# -*- Mode: perl; indent-tabs-mode: nil -*-
#
# The contents of this file are subject to the Mozilla Public
# License Version 1.1 (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.mozilla.org/MPL/
#
# Software distributed under the License is distributed on an "AS
# IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
# implied. See the License for the specific language governing
# rights and limitations under the License.
#
# The Original Code is the Bugzilla SecureMail Extension
#
# The Initial Developer of the Original Code is the Mozilla Foundation.
# Portions created by Mozilla are Copyright (C) 2008 Mozilla Foundation.
# All Rights Reserved.
#
# Contributor(s): Max Kanat-Alexander <mkanat@bugzilla.org>
#                 Gervase Markham <gerv@gerv.net>

package Bugzilla::Extension::SecureMail;

use 5.10.1;
use strict;
use warnings;

use base qw(Bugzilla::Extension);

use Bugzilla::Attachment;
use Bugzilla::Comment;
use Bugzilla::Group;
use Bugzilla::Object;
use Bugzilla::User;
use Bugzilla::Util qw(trim trick_taint is_7bit_clean);
use Bugzilla::Error;
use Bugzilla::Mailer;

use Crypt::OpenPGP::Armour;
use Crypt::OpenPGP::KeyRing;
use Crypt::OpenPGP;
use Crypt::SMIME;
use Email::MIME::ContentType qw(parse_content_type);
use Encode;
use HTML::Tree;

our $VERSION = '0.5';

use constant SECURE_NONE => 0;
use constant SECURE_BODY => 1;
use constant SECURE_ALL  => 2;

##############################################################################
# Creating new columns
#
# secure_mail boolean in the 'gselect id from groups where secure_mailroups' table - whether to send secure mail
# public_key text in the 'profiles' table - stores public key
##############################################################################
sub install_update_db {
    my ($self, $args) = @_;

    my $dbh = Bugzilla->dbh;
    $dbh->bz_add_column('groups', 'secure_mail',
                        {TYPE => 'BOOLEAN', NOTNULL => 1, DEFAULT => 0});
    $dbh->bz_add_column('profiles', 'public_key', { TYPE => 'LONGTEXT' });
}

##############################################################################
# Maintaining new columns
##############################################################################

BEGIN {
    *Bugzilla::Group::secure_mail = \&_group_secure_mail;
    *Bugzilla::User::public_key   = \&_user_public_key;
    *Bugzilla::securemail_groups = \&_securemail_groups;
}

sub _group_secure_mail { return $_[0]->{'secure_mail'}; }

sub _securemail_groups {
    return Bugzilla->dbh->selectcol_arrayref("SELECT name FROM groups WHERE secure_mail = 1") // [];
}

# We want to lazy-load the public_key.
sub _user_public_key {
    my $self = shift;
    if (!exists $self->{public_key}) {
        ($self->{public_key}) = Bugzilla->dbh->selectrow_array(
            "SELECT public_key FROM profiles WHERE userid = ?",
            undef,
            $self->id
        );
    }
    return $self->{public_key};
}

# Make sure generic functions know about the additional fields in the user
# and group objects.
sub object_columns {
    my ($self, $args) = @_;
    my $class = $args->{'class'};
    my $columns = $args->{'columns'};

    if ($class->isa('Bugzilla::Group')) {
        my $dbh = Bugzilla->dbh;
        if ($dbh->bz_column_info($class->DB_TABLE, 'secure_mail')) {
            push @$columns, 'secure_mail';
        }
    }
}

