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 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 }