libdvdcss.c

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/* libdvdcss.c: DVD reading library.
 *
 * Authors: St閜hane Borel <[e-mail]>
 *          Samuel Hocevar <[e-mail]>
 *          H錵an Hjort <[e-mail]>
 *
 * Copyright (C) 1998-2002 VideoLAN
 * $Id: libdvdcss.c,v 1.3 2008/04/12 07:14:44 dsqiu Exp $
 *
 * 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.
 */

/**
 * \mainpage libdvdcss developer documentation
 *
 * \section intro Introduction
 *
 * \e libdvdcss is a simple library designed for accessing DVDs like a block
 * device without having to bother about the decryption. The important features
 * are:
 * \li portability: currently supported platforms are GNU/Linux, FreeBSD,
 *     NetBSD, OpenBSD, BSD/OS, BeOS, Windows 95/98, Windows NT/2000, MacOS X,
 *     Solaris, HP-UX and OS/2.
 * \li adaptability: unlike most similar projects, libdvdcss doesn't require
 *     the region of your drive to be set and will try its best to read from
 *     the disc even in the case of a region mismatch.
 * \li simplicity: a DVD player can be built around the \e libdvdcss API using
 *     no more than 4 or 5 library calls.
 *
 * \e libdvdcss is free software, released under the General Public License.
 * This ensures that \e libdvdcss remains free and used only with free
 * software.
 *
 * \section api The libdvdcss API
 *
 * The complete \e libdvdcss programming interface is documented in the
 * dvdcss.h file.
 *
 * \section env Environment variables
 *
 * Some environment variables can be used to change the behaviour of
 * \e libdvdcss without having to modify the program which uses it. These
 * variables are:
 *
 * \li \b DVDCSS_VERBOSE: sets the verbosity level.
 *     - \c 0 outputs no messages at all.
 *     - \c 1 outputs error messages to stderr.
 *     - \c 2 outputs error messages and debug messages to stderr.
 *
 * \li \b DVDCSS_METHOD: sets the authentication and decryption method
 *     that \e libdvdcss will use to read scrambled discs. Can be one
 *     of \c title, \c key or \c disc.
 *     - \c key is the default method. \e libdvdcss will use a set of
 *       calculated player keys to try and get the disc key. This can fail
 *       if the drive does not recognize any of the player keys.
 *     - \c disc is a fallback method when \c key has failed. Instead of
 *       using player keys, \e libdvdcss will crack the disc key using
 *       a brute force algorithm. This process is CPU intensive and requires
 *       64 MB of memory to store temporary data.
 *     - \c title is the fallback when all other methods have failed. It does
 *       not rely on a key exchange with the DVD drive, but rather uses a
 *       crypto attack to guess the title key. On rare cases this may fail
 *       because there is not enough encrypted data on the disc to perform
 *       a statistical attack, but in the other hand it is the only way to
 *       decrypt a DVD stored on a hard disc, or a DVD with the wrong region
 *       on an RPC2 drive.
 *
 * \li \b DVDCSS_RAW_DEVICE: specify the raw device to use. Exact usage will
 *     depend on your operating system, the Linux utility to set up raw devices
 *     is \c raw(8) for instance. Please note that on most operating systems,
 *     using a raw device requires highly aligned buffers: Linux requires a
 *     2048 bytes alignment (which is the size of a DVD sector).
 *
 * \li \b DVDCSS_CACHE: specify a directory in which to store title key
 *     values. This will speed up descrambling of DVDs which are in the
 *     cache. The DVDCSS_CACHE directory is created if it does not exist,
 *     and a subdirectory is created named after the DVD's title or
 *     manufacturing date. If DVDCSS_CACHE is not set or is empty, \e libdvdcss
 *     will use the default value which is "${HOME}/.dvdcss/" under Unix and
 *     "C:\Documents and Settings\$USER\Application Data\dvdcss\" under Win32.
 *     The special value "off" disables caching.
 */

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

#include <mplaylib.h>
#include <mplaylib.h>
#include <mplaylib.h>
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_SYS_PARAM_H
#   include <sys/param.h>
#endif
#ifdef HAVE_PWD_H
#   include <pwd.h>
#endif
#include <fcntl.h>
#include <errno.h>

#ifdef HAVE_UNISTD_H
#   include <unistd.h>
#endif

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

#ifdef HAVE_DIRECT_H
#   include <direct.h>
#endif

#include "dvdcss/dvdcss.h"

