cipher-ctr.c

   1 /*
   2  * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16 #include "includes.h"
  17 RCSID("$OpenBSD: cipher-ctr.c,v 1.6 2005/07/17 07:17:55 djm Exp $");
  18
  19 #include <openssl/evp.h>
  20
  21 #include "log.h"
  22 #include "xmalloc.h"
  23
  24 #if OPENSSL_VERSION_NUMBER < 0x00906000L
  25 #define SSH_OLD_EVP
  26 #endif
  27
  28 #if OPENSSL_VERSION_NUMBER < 0x00907000L
  29 #include "rijndael.h"
  30 #define AES_KEY rijndael_ctx
  31 #define AES_BLOCK_SIZE 16
  32 #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
  33 #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
  34 #else
  35 #include <openssl/aes.h>
  36 #endif
  37
  38 const EVP_CIPHER *evp_aes_128_ctr(void);
  39 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  40
  41 struct ssh_aes_ctr_ctx
  42 {
  43         AES_KEY         aes_ctx;
  44         u_char          aes_counter[AES_BLOCK_SIZE];
  45 };
  46
  47 /*
  48  * increment counter 'ctr',
  49  * the counter is of size 'len' bytes and stored in network-byte-order.
  50  * (LSB at ctr[len-1], MSB at ctr[0])
  51  */
  52 static void
  53 ssh_ctr_inc(u_char *ctr, u_int len)
  54 {
  55         int i;
  56
  57         for (i = len - 1; i >= 0; i--)
  58                 if (++ctr[i])   /* continue on overflow */
  59                         return;
  60 }
  61
  62 static int
  63 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
  64     u_int len)
  65 {
  66         struct ssh_aes_ctr_ctx *c;
  67         u_int n = 0;
  68         u_char buf[AES_BLOCK_SIZE];
  69
  70         if (len == 0)
  71                 return (1);
  72         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
  73                 return (0);
  74
  75         while ((len--) > 0) {
  76                 if (n == 0) {
  77                         AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
  78                         ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
  79                 }
  80                 *(dest++) = *(src++) ^ buf[n];
  81                 n = (n + 1) % AES_BLOCK_SIZE;
  82         }
  83         return (1);
  84 }
  85
  86 static int
  87 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
  88     int enc)
  89 {
  90         struct ssh_aes_ctr_ctx *c;
  91
  92         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
  93                 c = xmalloc(sizeof(*c));
  94                 EVP_CIPHER_CTX_set_app_data(ctx, c);
  95         }
  96         if (key != NULL)
  97                 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
  98                     &c->aes_ctx);
  99         if (iv != NULL)
 100                 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
 101         return (1);
 102 }
 103
 104 static int
 105 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
 106 {
 107         struct ssh_aes_ctr_ctx *c;
 108
 109         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
 110                 memset(c, 0, sizeof(*c));
 111                 xfree(c);
 112                 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 113         }
 114         return (1);
 115 }
 116
 117 void
 118 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
 119 {
 120         struct ssh_aes_ctr_ctx *c;
 121
 122         if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
 123                 fatal("ssh_aes_ctr_iv: no context");
 124         if (doset)
 125                 memcpy(c->aes_counter, iv, len);
 126         else
 127                 memcpy(iv, c->aes_counter, len);
 128 }
 129
 130 const EVP_CIPHER *
 131 evp_aes_128_ctr(void)
 132 {
 133         static EVP_CIPHER aes_ctr;
 134
 135         memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
 136         aes_ctr.nid = NID_undef;
 137         aes_ctr.block_size = AES_BLOCK_SIZE;
 138         aes_ctr.iv_len = AES_BLOCK_SIZE;
 139         aes_ctr.key_len = 16;
 140         aes_ctr.init = ssh_aes_ctr_init;
 141         aes_ctr.cleanup = ssh_aes_ctr_cleanup;
 142         aes_ctr.do_cipher = ssh_aes_ctr;
 143 #ifndef SSH_OLD_EVP
 144         aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 145             EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
 146 #endif
 147         return (&aes_ctr);
 148 }