Adding upstream version 1.4.3.upstream/1.4.3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1756 insertions, 0 deletions

diff --git a/src/css.c b/src/css.c
new file mode 100644
index 0000000..55cb8df
--- /dev/null
+++ b/src/css.c
@@ -0,0 +1,1756 @@
+/*****************************************************************************
+ * css.c: Functions for DVD authentication and descrambling
+ *****************************************************************************
+ * Copyright (C) 1999-2008 VideoLAN
+ *
+ * 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.
+ *
+ * libdvdcss 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.
+ *
+ * libdvdcss 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 libdvdcss; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *****************************************************************************/
+
+/*****************************************************************************
+ * Preamble
+ *****************************************************************************/
+#include "config.h"
+
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#ifdef HAVE_SYS_PARAM_H
+#   include <sys/param.h>
+#endif
+#ifdef HAVE_UNISTD_H
+#   include <unistd.h>
+#endif
+#include <fcntl.h>
+
+#include "dvdcss/dvdcss.h"
+
+#include "common.h"
+#include "css.h"
+#include "libdvdcss.h"
+#include "csstables.h"
+#include "ioctl.h"
+#include "device.h"
+
+#define PSZ_KEY_SIZE (DVD_KEY_SIZE * 3)
+
+/*****************************************************************************
+ * Local prototypes
+ *****************************************************************************/
+static void PrintKey        ( dvdcss_t, const char *, const uint8_t * );
+
+static int  GetBusKey       ( dvdcss_t );
+static int  GetASF          ( dvdcss_t );
+
+static void CryptKey        ( int, int, const uint8_t *, uint8_t * );
+static void DecryptKey      ( uint8_t,
+                              const uint8_t *, const uint8_t *, uint8_t * );
+
+static int  DecryptDiscKey  ( dvdcss_t, const uint8_t *, dvd_key );
+static int  CrackDiscKey    ( uint8_t * );
+
+static void DecryptTitleKey ( dvd_key, dvd_key );
+static int  RecoverTitleKey ( int, const uint8_t *,
+                              const uint8_t *, const uint8_t *, uint8_t * );
+static int  CrackTitleKey   ( dvdcss_t, int, int, dvd_key );
+
+static int  AttackPattern   ( const uint8_t[], uint8_t * );
+#if 0
+static int  AttackPadding   ( const uint8_t[] );
+#endif
+
+static int  dvdcss_titlekey ( dvdcss_t, int, dvd_key );
+
+/*****************************************************************************
+ * 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 (Regional Playback Control) 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 )
+{
+    const char *psz_type, *psz_rpc;
+    char psz_region[17];
+    char *p_region = psz_region;
+    int i_ret, i_copyright, i_type, i_mask, i_rpc, i_region;
+
+    i_ret = ioctl_ReadCopyright( dvdcss->i_fd, 0 /* i_layer */, &i_copyright );
+
+    if( i_ret < 0 )
+    {
+#ifdef _WIN32
+        /* 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. */
+        if( dvdcss_disckey( dvdcss ) < 0 )
+        {
+            i_copyright = 0;
+        }
+        else
+        {
+            i_copyright = 1;
+        }
+#else
+        /* 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;
+#endif /* _WIN32 */
+    }
+
+    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 (Regional Playback "
+                     "Control) 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 (Regional Playback Control) 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;
+    }
+
+    *p_region = '\0';
+    for( i_region = 0; i_region < 8; i_region++ )
+    {
+        if( !( i_mask & ( 1 << i_region ) ) )
+        {
+            sprintf(p_region, " %d", i_region + 1);
+            p_region += 2;
+        }
+    }
+
+    print_debug( dvdcss, "drive region(s)%s, region mask 0x%x, %s, %s",
+                 psz_region, 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 )
+{
+    struct dvd_title *p_title;
+    struct dvd_title *p_newtitle;
+    dvd_key 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(p_title->p_key) );
+        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, "%." CACHE_FILENAME_LENGTH_STRING "x",
+                 i_block );
+        i_fd = open( dvdcss->psz_cachefile, O_RDONLY );
+        b_cache = 1;
+
+        if( i_fd >= 0 )
+        {
+            char psz_key[PSZ_KEY_SIZE];
+            unsigned int k0, k1, k2, k3, k4;
+
+            psz_key[PSZ_KEY_SIZE - 1] = '\0';
+
+            if( read( i_fd, psz_key, PSZ_KEY_SIZE - 1 ) == PSZ_KEY_SIZE - 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 Content Scrambling System (CSS) title key
+     * for current Video Title Set (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 Video Title Set (VTS) "
+                                 "Content Scrambling System (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[PSZ_KEY_SIZE + 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] );
+
+            if( write( i_fd, psz_key, PSZ_KEY_SIZE + 1 ) < PSZ_KEY_SIZE + 1 )
