drivers/target/iscsi/iscsi_target_auth.c

   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/random.h>
  24 #include <linux/scatterlist.h>
  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 int chap_gen_challenge(
  51         struct iscsi_conn *conn,
  52         int caller,
  53         char *c_str,
  54         unsigned int *c_len)
  55 {
  56         int ret;
  57         unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
  58         struct iscsi_chap *chap = conn->auth_protocol;
  59
  60         memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
  61
  62         ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH);
  63         if (unlikely(ret))
  64                 return ret;
  65         chap_binaryhex_to_asciihex(challenge_asciihex, chap->challenge,
  66                                 CHAP_CHALLENGE_LENGTH);
  67         /*
  68          * Set CHAP_C, and copy the generated challenge into c_str.
  69          */
  70         *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
  71         *c_len += 1;
  72
  73         pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
  74                         challenge_asciihex);
  75         return 0;
  76 }
  77
  78 static int chap_check_algorithm(const char *a_str)
  79 {
  80         char *tmp, *orig, *token;
  81
  82         tmp = kstrdup(a_str, GFP_KERNEL);
  83         if (!tmp) {
  84                 pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
  85                 return CHAP_DIGEST_UNKNOWN;
  86         }
  87         orig = tmp;
  88
  89         token = strsep(&tmp, "=");
  90         if (!token)
  91                 goto out;
  92
  93         if (strcmp(token, "CHAP_A")) {
  94                 pr_err("Unable to locate CHAP_A key\n");
  95                 goto out;
  96         }
  97         while (token) {
  98                 token = strsep(&tmp, ",");
  99                 if (!token)
 100                         goto out;
 101
 102                 if (!strncmp(token, "5", 1)) {
 103                         pr_debug("Selected MD5 Algorithm\n");
 104                         kfree(orig);
 105                         return CHAP_DIGEST_MD5;
 106                 }
 107         }
 108 out:
 109         kfree(orig);
 110         return CHAP_DIGEST_UNKNOWN;
 111 }
 112
 113 static struct iscsi_chap *chap_server_open(
 114         struct iscsi_conn *conn,
 115         struct iscsi_node_auth *auth,
 116         const char *a_str,
 117         char *aic_str,
 118         unsigned int *aic_len)
 119 {
 120         int ret;
 121         struct iscsi_chap *chap;
 122
 123         if (!(auth->naf_flags & NAF_USERID_SET) ||
 124             !(auth->naf_flags & NAF_PASSWORD_SET)) {
 125                 pr_err("CHAP user or password not set for"
 126                                 " Initiator ACL\n");
 127                 return NULL;
 128         }
 129
 130         conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
 131         if (!conn->auth_protocol)
 132                 return NULL;
 133
 134         chap = conn->auth_protocol;
 135         ret = chap_check_algorithm(a_str);
 136         switch (ret) {
 137         case CHAP_DIGEST_MD5:
 138                 pr_debug("[server] Got CHAP_A=5\n");
 139                 /*
 140                  * Send back CHAP_A set to MD5.
 141                 */
 142                 *aic_len = sprintf(aic_str, "CHAP_A=5");
 143                 *aic_len += 1;
 144                 chap->digest_type = CHAP_DIGEST_MD5;
 145                 pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type);
 146                 break;
 147         case CHAP_DIGEST_UNKNOWN:
 148         default:
 149                 pr_err("Unsupported CHAP_A value\n");
 150                 kfree(conn->auth_protocol);
 151                 return NULL;
 152         }
 153
 154         /*
 155          * Set Identifier.
 156          */
 157         chap->id = conn->tpg->tpg_chap_id++;
 158         *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
 159         *aic_len += 1;
 160         pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
 161         /*
 162          * Generate Challenge.
 163          */
 164         if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) {
 165                 kfree(conn->auth_protocol);
 166                 return NULL;
 167         }
 168
 169         return chap;
 170 }
 171
 172 static void chap_close(struct iscsi_conn *conn)
 173 {
 174         kfree(conn->auth_protocol);
 175         conn->auth_protocol = NULL;
 176 }
 177
 178 static int chap_server_compute_md5(
 179         struct iscsi_conn *conn,
 180         struct iscsi_node_auth *auth,
 181         char *nr_in_ptr,
 182         char *nr_out_ptr,
 183         unsigned int *nr_out_len)
 184 {
 185         unsigned long id;
 186         unsigned char id_as_uchar;
 187         unsigned char digest[MD5_SIGNATURE_SIZE];
 188         unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
 189         unsigned char identifier[10], *challenge = NULL;
 190         unsigned char *challenge_binhex = NULL;
 191         unsigned char client_digest[MD5_SIGNATURE_SIZE];
 192         unsigned char server_digest[MD5_SIGNATURE_SIZE];
 193         unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
 194         size_t compare_len;
 195         struct iscsi_chap *chap = conn->auth_protocol;
 196         struct crypto_shash *tfm = NULL;
 197         struct shash_desc *desc = NULL;
 198         int auth_ret = -1, ret, challenge_len;
 199
 200         memset(identifier, 0, 10);
 201         memset(chap_n, 0, MAX_CHAP_N_SIZE);
 202         memset(chap_r, 0, MAX_RESPONSE_LENGTH);
 203         memset(digest, 0, MD5_SIGNATURE_SIZE);
 204         memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
 205         memset(client_digest, 0, MD5_SIGNATURE_SIZE);
 206         memset(server_digest, 0, MD5_SIGNATURE_SIZE);
 207
 208         challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 209         if (!challenge) {
 210                 pr_err("Unable to allocate challenge buffer\n");
 211                 goto out;
 212         }
 213
 214         challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 215         if (!challenge_binhex) {
 216                 pr_err("Unable to allocate challenge_binhex buffer\n");
 217                 goto out;
 218         }
 219         /*
 220          * Extract CHAP_N.
