crypto/openssh/cipher.c

   1 /* $OpenBSD: cipher.c,v 1.107 2017/05/07 23:12:57 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  *
   7  * As far as I am concerned, the code I have written for this software
   8  * can be used freely for any purpose.  Any derived versions of this
   9  * software must be clearly marked as such, and if the derived work is
  10  * incompatible with the protocol description in the RFC file, it must be
  11  * called by a name other than "ssh" or "Secure Shell".
  12  *
  13  *
  14  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  15  * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41
  42 #include <string.h>
  43 #include <stdarg.h>
  44 #include <stdio.h>
  45
  46 #include "cipher.h"
  47 #include "misc.h"
  48 #include "sshbuf.h"
  49 #include "ssherr.h"
  50 #include "digest.h"
  51
  52 #include "openbsd-compat/openssl-compat.h"
  53
  54
  55 struct sshcipher_ctx {
  56         int     plaintext;
  57         int     encrypt;
  58         EVP_CIPHER_CTX *evp;
  59         struct chachapoly_ctx cp_ctx; /* XXX union with evp? */
  60         struct aesctr_ctx ac_ctx; /* XXX union with evp? */
  61         const struct sshcipher *cipher;
  62 };
  63
  64 struct sshcipher {
  65         char    *name;
  66         u_int   block_size;
  67         u_int   key_len;
  68         u_int   iv_len;         /* defaults to block_size */
  69         u_int   auth_len;
  70         u_int   flags;
  71 #define CFLAG_CBC               (1<<0)
  72 #define CFLAG_CHACHAPOLY        (1<<1)
  73 #define CFLAG_AESCTR            (1<<2)
  74 #define CFLAG_NONE              (1<<3)
  75 #define CFLAG_INTERNAL          CFLAG_NONE /* Don't use "none" for packets */
  76 #ifdef WITH_OPENSSL
  77         const EVP_CIPHER        *(*evptype)(void);
  78 #else
  79         void    *ignored;
  80 #endif
  81 };
  82
  83 static const struct sshcipher ciphers[] = {
  84 #ifdef WITH_OPENSSL
  85         { "3des-cbc",           8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
  86         { "aes128-cbc",         16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
  87         { "aes192-cbc",         16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
  88         { "aes256-cbc",         16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
  89         { "rijndael-cbc@lysator.liu.se",
  90                                 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
  91         { "aes128-ctr",         16, 16, 0, 0, 0, EVP_aes_128_ctr },
  92         { "aes192-ctr",         16, 24, 0, 0, 0, EVP_aes_192_ctr },
  93         { "aes256-ctr",         16, 32, 0, 0, 0, EVP_aes_256_ctr },
  94 # ifdef OPENSSL_HAVE_EVPGCM
  95         { "aes128-gcm@openssh.com",
  96                                 16, 16, 12, 16, 0, EVP_aes_128_gcm },
  97         { "aes256-gcm@openssh.com",
  98                                 16, 32, 12, 16, 0, EVP_aes_256_gcm },
  99 # endif /* OPENSSL_HAVE_EVPGCM */
 100 #else
 101         { "aes128-ctr",         16, 16, 0, 0, CFLAG_AESCTR, NULL },
 102         { "aes192-ctr",         16, 24, 0, 0, CFLAG_AESCTR, NULL },
 103         { "aes256-ctr",         16, 32, 0, 0, CFLAG_AESCTR, NULL },
 104 #endif
 105         { "chacha20-poly1305@openssh.com",
 106                                 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
 107         { "none",               8, 0, 0, 0, CFLAG_NONE, NULL },
 108
 109         { NULL,                 0, 0, 0, 0, 0, NULL }
 110 };
 111
 112 /*--*/
 113
 114 /* Returns a comma-separated list of supported ciphers. */
 115 char *
 116 cipher_alg_list(char sep, int auth_only)
 117 {
 118         char *tmp, *ret = NULL;
 119         size_t nlen, rlen = 0;
 120         const struct sshcipher *c;
 121
 122         for (c = ciphers; c->name != NULL; c++) {
 123                 if ((c->flags & CFLAG_INTERNAL) != 0)
 124                         continue;
 125                 if (auth_only && c->auth_len == 0)
 126                         continue;
 127                 if (ret != NULL)
 128                         ret[rlen++] = sep;
 129                 nlen = strlen(c->name);
 130                 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
 131                         free(ret);
 132                         return NULL;
 133                 }
 134                 ret = tmp;
 135                 memcpy(ret + rlen, c->name, nlen + 1);
 136                 rlen += nlen;
 137         }
 138         return ret;
 139 }
 140
 141 u_int
 142 cipher_blocksize(const struct sshcipher *c)
 143 {
 144         return (c->block_size);
 145 }
 146
 147 u_int
 148 cipher_keylen(const struct sshcipher *c)
 149 {
 150         return (c->key_len);
 151 }
 152
 153 u_int
 154 cipher_seclen(const struct sshcipher *c)
 155 {
 156         if (strcmp("3des-cbc", c->name) == 0)
 157                 return 14;
 158         return cipher_keylen(c);
 159 }
 160
 161 u_int
 162 cipher_authlen(const struct sshcipher *c)
 163 {
 164         return (c->auth_len);
 165 }
 166
 167 u_int
 168 cipher_ivlen(const struct sshcipher *c)
 169 {
 170         /*
 171          * Default is cipher block size, except for chacha20+poly1305 that
 172          * needs no IV. XXX make iv_len == -1 default?
