mirror of
https://github.com/linuxboot/linuxboot
synced 2024-11-21 23:59:59 +00:00
151 lines
3.6 KiB
Perl
Executable File
151 lines
3.6 KiB
Perl
Executable File
#!/usr/bin/perl
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# Clean all non-deterministric fields in a newc cpio file
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#
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# Items fixed:
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# Files are sorted by name
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# Inode numbers are based on the hash of the filename
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# File timestamp is set to 1970-01-01T00:00:00
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# uid/gid are set to root
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# check field is zeroed
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# nlinks is set to zero, since the filesystem manages it
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#
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use warnings;
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use strict;
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use Data::Dumper;
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use Digest::MD5 'md5_hex';
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# struct cpio_newc_header {
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# char c_magic[6]; -6
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# char c_ino[8]; -- set to a monotonic value 0
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# char c_mode[8]; 8
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# char c_uid[8]; 16
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# char c_gid[8]; 24
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# char c_nlink[8]; 32
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# char c_mtime[8]; 40 -- set to zero
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# char c_filesize[8]; 48
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# char c_devmajor[8]; 56
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# char c_devminor[8]; 64
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# char c_rdevmajor[8]; 72
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# char c_rdevminor[8]; 80
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# char c_namesize[8]; 88
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# char c_check[8]; 96
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# }; // 104
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# followed by namesize bytes of name (padded to be a multiple of 4)
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# followed dby filesize bytes of file (padded to be a multiple of 4)
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# Read the entire file at once
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undef $/;
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# Generate a map of all of the files in the cpio archive
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# This will also merge multiple cpio files
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my %entries;
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my $trailer;
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while(<>)
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{
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for(my $i = 0 ; $i < length $_ ; )
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{
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my $magic = substr($_, $i, 6);
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if ($magic ne "070701")
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{
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die "$ARGV: offset $i: invalid magic '$magic'\n";
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}
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my $namesize = substr($_, $i + 6+88, 8);
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my $filesize = substr($_, $i + 6+48, 8);
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if ($namesize =~ /[^0-9A-Fa-f]/)
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{
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die "$ARGV: offset $i: invalid characters in namesize '$namesize'\n";
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}
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if ($filesize =~ /[^0-9A-Fa-f]/)
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{
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die "$ARGV: offset $i: invalid characters in filesize '$filesize'\n";
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}
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# Convert them to hex
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$namesize = hex $namesize;
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$filesize = hex $filesize;
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#print STDERR "name: '$namesize', filesize: '$filesize'\n";
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my $name = substr($_, $i + 6+104, $namesize);
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#print STDERR Dumper($name);
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# Align the header size to be a multiple of four bytes
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my $entry_size = (6+104 + $namesize + 3) & ~3;
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$entry_size += ($filesize + 3) & ~3;
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my $entry = substr($_, $i, $entry_size);
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$i += $entry_size;
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if ($name =~ /^TRAILER!!!/)
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{
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$trailer = $entry;
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last;
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}
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$entries{$name} = $entry;
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}
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die "$ARGV: No trailer!\n" unless $trailer;
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}
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# Apply the cleaning to each one
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for my $filename (sort keys %entries)
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{
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my $entry = $entries{$filename};
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my $zero = sprintf "%08x", 0;
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# inodes are hashed to be deterministic
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# and hopefully not colliding
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my $md5 = md5_hex($filename);
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my $d0 = hex substr($md5, 0, 8) ;
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my $d1 = hex substr($md5, 8, 8) ;
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my $d2 = hex substr($md5, 16, 8) ;
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my $d3 = hex substr($md5, 24, 8) ;
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my $hash = sprintf "%08x", $d0 ^ $d1 ^ $d2 ^ $d3;
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#warn "$filename: $md5 -> $hash\n";
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substr($entry, 6 + 0, 8) = $hash;
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# set timestamps to zero
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substr($entry, 6 + 40, 8) = $zero;
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# remove group/user permissions, leaving only
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# the owner bits intact.
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my $mode = hex substr($entry, 6 + 8, 8);
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$mode &= ~0077;
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#$mode |= $mode >> 3 | $mode >> 6;
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substr($entry, 6 + 8, 8) = sprintf "%08X", $mode;
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# set uid/gid to zero
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substr($entry, 6 + 16, 8) = $zero;
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substr($entry, 6 + 24, 8) = $zero;
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# zero out the nlinks, since it is managed by the real fs
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substr($entry, 6 + 32, 8) = $zero;
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# set the device major/minor to zero
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substr($entry, 6 + 56, 8) = $zero;
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substr($entry, 6 + 64, 8) = $zero;
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# set check to zero
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substr($entry, 6 + 96, 8) = $zero;
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$entries{$filename} = $entry;
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}
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# Print them in sorted order
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for my $filename (sort keys %entries)
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{
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my $entry = $entries{$filename};
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print $entry;
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}
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# Output the trailer to mark the end of the archive
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print $trailer;
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__END__
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