cipher.c - third_party/openssh-portable - Git at Google

 /*
  * 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 1.52 2002/02/18 13:05:32 markus Exp $");

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

 #include <openssl/md5.h>
 #include "rijndael.h"

 static EVP_CIPHER *evp_ssh1_3des(void);
 static EVP_CIPHER *evp_ssh1_bf(void);
 static EVP_CIPHER *evp_rijndael(void);

 struct Cipher {
 	char	*name;
 	int	number;		/* for ssh1 only */
 	u_int	block_size;
 	u_int	key_len;
 	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 },
 	{ "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 },

 	{ NULL,			SSH_CIPHER_ILLEGAL, 0, 0, NULL }
 };

 /*--*/

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

 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 (strcasecmp(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 *ciphers, *cp;
 	char *p;

 	if (names == NULL || strcmp(names, "") == 0)
 		return 0;
 	ciphers = 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(ciphers);
 			return 0;
 		} else {
 			debug3("cipher ok: %s [%s]", p, names);
 		}
 	}
 	debug3("ciphers ok: [%s]", names);
 	xfree(ciphers);
 	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;
 	c = cipher_by_name(name);
 	return (c==NULL) ? -1 : c->number;
 }

 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 encrypt)
 {
 	static int dowarn = 1;
 	const EVP_CIPHER *type;
 	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);
 	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
 	    (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) {
 		debug("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);
 }

 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);
 	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
 		fatal("evp_crypt: EVP_Cipher failed");
 }

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

 /*
  * 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 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, encrypt);

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

 /* Implementations for other non-EVP ciphers */

 /*
  * This is used by SSH1:
  *
  * What kind of triple DES are these 2 routines?
  *
  * Why is there a redundant initialization vector?
  *
  * If only iv3 was used, then, this would till effect have been
  * outer-cbc. However, there is also a private iv1 == iv2 which
  * perhaps makes differential analysis easier. On the other hand, the
  * private iv1 probably makes the CRC-32 attack ineffective. This is a
  * result of that there is no longer any known iv1 to use when
  * choosing the X block.
  */
 struct ssh1_3des_ctx
 {
 	EVP_CIPHER_CTX	k1, k2, k3;
 };
 static int
 ssh1_3des_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
     int enc)
 {
 	struct ssh1_3des_ctx *c;
 	u_char *k1, *k2, *k3;

 	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)
 		return (1);
 	if (enc == -1)
 		enc = ctx->encrypt;
 	k1 = k2 = k3 = (u_char *) key;
 	k2 += 8;
 	if (EVP_CIPHER_CTX_key_length(ctx) >= 16+8) {
 		if (enc)
 			k3 += 16;
 		else
 			k1 += 16;
 	}
 	EVP_CIPHER_CTX_init(&c->k1);
 	EVP_CIPHER_CTX_init(&c->k2);
 	EVP_CIPHER_CTX_init(&c->k3);
 	if (EVP_CipherInit(&c->k1, EVP_des_cbc(), k1, NULL, enc) == 0 ||
 	    EVP_CipherInit(&c->k2, EVP_des_cbc(), k2, NULL, !enc) == 0 ||
 	    EVP_CipherInit(&c->k3, EVP_des_cbc(), k3, NULL, enc) == 0) {
 		memset(c, 0, sizeof(*c));
 		xfree(c);
 		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
 		return (0);
 	}
 	return (1);
 }
 static int
 ssh1_3des_cbc(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src, u_int len)
 {
 	struct ssh1_3des_ctx *c;

