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