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/*
* Copyright (c) 2003 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
RCSID("$OpenBSD: cipher-ctr.c,v 1.1 2003/05/17 04:27:52 markus Exp $");
#include <openssl/evp.h>
#include "log.h"
#include "xmalloc.h"
#if OPENSSL_VERSION_NUMBER < 0x00907000L
#include "rijndael.h"
#define AES_KEY rijndael_ctx
#define AES_BLOCK_SIZE 16
#define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
#define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
#else
#include <openssl/aes.h>
#endif
const EVP_CIPHER *evp_aes_128_ctr(void);
void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
struct ssh_aes_ctr_ctx
{
AES_KEY aes_ctx;
u_char aes_counter[AES_BLOCK_SIZE];
};
/*
* increment counter 'ctr',
* the counter is of size 'len' bytes and stored in network-byte-order.
* (LSB at ctr[len-1], MSB at ctr[0])
*/
static void
ssh_ctr_inc(u_char *ctr, u_int len)
{
int i;
for (i = len - 1; i >= 0; i--)
if (++ctr[i]) /* continue on overflow */
return;
}
static int
ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
u_int len)
{
struct ssh_aes_ctr_ctx *c;
u_int n = 0;
u_char buf[AES_BLOCK_SIZE];
if (len == 0)
return (1);
if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
return (0);
while ((len--) > 0) {
if (n == 0) {
AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
}
*(dest++) = *(src++) ^ buf[n];
n = (n + 1) % AES_BLOCK_SIZE;
}
return (1);
}
static int
ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
int enc)
{
struct ssh_aes_ctr_ctx *c;
if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
c = xmalloc(sizeof(*c));
EVP_CIPHER_CTX_set_app_data(ctx, c);
}
if (key != NULL)
AES_set_encrypt_key(key, ctx->key_len * 8, &c->aes_ctx);
if (iv != NULL)
memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
return (1);
}
static int
ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
{
struct ssh_aes_ctr_ctx *c;
if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
memset(c, 0, sizeof(*c));
xfree(c);
EVP_CIPHER_CTX_set_app_data(ctx, NULL);
}
return (1);
}
void
ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
{
struct ssh_aes_ctr_ctx *c;
if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
fatal("ssh_aes_ctr_iv: no context");
if (doset)
memcpy(c->aes_counter, iv, len);
else
memcpy(iv, c->aes_counter, len);
}
const EVP_CIPHER *
evp_aes_128_ctr(void)
{
static EVP_CIPHER aes_ctr;
memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
aes_ctr.nid = NID_undef;
aes_ctr.block_size = AES_BLOCK_SIZE;
aes_ctr.iv_len = AES_BLOCK_SIZE;
aes_ctr.key_len = 16;
aes_ctr.init = ssh_aes_ctr_init;
aes_ctr.cleanup = ssh_aes_ctr_cleanup;
aes_ctr.do_cipher = ssh_aes_ctr;
aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
return (&aes_ctr);
}
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