- djm@cvs.openbsd.org 2006/07/10 12:03:20

[openssh-git.git] / cipher.c

/* $OpenBSD: cipher.c,v 1.79 2006/03/25 13:17:01 djm 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 "xmalloc.h"
#include "log.h"
#include "cipher.h"

#include <openssl/md5.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;
        const EVP_CIPHER        *(*evptype)(void);
} ciphers[] = {
        { "none",               SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null },
        { "des",                SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc },
        { "3des",               SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des },
        { "blowfish",           SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf },

        { "3des-cbc",           SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc },
        { "blowfish-cbc",       SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc },
        { "cast128-cbc",        SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc },
        { "arcfour",            SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 },
        { "arcfour128",         SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 },
        { "arcfour256",         SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 },
        { "aes128-cbc",         SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc },
        { "aes192-cbc",         SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc },
        { "aes256-cbc",         SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
        { "rijndael-cbc@lysator.liu.se",
                                SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
        { "aes128-ctr",         SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_128_ctr },
        { "aes192-ctr",         SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_128_ctr },
        { "aes256-ctr",         SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_128_ctr },
#ifdef USE_CIPHER_ACSS
        { "acss@openssh.org",   SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss },
#endif
        { NULL,                 SSH_CIPHER_INVALID, 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_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);
        }
}