dpkg/scripts/Dpkg/Checksums.pm

# Copyright © 2008 Frank Lichtenheld <djpig@debian.org>
# Copyright © 2010 Raphaël Hertzog <hertzog@debian.org>
#
# 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, see <http://www.gnu.org/licenses/>.

package Dpkg::Checksums;

use strict;
use warnings;

our $VERSION = "1.00";

use Dpkg;
use Dpkg::Gettext;
use Dpkg::ErrorHandling;
use Dpkg::IPC;

use base qw(Exporter);
our @EXPORT = qw(checksums_get_list checksums_is_supported
		 checksums_get_property);

=head1 NAME

Dpkg::Checksums - generate and manipulate file checksums

=head1 DESCRIPTION

This module provides an object that can generate and manipulate
various file checksums as well as some methods to query information
about supported checksums.

=head1 EXPORTED FUNCTIONS

=over 4

=cut

my $CHECKSUMS = {
    "md5" => {
	"program" => [ "md5sum" ],
	"regex" => qr/[0-9a-f]{32}/,
    },
    "sha1" => {
	"program" => [ "sha1sum" ],
	"regex" => qr/[0-9a-f]{40}/,
    },
    "sha256" => {
	"program" => [ "sha256sum" ],
	"regex" => qr/[0-9a-f]{64}/,
    },
};

=item @list = checksums_get_list()

Returns the list of supported checksums algorithms.

=cut

sub checksums_get_list() {
    return sort keys %{$CHECKSUMS};
}

=item $bool = checksums_is_supported($alg)

Returns a boolean indicating whether the given checksum algorithm is
supported. The checksum algorithm is case-insensitive.

=cut

sub checksums_is_supported($) {
    my ($alg) = @_;
    return exists $CHECKSUMS->{lc($alg)};
}

=item $value = checksums_get_property($alg, $property)

Returns the requested property of the checksum algorithm. Returns undef if
either the property or the checksum algorithm doesn't exist. Valid
properties currently include "program" (returns an array reference with
a program name and parameters required to compute the checksum of the
filename given as last parameter) and "regex" for the regular expression
describing the common string representation of the checksum (as output
by the program that generates it).

=cut

sub checksums_get_property($$) {
    my ($alg, $property) = @_;
    return undef unless checksums_is_supported($alg);
    return $CHECKSUMS->{lc($alg)}{$property};
}

=back

=head1 OBJECT METHODS

=over 4

=item my $ck = Dpkg::Checksums->new()

Create a new Dpkg::Checksums object. This object is able to store
the checksums of several files to later export them or verify them.

=cut

sub new {
    my ($this, %opts) = @_;
    my $class = ref($this) || $this;

    my $self = {};
    bless $self, $class;
    $self->reset();

    return $self;
}

=item $ck->reset()

Forget about all checksums stored. The object is again in the same state
as if it was newly created.

=cut

sub reset {
    my ($self) = @_;
    $self->{files} = [];
    $self->{checksums} = {};
    $self->{size} = {};
}

=item $ck->add_from_file($filename, %opts)

Add checksums information for the file $filename. The file must exists
for the call to succeed. If you don't want the given filename to appear
when you later export the checksums you might want to set the "key"
option with the public name that you want to use. Also if you don't want
to generate all the checksums, you can pass an array reference of the
wanted checksums in the "checksums" option.

It the object already contains checksums information associated the
filename (or key), it will error out if the newly computed information
does not match what's stored.

=cut

sub add_from_file {
    my ($self, $file, %opts) = @_;
    my $key = exists $opts{key} ? $opts{key} : $file;
    my @alg;
    if (exists $opts{checksums}) {
	push @alg, map { lc($_) } @{$opts{checksums}};
    } else {
	push @alg, checksums_get_list();
    }

    push @{$self->{files}}, $key unless exists $self->{size}{$key};
    (my @s = stat($file)) || syserr(_g("cannot fstat file %s"), $file);
    if (exists $self->{size}{$key} and $self->{size}{$key} != $s[7]) {
	error(_g("File %s has size %u instead of expected %u"),
	      $file, $s[7], $self->{size}{$key});
    }
    $self->{size}{$key} = $s[7];

    foreach my $alg (@alg) {
	my @exec = (@{$CHECKSUMS->{$alg}{"program"}}, $file);
	my $regex = $CHECKSUMS->{$alg}{"regex"};
	my $output;
	spawn('exec' => \@exec, to_string => \$output);
	if ($output =~ /^($regex)(\s|$)/m) {
	    my $newsum = $1;
	    if (exists $self->{checksums}{$key}{$alg} and
		$self->{checksums}{$key}{$alg} ne $newsum) {
		error(_g("File %s has checksum %s instead of expected %s (algorithm %s)"),
		      $file, $newsum, $self->{checksums}{$key}{$alg}, $alg);
	    }
	    $self->{checksums}{$key}{$alg} = $newsum;
	} else {
	    error(_g("checksum program gave bogus output `%s'"), $output);
	}
    }
}

=item $ck->add_from_string($alg, $value)

Add checksums of type $alg that are stored in the $value variable.
$value can be multi-lines, each line should be a space separated list
of checksum, file size and filename. Leading or trailing spaces are
not allowed.

