1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /******************************************************************************* 3 * This file houses the main functions for the iSCSI CHAP support 4 * 5 * (c) Copyright 2007-2013 Datera, Inc. 6 * 7 * Author: Nicholas A. Bellinger <nab@linux-iscsi.org> 8 * 9 ******************************************************************************/ 10 11 #include <crypto/hash.h> 12 #include <crypto/utils.h> 13 #include <linux/kernel.h> 14 #include <linux/string.h> 15 #include <linux/err.h> 16 #include <linux/hex.h> 17 #include <linux/random.h> 18 #include <linux/scatterlist.h> 19 #include <target/iscsi/iscsi_target_core.h> 20 #include "iscsi_target_nego.h" 21 #include "iscsi_target_auth.h" 22 23 static char *chap_get_digest_name(const int digest_type) 24 { 25 switch (digest_type) { 26 case CHAP_DIGEST_MD5: 27 return "md5"; 28 case CHAP_DIGEST_SHA1: 29 return "sha1"; 30 case CHAP_DIGEST_SHA256: 31 return "sha256"; 32 case CHAP_DIGEST_SHA3_256: 33 return "sha3-256"; 34 default: 35 return NULL; 36 } 37 } 38 39 static int chap_gen_challenge( 40 struct iscsit_conn *conn, 41 int caller, 42 char *c_str, 43 unsigned int *c_len) 44 { 45 int ret; 46 unsigned char *challenge_asciihex; 47 struct iscsi_chap *chap = conn->auth_protocol; 48 49 challenge_asciihex = kzalloc(chap->challenge_len * 2 + 1, GFP_KERNEL); 50 if (!challenge_asciihex) 51 return -ENOMEM; 52 53 memset(chap->challenge, 0, MAX_CHAP_CHALLENGE_LEN); 54 55 ret = get_random_bytes_wait(chap->challenge, chap->challenge_len); 56 if (unlikely(ret)) 57 goto out; 58 59 bin2hex(challenge_asciihex, chap->challenge, 60 chap->challenge_len); 61 /* 62 * Set CHAP_C, and copy the generated challenge into c_str. 63 */ 64 *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex); 65 *c_len += 1; 66 67 pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client", 68 challenge_asciihex); 69 70 out: 71 kfree(challenge_asciihex); 72 return ret; 73 } 74 75 static int chap_test_algorithm(const char *name) 76 { 77 struct crypto_shash *tfm; 78 79 tfm = crypto_alloc_shash(name, 0, 0); 80 if (IS_ERR(tfm)) 81 return -1; 82 83 crypto_free_shash(tfm); 84 return 0; 85 } 86 87 static int chap_check_algorithm(const char *a_str) 88 { 89 char *tmp, *orig, *token, *digest_name; 90 long digest_type; 91 int r = CHAP_DIGEST_UNKNOWN; 92 93 tmp = kstrdup(a_str, GFP_KERNEL); 94 if (!tmp) { 95 pr_err("Memory allocation failed for CHAP_A temporary buffer\n"); 96 return CHAP_DIGEST_UNKNOWN; 97 } 98 orig = tmp; 99 100 token = strsep(&tmp, "="); 101 if (!token) 102 goto out; 103 104 if (strcmp(token, "CHAP_A")) { 105 pr_err("Unable to locate CHAP_A key\n"); 106 goto out; 107 } 108 while (token) { 109 token = strsep(&tmp, ","); 110 if (!token) 111 goto out; 112 113 if (kstrtol(token, 10, &digest_type)) 114 continue; 115 116 digest_name = chap_get_digest_name(digest_type); 117 if (!digest_name) 118 continue; 119 120 pr_debug("Selected %s Algorithm\n", digest_name); 121 if (chap_test_algorithm(digest_name) < 0) { 122 pr_err("failed to allocate %s algo\n", digest_name); 123 } else { 124 r = digest_type; 125 goto out; 126 } 127 } 128 out: 129 kfree(orig); 130 return r; 131 } 132 133 static void chap_close(struct iscsit_conn *conn) 134 { 135 kfree(conn->auth_protocol); 136 conn->auth_protocol = NULL; 137 } 138 139 static struct iscsi_chap *chap_server_open( 140 struct iscsit_conn *conn, 141 struct iscsi_node_auth *auth, 142 const char *a_str, 143 char *aic_str, 144 unsigned int *aic_len) 145 { 146 int digest_type; 147 struct iscsi_chap *chap; 148 149 if (!