# Plug appropriate validators so we can check the validity of the two
# fields created by this extension, when new values are submitted.
sub object_validators {
    my ($self, $args) = @_;
    my %args = %{ $args };
    my ($invocant, $validators) = @args{qw(class validators)};

    if ($invocant->isa('Bugzilla::Group')) {
        $validators->{'secure_mail'} = \&Bugzilla::Object::check_boolean;
    }
    elsif ($invocant->isa('Bugzilla::User')) {
        $validators->{'public_key'} = sub {
            my ($self, $value) = @_;
            $value = trim($value) || '';

            return $value if $value eq '';

            if ($value =~ /PUBLIC KEY/) {
                # PGP keys must be ASCII-armoured.
                if (!Crypt::OpenPGP::Armour->unarmour($value)) {
                    ThrowUserError('securemail_invalid_key',
                                   { errstr => Crypt::OpenPGP::Armour->errstr });
                }
            }
            elsif ($value =~ /BEGIN CERTIFICATE/) {
                # S/MIME Keys must be in PEM format (Base64-encoded X.509)
                #
                # Crypt::SMIME seems not to like tainted values - it claims
                # they aren't scalars!
                trick_taint($value);

                my $smime = Crypt::SMIME->new();
                eval {
                    $smime->setPublicKey([$value]);
                };
                if ($@) {
                    ThrowUserError('securemail_invalid_key',
                                   { errstr => $@ });
                }
            }
            else {
                ThrowUserError('securemail_invalid_key');
            }

            return $value;
        };
    }
}

# When creating a 'group' object, set up the secure_mail field appropriately.
sub object_before_create {
    my ($self, $args) = @_;
    my $class = $args->{'class'};
    my $params = $args->{'params'};

    if ($class->isa('Bugzilla::Group')) {
        $params->{secure_mail} = Bugzilla->cgi->param('secure_mail');
    }
}

# On update, make sure the updating process knows about our new columns.
sub object_update_columns {
    my ($self, $args) = @_;
    my $object  = $args->{'object'};
    my $columns = $args->{'columns'};

    if ($object->isa('Bugzilla::Group')) {
        # This seems like a convenient moment to extract this value...
        $object->set('secure_mail', Bugzilla->cgi->param('secure_mail'));

        push(@$columns, 'secure_mail');
    }
    elsif ($object->isa('Bugzilla::User')) {
        push(@$columns, 'public_key');
    }
}

# Handle the setting and changing of the public key.
sub user_preferences {
    my ($self, $args) = @_;
    my $tab     = $args->{'current_tab'};
    my $save    = $args->{'save_changes'};
    my $handled = $args->{'handled'};
    my $vars    = $args->{'vars'};
    my $params  = Bugzilla->input_params;

    return unless $tab eq 'securemail';

    # Create a new user object so we don't mess with the main one, as we
    # don't know where it's been...
    my $user = new Bugzilla::User(Bugzilla->user->id);

    if ($save) {
        $user->set('public_key', $params->{'public_key'});
        $user->update();

        # Send user a test email
        if ($user->public_key) {
            _send_test_email($user);
            $vars->{'test_email_sent'} = 1;
        }
    }

    $vars->{'public_key'} = $user->public_key;

    # Set the 'handled' scalar reference to true so that the caller
    # knows the panel name is valid and that an extension took care of it.
    $$handled = 1;
}

sub template_before_process {
    my ($self, $args) = @_;
    my $file = $args->{'file'};
    my $vars = $args->{'vars'};

    # Bug dependency emails contain the subject of the dependent bug
    # right before the diffs when a status has gone from open/closed
    # or closed/open. We need to sanitize the subject of change.blocker
    # similar to how we do referenced bugs
    return unless
        $file eq 'email/bugmail.html.tmpl'
        || $file eq 'email/bugmail.txt.tmpl';

    if (defined $vars->{diffs}) {
        foreach my $change (@{ $vars->{diffs} }) {
            next if !defined $change->{blocker};
            if (grep($_->secure_mail, @{ $change->{blocker}->groups_in })) {
                $change->{blocker}->{short_desc} = "(Secure bug)";
            }
        }
    }
}

sub _send_test_email {
    my ($user) = @_;
    my $template = Bugzilla->template_inner($user->settings->{'lang'}->{'value'});

    my $vars = {
        to_user => $user->email,
    };

    my $msg = "";
    $template->process("account/email/securemail-test.txt.tmpl", $vars, \$msg)
        || ThrowTemplateError($template->error());

    MessageToMTA($msg);
}

##############################################################################
# Encrypting the email
##############################################################################

