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vtun/lfd_encrypt.c

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/*
VTun - Virtual Tunnel over TCP/IP network.
Copyright (C) 1998-2008 Maxim Krasnyansky <max_mk@yahoo.com>
VTun has been derived from VPPP package by Maxim Krasnyansky.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
*/
/*
Encryption module uses software developed by the OpenSSL Project
for use in the OpenSSL Toolkit. (http://www.openssl.org/)
Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
*/
/*
* This lfd_encrypt module uses MD5 to create 128 bits encryption
* keys and BlowFish for actual data encryption.
* It is based on code written by Chris Todd<christ@insynq.com> with
* several improvements and modifications by me.
*/
/*
* The current lfd_encrypt module is based on code attributed above and
* uses new code written by Dale Fountain <dpf-vtun@fountainbay.com> to
* allow multiple ciphers, modes, and key sizes. Feb 2004.
*/
#include "config.h"
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <syslog.h>
#include <strings.h>
#include <string.h>
#include <time.h>
#include "vtun.h"
#include "linkfd.h"
#include "lib.h"
#ifdef HAVE_SSL
/* OpenSSL includes */
#include <openssl/evp.h>
#include <openssl/md5.h>
#include <openssl/blowfish.h>
#include <openssl/rand.h>
/*
* #define LFD_ENCRYPT_DEBUG
*/
#define ENC_BUF_SIZE VTUN_FRAME_SIZE + 128
#define ENC_KEY_SIZE 16
BF_KEY key;
char * enc_buf;
char * dec_buf;
#define CIPHER_INIT 0
#define CIPHER_CODE 1
#define CIPHER_SEQUENCE 2
#define CIPHER_REQ_INIT 3
struct vtun_host *phost;
extern int send_a_packet;
/* out of sync packet threshold before forcing a re-init */
#define MAX_GIBBERISH 10
#define MIN_GIBBERISH 1
#define MAX_GIBBERISH_TIME 2
int gibberish;
time_t gib_time_start;
int cipher_enc_state;
int cipher_dec_state;
int cipher;
int blocksize;
int keysize;
int enc_init_first_time;
int dec_init_first_time;
unsigned long sequence_num;
char * pkey;
char * iv_buf;
EVP_CIPHER_CTX ctx_enc; /* encrypt */
EVP_CIPHER_CTX ctx_dec; /* decrypt */
EVP_CIPHER_CTX ctx_enc_ecb; /* sideband ecb encrypt */
EVP_CIPHER_CTX ctx_dec_ecb; /* sideband ecb decrypt */
int prep_key(char **key, int size, struct vtun_host *host)
{
int tmplen, halflen;
char *hashkey;
if ( !(hashkey = malloc(size)) )
{
vtun_syslog(LOG_ERR,"Can't allocate buffer for key hash");
return -1;
}
memset(hashkey,0,size);
if (size == 32)
{
tmplen = strlen(host->passwd);
if (tmplen != 0) halflen = tmplen>>1;
else halflen = 0;
MD5(host->passwd, halflen, hashkey);
MD5((host->passwd)+halflen, tmplen-halflen, hashkey+16);
}
else if (size == 16)
{
MD5(host->passwd,strlen(host->passwd), hashkey);
}
else
{
/* don't know what to do */
free(hashkey);
*key = NULL;
return -1;
}
*key = hashkey;
return 0;
}
void free_key (char *key)
{
free(key);
}
int alloc_encrypt(struct vtun_host *host)
{
int sb_init = 0;
int var_key = 0;
const EVP_CIPHER *cipher_type;
char tmpstr[64];
char cipher_name[32];
EVP_CIPHER_CTX *pctx_enc;
EVP_CIPHER_CTX *pctx_dec;
enc_init_first_time = 1;
dec_init_first_time = 1;
