ref: 673cf17677756d73647eaed5ceb2b2e108be1f93
dir: /src/css.c/
/*****************************************************************************
* css.c: Functions for DVD authentication and descrambling
*****************************************************************************
* Copyright (C) 1999-2008 VideoLAN
* $Id$
*
* Authors: Stéphane Borel <stef@via.ecp.fr>
* Håkan Hjort <d95hjort@dtek.chalmers.se>
*
* based on:
* - css-auth by Derek Fawcus <derek@spider.com>
* - DVD CSS ioctls example program by Andrew T. Veliath <andrewtv@usa.net>
* - The Divide and conquer attack by Frank A. Stevenson <frank@funcom.com>
* (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 library 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 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this library; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*****************************************************************************/
/*****************************************************************************
* Preamble
*****************************************************************************/
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.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"
/*****************************************************************************
* 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
*****************************************************************************
* Return values:
* 1: DVD is scrambled but can be read
* 0: DVD is not scrambled and can be read
* -1: could not get "copyright" information
* -2: could not get RPC information (reading the disc might be possible)
* -3: drive is RPC-II, region is not set, and DVD is scrambled: the RPC
* scheme will prevent us from reading the scrambled data
*****************************************************************************/
int _dvdcss_test( dvdcss_t dvdcss )
{
char const *psz_type, *psz_rpc;
int i_ret, i_copyright, i_type, i_mask, i_rpc;
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: could not get \"copyright\""
" information, make sure there is a DVD in the drive,"
" and that you have used the correct device node." );
return -1;
}
print_debug( dvdcss, "disc reports copyright information 0x%x",
i_copyright );
i_ret = ioctl_ReportRPC( dvdcss->i_fd, &i_type, &i_mask, &i_rpc);
if( i_ret < 0 )
{
print_error( dvdcss, "css error: could not get RPC status. Assuming RPC-I drive." );
i_type = i_mask = i_rpc = 0;
}
switch( i_rpc )
{
case 0: psz_rpc = "RPC-I"; break;
case 1: psz_rpc = "RPC-II"; break;
default: psz_rpc = "unknown RPC scheme"; break;
}
switch( i_type )
{
case 0: psz_type = "no region code set"; break;
case 1: psz_type = "region code set"; break;
case 2: psz_type = "one region change remaining"; break;
case 3: psz_type = "region code set permanently"; break;
default: psz_type = "unknown status"; break;
}
print_debug( dvdcss, "drive region mask 0x%x, %s, %s",
i_mask, psz_rpc, psz_type );
if( i_copyright && i_rpc == 1 && i_type == 0 )
{
print_error( dvdcss, "css error: drive will prevent access to "
"scrambled data" );
return -3;
}
return i_copyright ? 1 : 0;
}
/*****************************************************************************
* _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 */
memset( p_disc_key, 0, KEY_SIZE );
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 )
{
i_ret = -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++ )
{
p_key[ i ] ^= dvdcss->css.p_bus_key[ 4 - (i % KEY_SIZE) ];
}
/* If p_key is all zero then there really wasn't any key present
* even though we got to read it without an error. */
if( !( p_key[0] | p_key[1] | p_key[2] | p_key[3] | p_key[4] ) )
{
i_ret = 0;
}
else
{
PrintKey( dvdcss, "initial disc key ", dvdcss->css.p_disc_key );
DecryptTitleKey( dvdcss->css.p_disc_key, p_key );
PrintKey( dvdcss, "decrypted title key ", p_key );
i_ret = 1;
}
/* All went well either there wasn't a key or we have it now. */
memcpy( p_title_key, p_key, KEY_SIZE );
PrintKey( dvdcss, "title key is ", p_title_key );
return i_ret;
}
/* The title key request failed */
print_debug( dvdcss, "resetting drive and cracking title key" );
/* Read an unscrambled sector and reset the drive */
dvdcss->pf_seek( dvdcss, 0 );
dvdcss->pf_read( dvdcss, p_garbage, 1 );
dvdcss->pf_seek( dvdcss, 0 );
_dvdcss_disckey( dvdcss );
/* Fallback */
}
/* METHOD is TITLE, we can't use the ioctls or requesting the title key
* failed above. For these cases we try to crack the key instead. */
/* For now, the read limit is 9Gb / 2048 = 4718592 sectors. */
i_ret = CrackTitleKey( dvdcss, i_pos, 4718592, p_key );
memcpy( p_title_key, p_key, KEY_SIZE );
PrintKey( dvdcss, "title key is ", p_title_key );
return i_ret;
}
/*****************************************************************************
* _dvdcss_unscramble: does the actual descrambling of data
*****************************************************************************
* sec : sector to unscramble
* key : title key for this sector
*****************************************************************************/
int _dvdcss_unscramble( dvd_key_t p_key, uint8_t *p_sec )
{
unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
uint8_t *p_end = p_sec + DVDCSS_BLOCK_SIZE;
/* PES_scrambling_control */
if( !(p_sec[0x14] & 0x30) )
{
return 0;
}
i_t1 = (p_key[0] ^ p_sec[0x54]) | 0x100;
i_t2 = p_key[1] ^ p_sec[0x55];
i_t3 = (p_key[2] | (p_key[3] << 8) |
(p_key[4] << 16)) ^ (p_sec[0x56] |
(p_sec[0x57] << 8) | (p_sec[0x58] << 16));
i_t4 = i_t3 & 7;
i_t3 = i_t3 * 2 + 8 - i_t4;
p_sec += 0x80;
i_t5 = 0;
while( p_sec != p_end )
{
i_t4 = p_css_tab2[i_t2] ^ p_css_tab3[i_t1];
i_t2 = i_t1>>1;
i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
i_t4 = p_css_tab5[i_t4];
i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
i_t3 = (i_t3 << 8 ) | i_t6;
i_t6 = p_css_tab4[i_t6];
i_t5 += i_t6 + i_t4;
*p_sec = p_css_tab1[*p_sec] ^ ( i_t5 & 0xff );
p_sec++;
i_t5 >>= 8;
}
return 0;
}
/* Following functions are local */
/*****************************************************************************
* GetBusKey : Go through the CSS Authentication process
*****************************************************************************
* It simulates the mutual authentication between logical unit and host,
* and stops when a session key (called bus key) has been established.