# determine if the bug should be encrypted at the time it is generated
sub bugmail_enqueue {
    my ($self, $args) = @_;
    my $vars = $args->{vars};
    if (_should_secure_bug($vars->{bug})) {
        $vars->{bugzilla_encrypt} = 1;
    }
}

sub bugmail_generate {
    my ($self, $args) = @_;
    my $vars = $args->{vars};
    my $email = $args->{email};
    if ($vars->{bugzilla_encrypt}) {
        $email->header_set('X-Bugzilla-Encrypt', 1);
    }
}

sub mailer_before_send {
    my ($self, $args) = @_;

    my $email = $args->{'email'};
    my $body  = $email->body;

    # Decide whether to make secure.
    # This is a bit of a hack; it would be nice if it were more clear
    # what sort a particular email is.
    my $is_bugmail      = $email->header('X-Bugzilla-Status') ||
                          $email->header('X-Bugzilla-Type') eq 'request';
    my $is_passwordmail = !$is_bugmail && ($body =~ /cfmpw.*cxlpw/s);
    my $is_test_email   = $email->header('X-Bugzilla-Type') =~ /securemail-test/ ? 1 : 0;
    my $is_whine_email  = $email->header('X-Bugzilla-Type') eq 'whine' ? 1 : 0;
    my $encrypt_header  = $email->header('X-Bugzilla-Encrypt') ? 1 : 0;

    if ($is_bugmail
        || $is_passwordmail
        || $is_test_email
        || $is_whine_email
        || $encrypt_header
    ) {
        # Convert the email's To address into a User object
        my $login = $email->header('To');
        my $emailsuffix = Bugzilla->params->{'emailsuffix'};
        $login =~ s/$emailsuffix$//;
        my $user = new Bugzilla::User({ name => $login });

        # Default to secure. (Of course, this means if this extension has a
        # bug, lots of people are going to get bugmail falsely claiming their
        # bugs are secure and they need to add a key...)
        my $make_secure = SECURE_ALL;

        if ($is_bugmail) {
            # This is also a bit of a hack, but there's no header with the
            # bug ID in. So we take the first number in the subject.
            my ($bug_id) = ($email->header('Subject') =~ /\[\D+(\d+)\]/);
            my $bug = new Bugzilla::Bug($bug_id);
            if (!_should_secure_bug($bug)) {
                $make_secure = SECURE_NONE;
            }
            # If the insider group has securemail enabled..
            my $insider_group = Bugzilla::Group->new({ name => Bugzilla->params->{'insidergroup'} });
            if ($insider_group
                && $insider_group->secure_mail
                && $make_secure == SECURE_NONE)
            {
                my $comment_is_private = Bugzilla->dbh->selectcol_arrayref(
                    "SELECT isprivate FROM longdescs WHERE bug_id=? ORDER BY bug_when",
                    undef, $bug_id);
                # Encrypt if there are private comments on an otherwise public bug
                if (scalar $email->parts > 1) {
                    $email->walk_parts(sub {
                        my $part = shift;
                        my $content_type = $part->content_type;
                        $body = $part->body if $content_type && $content_type =~ /^text\/plain/;
                    });
                }
                while ($body =~ /[\r\n]--- Comment #(\d+)/g) {
                    my $comment_number = $1;
                    if ($comment_number && $comment_is_private->[$comment_number]) {
                        $make_secure = SECURE_BODY;
                        last;
                    }
                }
                # Encrypt if updating a private attachment without a comment
                if ($email->header('X-Bugzilla-Changed-Fields')
                    && $email->header('X-Bugzilla-Attach-ID'))
                {
                    my $attachment = Bugzilla::Attachment->new($email->header('X-Bugzilla-Attach-ID'));
                    if ($attachment && $attachment->isprivate) {
                        $make_secure = SECURE_BODY;
                    }
                }
            }
        }
        elsif ($is_passwordmail) {
            # Mail is made unsecure only if the user does not have a public
            # key and is not in any security groups. So specifying a public
            # key OR being in a security group means the mail is kept secure
            # (but, as noted above, the check is the other way around because
            # we default to secure).
            if ($user &&
                !$user->public_key &&
                !grep($_->secure_mail, @{ $user->groups }))
            {
                $make_secure = SECURE_NONE;
            }
        }
        elsif ($is_whine_email) {
            # When a whine email has one or more secure bugs in the body, then
            # encrypt the entire email body. Subject can be left alone as it
            # comes from the whine settings.
            $make_secure = _should_secure_whine($email) ? SECURE_BODY : SECURE_NONE;
        }
        elsif ($encrypt_header) {
            # Templates or code may set the X-Bugzilla-Encrypt header to
            # trigger encryption of emails. Remove that header from the email.
            $email->header_set('X-Bugzilla-Encrypt');
        }

