csa.c

uclinux 下的vlc播放器源代码

/*****************************************************************************
 * libcsa.c: CSA scrambler/descrambler
 *****************************************************************************
 * Copyright (C) 2004-2005 Laurent Aimar
 * $Id: csa.c 13905 2006-01-12 23:10:04Z dionoea $
 *
 * Authors: Laurent Aimar <[e-mail]>
 *          Jean-Paul Saman <jpsaman #_at_# m2x.nl>
 *
 * This program 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., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*
 * XXX: A great part is just a copy/past of deCSA but I can't find the
 * author and the license. If there is a problem with it please e-mail me.
 */

#include <stdlib.h>
#include <vlc/vlc.h>

#include "csa.h"

struct csa_t
{
    /* odd and even keys */
    uint8_t o_ck[8];
    uint8_t e_ck[8];

    uint8_t o_kk[57];
    uint8_t e_kk[57];

    /* cypher state */
    int     A[11];
    int     B[11];
    int     X, Y, Z;
    int     D, E, F;
    int     p, q, r;
};

static void csa_ComputeKey( uint8_t kk[57], uint8_t ck[8] );

static void csa_StreamCypher( csa_t *c, int b_init, uint8_t *ck, uint8_t *sb, uint8_t *cb );

static void csa_BlockDecypher( uint8_t kk[57], uint8_t ib[8], uint8_t bd[8] );
static void csa_BlockCypher( uint8_t kk[57], uint8_t bd[8], uint8_t ib[8] );

/*****************************************************************************
 * csa_New:
 *****************************************************************************/
csa_t *csa_New()
{
    csa_t *c = malloc( sizeof( csa_t ) );
    memset( c, 0, sizeof( csa_t ) );

    return c;
}

/*****************************************************************************
 * csa_Delete:
 *****************************************************************************/
void   csa_Delete( csa_t *c )
{
    free( c );
}

/*****************************************************************************
 * csa_SetCW:
 *****************************************************************************/
void csa_SetCW( csa_t *c, uint8_t o_ck[8], uint8_t e_ck[8] )
{
    memcpy( c->o_ck, o_ck, 8 );
    csa_ComputeKey( c->o_kk, o_ck );

    memcpy( c->e_ck, e_ck, 8 );
    csa_ComputeKey( c->e_kk, e_ck );
}

/*****************************************************************************
 * csa_Decrypt:
 *****************************************************************************/
void csa_Decrypt( csa_t *c, uint8_t *pkt, int i_pkt_size )
{
    uint8_t *ck;
    uint8_t *kk;

    uint8_t  ib[8], stream[8], block[8];

    int     i_hdr, i_residue;
    int     i, j, n;

    /* transport scrambling control */
    if( (pkt[3]&0x80) == 0 )
    {
        /* not scrambled */
        return;
    }
    if( pkt[3]&0x40 )
    {
        ck = c->o_ck;
        kk = c->o_kk;
    }
    else
    {
        ck = c->e_ck;
        kk = c->e_kk;
    }

    /* clear transport scrambling control */
    pkt[3] &= 0x3f;

    i_hdr = 4;
    if( pkt[3]&0x20 )
    {
        /* skip adaption field */
        i_hdr += pkt[4] + 1;
    }

    if( 188 - i_hdr < 8 )
        return;

    /* init csa state */
    csa_StreamCypher( c, 1, ck, &pkt[i_hdr], ib );

