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gnupg/cipher/cipher.c

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/* cipher.c - cipher dispatcher
* Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG 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.
*
* GnuPG 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include "util.h"
#include "errors.h"
#include "cipher.h"
#include "algorithms.h"
/* We have support for a DUMMY encryption cipher which comes handy to
debug MDCs and similar things. Because this is a bit dangerous it
is not enabled. */
/*#define ALLOW_DUMMY 1 */
#define MAX_BLOCKSIZE 16
#define TABLE_SIZE 14
struct cipher_table_s {
const char *name;
int algo;
size_t blocksize;
size_t keylen;
size_t contextsize; /* allocate this amount of context */
int (*setkey)( void *c, const byte *key, unsigned keylen );
void (*encrypt)( void *c, byte *outbuf, const byte *inbuf );
void (*decrypt)( void *c, byte *outbuf, const byte *inbuf );
};
static struct cipher_table_s cipher_table[TABLE_SIZE];
static int disabled_algos[TABLE_SIZE];
struct cipher_handle_s {
int algo;
int mode;
size_t blocksize;
byte iv[MAX_BLOCKSIZE]; /* (this should be ulong aligned) */
byte lastiv[MAX_BLOCKSIZE];
int unused; /* in IV */
int (*setkey)( void *c, const byte *key, unsigned keylen );
void (*encrypt)( void *c, byte *outbuf, const byte *inbuf );
void (*decrypt)( void *c, byte *outbuf, const byte *inbuf );
PROPERLY_ALIGNED_TYPE context;
};
#ifdef ALLOW_DUMMY
static int
dummy_setkey( void *c, byte *key, unsigned keylen ) { return 0; }
static void
dummy_encrypt_block( void *c, byte *outbuf, byte *inbuf ) { BUG(); }
static void
dummy_decrypt_block( void *c, byte *outbuf, byte *inbuf ) { BUG(); }
#ifdef __GNUC__
# warning DUMMY cipher module is enabled
#endif
#endif
/****************
* Put the static entries into the table.
*/
static void
setup_cipher_table(void)
{
int i=0;
#ifdef USE_AES
cipher_table[i].algo = CIPHER_ALGO_AES;
cipher_table[i].name = rijndael_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
cipher_table[i].algo = CIPHER_ALGO_AES192;
cipher_table[i].name = rijndael_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
cipher_table[i].algo = CIPHER_ALGO_AES256;
cipher_table[i].name = rijndael_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
#endif
#ifdef USE_TWOFISH
cipher_table[i].algo = CIPHER_ALGO_TWOFISH;
cipher_table[i].name = twofish_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
#endif
#ifdef USE_BLOWFISH
cipher_table[i].algo = CIPHER_ALGO_BLOWFISH;
cipher_table[i].name = blowfish_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
#endif
#ifdef USE_CAST5
cipher_table[i].algo = CIPHER_ALGO_CAST5;
cipher_table[i].name = cast5_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
#endif
cipher_table[i].algo = CIPHER_ALGO_3DES;
cipher_table[i].name = des_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if( !cipher_table[i].name )
BUG();
i++;
#ifdef USE_IDEA
cipher_table[i].algo = CIPHER_ALGO_IDEA;
cipher_table[i].name = idea_get_info( cipher_table[i].algo,
&cipher_table[i].keylen,
&cipher_table[i].blocksize,
&cipher_table[i].contextsize,
&cipher_table[i].setkey,
&cipher_table[i].encrypt,
&cipher_table[i].decrypt );
if (cipher_table[i].name)
i++; /* Note that the loadable IDEA module may not be
available. */
#endif
#ifdef ALLOW_DUMMY
cipher_table[i].algo = CIPHER_ALGO_DUMMY;
cipher_table[i].name = "DUMMY";
cipher_table[i].blocksize = 8;
cipher_table[i].keylen = 128;
cipher_table[i].contextsize = 0;
cipher_table[i].setkey = dummy_setkey;
cipher_table[i].encrypt = dummy_encrypt_block;
cipher_table[i].decrypt = dummy_decrypt_block;
i++;
#endif
for( ; i < TABLE_SIZE; i++ )
cipher_table[i].name = NULL;
}
/****************