 	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
 		error("ssh1_3des_cbc: no context");
 		return (0);
 	}
 	if (EVP_Cipher(&c->k1, dest, (u_char *)src, len) == 0 ||
 	    EVP_Cipher(&c->k2, dest, dest, len) == 0 ||
 	    EVP_Cipher(&c->k3, dest, dest, len) == 0)
 		return (0);
 	return (1);
 }
 static int
 ssh1_3des_cleanup(EVP_CIPHER_CTX *ctx)
 {
 	struct ssh1_3des_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);
 }
 static EVP_CIPHER *
 evp_ssh1_3des(void)
 {
 	static EVP_CIPHER ssh1_3des;

 	memset(&ssh1_3des, 0, sizeof(EVP_CIPHER));
 	ssh1_3des.nid = NID_undef;
 	ssh1_3des.block_size = 8;
 	ssh1_3des.iv_len = 0;
 	ssh1_3des.key_len = 16;
 	ssh1_3des.init = ssh1_3des_init;
 	ssh1_3des.cleanup = ssh1_3des_cleanup;
 	ssh1_3des.do_cipher = ssh1_3des_cbc;
 	ssh1_3des.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH;
 	return (&ssh1_3des);
 }

 /*
  * SSH1 uses a variation on Blowfish, all bytes must be swapped before
  * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
  */
 static void
 swap_bytes(const u_char *src, u_char *dst, int n)
 {
 	u_char c[4];

 	/* Process 4 bytes every lap. */
 	for (n = n / 4; n > 0; n--) {
 		c[3] = *src++;
 		c[2] = *src++;
 		c[1] = *src++;
 		c[0] = *src++;

 		*dst++ = c[0];
 		*dst++ = c[1];
 		*dst++ = c[2];
 		*dst++ = c[3];
 	}
 }
 static int (*orig_bf)(EVP_CIPHER_CTX *, u_char *, const u_char *, u_int) = NULL;
 static int
 bf_ssh1_cipher(EVP_CIPHER_CTX *ctx, u_char *out, const u_char *in, u_int len)
 {
 	int ret;

 	swap_bytes(in, out, len);
 	ret = (*orig_bf)(ctx, out, out, len);
 	swap_bytes(out, out, len);
 	return (ret);
 }
 static EVP_CIPHER *
 evp_ssh1_bf(void)
 {
 	static EVP_CIPHER ssh1_bf;

 	memcpy(&ssh1_bf, EVP_bf_cbc(), sizeof(EVP_CIPHER));
 	orig_bf = ssh1_bf.do_cipher;
 	ssh1_bf.nid = NID_undef;
 	ssh1_bf.do_cipher = bf_ssh1_cipher;
 	ssh1_bf.key_len = 32;
 	return (&ssh1_bf);
 }

 /* RIJNDAEL */
 #define RIJNDAEL_BLOCKSIZE 16
 struct ssh_rijndael_ctx
 {
 	rijndael_ctx	r_ctx;
 	u_char		r_iv[RIJNDAEL_BLOCKSIZE];
 };

 static int
 ssh_rijndael_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
     int enc)
 {
 	struct ssh_rijndael_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) {
 		if (enc == -1)
 			enc = ctx->encrypt;
 		rijndael_set_key(&c->r_ctx, (u_char *)key,
 		    8*EVP_CIPHER_CTX_key_length(ctx), enc);
 	}
 	if (iv != NULL)
 		memcpy(c->r_iv, iv, RIJNDAEL_BLOCKSIZE);
 	return (1);
 }
 static int
 ssh_rijndael_cbc(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
     u_int len)
 {
 	struct ssh_rijndael_ctx *c;
 	u_char buf[RIJNDAEL_BLOCKSIZE];
 	u_char *cprev, *cnow, *plain, *ivp;
 	int i, j, blocks = len / RIJNDAEL_BLOCKSIZE;

 	if (len == 0)
 		return (1);
 	if (len % RIJNDAEL_BLOCKSIZE)
 		fatal("ssh_rijndael_cbc: bad len %d", len);
 	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
 		error("ssh_rijndael_cbc: no context");
 		return (0);
 	}
 	if (ctx->encrypt) {
 		cnow  = dest;
 		plain = (u_char *)src;
 		cprev = c->r_iv;
 		for (i = 0; i < blocks; i++, plain+=RIJNDAEL_BLOCKSIZE,
 		    cnow+=RIJNDAEL_BLOCKSIZE) {
 			for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
 				buf[j] = plain[j] ^ cprev[j];
 			rijndael_encrypt(&c->r_ctx, buf, cnow);
 			cprev = cnow;
 		}
 		memcpy(c->r_iv, cprev, RIJNDAEL_BLOCKSIZE);
 	} else {
 		cnow  = (u_char *) (src+len-RIJNDAEL_BLOCKSIZE);
 		plain = dest+len-RIJNDAEL_BLOCKSIZE;

