/* $OpenBSD: cipher.c,v 1.82 2009/01/26 09:58:15 markus Exp $ */
/*
* 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"
#include <sys/types.h>
#include <openssl/md5.h>
#include <string.h>
#include <stdarg.h>
#include "xmalloc.h"
#include "log.h"
#include "cipher.h"
/* compatibility with old or broken OpenSSL versions */
#include "openbsd-compat/openssl-compat.h"
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;
u_int discard_len;
u_int cbc_mode;
const EVP_CIPHER *(*evptype)(void);
} ciphers[] = {
{ "none", SSH_CIPHER_NONE, 8, 0, 0, 0, EVP_enc_null },
{ "des", SSH_CIPHER_DES, 8, 8, 0, 1, EVP_des_cbc },
{ "3des", SSH_CIPHER_3DES, 8, 16, 0, 1, evp_ssh1_3des },
{ "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 1, evp_ssh1_bf },
{ "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 1, EVP_des_ede3_cbc },
{ "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_bf_cbc },
#ifndef ANDROID
{ "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc },
#endif
{ "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 },
{ "arcfour128", SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 },
{ "arcfour256", SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 },
{ "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc },
{ "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc },
{ "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
{ "rijndael-cbc@lysator.liu.se",
SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
{ "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr },
{ "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr },
{ "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr },
#ifdef USE_CIPHER_ACSS
{ "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss },
#endif
{ NULL, SSH_CIPHER_INVALID, 0, 0, 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_is_cbc(const Cipher *c)
{
return (c->cbc_mode);
}
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;
int klen;
#endif
u_char *junk, *discard;
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 != (u_int)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
if (cipher->discard_len > 0) {
junk = xmalloc(cipher->discard_len);
discard = xmalloc(cipher->discard_len);
if (EVP_Cipher(&cc->evp, discard, junk,
cipher->discard_len) == 0)
fatal("evp_crypt: EVP_Cipher failed during discard");
memset(discard, 0, cipher->discard_len);
xfree(junk);
xfree(discard);
}
}
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 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 ((u_int)evplen != len)
fatal("%s: wrong iv length %d != %d", __func__,
evplen, len);
#ifdef USE_BUILTIN_RIJNDAEL
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;
#ifdef USE_BUILTIN_RIJNDAEL
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);
}
}