        # If finding the user fails for some reason, but we determine we
        # should be encrypting, we want to make the mail safe. An empty key
        # does that.
        my $public_key = $user ? $user->public_key : '';

        # Check if the new bugmail prefix should be added to the subject.
        my $add_new = ($email->header('X-Bugzilla-Type') eq 'new' &&
                       $user &&
                       $user->settings->{'bugmail_new_prefix'}->{'value'} eq 'on') ? 1 : 0;

        if ($make_secure == SECURE_NONE) {
            # Filter the bug_links in HTML email in case the bugs the links
            # point are "secured" bugs and the user may not be able to see
            # the summaries.
            _filter_bug_links($email);
        }
        else {
            _make_secure($email, $public_key, $is_bugmail && $make_secure == SECURE_ALL, $add_new);
        }
    }
}

# Custom hook for bugzilla.mozilla.org (see bug 752400)
sub bugmail_referenced_bugs {
    my ($self, $args) = @_;
    # Sanitise subjects of referenced bugs.
    my $referenced_bugs = $args->{'referenced_bugs'};
    # No need to sanitise subjects if the entire email will be secured.
    return if _should_secure_bug($args->{'updated_bug'});
    # Replace the subject if required
    foreach my $ref (@$referenced_bugs) {
        if (grep($_->secure_mail, @{ $ref->{'bug'}->groups_in })) {
            $ref->{'short_desc'} = "(Secure bug)";
        }
    }
}

sub _should_secure_bug {
    my ($bug) = @_;
    # If there's a problem with the bug, err on the side of caution and mark it
    # as secure.
    return
        !$bug
        || $bug->{'error'}
        || grep($_->secure_mail, @{ $bug->groups_in });
}

sub _should_secure_whine {
    my ($email) = @_;
    my $should_secure = 0;
    $email->walk_parts(sub {
        my $part = shift;
        my $content_type = $part->content_type;
        return if !$content_type || $content_type !~ /^text\/plain/;
        my $body = $part->body;
        my @bugids = $body =~ /Bug (\d+):/g;
        foreach my $id (@bugids) {
            $id = trim($id);
            next if !$id;
            my $bug = new Bugzilla::Bug($id);
            if ($bug && _should_secure_bug($bug)) {
                $should_secure = 1;
                last;
            }
        }
    });
    return $should_secure ? 1 : 0;
}

sub _make_secure {
    my ($email, $key, $sanitise_subject, $add_new) = @_;

    # Add header showing this email has been secured
    $email->header_set('X-Bugzilla-Secure-Email', 'Yes');

    my $subject = $email->header('Subject');
    my ($bug_id) = $subject =~ /\[\D+(\d+)\]/;

    my $key_type = 0;
    if ($key && $key =~ /PUBLIC KEY/) {
        $key_type = 'PGP';
    }
    elsif ($key && $key =~ /BEGIN CERTIFICATE/) {
        $key_type = 'S/MIME';
    }

    if ($key_type eq 'PGP') {
        ##################
        # PGP Encryption #
        ##################

        my $pubring = new Crypt::OpenPGP::KeyRing(Data => $key);
        my $pgp = new Crypt::OpenPGP(PubRing => $pubring);

        if (scalar $email->parts > 1) {
            my $old_boundary = $email->{ct}{attributes}{boundary};
            my $to_encrypt = "Content-Type: " . $email->content_type . "\n\n";