 		memcpy(buf, cnow, RIJNDAEL_BLOCKSIZE);
 		for (i = blocks; i > 0; i--, cnow-=RIJNDAEL_BLOCKSIZE,
 		    plain-=RIJNDAEL_BLOCKSIZE) {
 			rijndael_decrypt(&c->r_ctx, cnow, plain);
 			ivp = (i == 1) ? c->r_iv : cnow-RIJNDAEL_BLOCKSIZE;
 			for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
 				plain[j] ^= ivp[j];
 		}
 		memcpy(c->r_iv, buf, RIJNDAEL_BLOCKSIZE);
 	}
 	return (1);
 }
 static int
 ssh_rijndael_cleanup(EVP_CIPHER_CTX *ctx)
 {
 	struct ssh_rijndael_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);
 }
 static EVP_CIPHER *
 evp_rijndael(void)
 {
 	static EVP_CIPHER rijndal_cbc;

 	memset(&rijndal_cbc, 0, sizeof(EVP_CIPHER));
 	rijndal_cbc.nid = NID_undef;
 	rijndal_cbc.block_size = RIJNDAEL_BLOCKSIZE;
 	rijndal_cbc.iv_len = RIJNDAEL_BLOCKSIZE;
 	rijndal_cbc.key_len = 16;
 	rijndal_cbc.init = ssh_rijndael_init;
 	rijndal_cbc.cleanup = ssh_rijndael_cleanup;
 	rijndal_cbc.do_cipher = ssh_rijndael_cbc;
 	rijndal_cbc.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
 	    EVP_CIPH_ALWAYS_CALL_INIT;
 	return (&rijndal_cbc);
 }
	/*
	* 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 1.52 2002/02/18 13:05:32 markus Exp $");

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

	#include <openssl/md5.h>
	#include "rijndael.h"

	static EVP_CIPHER *evp_ssh1_3des(void);
	static EVP_CIPHER *evp_ssh1_bf(void);
	static EVP_CIPHER *evp_rijndael(void);

	struct Cipher {
	char *name;
	int number; /* for ssh1 only */
	u_int block_size;
	u_int key_len;
	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 },
	{ "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 },

	{ NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL }
	};

	/--/

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

	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 (strcasecmp(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 ciphers, cp;
	char *p;

	if (names == NULL \|\| strcmp(names, "") == 0)
	return 0;
	ciphers = 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(ciphers);
	return 0;
	} else {
	debug3("cipher ok: %s [%s]", p, names);
	}
	}
	debug3("ciphers ok: [%s]", names);
	xfree(ciphers);
	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;
	c = cipher_by_name(name);
	return (c==NULL) ? -1 : c->number;
	}

	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 encrypt)
	{
	static int dowarn = 1;
	const EVP_CIPHER *type;
	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);
	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
	(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) {
	debug("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);
	}

	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);
	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
	fatal("evp_crypt: EVP_Cipher failed");
	}

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

	/*
	* 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 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, encrypt);

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

	/* Implementations for other non-EVP ciphers */

	/*
	* This is used by SSH1:
	*
	* What kind of triple DES are these 2 routines?
	*
	* Why is there a redundant initialization vector?
	*
	* If only iv3 was used, then, this would till effect have been
	* outer-cbc. However, there is also a private iv1 == iv2 which
	* perhaps makes differential analysis easier. On the other hand, the
	* private iv1 probably makes the CRC-32 attack ineffective. This is a
	* result of that there is no longer any known iv1 to use when
	* choosing the X block.
	*/
	struct ssh1_3des_ctx
	{
	EVP_CIPHER_CTX k1, k2, k3;
	};
	static int
	ssh1_3des_init(EVP_CIPHER_CTX ctx, const u_char key, const u_char *iv,
	int enc)
	{
	struct ssh1_3des_ctx *c;
	u_char k1, k2, *k3;