* Always do the full auth sequence. Some drives seem to lie and always
* respond with ASF=1. For instance the old DVD roms on Compaq Armada says
* that ASF=1 from the start and then later fail with a 'read of scrambled
* block without authentication' error.
*****************************************************************************/
static int GetBusKey( dvdcss_t dvdcss )
{
uint8_t p_buffer[10];
uint8_t p_challenge[2*KEY_SIZE];
dvd_key_t p_key1;
dvd_key_t p_key2;
dvd_key_t p_key_check;
uint8_t i_variant = 0;
int i_ret = -1;
int i;
print_debug( dvdcss, "requesting AGID" );
i_ret = ioctl_ReportAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
/* We might have to reset hung authentication processes in the drive
* by invalidating the corresponding AGID'. As long as we haven't got
* an AGID, invalidate one (in sequence) and try again. */
for( i = 0; i_ret == -1 && i < 4 ; ++i )
{
print_debug( dvdcss, "ioctl ReportAgid failed, "
"invalidating AGID %d", i );
/* This is really _not good_, should be handled by the OS.
* Invalidating an AGID could make another process fail somewhere
* in its authentication process. */
dvdcss->css.i_agid = i;
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
print_debug( dvdcss, "requesting AGID" );
i_ret = ioctl_ReportAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
}
/* Unable to authenticate without AGID */
if( i_ret == -1 )
{
print_error( dvdcss, "ioctl ReportAgid failed, fatal" );
return -1;
}
/* Setup a challenge, any values should work */
for( i = 0 ; i < 10; ++i )
{
p_challenge[i] = i;
}
/* Get challenge from host */
for( i = 0 ; i < 10 ; ++i )
{
p_buffer[9-i] = p_challenge[i];
}
/* Send challenge to LU */
if( ioctl_SendChallenge( dvdcss->i_fd,
&dvdcss->css.i_agid, p_buffer ) < 0 )
{
print_error( dvdcss, "ioctl SendChallenge failed" );
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
return -1;
}
/* Get key1 from LU */
if( ioctl_ReportKey1( dvdcss->i_fd, &dvdcss->css.i_agid, p_buffer ) < 0)
{
print_error( dvdcss, "ioctl ReportKey1 failed" );
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
return -1;
}
/* Send key1 to host */
for( i = 0 ; i < KEY_SIZE ; i++ )
{
p_key1[i] = p_buffer[4-i];
}
for( i = 0 ; i < 32 ; ++i )
{
CryptKey( 0, i, p_challenge, p_key_check );
if( memcmp( p_key_check, p_key1, KEY_SIZE ) == 0 )
{
print_debug( dvdcss, "drive authenticated, using variant %d", i );
i_variant = i;
break;
}
}
if( i == 32 )
{
print_error( dvdcss, "drive would not authenticate" );
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
return -1;
}
/* Get challenge from LU */
if( ioctl_ReportChallenge( dvdcss->i_fd,
&dvdcss->css.i_agid, p_buffer ) < 0 )
{
print_error( dvdcss, "ioctl ReportKeyChallenge failed" );
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
return -1;
}
/* Send challenge to host */
for( i = 0 ; i < 10 ; ++i )
{
p_challenge[i] = p_buffer[9-i];
}
CryptKey( 1, i_variant, p_challenge, p_key2 );
/* Get key2 from host */
for( i = 0 ; i < KEY_SIZE ; ++i )
{
p_buffer[4-i] = p_key2[i];
}
/* Send key2 to LU */
if( ioctl_SendKey2( dvdcss->i_fd, &dvdcss->css.i_agid, p_buffer ) < 0 )
{
print_error( dvdcss, "ioctl SendKey2 failed" );
ioctl_InvalidateAgid( dvdcss->i_fd, &dvdcss->css.i_agid );
return -1;
}
/* The drive has accepted us as authentic. */
print_debug( dvdcss, "authentication established" );
memcpy( p_challenge, p_key1, KEY_SIZE );
memcpy( p_challenge + KEY_SIZE, p_key2, KEY_SIZE );
CryptKey( 2, i_variant, p_challenge, dvdcss->css.p_bus_key );
return 0;
}
/*****************************************************************************
* PrintKey : debug function that dumps a key value
*****************************************************************************/
static void PrintKey( dvdcss_t dvdcss, char *prefix, uint8_t const *data )
{
print_debug( dvdcss, "%s%02x:%02x:%02x:%02x:%02x", prefix,
data[0], data[1], data[2], data[3], data[4] );
}
/*****************************************************************************
* GetASF : Get Authentication success flag
*****************************************************************************
* Returns :
* -1 on ioctl error,
* 0 if the device needs to be authenticated,
* 1 either.
*****************************************************************************/
static int GetASF( dvdcss_t dvdcss )
{
int i_asf = 0;
if( ioctl_ReportASF( dvdcss->i_fd, NULL, &i_asf ) != 0 )
{
/* The ioctl process has failed */
print_error( dvdcss, "GetASF fatal error" );
return -1;
}
if( i_asf )
{
print_debug( dvdcss, "GetASF authenticated, ASF=1" );
}
else
{
print_debug( dvdcss, "GetASF not authenticated, ASF=0" );
}
return i_asf;
}
/*****************************************************************************
* CryptKey : shuffles bits and unencrypt keys.
*****************************************************************************
* Used during authentication and disc key negociation in GetBusKey.
* i_key_type : 0->key1, 1->key2, 2->buskey.
* i_variant : between 0 and 31.
