addChecksum.pl

#!/usr/bin/env perl

# Copyright 2011 Wladimir Palant
# https://palant.de/
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

#############################################################################
# Script to add checksums to downloadable subscriptions. The checksum will  #
# be validated by Adblock Plus on download and checksum mismatches          #      
# (broken downloads) will be rejected.                                      #
#                                                                           #
# To add a checksum to a subscription file, run the script like this:       #
#                                                                           #
#   perl addChecksum.pl subscription.txt                                    #
#                                                                           #
# Note: your subscription file should be saved in UTF-8 encoding, otherwise #
# the generated checksum might be incorrect.                                #
#                                                      AdblockPlus.Org      #
#############################################################################

use strict;
use warnings;
use Path::Tiny;
use Digest::MD5 qw(md5_base64);
use Encode qw(encode_utf8);
use POSIX qw(strftime);
use feature 'unicode_strings';

die "Usage: $^X $0 subscription.txt\n" unless @ARGV;

my $file = shift;

die "Specified file: $file doesn't exist!\n" unless (-e $file);

my $data = path($file)->slurp_utf8;

# Get existing checksum

$data =~ /^.*!\s*checksum[\s\-:]+([\w\+\/=]+).*\n/gmi;
my $oldchecksum = $1;

# Remove already existing checksum

$data =~ s/^.*!\s*checksum[\s\-:]+([\w\+\/=]+).*\n//gmi;

# Calculate new checksum: remove all CR symbols and empty
# lines and get an MD5 checksum of the result (base64-encoded,
# without the trailing = characters)

my $checksumData = $data;
$checksumData =~ s/\r//g;
$checksumData =~ s/\n+/\n/g;

# Calculate new checksum

my $checksum = md5_base64(encode_utf8($checksumData));

# If the old checksum matches the new one die
die "List has not changed.\n" if (($oldchecksum) and ($checksum eq $oldchecksum));

# Update the date and time

my $updated = strftime("%Y-%m-%d %H:%M %S UTC", gmtime);
$data =~ s/(^.*!.*(Last modified|Updated):\s*)(.*)\s*$/$1$updated/gmi if ($data =~ m/^.*!.*(Last modified|Updated)/gmi);

# Update version

my $version = strftime("%Y%m%d%H%M%S" ,gmtime);
$data =~ s/^.*!\s*Version:.*/! Version: $version/gmi;

# Recalculate the checksum as we've altered the date

$checksumData = $data;
$checksumData =~ s/\r//g;
$checksumData =~ s/\n+/\n/g;
$checksum = md5_base64(encode_utf8($checksumData));

# Insert checksum into the file

$data =~ s/(\r?\n)/$1! Checksum: $checksum$1/;

path($file)->spew_utf8($data);