+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+#
+# Standalone PSGI app to handle HTTP(s) unsubscribe links generated
+# by milters like examples/unsubscribe.milter to mailing lists.
+#
+# This does not depend on any other modules in the PublicInbox::*
+# and ought to be usable with any mailing list software.
+package PublicInbox::Unsubscribe;
+use strict;
+use warnings;
+use Crypt::CBC;
+use Plack::Util;
+use MIME::Base64 qw(decode_base64url);
+my $CODE_URL = 'git://80x24.org/public-inbox.git';
+my @CT_HTML = ('Content-Type', 'text/html; charset=UTF-8');
+
+sub new {
+ my ($class, %opt) = @_;
+ my $key_file = $opt{key_file};
+ defined $key_file or die "`key_file' needed";
+ open my $fh, '<', $key_file or die
+ "failed to open key_file=$key_file: $!\n";
+ my ($key, $iv);
+ if (read($fh, $key, 8) != 8 || read($fh, $iv, 8) != 8 ||
+ read($fh, my $end, 8) != 0) {
+ die "key_file must be 16 bytes\n";
+ }
+
+ # these parameters were chosen to generate shorter parameters
+ # to reduce the possibility of copy+paste errors
+ my $cipher = Crypt::CBC->new(-key => $key,
+ -iv => $iv,
+ -header => 'none',
+ -cipher => 'Blowfish');
+
+ my $e = $opt{owner_email} or die "`owner_email' not specified\n";
+ my $unsubscribe = $opt{unsubscribe} or
+ die "`unsubscribe' callback not given\n";
+
+ bless {
+ pi_config => $opt{pi_config}, # PublicInbox::Config
+ owner_email => $opt{owner_email},
+ cipher => $cipher,
+ unsubscribe => $unsubscribe,
+ contact => qq(<a\nhref="mailto:$e">$e</a>),
+ code_url => $opt{code_url} || $CODE_URL,
+ confirm => $opt{confirm},
+ }, $class;
+}
+
+# entry point for PSGI
+sub call {
+ my ($self, $env) = @_;
+ my $m = $env->{REQUEST_METHOD};
+ if ($m eq 'GET' || $m eq 'HEAD') {
+ $self->{confirm} ? confirm_prompt($self, $env)
+ : finalize_unsub($self, $env);
+ } elsif ($m eq 'POST') {
+ finalize_unsub($self, $env);
+ } else {
+ r($self, 405,
+ Plack::Util::encode_html($m).' method not allowed');
+ }
+}
+
+sub _user_list_addr {
+ my ($self, $env) = @_;
+ my ($blank, $u, $list) = split('/', $env->{PATH_INFO});
+
+ if (!defined $u || $u eq '') {
+ return r($self, 400, 'Bad request',
+ 'Missing encrypted email address in path component');
+ }
+ if (!defined $list && $list eq '') {
+ return r($self, 400, 'Bad request',
+ 'Missing mailing list name in path component');
+ }
+ my $user = eval { $self->{cipher}->decrypt(decode_base64url($u)) };
+ if (!defined $user) {
+ my $err = quotemeta($@);
+ my $errors = $env->{'psgi.errors'};
+ $errors->print("error decrypting: $u\n");
+ $errors->print("$_\n") for split("\n", $err);
+ return r($self, 400, 'Bad request', "Failed to decrypt: $u");
+ }
+
+ # The URLs are too damn long if we have the encrypted domain
+ # name in the query string
+ if (index($list, '@') < 0) {
+ my $host = (split(':', $env->{HTTP_HOST}))[0];
+ $list .= '@'.$host;
+ }
+ ($user, $list);
+}
+
+sub confirm_prompt { # on GET
+ my ($self, $env) = @_;
+ my ($user_addr, $list_addr) = _user_list_addr($self, $env);
+ return $user_addr if ref $user_addr;
+
+ my $xl = Plack::Util::encode_html($list_addr);
+ my $xu = Plack::Util::encode_html($user_addr);
+ my @body = (
+ "Confirmation required to remove", '',
+ "\t$xu", '',
+ "from the mailing list at", '',
+ "\t$xl", '',
+ 'You will get one last email once you hit "Confirm" below:',
+ qq(</pre><form\nmethod=post\naction="">) .
+ qq(<input\ntype=submit\nvalue="Confirm" />) .
+ '</form><pre>');
+
+ push @body, archive_info($self, $env, $list_addr);
+
+ r($self, 200, "Confirm unsubscribe for $xl", @body);
+}
+
+sub finalize_unsub { # on POST
+ my ($self, $env) = @_;
+ my ($user_addr, $list_addr) = _user_list_addr($self, $env);
+ return $user_addr if ref $user_addr;
+
+ my @archive = archive_info($self, $env, $list_addr);
+ if (my $err = $self->{unsubscribe}->($user_addr, $list_addr)) {
+ return r($self, 500, Plack::Util::encode_html($err), @archive);
+ }
+
+ my $xl = Plack::Util::encode_html($list_addr);
+ r($self, 200, "Unsubscribed from $xl",
+ 'You may get one final goodbye message', @archive);
+}
+
+sub r {
+ my ($self, $code, $title, @body) = @_;
+ [ $code, [ @CT_HTML ], [
+ "<html><head><title>$title</title></head><body><pre>".
+ join("\n", "<b>$title</b>\n", @body) . '</pre><hr />'.
+ "<pre>This page is available under AGPL-3.0+\n" .
+ "git clone $self->{code_url}\n" .
+ qq(Email $self->{contact} if you have any questions).
+ '</pre></body></html>'
+ ] ];
+}
+
+sub archive_info {
+ my ($self, $env, $list_addr) = @_;
+ my $archive_url = $self->{archive_urls}->{$list_addr};
+
+ unless ($archive_url) {
+ if (my $config = $self->{pi_config}) {
+ # PublicInbox::Config::lookup
+ my $inbox = $config->lookup($list_addr);
+ # PublicInbox::Inbox::base_url
+ $archive_url = $inbox->base_url if $inbox;
+ }
+ }
+
+ # protocol-relative URL: "//example.com/" => "https://example.com/"
+ if ($archive_url =~ m!\A//!) {
+ $archive_url = "$env->{'psgi.url_scheme'}:$archive_url";
+ }
+
+ # maybe there are other places where we could map
+ # list_addr => archive_url without ~/.public-inbox/config
+ if ($archive_url) {
+ $archive_url = Plack::Util::encode_html($archive_url);
+ ('',
+ 'HTML and git clone-able archives are available at:',
+ qq(<a\nhref="$archive_url">$archive_url</a>))
+ } else {
+ ('',
+ 'There ought to be archives for this list,',
+ 'but unfortunately the admin did not configure '.
+ __PACKAGE__. ' to show you the URL');
+ }
+}
+
+1;