*****************************************************************************/
static void CryptKey( int i_key_type, int i_variant,
uint8_t const *p_challenge, uint8_t *p_key )
{
/* Permutation table for challenge */
uint8_t pp_perm_challenge[3][10] =
{ { 1, 3, 0, 7, 5, 2, 9, 6, 4, 8 },
{ 6, 1, 9, 3, 8, 5, 7, 4, 0, 2 },
{ 4, 0, 3, 5, 7, 2, 8, 6, 1, 9 } };
/* Permutation table for variant table for key2 and buskey */
uint8_t pp_perm_variant[2][32] =
{ { 0x0a, 0x08, 0x0e, 0x0c, 0x0b, 0x09, 0x0f, 0x0d,
0x1a, 0x18, 0x1e, 0x1c, 0x1b, 0x19, 0x1f, 0x1d,
0x02, 0x00, 0x06, 0x04, 0x03, 0x01, 0x07, 0x05,
0x12, 0x10, 0x16, 0x14, 0x13, 0x11, 0x17, 0x15 },
{ 0x12, 0x1a, 0x16, 0x1e, 0x02, 0x0a, 0x06, 0x0e,
0x10, 0x18, 0x14, 0x1c, 0x00, 0x08, 0x04, 0x0c,
0x13, 0x1b, 0x17, 0x1f, 0x03, 0x0b, 0x07, 0x0f,
0x11, 0x19, 0x15, 0x1d, 0x01, 0x09, 0x05, 0x0d } };
uint8_t p_variants[32] =
{ 0xB7, 0x74, 0x85, 0xD0, 0xCC, 0xDB, 0xCA, 0x73,
0x03, 0xFE, 0x31, 0x03, 0x52, 0xE0, 0xB7, 0x42,
0x63, 0x16, 0xF2, 0x2A, 0x79, 0x52, 0xFF, 0x1B,
0x7A, 0x11, 0xCA, 0x1A, 0x9B, 0x40, 0xAD, 0x01 };
/* The "secret" key */
uint8_t p_secret[5] = { 0x55, 0xD6, 0xC4, 0xC5, 0x28 };
uint8_t p_bits[30], p_scratch[10], p_tmp1[5], p_tmp2[5];
uint8_t i_lfsr0_o; /* 1 bit used */
uint8_t i_lfsr1_o; /* 1 bit used */
uint8_t i_css_variant, i_cse, i_index, i_combined, i_carry;
uint8_t i_val = 0;
uint32_t i_lfsr0, i_lfsr1;
int i_term = 0;
int i_bit;
int i;
for (i = 9; i >= 0; --i)
p_scratch[i] = p_challenge[pp_perm_challenge[i_key_type][i]];
i_css_variant = ( i_key_type == 0 ) ? i_variant :
pp_perm_variant[i_key_type-1][i_variant];
/*
* This encryption engine implements one of 32 variations
* one the same theme depending upon the choice in the
* variant parameter (0 - 31).
*
* The algorithm itself manipulates a 40 bit input into
* a 40 bit output.
* The parameter 'input' is 80 bits. It consists of
* the 40 bit input value that is to be encrypted followed
* by a 40 bit seed value for the pseudo random number
* generators.
*/
/* Feed the secret into the input values such that
* we alter the seed to the LFSR's used above, then
* generate the bits to play with.
*/
for( i = 5 ; --i >= 0 ; )
{
p_tmp1[i] = p_scratch[5 + i] ^ p_secret[i] ^ p_crypt_tab2[i];
}
/*
* We use two LFSR's (seeded from some of the input data bytes) to
* generate two streams of pseudo-random bits. These two bit streams
* are then combined by simply adding with carry to generate a final
* sequence of pseudo-random bits which is stored in the buffer that
* 'output' points to the end of - len is the size of this buffer.
*
* The first LFSR is of degree 25, and has a polynomial of:
* x^13 + x^5 + x^4 + x^1 + 1
*
* The second LSFR is of degree 17, and has a (primitive) polynomial of:
* x^15 + x^1 + 1
*
* I don't know if these polynomials are primitive modulo 2, and thus
* represent maximal-period LFSR's.
*
*
* Note that we take the output of each LFSR from the new shifted in
* bit, not the old shifted out bit. Thus for ease of use the LFSR's
* are implemented in bit reversed order.
*
*/
/* In order to ensure that the LFSR works we need to ensure that the
* initial values are non-zero. Thus when we initialise them from
* the seed, we ensure that a bit is set.
*/
i_lfsr0 = ( p_tmp1[0] << 17 ) | ( p_tmp1[1] << 9 ) |
(( p_tmp1[2] & ~7 ) << 1 ) | 8 | ( p_tmp1[2] & 7 );
i_lfsr1 = ( p_tmp1[3] << 9 ) | 0x100 | p_tmp1[4];
i_index = sizeof(p_bits);
i_carry = 0;
do
{
for( i_bit = 0, i_val = 0 ; i_bit < 8 ; ++i_bit )
{
i_lfsr0_o = ( ( i_lfsr0 >> 24 ) ^ ( i_lfsr0 >> 21 ) ^
( i_lfsr0 >> 20 ) ^ ( i_lfsr0 >> 12 ) ) & 1;
i_lfsr0 = ( i_lfsr0 << 1 ) | i_lfsr0_o;
i_lfsr1_o = ( ( i_lfsr1 >> 16 ) ^ ( i_lfsr1 >> 2 ) ) & 1;
i_lfsr1 = ( i_lfsr1 << 1 ) | i_lfsr1_o;
i_combined = !i_lfsr1_o + i_carry + !i_lfsr0_o;
/* taking bit 1 */
i_carry = ( i_combined >> 1 ) & 1;
i_val |= ( i_combined & 1 ) << i_bit;
}
p_bits[--i_index] = i_val;
} while( i_index > 0 );
/* This term is used throughout the following to
* select one of 32 different variations on the
* algorithm.
*/
i_cse = p_variants[i_css_variant] ^ p_crypt_tab2[i_css_variant];
/* Now the actual blocks doing the encryption. Each
* of these works on 40 bits at a time and are quite
* similar.
*/
i_index = 0;
for( i = 5, i_term = 0 ; --i >= 0 ; i_term = p_scratch[i] )
{
i_index = p_bits[25 + i] ^ p_scratch[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
p_tmp1[i] = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
}
p_tmp1[4] ^= p_tmp1[0];
for( i = 5, i_term = 0 ; --i >= 0 ; i_term = p_tmp1[i] )
{
i_index = p_bits[20 + i] ^ p_tmp1[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
p_tmp2[i] = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
}
p_tmp2[4] ^= p_tmp2[0];
for( i = 5, i_term = 0 ; --i >= 0 ; i_term = p_tmp2[i] )
{
i_index = p_bits[15 + i] ^ p_tmp2[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
i_index = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
p_tmp1[i] = p_crypt_tab0[i_index] ^ p_crypt_tab2[i_index];
}
p_tmp1[4] ^= p_tmp1[0];
for( i = 5, i_term = 0 ; --i >= 0 ; i_term = p_tmp1[i] )
{
i_index = p_bits[10 + i] ^ p_tmp1[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
i_index = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
p_tmp2[i] = p_crypt_tab0[i_index] ^ p_crypt_tab2[i_index];
}
p_tmp2[4] ^= p_tmp2[0];
for( i = 5, i_term = 0 ; --i >= 0 ; i_term = p_tmp2[i] )
{
i_index = p_bits[5 + i] ^ p_tmp2[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
p_tmp1[i] = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
}
p_tmp1[4] ^= p_tmp1[0];
for(i = 5, i_term = 0 ; --i >= 0 ; i_term = p_tmp1[i] )
{
i_index = p_bits[i] ^ p_tmp1[i];
i_index = p_crypt_tab1[i_index] ^ ~p_crypt_tab2[i_index] ^ i_cse;
p_key[i] = p_crypt_tab2[i_index] ^ p_crypt_tab3[i_index] ^ i_term;
}
return;
}
/*****************************************************************************
* DecryptKey: decrypt p_crypted with p_key.