    /* */
    n = (i_pkt_size - i_hdr) / 8;
    if( n < 0 )
        return;
        
    i_residue = (i_pkt_size - i_hdr) % 8;    
    for( i = 1; i < n + 1; i++ )
    {
        csa_BlockDecypher( kk, ib, block );
        if( i != n )
        {
            csa_StreamCypher( c, 0, ck, NULL, stream );
            for( j = 0; j < 8; j++ )
            {
                /* xor ib with stream */
                ib[j] = pkt[i_hdr+8*i+j] ^ stream[j];
            }
        }
        else
        {
            /* last block */
            for( j = 0; j < 8; j++ )
            {
                ib[j] = 0;
            }
        }
        /* xor ib with block */
        for( j = 0; j < 8; j++ )
        {
            pkt[i_hdr+8*(i-1)+j] = ib[j] ^ block[j];
        }
    }

    if( i_residue > 0 )
    {
        csa_StreamCypher( c, 0, ck, NULL, stream );
        for( j = 0; j < i_residue; j++ )
        {
            pkt[i_pkt_size - i_residue + j] ^= stream[j];
        }
    }
}

/*****************************************************************************
 * csa_Encrypt:
 *****************************************************************************/
void csa_Encrypt( csa_t *c, uint8_t *pkt, int i_pkt_size, int b_odd )
{
    uint8_t *ck;
    uint8_t *kk;

    int i, j;
    int i_hdr = 4; /* hdr len */
    uint8_t  ib[184/8+2][8], stream[8], block[8];
    int n, i_residue;

    /* set transport scrambling control */
    pkt[3] |= 0x80;
    if( b_odd )
    {
        pkt[3] |= 0x40;
    }

    if( b_odd )
    {
        ck = c->o_ck;
        kk = c->o_kk;
    }
    else
    {
        ck = c->e_ck;
        kk = c->e_kk;
    }

    /* hdr len */
    i_hdr = 4;
    if( pkt[3]&0x20 )
    {
        /* skip adaption field */
        i_hdr += pkt[4] + 1;
    }
    n = (i_pkt_size - i_hdr) / 8;
    i_residue = (i_pkt_size - i_hdr) % 8;

    if( n <= 0 )
    {
        pkt[3] &= 0x3f;
        return;
    }

    /* */
    for( i = 0; i < 8; i++ )
    {
        ib[n+1][i] = 0;
    }
    for( i = n; i  > 0; i-- )
    {
        for( j = 0; j < 8; j++ )
        {
            block[j] = pkt[i_hdr+8*(i-1)+j] ^ib[i+1][j];
        }
        csa_BlockCypher( kk, block, ib[i] );
    }

    /* init csa state */
    csa_StreamCypher( c, 1, ck, ib[1], stream );

    for( i = 0; i < 8; i++ )
    {
        pkt[i_hdr+i] = ib[1][i];
    }
    for( i = 2; i < n+1; i++ )
    {
        csa_StreamCypher( c, 0, ck, NULL, stream );
        for( j = 0; j < 8; j++ )
        {
            pkt[i_hdr+8*(i-1)+j] = ib[i][j] ^ stream[j];
        }
    }
    if( i_residue > 0 )
    {
        csa_StreamCypher( c, 0, ck, NULL, stream );
        for( j = 0; j < i_residue; j++ )
        {
            pkt[i_pkt_size - i_residue + j] ^= stream[j];
        }
    }
}

/*****************************************************************************
 * Divers
 *****************************************************************************/
static const uint8_t key_perm[0x40] =
{
    0x12,0x24,0x09,0x07,0x2A,0x31,0x1D,0x15,0x1C,0x36,0x3E,0x32,0x13,0x21,0x3B,0x40,
    0x18,0x14,0x25,0x27,0x02,0x35,0x1B,0x01,0x22,0x04,0x0D,0x0E,0x39,0x28,0x1A,0x29,
    0x33,0x23,0x34,0x0C,0x16,0x30,0x1E,0x3A,0x2D,0x1F,0x08,0x19,0x17,0x2F,0x3D,0x11,
    0x3C,0x05,0x38,0x2B,0x0B,0x06,0x0A,0x2C,0x20,0x3F,0x2E,0x0F,0x03,0x26,0x10,0x37,
};

static void csa_ComputeKey( uint8_t kk[57], uint8_t ck[8] )
{
    int i,j,k;
    int bit[64];
    int newbit[64];
    int kb[9][8];

    /* from a cw create 56 key bytes, here kk[1..56] */