cipher.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  *
  * As far as I am concerned, the code I have written for this software
  * can be used freely for any purpose.  Any derived versions of this
  * software must be clearly marked as such, and if the derived work is
  * incompatible with the protocol description in the RFC file, it must be
  * called by a name other than "ssh" or "Secure Shell".
  *
  *
  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  * Copyright (c) 1999, 2000 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.c,v 1.73 2005/01/23 10:18:12 djm Exp $");

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

 #include <openssl/md5.h>

 #if OPENSSL_VERSION_NUMBER < 0x00906000L
 #define SSH_OLD_EVP
 #define EVP_CIPHER_CTX_get_app_data(e)          ((e)->app_data)
 #endif

 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 extern const EVP_CIPHER *evp_rijndael(void);
 extern void ssh_rijndael_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
 #endif

 #if !defined(EVP_CTRL_SET_ACSS_MODE)
 # if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
 extern const EVP_CIPHER *evp_acss(void);
 #  define EVP_acss evp_acss
 #  define EVP_CTRL_SET_ACSS_MODE xxx	/* used below */
 # else
 #  define EVP_acss NULL /* Don't try to support ACSS on older OpenSSL */
 # endif /* (OPENSSL_VERSION_NUMBER >= 0x00906000L) */
 #endif /* !defined(EVP_CTRL_SET_ACSS_MODE) */

 extern const EVP_CIPHER *evp_ssh1_bf(void);
 extern const EVP_CIPHER *evp_ssh1_3des(void);
 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
 extern const EVP_CIPHER *evp_aes_128_ctr(void);
 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);

 struct Cipher {
 	char	*name;
 	int	number;		/* for ssh1 only */
 	u_int	block_size;
 	u_int	key_len;
 	const EVP_CIPHER	*(*evptype)(void);
 } ciphers[] = {
 	{ "none",		SSH_CIPHER_NONE, 8, 0, EVP_enc_null },
 	{ "des",		SSH_CIPHER_DES, 8, 8, EVP_des_cbc },
 	{ "3des",		SSH_CIPHER_3DES, 8, 16, evp_ssh1_3des },
 	{ "blowfish",		SSH_CIPHER_BLOWFISH, 8, 32, evp_ssh1_bf },

 	{ "3des-cbc",		SSH_CIPHER_SSH2, 8, 24, EVP_des_ede3_cbc },
 	{ "blowfish-cbc",	SSH_CIPHER_SSH2, 8, 16, EVP_bf_cbc },
 	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, EVP_cast5_cbc },
 	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, EVP_rc4 },
 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, evp_rijndael },
 	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, evp_rijndael },
 	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
 	{ "rijndael-cbc@lysator.liu.se",
 				SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
 #else
 	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, EVP_aes_128_cbc },
 	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, EVP_aes_192_cbc },
 	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
 	{ "rijndael-cbc@lysator.liu.se",
 				SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
 #endif
 #if OPENSSL_VERSION_NUMBER >= 0x00905000L
 	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, evp_aes_128_ctr },
 	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, evp_aes_128_ctr },
 	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, evp_aes_128_ctr },
 #endif
 #if defined(EVP_CTRL_SET_ACSS_MODE)
 	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, EVP_acss },
 #endif
 	{ NULL,			SSH_CIPHER_INVALID, 0, 0, NULL }
 };

 /*--*/

 u_int
 cipher_blocksize(const Cipher *c)
 {
 	return (c->block_size);
 }

 u_int
 cipher_keylen(const Cipher *c)
 {
 	return (c->key_len);
 }

 u_int
 cipher_get_number(const Cipher *c)
 {
 	return (c->number);
 }

 u_int
 cipher_mask_ssh1(int client)
 {
 	u_int mask = 0;
 	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
 	mask |= 1 << SSH_CIPHER_BLOWFISH;
 	if (client) {
 		mask |= 1 << SSH_CIPHER_DES;
 	}
 	return mask;
 }