*****************************************************************************
* Used to decrypt the disc key, with a player key, after requesting it
* in _dvdcss_disckey and to decrypt title keys, with a disc key, requested
* in _dvdcss_titlekey.
* The player keys and the resulting disc key are only used as KEKs
* (key encryption keys).
* Decryption is slightly dependant on the type of key:
* -for disc key, invert is 0x00,
* -for title key, invert if 0xff.
*****************************************************************************/
static void DecryptKey( uint8_t invert, uint8_t const *p_key,
uint8_t const *p_crypted, uint8_t *p_result )
{
unsigned int i_lfsr1_lo;
unsigned int i_lfsr1_hi;
unsigned int i_lfsr0;
unsigned int i_combined;
uint8_t o_lfsr0;
uint8_t o_lfsr1;
uint8_t k[5];
int i;
i_lfsr1_lo = p_key[0] | 0x100;
i_lfsr1_hi = p_key[1];
i_lfsr0 = ( ( p_key[4] << 17 )
| ( p_key[3] << 9 )
| ( p_key[2] << 1 ) )
+ 8 - ( p_key[2] & 7 );
i_lfsr0 = ( p_css_tab4[i_lfsr0 & 0xff] << 24 ) |
( p_css_tab4[( i_lfsr0 >> 8 ) & 0xff] << 16 ) |
( p_css_tab4[( i_lfsr0 >> 16 ) & 0xff] << 8 ) |
p_css_tab4[( i_lfsr0 >> 24 ) & 0xff];
i_combined = 0;
for( i = 0 ; i < KEY_SIZE ; ++i )
{
o_lfsr1 = p_css_tab2[i_lfsr1_hi] ^ p_css_tab3[i_lfsr1_lo];
i_lfsr1_hi = i_lfsr1_lo >> 1;
i_lfsr1_lo = ( ( i_lfsr1_lo & 1 ) << 8 ) ^ o_lfsr1;
o_lfsr1 = p_css_tab4[o_lfsr1];
o_lfsr0 = ((((((( i_lfsr0 >> 8 ) ^ i_lfsr0 ) >> 1 )
^ i_lfsr0 ) >> 3 ) ^ i_lfsr0 ) >> 7 );
i_lfsr0 = ( i_lfsr0 >> 8 ) | ( o_lfsr0 << 24 );
i_combined += ( o_lfsr0 ^ invert ) + o_lfsr1;
k[i] = i_combined & 0xff;
i_combined >>= 8;
}
p_result[4] = k[4] ^ p_css_tab1[p_crypted[4]] ^ p_crypted[3];
p_result[3] = k[3] ^ p_css_tab1[p_crypted[3]] ^ p_crypted[2];
p_result[2] = k[2] ^ p_css_tab1[p_crypted[2]] ^ p_crypted[1];
p_result[1] = k[1] ^ p_css_tab1[p_crypted[1]] ^ p_crypted[0];
p_result[0] = k[0] ^ p_css_tab1[p_crypted[0]] ^ p_result[4];
p_result[4] = k[4] ^ p_css_tab1[p_result[4]] ^ p_result[3];
p_result[3] = k[3] ^ p_css_tab1[p_result[3]] ^ p_result[2];
p_result[2] = k[2] ^ p_css_tab1[p_result[2]] ^ p_result[1];
p_result[1] = k[1] ^ p_css_tab1[p_result[1]] ^ p_result[0];
p_result[0] = k[0] ^ p_css_tab1[p_result[0]];
return;
}
/*****************************************************************************
* player_keys: alternate DVD player keys
*****************************************************************************
* These player keys were generated using Frank A. Stevenson's PlayerKey
* cracker. A copy of his article can be found here:
* http://www-2.cs.cmu.edu/~dst/DeCSS/FrankStevenson/mail2.txt
*****************************************************************************/
static const dvd_key_t player_keys[] =
{
{ 0x01, 0xaf, 0xe3, 0x12, 0x80 },
{ 0x12, 0x11, 0xca, 0x04, 0x3b },
{ 0x14, 0x0c, 0x9e, 0xd0, 0x09 },
{ 0x14, 0x71, 0x35, 0xba, 0xe2 },
{ 0x1a, 0xa4, 0x33, 0x21, 0xa6 },
{ 0x26, 0xec, 0xc4, 0xa7, 0x4e },
{ 0x2c, 0xb2, 0xc1, 0x09, 0xee },
{ 0x2f, 0x25, 0x9e, 0x96, 0xdd },
{ 0x33, 0x2f, 0x49, 0x6c, 0xe0 },
{ 0x35, 0x5b, 0xc1, 0x31, 0x0f },
{ 0x36, 0x67, 0xb2, 0xe3, 0x85 },
{ 0x39, 0x3d, 0xf1, 0xf1, 0xbd },
{ 0x3b, 0x31, 0x34, 0x0d, 0x91 },
{ 0x45, 0xed, 0x28, 0xeb, 0xd3 },
{ 0x48, 0xb7, 0x6c, 0xce, 0x69 },
{ 0x4b, 0x65, 0x0d, 0xc1, 0xee },
{ 0x4c, 0xbb, 0xf5, 0x5b, 0x23 },
{ 0x51, 0x67, 0x67, 0xc5, 0xe0 },
{ 0x53, 0x94, 0xe1, 0x75, 0xbf },
{ 0x57, 0x2c, 0x8b, 0x31, 0xae },
{ 0x63, 0xdb, 0x4c, 0x5b, 0x4a },
{ 0x7b, 0x1e, 0x5e, 0x2b, 0x57 },
{ 0x85, 0xf3, 0x85, 0xa0, 0xe0 },
{ 0xab, 0x1e, 0xe7, 0x7b, 0x72 },
{ 0xab, 0x36, 0xe3, 0xeb, 0x76 },
{ 0xb1, 0xb8, 0xf9, 0x38, 0x03 },
{ 0xb8, 0x5d, 0xd8, 0x53, 0xbd },
{ 0xbf, 0x92, 0xc3, 0xb0, 0xe2 },
{ 0xcf, 0x1a, 0xb2, 0xf8, 0x0a },
{ 0xec, 0xa0, 0xcf, 0xb3, 0xff },
{ 0xfc, 0x95, 0xa9, 0x87, 0x35 }
};
/*****************************************************************************
* DecryptDiscKey
*****************************************************************************
* Decryption of the disc key with player keys: try to decrypt the disc key
* from every position with every player key.