* Try to load all modules and return true if new modules are available
*/
static int
load_cipher_modules(void)
{
static int initialized = 0;
if (!initialized )
{
setup_cipher_table(); /* load static modules on the first call */
initialized = 1;
return 1;
}
return 0;
}
/****************
* Map a string to the cipher algo
*/
int
string_to_cipher_algo( const char *string )
{
int i;
const char *s;
/* kludge to alias RIJNDAEL to AES */
if ( *string == 'R' || *string == 'r')
{
if (!ascii_strcasecmp (string, "RIJNDAEL"))
string = "AES";
else if (!ascii_strcasecmp (string, "RIJNDAEL192"))
string = "AES192";
else if (!ascii_strcasecmp (string, "RIJNDAEL256"))
string = "AES256";
}
do
{
for(i=0; (s=cipher_table[i].name); i++ )
{
if( !ascii_strcasecmp( s, string ) )
return cipher_table[i].algo;
}
} while( load_cipher_modules() );
/* Didn't find it, so try the Sx format */
if(string[0]=='S' || string[0]=='s')
{
long val;
char *endptr;
string++;
val=strtol(string,&endptr,10);
if(*string!='\0' && *endptr=='\0' && check_cipher_algo(val)==0)
return val;
}
return 0;
}
/****************
* Map a cipher algo to a string
*/
const char *
cipher_algo_to_string( int algo )
{
int i;
do {
for(i=0; cipher_table[i].name; i++ )
if( cipher_table[i].algo == algo )
return cipher_table[i].name;
} while( load_cipher_modules() );
return NULL;
}
void
disable_cipher_algo( int algo )
{
int i;
for(i=0; i < DIM(disabled_algos); i++ ) {
if( !disabled_algos[i] || disabled_algos[i] == algo ) {
disabled_algos[i] = algo;
return;
}
}
/* fixme: we should use a linked list */
log_fatal("can't disable cipher algo %d: table full\n", algo );
}
/****************
* Return 0 if the cipher algo is available
*/
int
check_cipher_algo( int algo )
{
int i;
do {
for(i=0; cipher_table[i].name; i++ )
if( cipher_table[i].algo == algo ) {
for(i=0; i < DIM(disabled_algos); i++ ) {
if( disabled_algos[i] == algo )
return G10ERR_CIPHER_ALGO;
}
return 0; /* okay */
}
} while( load_cipher_modules() );
return G10ERR_CIPHER_ALGO;
}
unsigned
cipher_get_keylen( int algo )
{
int i;
unsigned len = 0;
do {
for(i=0; cipher_table[i].name; i++ ) {
if( cipher_table[i].algo == algo ) {
len = cipher_table[i].keylen;
if( !len )
log_bug("cipher %d w/o key length\n", algo );
return len;
}
}
} while( load_cipher_modules() );
log_bug("cipher %d not found\n", algo );
return 0;
}
unsigned
cipher_get_blocksize( int algo )
{
int i;
unsigned len = 0;
do {
for(i=0; cipher_table[i].name; i++ ) {
if( cipher_table[i].algo == algo ) {
len = cipher_table[i].blocksize;
if( !len )
log_bug("cipher %d w/o blocksize\n", algo );
return len;
}
}
} while( load_cipher_modules() );
log_bug("cipher %d not found\n", algo );
return 0;
}
/****************
* Open a cipher handle for use with algorithm ALGO, in mode MODE
* and put it into secure memory if SECURE is true.
*/
CIPHER_HANDLE
cipher_open( int algo, int mode, int secure )
{
CIPHER_HANDLE hd;
int i;
fast_random_poll();
do {
for(i=0; cipher_table[i].name; i++ )
if( cipher_table[i].algo == algo )
break;
} while( !cipher_table[i].name && load_cipher_modules() );
if( !cipher_table[i].name ) {
log_fatal("cipher_open: algorithm %d not available\n", algo );
return NULL;
}
/* ? perform selftest here and mark this with a flag in cipher_table ? */
hd = secure ? xmalloc_secure_clear( sizeof *hd
+ cipher_table[i].contextsize
- sizeof(PROPERLY_ALIGNED_TYPE) )
: xmalloc_clear( sizeof *hd + cipher_table[i].contextsize
- sizeof(PROPERLY_ALIGNED_TYPE) );
hd->algo = algo;
hd->blocksize = cipher_table[i].blocksize;
hd->setkey = cipher_table[i].setkey;
hd->encrypt = cipher_table[i].encrypt;
hd->decrypt = cipher_table[i].decrypt;
if( mode == CIPHER_MODE_AUTO_CFB ) {
if( algo >= 100 )
hd->mode = CIPHER_MODE_CFB;
else
