package Archive::Zip::Crypt;
use v5.008;
use strict;
use Archive::Zip qw/ :CONSTANTS :ERROR_CODES :PKZIP_CONSTANTS /;

=head1 NAME

Archive::Zip::Crypt - Unpacking of password protected archives for Archive::Zip

=head1 VERSION

Version 0.02

=cut

our $VERSION = '0.02';


=head1 SYNOPSIS

This is a little hack that adds the capability to unpack password-protected
archives to L<Archive::Zip>. It adds a C<password()> method to
L<Archive::Zip::Member> (passwords may be different for different archive
members!) and overwrites a few others so they can use the decryption
functionality, so it may break wit Archive::Zip versions >1.30. This is a pure
Perl implementation and really slow as bit-fiddling stuff in Perl tends to be.

    use Archive::Zip;
    use Archive::Zip::Crypt;

    my $zip = Archive::Zip->new($archive_name) or die "can't unzip";
    foreach my $member_name ($zip->memberNames) {
        my $member = $zip->memberNamed($member_name);
        next if $member->isDirectory;
        $member->password($password);
        my $contents = $zip->contents($member) or die "error accessing $member_name";
    }

Note: it is important to C<use Archive::Zip> first, so C<Archive::Zip::Crypt>
can smear its bugs all over the former's namespace.

=head1 METHODS

=head2 Archive::Zip::Member::password($password)

Set the encryption password on a member if called with an argument. Always
returns the current password.

=cut

=head1 AUTHOR

Matthias Bethke, C<< <matthias at towiski.de> >>

=head1 BUGS

None known but highly likely to be there. Please report any bugs or feature
requests to C<bug-archive-zip-crypt at rt.cpan.org>, or through the web
interface at
L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Archive-Zip-Crypt>.  I will be
notified, and then you'll automatically be notified of progress on your bug as
I make changes.

=head1 ACKNOWLEDGEMENTS

This was written as part of a project for 1&1 Internet AG. Thanks to them for supporting OSS!

=head1 LICENSE AND COPYRIGHT

Copyright 2008-2012 Matthias Bethke.

This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.


=cut

{ 
    my @crc32tab = (
        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
        0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
        0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
        0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
        0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
        0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
        0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
        0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
        0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
        0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
        0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
        0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
        0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
        0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
        0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
        0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
        0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
        0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
        0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
        0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
        0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
        0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
        0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
        0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
        0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
        0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
        0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
        0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
        0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
        0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
        0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
        0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
        0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
        0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
        0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
        0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
        0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
        0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
        0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
        0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
        0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
        0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
        0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
        0x2d02ef8d
    );

    # Straightforward port of unzip's crc32().
    # Other Perl implementations don't seem to behave the same
    sub _crypt_crc32 {
        return $crc32tab[($_[0] ^ $_[1]) & 0xff] ^ ($_[0] >> 8);
    }
}

# Do one scrambling step to obtain the next keystream byte
sub _update_keys {
    use integer;
    my $keyz = shift->{keyz};
    $keyz->[0] = _crypt_crc32($keyz->[0], $_[0]);
    $keyz->[1] += $keyz->[0] & 0xff;
    $keyz->[1] = ($keyz->[1] * 134775813) + 1;
    $keyz->[2] = _crypt_crc32($keyz->[2], $keyz->[1]>>24);
    my $t = ($keyz->[2] | 3) & 0xffff;
    $keyz->[3] = (($t * ($t ^ 1)) >> 8) & 0xff;
}

# Initialize keys with a password that must be in $self->{password}
sub _init_keys {
    my $self = shift;
    @{$self->{keyz}} = (0x12345678, 0x23456789, 0x34567890);
    _update_keys($self, ord($_)) foreach(unpack '(A1)*', $self->{password});
}

# Decrypt a string passed in as a parameter and overwrite(!) it with the decrypted version.
sub _decrypt {
    my $self = shift;
    my $out;

    foreach(unpack '(A1)*', ${$_[0]}) {
        my $t = chr($self->{keyz}[3] ^ ord($_));
        _update_keys($self, ord($t));
        $out .= $t;
    }
    ${$_[0]} = $out;
}

no warnings 'redefine';     # Prepare for ugliness

# New public method: set decryption password on a member
*Archive::Zip::Member::password = sub {
    my ($self, $pw) = @_;
    defined $pw and $self->{password} = $pw;
    $self->{password};
};

# Replaces original method
*Archive::Zip::Member::readChunk = sub {
    my ( $self, $chunkSize ) = @_;

    if ( $self->readIsDone() ) {
        $self->endRead();
        my $dummy = '';
        return ( \$dummy, AZ_STREAM_END );
    }

