[openssh.git] / cipher-ctr.c

/* $OpenBSD: cipher-ctr.c,v 1.10 2006/08/03 03:34:42 deraadt 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 "includes.h"

#include <sys/types.h>

#include <string.h>

#include <openssl/evp.h>

#include "xmalloc.h"
#include "log.h"

/* compatibility with old or broken OpenSSL versions */
#include "openbsd-compat/openssl-compat.h"

#ifdef USE_BUILTIN_RIJNDAEL
#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, 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, 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;
#ifndef SSH_OLD_EVP
	aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
#endif
	return (&aes_ctr);
}
Commit	Line	Data
31652869	1	/* $OpenBSD: cipher-ctr.c,v 1.10 2006/08/03 03:34:42 deraadt Exp $ */
25b66522	2	/*
0a59bd6b	3	* Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
25b66522	4	*
0a59bd6b	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.
25b66522	8	*
0a59bd6b	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.
25b66522	16	*/
25b66522	17	#include "includes.h"
25b66522	18
31652869	19	#include <sys/types.h>
31652869	20
00146caa	21	#include <string.h>
00146caa	22
25b66522	23	#include <openssl/evp.h>
25b66522	24
25b66522	25	#include "xmalloc.h"
31652869	26	#include "log.h"
25b66522	27
e5146707	28	/* compatibility with old or broken OpenSSL versions */
e5146707	29	#include "openbsd-compat/openssl-compat.h"
0a23d79f	30
e5146707	31	#ifdef USE_BUILTIN_RIJNDAEL
25b66522	32	#include "rijndael.h"
	33	#define AES_KEY rijndael_ctx
	34	#define AES_BLOCK_SIZE 16
	35	#define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
	36	#define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
	37	#else
	38	#include <openssl/aes.h>
	39	#endif
	40
	41	const EVP_CIPHER *evp_aes_128_ctr(void);
	42	void ssh_aes_ctr_iv(EVP_CIPHER_CTX , int, u_char , u_int);
	43
	44	struct ssh_aes_ctr_ctx
	45	{
	46	AES_KEY aes_ctx;
	47	u_char aes_counter[AES_BLOCK_SIZE];
	48	};
	49
	50	/*
	51	* increment counter 'ctr',
	52	* the counter is of size 'len' bytes and stored in network-byte-order.
	53	* (LSB at ctr[len-1], MSB at ctr[0])
	54	*/
	55	static void
	56	ssh_ctr_inc(u_char *ctr, u_int len)
	57	{
	58	int i;
	59
	60	for (i = len - 1; i >= 0; i--)
	61	if (++ctr[i]) /* continue on overflow */
	62	return;
	63	}
	64
	65	static int
	66	ssh_aes_ctr(EVP_CIPHER_CTX ctx, u_char dest, const u_char *src,
	67	u_int len)
	68	{
	69	struct ssh_aes_ctr_ctx *c;
	70	u_int n = 0;
	71	u_char buf[AES_BLOCK_SIZE];
	72
	73	if (len == 0)
	74	return (1);
	75	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
	76	return (0);
	77
	78	while ((len--) > 0) {
	79	if (n == 0) {
	80	AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
	81	ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
	82	}
	83	(dest++) = (src++) ^ buf[n];
	84	n = (n + 1) % AES_BLOCK_SIZE;
	85	}
	86	return (1);
	87	}
	88
	89	static int
	90	ssh_aes_ctr_init(EVP_CIPHER_CTX ctx, const u_char key, const u_char *iv,
	91	int enc)
	92	{
	93	struct ssh_aes_ctr_ctx *c;
	94
	95	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
96	c = xmalloc(sizeof(*c));
97	EVP_CIPHER_CTX_set_app_data(ctx, c);
98	}
99	if (key != NULL)
59d51274	100	AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
4e2e5cfd	101	&c->aes_ctx);
25b66522	102	if (iv != NULL)
	103	memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
	104	return (1);
	105	}
	106
	107	static int
	108	ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
	109	{
	110	struct ssh_aes_ctr_ctx *c;
	111
	112	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
	113	memset(c, 0, sizeof(*c));
	114	xfree(c);
	115	EVP_CIPHER_CTX_set_app_data(ctx, NULL);
	116	}
	117	return (1);
	118	}
	119
	120	void
	121	ssh_aes_ctr_iv(EVP_CIPHER_CTX evp, int doset, u_char iv, u_int len)
	122	{
	123	struct ssh_aes_ctr_ctx *c;
	124
	125	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
	126	fatal("ssh_aes_ctr_iv: no context");
	127	if (doset)
	128	memcpy(c->aes_counter, iv, len);
	129	else
	130	memcpy(iv, c->aes_counter, len);
	131	}
	132
	133	const EVP_CIPHER *
	134	evp_aes_128_ctr(void)
	135	{
	136	static EVP_CIPHER aes_ctr;
	137
	138	memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
	139	aes_ctr.nid = NID_undef;
	140	aes_ctr.block_size = AES_BLOCK_SIZE;
	141	aes_ctr.iv_len = AES_BLOCK_SIZE;
	142	aes_ctr.key_len = 16;
	143	aes_ctr.init = ssh_aes_ctr_init;
	144	aes_ctr.cleanup = ssh_aes_ctr_cleanup;
	145	aes_ctr.do_cipher = ssh_aes_ctr;
0a23d79f	146	#ifndef SSH_OLD_EVP
25b66522	147	aes_ctr.flags = EVP_CIPH_CBC_MODE \| EVP_CIPH_VARIABLE_LENGTH \|
25b66522	148	EVP_CIPH_ALWAYS_CALL_INIT \| EVP_CIPH_CUSTOM_IV;
0a23d79f	149	#endif
25b66522	150	return (&aes_ctr);
25b66522	151	}