#include "common.h"
#include "css.h"
#include "libdvdcss.h"
#include "ioctl.h"
#include "device.h"
#undef memcpy
#define memcpy uc_memcpy
/**
 * \brief Symbol for version checks.
 *
 * The name of this symbol contains the library major number, which makes it
 * easy to check which \e libdvdcss development headers are installed on the
 * system with tools such as autoconf.
 *
 * The variable itself contains the exact version number of the library,
 * which can be useful for specific feature needs.
 */
char * dvdcss_interface_2 = VERSION;

/**
 * \brief Open a DVD device or directory and return a dvdcss instance.
 *
 * \param psz_target a string containing the target name, for instance
 *        "/dev/hdc" or "E:".
 * \return a handle to a dvdcss instance or NULL on error.
 *
 * Initialize the \e libdvdcss library and open the requested DVD device or
 * directory. \e libdvdcss checks whether ioctls can be performed on the disc,
 * and when possible, the disc key is retrieved.
 *
 * dvdcss_open() returns a handle to be used for all subsequent \e libdvdcss
 * calls. If an error occurred, NULL is returned.
 */
LIBDVDCSS_EXPORT dvdcss_t dvdcss_open ( char *psz_target )
{
    char psz_buffer[PATH_MAX];
    int i_ret;

    char *psz_method = getenv( "DVDCSS_METHOD" );
    char *psz_verbose = getenv( "DVDCSS_VERBOSE" );
    char *psz_cache = getenv( "DVDCSS_CACHE" );
#ifndef WIN32
    char *psz_raw_device = getenv( "DVDCSS_RAW_DEVICE" );
#endif

    dvdcss_t dvdcss;

    /*
     *  Allocate the library structure
     */
    dvdcss = malloc( sizeof( struct dvdcss_s ) );
    if( dvdcss == NULL )
    {
        return NULL;
    }

    /*
     *  Initialize structure with default values
     */
#ifndef WIN32
    dvdcss->i_raw_fd = -1;
#endif
    dvdcss->p_titles = NULL;
    dvdcss->psz_device = (char *)strdup( psz_target );
    dvdcss->psz_error = "no error";
    dvdcss->i_method = DVDCSS_METHOD_KEY;
    dvdcss->psz_cachefile[0] = '\0';
    dvdcss->b_debug = 0;
    dvdcss->b_errors = 0;

    /*
     *  Find verbosity from DVDCSS_VERBOSE environment variable
     */
    if( psz_verbose != NULL )
    {
        int i = atoi( psz_verbose );

        if( i >= 2 ) dvdcss->b_debug = i;
        if( i >= 1 ) dvdcss->b_errors = 1;
    }

    /*
     *  Find method from DVDCSS_METHOD environment variable
     */
    if( psz_method != NULL )
    {
        if( !strncmp( psz_method, "key", 4 ) )
        {
            dvdcss->i_method = DVDCSS_METHOD_KEY;
        }
        else if( !strncmp( psz_method, "disc", 5 ) )
        {
            dvdcss->i_method = DVDCSS_METHOD_DISC;
        }
        else if( !strncmp( psz_method, "title", 5 ) )
        {
            dvdcss->i_method = DVDCSS_METHOD_TITLE;
        }
        else
        {
            print_error( dvdcss, "unknown decrypt method, please choose "
                                 "from 'title', 'key' or 'disc'" );
            free( dvdcss->psz_device );
            free( dvdcss );
            return NULL;
        }
    }

    /*
     *  If DVDCSS_CACHE was not set, try to guess a default value
     */
    if( psz_cache == NULL || psz_cache[0] == '\0' )
    {
#ifdef HAVE_DIRECT_H
        typedef HRESULT( WINAPI *SHGETFOLDERPATH )
                       ( HWND, int, HANDLE, DWORD, LPTSTR );

#   define CSIDL_FLAG_CREATE 0x8000
#   define CSIDL_APPDATA 0x1A
#   define SHGFP_TYPE_CURRENT 0

        char psz_home[MAX_PATH];
        HINSTANCE p_dll;
        SHGETFOLDERPATH p_getpath;

        *psz_home = '\0';

