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/*
*****************************************************************************
*
* File: cipher_funcs.c
*
* Author: Damien S. Stuart
*
* Purpose: Cipher functions used by fwknop
*
* Copyright 2009-2013 Damien Stuart (dstuart@dstuart.org)
*
* License (GNU Public License):
*
* This library 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*****************************************************************************
*/
#include <stdio.h>
#include <string.h>
#ifdef WIN32
#include <sys/timeb.h>
#include <time.h>
#include <stdlib.h>
#else
#include <sys/time.h>
#endif
#include "fko_common.h"
#include "cipher_funcs.h"
#include "digest.h"
#ifndef WIN32
#ifndef RAND_FILE
#define RAND_FILE "/dev/urandom"
#endif
#endif
/* Get random data.
*/
void
get_random_data(unsigned char *data, const size_t len)
{
uint32_t i;
#ifdef WIN32
int rnum;
struct _timeb tb;
_ftime_s(&tb);
srand((uint32_t)(tb.time*1000)+tb.millitm);
for(i=0; i<len; i++)
{
rnum = rand();
*(data+i) = rnum % 0xff;
}
#else
FILE *rfd;
struct timeval tv;
int do_time = 0;
size_t amt_read;
/* Attempt to read seed data from /dev/urandom. If that does not
* work, then fall back to a time-based method (less secure, but
* probably more portable).
*/
if((rfd = fopen(RAND_FILE, "r")) == NULL)
{
do_time = 1;
}
else
{
/* Read seed from /dev/urandom
*/
amt_read = fread(data, len, 1, rfd);
fclose(rfd);
if (amt_read != 1)
do_time = 1;
}
if (do_time)
{
/* Seed based on time (current usecs).
*/
gettimeofday(&tv, NULL);
srand(tv.tv_usec);
for(i=0; i<len; i++)
*(data+i) = rand() % 0xff;
}
#endif
}
/*** These are Rijndael-specific functions ***/
/* Rijndael function to generate initial salt and initialization vector
* (iv). This is is done to be compatible with the data produced via OpenSSL
*/
static void
rij_salt_and_iv(RIJNDAEL_context *ctx, const char *key,
const int key_len, const unsigned char *data, const int mode_flag)
{
char pw_buf[RIJNDAEL_MAX_KEYSIZE] = {0};
unsigned char tmp_buf[MD5_DIGEST_LEN+RIJNDAEL_MAX_KEYSIZE+RIJNDAEL_BLOCKSIZE] = {0};
unsigned char kiv_buf[RIJNDAEL_MAX_KEYSIZE+RIJNDAEL_BLOCKSIZE] = {0}; /* Key and IV buffer */
unsigned char md5_buf[MD5_DIGEST_LEN] = {0}; /* Buffer for computed md5 hash */
int final_key_len = 0;
size_t kiv_len = 0;
if(mode_flag == FKO_ENC_MODE_CBC_LEGACY_IV)
{
/* Pad the pw with '0' chars up to the minimum Rijndael key size.
*
* This maintains compatibility with the old perl code if absolutely
* necessary in some scenarios, but is not recommended to use since it
* breaks compatibility with how OpenSSL implements AES and introduces
* other problems. This code will be removed altogether in a future
* version of fwknop.
*/
if(key_len < RIJNDAEL_MIN_KEYSIZE)
{
memcpy(pw_buf, key, key_len);
memset(pw_buf+key_len, '0', RIJNDAEL_MIN_KEYSIZE - key_len);
final_key_len = RIJNDAEL_MIN_KEYSIZE;
}
else
{
memcpy(pw_buf, key, key_len);
final_key_len = key_len;
}
}
else
{
memcpy(pw_buf, key, key_len);
final_key_len = key_len;
}
/* If we are decrypting, data will contain the salt. Otherwise,
* for encryption, we generate a random salt.
*/
if(data != NULL)
{
/* Pull the salt from the data
*/
memcpy(ctx->salt, (data+SALT_LEN), SALT_LEN);
}
else
{
/* Generate a random 8-byte salt.
*/
get_random_data(ctx->salt, SALT_LEN);
}
/* Now generate the key and initialization vector.
* (again it is the perl Crypt::CBC way, with a touch of
* fwknop).
*/
memcpy(tmp_buf+MD5_DIGEST_LEN, pw_buf, final_key_len);
memcpy(tmp_buf+MD5_DIGEST_LEN+final_key_len, ctx->salt, SALT_LEN);
while(kiv_len < sizeof(kiv_buf))
{
if(kiv_len == 0)
md5(md5_buf, tmp_buf+MD5_DIGEST_LEN, final_key_len+SALT_LEN);
else
md5(md5_buf, tmp_buf, MD5_DIGEST_LEN+final_key_len+SALT_LEN);
memcpy(tmp_buf, md5_buf, MD5_DIGEST_LEN);
memcpy(kiv_buf + kiv_len, md5_buf, MD5_DIGEST_LEN);
kiv_len += MD5_DIGEST_LEN;
}
memcpy(ctx->key, kiv_buf, RIJNDAEL_MAX_KEYSIZE);
memcpy(ctx->iv, kiv_buf+RIJNDAEL_MAX_KEYSIZE, RIJNDAEL_BLOCKSIZE);
}
/* Initialization entry point.
