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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 1.36 2000/10/14 10:01:15 markus Exp $");
#include "ssh.h"
#include "xmalloc.h"
#include <openssl/md5.h>
/* no encryption */
void
none_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
}
void
none_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
}
void
none_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
memcpy(dest, src, len);
}
/* DES */
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);
}
void
des_ssh1_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
memset(cc->u.des.iv, 0, sizeof(cc->u.des.iv));
}
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);
}
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 */
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);
}
void
des3_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
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);
}
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);
}
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.
*/
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);
}
void
des3_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
des_cblock iv1;
des_cblock *iv2 = &cc->u.des3.iv2;
des_cblock *iv3 = &cc->u.des3.iv3;
memcpy(&iv1, iv2, 8);
des_cbc_encrypt(src, dest, len, cc->u.des3.key1, &iv1, DES_ENCRYPT);
memcpy(&iv1, dest + len - 8, 8);
des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_DECRYPT);
memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
des_cbc_encrypt(dest, dest, len, cc->u.des3.key3, iv3, DES_ENCRYPT);
memcpy(iv3, dest + len - 8, 8);
}
void
des3_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
des_cblock iv1;
des_cblock *iv2 = &cc->u.des3.iv2;
des_cblock *iv3 = &cc->u.des3.iv3;
memcpy(&iv1, iv2, 8);
des_cbc_encrypt(src, dest, len, cc->u.des3.key3, iv3, DES_DECRYPT);
memcpy(iv3, src + len - 8, 8);
des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_ENCRYPT);
memcpy(iv2, dest + len - 8, 8);
des_cbc_encrypt(dest, dest, len, cc->u.des3.key1, &iv1, DES_DECRYPT);
/* memcpy(&iv1, iv2, 8); */
/* Note how iv1 == iv2 on entry and exit. */
}
/* Blowfish */
void
blowfish_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
BF_set_key(&cc->u.bf.key, keylen, (unsigned char *)key);
}
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);
}
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);
}
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 unsigned char *src, unsigned char *dst_, int n)
{
/* dst must be properly aligned. */
u_int32_t *dst = (u_int32_t *) dst_;
union {
u_int32_t i;
char c[4];
} t;
/* Process 8 bytes every lap. */
for (n = n / 8; n > 0; n--) {
t.c[3] = *src++;
t.c[2] = *src++;
t.c[1] = *src++;
t.c[0] = *src++;
*dst++ = t.i;
t.c[3] = *src++;
t.c[2] = *src++;
t.c[1] = *src++;
t.c[0] = *src++;
*dst++ = t.i;
}
}
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);
}
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 */
void
arcfour_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
RC4_set_key(&cc->u.rc4, keylen, (u_char *)key);
}
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 */
void
cast_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
CAST_set_key(&cc->u.cast.key, keylen, (unsigned char *) key);
}
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);
}
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);
}
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
void
rijndael_setkey(CipherContext *cc, const u_char *key, u_int keylen)
{
rijndael_set_key(&cc->u.rijndael.enc, (u4byte *)key, 8*keylen, 1);
rijndael_set_key(&cc->u.rijndael.dec, (u4byte *)key, 8*keylen, 0);
}
void
rijndael_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
{
if (iv == NULL)
fatal("no IV for %s.", cc->cipher->name);
memcpy((u_char *)cc->u.rijndael.iv, iv, RIJNDAEL_BLOCKSIZE);
}
void
rijndael_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
rijndael_ctx *ctx = &cc->u.rijndael.enc;
u4byte *iv = cc->u.rijndael.iv;
u4byte in[4];
u4byte *cprev, *cnow, *plain;
int i, blocks = len / RIJNDAEL_BLOCKSIZE;
if (len == 0)
return;
if (len % RIJNDAEL_BLOCKSIZE)
fatal("rijndael_cbc_encrypt: bad len %d", len);
cnow = (u4byte*) dest;
plain = (u4byte*) src;
cprev = iv;
for(i = 0; i < blocks; i++, plain+=4, cnow+=4) {
in[0] = plain[0] ^ cprev[0];
in[1] = plain[1] ^ cprev[1];
in[2] = plain[2] ^ cprev[2];
in[3] = plain[3] ^ cprev[3];
rijndael_encrypt(ctx, in, cnow);
cprev = cnow;
}
memcpy(iv, cprev, RIJNDAEL_BLOCKSIZE);
}
void
rijndael_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
u_int len)
{
rijndael_ctx *ctx = &cc->u.rijndael.dec;
u4byte *iv = cc->u.rijndael.iv;
u4byte ivsaved[4];
u4byte *cnow = (u4byte*) (src+len-RIJNDAEL_BLOCKSIZE);
u4byte *plain = (u4byte*) (dest+len-RIJNDAEL_BLOCKSIZE);
u4byte *ivp;
int i, 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-=4, plain-=4) {
rijndael_decrypt(ctx, cnow, plain);
ivp = (i == 1) ? iv : cnow-4;
plain[0] ^= ivp[0];
plain[1] ^= ivp[1];
plain[2] ^= ivp[2];
plain[3] ^= ivp[3];
}
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 },
{ "rijndael128-cbc",
SSH_CIPHER_SSH2, 16, 16,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ "rijndael192-cbc",
SSH_CIPHER_SSH2, 16, 24,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ "rijndael256-cbc",
SSH_CIPHER_SSH2, 16, 32,
rijndael_setkey, rijndael_setiv,
rijndael_cbc_encrypt, rijndael_cbc_decrypt },
{ "rijndael-cbc@lysator.liu.se",
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 }
};
/*--*/
unsigned int
cipher_mask_ssh1(int client)
{
unsigned 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)
{
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;
cipher->setkey(cc, key, keylen);
cipher->setiv(cc, iv, ivlen);
}
void
cipher_encrypt(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);
cc->cipher->encrypt(cc, dest, src, len);
}
void
cipher_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
{
if (len % cc->cipher->block_size)
fatal("cipher_decrypt: bad ciphertext length %d", len);
cc->cipher->decrypt(cc, dest, src, len);
}
/*
* 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)
{
MD5_CTX md;
unsigned 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);
memset(digest, 0, sizeof(digest));
memset(&md, 0, sizeof(md));
}
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