* p_struct_disckey: the 2048 byte DVD_STRUCT_DISCKEY data
* p_disc_key: result, the 5 byte disc key
*****************************************************************************/
static int DecryptDiscKey( dvdcss_t dvdcss, uint8_t const *p_struct_disckey,
dvd_key_t p_disc_key )
{
uint8_t p_verify[KEY_SIZE];
unsigned int i, n = 0;
/* Decrypt disc key with the above player keys */
for( n = 0; n < sizeof(player_keys) / sizeof(dvd_key_t); n++ )
{
PrintKey( dvdcss, "trying player key ", player_keys[n] );
for( i = 1; i < 409; i++ )
{
/* Check if player key n is the right key for position i. */
DecryptKey( 0, player_keys[n], p_struct_disckey + 5 * i,
p_disc_key );
/* The first part in the struct_disckey block is the
* 'disc key' encrypted with itself. Using this we
* can check if we decrypted the correct key. */
DecryptKey( 0, p_disc_key, p_struct_disckey, p_verify );
/* If the position / player key pair worked then return. */
if( memcmp( p_disc_key, p_verify, KEY_SIZE ) == 0 )
{
return 0;
}
}
}
/* Have tried all combinations of positions and keys,
* and we still didn't succeed. */
memset( p_disc_key, 0, KEY_SIZE );
return -1;
}
/*****************************************************************************
* DecryptTitleKey
*****************************************************************************
* Decrypt the title key using the disc key.
* p_disc_key: result, the 5 byte disc key
* p_titlekey: the encrypted title key, gets overwritten by the decrypted key
*****************************************************************************/
static void DecryptTitleKey( dvd_key_t p_disc_key, dvd_key_t p_titlekey )
{
DecryptKey( 0xff, p_disc_key, p_titlekey, p_titlekey );
}
/*****************************************************************************
* CrackDiscKey: brute force disc key
* CSS hash reversal function designed by Frank Stevenson
*****************************************************************************
* This function uses a big amount of memory to crack the disc key from the
* disc key hash, if player keys are not available.
*****************************************************************************/
#define K1TABLEWIDTH 10
/*
* Simple function to test if a candidate key produces the given hash
*/
static int investigate( unsigned char *hash, unsigned char *ckey )
{
unsigned char key[KEY_SIZE];
DecryptKey( 0, ckey, hash, key );
return memcmp( key, ckey, KEY_SIZE );
}
static int CrackDiscKey( dvdcss_t dvdcss, uint8_t *p_disc_key )
{
unsigned char B[5] = { 0,0,0,0,0 }; /* Second Stage of mangle cipher */
unsigned char C[5] = { 0,0,0,0,0 }; /* Output Stage of mangle cipher
* IntermediateKey */
unsigned char k[5] = { 0,0,0,0,0 }; /* Mangling cipher key
* Also output from CSS( C ) */
unsigned char out1[5]; /* five first output bytes of LFSR1 */
unsigned char out2[5]; /* five first output bytes of LFSR2 */
unsigned int lfsr1a; /* upper 9 bits of LFSR1 */
unsigned int lfsr1b; /* lower 8 bits of LFSR1 */
unsigned int tmp, tmp2, tmp3, tmp4,tmp5;
int i,j;
unsigned int nStepA; /* iterator for LFSR1 start state */
unsigned int nStepB; /* iterator for possible B[0] */
unsigned int nTry; /* iterator for K[1] possibilities */
unsigned int nPossibleK1; /* #of possible K[1] values */
unsigned char* K1table; /* Lookup table for possible K[1] */
unsigned int* BigTable; /* LFSR2 startstate indexed by
* 1,2,5 output byte */
/*
* Prepare tables for hash reversal
*/
/* initialize lookup tables for k[1] */
K1table = malloc( 65536 * K1TABLEWIDTH );
memset( K1table, 0 , 65536 * K1TABLEWIDTH );
if( K1table == NULL )
{
return -1;
}
tmp = p_disc_key[0] ^ p_css_tab1[ p_disc_key[1] ];
for( i = 0 ; i < 256 ; i++ ) /* k[1] */
{
tmp2 = p_css_tab1[ tmp ^ i ]; /* p_css_tab1[ B[1] ]*/
for( j = 0 ; j < 256 ; j++ ) /* B[0] */
{
