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 <linux/kernel.h>
  20 #include <linux/string.h>
  21 #include <linux/crypto.h>
  22 #include <linux/err.h>
  23 #include <linux/scatterlist.h>
  24
  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_hash *tfm;
 189         struct hash_desc desc;
 190         struct scatterlist sg;
 191         int auth_ret = -1, ret, challenge_len;
 192
 193         memset(identifier, 0, 10);
 194         memset(chap_n, 0, MAX_CHAP_N_SIZE);
 195         memset(chap_r, 0, MAX_RESPONSE_LENGTH);
 196         memset(digest, 0, MD5_SIGNATURE_SIZE);
 197         memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
 198         memset(client_digest, 0, MD5_SIGNATURE_SIZE);
 199         memset(server_digest, 0, MD5_SIGNATURE_SIZE);
 200
 201         challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 202         if (!challenge) {
 203                 pr_err("Unable to allocate challenge buffer\n");
 204                 goto out;
 205         }
 206
 207         challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
 208         if (!challenge_binhex) {
 209                 pr_err("Unable to allocate challenge_binhex buffer\n");
 210                 goto out;
 211         }
 212         /*
 213          * Extract CHAP_N.
 214          */
 215         if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
 216                                 &type) < 0) {
 217                 pr_err("Could not find CHAP_N.\n");
 218                 goto out;
 219         }
 220         if (type == HEX) {
 221                 pr_err("Could not find CHAP_N.\n");
 222                 goto out;
 223         }
 224
 225         /* Include the terminating NULL in the compare */
 226         compare_len = strlen(auth->userid) + 1;
 227         if (strncmp(chap_n, auth->userid, compare_len) != 0) {
 228                 pr_err("CHAP_N values do not match!\n");
 229                 goto out;
 230         }
 231         pr_debug("[server] Got CHAP_N=%s\n", chap_n);
 232         /*
 233          * Extract CHAP_R.
 234          */
 235         if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
 236                                 &type) < 0) {
 237                 pr_err("Could not find CHAP_R.\n");
 238                 goto out;
 239         }
 240         if (type != HEX) {
 241                 pr_err("Could not find CHAP_R.\n");
 242                 goto out;
 243         }
 244
 245         pr_debug("[server] Got CHAP_R=%s\n", chap_r);
 246         chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
 247
 248         tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
 249         if (IS_ERR(tfm)) {
 250                 pr_err("Unable to allocate struct crypto_hash\n");
 251                 goto out;
 252         }
 253         desc.tfm = tfm;
 254         desc.flags = 0;
 255
 256         ret = crypto_hash_init(&desc);
 257         if (ret < 0) {
 258                 pr_err("crypto_hash_init() failed\n");
 259                 crypto_free_hash(tfm);
 260                 goto out;
 261         }
 262
 263         sg_init_one(&sg, &chap->id, 1);
 264         ret = crypto_hash_update(&desc, &sg, 1);
 265         if (ret < 0) {
 266                 pr_err("crypto_hash_update() failed for id\n");
 267                 crypto_free_hash(tfm);
 268                 goto out;
 269         }
 270
 271         sg_init_one(&sg, &auth->password, strlen(auth->password));
 272         ret = crypto_hash_update(&desc, &sg, strlen(auth->password));
 273         if (ret < 0) {
 274                 pr_err("crypto_hash_update() failed for password\n");
 275                 crypto_free_hash(tfm);
 276                 goto out;
 277         }
 278
 279         sg_init_one(&sg, chap->challenge, CHAP_CHALLENGE_LENGTH);
 280         ret = crypto_hash_update(&desc, &sg, CHAP_CHALLENGE_LENGTH);
 281         if (ret < 0) {
 282                 pr_err("crypto_hash_update() failed for challenge\n");
 283                 crypto_free_hash(tfm);
 284                 goto out;
 285         }
 286
 287         ret = crypto_hash_final(&desc, server_digest);
 288         if (ret < 0) {
 289                 pr_err("crypto_hash_final() failed for server digest\n");
 290                 crypto_free_hash(tfm);
 291                 goto out;
 292         }
 293         crypto_free_hash(tfm);
 294
 295         chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
 296         pr_debug("[server] MD5 Server Digest: %s\n", response);
 297
 298         if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
 299                 pr_debug("[server] MD5 Digests do not match!\n\n");
 300                 goto out;
 301         } else
 302                 pr_debug("[server] MD5 Digests match, CHAP connetication"
 303                                 " successful.\n\n");
 304         /*
 305          * One way authentication has succeeded, return now if mutual
 306          * authentication is not enabled.
 307          */
 308         if (!auth->authenticate_target) {
 309                 kfree(challenge);
 310                 kfree(challenge_binhex);
 311                 return 0;
 312         }
 313         /*
 314          * Get CHAP_I.
 315          */
 316         if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
 317                 pr_err("Could not find CHAP_I.\n");
 318                 goto out;
 319         }
 320
 321         if (type == HEX)
 322                 ret = kstrtoul(&identifier[2], 0, &id);
 323         else
 324                 ret = kstrtoul(identifier, 0, &id);
 325
 326         if (ret < 0) {
 327                 pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
 328                 goto out;
 329         }
 330         if (id > 255) {
 331                 pr_err("chap identifier: %lu greater than 255\n", id);
 332                 goto out;
 333         }
 334         /*
 335          * RFC 1994 says Identifier is no more than octet (8 bits).
 336          */
 337         pr_debug("[server] Got CHAP_I=%lu\n", id);
 338         /*
 339          * Get CHAP_C.