+            {
+                print_error( dvdcss,
+                             "Error caching key on disk, continuing..\n" );
+            }
+            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( *p_newtitle ) );
+    if( p_newtitle == NULL )
+    {
+        return -1;
+    }
+    p_newtitle->i_startlb = i_block;
+    memcpy( p_newtitle->p_key, p_title_key, DVD_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, DVD_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 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 invalidated 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, "authentication success flag (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 % DVD_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, DVD_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, DVD_KEY_SIZE );
+            PrintKey( dvdcss, "cracking disc key ", p_disc_key );
+            if( ! CrackDiscKey( 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, DVD_KEY_SIZE );
+            dvdcss->i_method = DVDCSS_METHOD_TITLE;
+            break;
+
+        default:
+
+            print_debug( dvdcss, "disc key does not need to be decrypted" );
+            memset( p_disc_key, 0, DVD_KEY_SIZE );
+            break;
+    }
+
+    memcpy( dvdcss->css.p_disc_key, p_disc_key, DVD_KEY_SIZE );
+
+    return 0;
+}
+
+
+/*****************************************************************************
+ * dvdcss_titlekey: get title key.
+ *****************************************************************************/
+static int dvdcss_titlekey( dvdcss_t dvdcss, int i_pos, dvd_key p_title_key )
+{
+    static uint8_t p_garbage[ DVDCSS_BLOCK_SIZE ];  /* we never read it back */
+    uint8_t p_key[DVD_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 authentication success flag (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 authentication success flag (ASF), requesting title key" );
+                break;
+
+            case 1:
+                /* Drive status is OK. */
+                /* If the title key request failed, but we did not lose ASF,
+                 * we might still have the AGID.  Other code assumes 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 < DVD_KEY_SIZE ; i++ )
+            {
+                p_key[i] ^= dvdcss->css.p_bus_key[4 - (i % DVD_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, DVD_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, DVD_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 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 Content Scrambling System (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 say
+ * 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 * DVD_KEY_SIZE];
+    dvd_key   p_key1;
+    dvd_key   p_key2;
+    dvd_key   p_key_check;
+    uint8_t   i_variant = 0;
+    int       i_ret = -1;
+    int       i;
+
+    print_debug( dvdcss, "requesting authentication grant ID (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 authentication grant ID (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 "
+                             "authentication grant ID (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 authentication grant ID (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 < DVD_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, DVD_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 < DVD_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, DVD_KEY_SIZE );
+    memcpy( p_challenge + DVD_KEY_SIZE, p_key2, DVD_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, const char *prefix, const uint8_t *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 (ASF)
+ *****************************************************************************
+ * 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, &i_asf ) != 0 )
+    {
+        /* The ioctl process has failed */
+        print_error( dvdcss, "GetASF fatal error" );
+        return -1;
+    }
+
+    if( i_asf )
+    {
+        print_debug( dvdcss, "authentication success flag set, ASF=1" );
+    }
+    else
+    {
+        print_debug( dvdcss, "authentication success flag not set, ASF=0" );
+    }
+
+    return i_asf;
+}
+
+/*****************************************************************************
+ * CryptKey: shuffle bits and decrypt keys.
+ *****************************************************************************
+ * Used during authentication and disc key negotiation 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,
+                      const uint8_t *p_challenge, uint8_t *p_key )
+{
+    /* Permutation table for challenge */
+    static const 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 */
+    static const 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 } };
+
+    static const 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 */
+    static const 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 LFSR 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 initialize 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 dependent on the type of key:
+ *  -for disc key, invert is 0x00,
+ *  -for title key, invert if 0xff.
