#!/usr/bin/perl use Getopt::Std; # # geteltorito.pl: a bootimage extractor # Script that will extract the first El Torito bootimage from a # bootable CD image # R. Krienke 08/2001 # krienke@uni-koblenz.de # License: GPL # # Get latest version from: # http://userpages.uni-koblenz.de/~krienke/ftp/noarch/geteltorito # $utilVersion="0.5"; # # Version 0.5 # 2009/06/22 # A patch for harddisk emulation images from <colimit@gmail.com>. # For BootMediaType=4 (harddisk emulation) SectorCount is always 1, and geteltorito.pl # returns just MBR. This patch guesses the correct bootimage size # from MBR (offset+size of the first partitition). # Version 0.4 # 2007/02/01 # A patch from Santiago Garcia <manty@debian.org> to use a virtual sector # size (vSecSize) of 512 bytes, as defined on "El Torito" specs and change # unpack of the sector count from n to v to get the correct sector count. # Version 0.3 # 2006/02/21 # A patch from Ben Collins <bcollins@ubuntu.com> to make the # utility work on PPC machines (change from 'L'-encoding in pack to 'V') # Version 0.2 # Several patches included from Nathan Stratton Treadway(nathant@ontko.com) # to adjust the platform output as well as fixes for other minor bugs # Version 0.1 # Initial release # # For information on El Torito see # http://en.wikipedia.org/wiki/El_torito $vSecSize=512; $secSize=2048; $ret=undef;$version=undef;$opt_h=undef;$loadSegment=undef;$systemType=undef; # # Read a particular sector from a file # sector counting starts at 0, not 1 # sub getSector{ my ($secNum, $secCount, $file)=@_; my ($sec, $count); open(FILE, $file) || die "Cannot open \"$file\" \n"; seek(FILE, $secNum*$secSize, 0); $count=read(FILE, $sec, $vSecSize*$secCount, 0) ; if( $count != $vSecSize*$secCount ){ warn "Error reading from file \"$file\"\n"; } close(FILE); return($sec); } # # Write eltorito data into a file # sub writeOutputFile{ my($name)=shift; my($value)=shift; open(OUT, ">".$name)|| die "$0: Cannot open outputfile \"$name\" for writing. Stop."; print OUT $value; close(OUT); } # # Usage # sub usage{ warn "\n$0 [-hv] [-o outputfilename] cd-image \n", "Script will try to extract an El Torito image from a \n", "bootable CD (or cd-image) given by <cd-image> and write \n", "the data extracted to STDOUT or to a file.\n", " -h: This help. \n", " -v: Print version of script and exit.\n", " -o <file>: Write extracted data to file <file> instead of STDOUT.\n", "\n\n"; exit 0; } # --------------------------------------------------------------------- $ret=getopts('hvo:'); if( defined($opt_v) ){ warn "Version: $utilVersion \n"; exit 0; } if( defined($opt_h) || $#ARGV <0 ){ usage(0); } if( defined($opt_o) ){ $outputFilename="$opt_o"; } $imageFile=$ARGV[0]; if( ! -r $imageFile ){ die "Cannot read image/device \"$imageFile\". Aborting\n"; } # # Read Sector 17 from CD which should contain a Boot Record Volume # descriptor. This descriptor contains at its start the text ($isoIdent) # CD001 and ($toritoSpec) # EL TORITO SPECIFICATION # see http://www.cdpage.com/Compact_Disc_Variations/eltoritoi.html # for details # $sector=getSector(17, 1, $imageFile ); ($boot, $isoIdent, $version, $toritoSpec, $unUsed, $bootP)= unpack( "Ca5CA32A32V", $sector ); if( $isoIdent ne "CD001" || $toritoSpec ne "EL TORITO SPECIFICATION" ){ die "This data image does not seem to be a bootable CD-image\n"; } # # Now fetch the sector of the booting catalog # $sector=getSector($bootP, 1, $imageFile ); print STDERR "Booting catalog starts at sector: $bootP \n"; # The first 32 bytes of this sector contains the validation entry for a # boot. The first byte has to be 01, the next byte determines the # architecture the image is designed for, where 00 is i86, 01 is PowerPC # and 02 is Mac. More data give info about manufacturer, etc. The # final two bytes must contain 0x55 and 0xAA respectively (as # defined by the El Torito standard). $validateEntry=substr($sector, 0, 32); ($header, $platform, $unUsed, $manufact, $unUsed, $five, $aa)= unpack( "CCvA24vCC", $validateEntry); if( $header != 1 || $five != 0x55 || $aa != 0xaa ){ die "Invalid Validation Entry on image \n"; } print STDERR "Manufacturer of CD: $manufact\n"; print STDERR "Image architecture: "; print STDERR "x86" if( $platform == 0 ); print STDERR "PowerPC" if( $platform == 1 ); print STDERR "Mac" if( $platform == 2 ); print STDERR "unknown ($platform)" if( $platform > 2 ); print STDERR "\n"; # # Now we examine the initial/defaultentry which follows the validate # entry and has a size of 32 bytes. $initialEntry=substr($sector, 32, 32); ($boot, $media, $loadSegment, $systemType, $unUsed, $sCount, $imgStart, $unUsed)=unpack( "CCvCCvVC", $initialEntry); if( $boot != 0x88 ){ die "Boot indicator in Initial/Default-Entry is not 0x88. CD is not bootable. \n"; } print STDERR "Boot media type is: "; if( $media == 0 ){ print STDERR "no emulation"; $count=0; } if( $media == 1 ){ print STDERR "1.2meg floppy"; $count=1200*1024/$vSecSize; } if( $media == 2 ){ print STDERR "1.44meg floppy"; $count=1440*1024/$vSecSize; } if( $media == 3 ){ print STDERR "2.88meg floppy"; $count=2880*1024/$vSecSize; } if( $media == 4 ){ print STDERR "harddisk"; $MBR=getSector($imgStart, 1, $imageFile ); $partition1=substr($MBR, 446, 16); ($unUsed, $firstSector, $partitionSize) = unpack( "A8VV", $partition1); $count=$firstSector + $partitionSize; } print STDERR "\n"; # Only use the internal sector counter if the real size is unknown # ($count==0) $cnt=$count==0?$sCount:$count; print STDERR "El Torito image starts at sector $imgStart and has $cnt sector(s) of $vSecSize Bytes\n"; # We are there: # Now read the bootimage to stdout $image=getSector($imgStart, $cnt, $imageFile); if( length($outputFilename) ){ writeOutputFile($outputFilename, $image); print STDERR "\nImage has been written to file \"$outputFilename\".\n"; }else{ print "$image"; print STDERR "Image has been written to stdout ....\n"; }