 221          */
 222         if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
 223                                 &type) < 0) {
 224                 pr_err("Could not find CHAP_N.\n");
 225                 goto out;
 226         }
 227         if (type == HEX) {
 228                 pr_err("Could not find CHAP_N.\n");
 229                 goto out;
 230         }
 231
 232         /* Include the terminating NULL in the compare */
 233         compare_len = strlen(auth->userid) + 1;
 234         if (strncmp(chap_n, auth->userid, compare_len) != 0) {
 235                 pr_err("CHAP_N values do not match!\n");
 236                 goto out;
 237         }
 238         pr_debug("[server] Got CHAP_N=%s\n", chap_n);
 239         /*
 240          * Extract CHAP_R.
 241          */
 242         if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
 243                                 &type) < 0) {
 244                 pr_err("Could not find CHAP_R.\n");
 245                 goto out;
 246         }
 247         if (type != HEX) {
 248                 pr_err("Could not find CHAP_R.\n");
 249                 goto out;
 250         }
 251
 252         pr_debug("[server] Got CHAP_R=%s\n", chap_r);
 253         chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
 254
 255         tfm = crypto_alloc_shash("md5", 0, 0);
 256         if (IS_ERR(tfm)) {
 257                 tfm = NULL;
 258                 pr_err("Unable to allocate struct crypto_shash\n");
 259                 goto out;
 260         }
 261
 262         desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
 263         if (!desc) {
 264                 pr_err("Unable to allocate struct shash_desc\n");
 265                 goto out;
 266         }
 267
 268         desc->tfm = tfm;
 269         desc->flags = 0;
 270
 271         ret = crypto_shash_init(desc);
 272         if (ret < 0) {
 273                 pr_err("crypto_shash_init() failed\n");
 274                 goto out;
 275         }
 276
 277         ret = crypto_shash_update(desc, &chap->id, 1);
 278         if (ret < 0) {
 279                 pr_err("crypto_shash_update() failed for id\n");
 280                 goto out;
 281         }
 282
 283         ret = crypto_shash_update(desc, (char *)&auth->password,
 284                                   strlen(auth->password));
 285         if (ret < 0) {
 286                 pr_err("crypto_shash_update() failed for password\n");
 287                 goto out;
 288         }
 289
 290         ret = crypto_shash_finup(desc, chap->challenge,
 291                                  CHAP_CHALLENGE_LENGTH, server_digest);
 292         if (ret < 0) {
 293                 pr_err("crypto_shash_finup() failed for challenge\n");
 294                 goto out;
 295         }
 296
 297         chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
 298         pr_debug("[server] MD5 Server Digest: %s\n", response);
 299
 300         if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
 301                 pr_debug("[server] MD5 Digests do not match!\n\n");
 302                 goto out;
 303         } else
 304                 pr_debug("[server] MD5 Digests match, CHAP connection"
 305                                 " successful.\n\n");
 306         /*
 307          * One way authentication has succeeded, return now if mutual
 308          * authentication is not enabled.
 309          */
 310         if (!auth->authenticate_target) {
 311                 auth_ret = 0;
 312                 goto out;
 313         }
 314         /*
 315          * Get CHAP_I.
 316          */
 317         if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
 318                 pr_err("Could not find CHAP_I.\n");
 319                 goto out;
 320         }
 321
 322         if (type == HEX)
 323                 ret = kstrtoul(&identifier[2], 0, &id);
 324         else
 325                 ret = kstrtoul(identifier, 0, &id);
 326
 327         if (ret < 0) {
 328                 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
 329                 goto out;
 330         }
 331         if (id > 255) {
 332                 pr_err("chap identifier: %lu greater than 255\n", id);
 333                 goto out;
 334         }
 335         /*
 336          * RFC 1994 says Identifier is no more than octet (8 bits).