if( !(enc_buf = lfd_alloc(ENC_BUF_SIZE)) ){
vtun_syslog(LOG_ERR,"Can't allocate buffer for encryptor");
return -1;
}
if( !(dec_buf = lfd_alloc(ENC_BUF_SIZE)) ){
vtun_syslog(LOG_ERR,"Can't allocate buffer for decryptor");
return -1;
}
RAND_bytes((char *)&sequence_num, 4);
gibberish = 0;
gib_time_start = 0;
phost = host;
cipher = host->cipher;
switch(cipher)
{
case VTUN_ENC_AES256OFB:
case VTUN_ENC_AES256CFB:
case VTUN_ENC_AES256CBC:
blocksize = 16;
keysize = 32;
sb_init = 1;
cipher_type = EVP_aes_256_ecb();
pctx_enc = &ctx_enc_ecb;
pctx_dec = &ctx_dec_ecb;
break;
case VTUN_ENC_AES256ECB:
blocksize = 16;
keysize = 32;
pctx_enc = &ctx_enc;
pctx_dec = &ctx_dec;
cipher_type = EVP_aes_256_ecb();
strcpy(cipher_name,"AES-256-ECB");
break;
case VTUN_ENC_AES128OFB:
case VTUN_ENC_AES128CFB:
case VTUN_ENC_AES128CBC:
blocksize = 16;
keysize = 16;
sb_init=1;
cipher_type = EVP_aes_128_ecb();
pctx_enc = &ctx_enc_ecb;
pctx_dec = &ctx_dec_ecb;
break;
case VTUN_ENC_AES128ECB:
blocksize = 16;
keysize = 16;
pctx_enc = &ctx_enc;
pctx_dec = &ctx_dec;
cipher_type = EVP_aes_128_ecb();
strcpy(cipher_name,"AES-128-ECB");
break;
case VTUN_ENC_BF256OFB:
case VTUN_ENC_BF256CFB:
case VTUN_ENC_BF256CBC:
blocksize = 8;
keysize = 32;
var_key = 1;
sb_init = 1;
cipher_type = EVP_bf_ecb();
pctx_enc = &ctx_enc_ecb;
pctx_dec = &ctx_dec_ecb;
break;
case VTUN_ENC_BF256ECB:
blocksize = 8;
keysize = 32;
var_key = 1;
pctx_enc = &ctx_enc;
pctx_dec = &ctx_dec;
cipher_type = EVP_bf_ecb();
strcpy(cipher_name,"Blowfish-256-ECB");
break;
case VTUN_ENC_BF128OFB:
case VTUN_ENC_BF128CFB:
case VTUN_ENC_BF128CBC:
blocksize = 8;
keysize = 16;
var_key = 1;
sb_init = 1;
cipher_type = EVP_bf_ecb();
pctx_enc = &ctx_enc_ecb;
pctx_dec = &ctx_dec_ecb;
break;
case VTUN_ENC_BF128ECB: /* blowfish 128 ecb is the default */
default:
blocksize = 8;
keysize = 16;
var_key = 1;
pctx_enc = &ctx_enc;
pctx_dec = &ctx_dec;
cipher_type = EVP_bf_ecb();
strcpy(cipher_name,"Blowfish-128-ECB");
break;
} /* switch(host->cipher) */
if (prep_key(&pkey, keysize, host) != 0) return -1;
EVP_CIPHER_CTX_init(pctx_enc);
EVP_CIPHER_CTX_init(pctx_dec);
EVP_EncryptInit_ex(pctx_enc, cipher_type, NULL, NULL, NULL);
EVP_DecryptInit_ex(pctx_dec, cipher_type, NULL, NULL, NULL);
if (var_key)
{
EVP_CIPHER_CTX_set_key_length(pctx_enc, keysize);
EVP_CIPHER_CTX_set_key_length(pctx_dec, keysize);
}
EVP_EncryptInit_ex(pctx_enc, NULL, NULL, pkey, NULL);
EVP_DecryptInit_ex(pctx_dec, NULL, NULL, pkey, NULL);
EVP_CIPHER_CTX_set_padding(pctx_enc, 0);
EVP_CIPHER_CTX_set_padding(pctx_dec, 0);
if (sb_init)
{
cipher_enc_state=CIPHER_INIT;
cipher_dec_state=CIPHER_INIT;
}
else
{
cipher_enc_state=CIPHER_CODE;
cipher_dec_state=CIPHER_CODE;
sprintf(tmpstr,"%s encryption initialized", cipher_name);
vtun_syslog(LOG_INFO, tmpstr);
}
return 0;
}
int free_encrypt()
{
free_key(pkey); pkey = NULL;
lfd_free(enc_buf); enc_buf = NULL;
lfd_free(dec_buf); dec_buf = NULL;
EVP_CIPHER_CTX_cleanup(&ctx_enc);
EVP_CIPHER_CTX_cleanup(&ctx_dec);
EVP_CIPHER_CTX_cleanup(&ctx_enc_ecb);
EVP_CIPHER_CTX_cleanup(&ctx_dec_ecb);
return 0;
}
int encrypt_buf(int len, char *in, char **out)
