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_gen_challenge(
  30         struct iscsi_conn *conn,
  31         int caller,
  32         char *c_str,
  33         unsigned int *c_len)
  34 {
  35         int ret;
  36         unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
  37         struct iscsi_chap *chap = conn->auth_protocol;
  38
  39         memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
  40
  41         ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH);
  42         if (unlikely(ret))
  43                 return ret;
  44         bin2hex(challenge_asciihex, chap->challenge,
  45                                 CHAP_CHALLENGE_LENGTH);
  46         /*
  47          * Set CHAP_C, and copy the generated challenge into c_str.
  48          */
  49         *c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
  50         *c_len += 1;
  51
  52         pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
  53                         challenge_asciihex);
  54         return 0;
  55 }
  56
  57 static int chap_check_algorithm(const char *a_str)
  58 {
  59         char *tmp, *orig, *token;
  60
  61         tmp = kstrdup(a_str, GFP_KERNEL);
  62         if (!tmp) {
  63                 pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
  64                 return CHAP_DIGEST_UNKNOWN;
  65         }
  66         orig = tmp;
  67
  68         token = strsep(&tmp, "=");
  69         if (!token)
  70                 goto out;
  71
  72         if (strcmp(token, "CHAP_A")) {
  73                 pr_err("Unable to locate CHAP_A key\n");
  74                 goto out;
  75         }
  76         while (token) {
  77                 token = strsep(&tmp, ",");
  78                 if (!token)
  79                         goto out;
  80
  81                 if (!strncmp(token, "5", 1)) {
  82                         pr_debug("Selected MD5 Algorithm\n");
  83                         kfree(orig);
  84                         return CHAP_DIGEST_MD5;
  85                 }
  86         }
  87 out:
  88         kfree(orig);
  89         return CHAP_DIGEST_UNKNOWN;
  90 }
  91
  92 static struct iscsi_chap *chap_server_open(
  93         struct iscsi_conn *conn,
  94         struct iscsi_node_auth *auth,
  95         const char *a_str,
  96         char *aic_str,
  97         unsigned int *aic_len)
  98 {
  99         int ret;
 100         struct iscsi_chap *chap;
 101
 102         if (!(auth->naf_flags & NAF_USERID_SET) ||
 103             !(auth->naf_flags & NAF_PASSWORD_SET)) {
 104                 pr_err("CHAP user or password not set for"
 105                                 " Initiator ACL\n");
 106                 return NULL;
 107         }
 108
 109         conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
 110         if (!conn->auth_protocol)
 111                 return NULL;
 112
 113         chap = conn->auth_protocol;
 114         ret = chap_check_algorithm(a_str);
 115         switch (ret) {
 116         case CHAP_DIGEST_MD5:
 117                 pr_debug("[server] Got CHAP_A=5\n");
 118                 /*
 119                  * Send back CHAP_A set to MD5.
 120                 */
 121                 *aic_len = sprintf(aic_str, "CHAP_A=5");
 122                 *aic_len += 1;
 123                 chap->digest_type = CHAP_DIGEST_MD5;
 124                 pr_debug("[server] Sending CHAP_A=%d\n", chap->digest_type);
 125                 break;
 126         case CHAP_DIGEST_UNKNOWN:
 127         default:
 128                 pr_err("Unsupported CHAP_A value\n");
 129                 kfree(conn->auth_protocol);
 130                 return NULL;
 131         }
 132
 133         /*
 134          * Set Identifier.
 135          */
 136         chap->id = conn->tpg->tpg_chap_id++;
 137         *aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
 138         *aic_len += 1;
 139         pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
 140         /*
 141          * Generate Challenge.
 142          */
 143         if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) {
 144                 kfree(conn->auth_protocol);
 145                 return NULL;
 146         }
 147
 148         return chap;
 149 }
 150
 151 static void chap_close(struct iscsi_conn *conn)
 152 {
 153         kfree(conn->auth_protocol);
 154         conn->auth_protocol = NULL;
 155 }
 156
 157 static int chap_server_compute_md5(
 158         struct iscsi_conn *conn,
 159         struct iscsi_node_auth *auth,
 160         char *nr_in_ptr,
 161         char *nr_out_ptr,
 162         unsigned int *nr_out_len)
 163 {
 164         unsigned long id;
 165         unsigned char id_as_uchar;
 166         unsigned char digest[MD5_SIGNATURE_SIZE];
 167         unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
 168         unsigned char identifier[10], *challenge = NULL;
 169         unsigned char *challenge_binhex = NULL;
 170         unsigned char client_digest[MD5_SIGNATURE_SIZE];
 171         unsigned char server_digest[MD5_SIGNATURE_SIZE];
 172         unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
 173         size_t compare_len;
 174         struct iscsi_chap *chap = conn->auth_protocol;
 175         struct crypto_shash *tfm = NULL;
 176         struct shash_desc *desc = NULL;
 177         int auth_ret = -1, ret, challenge_len;
 178
 179         memset(identifier, 0, 10);
 180         memset(chap_n, 0, MAX_CHAP_N_SIZE);
 181         memset(chap_r, 0, MAX_RESPONSE_LENGTH);
 182         memset(digest, 0, MD5_SIGNATURE_SIZE);
 183         memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
 184         memset(client_digest, 0, MD5_SIGNATURE_SIZE);
 185         memset(server_digest, 0, MD5_SIGNATURE_SIZE);
 186
 187         challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 188         if (!challenge) {
 189                 pr_err("Unable to allocate challenge buffer\n");
 190                 goto out;
 191         }
 192
 193         challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 194         if (!challenge_binhex) {
 195                 pr_err("Unable to allocate challenge_binhex buffer\n");
 196                 goto out;
 197         }
 198         /*
 199          * Extract CHAP_N.
