release/src/router/dropbear/common-algo.c

   1 /*
   2  * Dropbear SSH
   3  *
   4  * Copyright (c) 2002,2003 Matt Johnston
   5  * Copyright (c) 2004 by Mihnea Stoenescu
   6  * All rights reserved.
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a copy
   9  * of this software and associated documentation files (the "Software"), to deal
  10  * in the Software without restriction, including without limitation the rights
  11  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  12  * copies of the Software, and to permit persons to whom the Software is
  13  * furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included in
  16  * all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  21  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  23  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  24  * SOFTWARE. */
  25
  26 #include "includes.h"
  27 #include "algo.h"
  28 #include "session.h"
  29 #include "dbutil.h"
  30 #include "kex.h"
  31 #include "ltc_prng.h"
  32 #include "ecc.h"
  33
  34 /* This file (algo.c) organises the ciphers which can be used, and is used to
  35  * decide which ciphers/hashes/compression/signing to use during key exchange*/
  36
  37 static int void_cipher(const unsigned char* in, unsigned char* out,
  38                 unsigned long len, void* UNUSED(cipher_state)) {
  39         if (in != out) {
  40                 memmove(out, in, len);
  41         }
  42         return CRYPT_OK;
  43 }
  44
  45 static int void_start(int UNUSED(cipher), const unsigned char* UNUSED(IV),
  46                         const unsigned char* UNUSED(key),
  47                         int UNUSED(keylen), int UNUSED(num_rounds), void* UNUSED(cipher_state)) {
  48         return CRYPT_OK;
  49 }
  50
  51 /* Mappings for ciphers, parameters are
  52    {&cipher_desc, keysize, blocksize} */
  53
  54 /* Remember to add new ciphers/hashes to regciphers/reghashes too */
  55
  56 #ifdef DROPBEAR_AES256
  57 static const struct dropbear_cipher dropbear_aes256 =
  58         {&aes_desc, 32, 16};
  59 #endif
  60 #ifdef DROPBEAR_AES128
  61 static const struct dropbear_cipher dropbear_aes128 =
  62         {&aes_desc, 16, 16};
  63 #endif
  64 #ifdef DROPBEAR_BLOWFISH
  65 static const struct dropbear_cipher dropbear_blowfish =
  66         {&blowfish_desc, 16, 8};
  67 #endif
  68 #ifdef DROPBEAR_TWOFISH256
  69 static const struct dropbear_cipher dropbear_twofish256 =
  70         {&twofish_desc, 32, 16};
  71 #endif
  72 #ifdef DROPBEAR_TWOFISH128
  73 static const struct dropbear_cipher dropbear_twofish128 =
  74         {&twofish_desc, 16, 16};
  75 #endif
  76 #ifdef DROPBEAR_3DES
  77 static const struct dropbear_cipher dropbear_3des =
  78         {&des3_desc, 24, 8};
  79 #endif
  80
  81 /* used to indicate no encryption, as defined in rfc2410 */
  82 const struct dropbear_cipher dropbear_nocipher =
  83         {NULL, 16, 8};
  84
  85 /* A few void* s are required to silence warnings
  86  * about the symmetric_CBC vs symmetric_CTR cipher_state pointer */
  87 const struct dropbear_cipher_mode dropbear_mode_cbc =
  88         {(void*)cbc_start, (void*)cbc_encrypt, (void*)cbc_decrypt};
  89 const struct dropbear_cipher_mode dropbear_mode_none =
  90         {void_start, void_cipher, void_cipher};
  91 #ifdef DROPBEAR_ENABLE_CTR_MODE
  92 /* a wrapper to make ctr_start and cbc_start look the same */
  93 static int dropbear_big_endian_ctr_start(int cipher,
  94                 const unsigned char *IV,
  95                 const unsigned char *key, int keylen,
  96                 int num_rounds, symmetric_CTR *ctr) {
  97         return ctr_start(cipher, IV, key, keylen, num_rounds, CTR_COUNTER_BIG_ENDIAN, ctr);
  98 }
  99 const struct dropbear_cipher_mode dropbear_mode_ctr =
 100         {(void*)dropbear_big_endian_ctr_start, (void*)ctr_encrypt, (void*)ctr_decrypt};
 101 #endif
 102
 103 /* Mapping of ssh hashes to libtomcrypt hashes, including keysize etc.
