/***************************************************************************** * dvd_css.c: Functions for DVD authentification and unscrambling ***************************************************************************** * Copyright (C) 1999-2001 VideoLAN * $Id: dvd_css.c,v 1.32 2001/06/03 12:47:21 sam Exp $ * * Author: Stéphane Borel * * 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 * - 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 "defs.h" #include #include #ifdef HAVE_UNISTD_H # include #elif defined( _MSC_VER ) && defined( _WIN32 ) # include #endif #include #include "config.h" #include "common.h" #include "threads.h" #include "mtime.h" #include "intf_msg.h" #include "dvd_css.h" #ifdef HAVE_CSS # include "dvd_csstables.h" #endif /* HAVE_CSS */ #include "dvd_ioctl.h" #include "input_dvd.h" #include "modules.h" #include "modules_export.h" /***************************************************************************** * Local prototypes *****************************************************************************/ #ifdef HAVE_CSS static int CSSGetASF ( int i_fd ); static void CSSCryptKey ( int i_key_type, int i_varient, u8 const * pi_challenge, u8* pi_key ); static int CSSCracker ( int i_start, unsigned char * p_crypted, unsigned char * p_decrypted, dvd_key_t * p_sector_key, dvd_key_t * p_key ); #endif /* HAVE_CSS */ /***************************************************************************** * CSSTest : check if the disc is encrypted or not *****************************************************************************/ int CSSTest( int i_fd ) { int i_ret, i_copyright; i_ret = ioctl_ReadCopyright( i_fd, 0 /* i_layer */, &i_copyright ); if( i_ret < 0 ) { /* Since it's the first ioctl we try to issue, we add a notice */ intf_ErrMsg( "css error: ioctl_ReadCopyright failed, " "make sure DVD ioctls were compiled in" ); return i_ret; } return i_copyright; } /***************************************************************************** * CSSInit : CSS Structure initialisation and DVD authentication. ***************************************************************************** * It simulates the mutual authentication between logical unit and host. * Since we don't need the disc key to find the title key, we just run the * basic unavoidable commands to authenticate device and disc. *****************************************************************************/ int CSSInit( int i_fd, css_t * p_css ) { #ifdef HAVE_CSS /* structures defined in cdrom.h or dvdio.h */ char p_buffer[2048 + 4 + 1]; int i_agid = 0; int i_ret = -1; int i; /* Test authentication success */ switch( CSSGetASF( i_fd ) ) { case -1: return -1; case 1: intf_WarnMsg( 2, "css info: already authenticated" ); return 0; case 0: intf_WarnMsg( 2, "css info: need to authenticate" ); } /* Init sequence, request AGID */ for( i = 1; i < 4 ; ++i ) { intf_WarnMsg( 2, "css info: requesting AGID %d", i ); i_ret = ioctl_ReportAgid( i_fd, &i_agid ); if( i_ret != -1 ) { /* No error during ioctl: we know the device is authenticated */ break; } intf_ErrMsg( "css error: ioctl_ReportAgid failed, invalidating" ); i_agid = 0; ioctl_InvalidateAgid( i_fd, &i_agid ); } /* Unable to authenticate without AGID */ if( i_ret == -1 ) { intf_ErrMsg( "css error: ioctl_ReportAgid failed, fatal" ); return -1; } for( i = 0 ; i < 10; ++i ) { p_css->disc.pi_challenge[i] = i; } /* Get challenge from host */ for( i = 0 ; i < 10 ; ++i ) { p_buffer[9-i] = p_css->disc.pi_challenge[i]; } /* Send challenge to LU */ if( ioctl_SendChallenge( i_fd, &i_agid, p_buffer ) < 0 ) { intf_ErrMsg( "css error: ioctl_SendChallenge failed" ); return -1; } /* Get key1 from LU */ if( ioctl_ReportKey1( i_fd, &i_agid, p_buffer ) < 0) { intf_ErrMsg( "css error: ioctl_ReportKey1 failed" ); return -1; } /* Send key1 to host */ for( i = 0 ; i < KEY_SIZE ; i++ ) { p_css->disc.pi_key1[i] = p_buffer[4-i]; } for( i = 0 ; i < 32 ; ++i ) { CSSCryptKey( 0, i, p_css->disc.pi_challenge, p_css->disc.pi_key_check ); if( memcmp( p_css->disc.pi_key_check, p_css->disc.pi_key1, KEY_SIZE ) == 0 ) { intf_WarnMsg( 2, "css info: drive authentic, using variant %d", i); p_css->disc.i_varient = i; break; } } if( i == 32 ) { intf_ErrMsg( "css error: drive would not authenticate" ); return -1; } /* Get challenge from LU */ if( ioctl_ReportChallenge( i_fd, &i_agid, p_buffer ) < 0 ) { intf_ErrMsg( "css error: ioctl_ReportKeyChallenge failed" ); return -1; } /* Send challenge to host */ for( i = 0 ; i < 10 ; ++i ) { p_css->disc.pi_challenge[i] = p_buffer[9-i]; } CSSCryptKey( 1, p_css->disc.i_varient, p_css->disc.pi_challenge, p_css->disc.pi_key2 ); /* Get key2 from host */ for( i = 0 ; i < KEY_SIZE ; ++i ) { p_buffer[4-i] = p_css->disc.pi_key2[i]; } /* Send key2 to LU */ if( ioctl_SendKey2( i_fd, &i_agid, p_buffer ) < 0 ) { intf_ErrMsg( "css error: ioctl_SendKey2 failed" ); return -1; } intf_WarnMsg( 2, "css info: authentication established" ); memcpy( p_css->disc.pi_challenge, p_css->disc.pi_key1, KEY_SIZE ); memcpy( p_css->disc.pi_challenge+KEY_SIZE, p_css->disc.pi_key2, KEY_SIZE ); CSSCryptKey( 2, p_css->disc.i_varient, p_css->disc.pi_challenge, p_css->disc.pi_key_check ); intf_WarnMsg( 2, "css info: received session key" ); if( i_agid < 0 ) { return -1; } /* Test authentication success */ switch( CSSGetASF( i_fd ) ) { case -1: return -1; case 1: intf_WarnMsg( 2, "css info: already authenticated" ); return 0; case 0: intf_WarnMsg( 2, "css info: need to get disc key" ); } /* Get encrypted disc key */ if( ioctl_ReadKey( i_fd, &i_agid, p_buffer ) < 0 ) { intf_ErrMsg( "css error: ioctl_ReadKey failed" ); return -1; } /* Unencrypt disc key using bus key */ for( i = 0 ; i < 2048 ; i++ ) { p_buffer[ i ] ^= p_css->disc.pi_key_check[ 4 - (i % KEY_SIZE) ]; } memcpy( p_css->disc.pi_key_check, p_buffer, 2048 ); /* initialize title key to know it empty */ for( i = 0 ; i < KEY_SIZE ; i++ ) { p_css->pi_title_key[i] = 0; } /* Test authentication success */ switch( CSSGetASF( i_fd ) ) { case -1: return -1; case 1: intf_WarnMsg( 2, "css info: successfully authenticated" ); return 0; case 0: intf_ErrMsg( "css error: no way to authenticate" ); return -1; } #else /* HAVE_CSS */ intf_ErrMsg( "css error: CSS decryption is disabled in this module" ); #endif /* HAVE_CSS */ return -1; } /***************************************************************************** * CSSGetKey : get title key. ***************************************************************************** * The DVD should have been opened and authenticated before. *****************************************************************************/ int CSSGetKey( int i_fd, css_t * p_css ) { #ifdef HAVE_CSS /* * Title key cracking method from Ethan Hawke, * with Frank A. Stevenson algorithm. * Does not use any player key table and ioctls. */ u8 pi_buf[0x800]; dvd_key_t pi_key; off_t i_pos; boolean_t b_encrypted; boolean_t b_stop_scanning; int i_bytes_read; int i_best_plen; int i_best_p; int i,j; for( i = 0 ; i < KEY_SIZE ; i++ ) { pi_key[i] = 0; } b_encrypted = 0; b_stop_scanning = 0; /* Position of the title on the disc */ i_pos = p_css->i_title_pos; do { #if !defined( WIN32 ) i_pos = lseek( i_fd, i_pos, SEEK_SET ); i_bytes_read = read( i_fd, pi_buf, 0x800 ); #else i_pos = SetFilePointer( (HANDLE) i_fd, i_pos, 0, FILE_BEGIN ); ReadFile( (HANDLE) i_fd, pi_buf, 0x800, &i_bytes_read, NULL ); #endif /* PES_scrambling_control */ if( pi_buf[0x14] & 0x30 ) { b_encrypted = 1; i_best_plen = 0; i_best_p = 0; for( i = 2 ; i < 0x30 ; i++ ) { for( j = i ; ( j < 0x80 ) && ( pi_buf[0x7F - (j%i)] == pi_buf[0x7F-j] ) ; j++ ); { if( ( j > i_best_plen ) && ( j > i ) ) { i_best_plen = j; i_best_p = i; } } } if( ( i_best_plen > 20 ) && ( i_best_plen / i_best_p >= 2) ) { i = CSSCracker( 0, &pi_buf[0x80], &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p], (dvd_key_t*)&pi_buf[0x54], &pi_key ); b_stop_scanning = ( i >= 0 ); } } i_pos += i_bytes_read; } while( i_bytes_read == 0x800 && !b_stop_scanning); if( b_stop_scanning) { memcpy( p_css->pi_title_key, &pi_key, sizeof(dvd_key_t) ); intf_WarnMsg( 2, "css info: vts key initialized" ); return 0; } if( !b_encrypted ) { intf_WarnMsg( 2, "css warning: this file was _NOT_ encrypted!" ); return 0; } return -1; #else /* HAVE_CSS */ intf_ErrMsg( "css error: css decryption unavailable" ); return -1; #endif /* HAVE_CSS */ } /***************************************************************************** * CSSDescrambleSector ***************************************************************************** * sec : sector to descramble * key : title key for this sector *****************************************************************************/ int CSSDescrambleSector( dvd_key_t pi_key, u8* pi_sec ) { #ifdef HAVE_CSS unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6; u8* pi_end = pi_sec + 0x800; /* PES_scrambling_control */ if( pi_sec[0x14] & 0x30) { i_t1 = ((pi_key)[0] ^ pi_sec[0x54]) | 0x100; i_t2 = (pi_key)[1] ^ pi_sec[0x55]; i_t3 = (((pi_key)[2]) | ((pi_key)[3] << 8) | ((pi_key)[4] << 16)) ^ ((pi_sec[0x56]) | (pi_sec[0x57] << 8) | (pi_sec[0x58] << 16)); i_t4 = i_t3 & 7; i_t3 = i_t3 * 2 + 8 - i_t4; pi_sec += 0x80; i_t5 = 0; while( pi_sec != pi_end ) { i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1]; i_t2 = i_t1>>1; i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4; i_t4 = pi_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 = pi_css_tab4[i_t6]; i_t5 += i_t6 + i_t4; *pi_sec = pi_css_tab1[*pi_sec] ^( i_t5 & 0xff ); pi_sec++; i_t5 >>= 8; } } return 0; #else /* HAVE_CSS */ return 1; #endif /* HAVE_CSS */ } #ifdef HAVE_CSS /* Following functions are local */ /***************************************************************************** * CSSGetASF : Get Authentification success flag ***************************************************************************** * Returns : * -1 on ioctl error, * 0 if the device needs to be authenticated, * 1 either. *****************************************************************************/ static int CSSGetASF( int i_fd ) { int i_agid; int i_asf = 0; for( i_agid = 0 ; i_agid < 4 ; i_agid++ ) { if( ioctl_ReportASF( i_fd, &i_agid, &i_asf ) == 0 ) { intf_WarnMsg( 3, "css info: GetASF %sauthenticated", i_asf ? "":"not " ); return i_asf; } } /* The ioctl process has failed */ intf_ErrMsg( "css error: GetASF fatal error" ); return -1; } /***************************************************************************** * CSSCryptKey : shuffles bits and unencrypt keys. ***************************************************************************** * Used during authentication and disc key negociation in CSSInit. * i_key_type : 0->key1, 1->key2, 2->buskey. * i_varient : between 0 and 31. *****************************************************************************/ static void CSSCryptKey( int i_key_type, int i_varient, u8 const * pi_challenge, u8* pi_key ) { /* Permutation table for challenge */ u8 ppi_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 varient table for key2 and buskey */ u8 ppi_perm_varient[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 } }; u8 pi_varients[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 */ u8 pi_secret[5] = { 0x55, 0xD6, 0xC4, 0xC5, 0x28 }; u8 pi_bits[30]; u8 pi_scratch[10]; u8 pi_tmp1[5]; u8 pi_tmp2[5]; u8 i_lfsr0_o; /* 1 bit used */ u8 i_lfsr1_o; /* 1 bit