 Cipher *
 cipher_by_name(const char *name)
 {
 	Cipher *c;
 	for (c = ciphers; c->name != NULL; c++)
 		if (strcmp(c->name, name) == 0)
 			return c;
 	return NULL;
 }

 Cipher *
 cipher_by_number(int id)
 {
 	Cipher *c;
 	for (c = ciphers; c->name != NULL; c++)
 		if (c->number == id)
 			return c;
 	return NULL;
 }

 #define	CIPHER_SEP	","
 int
 ciphers_valid(const char *names)
 {
 	Cipher *c;
 	char *cipher_list, *cp;
 	char *p;

 	if (names == NULL || strcmp(names, "") == 0)
 		return 0;
 	cipher_list = cp = xstrdup(names);
 	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
 	    (p = strsep(&cp, CIPHER_SEP))) {
 		c = cipher_by_name(p);
 		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
 			debug("bad cipher %s [%s]", p, names);
 			xfree(cipher_list);
 			return 0;
 		} else {
 			debug3("cipher ok: %s [%s]", p, names);
 		}
 	}
 	debug3("ciphers ok: [%s]", names);
 	xfree(cipher_list);
 	return 1;
 }

 /*
  * Parses the name of the cipher.  Returns the number of the corresponding
  * cipher, or -1 on error.
  */

 int
 cipher_number(const char *name)
 {
 	Cipher *c;
 	if (name == NULL)
 		return -1;
 	for (c = ciphers; c->name != NULL; c++)
 		if (strcasecmp(c->name, name) == 0)
 			return c->number;
 	return -1;
 }

 char *
 cipher_name(int id)
 {
 	Cipher *c = cipher_by_number(id);
 	return (c==NULL) ? "<unknown>" : c->name;
 }

 void
 cipher_init(CipherContext *cc, Cipher *cipher,
     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
     int do_encrypt)
 {
 	static int dowarn = 1;
 #ifdef SSH_OLD_EVP
 	EVP_CIPHER *type;
 #else
 	const EVP_CIPHER *type;
 #endif
 	int klen;

 	if (cipher->number == SSH_CIPHER_DES) {
 		if (dowarn) {
 			error("Warning: use of DES is strongly discouraged "
 			    "due to cryptographic weaknesses");
 			dowarn = 0;
 		}
 		if (keylen > 8)
 			keylen = 8;
 	}
 	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);

 	if (keylen < cipher->key_len)
 		fatal("cipher_init: key length %d is insufficient for %s.",
 		    keylen, cipher->name);
 	if (iv != NULL && ivlen < cipher->block_size)
 		fatal("cipher_init: iv length %d is insufficient for %s.",
 		    ivlen, cipher->name);
 	cc->cipher = cipher;

 	type = (*cipher->evptype)();

 	EVP_CIPHER_CTX_init(&cc->evp);
 #ifdef SSH_OLD_EVP
 	if (type->key_len > 0 && type->key_len != keylen) {
 		debug("cipher_init: set keylen (%d -> %d)",
 		    type->key_len, keylen);
 		type->key_len = keylen;
 	}
 	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
 	    (do_encrypt == CIPHER_ENCRYPT));
 #else
 	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
 	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
 		fatal("cipher_init: EVP_CipherInit failed for %s",
 		    cipher->name);
 	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
 	if (klen > 0 && keylen != klen) {
 		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
 		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
 			fatal("cipher_init: set keylen failed (%d -> %d)",
 			    klen, keylen);
 	}
 	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
 		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
 		    cipher->name);
 #endif
 }

 void
 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
 {
 	if (len % cc->cipher->block_size)
 		fatal("cipher_encrypt: bad plaintext length %d", len);
 #ifdef SSH_OLD_EVP
 	EVP_Cipher(&cc->evp, dest, (u_char *)src, len);
 #else
 	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
 		fatal("evp_crypt: EVP_Cipher failed");
 #endif
 }

 void
 cipher_cleanup(CipherContext *cc)
 {
 #ifdef SSH_OLD_EVP
 	EVP_CIPHER_CTX_cleanup(&cc->evp);
 #else
 	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
 		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
 #endif
 }