{
register int pad, p, msg_len;
int outlen;
char *in_ptr, *out_ptr = enc_buf;
msg_len = send_msg(len, in, out);
in = *out;
in_ptr = in+msg_len;
memcpy(out_ptr,in,msg_len);
out_ptr += msg_len;
send_ib_mesg(&len, &in_ptr);
if (!len) return 0;
/* ( len % blocksize ) */
p = (len & (blocksize-1)); pad = blocksize - p;
memset(in_ptr+len, pad, pad);
outlen=len+pad;
if (pad == blocksize)
RAND_bytes(in_ptr+len, blocksize-1);
EVP_EncryptUpdate(&ctx_enc, out_ptr, &outlen, in_ptr, len+pad);
*out = enc_buf;
sequence_num++;
return outlen+msg_len;
}
int decrypt_buf(int len, char *in, char **out)
{
register int pad;
char *tmp_ptr, *in_ptr, *out_ptr = dec_buf;
int outlen;
len = recv_msg(len, in, out);
in = *out;
in_ptr = in;
outlen=len;
if (!len) return 0;
EVP_DecryptUpdate(&ctx_dec, out_ptr, &outlen, in_ptr, len);
recv_ib_mesg(&outlen, &out_ptr);
if (!outlen) return 0;
tmp_ptr = out_ptr + outlen; tmp_ptr--;
pad = *tmp_ptr;
if (pad < 1 || pad > blocksize) {
vtun_syslog(LOG_INFO, "decrypt_buf: bad pad length");
return 0;
}
*out = out_ptr;
return outlen - pad;
}
int cipher_enc_init(char * iv)
{
int var_key = 0;
const EVP_CIPHER *cipher_type;
char tmpstr[64];
char cipher_name[32];
switch(cipher)
{
case VTUN_ENC_AES256OFB:
cipher_type = EVP_aes_256_ofb();
strcpy(cipher_name, "AES-256-OFB");
break;
case VTUN_ENC_AES256CFB:
cipher_type = EVP_aes_256_cfb();
strcpy(cipher_name, "AES-256-CFB");
break;
case VTUN_ENC_AES256CBC:
cipher_type = EVP_aes_256_cbc();
strcpy(cipher_name, "AES-256-CBC");
break;
case VTUN_ENC_AES128OFB:
cipher_type = EVP_aes_128_ofb();
strcpy(cipher_name, "AES-128-OFB");
break;
case VTUN_ENC_AES128CFB:
cipher_type = EVP_aes_128_cfb();
strcpy(cipher_name, "AES-128-CFB");
break;
case VTUN_ENC_AES128CBC:
cipher_type = EVP_aes_128_cbc();
strcpy(cipher_name, "AES-128-CBC");
break;
case VTUN_ENC_BF256OFB:
var_key = 1;
cipher_type = EVP_bf_ofb();
strcpy(cipher_name, "Blowfish-256-OFB");
break;
case VTUN_ENC_BF256CFB:
var_key = 1;
cipher_type = EVP_bf_cfb();
strcpy(cipher_name, "Blowfish-256-CFB");
break;
case VTUN_ENC_BF256CBC:
var_key = 1;
cipher_type = EVP_bf_cbc();
strcpy(cipher_name, "Blowfish-256-CBC");
break;
case VTUN_ENC_BF128OFB:
var_key = 1;
cipher_type = EVP_bf_ofb();
strcpy(cipher_name, "Blowfish-128-OFB");
break;
case VTUN_ENC_BF128CFB:
var_key = 1;
cipher_type = EVP_bf_cfb();
strcpy(cipher_name, "Blowfish-128-CFB");
break;
case VTUN_ENC_BF128CBC:
var_key = 1;
cipher_type = EVP_bf_cbc();
strcpy(cipher_name, "Blowfish-128-CBC");
break;
default:
/* if we're here, something weird's going on */
return -1;
break;
} /* switch(cipher) */
EVP_CIPHER_CTX_init(&ctx_enc);
EVP_EncryptInit_ex(&ctx_enc, cipher_type, NULL, NULL, NULL);
if (var_key)
EVP_CIPHER_CTX_set_key_length(&ctx_enc, keysize);
EVP_EncryptInit_ex(&ctx_enc, NULL, NULL, pkey, NULL);
EVP_EncryptInit_ex(&ctx_enc, NULL, NULL, NULL, iv);
EVP_CIPHER_CTX_set_padding(&ctx_enc, 0);
if (enc_init_first_time)
{
sprintf(tmpstr,"%s encryption initialized", cipher_name);
vtun_syslog(LOG_INFO, tmpstr);
enc_init_first_time = 0;
}
return 0;
}
