/***************************************************************************** * css.c: Functions for DVD authentication and descrambling ***************************************************************************** * Copyright (C) 1999-2003 VideoLAN * $Id$ * * Authors: Stéphane Borel * Håkan Hjort * * based on: * - css-auth by Derek Fawcus * - DVD CSS ioctls example program by Andrew T. Veliath * - The Divide and conquer attack by Frank A. Stevenson * (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 #include #include #include #include #ifdef HAVE_SYS_PARAM_H # include #endif #ifdef HAVE_UNISTD_H # include #endif #include #ifdef HAVE_LIMITS_H # include #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 *****************************************************************************/ 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++ ) { 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 ) { 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