drivers/target/iscsi/iscsi_target_auth.c

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