    $chunkSize = $Archive::Zip::ChunkSize if not defined $chunkSize;
    $chunkSize = $self->_readDataRemaining()
      if $chunkSize > $self->_readDataRemaining();

    my $buffer = '';
    my $outputRef;
    my ( $bytesRead, $status ) = $self->_readRawChunk( \$buffer, $chunkSize );
    return ( \$buffer, $status ) unless $status == AZ_OK;

    # Begin patch
    if($self->isEncrypted) {
        unless($self->{readOffset}) {
            croak("can't decrypt, use \$member->password('mypassword') first") unless defined $self->{password};
            Archive::Zip::Crypt::_init_keys($self);
        }
        Archive::Zip::Crypt::_decrypt($self,\$buffer);
        $buffer = substr($buffer,12) unless $self->{readOffset};
    }
    # End patch

    $self->{'readDataRemaining'} -= $bytesRead;
    $self->{'readOffset'} += $bytesRead;

    if ( $self->compressionMethod() == COMPRESSION_STORED ) {
        $self->{'crc32'} = $self->computeCRC32( $buffer, $self->{'crc32'} );
    }

    ( $outputRef, $status ) = &{ $self->{'chunkHandler'} }( $self, \$buffer );
    $self->{'writeOffset'} += length($$outputRef);

    $self->endRead()
      if $self->readIsDone();

    return ( $outputRef, $status );
};

# Replaces original method. Avoids patching larger methods just to fool them
# about encryption. Yes, it's ugly :)
*Archive::Zip::Member::isEncrypted = sub {
    return 0 if((caller(1))[3] =~ /::(?:extractToFile(?:Handle|Named))$/);
    shift->bitFlag() & GPBF_ENCRYPTED_MASK;
};


# Replaces original method. Just takes the 12 bytes of encryption header into
# account if present
*Archive::Zip::ZipFileMember::_skipLocalFileHeader = sub {
    my $self = shift;
    my $header;
    my $bytesRead = $self->fh()->read( $header, LOCAL_FILE_HEADER_LENGTH );
    if ( $bytesRead != LOCAL_FILE_HEADER_LENGTH ) {
        return _ioError("reading local file header");
    }
    my $fileNameLength;
    my $extraFieldLength;
    my $bitFlag;
    (
        undef,    # $self->{'versionNeededToExtract'},
        $bitFlag,
        undef,    # $self->{'compressionMethod'},
        undef,    # $self->{'lastModFileDateTime'},
        undef,    # $crc32,
        undef,    # $compressedSize,
        undef,    # $uncompressedSize,
        $fileNameLength,
        $extraFieldLength
    ) = unpack( LOCAL_FILE_HEADER_FORMAT, $header );

    if ($fileNameLength) {
        $self->fh()->seek( $fileNameLength, IO::Seekable::SEEK_CUR )
          or return _ioError("skipping local file name");
    }

    if ($extraFieldLength) {
        $bytesRead =
          $self->fh()->read( $self->{'localExtraField'}, $extraFieldLength );
        if ( $bytesRead != $extraFieldLength ) {
            return _ioError("reading local extra field");
        }
    }

    $self->{'dataOffset'} = $self->fh()->tell();

    if ( $bitFlag & GPBF_HAS_DATA_DESCRIPTOR_MASK ) {

        # Read the crc32, compressedSize, and uncompressedSize from the
        # extended data descriptor, which directly follows the compressed data.
        #
        # Skip over the compressed file data (assumes that EOCD compressedSize
        # was correct)
        $self->fh()->seek( $self->{'compressedSize'}, IO::Seekable::SEEK_CUR )
          or return _ioError("seeking to extended local header");

        # these values should be set correctly from before.
        my $oldCrc32            = $self->{'eocdCrc32'};
        my $oldCompressedSize   = $self->{'compressedSize'};
        my $oldUncompressedSize = $self->{'uncompressedSize'};

        my $status = $self->_readDataDescriptor();
        return $status unless $status == AZ_OK;

        # Begin patch
        # Account for 12 bytes of encryption header in $oldUncompressedSize for encrypted members
        # TODO uncompressedSize seems to differ only for some types of archives?
        $oldUncompressedSize -= 12 if($self->isEncrypted and $oldUncompressedSize != $self->{'uncompressedSize'});
        # End patch

        return _formatError(
            "CRC or size mismatch while skipping data descriptor")
          if ( $oldCrc32 != $self->{'crc32'}
            || $oldUncompressedSize != $self->{'uncompressedSize'} );
    }

    return AZ_OK;
};

1;
