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/*
* 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 1.51 2002/02/14 23:41:01 markus Exp $");
#include "xmalloc.h"
#include "log.h"
#include "cipher.h"
#include <openssl/md5.h>
struct Cipher {
char *name;
int number; /* for ssh1 only */
u_int block_size;
u_int key_len;
void (*setkey)(CipherContext *, const u_char *, u_int);
void (*setiv)(CipherContext *, const u_char *, u_int);
void (*encrypt)(CipherContext *, u_char *, const u_char *, u_int);
void (*decrypt)(CipherContext *, u_char *, const u_char *, u_int);
};
/* no encryption */
static void
none_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
}
static void
none_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
}
static void
none_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
memcpy(dest, src, len);
}
/* DES */
static void
des_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
static int dowarn = 1;
if (dowarn) {
error("Warning: use of DES is strongly discouraged "
"due to cryptographic weaknesses");
dowarn = 0;
}
des_set_key((void *)key, cc->u.des.key);
}
static void
des_ssh1_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
memset(cc->u.des.iv, 0, sizeof(cc->u.des.iv));
}
static void
des_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
DES_ENCRYPT);
}
static void
des_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
DES_DECRYPT);
}
/* 3DES */
static void
des3_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
des_set_key((void *) key, cc->u.des3.key1);
des_set_key((void *) (key+8), cc->u.des3.key2);
des_set_key((void *) (key+16), cc->u.des3.key3);
}
static void
des3_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
memset(cc->u.des3.iv1, 0, sizeof(cc->u.des3.iv1));
memset(cc->u.des3.iv2, 0, sizeof(cc->u.des3.iv2));
memset(cc->u.des3.iv3, 0, sizeof(cc->u.des3.iv3));
if (iv == NULL)
return;
memcpy(cc->u.des3.iv3, (char *)iv, 8);
}
static void
des3_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
des_ede3_cbc_encrypt(src, dest, len,
cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
&cc->u.des3.iv3, DES_ENCRYPT);
}
static void
des3_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
des_ede3_cbc_encrypt(src, dest, len,
cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
&cc->u.des3.iv3, DES_DECRYPT);
}
/*
* 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.
*/
static void
des3_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
des_set_key((void *) key, cc->u.des3.key1);
des_set_key((void *) (key+8), cc->u.des3.key2);
if (keylen <= 16)
des_set_key((void *) key, cc->u.des3.key3);
else
des_set_key((void *) (key+16), cc->u.des3.key3);
}
static void
des3_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
des_ncbc_encrypt(src, dest, len, cc->u.des3.key1, &cc->u.des3.iv1,
DES_ENCRYPT);
des_ncbc_encrypt(dest, dest, len, cc->u.des3.key2, &cc->u.des3.iv2,
DES_DECRYPT);
des_ncbc_encrypt(dest, dest, len, cc->u.des3.key3, &cc->u.des3.iv3,
DES_ENCRYPT);
}
static void
des3_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
des_ncbc_encrypt(src, dest, len, cc->u.des3.key3, &cc->u.des3.iv3,
DES_DECRYPT);
des_ncbc_encrypt(dest, dest, len, cc->u.des3.key2, &cc->u.des3.iv2,
DES_ENCRYPT);
des_ncbc_encrypt(dest, dest, len, cc->u.des3.key1, &cc->u.des3.iv1,
DES_DECRYPT);
}
/* Blowfish */
static void
blowfish_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
BF_set_key(&cc->u.bf.key, keylen, (u_char *)key);
}
static void
blowfish_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
if (iv == NULL)
memset(cc->u.bf.iv, 0, 8);
else
memcpy(cc->u.bf.iv, (char *)iv, 8);
}
static void
blowfish_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
BF_ENCRYPT);
}
static void
blowfish_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
BF_DECRYPT);
}
/*
* 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)
{
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 void
blowfish_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
swap_bytes(src, dest, len);
BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
BF_ENCRYPT);
swap_bytes(dest, dest, len);
}
static void
blowfish_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
swap_bytes(src, dest, len);
BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
BF_DECRYPT);
swap_bytes(dest, dest, len);
}
/* alleged rc4 */
static void
