crypto/openssh-5/cipher.c

   1 /* $OpenBSD: cipher.c,v 1.81 2006/08/03 03:34:42 deraadt 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 <openssl/md5.h>
  43
  44 #include <string.h>
  45 #include <stdarg.h>
  46
  47 #include "xmalloc.h"
  48 #include "log.h"
  49 #include "cipher.h"
  50
  51 /* compatibility with old or broken OpenSSL versions */
  52 #include "openbsd-compat/openssl-compat.h"
  53
  54 extern const EVP_CIPHER *evp_ssh1_bf(void);
  55 extern const EVP_CIPHER *evp_ssh1_3des(void);
  56 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
  57 extern const EVP_CIPHER *evp_aes_128_ctr(void);
  58 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  59
  60 struct Cipher {
  61         char    *name;
  62         int     number;         /* for ssh1 only */
  63         u_int   block_size;
  64         u_int   key_len;
  65         u_int   discard_len;
  66         const EVP_CIPHER        *(*evptype)(void);
  67 } ciphers[] = {
  68         { "none",               SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null },
  69         { "des",                SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc },
  70         { "3des",               SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des },
  71         { "blowfish",           SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf },
  72
  73         { "3des-cbc",           SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc },
  74         { "blowfish-cbc",       SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc },
  75         { "cast128-cbc",        SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc },
  76         { "arcfour",            SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 },
  77         { "arcfour128",         SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 },
  78         { "arcfour256",         SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 },
  79         { "aes128-cbc",         SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc },
  80         { "aes192-cbc",         SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc },
  81         { "aes256-cbc",         SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
  82         { "rijndael-cbc@lysator.liu.se",
  83                                 SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
  84         { "aes128-ctr",         SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_128_ctr },
  85         { "aes192-ctr",         SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_128_ctr },
  86         { "aes256-ctr",         SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_128_ctr },
  87 #ifdef USE_CIPHER_ACSS
  88         { "acss@openssh.org",   SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss },
  89 #endif
  90         { NULL,                 SSH_CIPHER_INVALID, 0, 0, 0, NULL }
  91 };
  92
  93 /*--*/
  94
  95 u_int
  96 cipher_blocksize(const Cipher *c)
  97 {
  98         return (c->block_size);
  99 }
 100
 101 u_int
 102 cipher_keylen(const Cipher *c)
 103 {
 104         return (c->key_len);
 105 }
 106
 107 u_int
 108 cipher_get_number(const Cipher *c)
 109 {
 110         return (c->number);
 111 }
 112
 113 u_int
 114 cipher_mask_ssh1(int client)
 115 {
 116         u_int mask = 0;
 117         mask |= 1 << SSH_CIPHER_3DES;           /* Mandatory */
 118         mask |= 1 << SSH_CIPHER_BLOWFISH;
 119         if (client) {
 120                 mask |= 1 << SSH_CIPHER_DES;
 121         }
 122         return mask;
 123 }
 124
 125 Cipher *
 126 cipher_by_name(const char *name)
 127 {
 128         Cipher *c;
 129         for (c = ciphers; c->name != NULL; c++)
 130                 if (strcmp(c->name, name) == 0)
 131                         return c;
 132         return NULL;
 133 }
 134
 135 Cipher *
 136 cipher_by_number(int id)
 137 {
 138         Cipher *c;
 139         for (c = ciphers; c->name != NULL; c++)
 140                 if (c->number == id)
 141                         return c;
 142         return NULL;
 143 }
 144
 145 #define CIPHER_SEP      ","
 146 int
 147 ciphers_valid(const char *names)
 148 {
 149         Cipher *c;
 150         char *cipher_list, *cp;
 151         char *p;
 152
 153         if (names == NULL || strcmp(names, "") == 0)
 154                 return 0;
 155         cipher_list = cp = xstrdup(names);
 156         for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
 157             (p = strsep(&cp, CIPHER_SEP))) {
 158                 c = cipher_by_name(p);
 159                 if (c == NULL || c->number != SSH_CIPHER_SSH2) {
 160                         debug("bad cipher %s [%s]", p, names);
 161                         xfree(cipher_list);
 162                         return 0;
 163                 } else {
 164                         debug3("cipher ok: %s [%s]", p, names);
 165                 }
 166         }
 167         debug3("ciphers ok: [%s]", names);
 168         xfree(cipher_list);
 169         return 1;
 170 }
 171
 172 /*
 173  * Parses the name of the cipher.  Returns the number of the corresponding
 174  * cipher, or -1 on error.