 340          */
 341         if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
 342                         challenge, &type) < 0) {
 343                 pr_err("Could not find CHAP_C.\n");
 344                 goto out;
 345         }
 346
 347         if (type != HEX) {
 348                 pr_err("Could not find CHAP_C.\n");
 349                 goto out;
 350         }
 351         pr_debug("[server] Got CHAP_C=%s\n", challenge);
 352         challenge_len = chap_string_to_hex(challenge_binhex, challenge,
 353                                 strlen(challenge));
 354         if (!challenge_len) {
 355                 pr_err("Unable to convert incoming challenge\n");
 356                 goto out;
 357         }
 358         if (challenge_len > 1024) {
 359                 pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
 360                 goto out;
 361         }
 362         /*
 363          * During mutual authentication, the CHAP_C generated by the
 364          * initiator must not match the original CHAP_C generated by
 365          * the target.
 366          */
 367         if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
 368                 pr_err("initiator CHAP_C matches target CHAP_C, failing"
 369                        " login attempt\n");
 370                 goto out;
 371         }
 372         /*
 373          * Generate CHAP_N and CHAP_R for mutual authentication.
 374          */
 375         tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
 376         if (IS_ERR(tfm)) {
 377                 pr_err("Unable to allocate struct crypto_hash\n");
 378                 goto out;
 379         }
 380         desc.tfm = tfm;
 381         desc.flags = 0;
 382
 383         ret = crypto_hash_init(&desc);
 384         if (ret < 0) {
 385                 pr_err("crypto_hash_init() failed\n");
 386                 crypto_free_hash(tfm);
 387                 goto out;
 388         }
 389
 390         /* To handle both endiannesses */
 391         id_as_uchar = id;
 392         sg_init_one(&sg, &id_as_uchar, 1);
 393         ret = crypto_hash_update(&desc, &sg, 1);
 394         if (ret < 0) {
 395                 pr_err("crypto_hash_update() failed for id\n");
 396                 crypto_free_hash(tfm);
 397                 goto out;
 398         }
 399
 400         sg_init_one(&sg, auth->password_mutual,
 401                                 strlen(auth->password_mutual));
 402         ret = crypto_hash_update(&desc, &sg, strlen(auth->password_mutual));
 403         if (ret < 0) {
 404                 pr_err("crypto_hash_update() failed for"
 405                                 " password_mutual\n");
 406                 crypto_free_hash(tfm);
 407                 goto out;
 408         }
 409         /*
 410          * Convert received challenge to binary hex.
 411          */
 412         sg_init_one(&sg, challenge_binhex, challenge_len);
 413         ret = crypto_hash_update(&desc, &sg, challenge_len);
 414         if (ret < 0) {
 415                 pr_err("crypto_hash_update() failed for ma challenge\n");
 416                 crypto_free_hash(tfm);
 417                 goto out;
 418         }
 419
 420         ret = crypto_hash_final(&desc, digest);
 421         if (ret < 0) {
 422                 pr_err("crypto_hash_final() failed for ma digest\n");
 423                 crypto_free_hash(tfm);
 424                 goto out;
 425         }
 426         crypto_free_hash(tfm);
 427         /*
 428          * Generate CHAP_N and CHAP_R.
 429          */
 430         *nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
 431         *nr_out_len += 1;
 432         pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
 433         /*
 434          * Convert response from binary hex to ascii hext.
 435          */
 436         chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE);
 437         *nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
 438                         response);
 439         *nr_out_len += 1;
 440         pr_debug("[server] Sending CHAP_R=0x%s\n", response);
 441         auth_ret = 0;
 442 out:
 443         kfree(challenge);
 444         kfree(challenge_binhex);
 445         return auth_ret;
 446 }
 447
 448 static int chap_got_response(
 449         struct iscsi_conn *conn,
 450         struct iscsi_node_auth *auth,
 451         char *nr_in_ptr,
 452         char *nr_out_ptr,
 453         unsigned int *nr_out_len)
 454 {
 455         struct iscsi_chap *chap = conn->auth_protocol;
 456
 457         switch (chap->digest_type) {
 458         case CHAP_DIGEST_MD5:
 459                 if (chap_server_compute_md5(conn, auth, nr_in_ptr,
 460                                 nr_out_ptr, nr_out_len) < 0)
 461                         return -1;
 462                 return 0;
 463         default:
 464                 pr_err("Unknown CHAP digest type %d!\n",
 465                                 chap->digest_type);
 466                 return -1;
 467         }
 468 }
 469
 470 u32 chap_main_loop(
 471         struct iscsi_conn *conn,
 472         struct iscsi_node_auth *auth,
 473         char *in_text,
 474         char *out_text,
 475         int *in_len,
 476         int *out_len)
 477 {
 478         struct iscsi_chap *chap = conn->auth_protocol;
 479
 480         if (!chap) {
 481                 chap = chap_server_open(conn, auth, in_text, out_text, out_len);
 482                 if (!chap)
 483                         return 2;
 484                 chap->chap_state = CHAP_STAGE_SERVER_AIC;
 485                 return 0;
 486         } else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
 487                 convert_null_to_semi(in_text, *in_len);
 488                 if (chap_got_response(conn, auth, in_text, out_text,
 489                                 out_len) < 0) {
 490                         chap_close(conn);
 491                         return 2;
 492                 }
 493                 if (auth->authenticate_target)
 494                         chap->chap_state = CHAP_STAGE_SERVER_NR;
 495                 else
 496                         *out_len = 0;
 497                 chap_close(conn);
 498                 return 1;
 499         }
 500
 501         return 2;
 502 }