int cipher_dec_init(char * iv)
{
int var_key = 0;
const EVP_CIPHER *cipher_type;
char tmpstr[64];
char cipher_name[32];
switch(cipher)
{
case VTUN_ENC_AES256OFB:
cipher_type = EVP_aes_256_ofb();
strcpy(cipher_name, "AES-256-OFB");
break;
case VTUN_ENC_AES256CFB:
cipher_type = EVP_aes_256_cfb();
strcpy(cipher_name, "AES-256-CFB");
break;
case VTUN_ENC_AES256CBC:
cipher_type = EVP_aes_256_cbc();
strcpy(cipher_name, "AES-256-CBC");
break;
case VTUN_ENC_AES128OFB:
cipher_type = EVP_aes_128_ofb();
strcpy(cipher_name, "AES-128-OFB");
break;
case VTUN_ENC_AES128CFB:
cipher_type = EVP_aes_128_cfb();
strcpy(cipher_name, "AES-128-CFB");
break;
case VTUN_ENC_AES128CBC:
cipher_type = EVP_aes_128_cbc();
strcpy(cipher_name, "AES-128-CBC");
break;
case VTUN_ENC_BF256OFB:
var_key = 1;
cipher_type = EVP_bf_ofb();
strcpy(cipher_name, "Blowfish-256-OFB");
break;
case VTUN_ENC_BF256CFB:
var_key = 1;
cipher_type = EVP_bf_cfb();
strcpy(cipher_name, "Blowfish-256-CFB");
break;
case VTUN_ENC_BF256CBC:
var_key = 1;
cipher_type = EVP_bf_cbc();
strcpy(cipher_name, "Blowfish-256-CBC");
break;
case VTUN_ENC_BF128OFB:
var_key = 1;
cipher_type = EVP_bf_ofb();
strcpy(cipher_name, "Blowfish-128-OFB");
break;
case VTUN_ENC_BF128CFB:
var_key = 1;
cipher_type = EVP_bf_cfb();
strcpy(cipher_name, "Blowfish-128-CFB");
break;
case VTUN_ENC_BF128CBC:
var_key = 1;
cipher_type = EVP_bf_cbc();
strcpy(cipher_name, "Blowfish-128-CBC");
break;
default:
/* if we're here, something weird's going on */
return -1;
break;
} /* switch(cipher) */
EVP_CIPHER_CTX_init(&ctx_dec);
EVP_DecryptInit_ex(&ctx_dec, cipher_type, NULL, NULL, NULL);
if (var_key)
EVP_CIPHER_CTX_set_key_length(&ctx_dec, keysize);
EVP_DecryptInit_ex(&ctx_dec, NULL, NULL, pkey, NULL);
EVP_DecryptInit_ex(&ctx_dec, NULL, NULL, NULL, iv);
EVP_CIPHER_CTX_set_padding(&ctx_dec, 0);
if (dec_init_first_time)
{
sprintf(tmpstr,"%s decryption initialized", cipher_name);
vtun_syslog(LOG_INFO, tmpstr);
dec_init_first_time = 0;
}
return 0;
}
int send_msg(int len, char *in, char **out)
{
char * iv; char * in_ptr;
int outlen;
switch(cipher_enc_state)
{
case CIPHER_INIT:
in_ptr = in - blocksize*2;
iv = malloc(blocksize);
RAND_bytes(iv, blocksize);
strncpy(in_ptr,"ivec",4);
in_ptr += 4;
memcpy(in_ptr,iv,blocksize);
in_ptr += blocksize;
cipher_enc_init(iv);
memset(iv,0,blocksize); free(iv); iv = NULL;
RAND_bytes(in_ptr, in - in_ptr);
in_ptr = in - blocksize*2;
outlen = blocksize*2;
EVP_EncryptUpdate(&ctx_enc_ecb, in_ptr,
&outlen, in_ptr, blocksize*2);
*out = in_ptr;
len = outlen;
cipher_enc_state = CIPHER_SEQUENCE;
break;
case CIPHER_CODE:
default:
*out = in;
len = 0;
break;
}
return len;
}
int recv_msg(int len, char *in, char **out)
{
char * iv; char * in_ptr;
int outlen;
switch(cipher_dec_state)
{
case CIPHER_INIT:
in_ptr = in;
iv = malloc(blocksize);
outlen = blocksize*2;
EVP_DecryptUpdate(&ctx_dec_ecb, in_ptr, &outlen, in_ptr, blocksize*2);
if ( !strncmp(in_ptr, "ivec", 4) )
{
memcpy(iv, in_ptr+4, blocksize);
cipher_dec_init(iv);
*out = in_ptr + blocksize*2;
len -= blocksize*2;
cipher_dec_state = CIPHER_SEQUENCE;
gibberish = 0;