 /*
  * Selects the cipher, and keys if by computing the MD5 checksum of the
  * passphrase and using the resulting 16 bytes as the key.
  */

 void
 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
     const char *passphrase, int do_encrypt)
 {
 	MD5_CTX md;
 	u_char digest[16];

 	MD5_Init(&md);
 	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
 	MD5_Final(digest, &md);

 	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);

 	memset(digest, 0, sizeof(digest));
 	memset(&md, 0, sizeof(md));
 }

 /*
  * Exports an IV from the CipherContext required to export the key
  * state back from the unprivileged child to the privileged parent
  * process.
  */

 int
 cipher_get_keyiv_len(const CipherContext *cc)
 {
 	Cipher *c = cc->cipher;
 	int ivlen;

 	if (c->number == SSH_CIPHER_3DES)
 		ivlen = 24;
 	else
 		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 	return (ivlen);
 }

 void
 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
 {
 	Cipher *c = cc->cipher;
 	int evplen;

 	switch (c->number) {
 	case SSH_CIPHER_SSH2:
 	case SSH_CIPHER_DES:
 	case SSH_CIPHER_BLOWFISH:
 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 		if (evplen == 0)
 			return;
 		if (evplen != len)
 			fatal("%s: wrong iv length %d != %d", __func__,
 			    evplen, len);
 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 		if (c->evptype == evp_rijndael)
 			ssh_rijndael_iv(&cc->evp, 0, iv, len);
 		else
 #endif
 		if (c->evptype == evp_aes_128_ctr)
 			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
 		else
 			memcpy(iv, cc->evp.iv, len);
 		break;
 	case SSH_CIPHER_3DES:
 		ssh1_3des_iv(&cc->evp, 0, iv, 24);
 		break;
 	default:
 		fatal("%s: bad cipher %d", __func__, c->number);
 	}
 }

 void
 cipher_set_keyiv(CipherContext *cc, u_char *iv)
 {
 	Cipher *c = cc->cipher;
 	int evplen = 0;

 	switch (c->number) {
 	case SSH_CIPHER_SSH2:
 	case SSH_CIPHER_DES:
 	case SSH_CIPHER_BLOWFISH:
 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
 		if (evplen == 0)
 			return;
 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 		if (c->evptype == evp_rijndael)
 			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
 		else
 #endif
 		if (c->evptype == evp_aes_128_ctr)
 			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
 		else
 			memcpy(cc->evp.iv, iv, evplen);
 		break;
 	case SSH_CIPHER_3DES:
 		ssh1_3des_iv(&cc->evp, 1, iv, 24);
 		break;
 	default:
 		fatal("%s: bad cipher %d", __func__, c->number);
 	}
 }

 #if OPENSSL_VERSION_NUMBER < 0x00907000L
 #define EVP_X_STATE(evp)	&(evp).c
 #define EVP_X_STATE_LEN(evp)	sizeof((evp).c)
 #else
 #define EVP_X_STATE(evp)	(evp).cipher_data
 #define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
 #endif

 int
 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
 {
 	Cipher *c = cc->cipher;
 	int plen = 0;

 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 		plen = EVP_X_STATE_LEN(cc->evp);
 		if (dat == NULL)
 			return (plen);
 		memcpy(dat, EVP_X_STATE(cc->evp), plen);
 	}
 	return (plen);
 }

 void
 cipher_set_keycontext(CipherContext *cc, u_char *dat)
 {
 	Cipher *c = cc->cipher;
 	int plen;

 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
 		plen = EVP_X_STATE_LEN(cc->evp);
 		memcpy(EVP_X_STATE(cc->evp), dat, plen);
 	}
 }
	/*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	*
	* As far as I am concerned, the code I have written for this software
	* can be used freely for any purpose. Any derived versions of this
	* software must be clearly marked as such, and if the derived work is
	* incompatible with the protocol description in the RFC file, it must be
	* called by a name other than "ssh" or "Secure Shell".
	*
	*
	* Copyright (c) 1999 Niels Provos. All rights reserved.
	* Copyright (c) 1999, 2000 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.c,v 1.73 2005/01/23 10:18:12 djm Exp $");

