489 lines
13 KiB
C
489 lines
13 KiB
C
/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*
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*
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* Copyright (c) 1999 Niels Provos. All rights reserved.
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* Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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RCSID("$OpenBSD: cipher.c,v 1.30 2000/09/07 20:27:50 deraadt Exp $");
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RCSID("$FreeBSD$");
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#include "ssh.h"
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#include "cipher.h"
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#include "xmalloc.h"
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#include <openssl/md5.h>
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/*
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* This is used by SSH1:
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*
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* What kind of triple DES are these 2 routines?
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*
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* Why is there a redundant initialization vector?
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*
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* If only iv3 was used, then, this would till effect have been
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* outer-cbc. However, there is also a private iv1 == iv2 which
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* perhaps makes differential analysis easier. On the other hand, the
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* private iv1 probably makes the CRC-32 attack ineffective. This is a
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* result of that there is no longer any known iv1 to use when
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* choosing the X block.
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*/
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void
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SSH_3CBC_ENCRYPT(des_key_schedule ks1,
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des_key_schedule ks2, des_cblock * iv2,
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des_key_schedule ks3, des_cblock * iv3,
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unsigned char *dest, unsigned char *src,
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unsigned int len)
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{
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des_cblock iv1;
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memcpy(&iv1, iv2, 8);
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des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
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memcpy(&iv1, dest + len - 8, 8);
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des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
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memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
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des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
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memcpy(iv3, dest + len - 8, 8);
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}
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void
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SSH_3CBC_DECRYPT(des_key_schedule ks1,
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des_key_schedule ks2, des_cblock * iv2,
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des_key_schedule ks3, des_cblock * iv3,
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unsigned char *dest, unsigned char *src,
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unsigned int len)
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{
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des_cblock iv1;
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memcpy(&iv1, iv2, 8);
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des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
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memcpy(iv3, src + len - 8, 8);
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des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
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memcpy(iv2, dest + len - 8, 8);
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des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
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/* memcpy(&iv1, iv2, 8); */
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/* Note how iv1 == iv2 on entry and exit. */
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}
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/*
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* SSH1 uses a variation on Blowfish, all bytes must be swapped before
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* and after encryption/decryption. Thus the swap_bytes stuff (yuk).
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*/
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static void
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swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
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{
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/* dst must be properly aligned. */
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u_int32_t *dst = (u_int32_t *) dst_;
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union {
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u_int32_t i;
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char c[4];
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} t;
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/* Process 8 bytes every lap. */
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for (n = n / 8; n > 0; n--) {
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t.c[3] = *src++;
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t.c[2] = *src++;
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t.c[1] = *src++;
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t.c[0] = *src++;
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*dst++ = t.i;
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t.c[3] = *src++;
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t.c[2] = *src++;
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t.c[1] = *src++;
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t.c[0] = *src++;
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*dst++ = t.i;
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}
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}
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/*
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* Names of all encryption algorithms.
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* These must match the numbers defined in cipher.h.
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*/
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static char *cipher_names[] =
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{
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"none",
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"idea",
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"des",
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"3des",
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"tss",
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"rc4",
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"blowfish",
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"reserved",
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"blowfish-cbc",
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"3des-cbc",
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"arcfour",
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"cast128-cbc"
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};
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/*
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* Returns a bit mask indicating which ciphers are supported by this
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* implementation. The bit mask has the corresponding bit set of each
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* supported cipher.
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*/
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unsigned int
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cipher_mask1()
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{
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unsigned int mask = 0;
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mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
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mask |= 1 << SSH_CIPHER_BLOWFISH;
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return mask;
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}
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unsigned int
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cipher_mask2()
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{
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unsigned int mask = 0;
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mask |= 1 << SSH_CIPHER_BLOWFISH_CBC;
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mask |= 1 << SSH_CIPHER_3DES_CBC;
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mask |= 1 << SSH_CIPHER_ARCFOUR;
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mask |= 1 << SSH_CIPHER_CAST128_CBC;
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return mask;
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}
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unsigned int
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cipher_mask()
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{
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return cipher_mask1() | cipher_mask2();
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}
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/* Returns the name of the cipher. */
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const char *
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cipher_name(int cipher)
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{
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if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
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cipher_names[cipher] == NULL)
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fatal("cipher_name: bad cipher name: %d", cipher);
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return cipher_names[cipher];
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}
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/* Returns 1 if the name of the ciphers are valid. */
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#define CIPHER_SEP ","
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int
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ciphers_valid(const char *names)
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{
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char *ciphers, *cp;
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char *p;
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int i;
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if (names == NULL || strcmp(names, "") == 0)
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return 0;
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ciphers = cp = xstrdup(names);
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for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
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(p = strsep(&cp, CIPHER_SEP))) {
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i = cipher_number(p);
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if (i == -1 || !(cipher_mask2() & (1 << i))) {
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xfree(ciphers);
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return 0;
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}
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}
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xfree(ciphers);
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return 1;
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}
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/*
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* Parses the name of the cipher. Returns the number of the corresponding
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* cipher, or -1 on error.