(auth->naf_flags & NAF_USERID_SET) || 150 !(auth->naf_flags & NAF_PASSWORD_SET)) { 151 pr_err("CHAP user or password not set for" 152 " Initiator ACL\n"); 153 return NULL; 154 } 155 156 conn->auth_protocol = kzalloc_obj(struct iscsi_chap); 157 if (!conn->auth_protocol) 158 return NULL; 159 160 chap = conn->auth_protocol; 161 digest_type = chap_check_algorithm(a_str); 162 switch (digest_type) { 163 case CHAP_DIGEST_MD5: 164 chap->digest_size = MD5_SIGNATURE_SIZE; 165 break; 166 case CHAP_DIGEST_SHA1: 167 chap->digest_size = SHA1_SIGNATURE_SIZE; 168 break; 169 case CHAP_DIGEST_SHA256: 170 chap->digest_size = SHA256_SIGNATURE_SIZE; 171 break; 172 case CHAP_DIGEST_SHA3_256: 173 chap->digest_size = SHA3_256_SIGNATURE_SIZE; 174 break; 175 case CHAP_DIGEST_UNKNOWN: 176 default: 177 pr_err("Unsupported CHAP_A value\n"); 178 chap_close(conn); 179 return NULL; 180 } 181 182 chap->digest_name = chap_get_digest_name(digest_type); 183 184 /* Tie the challenge length to the digest size */ 185 chap->challenge_len = chap->digest_size; 186 187 pr_debug("[server] Got CHAP_A=%d\n", digest_type); 188 *aic_len = sprintf(aic_str, "CHAP_A=%d", digest_type); 189 *aic_len += 1; 190 pr_debug("[server] Sending CHAP_A=%d\n", digest_type); 191 192 /* 193 * Set Identifier. 194 */ 195 chap->id = conn->tpg->tpg_chap_id++; 196 *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id); 197 *aic_len += 1; 198 pr_debug("[server] Sending CHAP_I=%d\n", chap->id); 199 /* 200 * Generate Challenge. 201 */ 202 if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) { 203 chap_close(conn); 204 return NULL; 205 } 206 207 return chap; 208 } 209 210 static const char base64_lookup_table[] = 211 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; 212 213 static int chap_base64_decode(u8 *dst, const char *src, size_t len) 214 { 215 int i, bits = 0, ac = 0; 216 const char *p; 217 u8 *cp = dst; 218 219 for (i = 0; i < len; i++) { 220 if (src[i] == '=') 221 return cp - dst; 222 223 p = strchr(base64_lookup_table, src[i]); 224 if (p == NULL || src[i] == 0) 225 return -2; 226 227 ac <<= 6; 228 ac += (p - base64_lookup_table); 229 bits += 6; 230 if (bits >= 8) { 231 *cp++ = (ac >> (bits - 8)) & 0xff; 232 ac &= ~(BIT(16) - BIT(bits - 8)); 233 bits -= 8; 234 } 235 } 236 if (ac) 237 return -1; 238 239 return cp - dst; 240 } 241 242 static int chap_server_compute_hash( 243 struct iscsit_conn *conn, 244 struct iscsi_node_auth *auth, 245 char *nr_in_ptr, 246 char *nr_out_ptr, 247 unsigned int *nr_out_len) 248 { 249 unsigned long id; 250 unsigned char id_as_uchar; 251 unsigned char type; 252 unsigned char identifier[10], *initiatorchg = NULL; 253 unsigned char *initiatorchg_binhex = NULL; 254 unsigned char *digest = NULL; 255 unsigned char *response = NULL; 256 unsigned char *client_digest = NULL; 257 unsigned char *server_digest = NULL; 258 unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH]; 259 size_t compare_len; 