src/mcrypt/ctr.c

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This source file includes following definitions.
increase_counter
_init_mcrypt
_mcrypt_set_state
_mcrypt_get_state
_end_mcrypt
xor_stuff
_mcrypt
_mdecrypt
gf_crypt_register_ctr
/*
 * Copyright (C) 2002 Nikos Mavroyanopoulos
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Library General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <gpac/internal/crypt_dev.h>

#if !defined(GPAC_DISABLE_MCRYPT)

typedef struct ctr_buf {
        u8* enc_counter;
        u8* c_counter;
        int c_counter_pos;
        int blocksize;
} CTR_BUFFER;

/* CTR MODE */

/* This function will add one to the given number (as a u8 string).
 * has been reached.
 */
static void increase_counter( u8 *x, int x_size) {
        register int i, y=0;

        for (i=x_size-1; i>=0; i--) {
                y = 0;
                if ( x[i] == 0xff) {
                        x[i] = 0;
                        y = 1;
                } else x[i]++;

                if (y==0) break;
        }

        return;
}


/* size holds the size of the IV (counter in this mode).
 * This is the block size.
 */
GF_Err _init_mcrypt( void *buf, void *key, int lenofkey, void *IV, int size)
{
        ((CTR_BUFFER* )buf)->c_counter = ((CTR_BUFFER* )buf)->enc_counter = NULL;

        /* For ctr */
        ((CTR_BUFFER* )buf)->c_counter_pos = 0;
        ((CTR_BUFFER* )buf)->blocksize = size;

        ((CTR_BUFFER* )buf)->c_counter = (u8 *)gf_malloc(size);
        if (((CTR_BUFFER* )buf)->c_counter==NULL) goto freeall;

        ((CTR_BUFFER* )buf)->enc_counter = (u8 *)gf_malloc(size);
        if (((CTR_BUFFER* )buf)->enc_counter==NULL) goto freeall;

        if (IV!=NULL) {
                memcpy(((CTR_BUFFER* )buf)->enc_counter, IV, size);
                memcpy(((CTR_BUFFER* )buf)->c_counter, IV, size);
        }

        /* End ctr */

        return GF_OK;
freeall:
        gf_free(((CTR_BUFFER* )buf)->c_counter);
        gf_free(((CTR_BUFFER* )buf)->enc_counter);
        return GF_OUT_OF_MEM;
}

GF_Err _mcrypt_set_state(void *_buf, void *IV, int size)
{
        CTR_BUFFER* buf = (CTR_BUFFER* )_buf;
        ((CTR_BUFFER* )buf)->c_counter_pos = ((u8*)IV)[0];
        memcpy(((CTR_BUFFER* )buf)->c_counter, &((u8*)IV)[1], size-1);
        memcpy(((CTR_BUFFER* )buf)->enc_counter, &((u8*)IV)[1], size-1);

        return GF_OK;
}

GF_Err _mcrypt_get_state(void *buf, void *IV, int *size)
{
        if (*size < ((CTR_BUFFER* )buf)->blocksize + 1) {
                *size = ((CTR_BUFFER* )buf)->blocksize + 1;
                return GF_BAD_PARAM;
        }
        *size = ((CTR_BUFFER* )buf)->blocksize + 1;

        ((u8 *)IV)[0] = ((CTR_BUFFER* )buf)->c_counter_pos;
        memcpy( & ((u8 *) IV)[1], ((CTR_BUFFER* )buf)->c_counter, ((CTR_BUFFER* )buf)->blocksize);

        return GF_OK;
}


void _end_mcrypt(void *buf) {
        gf_free(((CTR_BUFFER* )buf)->c_counter);
        gf_free(((CTR_BUFFER* )buf)->enc_counter);
}

static GFINLINE
void xor_stuff( CTR_BUFFER *buf, void* akey, void (*func)(void*,void*), u8* plain,  int blocksize, int xor_size)
{
        void (*_mcrypt_block_encrypt) (void *, void *);

        _mcrypt_block_encrypt = func;

        if (xor_size == blocksize) {
                if (((CTR_BUFFER* )buf)->c_counter_pos == 0) {

                        memcpy( ((CTR_BUFFER* )buf)->enc_counter, ((CTR_BUFFER* )buf)->c_counter, blocksize);
                        _mcrypt_block_encrypt(akey, ((CTR_BUFFER* )buf)->enc_counter);

                        memxor( plain, ((CTR_BUFFER* )buf)->enc_counter, blocksize);

