root/src/mcrypt/nofb.c

DEFINITIONS

1. _init_mcrypt
2. _mcrypt_set_state
3. _mcrypt_get_state
4. _end_mcrypt
5. xor_stuff
6. _mcrypt
7. gf_crypt_register_nofb

/*
 * Copyright (C) 1998,1999,2000,2001 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 ncfb_buf {
        u8*   enc_s_register;
        u8* s_register;
        int   s_register_pos;
        int   blocksize;
} nOFB_BUFFER;

/* nOFB MODE */

static GF_Err _init_mcrypt( nOFB_BUFFER* buf, void *key, int lenofkey, void *IV, int size)
{
        buf->enc_s_register = buf->s_register = NULL;
        buf->s_register_pos = 0;

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

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

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

        /* End nofb */

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

static GF_Err _mcrypt_set_state( nOFB_BUFFER* buf, u8 *IV, int size)
{
        buf->s_register_pos = IV[0];
        memcpy(buf->enc_s_register, &IV[1], size-1);
        memcpy(buf->s_register, &IV[1], size-1);

        return GF_OK;
}

static GF_Err _mcrypt_get_state( nOFB_BUFFER* buf, u8 *IV, int *size)
{
        if (*size < buf->blocksize + 1) {
                *size = buf->blocksize + 1;
                return GF_BAD_PARAM;
        }
        *size = buf->blocksize + 1;

        IV[0] = buf->s_register_pos;
        memcpy( &IV[1], buf->s_register, buf->blocksize);

        return GF_OK;
}


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

GFINLINE static
void xor_stuff( nOFB_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 (buf->s_register_pos == 0) {

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

                        _mcrypt_block_encrypt(akey, buf->enc_s_register);

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

                        memxor( plain, buf->enc_s_register, blocksize);

                } else {
                        int size = blocksize - buf->s_register_pos;

                        memxor( plain, &buf->enc_s_register[buf->s_register_pos],
                                size);

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

                        _mcrypt_block_encrypt(akey, buf->enc_s_register);

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

                        memxor( &plain[size], buf->enc_s_register,
                                buf->s_register_pos);

                        /* buf->s_register_pos remains the same */
                }
        } else { /* xor_size != blocksize */
                if (buf->s_register_pos == 0) {
                        memcpy(buf->enc_s_register, buf->s_register, blocksize);

                        _mcrypt_block_encrypt(akey, buf->enc_s_register);

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

                        memxor( plain, buf->enc_s_register, xor_size);

                        buf->s_register_pos = xor_size;
                } else {
                        int size = blocksize - buf->s_register_pos;
                        int min_size =  size < xor_size ? size: xor_size;

                        memxor( plain, &buf->enc_s_register[buf->s_register_pos],
                                min_size);

                        buf->s_register_pos += min_size;

                        if (min_size >= xor_size)
                                return;

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

                        _mcrypt_block_encrypt(akey, buf->enc_s_register);

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

                        memxor( &plain[min_size], buf->s_register,
                                xor_size - min_size);

                        buf->s_register_pos = xor_size - min_size;

                }

        }
        return;
}


static GF_Err _mcrypt( nOFB_BUFFER* buf,void *plaintext, int len, int blocksize, void* akey, void (*func)(void*,void*), void (*func2)(void*,void*))
{       /* plaintext is n*blocksize bytes (nbit cfb) */
        u8* plain;
        int dlen, j=0;
        void (*_mcrypt_block_encrypt) (void *, void *);
        int modlen;

        _mcrypt_block_encrypt = func;

        dlen = len / blocksize;
        plain = plaintext;
        for (j = 0; j < dlen; j++) {
                xor_stuff( buf, akey, func, plain, blocksize, blocksize);

                plain += blocksize;

        }
        modlen = len % blocksize;
        if (modlen > 0) {
                xor_stuff( buf, akey, func, plain, blocksize, modlen);
        }

        return GF_OK;
}

void gf_crypt_register_nofb(GF_Crypt *td)
{
        td->mode_name = "nOFB";
        td->_init_mcrypt = _init_mcrypt;
        td->_end_mcrypt = _end_mcrypt;
        td->_mcrypt = _mcrypt;
        td->_mdecrypt = _mcrypt;
        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(nOFB_BUFFER);
        td->mode_version = 20020307;
}

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