tmp3 = j ^ tmp2 ^ i; /* C[1] */
tmp4 = K1table[ K1TABLEWIDTH * ( 256 * j + tmp3 ) ]; /* count of entries here */
tmp4++;
/*
if( tmp4 == K1TABLEWIDTH )
{
print_debug( dvdcss, "Table disaster %d", tmp4 );
}
*/
if( tmp4 < K1TABLEWIDTH )
{
K1table[ K1TABLEWIDTH * ( 256 * j + tmp3 ) + tmp4 ] = i;
}
K1table[ K1TABLEWIDTH * ( 256 * j + tmp3 ) ] = tmp4;
}
}
/* Initing our Really big table */
BigTable = malloc( 16777216 * sizeof(int) );
memset( BigTable, 0 , 16777216 * sizeof(int) );
if( BigTable == NULL )
{
free( K1table );
return -1;
}
tmp3 = 0;
print_debug( dvdcss, "initializing the big table" );
for( i = 0 ; i < 16777216 ; i++ )
{
tmp = (( i + i ) & 0x1fffff0 ) | 0x8 | ( i & 0x7 );
for( j = 0 ; j < 5 ; j++ )
{
tmp2=((((((( tmp >> 3 ) ^ tmp ) >> 1 ) ^ tmp ) >> 8 )
^ tmp ) >> 5 ) & 0xff;
tmp = ( tmp << 8) | tmp2;
out2[j] = p_css_tab4[ tmp2 ];
}
j = ( out2[0] << 16 ) | ( out2[1] << 8 ) | out2[4];
BigTable[j] = i;
}
/*
* We are done initing, now reverse hash
*/
tmp5 = p_disc_key[0] ^ p_css_tab1[ p_disc_key[1] ];
for( nStepA = 0 ; nStepA < 65536 ; nStepA ++ )
{
lfsr1a = 0x100 | ( nStepA >> 8 );
lfsr1b = nStepA & 0xff;
/* Generate 5 first output bytes from lfsr1 */
for( i = 0 ; i < 5 ; i++ )
{
tmp = p_css_tab2[ lfsr1b ] ^ p_css_tab3[ lfsr1a ];
lfsr1b = lfsr1a >> 1;
lfsr1a = ((lfsr1a&1)<<8) ^ tmp;
out1[ i ] = p_css_tab4[ tmp ];
}
/* cumpute and cache some variables */
C[0] = nStepA >> 8;
C[1] = nStepA & 0xff;
tmp = p_disc_key[3] ^ p_css_tab1[ p_disc_key[4] ];
tmp2 = p_css_tab1[ p_disc_key[0] ];
/* Search through all possible B[0] */
for( nStepB = 0 ; nStepB < 256 ; nStepB++ )
{
/* reverse parts of the mangling cipher */
B[0] = nStepB;
k[0] = p_css_tab1[ B[0] ] ^ C[0];
B[4] = B[0] ^ k[0] ^ tmp2;
k[4] = B[4] ^ tmp;
nPossibleK1 = K1table[ K1TABLEWIDTH * (256 * B[0] + C[1]) ];
/* Try out all possible values for k[1] */
for( nTry = 0 ; nTry < nPossibleK1 ; nTry++ )
{
k[1] = K1table[ K1TABLEWIDTH * (256 * B[0] + C[1]) + nTry + 1 ];
B[1] = tmp5 ^ k[1];
/* reconstruct output from LFSR2 */
tmp3 = ( 0x100 + k[0] - out1[0] );
out2[0] = tmp3 & 0xff;
tmp3 = tmp3 & 0x100 ? 0x100 : 0xff;
tmp3 = ( tmp3 + k[1] - out1[1] );
out2[1] = tmp3 & 0xff;
tmp3 = ( 0x100 + k[4] - out1[4] );
out2[4] = tmp3 & 0xff; /* Can be 1 off */
/* test first possible out2[4] */
tmp4 = ( out2[0] << 16 ) | ( out2[1] << 8 ) | out2[4];
tmp4 = BigTable[ tmp4 ];
C[2] = tmp4 & 0xff;
C[3] = ( tmp4 >> 8 ) & 0xff;
C[4] = ( tmp4 >> 16 ) & 0xff;
B[3] = p_css_tab1[ B[4] ] ^ k[4] ^ C[4];
k[3] = p_disc_key[2] ^ p_css_tab1[ p_disc_key[3] ] ^ B[3];
B[2] = p_css_tab1[ B[3] ] ^ k[3] ^ C[3];
k[2] = p_disc_key[1] ^ p_css_tab1[ p_disc_key[2] ] ^ B[2];
if( ( B[1] ^ p_css_tab1[ B[2] ] ^ k[ 2 ] ) == C[ 2 ] )
{
if( ! investigate( &p_disc_key[0] , &C[0] ) )
{
goto end;
}
}
/* Test second possible out2[4] */
out2[4] = ( out2[4] + 0xff ) & 0xff;
tmp4 = ( out2[0] << 16 ) | ( out2[1] << 8 ) | out2[4];
tmp4 = BigTable[ tmp4 ];
C[2] = tmp4 & 0xff;
C[3] = ( tmp4 >> 8 ) & 0xff;
C[4] = ( tmp4 >> 16 ) & 0xff;
B[3] = p_css_tab1[ B[4] ] ^ k[4] ^ C[4];
k[3] = p_disc_key[2] ^ p_css_tab1[ p_disc_key[3] ] ^ B[3];
B[2] = p_css_tab1[ B[3] ] ^ k[3] ^ C[3];
k[2] = p_disc_key[1] ^ p_css_tab1[ p_disc_key[2] ] ^ B[2];
if( ( B[1] ^ p_css_tab1[ B[2] ] ^ k[ 2 ] ) == C[ 2 ] )
{
if( ! investigate( &p_disc_key[0] , &C[0] ) )
{
goto end;
}
}
}
}
}
end:
memcpy( p_disc_key, &C[0], KEY_SIZE );
free( K1table );
free( BigTable );
return 0;
}
/*****************************************************************************
* RecoverTitleKey: (title) key recovery from cipher and plain text
* Function designed by Frank Stevenson
*****************************************************************************
* Called from Attack* which are in turn called by CrackTitleKey. Given
* a guessed(?) plain text and the cipher text. Returns -1 on failure.
