cipher.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  *
   6  * As far as I am concerned, the code I have written for this software
   7  * can be used freely for any purpose.  Any derived versions of this
   8  * software must be clearly marked as such, and if the derived work is
   9  * incompatible with the protocol description in the RFC file, it must be
  10  * called by a name other than "ssh" or "Secure Shell".
  11  *
  12  *
  13  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  14  * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
  15  *
  16  * Redistribution and use in source and binary forms, with or without
  17  * modification, are permitted provided that the following conditions
  18  * are met:
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  26  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  28  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  29  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  34  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  */
  36
  37 #include "includes.h"
  38 RCSID("$OpenBSD: cipher.c,v 1.73 2005/01/23 10:18:12 djm Exp $");
  39
  40 #include "xmalloc.h"
  41 #include "log.h"
  42 #include "cipher.h"
  43
  44 #include <openssl/md5.h>
  45
  46 #if OPENSSL_VERSION_NUMBER < 0x00906000L
  47 #define SSH_OLD_EVP
  48 #define EVP_CIPHER_CTX_get_app_data(e)          ((e)->app_data)
  49 #endif
  50
  51 #if OPENSSL_VERSION_NUMBER < 0x00907000L
  52 extern const EVP_CIPHER *evp_rijndael(void);
  53 extern void ssh_rijndael_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  54 #endif
  55
  56 #if !defined(EVP_CTRL_SET_ACSS_MODE)
  57 # if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
  58 extern const EVP_CIPHER *evp_acss(void);
  59 #  define EVP_acss evp_acss
  60 #  define EVP_CTRL_SET_ACSS_MODE xxx    /* used below */
  61 # else
  62 #  define EVP_acss NULL /* Don't try to support ACSS on older OpenSSL */
  63 # endif /* (OPENSSL_VERSION_NUMBER >= 0x00906000L) */
  64 #endif /* !defined(EVP_CTRL_SET_ACSS_MODE) */
  65
  66 extern const EVP_CIPHER *evp_ssh1_bf(void);
  67 extern const EVP_CIPHER *evp_ssh1_3des(void);
  68 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
  69 extern const EVP_CIPHER *evp_aes_128_ctr(void);
  70 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  71
  72 struct Cipher {
  73         char    *name;
  74         int     number;         /* for ssh1 only */
  75         u_int   block_size;
  76         u_int   key_len;
  77         const EVP_CIPHER        *(*evptype)(void);
  78 } ciphers[] = {
  79         { "none",               SSH_CIPHER_NONE, 8, 0, EVP_enc_null },
  80         { "des",                SSH_CIPHER_DES, 8, 8, EVP_des_cbc },
  81         { "3des",               SSH_CIPHER_3DES, 8, 16, evp_ssh1_3des },
  82         { "blowfish",           SSH_CIPHER_BLOWFISH, 8, 32, evp_ssh1_bf },
  83
  84         { "3des-cbc",           SSH_CIPHER_SSH2, 8, 24, EVP_des_ede3_cbc },
  85         { "blowfish-cbc",       SSH_CIPHER_SSH2, 8, 16, EVP_bf_cbc },
  86         { "cast128-cbc",        SSH_CIPHER_SSH2, 8, 16, EVP_cast5_cbc },
  87         { "arcfour",            SSH_CIPHER_SSH2, 8, 16, EVP_rc4 },
  88 #if OPENSSL_VERSION_NUMBER < 0x00907000L
  89         { "aes128-cbc",         SSH_CIPHER_SSH2, 16, 16, evp_rijndael },
  90         { "aes192-cbc",         SSH_CIPHER_SSH2, 16, 24, evp_rijndael },
  91         { "aes256-cbc",         SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
  92         { "rijndael-cbc@lysator.liu.se",
  93                                 SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
  94 #else
  95         { "aes128-cbc",         SSH_CIPHER_SSH2, 16, 16, EVP_aes_128_cbc },
  96         { "aes192-cbc",         SSH_CIPHER_SSH2, 16, 24, EVP_aes_192_cbc },
  97         { "aes256-cbc",         SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
  98         { "rijndael-cbc@lysator.liu.se",
  99                                 SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
 100 #endif
 101 #if OPENSSL_VERSION_NUMBER >= 0x00905000L
 102         { "aes128-ctr",         SSH_CIPHER_SSH2, 16, 16, evp_aes_128_ctr },
 103         { "aes192-ctr",         SSH_CIPHER_SSH2, 16, 24, evp_aes_128_ctr },
 104         { "aes256-ctr",         SSH_CIPHER_SSH2, 16, 32, evp_aes_128_ctr },
 105 #endif
 106 #if defined(EVP_CTRL_SET_ACSS_MODE)
 107         { "acss@openssh.org",   SSH_CIPHER_SSH2, 16, 5, EVP_acss },
 108 #endif
 109         { NULL,                 SSH_CIPHER_INVALID, 0, 0, NULL }
 110 };
 111
 112 /*--*/
 113
 114 u_int
 115 cipher_blocksize(const Cipher *c)
 116 {
 117         return (c->block_size);
 118 }
 119
 120 u_int
 121 cipher_keylen(const Cipher *c)
 122 {
 123         return (c->key_len);
 124 }
 125
 126 u_int
 127 cipher_get_number(const Cipher *c)
 128 {
 129         return (c->number);
 130 }
 131
 132 u_int
 133 cipher_mask_ssh1(int client)
 134 {
 135         u_int mask = 0;
 136         mask |= 1 << SSH_CIPHER_3DES;           /* Mandatory */
 137         mask |= 1 << SSH_CIPHER_BLOWFISH;
 138         if (client) {
 139                 mask |= 1 << SSH_CIPHER_DES;
 140         }
 141         return mask;
 142 }
 143
 144 Cipher *
 145 cipher_by_name(const char *name)
 146 {
 147         Cipher *c;
 148         for (c = ciphers; c->name != NULL; c++)