 104    {&hash_desc, keysize, hashsize} */
 105
 106 #ifdef DROPBEAR_SHA1_HMAC
 107 static const struct dropbear_hash dropbear_sha1 =
 108         {&sha1_desc, 20, 20};
 109 #endif
 110 #ifdef DROPBEAR_SHA1_96_HMAC
 111 static const struct dropbear_hash dropbear_sha1_96 =
 112         {&sha1_desc, 20, 12};
 113 #endif
 114 #ifdef DROPBEAR_SHA2_256_HMAC
 115 static const struct dropbear_hash dropbear_sha2_256 =
 116         {&sha256_desc, 32, 32};
 117 #endif
 118 #ifdef DROPBEAR_SHA2_512_HMAC
 119 static const struct dropbear_hash dropbear_sha2_512 =
 120         {&sha512_desc, 64, 64};
 121 #endif
 122 #ifdef DROPBEAR_MD5_HMAC
 123 static const struct dropbear_hash dropbear_md5 =
 124         {&md5_desc, 16, 16};
 125 #endif
 126
 127 const struct dropbear_hash dropbear_nohash =
 128         {NULL, 16, 0}; /* used initially */
 129
 130
 131 /* The following map ssh names to internal values.
 132  * The ordering here is important for the client - the first mode
 133  * that is also supported by the server will get used. */
 134
 135 algo_type sshciphers[] = {
 136 #ifdef DROPBEAR_ENABLE_CTR_MODE
 137 #ifdef DROPBEAR_AES128
 138         {"aes128-ctr", 0, &dropbear_aes128, 1, &dropbear_mode_ctr},
 139 #endif
 140 #ifdef DROPBEAR_3DES
 141         {"3des-ctr", 0, &dropbear_3des, 1, &dropbear_mode_ctr},
 142 #endif
 143 #ifdef DROPBEAR_AES256
 144         {"aes256-ctr", 0, &dropbear_aes256, 1, &dropbear_mode_ctr},
 145 #endif
 146 #endif /* DROPBEAR_ENABLE_CTR_MODE */
 147
 148 /* CBC modes are always enabled */
 149 #ifdef DROPBEAR_AES128
 150         {"aes128-cbc", 0, &dropbear_aes128, 1, &dropbear_mode_cbc},
 151 #endif
 152 #ifdef DROPBEAR_3DES
 153         {"3des-cbc", 0, &dropbear_3des, 1, &dropbear_mode_cbc},
 154 #endif
 155 #ifdef DROPBEAR_AES256
 156         {"aes256-cbc", 0, &dropbear_aes256, 1, &dropbear_mode_cbc},
 157 #endif
 158 #ifdef DROPBEAR_TWOFISH256
 159         {"twofish256-cbc", 0, &dropbear_twofish256, 1, &dropbear_mode_cbc},
 160         {"twofish-cbc", 0, &dropbear_twofish256, 1, &dropbear_mode_cbc},
 161 #endif
 162 #ifdef DROPBEAR_TWOFISH128
 163         {"twofish128-cbc", 0, &dropbear_twofish128, 1, &dropbear_mode_cbc},
 164 #endif
 165 #ifdef DROPBEAR_BLOWFISH
 166         {"blowfish-cbc", 0, &dropbear_blowfish, 1, &dropbear_mode_cbc},
 167 #endif
 168 #ifdef DROPBEAR_NONE_CIPHER
 169         {"none", 0, (void*)&dropbear_nocipher, 1, &dropbear_mode_none},
 170 #endif
 171         {NULL, 0, NULL, 0, NULL}
 172 };
 173
 174 algo_type sshhashes[] = {
 175 #ifdef DROPBEAR_SHA2_256_HMAC
 176         {"hmac-sha2-256", 0, &dropbear_sha2_256, 1, NULL},
 177 #endif