 337          */
 338         pr_debug("[server] Got CHAP_I=%lu\n", id);
 339         /*
 340          * Get CHAP_C.
 341          */
 342         if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
 343                         challenge, &type) < 0) {
 344                 pr_err("Could not find CHAP_C.\n");
 345                 goto out;
 346         }
 347
 348         if (type != HEX) {
 349                 pr_err("Could not find CHAP_C.\n");
 350                 goto out;
 351         }
 352         pr_debug("[server] Got CHAP_C=%s\n", challenge);
 353         challenge_len = chap_string_to_hex(challenge_binhex, challenge,
 354                                 strlen(challenge));
 355         if (!challenge_len) {
 356                 pr_err("Unable to convert incoming challenge\n");
 357                 goto out;
 358         }
 359         if (challenge_len > 1024) {
 360                 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
 361                 goto out;
 362         }
 363         /*
 364          * During mutual authentication, the CHAP_C generated by the
 365          * initiator must not match the original CHAP_C generated by
 366          * the target.
 367          */
 368         if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
 369                 pr_err("initiator CHAP_C matches target CHAP_C, failing"
 370                        " login attempt\n");
 371                 goto out;
 372         }
 373         /*
 374          * Generate CHAP_N and CHAP_R for mutual authentication.
 375          */
 376         ret = crypto_shash_init(desc);
 377         if (ret < 0) {
 378                 pr_err("crypto_shash_init() failed\n");
 379                 goto out;
 380         }
 381
 382         /* To handle both endiannesses */
 383         id_as_uchar = id;
 384         ret = crypto_shash_update(desc, &id_as_uchar, 1);
 385         if (ret < 0) {
 386                 pr_err("crypto_shash_update() failed for id\n");
 387                 goto out;
 388         }
 389
 390         ret = crypto_shash_update(desc, auth->password_mutual,
 391                                   strlen(auth->password_mutual));
 392         if (ret < 0) {
 393                 pr_err("crypto_shash_update() failed for"
 394                                 " password_mutual\n");
 395                 goto out;
 396         }
 397         /*
 398          * Convert received challenge to binary hex.
 399          */
 400         ret = crypto_shash_finup(desc, challenge_binhex, challenge_len,
 401                                  digest);
 402         if (ret < 0) {
 403                 pr_err("crypto_shash_finup() failed for ma challenge\n");
 404                 goto out;
 405         }
 406
 407         /*
 408          * Generate CHAP_N and CHAP_R.
 409          */
 410         *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
 411         *nr_out_len += 1;
 412         pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
 413         /*
 414          * Convert response from binary hex to ascii hext.
 415          */
 416         chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE);
 417         *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
 418                         response);
 419         *nr_out_len += 1;
 420         pr_debug("[server] Sending CHAP_R=0x%s\n", response);
 421         auth_ret = 0;
 422 out:
 423         kzfree(desc);
 424         crypto_free_shash(tfm);
 425         kfree(challenge);
 426         kfree(challenge_binhex);
 427         return auth_ret;
 428 }
 429
 430 static int chap_got_response(
 431         struct iscsi_conn *conn,
 432         struct iscsi_node_auth *auth,
 433         char *nr_in_ptr,
 434         char *nr_out_ptr,
 435         unsigned int *nr_out_len)
 436 {
 437         struct iscsi_chap *chap = conn->auth_protocol;
 438
 439         switch (chap->digest_type) {
 440         case CHAP_DIGEST_MD5:
 441                 if (chap_server_compute_md5(conn, auth, nr_in_ptr,
 442                                 nr_out_ptr, nr_out_len) < 0)
 443                         return -1;
 444                 return 0;
 445         default:
 446                 pr_err("Unknown CHAP digest type %d!\n",
 447                                 chap->digest_type);
 448                 return -1;
 449         }
 450 }
 451
 452 u32 chap_main_loop(
 453         struct iscsi_conn *conn,
 454         struct iscsi_node_auth *auth,
 455         char *in_text,
 456         char *out_text,
 457         int *in_len,
 458         int *out_len)
 459 {
 460         struct iscsi_chap *chap = conn->auth_protocol;
 461
 462         if (!chap) {
 463                 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
 464                 if (!chap)
 465                         return 2;
 466                 chap->chap_state = CHAP_STAGE_SERVER_AIC;
 467                 return 0;
 468         } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
 469                 convert_null_to_semi(in_text, *in_len);
 470                 if (chap_got_response(conn, auth, in_text, out_text,
 471                                 out_len) < 0) {
 472                         chap_close(conn);
 473                         return 2;
 474                 }
 475                 if (auth->authenticate_target)
 476                         chap->chap_state = CHAP_STAGE_SERVER_NR;
 477                 else
 478                         *out_len = 0;
 479                 chap_close(conn);
 480                 return 1;
 481         }
 482
 483         return 2;
 484 }