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*/
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int
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cipher_number(const char *name)
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{
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int i;
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if (name == NULL)
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return -1;
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for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
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if (strcmp(cipher_names[i], name) == 0 &&
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(cipher_mask() & (1 << i)))
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return i;
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return -1;
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}
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/*
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* Selects the cipher, and keys if by computing the MD5 checksum of the
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* passphrase and using the resulting 16 bytes as the key.
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*/
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void
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cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase)
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{
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MD5_CTX md;
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unsigned char digest[16];
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MD5_Init(&md);
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MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
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MD5_Final(digest, &md);
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cipher_set_key(context, cipher, digest, 16);
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memset(digest, 0, sizeof(digest));
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memset(&md, 0, sizeof(md));
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}
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/* Selects the cipher to use and sets the key. */
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void
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cipher_set_key(CipherContext *context, int cipher, const unsigned char *key,
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int keylen)
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{
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unsigned char padded[32];
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/* Set cipher type. */
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context->type = cipher;
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/* Get 32 bytes of key data. Pad if necessary. (So that code
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below does not need to worry about key size). */
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memset(padded, 0, sizeof(padded));
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memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
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/* Initialize the initialization vector. */
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switch (cipher) {
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case SSH_CIPHER_NONE:
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/*
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* Has to stay for authfile saving of private key with no
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* passphrase
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*/
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break;
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case SSH_CIPHER_3DES:
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/*
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* Note: the least significant bit of each byte of key is
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* parity, and must be ignored by the implementation. 16
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* bytes of key are used (first and last keys are the same).
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*/
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if (keylen < 16)
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error("Key length %d is insufficient for 3DES.", keylen);
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des_set_key((void *) padded, context->u.des3.key1);
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des_set_key((void *) (padded + 8), context->u.des3.key2);
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if (keylen <= 16)
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des_set_key((void *) padded, context->u.des3.key3);
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else
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des_set_key((void *) (padded + 16), context->u.des3.key3);
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memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
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memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
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break;
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case SSH_CIPHER_BLOWFISH:
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if (keylen < 16)
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error("Key length %d is insufficient for blowfish.", keylen);
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BF_set_key(&context->u.bf.key, keylen, padded);
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memset(context->u.bf.iv, 0, 8);
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break;
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case SSH_CIPHER_3DES_CBC:
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case SSH_CIPHER_BLOWFISH_CBC:
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case SSH_CIPHER_ARCFOUR:
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case SSH_CIPHER_CAST128_CBC:
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fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher));
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break;
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default:
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fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
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}
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memset(padded, 0, sizeof(padded));
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}
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void
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cipher_set_key_iv(CipherContext * context, int cipher,
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const unsigned char *key, int keylen,
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const unsigned char *iv, int ivlen)
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{
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/* Set cipher type. */
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context->type = cipher;
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/* Initialize the initialization vector. */
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switch (cipher) {
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case SSH_CIPHER_NONE:
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break;
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case SSH_CIPHER_3DES:
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case SSH_CIPHER_BLOWFISH:
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fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher));
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break;
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case SSH_CIPHER_3DES_CBC:
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if (keylen < 24)
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error("Key length %d is insufficient for 3des-cbc.", keylen);
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des_set_key((void *) key, context->u.des3.key1);
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des_set_key((void *) (key+8), context->u.des3.key2);
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des_set_key((void *) (key+16), context->u.des3.key3);
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if (ivlen < 8)
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error("IV length %d is insufficient for 3des-cbc.", ivlen);
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memcpy(context->u.des3.iv3, (char *)iv, 8);
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break;
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case SSH_CIPHER_BLOWFISH_CBC:
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if (keylen < 16)
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error("Key length %d is insufficient for blowfish.", keylen);
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if (ivlen < 8)