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

	#include <openssl/md5.h>

	#if OPENSSL_VERSION_NUMBER < 0x00906000L
	#define SSH_OLD_EVP
	#define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
	#endif

	#if OPENSSL_VERSION_NUMBER < 0x00907000L
	extern const EVP_CIPHER *evp_rijndael(void);
	extern void ssh_rijndael_iv(EVP_CIPHER_CTX , int, u_char , u_int);
	#endif

	#if !defined(EVP_CTRL_SET_ACSS_MODE)
	# if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
	extern const EVP_CIPHER *evp_acss(void);
	# define EVP_acss evp_acss
	# define EVP_CTRL_SET_ACSS_MODE xxx /* used below */
	# else
	# define EVP_acss NULL /* Don't try to support ACSS on older OpenSSL */
	# endif /* (OPENSSL_VERSION_NUMBER >= 0x00906000L) */
	#endif /* !defined(EVP_CTRL_SET_ACSS_MODE) */

	extern const EVP_CIPHER *evp_ssh1_bf(void);
	extern const EVP_CIPHER *evp_ssh1_3des(void);
	extern void ssh1_3des_iv(EVP_CIPHER_CTX , int, u_char , int);
	extern const EVP_CIPHER *evp_aes_128_ctr(void);
	extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX , int, u_char , u_int);

	struct Cipher {
	char *name;
	int number; /* for ssh1 only */
	u_int block_size;
	u_int key_len;
	const EVP_CIPHER (evptype)(void);
	} ciphers[] = {
	{ "none", SSH_CIPHER_NONE, 8, 0, EVP_enc_null },
	{ "des", SSH_CIPHER_DES, 8, 8, EVP_des_cbc },
	{ "3des", SSH_CIPHER_3DES, 8, 16, evp_ssh1_3des },
	{ "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, evp_ssh1_bf },

	{ "3des-cbc", SSH_CIPHER_SSH2, 8, 24, EVP_des_ede3_cbc },
	{ "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_bf_cbc },
	{ "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_cast5_cbc },
	{ "arcfour", SSH_CIPHER_SSH2, 8, 16, EVP_rc4 },
	#if OPENSSL_VERSION_NUMBER < 0x00907000L
	{ "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, evp_rijndael },
	{ "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, evp_rijndael },
	{ "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
	{ "rijndael-cbc@lysator.liu.se",
	SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
	#else
	{ "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, EVP_aes_128_cbc },
	{ "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, EVP_aes_192_cbc },
	{ "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
	{ "rijndael-cbc@lysator.liu.se",
	SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc },
	#endif
	#if OPENSSL_VERSION_NUMBER >= 0x00905000L
	{ "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, evp_aes_128_ctr },
	{ "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, evp_aes_128_ctr },
	{ "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, evp_aes_128_ctr },
	#endif
	#if defined(EVP_CTRL_SET_ACSS_MODE)
	{ "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, EVP_acss },
	#endif
	{ NULL, SSH_CIPHER_INVALID, 0, 0, NULL }
	};

	/--/

	u_int
	cipher_blocksize(const Cipher *c)
	{
	return (c->block_size);
	}

	u_int
	cipher_keylen(const Cipher *c)
	{
	return (c->key_len);
	}

	u_int
	cipher_get_number(const Cipher *c)
	{
	return (c->number);
	}

	u_int
	cipher_mask_ssh1(int client)
	{
	u_int mask = 0;
	mask \|= 1 << SSH_CIPHER_3DES; /* Mandatory */
	mask \|= 1 << SSH_CIPHER_BLOWFISH;
	if (client) {
	mask \|= 1 << SSH_CIPHER_DES;
	}
	return mask;
	}

	Cipher *
	cipher_by_name(const char *name)
	{
	Cipher *c;
	for (c = ciphers; c->name != NULL; c++)
	if (strcmp(c->name, name) == 0)
	return c;
	return NULL;
	}