 173          */
 174         return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
 175             c->iv_len : c->block_size;
 176 }
 177
 178 u_int
 179 cipher_is_cbc(const struct sshcipher *c)
 180 {
 181         return (c->flags & CFLAG_CBC) != 0;
 182 }
 183
 184 u_int
 185 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
 186 {
 187         return cc->plaintext;
 188 }
 189
 190 const struct sshcipher *
 191 cipher_by_name(const char *name)
 192 {
 193         const struct sshcipher *c;
 194         for (c = ciphers; c->name != NULL; c++)
 195                 if (strcmp(c->name, name) == 0)
 196                         return c;
 197         return NULL;
 198 }
 199
 200 #define CIPHER_SEP      ","
 201 int
 202 ciphers_valid(const char *names)
 203 {
 204         const struct sshcipher *c;
 205         char *cipher_list, *cp;
 206         char *p;
 207
 208         if (names == NULL || strcmp(names, "") == 0)
 209                 return 0;
 210         if ((cipher_list = cp = strdup(names)) == NULL)
 211                 return 0;
 212         for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
 213             (p = strsep(&cp, CIPHER_SEP))) {
 214                 c = cipher_by_name(p);
 215                 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
 216                         free(cipher_list);
 217                         return 0;
 218                 }
 219         }
 220         free(cipher_list);
 221         return 1;
 222 }
 223
 224 const char *
 225 cipher_warning_message(const struct sshcipher_ctx *cc)
 226 {
 227         if (cc == NULL || cc->cipher == NULL)
 228                 return NULL;
 229         /* XXX repurpose for CBC warning */
 230         return NULL;
 231 }
 232
 233 int
 234 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
 235     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
 236     int do_encrypt)
 237 {
 238         struct sshcipher_ctx *cc = NULL;
 239         int ret = SSH_ERR_INTERNAL_ERROR;
 240 #ifdef WITH_OPENSSL
 241         const EVP_CIPHER *type;
 242         int klen;
 243 #endif
 244
 245         *ccp = NULL;
 246         if ((cc = calloc(sizeof(*cc), 1)) == NULL)
 247                 return SSH_ERR_ALLOC_FAIL;
 248
 249         cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
 250         cc->encrypt = do_encrypt;
 251
 252         if (keylen < cipher->key_len ||
 253             (iv != NULL && ivlen < cipher_ivlen(cipher))) {
 254                 ret = SSH_ERR_INVALID_ARGUMENT;
 255                 goto out;
 256         }
 257
 258         cc->cipher = cipher;
 259         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
 260                 ret = chachapoly_init(&cc->cp_ctx, key, keylen);
 261                 goto out;
 262         }
 263         if ((cc->cipher->flags & CFLAG_NONE) != 0) {
 264                 ret = 0;
 265                 goto out;
 266         }
 267 #ifndef WITH_OPENSSL
 268         if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
 269                 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
 270                 aesctr_ivsetup(&cc->ac_ctx, iv);
 271                 ret = 0;
 272                 goto out;
 273         }
 274         ret = SSH_ERR_INVALID_ARGUMENT;
 275         goto out;
 276 #else /* WITH_OPENSSL */
 277         type = (*cipher->evptype)();
 278         if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
 279                 ret = SSH_ERR_ALLOC_FAIL;
 280                 goto out;
 281         }
 282         if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv,
 283             (do_encrypt == CIPHER_ENCRYPT)) == 0) {
 284                 ret = SSH_ERR_LIBCRYPTO_ERROR;
 285                 goto out;
 286         }
 287         if (cipher_authlen(cipher) &&
 288             !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
 289             -1, (u_char *)iv)) {
 290                 ret = SSH_ERR_LIBCRYPTO_ERROR;
 291                 goto out;
 292         }
 293         klen = EVP_CIPHER_CTX_key_length(cc->evp);
 294         if (klen > 0 && keylen != (u_int)klen) {
 295                 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
 296                         ret = SSH_ERR_LIBCRYPTO_ERROR;
 297                         goto out;
 298                 }
 299         }
 300         if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) {
 301                 ret = SSH_ERR_LIBCRYPTO_ERROR;
 302                 goto out;
 303         }
 304         ret = 0;
 305 #endif /* WITH_OPENSSL */
 306  out:
 307         if (ret == 0) {
 308                 /* success */
 309                 *ccp = cc;
 310         } else {
 311                 if (cc != NULL) {
 312 #ifdef WITH_OPENSSL
 313                         if (cc->evp != NULL)
 314                                 EVP_CIPHER_CTX_free(cc->evp);
 315 #endif /* WITH_OPENSSL */
 316                         explicit_bzero(cc, sizeof(*cc));
 317                         free(cc);
 318                 }
 319         }
 320         return ret;
 321 }
 322
 323 /*
 324  * cipher_crypt() operates as following:
 325  * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
 326  * Theses bytes are treated as additional authenticated data for
 327  * authenticated encryption modes.
