css.c

来自「君正早期ucos系统(只有早期的才不没有打包成库),MPLAYER,文件系统,图」· C语言 代码 · 共 1,697 行 · 第 1/4 页

/*****************************************************************************
 * css.c: Functions for DVD authentication and descrambling
 *****************************************************************************
 * Copyright (C) 1999-2003 VideoLAN
 * $Id: css.c,v 1.3 2008/04/12 07:14:44 dsqiu Exp $
 *
 * Authors: St閜hane Borel <[e-mail]>
 *          H錵an Hjort <[e-mail]>
 *
 * based on:
 *  - css-auth by Derek Fawcus <[e-mail]>
 *  - DVD CSS ioctls example program by Andrew T. Veliath <[e-mail]>
 *  - The Divide and conquer attack by Frank A. Stevenson <[e-mail]>
 *     (see http://www-2.cs.cmu.edu/~dst/DeCSS/FrankStevenson/index.html)
 *  - DeCSSPlus by Ethan Hawke
 *  - DecVOB
 *  see http://www.lemuria.org/DeCSS/ by Tom Vogt for more information.
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include "config.h"

#include <mplaylib.h>
#include <mplaylib.h>
#include <mplaylib.h>
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_SYS_PARAM_H
#   include <sys/param.h>
#endif
#ifdef HAVE_UNISTD_H
#   include <unistd.h>
#endif
#include <fcntl.h>

#ifdef HAVE_LIMITS_H
#   include <limits.h>
#endif

#include "dvdcss/dvdcss.h"

#include "common.h"
#include "css.h"
#include "libdvdcss.h"
#include "csstables.h"
#include "ioctl.h"
#include "device.h"
#undef memcpy
#define memcpy uc_memcpy
/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static void PrintKey        ( dvdcss_t, char *, uint8_t const * );

static int  GetBusKey       ( dvdcss_t );
static int  GetASF          ( dvdcss_t );

static void CryptKey        ( int, int, uint8_t const *, uint8_t * );
static void DecryptKey      ( uint8_t,
                              uint8_t const *, uint8_t const *, uint8_t * );

static int  DecryptDiscKey  ( dvdcss_t, uint8_t const *, dvd_key_t );
static int  CrackDiscKey    ( dvdcss_t, uint8_t * );

static void DecryptTitleKey ( dvd_key_t, dvd_key_t );
static int  RecoverTitleKey ( int, uint8_t const *,
                              uint8_t const *, uint8_t const *, uint8_t * );
static int  CrackTitleKey   ( dvdcss_t, int, int, dvd_key_t );

static int  AttackPattern   ( uint8_t const[], int, uint8_t * );
#if 0
static int  AttackPadding   ( uint8_t const[], int, uint8_t * );
#endif

/*****************************************************************************
 * _dvdcss_test: check if the disc is encrypted or not
 *****************************************************************************/
int _dvdcss_test( dvdcss_t dvdcss )
{
    int i_ret, i_copyright;

    i_ret = ioctl_ReadCopyright( dvdcss->i_fd, 0 /* i_layer */, &i_copyright );

#ifdef WIN32
    if( i_ret < 0 )
    {
        /* Maybe we didn't have enough privileges to read the copyright
         * (see ioctl_ReadCopyright comments).
         * Apparently, on unencrypted DVDs _dvdcss_disckey() always fails, so
         * we can check this as a workaround. */
        i_ret = 0;
        i_copyright = 1;
        if( _dvdcss_disckey( dvdcss ) < 0 )
        {
            i_copyright = 0;
        }
    }
#endif

    if( i_ret < 0 )
    {
        /* Since it's the first ioctl we try to issue, we add a notice */
        print_error( dvdcss, "css error: ioctl_ReadCopyright failed, "
                     "make sure there is a DVD in the drive, and that "
                     "you have used the correct device node." );

        return i_ret;
    }

    return i_copyright;
}

/*****************************************************************************
 * _dvdcss_title: crack or decrypt the current title key if needed
 *****************************************************************************
 * This function should only be called by dvdcss->pf_seek and should eventually
 * not be external if possible.
 *****************************************************************************/
int _dvdcss_title ( dvdcss_t dvdcss, int i_block )
{
    dvd_title_t *p_title;
    dvd_title_t *p_newtitle;
    dvd_key_t    p_title_key;
    int          i_fd, i_ret = -1, b_cache = 0;

    if( ! dvdcss->b_scrambled )
    {
        return 0;
    }

    /* Check if we've already cracked this key */
    p_title = dvdcss->p_titles;
    while( p_title != NULL
            && p_title->p_next != NULL
            && p_title->p_next->i_startlb <= i_block )
    {
        p_title = p_title->p_next;
    }

    if( p_title != NULL
         && p_title->i_startlb == i_block )
    {
        /* We've already cracked this key, nothing to do */
        memcpy( dvdcss->css.p_title_key, p_title->p_key, sizeof(dvd_key_t) );
        return 0;
    }