+ *****************************************************************************/
+static void DecryptKey( uint8_t invert, const uint8_t *p_key,
+                        const uint8_t *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 < DVD_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 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, const uint8_t *p_struct_disckey,
+                           dvd_key p_disc_key )
+{
+    uint8_t p_verify[DVD_KEY_SIZE];
+    unsigned int i, n = 0;
+
+    /* Decrypt disc key with the above player keys */
+    for( n = 0; n < sizeof(player_keys) / sizeof(*player_keys); 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, DVD_KEY_SIZE ) == 0 )
+            {
+                return 0;
+            }
+        }
+    }
+
+    /* Have tried all combinations of positions and keys,
+     * and we still didn't succeed. */
+    memset( p_disc_key, 0, DVD_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 p_disc_key, dvd_key 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 K1TABLESIZE  65536
+#define K1TABLEWIDTH 10
+
+#define BIGTABLESIZE 16777216
+
+/*
+ * Simple function to test if a candidate key produces the given hash
+ */
+static int investigate( unsigned char *hash, unsigned char *ckey )
+{
+    unsigned char key[DVD_KEY_SIZE];
+
+    DecryptKey( 0, ckey, hash, key );
+
+    return memcmp( key, ckey, DVD_KEY_SIZE );
+}
+
+static int CrackDiscKey( 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, ret = 0;
+    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 = calloc( K1TABLESIZE, 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 )
+            {
+                K1table[ K1TABLEWIDTH * ( 256 * j + tmp3 ) +    tmp4 ] = i;
+            }
+            K1table[ K1TABLEWIDTH * ( 256 * j + tmp3 ) ] = tmp4;
+        }
+    }
+
+    /* Initializing our really big table */
+    BigTable = calloc( BIGTABLESIZE, sizeof(*BigTable) );
+    if( BigTable == NULL )
+    {
+        free( K1table );
+        return -1;
+    }
+
+    tmp3 = 0;
+
+    for( i = 0 ; i < BIGTABLESIZE ; 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];
+        if ( j >= BIGTABLESIZE )
+        {
+            ret = -1;
+            goto error;
+        }
+        BigTable[j] = i;
+    }
+
+    /*
+     * We are done initializing, now reverse hash
+     */
+    tmp5 = p_disc_key[0] ^ p_css_tab1[ p_disc_key[1] ];
+
+    for( nStepA = 0 ; nStepA < K1TABLESIZE ; 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 ];
+        }
+
+        /* compute 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];
+                if ( tmp4 >= BIGTABLESIZE )
+                {
+                    ret = -1;
+                    goto error;
+                }
+                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];
+                if ( tmp4 >= BIGTABLESIZE )
+                {
+                    ret = -1;
+                    goto error;
+                }
+                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], DVD_KEY_SIZE );
+
+error:
+    free( K1table );
+    free( BigTable );
+
+    return ret;
+}
+
+/*****************************************************************************
+ * 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, const uint8_t *p_crypted,
+                            const uint8_t *p_decrypted,
+                            const uint8_t *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 normally */
+            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 brute-force
+                 * 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 copyright 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 scrambled 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 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 "
+                                     "arcane secrets to recover", i_pos );
+
+                /* Reset the drive before trying to continue */
+                dvdcss_close_device( dvdcss );
+                dvdcss_open_device( 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, "block %i is a non-MPEG block "
+                                 "(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, p_titlekey ) > 0 )
+            {
+                b_stop_scanning = 1;
+            }
+#if 0
+            if( AttackPadding( p_buf ) > 0 )
+            {
+                b_stop_scanning = 1;
+            }
+#endif /* 0 */
+        }
+
+        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, "Video Title Set (VTS) key initialized" );
+        return 1;
+    }
+
+    if( i_encrypted == 0 && i_reads > 0 )
+    {
+        memset( p_titlekey, 0, DVD_KEY_SIZE );
+        print_debug( dvdcss, "no scrambled sectors found" );
+        return 0;
+    }
+
+    memset( p_titlekey, 0, DVD_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 continuation of that pattern.
+ *****************************************************************************/
+static int AttackPattern( const uint8_t p_sec[ DVDCSS_BLOCK_SIZE ],
+                          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, DVD_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 );
+        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 piece 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( const uint8_t p_sec[ DVDCSS_BLOCK_SIZE ] )
+{
+    unsigned int i_pes_length;
+    /*static int i_tries = 0, i_success = 0;*/
+
+    i_pes_length = (p_sec[0x12]<<8) | p_sec[0x13];
+
+    /* Covered by the test below but useful for debugging. */
+    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.
+       Normally 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 except 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++;
+    }
+
+    return 0;
+}
+#endif /* 0 */