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error("IV length %d is insufficient for blowfish.", ivlen);
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BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key);
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memcpy(context->u.bf.iv, (char *)iv, 8);
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break;
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case SSH_CIPHER_ARCFOUR:
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if (keylen < 16)
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error("Key length %d is insufficient for arcfour.", keylen);
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RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key);
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break;
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case SSH_CIPHER_CAST128_CBC:
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if (keylen < 16)
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error("Key length %d is insufficient for cast128.", keylen);
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if (ivlen < 8)
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error("IV length %d is insufficient for cast128.", ivlen);
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CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key);
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memcpy(context->u.cast.iv, (char *)iv, 8);
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break;
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default:
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fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
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}
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}
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/* Encrypts data using the cipher. */
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void
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cipher_encrypt(CipherContext *context, unsigned char *dest,
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const unsigned char *src, unsigned int len)
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{
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if ((len & 7) != 0)
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fatal("cipher_encrypt: bad plaintext length %d", len);
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switch (context->type) {
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case SSH_CIPHER_NONE:
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memcpy(dest, src, len);
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break;
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case SSH_CIPHER_3DES:
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SSH_3CBC_ENCRYPT(context->u.des3.key1,
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context->u.des3.key2, &context->u.des3.iv2,
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context->u.des3.key3, &context->u.des3.iv3,
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dest, (unsigned char *) src, len);
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break;
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case SSH_CIPHER_BLOWFISH:
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swap_bytes(src, dest, len);
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BF_cbc_encrypt(dest, dest, len,
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&context->u.bf.key, context->u.bf.iv,
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BF_ENCRYPT);
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swap_bytes(dest, dest, len);
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break;
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case SSH_CIPHER_BLOWFISH_CBC:
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BF_cbc_encrypt((void *)src, dest, len,
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&context->u.bf.key, context->u.bf.iv,
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BF_ENCRYPT);
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break;
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case SSH_CIPHER_3DES_CBC:
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des_ede3_cbc_encrypt(src, dest, len,
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context->u.des3.key1, context->u.des3.key2,
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context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT);
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break;
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case SSH_CIPHER_ARCFOUR:
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RC4(&context->u.rc4, len, (unsigned char *)src, dest);
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break;
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case SSH_CIPHER_CAST128_CBC:
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CAST_cbc_encrypt(src, dest, len,
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&context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT);
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break;
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default:
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fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
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}
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}
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/* Decrypts data using the cipher. */
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void
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cipher_decrypt(CipherContext *context, unsigned char *dest,
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const unsigned char *src, unsigned int len)
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{
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if ((len & 7) != 0)
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fatal("cipher_decrypt: bad ciphertext length %d", len);
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switch (context->type) {
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case SSH_CIPHER_NONE:
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memcpy(dest, src, len);
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break;
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case SSH_CIPHER_3DES:
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SSH_3CBC_DECRYPT(context->u.des3.key1,
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context->u.des3.key2, &context->u.des3.iv2,
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context->u.des3.key3, &context->u.des3.iv3,
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dest, (unsigned char *) src, len);
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break;
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case SSH_CIPHER_BLOWFISH:
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swap_bytes(src, dest, len);
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BF_cbc_encrypt((void *) dest, dest, len,
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&context->u.bf.key, context->u.bf.iv,
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BF_DECRYPT);
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swap_bytes(dest, dest, len);
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break;
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case SSH_CIPHER_BLOWFISH_CBC:
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BF_cbc_encrypt((void *) src, dest, len,
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&context->u.bf.key, context->u.bf.iv,
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BF_DECRYPT);
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break;
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case SSH_CIPHER_3DES_CBC:
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des_ede3_cbc_encrypt(src, dest, len,
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context->u.des3.key1, context->u.des3.key2,
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context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT);
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break;
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case SSH_CIPHER_ARCFOUR:
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RC4(&context->u.rc4, len, (unsigned char *)src, dest);
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break;
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case SSH_CIPHER_CAST128_CBC:
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CAST_cbc_encrypt(src, dest, len,
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&context->u.cast.key, context->u.cast.iv, CAST_DECRYPT);
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break;
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default:
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fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
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}
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}
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