        /* Load the shfolder dll to retrieve SHGetFolderPath */
        p_dll = LoadLibrary( "shfolder.dll" );
        if( p_dll )
        {
            p_getpath = (void*)GetProcAddress( p_dll, "SHGetFolderPathA" );
            if( p_getpath )
            {
                /* Get the "Application Data" folder for the current user */
                if( p_getpath( NULL, CSIDL_APPDATA | CSIDL_FLAG_CREATE,
                               NULL, SHGFP_TYPE_CURRENT, psz_home ) == S_OK )
                {
                    FreeLibrary( p_dll );
                }
                else
                {
                    *psz_home = '\0';
                }
            }
            FreeLibrary( p_dll );
        }

        /* Cache our keys in
         * C:\Documents and Settings\$USER\Application Data\dvdcss\ */
        if( *psz_home )
        {
            snprintf( psz_buffer, PATH_MAX, "%s/dvdcss", psz_home );
            psz_buffer[PATH_MAX-1] = '\0';
            psz_cache = psz_buffer;
        }
#else
        char *psz_home = NULL;
#   ifdef HAVE_PWD_H
        struct passwd *p_pwd;

        /* Try looking in password file for home dir. */
        p_pwd = getpwuid(getuid());
        if( p_pwd )
        {
            psz_home = p_pwd->pw_dir;
        }
#   endif

        if( psz_home == NULL )
        {
            psz_home = getenv( "HOME" );
        }
        if( psz_home == NULL )
        {
            psz_home = getenv( "USERPROFILE" );
        }

        /* Cache our keys in ${HOME}/.dvdcss/ */
        if( psz_home )
        {
            snprintf( psz_buffer, PATH_MAX, "%s/.dvdcss", psz_home );
            psz_buffer[PATH_MAX-1] = '\0';
            psz_cache = psz_buffer;
        }
#endif
    }

    /*
     *  Find cache dir from the DVDCSS_CACHE environment variable
     */
    if( psz_cache != NULL )
    {
        if( psz_cache[0] == '\0' || !strcmp( psz_cache, "off" ) )
        {
            psz_cache = NULL;
        }
        /* Check that we can add the ID directory and the block filename */
        else if( strlen( psz_cache ) + 1 + 32 + 1 + (KEY_SIZE * 2) + 10 + 1
                  > PATH_MAX )
        {
            print_error( dvdcss, "cache directory name is too long" );
            psz_cache = NULL;
        }
    }

    /*
     *  Open device
     */
    _dvdcss_check( dvdcss );
    i_ret = _dvdcss_open( dvdcss );
    if( i_ret < 0 )
    {
        free( dvdcss->psz_device );
        free( dvdcss );
        return NULL;
    }

    dvdcss->b_scrambled = 1; /* Assume the worst */
    dvdcss->b_ioctls = _dvdcss_use_ioctls( dvdcss );

    if( dvdcss->b_ioctls )
    {
        i_ret = _dvdcss_test( dvdcss );
        if( i_ret < 0 )
        {
            /* Disable the CSS ioctls and hope that it works? */
            print_debug( dvdcss,
                         "could not check whether the disc was scrambled" );
            dvdcss->b_ioctls = 0;
        }
        else
        {
            print_debug( dvdcss, i_ret ? "disc is scrambled"
                                       : "disc is unscrambled" );
            dvdcss->b_scrambled = i_ret;
        }
    }

    /* If disc is CSS protected and the ioctls work, authenticate the drive */
    if( dvdcss->b_scrambled && dvdcss->b_ioctls )
    {
        i_ret = _dvdcss_disckey( dvdcss );

        if( i_ret < 0 )
        {
            _dvdcss_close( dvdcss );
            free( dvdcss->psz_device );
            free( dvdcss );
            return NULL;
        }
    }

    /* If the cache is enabled, write the cache directory tag */
    if( psz_cache )
    {
        char *psz_tag = "Signature: 8a477f597d28d172789f06886806bc55\r\n"
            "# This file is a cache directory tag created by libdvdcss.\r\n"
            "# For information about cache directory tags, see:\r\n"
            "#   http://www.brynosaurus.com/cachedir/\r\n";
        char psz_tagfile[PATH_MAX + 1 + 12 + 1];
        int i_fd;

        sprintf( psz_tagfile, "%s/CACHEDIR.TAG", psz_cache );
        i_fd = open( psz_tagfile, O_RDWR|O_CREAT, 0644 );
        if( i_fd >= 0 )
        {
            write( i_fd, psz_tag, strlen(psz_tag) );
            close( i_fd );
        }
    }