crypto/openssh-4/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 <stdarg.h>
  22 #include <string.h>
  23
  24 #include <openssl/evp.h>
  25
  26 #include "xmalloc.h"
  27 #include "log.h"
  28
  29 /* compatibility with old or broken OpenSSL versions */
  30 #include "openbsd-compat/openssl-compat.h"
  31
  32 #ifdef USE_BUILTIN_RIJNDAEL
  33 #include "rijndael.h"
  34 #define AES_KEY rijndael_ctx
  35 #define AES_BLOCK_SIZE 16
  36 #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
  37 #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
  38 #else
  39 #include <openssl/aes.h>
  40 #endif
  41
  42 const EVP_CIPHER *evp_aes_128_ctr(void);
  43 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
  44
  45 struct ssh_aes_ctr_ctx
  46 {
  47         AES_KEY         aes_ctx;
  48         u_char          aes_counter[AES_BLOCK_SIZE];
  49 };
  50
  51 /*
  52  * increment counter 'ctr',
  53  * the counter is of size 'len' bytes and stored in network-byte-order.
  54  * (LSB at ctr[len-1], MSB at ctr[0])
  55  */
  56 static void
  57 ssh_ctr_inc(u_char *ctr, u_int len)
  58 {
  59         int i;
  60
  61         for (i = len - 1; i >= 0; i--)
  62                 if (++ctr[i])   /* continue on overflow */
  63                         return;
  64 }
  65
  66 static int
  67 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
  68     u_int len)
  69 {
  70         struct ssh_aes_ctr_ctx *c;
  71         u_int n = 0;
  72         u_char buf[AES_BLOCK_SIZE];
  73
  74         if (len == 0)
  75                 return (1);
  76         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
  77                 return (0);
  78
  79         while ((len--) > 0) {
  80                 if (n == 0) {
  81                         AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
  82                         ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
  83                 }
  84                 *(dest++) = *(src++) ^ buf[n];
  85                 n = (n + 1) % AES_BLOCK_SIZE;
  86         }
  87         return (1);
  88 }
  89
  90 static int
  91 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
  92     int enc)
  93 {
  94         struct ssh_aes_ctr_ctx *c;
  95
  96         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
  97                 c = xmalloc(sizeof(*c));
  98                 EVP_CIPHER_CTX_set_app_data(ctx, c);
  99         }
 100         if (key != NULL)
 101                 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
 102                     &c->aes_ctx);
 103         if (iv != NULL)
 104                 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
 105         return (1);
 106 }
 107
 108 static int
 109 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
 110 {
 111         struct ssh_aes_ctr_ctx *c;
 112
 113         if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
 114                 memset(c, 0, sizeof(*c));
 115                 xfree(c);
 116                 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 117         }
 118         return (1);
 119 }
 120
 121 void
 122 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
 123 {
 124         struct ssh_aes_ctr_ctx *c;
 125
 126         if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
 127                 fatal("ssh_aes_ctr_iv: no context");
 128         if (doset)
 129                 memcpy(c->aes_counter, iv, len);
 130         else
 131                 memcpy(iv, c->aes_counter, len);
 132 }
 133
 134 const EVP_CIPHER *
 135 evp_aes_128_ctr(void)
 136 {
 137         static EVP_CIPHER aes_ctr;
 138
 139         memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
 140         aes_ctr.nid = NID_undef;
 141         aes_ctr.block_size = AES_BLOCK_SIZE;
 142         aes_ctr.iv_len = AES_BLOCK_SIZE;
 143         aes_ctr.key_len = 16;
 144         aes_ctr.init = ssh_aes_ctr_init;
 145         aes_ctr.cleanup = ssh_aes_ctr_cleanup;
 146         aes_ctr.do_cipher = ssh_aes_ctr;
 147 #ifndef SSH_OLD_EVP
 148         aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 149             EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
 150 #endif
 151         return (&aes_ctr);
 152 }