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 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_hash *tfm; 189 struct hash_desc desc; 190 struct scatterlist sg; 191 int auth_ret = -1, ret, challenge_len; 192 193 memset(identifier, 0, 10); 194 memset(chap_n, 0, MAX_CHAP_N_SIZE); 195 memset(chap_r, 0, MAX_RESPONSE_LENGTH); 196 memset(digest, 0, MD5_SIGNATURE_SIZE); 197 memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2); 198 memset(client_digest, 0, MD5_SIGNATURE_SIZE); 199 memset(server_digest, 0, MD5_SIGNATURE_SIZE); 200 201 challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 202 if (!challenge) { 203 pr_err("Unable to allocate challenge buffer\n"); 204 goto out; 205 } 206 207 challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 208 if (!challenge_binhex) { 209 pr_err("Unable to allocate challenge_binhex buffer\n"); 210 goto out; 211 } 212 /* 213 * Extract CHAP_N. 214 */ 215 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n, 216 &type) < 0) { 217 pr_err("Could not find CHAP_N.\n"); 218 goto out; 219 } 220 if (type == HEX) { 221 pr_err("Could not find CHAP_N.\n"); 222 goto out; 223 } 224 225 /* Include the terminating NULL in the compare */ 226 compare_len = strlen(auth->userid) + 1; 227 if (strncmp(chap_n, auth->userid, compare_len) != 0) { 228 pr_err("CHAP_N values do not match!\n"); 229 goto out; 230 } 231 pr_debug("[server] Got CHAP_N=%s\n", chap_n); 232 /* 233 * Extract CHAP_R. 234 */ 235 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r, 236 &type) < 0) { 237 pr_err("Could not find CHAP_R.\n"); 238 goto out; 239 } 240 if (type != HEX) { 241 pr_err("Could not find CHAP_R.\n"); 242 goto out; 243 } 244 245 pr_debug("[server] Got CHAP_R=%s\n", chap_r); 246 chap_string_to_hex(client_digest, chap_r, strlen(chap_r)); 247 248 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC); 249 if (IS_ERR(tfm)) { 250 pr_err("Unable to allocate struct crypto_hash\n"); 251 goto out; 252 } 253 desc.tfm = tfm; 254 desc.flags = 0; 255 256 ret = crypto_hash_init(&desc); 257 if (ret < 0) { 258 pr_err("crypto_hash_init() failed\n"); 259 crypto_free_hash(tfm); 260 goto out; 261 } 262 263 sg_init_one(&sg, &chap->id, 1); 264 ret = crypto_hash_update(&desc, &sg, 1); 265 if (ret < 0) { 266 pr_err("crypto_hash_update() failed for id\n"); 267 crypto_free_hash(tfm); 268 goto out; 269 } 270 271 sg_init_one(&sg, &auth->password, strlen(auth->password)); 272 ret = crypto_hash_update(&desc, &sg, strlen(auth->password)); 273 if (ret < 0) { 274 pr_err("crypto_hash_update() failed for password\n"); 275 crypto_free_hash(tfm); 276 goto out; 277 } 278 279 sg_init_one(&sg, chap->challenge, CHAP_CHALLENGE_LENGTH); 280 ret = crypto_hash_update(&desc, &sg, CHAP_CHALLENGE_LENGTH); 281 if (ret < 0) { 282 pr_err("crypto_hash_update() failed for challenge\n"); 283 crypto_free_hash(tfm); 284 goto out; 285 } 286 287 ret = crypto_hash_final(&desc, server_digest); 288 if (ret < 0) { 289 pr_err("crypto_hash_final() failed for server digest\n"); 290 crypto_free_hash(tfm); 291 goto out; 292 } 293 crypto_free_hash(tfm); 294 295 chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE); 296 pr_debug("[server] MD5 Server Digest: %s\n", response); 297 298 if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) { 299 pr_debug("[server] MD5 Digests do not match!\n\n"); 300 goto out; 301 } else 302 pr_debug("[server] MD5 Digests match, CHAP connetication" 303 " successful.\n\n"); 304 /* 305 * One way authentication has succeeded, return now if mutual 306 * authentication is not enabled. 307 */ 308 if (!auth->authenticate_target) { 309 kfree(challenge); 310 kfree(challenge_binhex); 311 return 0; 312 } 313 /* 314 * Get CHAP_I. 315 */ 316 if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) { 317 pr_err("Could not find CHAP_I.\n"); 318 goto out; 319 } 320 321 if (type == HEX) 322 ret = kstrtoul(&identifier[2], 0, &id); 323 else 324 ret = kstrtoul(identifier, 0, &id); 325 326 if (ret < 0) { 327 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret); 328 goto out; 329 } 330 if (id > 255) { 331 pr_err("chap identifier: %lu greater than 255\n", id); 332 goto out; 333 } 334 /* 335 * RFC 1994 says Identifier is no more than octet (8 bits). 