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