	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)
	return (1);
	if (enc == -1)
	enc = ctx->encrypt;
	k1 = k2 = k3 = (u_char *) key;
	k2 += 8;
	if (EVP_CIPHER_CTX_key_length(ctx) >= 16+8) {
	if (enc)
	k3 += 16;
	else
	k1 += 16;
	}
	EVP_CIPHER_CTX_init(&c->k1);
	EVP_CIPHER_CTX_init(&c->k2);
	EVP_CIPHER_CTX_init(&c->k3);
	if (EVP_CipherInit(&c->k1, EVP_des_cbc(), k1, NULL, enc) == 0 \|\|
	EVP_CipherInit(&c->k2, EVP_des_cbc(), k2, NULL, !enc) == 0 \|\|
	EVP_CipherInit(&c->k3, EVP_des_cbc(), k3, NULL, enc) == 0) {
	memset(c, 0, sizeof(*c));
	xfree(c);
	EVP_CIPHER_CTX_set_app_data(ctx, NULL);
	return (0);
	}
	return (1);
	}
	static int
	ssh1_3des_cbc(EVP_CIPHER_CTX ctx, u_char dest, const u_char *src, u_int len)
	{
	struct ssh1_3des_ctx *c;

	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
	error("ssh1_3des_cbc: no context");
	return (0);
	}
	if (EVP_Cipher(&c->k1, dest, (u_char *)src, len) == 0 \|\|
	EVP_Cipher(&c->k2, dest, dest, len) == 0 \|\|
	EVP_Cipher(&c->k3, dest, dest, len) == 0)
	return (0);
	return (1);
	}
	static int
	ssh1_3des_cleanup(EVP_CIPHER_CTX *ctx)
	{
	struct ssh1_3des_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);
	}
	static EVP_CIPHER *
	evp_ssh1_3des(void)
	{
	static EVP_CIPHER ssh1_3des;

	memset(&ssh1_3des, 0, sizeof(EVP_CIPHER));
	ssh1_3des.nid = NID_undef;
	ssh1_3des.block_size = 8;
	ssh1_3des.iv_len = 0;
	ssh1_3des.key_len = 16;
	ssh1_3des.init = ssh1_3des_init;
	ssh1_3des.cleanup = ssh1_3des_cleanup;
	ssh1_3des.do_cipher = ssh1_3des_cbc;
	ssh1_3des.flags = EVP_CIPH_CBC_MODE \| EVP_CIPH_VARIABLE_LENGTH;
	return (&ssh1_3des);
	}

	/*
	* SSH1 uses a variation on Blowfish, all bytes must be swapped before
	* and after encryption/decryption. Thus the swap_bytes stuff (yuk).
	*/
	static void
	swap_bytes(const u_char src, u_char dst, int n)
	{
	u_char c[4];

	/* Process 4 bytes every lap. */
	for (n = n / 4; n > 0; n--) {
	c[3] = *src++;
	c[2] = *src++;
	c[1] = *src++;
	c[0] = *src++;

	*dst++ = c[0];
	*dst++ = c[1];
	*dst++ = c[2];
	*dst++ = c[3];
	}
	}
	static int (orig_bf)(EVP_CIPHER_CTX , u_char , const u_char , u_int) = NULL;
	static int
	bf_ssh1_cipher(EVP_CIPHER_CTX ctx, u_char out, const u_char *in, u_int len)
	{
	int ret;

	swap_bytes(in, out, len);
	ret = (*orig_bf)(ctx, out, out, len);
	swap_bytes(out, out, len);
	return (ret);
	}
	static EVP_CIPHER *
	evp_ssh1_bf(void)
	{
	static EVP_CIPHER ssh1_bf;

	memcpy(&ssh1_bf, EVP_bf_cbc(), sizeof(EVP_CIPHER));
	orig_bf = ssh1_bf.do_cipher;
	ssh1_bf.nid = NID_undef;
	ssh1_bf.do_cipher = bf_ssh1_cipher;
	ssh1_bf.key_len = 32;
	return (&ssh1_bf);
	}