*****************************************************************************/
static int RecoverTitleKey( int i_start, uint8_t const *p_crypted,
uint8_t const *p_decrypted,
uint8_t const *p_sector_seed, uint8_t *p_key )
{
uint8_t p_buffer[10];
unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
unsigned int i_try;
unsigned int i_candidate;
unsigned int i, j;
int i_exit = -1;
for( i = 0 ; i < 10 ; i++ )
{
p_buffer[i] = p_css_tab1[p_crypted[i]] ^ p_decrypted[i];
}
for( i_try = i_start ; i_try < 0x10000 ; i_try++ )
{
i_t1 = i_try >> 8 | 0x100;
i_t2 = i_try & 0xff;
i_t3 = 0; /* not needed */
i_t5 = 0;
/* iterate cipher 4 times to reconstruct LFSR2 */
for( i = 0 ; i < 4 ; i++ )
{
/* advance LFSR1 normaly */
i_t4 = p_css_tab2[i_t2] ^ p_css_tab3[i_t1];
i_t2 = i_t1 >> 1;
i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
i_t4 = p_css_tab5[i_t4];
/* deduce i_t6 & i_t5 */
i_t6 = p_buffer[i];
if( i_t5 )
{
i_t6 = ( i_t6 + 0xff ) & 0x0ff;
}
if( i_t6 < i_t4 )
{
i_t6 += 0x100;
}
i_t6 -= i_t4;
i_t5 += i_t6 + i_t4;
i_t6 = p_css_tab4[ i_t6 ];
/* feed / advance i_t3 / i_t5 */
i_t3 = ( i_t3 << 8 ) | i_t6;
i_t5 >>= 8;
}
i_candidate = i_t3;
/* iterate 6 more times to validate candidate key */
for( ; i < 10 ; i++ )
{
i_t4 = p_css_tab2[i_t2] ^ p_css_tab3[i_t1];
i_t2 = i_t1 >> 1;
i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
i_t4 = p_css_tab5[i_t4];
i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
i_t3 = ( i_t3 << 8 ) | i_t6;
i_t6 = p_css_tab4[i_t6];
i_t5 += i_t6 + i_t4;
if( ( i_t5 & 0xff ) != p_buffer[i] )
{
break;
}
i_t5 >>= 8;
}
if( i == 10 )
{
/* Do 4 backwards steps of iterating t3 to deduce initial state */
i_t3 = i_candidate;
for( i = 0 ; i < 4 ; i++ )
{
i_t1 = i_t3 & 0xff;
i_t3 = ( i_t3 >> 8 );
/* easy to code, and fast enough bruteforce
* search for byte shifted in */
for( j = 0 ; j < 256 ; j++ )
{
i_t3 = ( i_t3 & 0x1ffff ) | ( j << 17 );
i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
if( i_t6 == i_t1 )
{
break;
}
}
}
i_t4 = ( i_t3 >> 1 ) - 4;
for( i_t5 = 0 ; i_t5 < 8; i_t5++ )
{
if( ( ( i_t4 + i_t5 ) * 2 + 8 - ( (i_t4 + i_t5 ) & 7 ) )
== i_t3 )
{
p_key[0] = i_try>>8;
p_key[1] = i_try & 0xFF;
p_key[2] = ( ( i_t4 + i_t5 ) >> 0 ) & 0xFF;
p_key[3] = ( ( i_t4 + i_t5 ) >> 8 ) & 0xFF;
p_key[4] = ( ( i_t4 + i_t5 ) >> 16 ) & 0xFF;
i_exit = i_try + 1;
}
}
}
}
if( i_exit >= 0 )
{
p_key[0] ^= p_sector_seed[0];
p_key[1] ^= p_sector_seed[1];
p_key[2] ^= p_sector_seed[2];
p_key[3] ^= p_sector_seed[3];
p_key[4] ^= p_sector_seed[4];
}
return i_exit;
}
/******************************************************************************
* Various pieces for the title crack engine.
******************************************************************************
* The length of the PES packet is located at 0x12-0x13.
* The the copyrigth protection bits are located at 0x14 (bits 0x20 and 0x10).
* The data of the PES packet begins at 0x15 (if there isn't any PTS/DTS)
* or at 0x?? if there are both PTS and DTS's.
* The seed value used with the unscrambling key is the 5 bytes at 0x54-0x58.
* The scrabled part of a sector begins at 0x80.
*****************************************************************************/
/* Statistics */
static int i_tries = 0, i_success = 0;
/*****************************************************************************
* CrackTitleKey: try to crack title key from the contents of a VOB.
*****************************************************************************
* This function is called by _dvdcss_titlekey to find a title key, if we've
* chosen to crack title key instead of decrypting it with the disc key.
* The DVD should have been opened and be in an authenticated state.
* i_pos is the starting sector, i_len is the maximum number of sectors to read
*****************************************************************************/
static int CrackTitleKey( dvdcss_t dvdcss, int i_pos, int i_len,
dvd_key_t p_titlekey )
{
uint8_t p_buf[ DVDCSS_BLOCK_SIZE ];
const uint8_t p_packstart[4] = { 0x00, 0x00, 0x01, 0xba };
int i_reads = 0;
int i_encrypted = 0;
int b_stop_scanning = 0;
int b_read_error = 0;
int i_ret;
print_debug( dvdcss, "cracking title key at block %i", i_pos );
i_tries = 0;
i_success = 0;
do
{
i_ret = dvdcss->pf_seek( dvdcss, i_pos );
if( i_ret != i_pos )
{
print_error( dvdcss, "seek failed" );
}
i_ret = dvdcss_read( dvdcss, p_buf, 1, DVDCSS_NOFLAGS );
/* Either we are at the end of the physical device or the auth
* have failed / were not done and we got a read error. */
if( i_ret <= 0 )
{
if( i_ret == 0 )
{
print_debug( dvdcss, "read returned 0 (end of device?)" );
}
else if( !b_read_error )
{
print_debug( dvdcss, "read error at block %i, resorting to "
"secret arcanes to recover", i_pos );
/* Reset the drive before trying to continue */
_dvdcss_close( dvdcss );
_dvdcss_open( dvdcss );
b_read_error = 1;
continue;
}
break;
}
/* Stop when we find a non MPEG stream block.
* (We must have reached the end of the stream).
* For now, allow all blocks that begin with a start code. */
if( memcmp( p_buf, p_packstart, 3 ) )
{
print_debug( dvdcss, "non MPEG block found at block %i "
"(end of title)", i_pos );
break;
}
if( p_buf[0x0d] & 0x07 )
print_debug( dvdcss, "stuffing in pack header" );
/* PES_scrambling_control does not exist in a system_header,
* a padding_stream or a private_stream2 (and others?). */
if( p_buf[0x14] & 0x30 && ! ( p_buf[0x11] == 0xbb
|| p_buf[0x11] == 0xbe
|| p_buf[0x11] == 0xbf ) )
{
i_encrypted++;
if( AttackPattern(p_buf, i_reads, p_titlekey) > 0 )
{
b_stop_scanning = 1;
}
#if 0
if( AttackPadding(p_buf, i_reads, p_titlekey) > 0 )
{
b_stop_scanning = 1;
}
#endif
}
i_pos++;
i_len--;
i_reads++;
/* Emit a progress indication now and then. */
if( !( i_reads & 0xfff ) )
{
print_debug( dvdcss, "at block %i, still cracking...", i_pos );
}
/* Stop after 2000 blocks if we haven't seen any encrypted blocks. */
if( i_reads >= 2000 && i_encrypted == 0 ) break;
} while( !b_stop_scanning && i_len > 0);
if( !b_stop_scanning )
{
print_debug( dvdcss, "end of title reached" );
}
/* Print some statistics. */
print_debug( dvdcss, "successful attempts %d/%d, scrambled blocks %d/%d",
i_success, i_tries, i_encrypted, i_reads );
if( i_success > 0 /* b_stop_scanning */ )
{
print_debug( dvdcss, "vts key initialized" );
return 1;
}
if( i_encrypted == 0 && i_reads > 0 )
{
memset( p_titlekey, 0, KEY_SIZE );
print_debug( dvdcss, "no scrambled sectors found" );
return 0;
}
memset( p_titlekey, 0, KEY_SIZE );
return -1;
}
/******************************************************************************
* The original Ethan Hawke (DeCSSPlus) attack (modified).
