pr_err("Could not find CHAP_I.\n");
281 goto out;
282 }
283
284 if (type == HEX)
285 id = simple_strtoul(&identifier[2], &endptr, 0);
286 else
287 id = simple_strtoul(identifier, &endptr, 0);
288 if (id > 255) {
289 pr_err("chap identifier: %lu greater than 255\n", id);
290 goto out;
291 }
292 /*
293 * RFC 1994 says Identifier is no more than octet (8 bits).
294 */
295 pr_debug("[server] Got CHAP_I=%lu\n", id);
296 /*
297 * Get CHAP_C.
298 */
299 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
300 challenge, &type) < 0) {
301 pr_err("Could not find CHAP_C.\n");
302 goto out;
303 }
304
305 if (type != HEX) {
306 pr_err("Could not find CHAP_C.\n");
307 goto out;
308 }
309 pr_debug("[server] Got CHAP_C=%s\n", challenge);
310 challenge_len = chap_string_to_hex(challenge_binhex, challenge,
311 strlen(challenge));
312 if (!challenge_len) {
313 pr_err("Unable to convert incoming challenge\n");
314 goto out;
315 }
316 /*
317 * Generate CHAP_N and CHAP_R for mutual authentication.
318 */
319 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
320 if (IS_ERR(tfm)) {
321 pr_err("Unable to allocate struct crypto_hash\n");
322 goto out;
323 }
324 desc.tfm = tfm;
325 desc.flags = 0;
326
327 ret = crypto_hash_init(&desc);
328 if (ret < 0) {
329 pr_err("crypto_hash_init() failed\n");
330 crypto_free_hash(tfm);
331 goto out;
332 }
333
334 /* To handle both endiannesses */
335 id_as_uchar = id;
336 sg_init_one(&sg, &id_as_uchar, 1);
337 ret = crypto_hash_update(&desc, &sg, 1);
338 if (ret < 0) {
339 pr_err("crypto_hash_update() failed for id\n");
340 crypto_free_hash(tfm);
341 goto out;
342 }
343
344 sg_init_one(&sg, auth->password_mutual,
345 strlen(auth->password_mutual));
346 ret = crypto_hash_update(&desc, &sg, strlen(auth->password_mutual));
347 if (ret < 0) {
348 pr_err("crypto_hash_update() failed for"
349 " password_mutual\n");
350 crypto_free_hash(tfm);
351 goto out;
352 }
353 /*
354 * Convert received challenge to binary hex.
355 */
356 sg_init_one(&sg, challenge_binhex, challenge_len);
357 ret = crypto_hash_update(&desc, &sg, challenge_len);
358 if (ret < 0) {
359 pr_err("crypto_hash_update() failed for ma challenge\n");
360 crypto_free_hash(tfm);
361 goto out;
362 }
363
364 ret = crypto_hash_final(&desc, digest);
365 if (ret < 0) {
366 pr_err("crypto_hash_final() failed for ma digest\n");
367 crypto_free_hash(tfm);
368 goto out;
369 }
370 crypto_free_hash(tfm);
371 /*
372 * Generate CHAP_N and CHAP_R.
373 */
374 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
375 *nr_out_len += 1;
376 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
377 /*
378 * Convert response from binary hex to ascii hext.
379 */
380 chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE);
381 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
382 response);
383 *nr_out_len += 1;
384 pr_debug("[server] Sending CHAP_R=0x%s\n", response);
385 auth_ret = 0;
386out:
387 kfree(challenge);
388 kfree(challenge_binhex);
389 return auth_ret;
390}
391
392static int chap_got_response(
393 struct iscsi_conn *conn,
394 struct iscsi_node_auth *auth,
395 char *nr_in_ptr,
396 char *nr_out_ptr,
397 unsigned int *nr_out_len)
398{
399 struct iscsi_chap *chap = conn->auth_protocol;
400
401 switch (chap->digest_type) {
402 case CHAP_DIGEST_MD5:
403 if (chap_server_compute_md5(conn, auth, nr_in_ptr,
404 nr_out_ptr, nr_out_len) < 0)
405 return -1;
406 return 0;
407 default:
408 pr_err("Unknown CHAP digest type %d!\n",
409 chap->digest_type);
410 return -1;
411 }
412}
413
414u32 chap_main_loop(
415 struct iscsi_conn *conn,
416 struct iscsi_node_auth *auth,
417 char *in_text,
418 char *out_text,
419 int *in_len,
420 int *out_len)
421{
422 struct iscsi_chap *chap = conn->auth_protocol;
423
424 if (!chap) {
425 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
426 if (!chap)
427 return 2;
428 chap->chap_state = CHAP_STAGE_SERVER_AIC;
429 return 0;
430 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
431 convert_null_to_semi(in_text, *in_len);
432 if (chap_got_response(conn, auth, in_text, out_text,
433 out_len) < 0) {
434 chap_close(conn);
435 return 2;
436 }
437 if (auth->authenticate_target)
438 chap->chap_state = CHAP_STAGE_SERVER_NR;
439 else
440 *out_len = 0;
441 chap_close(conn);
442 return 1;
443 }
444
445 return 2;
446}