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openssh-portable/cipher.c

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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 1.52 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);
}
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