    /* Check whether the key is in our disk cache */
    if( dvdcss->psz_cachefile[0] )
    {
        /* XXX: be careful, we use sprintf and not snprintf */
        sprintf( dvdcss->psz_block, "%.10x", i_block );
        i_fd = open( dvdcss->psz_cachefile, O_RDONLY );
        b_cache = 1;

        if( i_fd >= 0 )
        {
            char psz_key[KEY_SIZE * 3];
            unsigned int k0, k1, k2, k3, k4;

            psz_key[KEY_SIZE * 3 - 1] = '\0';

            if( read( i_fd, psz_key, KEY_SIZE * 3 - 1 ) == KEY_SIZE * 3 - 1
                 && sscanf( psz_key, "%x:%x:%x:%x:%x",
                            &k0, &k1, &k2, &k3, &k4 ) == 5 )
            {
                p_title_key[0] = k0;
                p_title_key[1] = k1;
                p_title_key[2] = k2;
                p_title_key[3] = k3;
                p_title_key[4] = k4;
                PrintKey( dvdcss, "title key found in cache ", p_title_key );

                /* Don't try to save it again */
                b_cache = 0;
                i_ret = 1;
            }

            close( i_fd );
        }
    }

    /* Crack or decrypt CSS title key for current VTS */
    if( i_ret < 0 )
    {
        i_ret = _dvdcss_titlekey( dvdcss, i_block, p_title_key );

        if( i_ret < 0 )
        {
            print_error( dvdcss, "fatal error in vts css key" );
            return i_ret;
        }

        if( i_ret == 0 )
        {
            print_debug( dvdcss, "unencrypted title" );
            /* We cache this anyway, so we don't need to check again. */
        }
    }

    /* Key is valid, we store it on disk. */
    if( dvdcss->psz_cachefile[0] && b_cache )
    {
        i_fd = open( dvdcss->psz_cachefile, O_RDWR|O_CREAT, 0644 );
        if( i_fd >= 0 )
        {
            char psz_key[KEY_SIZE * 3 + 2];

            sprintf( psz_key, "%02x:%02x:%02x:%02x:%02x\r\n",
                              p_title_key[0], p_title_key[1], p_title_key[2],
                              p_title_key[3], p_title_key[4] );

            write( i_fd, psz_key, KEY_SIZE * 3 + 1 );
            close( i_fd );
        }
    }

    /* Find our spot in the list */
    p_newtitle = NULL;
    p_title = dvdcss->p_titles;
    while( ( p_title != NULL ) && ( p_title->i_startlb < i_block ) )
    {
        p_newtitle = p_title;
        p_title = p_title->p_next;
    }

    /* Save the found title */
    p_title = p_newtitle;

    /* Write in the new title and its key */
    p_newtitle = malloc( sizeof( dvd_title_t ) );
    p_newtitle->i_startlb = i_block;
    memcpy( p_newtitle->p_key, p_title_key, KEY_SIZE );

    /* Link it at the head of the (possibly empty) list */
    if( p_title == NULL )
    {
        p_newtitle->p_next = dvdcss->p_titles;
        dvdcss->p_titles = p_newtitle;
    }
    /* Link the new title inside the list */
    else
    {
        p_newtitle->p_next = p_title->p_next;
        p_title->p_next = p_newtitle;
    }

    memcpy( dvdcss->css.p_title_key, p_title_key, KEY_SIZE );
    return 0;
}

/*****************************************************************************
 * _dvdcss_disckey: get disc key.
 *****************************************************************************
 * This function should only be called if DVD ioctls are present.
 * It will set dvdcss->i_method = DVDCSS_METHOD_TITLE if it fails to find
 * a valid disc key.
 * Two decryption methods are offered:
 *  -disc key hash crack,
 *  -decryption with player keys if they are available.
 *****************************************************************************/
int _dvdcss_disckey( dvdcss_t dvdcss )
{
    unsigned char p_buffer[ DVD_DISCKEY_SIZE ];
    dvd_key_t p_disc_key;
    int i;

    if( GetBusKey( dvdcss ) < 0 )
    {
        return -1;
    }

    /* Get encrypted disc key */
    if( ioctl_ReadDiscKey( dvdcss->i_fd, &dvdcss->css.i_agid, p_buffer ) < 0 )
    {
        print_error( dvdcss, "ioctl ReadDiscKey failed" );
        return -1;
    }