            # We need to do some fix up of each part for proper encoding and then
            # stringify all parts for encrypting. We have to retain the old
            # boundaries as well so that the email client can reconstruct the
            # original message properly.
            $email->walk_parts(\&_fix_encoding);

            $email->walk_parts(sub {
                my ($part) = @_;
                if ($sanitise_subject) {
                    _insert_subject($part, $subject);
                }
                return if $part->parts > 1; # Top-level
                $to_encrypt .= "--$old_boundary\n" . $part->as_string . "\n";
            });
            $to_encrypt .= "--$old_boundary--";

            # Now create the new properly formatted PGP parts containing the
            # encrypted original message
            my @new_parts = (
                Email::MIME->create(
                    attributes => {
                        content_type => 'application/pgp-encrypted',
                        encoding     => '7bit',
                    },
                    body => "Version: 1\n",
                ),
                Email::MIME->create(
                    attributes => {
                        content_type => 'application/octet-stream',
                        filename     => 'encrypted.asc',
                        disposition  => 'inline',
                        encoding     => '7bit',
                    },
                    body => _pgp_encrypt($pgp, $to_encrypt, $bug_id)
                ),
            );
            $email->parts_set(\@new_parts);
            my $new_boundary = $email->{ct}{attributes}{boundary};
            # Redo the old content type header with the new boundaries
            # and other information needed for PGP
            $email->header_set("Content-Type",
                               "multipart/encrypted; " .
                               "protocol=\"application/pgp-encrypted\"; " .
                               "boundary=\"$new_boundary\"");
        }
        else {
            _fix_encoding($email);
            if ($sanitise_subject) {
                _insert_subject($email, $subject);
            }
            $email->body_set(_pgp_encrypt($pgp, $email->body, $bug_id));
        }
    }

    elsif ($key_type eq 'S/MIME') {
        #####################
        # S/MIME Encryption #
        #####################

        $email->walk_parts(\&_fix_encoding);

        if ($sanitise_subject) {
            $email->walk_parts(sub { _insert_subject($_[0], $subject) });
        }

        my $smime = Crypt::SMIME->new();
        my $encrypted;

        eval {
            $smime->setPublicKey([$key]);
            $encrypted = $smime->encrypt($email->as_string());
        };

        if (!$@) {
            # We can't replace the Email::MIME object, so we have to swap
            # out its component parts.
            my $enc_obj = new Email::MIME($encrypted);
            $email->header_obj_set($enc_obj->header_obj());
            $email->parts_set([]);
            $email->body_set($enc_obj->body());
            $email->content_type_set('application/pkcs7-mime');
            $email->charset_set('UTF-8') if Bugzilla->params->{'utf8'};
        }
        else {
            $email->body_set('Error during Encryption: ' . $@);
        }
    }
    else {
        # No encryption key provided; send a generic, safe email.
        my $template = Bugzilla->template;
        my $message;
        my $email_type = $email->header('X-Bugzilla-Type');
        my $vars = {
          'urlbase'    => Bugzilla->localconfig->{urlbase},
          'bug_id'     => $bug_id,
          'maintainer' => Bugzilla->params->{'maintainer'},
          'email_type' => $email_type
        };

        $template->process('account/email/encryption-required.txt.tmpl',
                           $vars, \$message)
          || ThrowTemplateError($template->error());