arcfour_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
RC4_set_key(&cc->u.rc4, keylen, (u_char *)key);
}
static void
arcfour_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
RC4(&cc->u.rc4, len, (u_char *)src, dest);
}
/* CAST */
static void
cast_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
CAST_set_key(&cc->u.cast.key, keylen, (u_char *) key);
}
static void
cast_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
if (iv == NULL)
fatal("no IV for %s.", cc->cipher->name);
memcpy(cc->u.cast.iv, (char *)iv, 8);
}
static void
cast_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
CAST_ENCRYPT);
}
static void
cast_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
CAST_DECRYPT);
}
/* RIJNDAEL */
#define RIJNDAEL_BLOCKSIZE 16
static void
rijndael_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
rijndael_set_key(&cc->u.rijndael.enc, (char *)key, 8*keylen, 1);
rijndael_set_key(&cc->u.rijndael.dec, (char *)key, 8*keylen, 0);
}
static void
rijndael_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
if (iv == NULL || ivlen != RIJNDAEL_BLOCKSIZE)
fatal("bad/no IV for %s.", cc->cipher->name);
memcpy(cc->u.rijndael.iv, iv, RIJNDAEL_BLOCKSIZE);
}
static void
rijndael_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
rijndael_ctx *ctx = &cc->u.rijndael.enc;
u_char *iv = cc->u.rijndael.iv;
u_char in[RIJNDAEL_BLOCKSIZE];
u_char *cprev, *cnow, *plain;
int i, j, blocks = len / RIJNDAEL_BLOCKSIZE;
if (len == 0)
return;
if (len % RIJNDAEL_BLOCKSIZE)
fatal("rijndael_cbc_encrypt: bad len %d", len);
cnow = dest;
plain = (u_char *)src;
cprev = iv;
for (i = 0; i < blocks; i++, plain+=RIJNDAEL_BLOCKSIZE,
cnow+=RIJNDAEL_BLOCKSIZE) {
for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
in[j] = plain[j] ^ cprev[j];
rijndael_encrypt(ctx, in, cnow);
cprev = cnow;
}
memcpy(iv, cprev, RIJNDAEL_BLOCKSIZE);
}
static void
rijndael_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
rijndael_ctx *ctx = &cc->u.rijndael.dec;
u_char *iv = cc->u.rijndael.iv;
u_char ivsaved[RIJNDAEL_BLOCKSIZE];
u_char *cnow = (u_char *) (src+len-RIJNDAEL_BLOCKSIZE);
u_char *plain = dest+len-RIJNDAEL_BLOCKSIZE;
u_char *ivp;
int i, j, blocks = len / RIJNDAEL_BLOCKSIZE;
if (len == 0)
return;
if (len % RIJNDAEL_BLOCKSIZE)
fatal("rijndael_cbc_decrypt: bad len %d", len);
memcpy(ivsaved, cnow, RIJNDAEL_BLOCKSIZE);
for (i = blocks; i > 0; i--, cnow-=RIJNDAEL_BLOCKSIZE,
plain-=RIJNDAEL_BLOCKSIZE) {
rijndael_decrypt(ctx, cnow, plain);
ivp = (i == 1) ? iv : cnow-RIJNDAEL_BLOCKSIZE;
for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
plain[j] ^= ivp[j];
}
memcpy(iv, ivsaved, RIJNDAEL_BLOCKSIZE);
}
Cipher ciphers[] = {
{ "none",
SSH_CIPHER_NONE, 8, 0,
none_setkey, none_setiv,
none_crypt, none_crypt },
{ "des",
SSH_CIPHER_DES, 8, 8,
des_ssh1_setkey, des_ssh1_setiv,
des_ssh1_encrypt, des_ssh1_decrypt },
{ "3des",
SSH_CIPHER_3DES, 8, 16,
des3_ssh1_setkey, des3_setiv,
des3_ssh1_encrypt, des3_ssh1_decrypt },
{ "blowfish",
SSH_CIPHER_BLOWFISH, 8, 16,
blowfish_setkey, blowfish_setiv,
blowfish_ssh1_encrypt, blowfish_ssh1_decrypt },
{ "3des-cbc",
SSH_CIPHER_SSH2, 8, 24,
des3_setkey, des3_setiv,
des3_cbc_encrypt, des3_cbc_decrypt },
{ "blowfish-cbc",
SSH_CIPHER_SSH2, 8, 16,
blowfish_setkey, blowfish_setiv,
blowfish_cbc_encrypt, blowfish_cbc_decrypt },
{ "cast128-cbc",
SSH_CIPHER_SSH2, 8, 16,
cast_setkey, cast_setiv,
cast_cbc_encrypt, cast_cbc_decrypt },
{ "arcfour",
SSH_CIPHER_SSH2, 8, 16,
arcfour_setkey, none_setiv,
arcfour_crypt, arcfour_crypt },
{ "aes128-cbc",
SSH_CIPHER_SSH2, 16, 16,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ "aes192-cbc",
SSH_CIPHER_SSH2, 16, 24,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ "aes256-cbc",
SSH_CIPHER_SSH2, 16, 32,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL, NULL, NULL, 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)
{
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;
cc->encrypt = (encrypt == CIPHER_ENCRYPT);
cipher->setkey(cc, key, keylen);
cipher->setiv(cc, iv, ivlen);
}
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 (cc->encrypt)
cc->cipher->encrypt(cc, dest, src, len);
else
cc->cipher->decrypt(cc, dest, src, len);
}
void
cipher_cleanup(CipherContext *cc)
{
memset(cc, 0, sizeof(*cc));
}
/*
* 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));
}
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