gib_time_start = 0;
}
else
{
len = 0;
*out = in;
gibberish++;
if (gibberish == 1) gib_time_start = time(NULL);
if (gibberish == MIN_GIBBERISH)
{
cipher_enc_state = CIPHER_REQ_INIT;
send_a_packet = 1;
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO,
"Min. gibberish threshold reached");
#endif
}
if (gibberish >= MAX_GIBBERISH ||
difftime(time(NULL), gib_time_start) >= MAX_GIBBERISH_TIME)
{
gibberish = 0;
gib_time_start = 0;
send_a_packet = 1;
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO,
"Max. gibberish threshold reached");
#endif
if (cipher_enc_state != CIPHER_INIT)
{
cipher_enc_state = CIPHER_INIT;
EVP_CIPHER_CTX_cleanup(&ctx_enc);
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO,
"Forcing local encryptor re-init");
#endif
}
}
}
memset(iv,0,blocksize); free(iv); iv = NULL;
memset(in_ptr,0,blocksize*2);
break;
case CIPHER_CODE:
default:
*out = in;
break;
}
return len;
}
/* Send In-Band Message */
int send_ib_mesg(int *len, char **in)
{
char *in_ptr = *in;
/* To simplify matters, I assume that blocksize
will not be less than 8 bytes */
if (cipher_enc_state == CIPHER_SEQUENCE)
{
in_ptr -= blocksize;
memset(in_ptr,0,blocksize);
strncpy(in_ptr,"seq#",4);
in_ptr+=4;
*((unsigned long *)in_ptr) = htonl(sequence_num);
in_ptr-=4;
*in = in_ptr;
*len += blocksize;
}
else if (cipher_enc_state == CIPHER_REQ_INIT)
{
in_ptr -= blocksize;
memset(in_ptr,0,blocksize);
strncpy(in_ptr,"rsyn",4);
in_ptr+=4;
*((unsigned long *)in_ptr) = htonl(sequence_num);
in_ptr-=4;
*in = in_ptr;
*len += blocksize;
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO, "Requesting remote encryptor re-init");
#endif
cipher_enc_state = CIPHER_SEQUENCE;
send_a_packet = 1;
}
return 0;
}
/* Receive In-Band Message */
int recv_ib_mesg(int *len, char **in)
{
char *in_ptr = *in;
if (cipher_dec_state == CIPHER_SEQUENCE)
{
/* To simplify matters, I assume that blocksize
will not be less than 8 bytes */
if ( !strncmp(in_ptr, "seq#", 4) )
{
*in += blocksize;
*len -= blocksize;
}
else if ( !strncmp(in_ptr, "rsyn", 4) )
{
*in += blocksize;
*len -= blocksize;
if (cipher_enc_state != CIPHER_INIT)
{
cipher_enc_state = CIPHER_INIT;
EVP_CIPHER_CTX_cleanup(&ctx_enc);
}
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO, "Remote requests encryptor re-init");
#endif
}
else
{
*len = 0;
if (cipher_dec_state != CIPHER_INIT &&
cipher_enc_state != CIPHER_REQ_INIT &&
cipher_enc_state != CIPHER_INIT)
{
EVP_CIPHER_CTX_cleanup (&ctx_dec);
cipher_dec_state = CIPHER_INIT;
cipher_enc_state = CIPHER_REQ_INIT;
}
#ifdef LFD_ENCRYPT_DEBUG
vtun_syslog(LOG_INFO, "Local decryptor out of sync");
#endif
}
}
return 0;
}
/*
* Module structure.
*/
struct lfd_mod lfd_encrypt = {
"Encryptor",
alloc_encrypt,
encrypt_buf,
NULL,
decrypt_buf,
NULL,
free_encrypt,
NULL,
NULL
};
#else /* HAVE_SSL */
int no_encrypt(struct vtun_host *host)
{
vtun_syslog(LOG_INFO, "Encryption is not supported");
return -1;
}
struct lfd_mod lfd_encrypt = {
"Encryptor",
no_encrypt, NULL, NULL, NULL, NULL, NULL, NULL, NULL
};
#endif /* HAVE_SSL */
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