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 <linux/kernel.h> 13 #include <linux/string.h> 14 #include <linux/err.h> 15 #include <linux/random.h> 16 #include <linux/scatterlist.h> 17 #include <target/iscsi/iscsi_target_core.h> 18 #include "iscsi_target_nego.h" 19 #include "iscsi_target_auth.h" 20 21 static int chap_gen_challenge( 22 struct iscsi_conn *conn, 23 int caller, 24 char *c_str, 25 unsigned int *c_len) 26 { 27 int ret; 28 unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1]; 29 struct iscsi_chap *chap = conn->auth_protocol; 30 31 memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1); 32 33 ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH); 34 if (unlikely(ret)) 35 return ret; 36 bin2hex(challenge_asciihex, chap->challenge, 37 CHAP_CHALLENGE_LENGTH); 38 /* 39 * Set CHAP_C, and copy the generated challenge into c_str. 40 */ 41 *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex); 42 *c_len += 1; 43 44 pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client", 45 challenge_asciihex); 46 return 0; 47 } 48 49 static int chap_check_algorithm(const char *a_str) 50 { 51 char *tmp, *orig, *token; 52 53 tmp = kstrdup(a_str, GFP_KERNEL); 54 if (!tmp) { 55 pr_err("Memory allocation failed for CHAP_A temporary buffer\n"); 56 return CHAP_DIGEST_UNKNOWN; 57 } 58 orig = tmp; 59 60 token = strsep(&tmp, "="); 61 if (!token) 62 goto out; 63 64 if (strcmp(token, "CHAP_A")) { 65 pr_err("Unable to locate CHAP_A key\n"); 66 goto out; 67 } 68 while (token) { 69 token = strsep(&tmp, ","); 70 if (!token) 71 goto out; 72 73 if (!strncmp(token, "5", 1)) { 74 pr_debug("Selected MD5 Algorithm\n"); 75 kfree(orig); 76 return CHAP_DIGEST_MD5; 77 } 78 } 79 out: 80 kfree(orig); 81 return CHAP_DIGEST_UNKNOWN; 82 } 83 84 static void chap_close(struct iscsi_conn *conn) 85 { 86 kfree(conn->auth_protocol); 87 conn->auth_protocol = NULL; 88 } 89 90 static struct iscsi_chap *chap_server_open( 91 struct iscsi_conn *conn, 92 struct iscsi_node_auth *auth, 93 const char *a_str, 94 char *aic_str, 95 unsigned int *aic_len) 96 { 97 int ret; 98 struct iscsi_chap *chap; 99 100 if (!(auth->naf_flags & NAF_USERID_SET) || 101 !(auth->naf_flags & NAF_PASSWORD_SET)) { 102 pr_err("CHAP user or password not set for" 103 " Initiator ACL\n"); 104 return NULL; 105 } 106 107 conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL); 108 if (!conn->auth_protocol) 109 return NULL; 110 111 chap = conn->auth_protocol; 112 ret = chap_check_algorithm(a_str); 113 switch (ret) { 114 case CHAP_DIGEST_MD5: 115 pr_debug("[server] Got CHAP_A=5\n"); 116 /* 117 * Send back CHAP_A set to MD5. 118 */ 119 *aic_len = sprintf(aic_str, "CHAP_A=5"); 120 *aic_len += 1; 121 chap->digest_type = CHAP_DIGEST_MD5; 122 pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type); 123 break; 124 case CHAP_DIGEST_UNKNOWN: 125 default: 126 pr_err("Unsupported CHAP_A value\n"); 127 chap_close(conn); 128 return NULL; 129 } 130 131 /* 132 * Set Identifier. 133 */ 134 chap->id = conn->tpg->tpg_chap_id++; 135 *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id); 136 *aic_len += 1; 137 pr_debug("[server] Sending CHAP_I=%d\n", chap->id); 138 /* 139 * Generate Challenge. 140 */ 141 if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) { 142 chap_close(conn); 143 return NULL; 144 } 145 146 return chap; 147 } 148 149 static int chap_server_compute_md5( 150 struct iscsi_conn *conn, 151 struct iscsi_node_auth *auth, 152 char *nr_in_ptr, 153 char *nr_out_ptr, 154 unsigned int *nr_out_len) 155 { 156 unsigned long id; 157 unsigned char id_as_uchar; 158 unsigned char digest[MD5_SIGNATURE_SIZE]; 159 unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2]; 160 unsigned char identifier[10], *challenge = NULL; 161 unsigned char *challenge_binhex = NULL; 162 unsigned char client_digest[MD5_SIGNATURE_SIZE]; 163 unsigned char server_digest[MD5_SIGNATURE_SIZE]; 164 unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH]; 165 size_t compare_len; 