                        increase_counter( ((CTR_BUFFER* )buf)->c_counter, blocksize);


                } else {
                        int size = blocksize - ((CTR_BUFFER* )buf)->c_counter_pos;

                        memxor( plain, &((CTR_BUFFER* )buf)->enc_counter[((CTR_BUFFER* )buf)->c_counter_pos],
                                size);

                        increase_counter( ((CTR_BUFFER* )buf)->c_counter, blocksize);

                        memcpy( ((CTR_BUFFER* )buf)->enc_counter, ((CTR_BUFFER* )buf)->c_counter, blocksize);
                        _mcrypt_block_encrypt(akey, ((CTR_BUFFER* )buf)->enc_counter);

                        memxor( &plain[size], ((CTR_BUFFER* )buf)->enc_counter,
                                ((CTR_BUFFER* )buf)->c_counter_pos);

                        /* ((CTR_BUFFER* )buf)->c_counter_pos remains the same */

                }
        } else { /* xor_size != blocksize */
                if (((CTR_BUFFER* )buf)->c_counter_pos == 0) {
                        memcpy( ((CTR_BUFFER* )buf)->enc_counter, ((CTR_BUFFER* )buf)->c_counter, blocksize);
                        _mcrypt_block_encrypt(akey, ((CTR_BUFFER* )buf)->enc_counter);

                        memxor( plain, ((CTR_BUFFER* )buf)->enc_counter, xor_size);
                        ((CTR_BUFFER* )buf)->c_counter_pos = xor_size;
                } else {
                        int size = blocksize - ((CTR_BUFFER* )buf)->c_counter_pos;
                        int min_size =  size < xor_size ? size: xor_size;

                        memxor( plain, &((CTR_BUFFER* )buf)->enc_counter[((CTR_BUFFER* )buf)->c_counter_pos],
                                min_size);

                        ((CTR_BUFFER* )buf)->c_counter_pos += min_size;

                        if (min_size >= xor_size)
                                return;

                        increase_counter( ((CTR_BUFFER* )buf)->c_counter, blocksize);

                        memcpy( ((CTR_BUFFER* )buf)->enc_counter, ((CTR_BUFFER* )buf)->c_counter, blocksize);
                        _mcrypt_block_encrypt(akey, ((CTR_BUFFER* )buf)->enc_counter);

                        memxor( &plain[min_size], ((CTR_BUFFER* )buf)->enc_counter,
                                xor_size - min_size);

                        ((CTR_BUFFER* )buf)->c_counter_pos = xor_size - min_size;

                }

        }
        return;
}

GF_Err _mcrypt(void * buf,void *plaintext, int len, int blocksize, void* akey, void (*func)(void*,void*), void (*func2)(void*,void*))
{       /* plaintext can be any size */
        u8 *plain;
        int dlen, j=0;
        int modlen;

        dlen = len / blocksize;
        plain = (u8 *)plaintext;
        for (j = 0; j < dlen; j++) {

                xor_stuff((CTR_BUFFER*) buf, akey, func, plain, blocksize, blocksize);

                plain += blocksize;

                /* Put the new register */

        }
        modlen = len % blocksize;
        if (modlen > 0) {
                /* This is only useful if encrypting the
                 * final block. Otherwise you'll not be
                 * able to decrypt it.
                 */

                xor_stuff( (CTR_BUFFER*)buf, akey, func, plain, blocksize, modlen);

        }

        return GF_OK;
}


GF_Err _mdecrypt(void * buf,void *plaintext, int len, int blocksize, void* akey, void (*func)(void*,void*), void (*func2)(void*,void*))
{       /* plaintext can be any size */
        return _mcrypt( buf, plaintext, len, blocksize, akey, func, func2);
}

void gf_crypt_register_ctr(GF_Crypt *td)
{
        td->mode_name = "CTR";
        td->_init_mcrypt = _init_mcrypt;
        td->_end_mcrypt = _end_mcrypt;
        td->_mcrypt = _mcrypt;
        td->_mdecrypt = _mdecrypt;
        td->_mcrypt_get_state = _mcrypt_get_state;
        td->_mcrypt_set_state = _mcrypt_set_state;

        td->has_IV = 1;
        td->is_block_mode = 1;
        td->is_block_algo_mode = 1;
        td->mode_size = sizeof(CTR_BUFFER);
        td->mode_version = 20020307;
}
#endif /*!defined(GPAC_DISABLE_MCRYPT)*/
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root/src/mcrypt/ctr.c

DEFINITIONS