260 struct iscsi_chap *chap = conn->auth_protocol; 261 struct crypto_shash *tfm = NULL; 262 struct shash_desc *desc = NULL; 263 int auth_ret = -1, ret, initiatorchg_len; 264 265 digest = kzalloc(chap->digest_size, GFP_KERNEL); 266 if (!digest) { 267 pr_err("Unable to allocate the digest buffer\n"); 268 goto out; 269 } 270 271 response = kzalloc(chap->digest_size * 2 + 2, GFP_KERNEL); 272 if (!response) { 273 pr_err("Unable to allocate the response buffer\n"); 274 goto out; 275 } 276 277 client_digest = kzalloc(chap->digest_size, GFP_KERNEL); 278 if (!client_digest) { 279 pr_err("Unable to allocate the client_digest buffer\n"); 280 goto out; 281 } 282 283 server_digest = kzalloc(chap->digest_size, GFP_KERNEL); 284 if (!server_digest) { 285 pr_err("Unable to allocate the server_digest buffer\n"); 286 goto out; 287 } 288 289 memset(identifier, 0, 10); 290 memset(chap_n, 0, MAX_CHAP_N_SIZE); 291 memset(chap_r, 0, MAX_RESPONSE_LENGTH); 292 293 initiatorchg = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 294 if (!initiatorchg) { 295 pr_err("Unable to allocate challenge buffer\n"); 296 goto out; 297 } 298 299 initiatorchg_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 300 if (!initiatorchg_binhex) { 301 pr_err("Unable to allocate initiatorchg_binhex buffer\n"); 302 goto out; 303 } 304 /* 305 * Extract CHAP_N. 306 */ 307 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n, 308 &type) < 0) { 309 pr_err("Could not find CHAP_N.\n"); 310 goto out; 311 } 312 if (type == HEX) { 313 pr_err("Could not find CHAP_N.\n"); 314 goto out; 315 } 316 317 /* Include the terminating NULL in the compare */ 318 compare_len = strlen(auth->userid) + 1; 319 if (strncmp(chap_n, auth->userid, compare_len) != 0) { 320 pr_err("CHAP_N values do not match!\n"); 321 goto out; 322 } 323 pr_debug("[server] Got CHAP_N=%s\n", chap_n); 324 /* 325 * Extract CHAP_R. 326 */ 327 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r, 328 &type) < 0) { 329 pr_err("Could not find CHAP_R.\n"); 330 goto out; 331 } 332 333 switch (type) { 334 case HEX: 335 if (strlen(chap_r) != chap->digest_size * 2) { 336 pr_err("Malformed CHAP_R\n"); 337 goto out; 338 } 339 if (hex2bin(client_digest, chap_r, chap->digest_size) < 0) { 340 pr_err("Malformed CHAP_R: invalid HEX\n"); 341 goto out; 342 } 343 break; 344 case BASE64: { 345 size_t r_len = strlen(chap_r); 346 347 while (r_len > 0 && chap_r[r_len - 1] == '=') 348 r_len--; 349 if (r_len > DIV_ROUND_UP(chap->digest_size * 4, 3)) { 350 pr_err("Malformed CHAP_R: base64 payload too long\n"); 351 goto out; 352 } 353 if (chap_base64_decode(client_digest, chap_r, strlen(chap_r)) != 354 chap->digest_size) { 355 pr_err("Malformed CHAP_R: invalid BASE64\n"); 356 goto out; 357 } 358 break; 359 } 360 default: 361 pr_err("Could not find CHAP_R\n"); 362 goto out; 363 } 364 365 pr_debug("[server] Got CHAP_R=%s\n", chap_r); 366 367 tfm = crypto_alloc_shash(chap->digest_name, 0, 0); 368 if (IS_ERR(tfm)) { 369 tfm = NULL; 370 pr_err("Unable to allocate struct crypto_shash\n"); 371 goto out; 372 } 373 374 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); 375 if (!desc) { 376 pr_err("Unable to allocate struct shash_desc\n"); 377 goto out; 378 } 379 380 desc->tfm = tfm; 381 382 ret = crypto_shash_init(desc); 383 if (ret < 0) { 384 pr_err("crypto_shash_init() failed\n"); 385 goto out; 386 } 387 388 ret = crypto_shash_update(desc, &chap->id, 1); 389 if (ret < 0) { 390 pr_err("crypto_shash_update() failed for id\n"); 391 goto out; 392 } 393 394 ret = crypto_shash_update(desc, (char *)&auth->password, 395 strlen(auth->password)); 396 if (ret < 0) { 397 pr_err("crypto_shash_update() failed for password\n"); 398 goto out; 399 } 400 401 ret = crypto_shash_finup(desc, chap->challenge, 402 chap->challenge_len, server_digest); 403 if (ret < 0) { 404 pr_err("crypto_shash_finup() failed for challenge\n"); 405 goto out; 406 } 407 408 bin2hex(response, server_digest, chap->digest_size); 409 pr_debug("[server] %s Server Digest: %s\n", 410 chap->digest_name, response); 411 412 if (crypto_memneq(server_digest, client_digest, chap->digest_size)) { 413 pr_debug("[server] %s Digests do not match!\n\n", 414 chap->digest_name); 415 goto out; 416 } else 417 pr_debug("[server] %s Digests match, CHAP connection" 418 " successful.\n\n", chap->digest_name); 419 /* 420 * One way authentication has succeeded, return now if mutual 421 * authentication is not enabled. 422 */ 423 if (!auth->authenticate_target) { 424 auth_ret = 0; 425 goto out; 426 } 427 /* 428 * Get CHAP_I. 429 */ 430 ret = extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type); 431 if (ret == -ENOENT) { 432 pr_debug("Could not find CHAP_I. Initiator uses One way authentication.\n"); 433 auth_ret = 0; 434 goto out; 435 } 436 if (ret < 0) { 437 pr_err("Could not find CHAP_I.\n"); 438 goto out; 439 } 440 441 if (type == HEX) 442 ret = kstrtoul(identifier, 16, &id); 443 else if (type == DECIMAL) 444 ret = kstrtoul(identifier, 10, &id); 445 else 446 ret = -EINVAL; 447 448 if (ret < 0) { 449 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret); 450 goto out; 451 } 452 if (id > 255) { 453 pr_err("chap identifier: %lu greater than 255\n", id); 454 goto out; 455 } 456 /* 457 * RFC 1994 says Identifier is no more than octet (8 bits). 458 */ 459 pr_debug("[server] Got CHAP_I=%lu\n", id); 460 /* 461 * Get CHAP_C. 462 */ 463 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN, 464 initiatorchg, &type) < 0) { 465 pr_err("Could not find CHAP_C.\n"); 466 goto out; 467 } 468 469 switch (type) { 470 case HEX: 471 initiatorchg_len = DIV_ROUND_UP(strlen(initiatorchg), 2); 472 if (!initiatorchg_len) { 473 pr_err("Unable to convert incoming challenge\n"); 474 goto out; 475 } 476 if (initiatorchg_len > 1024) { 477 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n"); 478 goto out; 479 } 480 481 if (hex2bin(initiatorchg_binhex, initiatorchg, 482 initiatorchg_len) < 0) { 483 pr_err("Malformed CHAP_C: invalid HEX\n"); 484 goto out; 485 } 486 break; 487 case BASE64: 488 /* 489 * No overflow check needed: initiatorchg_binhex is 490 * CHAP_CHALLENGE_STR_LEN bytes and extract_param() caps 491 * initiatorchg at CHAP_CHALLENGE_STR_LEN characters, so 492 * the decoded output is at most DIV_ROUND_UP( 493 * (CHAP_CHALLENGE_STR_LEN - 1) * 3, 4) bytes, which is 494 * less than CHAP_CHALLENGE_STR_LEN. 495 */ 496 initiatorchg_len = chap_base64_decode(initiatorchg_binhex, 497 initiatorchg, 498 strlen(initiatorchg)); 499 if (initiatorchg_len < 0) { 500 pr_err("Malformed CHAP_C: invalid BASE64\n"); 501 goto out; 502 } 503 if (!initiatorchg_len) { 504 pr_err("Unable to convert incoming challenge\n"); 505 goto out; 506 } 507 if (initiatorchg_len > 1024) { 508 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n"); 509 goto out; 510 } 511 break; 512 default: 513 pr_err("Could not find CHAP_C.