cipher-ctr.c

   1 /* $OpenBSD: cipher-ctr.c,v 1.10 2006/08/03 03:34:42 deraadt 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 #include <sys/types.h>
  20
  21 #include <string.h>
  22
  23 #include <openssl/evp.h>
  24
  25 #include "xmalloc.h"
  26 #include "log.h"
  27
  28 /* compatibility with old or broken OpenSSL versions */
  29 #include "openbsd-compat/openssl-compat.h"
  30
  31 #ifdef USE_BUILTIN_RIJNDAEL
  32 #include "rijndael.h"
  33 #define AES_KEY rijndael_ctx
  34 #define AES_BLOCK_SIZE 16
  35 #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
  36 #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
  37 #else
  38 #include <openssl/aes.h>
  39 #endif
  40
  41 const EVP_CIPHER *evp_aes_128_ctr(void);
  42 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  43
  44 struct ssh_aes_ctr_ctx
  45 {
  46         AES_KEY         aes_ctx;
  47         u_char          aes_counter[AES_BLOCK_SIZE];
  48 };
  49
  50 /*
  51  * increment counter 'ctr',
  52  * the counter is of size 'len' bytes and stored in network-byte-order.
  53  * (LSB at ctr[len-1], MSB at ctr[0])
  54  */
  55 static void
  56 ssh_ctr_inc(u_char *ctr, u_int len)
  57 {
  58         int i;
  59
  60         for (i = len - 1; i >= 0; i--)
  61                 if (++ctr[i])   /* continue on overflow */
  62                         return;
  63 }
  64
  65 static int
  66 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
  67     u_int len)
  68 {
  69         struct ssh_aes_ctr_ctx *c;
  70         u_int n = 0;
  71         u_char buf[AES_BLOCK_SIZE];
  72
  73         if (len == 0)
  74                 return (1);
  75         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
  76                 return (0);
  77
  78         while ((len--) > 0) {
  79                 if (n == 0) {
  80                         AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
  81                         ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
  82                 }
  83                 *(dest++) = *(src++) ^ buf[n];
  84                 n = (n + 1) % AES_BLOCK_SIZE;
  85         }
  86         return (1);
  87 }
  88
  89 static int
  90 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
  91     int enc)
  92 {
  93         struct ssh_aes_ctr_ctx *c;
  94
  95         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
  96                 c = xmalloc(sizeof(*c));
  97                 EVP_CIPHER_CTX_set_app_data(ctx, c);
  98         }
  99         if (key != NULL)
 100                 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
 101                     &c->aes_ctx);
 102         if (iv != NULL)
 103                 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
 104         return (1);
 105 }
 106
 107 static int
 108 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
 109 {
 110         struct ssh_aes_ctr_ctx *c;
 111
 112         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
 113                 memset(c, 0, sizeof(*c));
 114                 xfree(c);
 115                 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 116         }
 117         return (1);
 118 }
 119
 120 void
 121 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
 122 {
 123         struct ssh_aes_ctr_ctx *c;
 124
 125         if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
 126                 fatal("ssh_aes_ctr_iv: no context");
 127         if (doset)
 128                 memcpy(c->aes_counter, iv, len);
 129         else
 130                 memcpy(iv, c->aes_counter, len);
 131 }
 132
 133 const EVP_CIPHER *
 134 evp_aes_128_ctr(void)
 135 {
 136         static EVP_CIPHER aes_ctr;
 137
 138         memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
 139         aes_ctr.nid = NID_undef;
 140         aes_ctr.block_size = AES_BLOCK_SIZE;
 141         aes_ctr.iv_len = AES_BLOCK_SIZE;
 142         aes_ctr.key_len = 16;
 143         aes_ctr.init = ssh_aes_ctr_init;
 144         aes_ctr.cleanup = ssh_aes_ctr_cleanup;
 145         aes_ctr.do_cipher = ssh_aes_ctr;
 146 #ifndef SSH_OLD_EVP
 147         aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 148             EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
 149 #endif
 150         return (&aes_ctr);
 151 }