 149                 if (strcmp(c->name, name) == 0)
 150                         return c;
 151         return NULL;
 152 }
 153
 154 Cipher *
 155 cipher_by_number(int id)
 156 {
 157         Cipher *c;
 158         for (c = ciphers; c->name != NULL; c++)
 159                 if (c->number == id)
 160                         return c;
 161         return NULL;
 162 }
 163
 164 #define CIPHER_SEP      ","
 165 int
 166 ciphers_valid(const char *names)
 167 {
 168         Cipher *c;
 169         char *cipher_list, *cp;
 170         char *p;
 171
 172         if (names == NULL || strcmp(names, "") == 0)
 173                 return 0;
 174         cipher_list = cp = xstrdup(names);
 175         for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
 176             (p = strsep(&cp, CIPHER_SEP))) {
 177                 c = cipher_by_name(p);
 178                 if (c == NULL || c->number != SSH_CIPHER_SSH2) {
 179                         debug("bad cipher %s [%s]", p, names);
 180                         xfree(cipher_list);
 181                         return 0;
 182                 } else {
 183                         debug3("cipher ok: %s [%s]", p, names);
 184                 }
 185         }
 186         debug3("ciphers ok: [%s]", names);
 187         xfree(cipher_list);
 188         return 1;
 189 }
 190
 191 /*
 192  * Parses the name of the cipher.  Returns the number of the corresponding
 193  * cipher, or -1 on error.
 194  */
 195
 196 int
 197 cipher_number(const char *name)
 198 {
 199         Cipher *c;
 200         if (name == NULL)
 201                 return -1;
 202         for (c = ciphers; c->name != NULL; c++)
 203                 if (strcasecmp(c->name, name) == 0)
 204                         return c->number;
 205         return -1;
 206 }
 207
 208 char *
 209 cipher_name(int id)
 210 {
 211         Cipher *c = cipher_by_number(id);
 212         return (c==NULL) ? "<unknown>" : c->name;
 213 }
 214
 215 void
 216 cipher_init(CipherContext *cc, Cipher *cipher,
 217     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
 218     int do_encrypt)
 219 {
 220         static int dowarn = 1;
 221 #ifdef SSH_OLD_EVP
 222         EVP_CIPHER *type;
 223 #else
 224         const EVP_CIPHER *type;
 225 #endif
 226         int klen;
 227
 228         if (cipher->number == SSH_CIPHER_DES) {
 229                 if (dowarn) {
 230                         error("Warning: use of DES is strongly discouraged "
 231                             "due to cryptographic weaknesses");
 232                         dowarn = 0;
 233                 }
 234                 if (keylen > 8)
 235                         keylen = 8;
 236         }
 237         cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
 238
 239         if (keylen < cipher->key_len)
 240                 fatal("cipher_init: key length %d is insufficient for %s.",
 241                     keylen, cipher->name);
 242         if (iv != NULL && ivlen < cipher->block_size)
 243                 fatal("cipher_init: iv length %d is insufficient for %s.",
 244                     ivlen, cipher->name);
 245         cc->cipher = cipher;
 246
 247         type = (*cipher->evptype)();
 248
 249         EVP_CIPHER_CTX_init(&cc->evp);
 250 #ifdef SSH_OLD_EVP
 251         if (type->key_len > 0 && type->key_len != keylen) {
 252                 debug("cipher_init: set keylen (%d -> %d)",
 253                     type->key_len, keylen);
 254                 type->key_len = keylen;
 255         }
 256         EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
 257             (do_encrypt == CIPHER_ENCRYPT));
 258 #else
 259         if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
 260             (do_encrypt == CIPHER_ENCRYPT)) == 0)
 261                 fatal("cipher_init: EVP_CipherInit failed for %s",
 262                     cipher->name);
 263         klen = EVP_CIPHER_CTX_key_length(&cc->evp);
 264         if (klen > 0 && keylen != klen) {
 265                 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
 266                 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
 267                         fatal("cipher_init: set keylen failed (%d -> %d)",
 268                             klen, keylen);
 269         }
 270         if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
 271                 fatal("cipher_init: EVP_CipherInit: set key failed for %s",
 272                     cipher->name);
 273 #endif
 274 }
 275
 276 void
 277 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
 278 {
 279         if (len % cc->cipher->block_size)
 280                 fatal("cipher_encrypt: bad plaintext length %d", len);
 281 #ifdef SSH_OLD_EVP
 282         EVP_Cipher(&cc->evp, dest, (u_char *)src, len);
 283 #else
 284         if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
 285                 fatal("evp_crypt: EVP_Cipher failed");
 286 #endif
 287 }
 288
 289 void
 290 cipher_cleanup(CipherContext *cc)
 291 {
 292 #ifdef SSH_OLD_EVP
 293         EVP_CIPHER_CTX_cleanup(&cc->evp);
 294 #else
 295         if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
 296                 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
 297 #endif
 298 }
 299
 300 /*
 301  * Selects the cipher, and keys if by computing the MD5 checksum of the
 302  * passphrase and using the resulting 16 bytes as the key.