 178 #ifdef DROPBEAR_SHA2_512_HMAC
 179         {"hmac-sha2-512", 0, &dropbear_sha2_512, 1, NULL},
 180 #endif
 181 #ifdef DROPBEAR_SHA1_96_HMAC
 182         {"hmac-sha1-96", 0, &dropbear_sha1_96, 1, NULL},
 183 #endif
 184 #ifdef DROPBEAR_SHA1_HMAC
 185         {"hmac-sha1", 0, &dropbear_sha1, 1, NULL},
 186 #endif
 187 #ifdef DROPBEAR_MD5_HMAC
 188         {"hmac-md5", 0, (void*)&dropbear_md5, 1, NULL},
 189 #endif
 190 #ifdef DROPBEAR_NONE_INTEGRITY
 191         {"none", 0, (void*)&dropbear_nohash, 1, NULL},
 192 #endif
 193         {NULL, 0, NULL, 0, NULL}
 194 };
 195
 196 #ifndef DISABLE_ZLIB
 197 algo_type ssh_compress[] = {
 198         {"zlib", DROPBEAR_COMP_ZLIB, NULL, 1, NULL},
 199         {"zlib@openssh.com", DROPBEAR_COMP_ZLIB_DELAY, NULL, 1, NULL},
 200         {"none", DROPBEAR_COMP_NONE, NULL, 1, NULL},
 201         {NULL, 0, NULL, 0, NULL}
 202 };
 203 #endif
 204
 205 algo_type ssh_nocompress[] = {
 206         {"none", DROPBEAR_COMP_NONE, NULL, 1, NULL},
 207         {NULL, 0, NULL, 0, NULL}
 208 };
 209
 210 algo_type sshhostkey[] = {
 211 #ifdef DROPBEAR_ECDSA
 212 #ifdef DROPBEAR_ECC_256
 213         {"ecdsa-sha2-nistp256", DROPBEAR_SIGNKEY_ECDSA_NISTP256, NULL, 1, NULL},
 214 #endif
 215 #ifdef DROPBEAR_ECC_384
 216         {"ecdsa-sha2-nistp384", DROPBEAR_SIGNKEY_ECDSA_NISTP384, NULL, 1, NULL},
 217 #endif
 218 #ifdef DROPBEAR_ECC_521
 219         {"ecdsa-sha2-nistp521", DROPBEAR_SIGNKEY_ECDSA_NISTP521, NULL, 1, NULL},
 220 #endif
 221 #endif
 222 #ifdef DROPBEAR_RSA
 223         {"ssh-rsa", DROPBEAR_SIGNKEY_RSA, NULL, 1, NULL},
 224 #endif
 225 #ifdef DROPBEAR_DSS
 226         {"ssh-dss", DROPBEAR_SIGNKEY_DSS, NULL, 1, NULL},
 227 #endif
 228         {NULL, 0, NULL, 0, NULL}
 229 };
 230
 231 static const struct dropbear_kex kex_dh_group1 = {DROPBEAR_KEX_NORMAL_DH, dh_p_1, DH_P_1_LEN, NULL, &sha1_desc };
 232 static const struct dropbear_kex kex_dh_group14 = {DROPBEAR_KEX_NORMAL_DH, dh_p_14, DH_P_14_LEN, NULL, &sha1_desc };
 233
 234 /* These can't be const since dropbear_ecc_fill_dp() fills out
 235  ecc_curve at runtime */
 236 #ifdef DROPBEAR_ECDH
 237 #ifdef DROPBEAR_ECC_256
 238 static struct dropbear_kex kex_ecdh_nistp256 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp256, &sha256_desc };
 239 #endif
 240 #ifdef DROPBEAR_ECC_384
 241 static struct dropbear_kex kex_ecdh_nistp384 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp384, &sha384_desc };
 242 #endif
 243 #ifdef DROPBEAR_ECC_521
 244 static struct dropbear_kex kex_ecdh_nistp521 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp521, &sha512_desc };
 245 #endif
 246 #endif /* DROPBEAR_ECDH */
 247