*/
static void
rijndael_init(RIJNDAEL_context *ctx, const char *key,
const int key_len, const unsigned char *data,
int encryption_mode)
{
/* The default is Rijndael in CBC mode
*/
if(encryption_mode == FKO_ENC_MODE_CBC
|| encryption_mode == FKO_ENC_MODE_CBC_LEGACY_IV)
ctx->mode = MODE_CBC;
else if(encryption_mode == FKO_ENC_MODE_CTR)
ctx->mode = MODE_CTR;
else if(encryption_mode == FKO_ENC_MODE_PCBC)
ctx->mode = MODE_PCBC;
else if(encryption_mode == FKO_ENC_MODE_OFB)
ctx->mode = MODE_OFB;
else if(encryption_mode == FKO_ENC_MODE_CFB)
ctx->mode = MODE_CFB;
else if(encryption_mode == FKO_ENC_MODE_ECB)
ctx->mode = MODE_ECB;
else /* shouldn't get this far */
ctx->mode = encryption_mode;
/* Generate the salt and initialization vector.
*/
rij_salt_and_iv(ctx, key, key_len, data, encryption_mode);
/* Intialize our Rijndael context.
*/
rijndael_setup(ctx, RIJNDAEL_MAX_KEYSIZE, ctx->key);
}
/* Take a chunk of data, encrypt it in the same way OpenSSL would
* (with a default of AES in CBC mode).
*/
size_t
rij_encrypt(unsigned char *in, size_t in_len,
const char *key, const int key_len,
unsigned char *out, int encryption_mode)
{
RIJNDAEL_context ctx;
int i, pad_val;
unsigned char *ondx = out;
rijndael_init(&ctx, key, key_len, NULL, encryption_mode);
/* Prepend the salt to the ciphertext...
*/
memcpy(ondx, "Salted__", SALT_LEN);
ondx+=SALT_LEN;
memcpy(ondx, ctx.salt, SALT_LEN);
ondx+=SALT_LEN;
/* Add padding to the original plaintext to ensure that it is a
* multiple of the Rijndael block size
*/
pad_val = RIJNDAEL_BLOCKSIZE - (in_len % RIJNDAEL_BLOCKSIZE);
for (i = (int)in_len; i < ((int)in_len+pad_val); i++)
in[i] = pad_val;
block_encrypt(&ctx, in, in_len+pad_val, ondx, ctx.iv);
ondx += in_len+pad_val;
return(ondx - out);
}
/* Decrypt the given data.
*/
size_t
rij_decrypt(unsigned char *in, size_t in_len,
const char *key, const int key_len,
unsigned char *out, int encryption_mode)
{
RIJNDAEL_context ctx;
int i, pad_val, pad_err = 0;
unsigned char *pad_s;
unsigned char *ondx = out;
rijndael_init(&ctx, key, key_len, in, encryption_mode);
/* Remove the first block since it contains the salt (it was consumed
* by the rijndael_init() function above).
*/
in_len -= RIJNDAEL_BLOCKSIZE;
memmove(in, in+RIJNDAEL_BLOCKSIZE, in_len);
block_decrypt(&ctx, in, in_len, out, ctx.iv);
ondx += in_len;
/* Find and remove padding.
*/
pad_val = *(ondx-1);
if(pad_val >= 0 && pad_val <= RIJNDAEL_BLOCKSIZE)
{
pad_s = ondx - pad_val;
for(i=0; i < (ondx-pad_s); i++)
{
if(*(pad_s+i) != pad_val)
pad_err++;
}
if(pad_err == 0)
ondx -= pad_val;
}
*ondx = '\0';
return(ondx - out);
}
/* See if we need to add the "Salted__" string to the front of the
* encrypted data.
*/
int
add_salted_str(fko_ctx_t ctx)
{
char *tbuf;
if(constant_runtime_cmp(ctx->encrypted_msg,
B64_RIJNDAEL_SALT, B64_RIJNDAEL_SALT_STR_LEN) != 0)
{
/* We need to realloc space for the salt.
*/
tbuf = realloc(ctx->encrypted_msg, ctx->encrypted_msg_len
+ B64_RIJNDAEL_SALT_STR_LEN+1);
if(tbuf == NULL)
return(FKO_ERROR_MEMORY_ALLOCATION);
memmove(tbuf+B64_RIJNDAEL_SALT_STR_LEN, tbuf, ctx->encrypted_msg_len);
ctx->encrypted_msg = memcpy(tbuf,
B64_RIJNDAEL_SALT, B64_RIJNDAEL_SALT_STR_LEN);
/* Adjust the encoded msg len for added SALT value and Make sure we
* are still a properly NULL-terminated string (Ubuntu was one system
* for which this was an issue).
*/
ctx->encrypted_msg_len += B64_RIJNDAEL_SALT_STR_LEN;
tbuf[ctx->encrypted_msg_len] = '\0';
ctx->added_salted_str = 1;
}
return(FKO_SUCCESS);
}
/* See if we need to add the "hQ" string to the front of the
* encrypted data.
*/
int
add_gpg_prefix(fko_ctx_t ctx)
{
char *tbuf;
if(constant_runtime_cmp(ctx->encrypted_msg,
B64_GPG_PREFIX, B64_GPG_PREFIX_STR_LEN) != 0)
{
/* We need to realloc space for the prefix.
*/
tbuf = realloc(ctx->encrypted_msg, ctx->encrypted_msg_len
+ B64_GPG_PREFIX_STR_LEN+1);
if(tbuf == NULL)
return(FKO_ERROR_MEMORY_ALLOCATION);
memmove(tbuf+B64_GPG_PREFIX_STR_LEN, tbuf, ctx->encrypted_msg_len);
ctx->encrypted_msg = memcpy(tbuf,
B64_GPG_PREFIX, B64_GPG_PREFIX_STR_LEN);
/* Adjust the encoded msg len for added SALT value and Make sure we
* are still a properly NULL-terminated string (Ubuntu was one system
* for which this was an issue).
*/
ctx->encrypted_msg_len += B64_GPG_PREFIX_STR_LEN;
tbuf[ctx->encrypted_msg_len] = '\0';
ctx->added_gpg_prefix = 1;
}
return(FKO_SUCCESS);
}
/***EOF***/
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