	Cipher *
	cipher_by_number(int id)
	{
	Cipher *c;
	for (c = ciphers; c->name != NULL; c++)
	if (c->number == id)
	return c;
	return NULL;
	}

	#define CIPHER_SEP ","
	int
	ciphers_valid(const char *names)
	{
	Cipher *c;
	char cipher_list, cp;
	char *p;

	if (names == NULL \|\| strcmp(names, "") == 0)
	return 0;
	cipher_list = cp = xstrdup(names);
	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
	(p = strsep(&cp, CIPHER_SEP))) {
	c = cipher_by_name(p);
	if (c == NULL \|\| c->number != SSH_CIPHER_SSH2) {
	debug("bad cipher %s [%s]", p, names);
	xfree(cipher_list);
	return 0;
	} else {
	debug3("cipher ok: %s [%s]", p, names);
	}
	}
	debug3("ciphers ok: [%s]", names);
	xfree(cipher_list);
	return 1;
	}

	/*
	* Parses the name of the cipher. Returns the number of the corresponding
	* cipher, or -1 on error.
	*/

	int
	cipher_number(const char *name)
	{
	Cipher *c;
	if (name == NULL)
	return -1;
	for (c = ciphers; c->name != NULL; c++)
	if (strcasecmp(c->name, name) == 0)
	return c->number;
	return -1;
	}

	char *
	cipher_name(int id)
	{
	Cipher *c = cipher_by_number(id);
	return (c==NULL) ? "<unknown>" : c->name;
	}

	void
	cipher_init(CipherContext cc, Cipher cipher,
	const u_char key, u_int keylen, const u_char iv, u_int ivlen,
	int do_encrypt)
	{
	static int dowarn = 1;
	#ifdef SSH_OLD_EVP
	EVP_CIPHER *type;
	#else
	const EVP_CIPHER *type;
	#endif
	int klen;

	if (cipher->number == SSH_CIPHER_DES) {
	if (dowarn) {
	error("Warning: use of DES is strongly discouraged "
	"due to cryptographic weaknesses");
	dowarn = 0;
	}
	if (keylen > 8)
	keylen = 8;
	}
	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);

	if (keylen < cipher->key_len)
	fatal("cipher_init: key length %d is insufficient for %s.",
	keylen, cipher->name);
	if (iv != NULL && ivlen < cipher->block_size)
	fatal("cipher_init: iv length %d is insufficient for %s.",
	ivlen, cipher->name);
	cc->cipher = cipher;

	type = (*cipher->evptype)();

	EVP_CIPHER_CTX_init(&cc->evp);
	#ifdef SSH_OLD_EVP
	if (type->key_len > 0 && type->key_len != keylen) {
	debug("cipher_init: set keylen (%d -> %d)",
	type->key_len, keylen);
	type->key_len = keylen;
	}
	EVP_CipherInit(&cc->evp, type, (u_char )key, (u_char )iv,
	(do_encrypt == CIPHER_ENCRYPT));
	#else
	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
	(do_encrypt == CIPHER_ENCRYPT)) == 0)
	fatal("cipher_init: EVP_CipherInit failed for %s",
	cipher->name);
	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
	if (klen > 0 && keylen != klen) {
	debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
	if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
	fatal("cipher_init: set keylen failed (%d -> %d)",
	klen, keylen);
	}
	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
	fatal("cipher_init: EVP_CipherInit: set key failed for %s",
	cipher->name);
	#endif
	}

	void
	cipher_crypt(CipherContext cc, u_char dest, const u_char *src, u_int len)
	{
	if (len % cc->cipher->block_size)
	fatal("cipher_encrypt: bad plaintext length %d", len);
	#ifdef SSH_OLD_EVP
	EVP_Cipher(&cc->evp, dest, (u_char *)src, len);
	#else
	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
	fatal("evp_crypt: EVP_Cipher failed");
	#endif
	}

	void
	cipher_cleanup(CipherContext *cc)
	{
	#ifdef SSH_OLD_EVP
	EVP_CIPHER_CTX_cleanup(&cc->evp);
	#else
	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
	error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
	#endif
	}