 175  */
 176
 177 int
 178 cipher_number(const char *name)
 179 {
 180         Cipher *c;
 181         if (name == NULL)
 182                 return -1;
 183         for (c = ciphers; c->name != NULL; c++)
 184                 if (strcasecmp(c->name, name) == 0)
 185                         return c->number;
 186         return -1;
 187 }
 188
 189 char *
 190 cipher_name(int id)
 191 {
 192         Cipher *c = cipher_by_number(id);
 193         return (c==NULL) ? "<unknown>" : c->name;
 194 }
 195
 196 void
 197 cipher_init(CipherContext *cc, Cipher *cipher,
 198     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
 199     int do_encrypt)
 200 {
 201         static int dowarn = 1;
 202 #ifdef SSH_OLD_EVP
 203         EVP_CIPHER *type;
 204 #else
 205         const EVP_CIPHER *type;
 206         int klen;
 207 #endif
 208         u_char *junk, *discard;
 209
 210         if (cipher->number == SSH_CIPHER_DES) {
 211                 if (dowarn) {
 212                         error("Warning: use of DES is strongly discouraged "
 213                             "due to cryptographic weaknesses");
 214                         dowarn = 0;
 215                 }
 216                 if (keylen > 8)
 217                         keylen = 8;
 218         }
 219         cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
 220
 221         if (keylen < cipher->key_len)
 222                 fatal("cipher_init: key length %d is insufficient for %s.",
 223                     keylen, cipher->name);
 224         if (iv != NULL && ivlen < cipher->block_size)
 225                 fatal("cipher_init: iv length %d is insufficient for %s.",
 226                     ivlen, cipher->name);
 227         cc->cipher = cipher;
 228
 229         type = (*cipher->evptype)();
 230
 231         EVP_CIPHER_CTX_init(&cc->evp);
 232 #ifdef SSH_OLD_EVP
 233         if (type->key_len > 0 && type->key_len != keylen) {
 234                 debug("cipher_init: set keylen (%d -> %d)",
 235                     type->key_len, keylen);
 236                 type->key_len = keylen;
 237         }
 238         EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
 239             (do_encrypt == CIPHER_ENCRYPT));
 240 #else
 241         if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
 242             (do_encrypt == CIPHER_ENCRYPT)) == 0)
 243                 fatal("cipher_init: EVP_CipherInit failed for %s",
 244                     cipher->name);
 245         klen = EVP_CIPHER_CTX_key_length(&cc->evp);
 246         if (klen > 0 && keylen != (u_int)klen) {
 247                 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
 248                 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
 249                         fatal("cipher_init: set keylen failed (%d -> %d)",
 250                             klen, keylen);
 251         }
 252         if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
 253                 fatal("cipher_init: EVP_CipherInit: set key failed for %s",
 254                     cipher->name);
 255 #endif
 256
 257         if (cipher->discard_len > 0) {
 258                 junk = xmalloc(cipher->discard_len);
 259                 discard = xmalloc(cipher->discard_len);
 260                 if (EVP_Cipher(&cc->evp, discard, junk,
 261                     cipher->discard_len) == 0)
 262                         fatal("evp_crypt: EVP_Cipher failed during discard");
 263                 memset(discard, 0, cipher->discard_len);
 264                 xfree(junk);
 265                 xfree(discard);
 266         }
 267 }
 268
 269 void
 270 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
 271 {
 272         if (len % cc->cipher->block_size)
 273                 fatal("cipher_encrypt: bad plaintext length %d", len);
 274         if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
 275                 fatal("evp_crypt: EVP_Cipher failed");
 276 }
 277
 278 void
 279 cipher_cleanup(CipherContext *cc)
 280 {
 281         if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
 282                 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
 283 }
 284
 285 /*
 286  * Selects the cipher, and keys if by computing the MD5 checksum of the
 287  * passphrase and using the resulting 16 bytes as the key.