It the object already contains checksums information associated to the
filenames, it will error out if the newly read information does not match
what's stored.

=cut

sub add_from_string {
    my ($self, $alg, $fieldtext) = @_;
    $alg = lc($alg);
    my $rx_fname = qr/[0-9a-zA-Z][-+:.,=0-9a-zA-Z_~]+/;
    my $regex = checksums_get_property($alg, "regex");
    my $checksums = $self->{checksums};

    for my $checksum (split /\n */, $fieldtext) {
	next if $checksum eq '';
	unless ($checksum =~ m/^($regex)\s+(\d+)\s+($rx_fname)$/) {
	    error(_g("invalid line in %s checksums string: %s"),
		  $alg, $checksum);
	}
	my ($sum, $size, $file) = ($1, $2, $3);
	if (exists($checksums->{$file}{$alg})
	    and $checksums->{$file}{$alg} ne $sum) {
	    error(_g("Conflicting checksums \`%s\' and \`%s' for file \`%s'"),
		  $checksums->{$file}{$alg}, $sum, $file);
	}
	if (exists $self->{size}{$file} and $self->{size}{$file} != $size) {
	    error(_g("Conflicting file sizes \`%u\' and \`%u' for file \`%s'"),
		  $self->{size}{$file}, $size, $file);
	}
	push @{$self->{files}}, $file unless exists $self->{size}{$file};
	$checksums->{$file}{$alg} = $sum;
	$self->{size}{$file} = $size;
    }
}

=item $ck->add_from_control($control, %opts)

Read checksums from Checksums-* fields stored in the Dpkg::Control object
$control. It uses $self->add_from_string() on the field values to do the
actual work.

If the option "use_files_for_md5" evaluates to true, then the "Files"
field is used in place of the "Checksums-Md5" field. By default the option
is false.

=cut

sub add_from_control {
    my ($self, $control, %opts) = @_;
    $opts{use_files_for_md5} = 0 unless exists $opts{use_files_for_md5};
    foreach my $alg (checksums_get_list()) {
	my $key = "Checksums-$alg";
	$key = "Files" if ($opts{use_files_for_md5} and $alg eq "md5");
	if (exists $control->{$key}) {
	    $self->add_from_string($alg, $control->{$key});
	}
    }
}

=item @files = $ck->get_files()

Return the list of files whose checksums are stored in the object.

=cut

sub get_files {
    my ($self) = @_;
    return @{$self->{files}};
}

=item $bool = $ck->has_file($file)

Return true if we have checksums for the given file. Returns false
otherwise.

=cut

sub has_file {
    my ($self, $file) = @_;
    return exists $self->{size}{$file};
}

=item $ck->remove_file($file)

Remove all checksums of the given file.

=cut

sub remove_file {
    my ($self, $file) = @_;
    return unless $self->has_file($file);
    delete $self->{'checksums'}{$file};
    delete $self->{'size'}{$file};
    @{$self->{'files'}} = grep { $_ ne $file } $self->get_files();
}

=item $checksum = $ck->get_checksum($file, $alg)

Return the checksum of type $alg for the requested $file. This will not
compute the checksum but only return the checksum stored in the object, if
any.

If $alg is not defined, it returns a reference to a hash: keys are
the checksum algorithms and values are the checksums themselves. The
hash returned must not be modified, it's internal to the object.

=cut

sub get_checksum {
    my ($self, $file, $alg) = @_;
    $alg = lc($alg) if defined $alg;
    if (exists $self->{checksums}{$file}) {
	return $self->{checksums}{$file} unless defined $alg;
	return $self->{checksums}{$file}{$alg};
    }
    return undef;
}

=item $size = $ck->get_size($file)

Return the size of the requested file if it's available in the object.

=cut

sub get_size {
    my ($self, $file) = @_;
    return $self->{size}{$file};
}

=item $ck->export_to_string($alg, %opts)

Return a multi-line string containing the checksums of type $alg. The
string can be stored as-is in a Checksum-* field of a Dpkg::Control
object.

=cut

sub export_to_string {
    my ($self, $alg, %opts) = @_;
    my $res = "";
    foreach my $file ($self->get_files()) {
	my $sum = $self->get_checksum($file, $alg);
	my $size = $self->get_size($file);
	next unless defined $sum and defined $size;
	$res .= "\n$sum $size $file";
    }
    return $res;
}

=item $ck->export_to_control($control, %opts)

Export the checksums in the Checksums-* fields of the Dpkg::Control
$control object.

=cut

sub export_to_control {
    my ($self, $control, %opts) = @_;
    $opts{use_files_for_md5} = 0 unless exists $opts{use_files_for_md5};
    foreach my $alg (checksums_get_list()) {
	my $key = "Checksums-$alg";
	$key = "Files" if ($opts{use_files_for_md5} and $alg eq "md5");
	$control->{$key} = $self->export_to_string($alg, %opts);
    }
}

=back

=head1 AUTHOR

Raphaël Hertzog <hertzog@debian.org>.

=cut

1;