        $email->parts_set([]);
        $email->content_type_set('text/plain');
        $email->body_set($message);
    }

    if ($sanitise_subject) {
        # This is designed to still work if the admin changes the word
        # 'bug' to something else. However, it could break if they change
        # the format of the subject line in another way.
        my $new = $add_new ? ' New:' : '';
        my $product = $email->header('X-Bugzilla-Product');
        my $component = $email->header('X-Bugzilla-Component');
        # Note: the $bug_id is required within the parentheses in order to keep
        # gmail's threading algorithm happy.
        $subject =~ s/($bug_id\])\s+(.*)$/$1$new (Secure bug $bug_id in $product :: $component)/;
        {
            # avoid excessive line wrapping done by Encode.
            local $Encode::Encoding{'MIME-Q'}->{'bpl'} = 998;
            $email->header_set('Subject', encode('MIME-Q', $subject));
        }
    }
}

sub _pgp_encrypt {
    my ($pgp, $text, $bug_id) = @_;
    # "@" matches every key in the public key ring, which is fine,
    # because there's only one key in our keyring.
    #
    # We use the CAST5 cipher because the Rijndael (AES) module doesn't
    # like us for some reason I don't have time to debug fully.
    # ("key must be an untainted string scalar")
    my $encrypted = $pgp->encrypt(
        Data       => $text,
        Recipients => "@",
        Cipher     => 'CAST5',
        Armour     => 0
    );
    if (!defined $encrypted) {
        return 'Error during Encryption: ' . $pgp->errstr;
    }
    $encrypted = Crypt::OpenPGP::Armour->armour(
        Data => $encrypted,
        Object => 'MESSAGE',
        Headers => {
            Comment => Bugzilla->localconfig->{urlbase} . ($bug_id ? 'show_bug.cgi?id=' . $bug_id : ''),
        },
    );
    # until Crypt::OpenPGP makes the Version header optional we have to strip
    # it out manually (bug 1181406).
    $encrypted =~ s/\nVersion:[^\n]+//;
    return $encrypted;
}

# Insert the subject into the part's body, as the subject of the message will
# be sanitised.
# XXX this incorrectly assumes all parts of the message are the body
# we should only alter parts whose parent is multipart/alternative
sub _insert_subject {
    my ($part, $subject) = @_;
    my $content_type = $part->content_type or return;
    if ($content_type =~ /^text\/plain/) {
        $part->body_str_set("Subject: $subject\015\012\015\012" . $part->body_str);
    }
    elsif ($content_type =~ /^text\/html/) {
        my $tree = HTML::Tree->new->parse_content($part->body_str);
        my $body = $tree->look_down(qw(_tag body));
        $body->unshift_content(['strong', "Subject: $subject"], ['br']);
        $part->body_str_set($tree->as_HTML);
        $tree->delete;
    }
}

sub _fix_encoding {
    my $part = shift;

    # don't touch the top-level part of multi-part mail
    return if $part->parts > 1;

    # nothing to do if the part already has a charset
    my $ct = parse_content_type($part->content_type);
    my $charset = $ct->{attributes}{charset}
        ? $ct->{attributes}{charset}
        : '';
    return unless !$charset || $charset eq 'us-ascii';

    if (Bugzilla->params->{utf8}) {
        $part->charset_set('UTF-8');
        my $raw = $part->body_raw;
        if (utf8::is_utf8($raw)) {
            utf8::encode($raw);
            $part->body_set($raw);
        }
    }
    $part->encoding_set('quoted-printable');
}

sub _filter_bug_links {
    my ($email) = @_;
    $email->walk_parts(sub {
        my $part = shift;
        _fix_encoding($part);
        my $content_type = $part->content_type;
        return if !$content_type || $content_type !~ /text\/html/;
        my $tree = HTML::Tree->new->parse_content($part->body_str);
        my @links = $tree->look_down( _tag  => q{a}, class => qr/bz_bug_link/ );
        my $updated = 0;
        foreach my $link (@links) {
            my $href = $link->attr('href');
            my ($bug_id) = $href =~ /\Qshow_bug.cgi?id=\E(\d+)/;
            my $bug = new Bugzilla::Bug($bug_id);
            if ($bug && _should_secure_bug($bug)) {
                $link->attr('title', '(secure bug)');
                $link->attr('class', 'bz_bug_link');
                $updated = 1;
            }
        }
        if ($updated) {
            $part->body_str_set($tree->as_HTML);
        }
        $tree->delete;
    });
}

__PACKAGE__->NAME;