	/*
	* Selects the cipher, and keys if by computing the MD5 checksum of the
	* passphrase and using the resulting 16 bytes as the key.
	*/

	void
	cipher_set_key_string(CipherContext cc, Cipher cipher,
	const char *passphrase, int do_encrypt)
	{
	MD5_CTX md;
	u_char digest[16];

	MD5_Init(&md);
	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
	MD5_Final(digest, &md);

	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);

	memset(digest, 0, sizeof(digest));
	memset(&md, 0, sizeof(md));
	}

	/*
	* Exports an IV from the CipherContext required to export the key
	* state back from the unprivileged child to the privileged parent
	* process.
	*/

	int
	cipher_get_keyiv_len(const CipherContext *cc)
	{
	Cipher *c = cc->cipher;
	int ivlen;

	if (c->number == SSH_CIPHER_3DES)
	ivlen = 24;
	else
	ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
	return (ivlen);
	}

	void
	cipher_get_keyiv(CipherContext cc, u_char iv, u_int len)
	{
	Cipher *c = cc->cipher;
	int evplen;

	switch (c->number) {
	case SSH_CIPHER_SSH2:
	case SSH_CIPHER_DES:
	case SSH_CIPHER_BLOWFISH:
	evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
	if (evplen == 0)
	return;
	if (evplen != len)
	fatal("%s: wrong iv length %d != %d", __func__,
	evplen, len);
	#if OPENSSL_VERSION_NUMBER < 0x00907000L
	if (c->evptype == evp_rijndael)
	ssh_rijndael_iv(&cc->evp, 0, iv, len);
	else
	#endif
	if (c->evptype == evp_aes_128_ctr)
	ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
	else
	memcpy(iv, cc->evp.iv, len);
	break;
	case SSH_CIPHER_3DES:
	ssh1_3des_iv(&cc->evp, 0, iv, 24);
	break;
	default:
	fatal("%s: bad cipher %d", __func__, c->number);
	}
	}

	void
	cipher_set_keyiv(CipherContext cc, u_char iv)
	{
	Cipher *c = cc->cipher;
	int evplen = 0;

	switch (c->number) {
	case SSH_CIPHER_SSH2:
	case SSH_CIPHER_DES:
	case SSH_CIPHER_BLOWFISH:
	evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
	if (evplen == 0)
	return;
	#if OPENSSL_VERSION_NUMBER < 0x00907000L
	if (c->evptype == evp_rijndael)
	ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
	else
	#endif
	if (c->evptype == evp_aes_128_ctr)
	ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
	else
	memcpy(cc->evp.iv, iv, evplen);
	break;
	case SSH_CIPHER_3DES:
	ssh1_3des_iv(&cc->evp, 1, iv, 24);
	break;
	default:
	fatal("%s: bad cipher %d", __func__, c->number);
	}
	}

	#if OPENSSL_VERSION_NUMBER < 0x00907000L
	#define EVP_X_STATE(evp) &(evp).c
	#define EVP_X_STATE_LEN(evp) sizeof((evp).c)
	#else
	#define EVP_X_STATE(evp) (evp).cipher_data
	#define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size
	#endif

	int
	cipher_get_keycontext(const CipherContext cc, u_char dat)
	{
	Cipher *c = cc->cipher;
	int plen = 0;

	if (c->evptype == EVP_rc4 \|\| c->evptype == EVP_acss) {
	plen = EVP_X_STATE_LEN(cc->evp);
	if (dat == NULL)
	return (plen);
	memcpy(dat, EVP_X_STATE(cc->evp), plen);
	}
	return (plen);
	}

	void
	cipher_set_keycontext(CipherContext cc, u_char dat)
	{
	Cipher *c = cc->cipher;
	int plen;

	if (c->evptype == EVP_rc4 \|\| c->evptype == EVP_acss) {
	plen = EVP_X_STATE_LEN(cc->evp);
	memcpy(EVP_X_STATE(cc->evp), dat, plen);
	}
	}