hd->mode = CIPHER_MODE_PHILS_CFB;
}
else
hd->mode = mode;
#ifdef ALLOW_DUMMY
if( algo == CIPHER_ALGO_DUMMY )
hd->mode = CIPHER_MODE_DUMMY;
#endif
return hd;
}
void
cipher_close( CIPHER_HANDLE c )
{
xfree(c);
}
int
cipher_setkey( CIPHER_HANDLE c, byte *key, unsigned keylen )
{
return (*c->setkey)( &c->context.c, key, keylen );
}
void
cipher_setiv( CIPHER_HANDLE c, const byte *iv, unsigned ivlen )
{
memset( c->iv, 0, c->blocksize );
if( iv ) {
if( ivlen != c->blocksize )
log_info("WARNING: cipher_setiv: ivlen=%u blklen=%u\n",
ivlen, (unsigned)c->blocksize );
if( ivlen > c->blocksize )
ivlen = c->blocksize;
memcpy( c->iv, iv, ivlen );
}
c->unused = 0;
}
static void
do_ecb_encrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nblocks )
{
unsigned n;
for(n=0; n < nblocks; n++ ) {
(*c->encrypt)( &c->context.c, outbuf, inbuf );
inbuf += c->blocksize;
outbuf += c->blocksize;
}
}
static void
do_ecb_decrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nblocks )
{
unsigned n;
for(n=0; n < nblocks; n++ ) {
(*c->decrypt)( &c->context.c, outbuf, inbuf );
inbuf += c->blocksize;
outbuf += c->blocksize;
}
}
static void
do_cbc_encrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nblocks )
{
unsigned int n;
byte *ivp;
int i;
size_t blocksize = c->blocksize;
for(n=0; n < nblocks; n++ ) {
/* fixme: the xor should works on words and not on
* bytes. Maybe it is a good idea to enhance the cipher backend
* API to allow for CBC handling in the backend */
for(ivp=c->iv,i=0; i < blocksize; i++ )
outbuf[i] = inbuf[i] ^ *ivp++;
(*c->encrypt)( &c->context.c, outbuf, outbuf );
memcpy(c->iv, outbuf, blocksize );
inbuf += c->blocksize;
outbuf += c->blocksize;
}
}
static void
do_cbc_decrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nblocks )
{
unsigned int n;
byte *ivp;
int i;
size_t blocksize = c->blocksize;
for(n=0; n < nblocks; n++ ) {
/* because outbuf and inbuf might be the same, we have
* to save the original ciphertext block. We use lastiv
* for this here because it is not used otherwise */
memcpy(c->lastiv, inbuf, blocksize );
(*c->decrypt)( &c->context.c, outbuf, inbuf );
for(ivp=c->iv,i=0; i < blocksize; i++ )
outbuf[i] ^= *ivp++;
memcpy(c->iv, c->lastiv, blocksize );
inbuf += c->blocksize;
outbuf += c->blocksize;
}
}
static void
do_cfb_encrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nbytes )
{
byte *ivp;
size_t blocksize = c->blocksize;
if( nbytes <= c->unused ) {
/* short enough to be encoded by the remaining XOR mask */
/* XOR the input with the IV and store input into IV */
for(ivp=c->iv+c->blocksize - c->unused; nbytes; nbytes--, c->unused-- )
*outbuf++ = (*ivp++ ^= *inbuf++);
return;
}
if( c->unused ) {
/* XOR the input with the IV and store input into IV */
nbytes -= c->unused;
for(ivp=c->iv+blocksize - c->unused; c->unused; c->unused-- )
*outbuf++ = (*ivp++ ^= *inbuf++);
}
/* Now we can process complete blocks. */
#if 0
/* Experimental code. We may only use this for standard CFB
because for Phil's mode we need to save the IV of before the
last encryption - we don't want to do this in tghe fasf CFB
encryption routine. */
if (c->algo == CIPHER_ALGO_AES
&& nbytes >= blocksize
&& c->mode != CIPHER_MODE_PHILS_CFB) {
size_t n;
memcpy( c->lastiv, c->iv, blocksize );
n = (nbytes / blocksize) * blocksize;
rijndael_cfb_encrypt (&c->context.c, c->iv, outbuf, inbuf, n);
inbuf += n;
outbuf += n;
nbytes -= n;
}
#endif
while( nbytes >= blocksize ) {
int i;
/* encrypt the IV (and save the current one) */
memcpy( c->lastiv, c->iv, blocksize );
(*c->encrypt)( &c->context.c, c->iv, c->iv );
/* XOR the input with the IV and store input into IV */
for(ivp=c->iv,i=0; i < blocksize; i++ )
*outbuf++ = (*ivp++ ^= *inbuf++);
nbytes -= blocksize;
}