 200          */
 201         if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
 202                                 &type) < 0) {
 203                 pr_err("Could not find CHAP_N.\n");
 204                 goto out;
 205         }
 206         if (type == HEX) {
 207                 pr_err("Could not find CHAP_N.\n");
 208                 goto out;
 209         }
 210
 211         /* Include the terminating NULL in the compare */
 212         compare_len = strlen(auth->userid) + 1;
 213         if (strncmp(chap_n, auth->userid, compare_len) != 0) {
 214                 pr_err("CHAP_N values do not match!\n");
 215                 goto out;
 216         }
 217         pr_debug("[server] Got CHAP_N=%s\n", chap_n);
 218         /*
 219          * Extract CHAP_R.
 220          */
 221         if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
 222                                 &type) < 0) {
 223                 pr_err("Could not find CHAP_R.\n");
 224                 goto out;
 225         }
 226         if (type != HEX) {
 227                 pr_err("Could not find CHAP_R.\n");
 228                 goto out;
 229         }
 230         if (strlen(chap_r) != MD5_SIGNATURE_SIZE * 2) {
 231                 pr_err("Malformed CHAP_R\n");
 232                 goto out;
 233         }
 234         if (hex2bin(client_digest, chap_r, MD5_SIGNATURE_SIZE) < 0) {
 235                 pr_err("Malformed CHAP_R\n");
 236                 goto out;
 237         }
 238
 239         pr_debug("[server] Got CHAP_R=%s\n", chap_r);
 240
 241         tfm = crypto_alloc_shash("md5", 0, 0);
 242         if (IS_ERR(tfm)) {
 243                 tfm = NULL;
 244                 pr_err("Unable to allocate struct crypto_shash\n");
 245                 goto out;
 246         }
 247
 248         desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
 249         if (!desc) {
 250                 pr_err("Unable to allocate struct shash_desc\n");
 251                 goto out;
 252         }
 253
 254         desc->tfm = tfm;
 255         desc->flags = 0;
 256
 257         ret = crypto_shash_init(desc);
 258         if (ret < 0) {
 259                 pr_err("crypto_shash_init() failed\n");
 260                 goto out;
 261         }
 262
 263         ret = crypto_shash_update(desc, &chap->id, 1);
 264         if (ret < 0) {
 265                 pr_err("crypto_shash_update() failed for id\n");
 266                 goto out;
 267         }
 268
 269         ret = crypto_shash_update(desc, (char *)&auth->password,
 270                                   strlen(auth->password));
 271         if (ret < 0) {
 272                 pr_err("crypto_shash_update() failed for password\n");
 273                 goto out;
 274         }
 275
 276         ret = crypto_shash_finup(desc, chap->challenge,
 277                                  CHAP_CHALLENGE_LENGTH, server_digest);
 278         if (ret < 0) {
 279                 pr_err("crypto_shash_finup() failed for challenge\n");
 280                 goto out;
 281         }
 282
 283         bin2hex(response, server_digest, MD5_SIGNATURE_SIZE);
 284         pr_debug("[server] MD5 Server Digest: %s\n", response);
 285
 286         if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
 287                 pr_debug("[server] MD5 Digests do not match!\n\n");
 288                 goto out;
 289         } else
 290                 pr_debug("[server] MD5 Digests match, CHAP connection"
 291                                 " successful.\n\n");
 292         /*
 293          * One way authentication has succeeded, return now if mutual
 294          * authentication is not enabled.
 295          */
 296         if (!auth->authenticate_target) {
 297                 auth_ret = 0;
 298                 goto out;
 299         }
 300         /*
 301          * Get CHAP_I.
 302          */
 303         if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
 304                 pr_err("Could not find CHAP_I.\n");
 305                 goto out;
 306         }
 307
 308         if (type == HEX)
 309                 ret = kstrtoul(&identifier[2], 0, &id);
 310         else
 311                 ret = kstrtoul(identifier, 0, &id);
 312
 313         if (ret < 0) {
 314                 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
 315                 goto out;
 316         }
 317         if (id > 255) {
 318                 pr_err("chap identifier: %lu greater than 255\n", id);
 319                 goto out;
 320         }
 321         /*
 322          * RFC 1994 says Identifier is no more than octet (8 bits).