 328  * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
 329  * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
 330  * This tag is written on encryption and verified on decryption.
 331  * Both 'aadlen' and 'authlen' can be set to 0.
 332  */
 333 int
 334 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
 335    const u_char *src, u_int len, u_int aadlen, u_int authlen)
 336 {
 337         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
 338                 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src,
 339                     len, aadlen, authlen, cc->encrypt);
 340         }
 341         if ((cc->cipher->flags & CFLAG_NONE) != 0) {
 342                 memcpy(dest, src, aadlen + len);
 343                 return 0;
 344         }
 345 #ifndef WITH_OPENSSL
 346         if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
 347                 if (aadlen)
 348                         memcpy(dest, src, aadlen);
 349                 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
 350                     dest + aadlen, len);
 351                 return 0;
 352         }
 353         return SSH_ERR_INVALID_ARGUMENT;
 354 #else
 355         if (authlen) {
 356                 u_char lastiv[1];
 357
 358                 if (authlen != cipher_authlen(cc->cipher))
 359                         return SSH_ERR_INVALID_ARGUMENT;
 360                 /* increment IV */
 361                 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
 362                     1, lastiv))
 363                         return SSH_ERR_LIBCRYPTO_ERROR;
 364                 /* set tag on decyption */
 365                 if (!cc->encrypt &&
 366                     !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
 367                     authlen, (u_char *)src + aadlen + len))
 368                         return SSH_ERR_LIBCRYPTO_ERROR;
 369         }
 370         if (aadlen) {
 371                 if (authlen &&
 372                     EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0)
 373                         return SSH_ERR_LIBCRYPTO_ERROR;
 374                 memcpy(dest, src, aadlen);
 375         }
 376         if (len % cc->cipher->block_size)
 377                 return SSH_ERR_INVALID_ARGUMENT;
 378         if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
 379             len) < 0)
 380                 return SSH_ERR_LIBCRYPTO_ERROR;
 381         if (authlen) {
 382                 /* compute tag (on encrypt) or verify tag (on decrypt) */
 383                 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
 384                         return cc->encrypt ?
 385                             SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
 386                 if (cc->encrypt &&
 387                     !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
 388                     authlen, dest + aadlen + len))
 389                         return SSH_ERR_LIBCRYPTO_ERROR;
 390         }
 391         return 0;
 392 #endif
 393 }
 394
 395 /* Extract the packet length, including any decryption necessary beforehand */
 396 int
 397 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
 398     const u_char *cp, u_int len)
 399 {
 400         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
 401                 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
 402                     cp, len);
 403         if (len < 4)
 404                 return SSH_ERR_MESSAGE_INCOMPLETE;
 405         *plenp = get_u32(cp);
 406         return 0;
 407 }
 408
 409 void
 410 cipher_free(struct sshcipher_ctx *cc)
 411 {
 412         if (cc == NULL)
 413                 return;
 414         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
 415                 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
 416         else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
 417                 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
 418 #ifdef WITH_OPENSSL
 419         if (cc->evp != NULL) {
 420                 EVP_CIPHER_CTX_free(cc->evp);
 421                 cc->evp = NULL;
 422         }
 423 #endif
 424         explicit_bzero(cc, sizeof(*cc));
 425         free(cc);
 426 }
 427
 428 /*
 429  * Exports an IV from the sshcipher_ctx required to export the key
 430  * state back from the unprivileged child to the privileged parent
 431  * process.
