cipher-ctr.c

   1 /* $OpenBSD: cipher-ctr.c,v 1.8 2006/03/25 13:17:01 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 #include <openssl/evp.h>
  20
  21 #include "log.h"
  22 #include "xmalloc.h"
  23
  24 /* compatibility with old or broken OpenSSL versions */
  25 #include "openbsd-compat/openssl-compat.h"
  26
  27 #ifdef USE_BUILTIN_RIJNDAEL
  28 #include "rijndael.h"
  29 #define AES_KEY rijndael_ctx
  30 #define AES_BLOCK_SIZE 16
  31 #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
  32 #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
  33 #else
  34 #include <openssl/aes.h>
  35 #endif
  36
  37 const EVP_CIPHER *evp_aes_128_ctr(void);
  38 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  39
  40 struct ssh_aes_ctr_ctx
  41 {
  42         AES_KEY         aes_ctx;
  43         u_char          aes_counter[AES_BLOCK_SIZE];
  44 };
  45
  46 /*
  47  * increment counter 'ctr',
  48  * the counter is of size 'len' bytes and stored in network-byte-order.
  49  * (LSB at ctr[len-1], MSB at ctr[0])
  50  */
  51 static void
  52 ssh_ctr_inc(u_char *ctr, u_int len)
  53 {
  54         int i;
  55
  56         for (i = len - 1; i >= 0; i--)
  57                 if (++ctr[i])   /* continue on overflow */
  58                         return;
  59 }
  60
  61 static int
  62 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
  63     u_int len)
  64 {
  65         struct ssh_aes_ctr_ctx *c;
  66         u_int n = 0;
  67         u_char buf[AES_BLOCK_SIZE];
  68
  69         if (len == 0)
  70                 return (1);
  71         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
  72                 return (0);
  73
  74         while ((len--) > 0) {
  75                 if (n == 0) {
  76                         AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
  77                         ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
  78                 }
  79                 *(dest++) = *(src++) ^ buf[n];
  80                 n = (n + 1) % AES_BLOCK_SIZE;
  81         }
  82         return (1);
  83 }
  84
  85 static int
  86 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
  87     int enc)
  88 {
  89         struct ssh_aes_ctr_ctx *c;
  90
  91         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
  92                 c = xmalloc(sizeof(*c));
  93                 EVP_CIPHER_CTX_set_app_data(ctx, c);
  94         }
  95         if (key != NULL)
  96                 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
  97                     &c->aes_ctx);
  98         if (iv != NULL)
  99                 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
 100         return (1);
 101 }
 102
 103 static int
 104 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
 105 {
 106         struct ssh_aes_ctr_ctx *c;
 107
 108         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
 109                 memset(c, 0, sizeof(*c));
 110                 xfree(c);
 111                 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 112         }
 113         return (1);
 114 }
 115
 116 void
 117 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
 118 {
 119         struct ssh_aes_ctr_ctx *c;
 120
 121         if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
 122                 fatal("ssh_aes_ctr_iv: no context");
 123         if (doset)
 124                 memcpy(c->aes_counter, iv, len);
 125         else
 126                 memcpy(iv, c->aes_counter, len);
 127 }
 128
 129 const EVP_CIPHER *
 130 evp_aes_128_ctr(void)
 131 {
 132         static EVP_CIPHER aes_ctr;
 133
 134         memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
 135         aes_ctr.nid = NID_undef;
 136         aes_ctr.block_size = AES_BLOCK_SIZE;
 137         aes_ctr.iv_len = AES_BLOCK_SIZE;
 138         aes_ctr.key_len = 16;
 139         aes_ctr.init = ssh_aes_ctr_init;
 140         aes_ctr.cleanup = ssh_aes_ctr_cleanup;
 141         aes_ctr.do_cipher = ssh_aes_ctr;
 142 #ifndef SSH_OLD_EVP
 143         aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 144             EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
 145 #endif
 146         return (&aes_ctr);
 147 }