root/src/mcrypt/ofb.c

DEFINITIONS

1. _init_mcrypt
2. _mcrypt_get_state
3. _mcrypt_set_state
4. _end_mcrypt
5. _mcrypt
6. _mdecrypt
7. gf_crypt_register_ofb

/*
 * Copyright (C) 1998,1999,2000,2001,2002 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_CRYPT_ISMA_ONLY) && !defined(GPAC_DISABLE_MCRYPT)

typedef struct ofb_buf {
        u8* s_register;
        u8* enc_s_register;
        int blocksize;
} OFB_BUFFER;


/* OFB MODE */

static GF_Err _init_mcrypt( OFB_BUFFER* buf, void *key, int lenofkey, void *IV, int size)
{

        buf->s_register = buf->enc_s_register = NULL;

        buf->blocksize = size;

        /* For ofb */
        buf->s_register=gf_malloc( size);
        if (buf->s_register==NULL) goto freeall;

        buf->enc_s_register=gf_malloc( size);
        if (buf->enc_s_register==NULL) goto freeall;

        if (IV!=NULL) {
                memcpy(buf->s_register, IV, size);
        } else {
                memset(buf->s_register, 0, size);
        }
        /* End ofb */

        return GF_OK;

freeall:
        if (buf->s_register) gf_free(buf->s_register);
        if (buf->enc_s_register) gf_free(buf->enc_s_register);
        return GF_OUT_OF_MEM;
}

static GF_Err _mcrypt_get_state( OFB_BUFFER* buf, u8 *IV, int *size)
{
        if (*size < buf->blocksize) {
                *size = buf->blocksize;
                return GF_BAD_PARAM;
        }
        *size = buf->blocksize;

        memcpy( IV, buf->s_register, buf->blocksize);

        return GF_OK;
}

static GF_Err _mcrypt_set_state( OFB_BUFFER* buf, void *IV, int size)
{
        memcpy(buf->enc_s_register, IV, size);
        memcpy(buf->s_register, IV, size);

        return GF_OK;
}


static void _end_mcrypt( OFB_BUFFER* buf) {
        gf_free(buf->s_register);
        gf_free(buf->enc_s_register);
}


static GF_Err _mcrypt( OFB_BUFFER* buf,void *plaintext, int len, int blocksize, void* akey, void (*func)(void*,void*), void (*func2)(void*,void*) )
{       /* plaintext is 1 u8 (8bit ofb) */
        char *plain = plaintext;
        int i, j;
        void (*_mcrypt_block_encrypt) (void *, void *);

        _mcrypt_block_encrypt = func;

        for (j = 0; j < len; j++) {

                memcpy(buf->enc_s_register, buf->s_register, blocksize);

                _mcrypt_block_encrypt(akey, buf->enc_s_register);

                plain[j] ^= buf->enc_s_register[0];

                /* Shift the register */
                for (i = 0; i < (blocksize - 1); i++)
                        buf->s_register[i] = buf->s_register[i + 1];

                buf->s_register[blocksize - 1] = buf->enc_s_register[0];
        }

        return GF_OK;

}


static GF_Err _mdecrypt( OFB_BUFFER* buf, void *plaintext, int len, int blocksize, void* akey, void (*func)(void*,void*), void (*func2)(void*,void*))
{       /* plaintext is 1 u8 (8bit ofb) */
        char *plain = plaintext;
        int i, j;
        void (*_mcrypt_block_encrypt) (void *, void *);

        _mcrypt_block_encrypt = func;

        for (j = 0; j < len; j++) {

                memcpy(buf->enc_s_register, buf->s_register, blocksize);

                _mcrypt_block_encrypt(akey, buf->enc_s_register);

                /* Shift the register */
                for (i = 0; i < (blocksize - 1); i++)
                        buf->s_register[i] = buf->s_register[i + 1];

                buf->s_register[blocksize - 1] = buf->enc_s_register[0];

                plain[j] ^= buf->enc_s_register[0];

        }

        return GF_OK;
}

void gf_crypt_register_ofb(GF_Crypt *td)
{
        td->mode_name = "OFB";
        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 = 0;
        td->is_block_algo_mode = 1;
        td->mode_size = sizeof(OFB_BUFFER);
        td->mode_version = 20010310;
}

#endif /*!defined(GPAC_CRYPT_ISMA_ONLY) && !defined(GPAC_DISABLE_MCRYPT)*/