 248 #ifdef DROPBEAR_CURVE25519
 249 /* Referred to directly */
 250 static const struct dropbear_kex kex_curve25519 = {DROPBEAR_KEX_CURVE25519, NULL, 0, NULL, &sha256_desc };
 251 #endif
 252
 253 algo_type sshkex[] = {
 254 #ifdef DROPBEAR_CURVE25519
 255         {"curve25519-sha256@libssh.org", 0, &kex_curve25519, 1, NULL},
 256 #endif
 257 #ifdef DROPBEAR_ECDH
 258 #ifdef DROPBEAR_ECC_521
 259         {"ecdh-sha2-nistp521", 0, &kex_ecdh_nistp521, 1, NULL},
 260 #endif
 261 #ifdef DROPBEAR_ECC_384
 262         {"ecdh-sha2-nistp384", 0, &kex_ecdh_nistp384, 1, NULL},
 263 #endif
 264 #ifdef DROPBEAR_ECC_256
 265         {"ecdh-sha2-nistp256", 0, &kex_ecdh_nistp256, 1, NULL},
 266 #endif
 267 #endif
 268         {"diffie-hellman-group1-sha1", 0, &kex_dh_group1, 1, NULL},
 269         {"diffie-hellman-group14-sha1", 0, &kex_dh_group14, 1, NULL},
 270 #ifdef USE_KEXGUESS2
 271         {KEXGUESS2_ALGO_NAME, KEXGUESS2_ALGO_ID, NULL, 1, NULL},
 272 #endif
 273         {NULL, 0, NULL, 0, NULL}
 274 };
 275
 276 /* algolen specifies the length of algo, algos is our local list to match
 277  * against.
 278  * Returns DROPBEAR_SUCCESS if we have a match for algo, DROPBEAR_FAILURE
 279  * otherwise */
 280 int have_algo(char* algo, size_t algolen, algo_type algos[]) {
 281
 282         int i;
 283
 284         for (i = 0; algos[i].name != NULL; i++) {
 285                 if (strlen(algos[i].name) == algolen
 286                                 && (strncmp(algos[i].name, algo, algolen) == 0)) {
 287                         return DROPBEAR_SUCCESS;
 288                 }
 289         }
 290
 291         return DROPBEAR_FAILURE;
 292 }
 293
 294 /* Output a comma separated list of algorithms to a buffer */
 295 void buf_put_algolist(buffer * buf, algo_type localalgos[]) {
 296
 297         unsigned int i, len;
 298         unsigned int donefirst = 0;
 299         buffer *algolist = NULL;
 300
 301         algolist = buf_new(200);
 302         for (i = 0; localalgos[i].name != NULL; i++) {
 303                 if (localalgos[i].usable) {
 304                         if (donefirst)
 305                                 buf_putbyte(algolist, ',');
 306                         donefirst = 1;
 307                         len = strlen(localalgos[i].name);
 308                         buf_putbytes(algolist, localalgos[i].name, len);
 309                 }
 310         }
 311         buf_putstring(buf, algolist->data, algolist->len);
 312         buf_free(algolist);
 313 }
 314
 315 /* match the first algorithm in the comma-separated list in buf which is
 316  * also in localalgos[], or return NULL on failure.