166 struct iscsi_chap *chap = conn->auth_protocol; 167 struct crypto_shash *tfm = NULL; 168 struct shash_desc *desc = NULL; 169 int auth_ret = -1, ret, challenge_len; 170 171 memset(identifier, 0, 10); 172 memset(chap_n, 0, MAX_CHAP_N_SIZE); 173 memset(chap_r, 0, MAX_RESPONSE_LENGTH); 174 memset(digest, 0, MD5_SIGNATURE_SIZE); 175 memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2); 176 memset(client_digest, 0, MD5_SIGNATURE_SIZE); 177 memset(server_digest, 0, MD5_SIGNATURE_SIZE); 178 179 challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 180 if (!challenge) { 181 pr_err("Unable to allocate challenge buffer\n"); 182 goto out; 183 } 184 185 challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL); 186 if (!challenge_binhex) { 187 pr_err("Unable to allocate challenge_binhex buffer\n"); 188 goto out; 189 } 190 /* 191 * Extract CHAP_N. 192 */ 193 if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n, 194 &type) < 0) { 195 pr_err("Could not find CHAP_N.\n"); 196 goto out; 197 } 198 if (type == HEX) { 199 pr_err("Could not find CHAP_N.\n"); 200 goto out; 201 } 202 203 /* Include the terminating NULL in the compare */ 204 compare_len = strlen(auth->userid) + 1; 205 if (strncmp(chap_n, auth->userid, compare_len) != 0) { 206 pr_err("CHAP_N values do not match!\n"); 207 goto out; 208 } 209 pr_debug("[server] Got CHAP_N=%s\n", chap_n); 210 /* 211 * Extract CHAP_R. 212 */ 213 if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r, 214 &type) < 0) { 215 pr_err("Could not find CHAP_R.\n"); 216 goto out; 217 } 218 if (type != HEX) { 219 pr_err("Could not find CHAP_R.\n"); 220 goto out; 221 } 222 if (strlen(chap_r) != MD5_SIGNATURE_SIZE * 2) { 223 pr_err("Malformed CHAP_R\n"); 224 goto out; 225 } 226 if (hex2bin(client_digest, chap_r, MD5_SIGNATURE_SIZE) < 0) { 227 pr_err("Malformed CHAP_R\n"); 228 goto out; 229 } 230 231 pr_debug("[server] Got CHAP_R=%s\n", chap_r); 232 233 tfm = crypto_alloc_shash("md5", 0, 0); 234 if (IS_ERR(tfm)) { 235 tfm = NULL; 236 pr_err("Unable to allocate struct crypto_shash\n"); 237 goto out; 238 } 239 240 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); 241 if (!desc) { 242 pr_err("Unable to allocate struct shash_desc\n"); 243 goto out; 244 } 245 246 desc->tfm = tfm; 247 248 ret = crypto_shash_init(desc); 249 if (ret < 0) { 250 pr_err("crypto_shash_init() failed\n"); 251 goto out; 252 } 253 254 ret = crypto_shash_update(desc, &chap->id, 1); 255 if (ret < 0) { 256 pr_err("crypto_shash_update() failed for id\n"); 257 goto out; 258 } 259 260 ret = crypto_shash_update(desc, (char *)&auth->password, 261 strlen(auth->password)); 262 if (ret < 0) { 263 pr_err("crypto_shash_update() failed for password\n"); 264 goto out; 265 } 266 267 ret = crypto_shash_finup(desc, chap->challenge, 268 CHAP_CHALLENGE_LENGTH, server_digest); 269 if (ret < 0) { 270 pr_err("crypto_shash_finup() failed for challenge\n"); 271 goto out; 272 } 273 274 bin2hex(response, server_digest, MD5_SIGNATURE_SIZE); 275 pr_debug("[server] MD5 Server Digest: %s\n", response); 276 277 if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) { 278 pr_debug("[server] MD5 Digests do not match!\n\n"); 279 goto out; 280 } else 281 pr_debug("[server] MD5 Digests match, CHAP connection" 282 " successful.\n\n"); 283 /* 284 * One way authentication has succeeded, return now if mutual 285 * authentication is not enabled. 286 */ 287 if (!auth->authenticate_target) { 288 auth_ret = 0; 289 goto out; 290 } 291 /* 292 * Get CHAP_I. 293 */ 294 if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) { 295 pr_err("Could not find CHAP_I.\n"); 296 goto out; 297 } 298 299 if (type == HEX) 300 ret = kstrtoul(&identifier[2], 0, &id); 301 else 302 ret = kstrtoul(identifier, 0, &id); 303 304 if (ret < 0) { 305 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret); 306 goto out; 307 } 308 if (id > 255) { 309 pr_err("chap identifier: %lu greater than 255\n", id); 310 goto out; 311 } 312 /* 313 * RFC 1994 says Identifier is no more than octet (8 bits). 