 303  */
 304
 305 void
 306 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
 307     const char *passphrase, int do_encrypt)
 308 {
 309         MD5_CTX md;
 310         u_char digest[16];
 311
 312         MD5_Init(&md);
 313         MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
 314         MD5_Final(digest, &md);
 315
 316         cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
 317
 318         memset(digest, 0, sizeof(digest));
 319         memset(&md, 0, sizeof(md));
 320 }
 321
 322 /*
 323  * Exports an IV from the CipherContext required to export the key
 324  * state back from the unprivileged child to the privileged parent
 325  * process.
 326  */
 327
 328 int
 329 cipher_get_keyiv_len(const CipherContext *cc)
 330 {
 331         Cipher *c = cc->cipher;
 332         int ivlen;
 333
 334         if (c->number == SSH_CIPHER_3DES)
 335                 ivlen = 24;
 336         else
 337                 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 338         return (ivlen);
 339 }
 340
 341 void
 342 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
 343 {
 344         Cipher *c = cc->cipher;
 345         int evplen;
 346
 347         switch (c->number) {
 348         case SSH_CIPHER_SSH2:
 349         case SSH_CIPHER_DES:
 350         case SSH_CIPHER_BLOWFISH:
 351                 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 352                 if (evplen == 0)
 353                         return;
 354                 if (evplen != len)
 355                         fatal("%s: wrong iv length %d != %d", __func__,
 356                             evplen, len);
 357 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 358                 if (c->evptype == evp_rijndael)
 359                         ssh_rijndael_iv(&cc->evp, 0, iv, len);
 360                 else
 361 #endif
 362                 if (c->evptype == evp_aes_128_ctr)
 363                         ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
 364                 else
 365                         memcpy(iv, cc->evp.iv, len);
 366                 break;
 367         case SSH_CIPHER_3DES:
 368                 ssh1_3des_iv(&cc->evp, 0, iv, 24);
 369                 break;
 370         default:
 371                 fatal("%s: bad cipher %d", __func__, c->number);
 372         }
 373 }
 374
 375 void
 376 cipher_set_keyiv(CipherContext *cc, u_char *iv)
 377 {
 378         Cipher *c = cc->cipher;
 379         int evplen = 0;
 380
 381         switch (c->number) {
 382         case SSH_CIPHER_SSH2:
 383         case SSH_CIPHER_DES:
 384         case SSH_CIPHER_BLOWFISH:
 385                 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 386                 if (evplen == 0)
 387                         return;
 388 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 389                 if (c->evptype == evp_rijndael)
 390                         ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
 391                 else
 392 #endif
 393                 if (c->evptype == evp_aes_128_ctr)
 394                         ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
 395                 else
 396                         memcpy(cc->evp.iv, iv, evplen);
 397                 break;
 398         case SSH_CIPHER_3DES:
 399                 ssh1_3des_iv(&cc->evp, 1, iv, 24);
 400                 break;
 401         default:
 402                 fatal("%s: bad cipher %d", __func__, c->number);
 403         }
 404 }
 405
 406 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 407 #define EVP_X_STATE(evp)        &(evp).c
 408 #define EVP_X_STATE_LEN(evp)    sizeof((evp).c)
 409 #else
 410 #define EVP_X_STATE(evp)        (evp).cipher_data
 411 #define EVP_X_STATE_LEN(evp)    (evp).cipher->ctx_size
 412 #endif
 413
 414 int
 415 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
 416 {
 417         Cipher *c = cc->cipher;
 418         int plen = 0;
 419
 420         if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 421                 plen = EVP_X_STATE_LEN(cc->evp);
 422                 if (dat == NULL)
 423                         return (plen);
 424                 memcpy(dat, EVP_X_STATE(cc->evp), plen);
 425         }
 426         return (plen);
 427 }
 428
 429 void
 430 cipher_set_keycontext(CipherContext *cc, u_char *dat)
 431 {
 432         Cipher *c = cc->cipher;
 433         int plen;
 434
 435         if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 436                 plen = EVP_X_STATE_LEN(cc->evp);
 437                 memcpy(EVP_X_STATE(cc->evp), dat, plen);
 438         }
 439 }