 288  */
 289
 290 void
 291 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
 292     const char *passphrase, int do_encrypt)
 293 {
 294         MD5_CTX md;
 295         u_char digest[16];
 296
 297         MD5_Init(&md);
 298         MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
 299         MD5_Final(digest, &md);
 300
 301         cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
 302
 303         memset(digest, 0, sizeof(digest));
 304         memset(&md, 0, sizeof(md));
 305 }
 306
 307 /*
 308  * Exports an IV from the CipherContext required to export the key
 309  * state back from the unprivileged child to the privileged parent
 310  * process.
 311  */
 312
 313 int
 314 cipher_get_keyiv_len(const CipherContext *cc)
 315 {
 316         Cipher *c = cc->cipher;
 317         int ivlen;
 318
 319         if (c->number == SSH_CIPHER_3DES)
 320                 ivlen = 24;
 321         else
 322                 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 323         return (ivlen);
 324 }
 325
 326 void
 327 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
 328 {
 329         Cipher *c = cc->cipher;
 330         int evplen;
 331
 332         switch (c->number) {
 333         case SSH_CIPHER_SSH2:
 334         case SSH_CIPHER_DES:
 335         case SSH_CIPHER_BLOWFISH:
 336                 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 337                 if (evplen <= 0)
 338                         return;
 339                 if ((u_int)evplen != len)
 340                         fatal("%s: wrong iv length %d != %d", __func__,
 341                             evplen, len);
 342 #ifdef USE_BUILTIN_RIJNDAEL
 343                 if (c->evptype == evp_rijndael)
 344                         ssh_rijndael_iv(&cc->evp, 0, iv, len);
 345                 else
 346 #endif
 347                 if (c->evptype == evp_aes_128_ctr)
 348                         ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
 349                 else
 350                         memcpy(iv, cc->evp.iv, len);
 351                 break;
 352         case SSH_CIPHER_3DES:
 353                 ssh1_3des_iv(&cc->evp, 0, iv, 24);
 354                 break;
 355         default:
 356                 fatal("%s: bad cipher %d", __func__, c->number);
 357         }
 358 }
 359
 360 void
 361 cipher_set_keyiv(CipherContext *cc, u_char *iv)
 362 {
 363         Cipher *c = cc->cipher;
 364         int evplen = 0;
 365
 366         switch (c->number) {
 367         case SSH_CIPHER_SSH2:
 368         case SSH_CIPHER_DES:
 369         case SSH_CIPHER_BLOWFISH:
 370                 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 371                 if (evplen == 0)
 372                         return;
 373 #ifdef USE_BUILTIN_RIJNDAEL
 374                 if (c->evptype == evp_rijndael)
 375                         ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
 376                 else
 377 #endif
 378                 if (c->evptype == evp_aes_128_ctr)
 379                         ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
 380                 else
 381                         memcpy(cc->evp.iv, iv, evplen);
 382                 break;
 383         case SSH_CIPHER_3DES:
 384                 ssh1_3des_iv(&cc->evp, 1, iv, 24);
 385                 break;
 386         default:
 387                 fatal("%s: bad cipher %d", __func__, c->number);
 388         }
 389 }
 390
 391 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 392 #define EVP_X_STATE(evp)        &(evp).c
 393 #define EVP_X_STATE_LEN(evp)    sizeof((evp).c)
 394 #else
 395 #define EVP_X_STATE(evp)        (evp).cipher_data
 396 #define EVP_X_STATE_LEN(evp)    (evp).cipher->ctx_size
 397 #endif
 398
 399 int
 400 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
 401 {
 402         Cipher *c = cc->cipher;
 403         int plen = 0;
 404
 405         if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 406                 plen = EVP_X_STATE_LEN(cc->evp);
 407                 if (dat == NULL)
 408                         return (plen);
 409                 memcpy(dat, EVP_X_STATE(cc->evp), plen);
 410         }
 411         return (plen);
 412 }
 413
 414 void
 415 cipher_set_keycontext(CipherContext *cc, u_char *dat)
 416 {
 417         Cipher *c = cc->cipher;
 418         int plen;
 419
 420         if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 421                 plen = EVP_X_STATE_LEN(cc->evp);
 422                 memcpy(EVP_X_STATE(cc->evp), dat, plen);
 423         }
 424 }