	/* RIJNDAEL */
	#define RIJNDAEL_BLOCKSIZE 16
	struct ssh_rijndael_ctx
	{
	rijndael_ctx r_ctx;
	u_char r_iv[RIJNDAEL_BLOCKSIZE];
	};

	static int
	ssh_rijndael_init(EVP_CIPHER_CTX ctx, const u_char key, const u_char *iv,
	int enc)
	{
	struct ssh_rijndael_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) {
	if (enc == -1)
	enc = ctx->encrypt;
	rijndael_set_key(&c->r_ctx, (u_char *)key,
	8*EVP_CIPHER_CTX_key_length(ctx), enc);
	}
	if (iv != NULL)
	memcpy(c->r_iv, iv, RIJNDAEL_BLOCKSIZE);
	return (1);
	}
	static int
	ssh_rijndael_cbc(EVP_CIPHER_CTX ctx, u_char dest, const u_char *src,
	u_int len)
	{
	struct ssh_rijndael_ctx *c;
	u_char buf[RIJNDAEL_BLOCKSIZE];
	u_char cprev, cnow, plain, ivp;
	int i, j, blocks = len / RIJNDAEL_BLOCKSIZE;

	if (len == 0)
	return (1);
	if (len % RIJNDAEL_BLOCKSIZE)
	fatal("ssh_rijndael_cbc: bad len %d", len);
	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
	error("ssh_rijndael_cbc: no context");
	return (0);
	}
	if (ctx->encrypt) {
	cnow = dest;
	plain = (u_char *)src;
	cprev = c->r_iv;
	for (i = 0; i < blocks; i++, plain+=RIJNDAEL_BLOCKSIZE,
	cnow+=RIJNDAEL_BLOCKSIZE) {
	for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
	buf[j] = plain[j] ^ cprev[j];
	rijndael_encrypt(&c->r_ctx, buf, cnow);
	cprev = cnow;
	}
	memcpy(c->r_iv, cprev, RIJNDAEL_BLOCKSIZE);
	} else {
	cnow = (u_char *) (src+len-RIJNDAEL_BLOCKSIZE);
	plain = dest+len-RIJNDAEL_BLOCKSIZE;

	memcpy(buf, cnow, RIJNDAEL_BLOCKSIZE);
	for (i = blocks; i > 0; i--, cnow-=RIJNDAEL_BLOCKSIZE,
	plain-=RIJNDAEL_BLOCKSIZE) {
	rijndael_decrypt(&c->r_ctx, cnow, plain);
	ivp = (i == 1) ? c->r_iv : cnow-RIJNDAEL_BLOCKSIZE;
	for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
	plain[j] ^= ivp[j];
	}
	memcpy(c->r_iv, buf, RIJNDAEL_BLOCKSIZE);
	}
	return (1);
	}
	static int
	ssh_rijndael_cleanup(EVP_CIPHER_CTX *ctx)
	{
	struct ssh_rijndael_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);
	}
	static EVP_CIPHER *
	evp_rijndael(void)
	{
	static EVP_CIPHER rijndal_cbc;

	memset(&rijndal_cbc, 0, sizeof(EVP_CIPHER));
	rijndal_cbc.nid = NID_undef;
	rijndal_cbc.block_size = RIJNDAEL_BLOCKSIZE;
	rijndal_cbc.iv_len = RIJNDAEL_BLOCKSIZE;
	rijndal_cbc.key_len = 16;
	rijndal_cbc.init = ssh_rijndael_init;
	rijndal_cbc.cleanup = ssh_rijndael_cleanup;
	rijndal_cbc.do_cipher = ssh_rijndael_cbc;
	rijndal_cbc.flags = EVP_CIPH_CBC_MODE \| EVP_CIPH_VARIABLE_LENGTH \|
	EVP_CIPH_ALWAYS_CALL_INIT;
	return (&rijndal_cbc);
	}