used */ u32 i_lfsr0; u32 i_lfsr1; u8 i_css_varient; u8 i_cse; u8 i_index; u8 i_combined; u8 i_carry; u8 i_val = 0; int i_term = 0; int i_bit; int i; for (i = 9; i >= 0; --i) pi_scratch[i] = pi_challenge[ppi_perm_challenge[i_key_type][i]]; i_css_varient = ( i_key_type == 0 ) ? i_varient : ppi_perm_varient[i_key_type-1][i_varient]; /* * This encryption engine implements one of 32 variations * one the same theme depending upon the choice in the * varient 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 ; ) { pi_tmp1[i] = pi_scratch[5 + i] ^ pi_secret[i] ^ pi_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 = ( pi_tmp1[0] << 17 ) | ( pi_tmp1[1] << 9 ) | (( pi_tmp1[2] & ~7 ) << 1 ) | 8 | ( pi_tmp1[2] & 7 ); i_lfsr1 = ( pi_tmp1[3] << 9 ) | 0x100 | pi_tmp1[4]; i_index = sizeof(pi_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; } pi_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 = pi_varients[i_css_varient] ^ pi_crypt_tab2[i_css_varient]; /* 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 = pi_scratch[i] ) { i_index = pi_bits[25 + i] ^ pi_scratch[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; } pi_tmp1[4] ^= pi_tmp1[0]; for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] ) { i_index = pi_bits[20 + i] ^ pi_tmp1[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; pi_tmp2[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; } pi_tmp2[4] ^= pi_tmp2[0]; for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] ) { i_index = pi_bits[15 + i] ^ pi_tmp2[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; pi_tmp1[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index]; } pi_tmp1[4] ^= pi_tmp1[0]; for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] ) { i_index = pi_bits[10 + i] ^ pi_tmp1[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; pi_tmp2[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index]; } pi_tmp2[4] ^= pi_tmp2[0]; for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] ) { i_index = pi_bits[5 + i] ^ pi_tmp2[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; } pi_tmp1[4] ^= pi_tmp1[0]; for(i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] ) { i_index = pi_bits[i] ^ pi_tmp1[i]; i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse; pi_key[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term; } return; } /***************************************************************************** * CSSCracker : title key decryption by cracking ***************************************************************************** * This function is called by CSSGetKeys to find a key *****************************************************************************/ static int CSSCracker( int i_start, unsigned char * p_crypted, unsigned char * p_decrypted, dvd_key_t * p_sector_key, dvd_key_t * p_key ) { unsigned char pi_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++ ) { pi_buffer[i] = pi_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 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1]; i_t2 = i_t1 >> 1; i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4; i_t4 = pi_css_tab5[i_t4]; /* deduce i_t6 & i_t5 */ i_t6 = pi_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 = pi_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 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1]; i_t2 = i_t1 >> 1; i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4; i_t4 = pi_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 = pi_css_tab4[i_t6]; i_t5 += i_t6 + i_t4; if( ( i_t5 & 0xff ) != pi_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_key)[0]; (*p_key)[1] ^= (*p_sector_key)[1]; (*p_key)[2] ^= (*p_sector_key)[2]; (*p_key)[3] ^= (*p_sector_key)[3]; (*p_key)[4] ^= (*p_sector_key)[4]; } return i_exit; } #endif /* HAVE_CSS */