if( nbytes ) { /* process the remaining bytes */
/* encrypt the IV (and save the current one) */
memcpy( c->lastiv, c->iv, blocksize );
(*c->encrypt)( &c->context.c, c->iv, c->iv );
c->unused = blocksize;
/* and apply the xor */
c->unused -= nbytes;
for(ivp=c->iv; nbytes; nbytes-- )
*outbuf++ = (*ivp++ ^= *inbuf++);
}
}
static void
do_cfb_decrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nbytes )
{
byte *ivp;
ulong temp;
size_t blocksize = c->blocksize;
if( nbytes <= c->unused ) {
/* short enough to be encoded by the remaining XOR mask */
/* XOR the input with the IV and store input into IV */
for(ivp=c->iv+blocksize - c->unused; nbytes; nbytes--,c->unused--){
temp = *inbuf++;
*outbuf++ = *ivp ^ temp;
*ivp++ = temp;
}
return;
}
if( c->unused ) {
/* XOR the input with the IV and store input into IV */
nbytes -= c->unused;
for(ivp=c->iv+blocksize - c->unused; c->unused; c->unused-- ) {
temp = *inbuf++;
*outbuf++ = *ivp ^ temp;
*ivp++ = temp;
}
}
/* now we can process complete blocks */
while( nbytes >= blocksize ) {
int i;
/* encrypt the IV (and save the current one) */
memcpy( c->lastiv, c->iv, blocksize );
(*c->encrypt)( &c->context.c, c->iv, c->iv );
/* XOR the input with the IV and store input into IV */
for(ivp=c->iv,i=0; i < blocksize; i++ ) {
temp = *inbuf++;
*outbuf++ = *ivp ^ temp;
*ivp++ = temp;
}
nbytes -= blocksize;
}
if( nbytes ) { /* process the remaining bytes */
/* encrypt the IV (and save the current one) */
memcpy( c->lastiv, c->iv, blocksize );
(*c->encrypt)( &c->context.c, c->iv, c->iv );
c->unused = blocksize;
/* and apply the xor */
c->unused -= nbytes;
for(ivp=c->iv; nbytes; nbytes-- ) {
temp = *inbuf++;
*outbuf++ = *ivp ^ temp;
*ivp++ = temp;
}
}
}
/****************
* Encrypt INBUF to OUTBUF with the mode selected at open.
* inbuf and outbuf may overlap or be the same.
* Depending on the mode some some contraints apply to NBYTES.
*/
void
cipher_encrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nbytes )
{
switch( c->mode ) {
case CIPHER_MODE_ECB:
assert(!(nbytes%c->blocksize));
do_ecb_encrypt(c, outbuf, inbuf, nbytes/c->blocksize );
break;
case CIPHER_MODE_CBC:
assert(!(nbytes%c->blocksize));
do_cbc_encrypt(c, outbuf, inbuf, nbytes/c->blocksize );
break;
case CIPHER_MODE_CFB:
case CIPHER_MODE_PHILS_CFB:
do_cfb_encrypt(c, outbuf, inbuf, nbytes );
break;
#ifdef ALLOW_DUMMY
case CIPHER_MODE_DUMMY:
if( inbuf != outbuf )
memmove( outbuf, inbuf, nbytes );
break;
#endif
default: log_fatal("cipher_encrypt: invalid mode %d\n", c->mode );
}
}
/****************
* Decrypt INBUF to OUTBUF with the mode selected at open.
* inbuf and outbuf may overlap or be the same.
* Depending on the mode some some contraints apply to NBYTES.
*/
void
cipher_decrypt( CIPHER_HANDLE c, byte *outbuf, byte *inbuf, unsigned nbytes )
{
switch( c->mode ) {
case CIPHER_MODE_ECB:
assert(!(nbytes%c->blocksize));
do_ecb_decrypt(c, outbuf, inbuf, nbytes/c->blocksize );
break;
case CIPHER_MODE_CBC:
assert(!(nbytes%c->blocksize));
do_cbc_decrypt(c, outbuf, inbuf, nbytes/c->blocksize );
break;
case CIPHER_MODE_CFB:
case CIPHER_MODE_PHILS_CFB:
do_cfb_decrypt(c, outbuf, inbuf, nbytes );
break;
#ifdef ALLOW_DUMMY
case CIPHER_MODE_DUMMY:
if( inbuf != outbuf )
memmove( outbuf, inbuf, nbytes );
break;
#endif
default: log_fatal("cipher_decrypt: invalid mode %d\n", c->mode );
}
}
/****************
* Used for PGP's somewhat strange CFB mode. Only works if
* the handle is in PHILS_CFB mode
*/
void
cipher_sync( CIPHER_HANDLE c )
{
if( c->mode == CIPHER_MODE_PHILS_CFB && c->unused ) {
memmove(c->iv + c->unused, c->iv, c->blocksize - c->unused );
memcpy(c->iv, c->lastiv + c->blocksize - c->unused, c->unused);
c->unused = 0;
}
}
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