336 */ 337 pr_debug("[server] Got CHAP_I=%lu\n", id); 338 /* 339 * Get CHAP_C. 340 */ 341 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN, 342 challenge, &type) < 0) { 343 pr_err("Could not find CHAP_C.\n"); 344 goto out; 345 } 346 347 if (type != HEX) { 348 pr_err("Could not find CHAP_C.\n"); 349 goto out; 350 } 351 pr_debug("[server] Got CHAP_C=%s\n", challenge); 352 challenge_len = chap_string_to_hex(challenge_binhex, challenge, 353 strlen(challenge)); 354 if (!challenge_len) { 355 pr_err("Unable to convert incoming challenge\n"); 356 goto out; 357 } 358 if (challenge_len > 1024) { 359 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n"); 360 goto out; 361 } 362 /* 363 * During mutual authentication, the CHAP_C generated by the 364 * initiator must not match the original CHAP_C generated by 365 * the target. 366 */ 367 if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) { 368 pr_err("initiator CHAP_C matches target CHAP_C, failing" 369 " login attempt\n"); 370 goto out; 371 } 372 /* 373 * Generate CHAP_N and CHAP_R for mutual authentication. 374 */ 375 tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC); 376 if (IS_ERR(tfm)) { 377 pr_err("Unable to allocate struct crypto_hash\n"); 378 goto out; 379 } 380 desc.tfm = tfm; 381 desc.flags = 0; 382 383 ret = crypto_hash_init(&desc); 384 if (ret < 0) { 385 pr_err("crypto_hash_init() failed\n"); 386 crypto_free_hash(tfm); 387 goto out; 388 } 389 390 /* To handle both endiannesses */ 391 id_as_uchar = id; 392 sg_init_one(&sg, &id_as_uchar, 1); 393 ret = crypto_hash_update(&desc, &sg, 1); 394 if (ret < 0) { 395 pr_err("crypto_hash_update() failed for id\n"); 396 crypto_free_hash(tfm); 397 goto out; 398 } 399 400 sg_init_one(&sg, auth->password_mutual, 401 strlen(auth->password_mutual)); 402 ret = crypto_hash_update(&desc, &sg, strlen(auth->password_mutual)); 403 if (ret < 0) { 404 pr_err("crypto_hash_update() failed for" 405 " password_mutual\n"); 406 crypto_free_hash(tfm); 407 goto out; 408 } 409 /* 410 * Convert received challenge to binary hex. 411 */ 412 sg_init_one(&sg, challenge_binhex, challenge_len); 413 ret = crypto_hash_update(&desc, &sg, challenge_len); 414 if (ret < 0) { 415 pr_err("crypto_hash_update() failed for ma challenge\n"); 416 crypto_free_hash(tfm); 417 goto out; 418 } 419 420 ret = crypto_hash_final(&desc, digest); 421 if (ret < 0) { 422 pr_err("crypto_hash_final() failed for ma digest\n"); 423 crypto_free_hash(tfm); 424 goto out; 425 } 426 crypto_free_hash(tfm); 427 /* 428 * Generate CHAP_N and CHAP_R. 429 */ 430 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual); 431 *nr_out_len += 1; 432 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual); 433 /* 434 * Convert response from binary hex to ascii hext. 435 */ 436 chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE); 437 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s", 438 response); 439 *nr_out_len += 1; 440 pr_debug("[server] Sending CHAP_R=0x%s\n", response); 441 auth_ret = 0; 442 out: 443 kfree(challenge); 444 kfree(challenge_binhex); 445 return auth_ret; 446 } 447 448 static int chap_got_response( 449 struct iscsi_conn *conn, 450 struct iscsi_node_auth *auth, 451 char *nr_in_ptr, 452 char *nr_out_ptr, 453 unsigned int *nr_out_len) 454 { 455 struct iscsi_chap *chap = conn->auth_protocol; 456 457 switch (chap->digest_type) { 458 case CHAP_DIGEST_MD5: 459 if (chap_server_compute_md5(conn, auth, nr_in_ptr, 460 nr_out_ptr, nr_out_len) < 0) 461 return -1; 462 return 0; 463 default: 464 pr_err("Unknown CHAP digest type %d!\n", 465 chap->digest_type); 466 return -1; 467 } 468 } 469 470 u32 chap_main_loop( 471 struct iscsi_conn *conn, 472 struct iscsi_node_auth *auth, 473 char *in_text, 474 char *out_text, 475 int *in_len, 476 int *out_len) 477 { 478 struct iscsi_chap *chap = conn->auth_protocol; 479 480 if (!chap) { 481 chap = chap_server_open(conn, auth, in_text, out_text, out_len); 482 if (!chap) 483 return 2; 484 chap->chap_state = CHAP_STAGE_SERVER_AIC; 485 return 0; 486 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) { 487 convert_null_to_semi(in_text, *in_len); 488 if (chap_got_response(conn, auth, in_text, out_text, 489 out_len) < 0) { 490 chap_close(conn); 491 return 2; 492 } 493 if (auth->authenticate_target) 494 chap->chap_state = CHAP_STAGE_SERVER_NR; 495 else 496 *out_len = 0; 497 chap_close(conn); 498 return 1; 499 } 500 501 return 2; 502 } 503