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