 317  * (*goodguess) is set to 1 if the preferred client/server algos match,
 318  * 0 otherwise. This is used for checking if the kexalgo/hostkeyalgos are
 319  * guessed correctly */
 320 algo_type * buf_match_algo(buffer* buf, algo_type localalgos[],
 321                 enum kexguess2_used *kexguess2, int *goodguess)
 322 {
 323
 324         unsigned char * algolist = NULL;
 325         const unsigned char *remotenames[MAX_PROPOSED_ALGO], *localnames[MAX_PROPOSED_ALGO];
 326         unsigned int len;
 327         unsigned int remotecount, localcount, clicount, servcount, i, j;
 328         algo_type * ret = NULL;
 329         const unsigned char **clinames, **servnames;
 330
 331         if (goodguess) {
 332                 *goodguess = 0;
 333         }
 334
 335         /* get the comma-separated list from the buffer ie "algo1,algo2,algo3" */
 336         algolist = buf_getstring(buf, &len);
 337         TRACE(("buf_match_algo: %s", algolist))
 338         if (len > MAX_PROPOSED_ALGO*(MAX_NAME_LEN+1)) {
 339                 goto out;
 340         }
 341
 342         /* remotenames will contain a list of the strings parsed out */
 343         /* We will have at least one string (even if it's just "") */
 344         remotenames[0] = algolist;
 345         remotecount = 1;
 346         for (i = 0; i < len; i++) {
 347                 if (algolist[i] == '\0') {
 348                         /* someone is trying something strange */
 349                         goto out;
 350                 }
 351                 if (algolist[i] == ',') {
 352                         algolist[i] = '\0';
 353                         remotenames[remotecount] = &algolist[i+1];
 354                         remotecount++;
 355                 }
 356                 if (remotecount >= MAX_PROPOSED_ALGO) {
 357                         break;
 358                 }
 359         }
 360         if (kexguess2 && *kexguess2 == KEXGUESS2_LOOK) {
 361                 for (i = 0; i < remotecount; i++)
 362                 {
 363                         if (strcmp(remotenames[i], KEXGUESS2_ALGO_NAME) == 0) {
 364                                 *kexguess2 = KEXGUESS2_YES;
 365                                 break;
 366                         }
 367                 }
 368                 if (*kexguess2 == KEXGUESS2_LOOK) {
 369                         *kexguess2 = KEXGUESS2_NO;
 370                 }
 371         }
 372
 373         for (i = 0; localalgos[i].name != NULL; i++) {
 374                 if (localalgos[i].usable) {
 375                         localnames[i] = localalgos[i].name;
 376                 } else {
 377                         localnames[i] = NULL;
 378                 }
 379         }
 380         localcount = i;
 381
 382         if (IS_DROPBEAR_SERVER) {
 383                 clinames = remotenames;
 384                 clicount = remotecount;
 385                 servnames = localnames;
 386                 servcount = localcount;
 387         } else {
 388                 clinames = localnames;
 389                 clicount = localcount;
 390                 servnames = remotenames;
 391                 servcount = remotecount;
 392         }
 393
 394         /* iterate and find the first match */
 395         for (i = 0; i < clicount; i++) {
 396                 for (j = 0; j < servcount; j++) {
 397                         if (!(servnames[j] && clinames[i])) {
 398                                 /* unusable algos are NULL */
 399                                 continue;
 400                         }
 401                         if (strcmp(servnames[j], clinames[i]) == 0) {
 402                                 /* set if it was a good guess */
 403                                 if (goodguess && kexguess2) {
 404                                         if (*kexguess2 == KEXGUESS2_YES) {
 405                                                 if (i == 0) {
 406                                                         *goodguess = 1;
 407                                                 }
 408
 409                                         } else {
 410                                                 if (i == 0 && j == 0) {
 411                                                         *goodguess = 1;
 412                                                 }
