crypto/openssh/cipher-ctr.c

   1 /* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
   2 /*
   3  * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17 #include "includes.h"
  18
  19 #if defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR)
  20 #include <sys/types.h>
  21
  22 #include <stdarg.h>
  23 #include <string.h>
  24
  25 #include <openssl/evp.h>
  26
  27 #include "xmalloc.h"
  28 #include "log.h"
  29
  30 /* compatibility with old or broken OpenSSL versions */
  31 #include "openbsd-compat/openssl-compat.h"
  32
  33 #ifndef USE_BUILTIN_RIJNDAEL
  34 #include <openssl/aes.h>
  35 #endif
  36
  37 struct ssh_aes_ctr_ctx
  38 {
  39         AES_KEY         aes_ctx;
  40         u_char          aes_counter[AES_BLOCK_SIZE];
  41 };
  42
  43 /*
  44  * increment counter 'ctr',
  45  * the counter is of size 'len' bytes and stored in network-byte-order.
  46  * (LSB at ctr[len-1], MSB at ctr[0])
  47  */
  48 static void
  49 ssh_ctr_inc(u_char *ctr, size_t len)
  50 {
  51         int i;
  52
  53         for (i = len - 1; i >= 0; i--)
  54                 if (++ctr[i])   /* continue on overflow */
  55                         return;
  56 }
  57
  58 static int
  59 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
  60     LIBCRYPTO_EVP_INL_TYPE len)
  61 {
  62         struct ssh_aes_ctr_ctx *c;
  63         size_t n = 0;
  64         u_char buf[AES_BLOCK_SIZE];
  65
  66         if (len == 0)
  67                 return (1);
  68         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
  69                 return (0);
  70
  71         while ((len--) > 0) {
  72                 if (n == 0) {
  73                         AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
  74                         ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
  75                 }
  76                 *(dest++) = *(src++) ^ buf[n];
  77                 n = (n + 1) % AES_BLOCK_SIZE;
  78         }
  79         return (1);
  80 }
  81
  82 static int
  83 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
  84     int enc)
  85 {
  86         struct ssh_aes_ctr_ctx *c;
  87
  88         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
  89                 c = xmalloc(sizeof(*c));
  90                 EVP_CIPHER_CTX_set_app_data(ctx, c);
  91         }
  92         if (key != NULL)
  93                 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
  94                     &c->aes_ctx);
  95         if (iv != NULL)
  96                 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
  97         return (1);
  98 }
  99
 100 static int
 101 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
 102 {
 103         struct ssh_aes_ctr_ctx *c;
 104
 105         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
 106                 memset(c, 0, sizeof(*c));
 107                 free(c);
 108                 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 109         }
 110         return (1);
 111 }
 112
 113 void
 114 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, size_t len)
 115 {
 116         struct ssh_aes_ctr_ctx *c;
 117
 118         if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
 119                 fatal("ssh_aes_ctr_iv: no context");
 120         if (doset)
 121                 memcpy(c->aes_counter, iv, len);
 122         else
 123                 memcpy(iv, c->aes_counter, len);
 124 }
 125
 126 const EVP_CIPHER *
 127 evp_aes_128_ctr(void)
 128 {
 129         static EVP_CIPHER aes_ctr;
 130
 131         memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
 132         aes_ctr.nid = NID_undef;
 133         aes_ctr.block_size = AES_BLOCK_SIZE;
 134         aes_ctr.iv_len = AES_BLOCK_SIZE;
 135         aes_ctr.key_len = 16;
 136         aes_ctr.init = ssh_aes_ctr_init;
 137         aes_ctr.cleanup = ssh_aes_ctr_cleanup;
 138         aes_ctr.do_cipher = ssh_aes_ctr;
 139 #ifndef SSH_OLD_EVP
 140         aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 141             EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
 142 #endif
 143         return (&aes_ctr);
 144 }
 145
 146 #endif /* defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR) */