314 */ 315 pr_debug("[server] Got CHAP_I=%lu\n", id); 316 /* 317 * Get CHAP_C. 318 */ 319 if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN, 320 challenge, &type) < 0) { 321 pr_err("Could not find CHAP_C.\n"); 322 goto out; 323 } 324 325 if (type != HEX) { 326 pr_err("Could not find CHAP_C.\n"); 327 goto out; 328 } 329 challenge_len = DIV_ROUND_UP(strlen(challenge), 2); 330 if (!challenge_len) { 331 pr_err("Unable to convert incoming challenge\n"); 332 goto out; 333 } 334 if (challenge_len > 1024) { 335 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n"); 336 goto out; 337 } 338 if (hex2bin(challenge_binhex, challenge, challenge_len) < 0) { 339 pr_err("Malformed CHAP_C\n"); 340 goto out; 341 } 342 pr_debug("[server] Got CHAP_C=%s\n", challenge); 343 /* 344 * During mutual authentication, the CHAP_C generated by the 345 * initiator must not match the original CHAP_C generated by 346 * the target. 347 */ 348 if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) { 349 pr_err("initiator CHAP_C matches target CHAP_C, failing" 350 " login attempt\n"); 351 goto out; 352 } 353 /* 354 * Generate CHAP_N and CHAP_R for mutual authentication. 355 */ 356 ret = crypto_shash_init(desc); 357 if (ret < 0) { 358 pr_err("crypto_shash_init() failed\n"); 359 goto out; 360 } 361 362 /* To handle both endiannesses */ 363 id_as_uchar = id; 364 ret = crypto_shash_update(desc, &id_as_uchar, 1); 365 if (ret < 0) { 366 pr_err("crypto_shash_update() failed for id\n"); 367 goto out; 368 } 369 370 ret = crypto_shash_update(desc, auth->password_mutual, 371 strlen(auth->password_mutual)); 372 if (ret < 0) { 373 pr_err("crypto_shash_update() failed for" 374 " password_mutual\n"); 375 goto out; 376 } 377 /* 378 * Convert received challenge to binary hex. 379 */ 380 ret = crypto_shash_finup(desc, challenge_binhex, challenge_len, 381 digest); 382 if (ret < 0) { 383 pr_err("crypto_shash_finup() failed for ma challenge\n"); 384 goto out; 385 } 386 387 /* 388 * Generate CHAP_N and CHAP_R. 389 */ 390 *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual); 391 *nr_out_len += 1; 392 pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual); 393 /* 394 * Convert response from binary hex to ascii hext. 395 */ 396 bin2hex(response, digest, MD5_SIGNATURE_SIZE); 397 *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s", 398 response); 399 *nr_out_len += 1; 400 pr_debug("[server] Sending CHAP_R=0x%s\n", response); 401 auth_ret = 0; 402 out: 403 kzfree(desc); 404 if (tfm) 405 crypto_free_shash(tfm); 406 kfree(challenge); 407 kfree(challenge_binhex); 408 return auth_ret; 409 } 410 411 static int chap_got_response( 412 struct iscsi_conn *conn, 413 struct iscsi_node_auth *auth, 414 char *nr_in_ptr, 415 char *nr_out_ptr, 416 unsigned int *nr_out_len) 417 { 418 struct iscsi_chap *chap = conn->auth_protocol; 419 420 switch (chap->digest_type) { 421 case CHAP_DIGEST_MD5: 422 if (chap_server_compute_md5(conn, auth, nr_in_ptr, 423 nr_out_ptr, nr_out_len) < 0) 424 return -1; 425 return 0; 426 default: 427 pr_err("Unknown CHAP digest type %d!\n", 428 chap->digest_type); 429 return -1; 430 } 431 } 432 433 u32 chap_main_loop( 434 struct iscsi_conn *conn, 435 struct iscsi_node_auth *auth, 436 char *in_text, 437 char *out_text, 438 int *in_len, 439 int *out_len) 440 { 441 struct iscsi_chap *chap = conn->auth_protocol; 442 443 if (!chap) { 444 chap = chap_server_open(conn, auth, in_text, out_text, out_len); 445 if (!chap) 446 return 2; 447 chap->chap_state = CHAP_STAGE_SERVER_AIC; 448 return 0; 449 } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) { 450 convert_null_to_semi(in_text, *in_len); 451 if (chap_got_response(conn, auth, in_text, out_text, 452 out_len) < 0) { 453 chap_close(conn); 454 return 2; 455 } 456 if (auth->authenticate_target) 457 chap->chap_state = CHAP_STAGE_SERVER_NR; 458 else 459 *out_len = 0; 460 chap_close(conn); 461 return 1; 462 } 463 464 return 2; 465 } 466