 323          */
 324         pr_debug("[server] Got CHAP_I=%lu\n", id);
 325         /*
 326          * Get CHAP_C.
 327          */
 328         if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
 329                         challenge, &type) < 0) {
 330                 pr_err("Could not find CHAP_C.\n");
 331                 goto out;
 332         }
 333
 334         if (type != HEX) {
 335                 pr_err("Could not find CHAP_C.\n");
 336                 goto out;
 337         }
 338         challenge_len = DIV_ROUND_UP(strlen(challenge), 2);
 339         if (!challenge_len) {
 340                 pr_err("Unable to convert incoming challenge\n");
 341                 goto out;
 342         }
 343         if (challenge_len > 1024) {
 344                 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
 345                 goto out;
 346         }
 347         if (hex2bin(challenge_binhex, challenge, challenge_len) < 0) {
 348                 pr_err("Malformed CHAP_C\n");
 349                 goto out;
 350         }
 351         pr_debug("[server] Got CHAP_C=%s\n", challenge);
 352         /*
 353          * During mutual authentication, the CHAP_C generated by the
 354          * initiator must not match the original CHAP_C generated by
 355          * the target.
 356          */
 357         if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
 358                 pr_err("initiator CHAP_C matches target CHAP_C, failing"
 359                        " login attempt\n");
 360                 goto out;
 361         }
 362         /*
 363          * Generate CHAP_N and CHAP_R for mutual authentication.
 364          */
 365         ret = crypto_shash_init(desc);
 366         if (ret < 0) {
 367                 pr_err("crypto_shash_init() failed\n");
 368                 goto out;
 369         }
 370
 371         /* To handle both endiannesses */
 372         id_as_uchar = id;
 373         ret = crypto_shash_update(desc, &id_as_uchar, 1);
 374         if (ret < 0) {
 375                 pr_err("crypto_shash_update() failed for id\n");
 376                 goto out;
 377         }
 378
 379         ret = crypto_shash_update(desc, auth->password_mutual,
 380                                   strlen(auth->password_mutual));
 381         if (ret < 0) {
 382                 pr_err("crypto_shash_update() failed for"
 383                                 " password_mutual\n");
 384                 goto out;
 385         }
 386         /*
 387          * Convert received challenge to binary hex.
 388          */
 389         ret = crypto_shash_finup(desc, challenge_binhex, challenge_len,
 390                                  digest);
 391         if (ret < 0) {
 392                 pr_err("crypto_shash_finup() failed for ma challenge\n");
 393                 goto out;
 394         }
 395
 396         /*
 397          * Generate CHAP_N and CHAP_R.
 398          */
 399         *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
 400         *nr_out_len += 1;
 401         pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
 402         /*
 403          * Convert response from binary hex to ascii hext.
 404          */
 405         bin2hex(response, digest, MD5_SIGNATURE_SIZE);
 406         *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
 407                         response);
 408         *nr_out_len += 1;
 409         pr_debug("[server] Sending CHAP_R=0x%s\n", response);
 410         auth_ret = 0;
 411 out:
 412         kzfree(desc);
 413         if (tfm)
 414                 crypto_free_shash(tfm);
 415         kfree(challenge);
 416         kfree(challenge_binhex);
 417         return auth_ret;
 418 }
 419
 420 static int chap_got_response(
 421         struct iscsi_conn *conn,
 422         struct iscsi_node_auth *auth,
 423         char *nr_in_ptr,
 424         char *nr_out_ptr,
 425         unsigned int *nr_out_len)
 426 {
 427         struct iscsi_chap *chap = conn->auth_protocol;
 428
 429         switch (chap->digest_type) {
 430         case CHAP_DIGEST_MD5:
 431                 if (chap_server_compute_md5(conn, auth, nr_in_ptr,
 432                                 nr_out_ptr, nr_out_len) < 0)
 433                         return -1;
 434                 return 0;
 435         default:
 436                 pr_err("Unknown CHAP digest type %d!\n",
 437                                 chap->digest_type);
 438                 return -1;
 439         }
 440 }
 441
 442 u32 chap_main_loop(
 443         struct iscsi_conn *conn,
 444         struct iscsi_node_auth *auth,
 445         char *in_text,
 446         char *out_text,
 447         int *in_len,
 448         int *out_len)
 449 {
 450         struct iscsi_chap *chap = conn->auth_protocol;
 451
 452         if (!chap) {
 453                 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
 454                 if (!chap)
 455                         return 2;
 456                 chap->chap_state = CHAP_STAGE_SERVER_AIC;
 457                 return 0;
 458         } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
 459                 convert_null_to_semi(in_text, *in_len);
 460                 if (chap_got_response(conn, auth, in_text, out_text,
 461                                 out_len) < 0) {
 462                         chap_close(conn);
 463                         return 2;
 464                 }
 465                 if (auth->authenticate_target)
 466                         chap->chap_state = CHAP_STAGE_SERVER_NR;
 467                 else
 468                         *out_len = 0;
 469                 chap_close(conn);
 470                 return 1;
 471         }
 472
 473         return 2;
 474 }