******************************************************************************
* Tries to find a repeating pattern just before the encrypted part starts.
* Then it guesses that the plain text for first encrypted bytes are
* a contiuation of that pattern.
*****************************************************************************/
static int AttackPattern( uint8_t const p_sec[ DVDCSS_BLOCK_SIZE ],
int i_pos, uint8_t *p_key )
{
unsigned int i_best_plen = 0;
unsigned int i_best_p = 0;
unsigned int i, j;
/* For all cycle length from 2 to 48 */
for( i = 2 ; i < 0x30 ; i++ )
{
/* Find the number of bytes that repeats in cycles. */
for( j = i + 1;
j < 0x80 && ( p_sec[0x7F - (j%i)] == p_sec[0x7F - j] );
j++ )
{
/* We have found j repeating bytes with a cycle length i. */
if( j > i_best_plen )
{
i_best_plen = j;
i_best_p = i;
}
}
}
/* We need at most 10 plain text bytes?, so a make sure that we
* have at least 20 repeated bytes and that they have cycled at
* least one time. */
if( ( i_best_plen > 3 ) && ( i_best_plen / i_best_p >= 2) )
{
int res;
i_tries++;
memset( p_key, 0, KEY_SIZE );
res = RecoverTitleKey( 0, &p_sec[0x80],
&p_sec[ 0x80 - (i_best_plen / i_best_p) * i_best_p ],
&p_sec[0x54] /* key_seed */, p_key );
i_success += ( res >= 0 );
#if 0
if( res >= 0 )
{
fprintf( stderr, "key is %02x:%02x:%02x:%02x:%02x ",
p_key[0], p_key[1], p_key[2], p_key[3], p_key[4] );
fprintf( stderr, "at block %5d pattern len %3d period %3d %s\n",
i_pos, i_best_plen, i_best_p, (res>=0?"y":"n") );
}
#endif
return ( res >= 0 );
}
return 0;
}
#if 0
/******************************************************************************
* Encrypted Padding_stream attack.
******************************************************************************
* DVD specifies that there must only be one type of data in every sector.
* Every sector is one pack and so must obviously be 2048 bytes long.
* For the last pice of video data before a VOBU boundary there might not
* be exactly the right amount of data to fill a sector. Then one has to
* pad the pack to 2048 bytes. For just a few bytes this is done in the
* header but for any large amount you insert a PES packet from the
* Padding stream. This looks like 0x00 00 01 be xx xx ff ff ...
* where xx xx is the length of the padding stream.
*****************************************************************************/
static int AttackPadding( uint8_t const p_sec[ DVDCSS_BLOCK_SIZE ],
int i_pos, uint8_t *p_key )
{
unsigned int i_pes_length;
/*static int i_tries = 0, i_success = 0;*/
i_pes_length = (p_sec[0x12]<<8) | p_sec[0x13];
/* Coverd by the test below but usfull for debuging. */
if( i_pes_length == DVDCSS_BLOCK_SIZE - 0x14 ) return 0;
/* There must be room for at least 4? bytes of padding stream,
* and it must be encrypted.
* sector size - pack/pes header - padding startcode - padding length */
if( ( DVDCSS_BLOCK_SIZE - 0x14 - 4 - 2 - i_pes_length < 4 ) ||
( p_sec[0x14 + i_pes_length + 0] == 0x00 &&
p_sec[0x14 + i_pes_length + 1] == 0x00 &&
p_sec[0x14 + i_pes_length + 2] == 0x01 ) )
{
fprintf( stderr, "plain %d %02x:%02x:%02x:%02x (type %02x sub %02x)\n",
DVDCSS_BLOCK_SIZE - 0x14 - 4 - 2 - i_pes_length,
p_sec[0x14 + i_pes_length + 0],
p_sec[0x14 + i_pes_length + 1],
p_sec[0x14 + i_pes_length + 2],
p_sec[0x14 + i_pes_length + 3],
p_sec[0x11], p_sec[0x17 + p_sec[0x16]]);
return 0;
}
/* If we are here we know that there is a where in the pack a
encrypted PES header is (startcode + length). It's never more
than two packets in the pack, so we 'know' the length. The
plaintext at offset (0x14 + i_pes_length) will then be
00 00 01 e0/bd/be xx xx, in the case of be the following bytes
are also known. */
/* An encrypted SPU PES packet with another encrypted PES packet following.
Normaly if the following was a padding stream that would be in plain
text. So it will be another SPU PES packet. */
if( p_sec[0x11] == 0xbd &&
p_sec[0x17 + p_sec[0x16]] >= 0x20 &&
p_sec[0x17 + p_sec[0x16]] <= 0x3f )
{
i_tries++;
}
/* A Video PES packet with another encrypted PES packet following.
* No reason execpt for time stamps to break the data into two packets.
* So it's likely that the following PES packet is a padding stream. */
if( p_sec[0x11] == 0xe0 )
{
i_tries++;
}
if( 1 )
{
/*fprintf( stderr, "key is %02x:%02x:%02x:%02x:%02x ",
p_key[0], p_key[1], p_key[2], p_key[3], p_key[4] );*/
fprintf( stderr, "at block %5d padding len %4d "
"type %02x sub %02x\n", i_pos, i_pes_length,
p_sec[0x11], p_sec[0x17 + p_sec[0x16]]);
}
return 0;
}
#endif