    /* This should have invaidated the AGID and got us ASF=1. */
    if( GetASF( dvdcss ) != 1 )
    {
        /* Region mismatch (or region not set) is the most likely source. */
        print_error( dvdcss,
                     "ASF not 1 after reading disc key (region mismatch?)" );
        ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
        return -1;
    }

    /* Shuffle disc key using bus key */
    for( i = 0 ; i < DVD_DISCKEY_SIZE ; i++ )
    {
        p_buffer[ i ] ^= dvdcss->css.p_bus_key[ 4 - (i % KEY_SIZE) ];
    }

    /* Decrypt disc key */
    switch( dvdcss->i_method )
    {
        case DVDCSS_METHOD_KEY:

            /* Decrypt disc key with player key. */
            PrintKey( dvdcss, "decrypting disc key ", p_buffer );
            if( ! DecryptDiscKey( dvdcss, p_buffer, p_disc_key ) )
            {
                PrintKey( dvdcss, "decrypted disc key is ", p_disc_key );
                break;
            }
            print_debug( dvdcss, "failed to decrypt the disc key, "
                                 "faulty drive/kernel? "
                                 "cracking title keys instead" );

            /* Fallback, but not to DISC as the disc key might be faulty */
            dvdcss->i_method = DVDCSS_METHOD_TITLE;
            break;

        case DVDCSS_METHOD_DISC:

            /* Crack Disc key to be able to use it */
            memcpy( p_disc_key, p_buffer, KEY_SIZE );
            PrintKey( dvdcss, "cracking disc key ", p_disc_key );
            if( ! CrackDiscKey( dvdcss, p_disc_key ) )
            {
                PrintKey( dvdcss, "cracked disc key is ", p_disc_key );
                break;
            }
            print_debug( dvdcss, "failed to crack the disc key" );
            memset( p_disc_key, 0, KEY_SIZE );
            dvdcss->i_method = DVDCSS_METHOD_TITLE;
            break;

        default:

            print_debug( dvdcss, "disc key needs not be decrypted" );
            memset( p_disc_key, 0, KEY_SIZE );
            break;
    }

    memcpy( dvdcss->css.p_disc_key, p_disc_key, KEY_SIZE );

    return 0;
}


/*****************************************************************************
 * _dvdcss_titlekey: get title key.
 *****************************************************************************/
int _dvdcss_titlekey( dvdcss_t dvdcss, int i_pos, dvd_key_t p_title_key )
{
    static uint8_t p_garbage[ DVDCSS_BLOCK_SIZE ];  /* we never read it back */
    uint8_t p_key[ KEY_SIZE ];
    int i, i_ret = 0;

    if( dvdcss->b_ioctls && ( dvdcss->i_method == DVDCSS_METHOD_KEY ||
                              dvdcss->i_method == DVDCSS_METHOD_DISC ) )
    {
        /* We have a decrypted Disc key and the ioctls are available,
         * read the title key and decrypt it.
         */

        print_debug( dvdcss, "getting title key at block %i the classic way",
                             i_pos );

        /* We need to authenticate again every time to get a new session key */
        if( GetBusKey( dvdcss ) < 0 )
        {
            return -1;
        }

        /* Get encrypted title key */
        if( ioctl_ReadTitleKey( dvdcss->i_fd, &dvdcss->css.i_agid,
                                i_pos, p_key ) < 0 )
        {
            print_debug( dvdcss,
                         "ioctl ReadTitleKey failed (region mismatch?)" );
            i_ret = -1;
        }

        /* Test ASF, it will be reset to 0 if we got a Region error */
        switch( GetASF( dvdcss ) )
        {
            case -1:
                /* An error getting the ASF status, something must be wrong. */
                print_debug( dvdcss, "lost ASF requesting title key" );
                ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
                i_ret = -1;
                break;

            case 0:
                /* This might either be a title that has no key,
                 * or we encountered a region error. */
                print_debug( dvdcss, "lost ASF requesting title key" );
                break;

            case 1:
                /* Drive status is ok. */
                /* If the title key request failed, but we did not loose ASF,
                 * we might stil have the AGID.  Other code assume that we
                 * will not after this so invalidate it(?). */
                if( i_ret < 0 )
                {
                    ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
                }
                break;
        }

        if( !( i_ret < 0 ) )
        {
            /* Decrypt title key using the bus key */
            for( i = 0 ; i < KEY_SIZE ; i++ )