 413                                         }
 414                                 }
 415                                 /* set the algo to return */
 416                                 if (IS_DROPBEAR_SERVER) {
 417                                         ret = &localalgos[j];
 418                                 } else {
 419                                         ret = &localalgos[i];
 420                                 }
 421                                 goto out;
 422                         }
 423                 }
 424         }
 425
 426 out:
 427         m_free(algolist);
 428         return ret;
 429 }
 430
 431 #ifdef DROPBEAR_NONE_CIPHER
 432
 433 void
 434 set_algo_usable(algo_type algos[], const char * algo_name, int usable)
 435 {
 436         algo_type *a;
 437         for (a = algos; a->name != NULL; a++)
 438         {
 439                 if (strcmp(a->name, algo_name) == 0)
 440                 {
 441                         a->usable = usable;
 442                         return;
 443                 }
 444         }
 445 }
 446
 447 int
 448 get_algo_usable(algo_type algos[], const char * algo_name)
 449 {
 450         algo_type *a;
 451         for (a = algos; a->name != NULL; a++)
 452         {
 453                 if (strcmp(a->name, algo_name) == 0)
 454                 {
 455                         return a->usable;
 456                 }
 457         }
 458         return 0;
 459 }
 460
 461 #endif /* DROPBEAR_NONE_CIPHER */
 462
 463 #ifdef ENABLE_USER_ALGO_LIST
 464
 465 char *
 466 algolist_string(algo_type algos[])
 467 {
 468         char *ret_list;
 469         buffer *b = buf_new(200);
 470         buf_put_algolist(b, algos);
 471         buf_setpos(b, b->len);
 472         buf_putbyte(b, '\0');
 473         buf_setpos(b, 4);
 474         ret_list = m_strdup(buf_getptr(b, b->len - b->pos));
 475         buf_free(b);
 476         return ret_list;
 477 }
 478
 479 static algo_type*
 480 check_algo(const char* algo_name, algo_type *algos)
 481 {
 482         algo_type *a;
 483         for (a = algos; a->name != NULL; a++)
 484         {
 485                 if (strcmp(a->name, algo_name) == 0)
 486                 {
 487                         return a;
 488                 }
 489         }
 490
 491         return NULL;
 492 }
 493
 494 static void
 495 try_add_algo(const char *algo_name, algo_type *algos,
 496                 const char *algo_desc, algo_type * new_algos, int *num_ret)
 497 {
 498         algo_type *match_algo = check_algo(algo_name, algos);
 499         if (!match_algo)
 500         {
 501                 dropbear_log(LOG_WARNING, "This Dropbear program does not support '%s' %s algorithm", algo_name, algo_desc);
 502                 return;
 503         }
 504
 505         new_algos[*num_ret] = *match_algo;
 506         (*num_ret)++;
 507 }
 508
 509 /* Checks a user provided comma-separated algorithm list for available
 510  * options. Any that are not acceptable are removed in-place. Returns the
 511  * number of valid algorithms. */
 512 int
 513 check_user_algos(const char* user_algo_list, algo_type * algos,
 514                 const char *algo_desc)
 515 {
 516         algo_type new_algos[MAX_PROPOSED_ALGO];
 517         /* this has two passes. first we sweep through the given list of
 518          * algorithms and mark them as usable=2 in the algo_type[] array... */
 519         int num_ret = 0;
 520         char *work_list = m_strdup(user_algo_list);
 521         char *last_name = work_list;
 522         char *c;
 523         for (c = work_list; *c; c++)
 524         {
 525                 if (*c == ',')
 526                 {
 527                         *c = '\0';
 528                         try_add_algo(last_name, algos, algo_desc, new_algos, &num_ret);
 529                         c++;
 530                         last_name = c;
 531                 }
 532         }
 533         try_add_algo(last_name, algos, algo_desc, new_algos, &num_ret);
 534         m_free(work_list);
 535
 536         new_algos[num_ret].name = NULL;
 537
 538         /* Copy one more as a blank delimiter */
 539         memcpy(algos, new_algos, sizeof(*new_algos) * (num_ret+1));
 540         return num_ret;
 541 }
 542 #endif /* ENABLE_USER_ALGO_LIST */