 432  */
 433 int
 434 cipher_get_keyiv_len(const struct sshcipher_ctx *cc)
 435 {
 436         const struct sshcipher *c = cc->cipher;
 437
 438         if ((c->flags & CFLAG_CHACHAPOLY) != 0)
 439                 return 0;
 440         else if ((c->flags & CFLAG_AESCTR) != 0)
 441                 return sizeof(cc->ac_ctx.ctr);
 442 #ifdef WITH_OPENSSL
 443         return EVP_CIPHER_CTX_iv_length(cc->evp);
 444 #else
 445         return 0;
 446 #endif
 447 }
 448
 449 int
 450 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, u_int len)
 451 {
 452         const struct sshcipher *c = cc->cipher;
 453 #ifdef WITH_OPENSSL
 454         int evplen;
 455 #endif
 456
 457         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
 458                 if (len != 0)
 459                         return SSH_ERR_INVALID_ARGUMENT;
 460                 return 0;
 461         }
 462         if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
 463                 if (len != sizeof(cc->ac_ctx.ctr))
 464                         return SSH_ERR_INVALID_ARGUMENT;
 465                 memcpy(iv, cc->ac_ctx.ctr, len);
 466                 return 0;
 467         }
 468         if ((cc->cipher->flags & CFLAG_NONE) != 0)
 469                 return 0;
 470
 471 #ifdef WITH_OPENSSL
 472         evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
 473         if (evplen == 0)
 474                 return 0;
 475         else if (evplen < 0)
 476                 return SSH_ERR_LIBCRYPTO_ERROR;
 477         if ((u_int)evplen != len)
 478                 return SSH_ERR_INVALID_ARGUMENT;
 479 #ifndef OPENSSL_HAVE_EVPCTR
 480         if (c->evptype == evp_aes_128_ctr)
 481                 ssh_aes_ctr_iv(cc->evp, 0, iv, len);
 482         else
 483 #endif
 484         if (cipher_authlen(c)) {
 485                 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
 486                    len, iv))
 487                        return SSH_ERR_LIBCRYPTO_ERROR;
 488         } else
 489                 memcpy(iv, cc->evp->iv, len);
 490 #endif
 491         return 0;
 492 }
 493
 494 int
 495 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv)
 496 {
 497         const struct sshcipher *c = cc->cipher;
 498 #ifdef WITH_OPENSSL
 499         int evplen = 0;
 500 #endif
 501
 502         if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
 503                 return 0;
 504         if ((cc->cipher->flags & CFLAG_NONE) != 0)
 505                 return 0;
 506
 507 #ifdef WITH_OPENSSL
 508         evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
 509         if (evplen <= 0)
 510                 return SSH_ERR_LIBCRYPTO_ERROR;
 511 #ifndef OPENSSL_HAVE_EVPCTR
 512         /* XXX iv arg is const, but ssh_aes_ctr_iv isn't */
 513         if (c->evptype == evp_aes_128_ctr)
 514                 ssh_aes_ctr_iv(cc->evp, 1, (u_char *)iv, evplen);
 515         else
 516 #endif
 517         if (cipher_authlen(c)) {
 518                 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
 519                 if (!EVP_CIPHER_CTX_ctrl(cc->evp,
 520                     EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv))
 521                         return SSH_ERR_LIBCRYPTO_ERROR;
 522         } else
 523                 memcpy(cc->evp->iv, iv, evplen);
 524 #endif
 525         return 0;
 526 }
 527
 528 #ifdef WITH_OPENSSL
 529 #define EVP_X_STATE(evp)        (evp)->cipher_data
 530 #define EVP_X_STATE_LEN(evp)    (evp)->cipher->ctx_size
 531 #endif
 532
 533 int
 534 cipher_get_keycontext(const struct sshcipher_ctx *cc, u_char *dat)
 535 {
 536 #if defined(WITH_OPENSSL) && !defined(OPENSSL_NO_RC4)
 537         const struct sshcipher *c = cc->cipher;
 538         int plen = 0;
 539
 540         if (c->evptype == EVP_rc4) {
 541                 plen = EVP_X_STATE_LEN(cc->evp);
 542                 if (dat == NULL)
 543                         return (plen);
 544                 memcpy(dat, EVP_X_STATE(cc->evp), plen);
 545         }
 546         return (plen);
 547 #else
 548         return 0;
 549 #endif
 550 }
 551
 552 void
 553 cipher_set_keycontext(struct sshcipher_ctx *cc, const u_char *dat)
 554 {
 555 #if defined(WITH_OPENSSL) && !defined(OPENSSL_NO_RC4)
 556         const struct sshcipher *c = cc->cipher;
 557         int plen;
 558
 559         if (c->evptype == EVP_rc4) {
 560                 plen = EVP_X_STATE_LEN(cc->evp);
 561                 memcpy(EVP_X_STATE(cc->evp), dat, plen);
 562         }
 563 #endif
 564 }