\n"); 514 goto out; 515 } 516 517 pr_debug("[server] Got CHAP_C=%s\n", initiatorchg); 518 /* 519 * During mutual authentication, the CHAP_C generated by the 520 * initiator must not match the original CHAP_C generated by 521 * the target. 522 */ 523 if (initiatorchg_len == chap->challenge_len && 524 !memcmp(initiatorchg_binhex, chap->challenge, 525 initiatorchg_len)) { 526 pr_err("initiator CHAP_C matches target CHAP_C, failing" 527 " login attempt\n"); 528 goto out; 529 } 530 /* 531 * Generate CHAP_N and CHAP_R for mutual authentication. 532 */ 533 ret = crypto_shash_init(desc); 534 if (ret < 0) { 535 pr_err("crypto_shash_init() failed\n"); 536 goto out; 537 } 538 539 /* To handle both endiannesses */ 540 id_as_uchar = id; 541 ret = crypto_shash_update(desc, &id_as_uchar, 1); 542 if (ret < 0) { 543 pr_err("crypto_shash_update() failed for id\n"); 544 goto out; 545 } 546 547 ret = crypto_shash_update(desc, auth->password_mutual, 548 strlen(auth->password_mutual)); 549 if (ret < 0) { 550 pr_err("crypto_shash_update() failed for" 551 " password_mutual\n"); 552 goto out; 553 } 554 /* 555 * Convert received challenge to binary hex. 556 */ 557 ret = crypto_shash_finup(desc, initiatorchg_binhex, initiatorchg_len, 558 digest); 559 if (ret < 0) { 560 pr_err("crypto_shash_finup() failed for ma challenge\n"); 561 goto out; 562 } 563 564 /* 565 * Generate CHAP_N and CHAP_R. 566 */ 567 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual); 568 *nr_out_len += 1; 569 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual); 570 /* 571 * Convert response from binary hex to ascii hext. 572 */ 573 bin2hex(response, digest, chap->digest_size); 574 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s", 575 response); 576 *nr_out_len += 1; 577 pr_debug("[server] Sending CHAP_R=0x%s\n", response); 578 auth_ret = 0; 579 out: 580 kfree_sensitive(desc); 581 if (tfm) 582 crypto_free_shash(tfm); 583 kfree(initiatorchg); 584 kfree(initiatorchg_binhex); 585 kfree(digest); 586 kfree(response); 587 kfree(server_digest); 588 kfree(client_digest); 589 return auth_ret; 590 } 591 592 u32 chap_main_loop( 593 struct iscsit_conn *conn, 594 struct iscsi_node_auth *auth, 595 char *in_text, 596 char *out_text, 597 int *in_len, 598 int *out_len) 599 { 600 struct iscsi_chap *chap = conn->auth_protocol; 601 602 if (!chap) { 603 chap = chap_server_open(conn, auth, in_text, out_text, out_len); 604 if (!chap) 605 return 2; 606 chap->chap_state = CHAP_STAGE_SERVER_AIC; 607 return 0; 608 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) { 609 convert_null_to_semi(in_text, *in_len); 610 if (chap_server_compute_hash(conn, auth, in_text, out_text, 611 out_len) < 0) { 612 chap_close(conn); 613 return 2; 614 } 615 if (auth->authenticate_target) 616 chap->chap_state = CHAP_STAGE_SERVER_NR; 617 else 618 *out_len = 0; 619 chap_close(conn); 620 return 1; 621 } 622 623 return 2; 624 } 625