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/* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
/*
* Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#include "xmalloc.h"
#include "log.h"
const EVP_CIPHER *evp_aes_128_ctr(void);
void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, size_t);
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, size_t 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,
size_t len)
{
struct ssh_aes_ctr_ctx *c;
size_t 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, EVP_CIPHER_CTX_key_length(ctx) * 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, size_t 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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