https://github.com/afresh1/opensmtpd-filter
This is a barely functional perl module to make writing OpenSMTPd filters easier.
https://github.com/afresh1/opensmtpd-filter
email filter mail openbsd opensmtpd opensmtpd-filter
Last synced: 5 months ago
JSON representation
This is a barely functional perl module to make writing OpenSMTPd filters easier.
- Host: GitHub
- URL: https://github.com/afresh1/opensmtpd-filter
- Owner: afresh1
- License: other
- Created: 2021-02-10T03:26:06.000Z (about 4 years ago)
- Default Branch: blead
- Last Pushed: 2023-07-06T01:30:55.000Z (almost 2 years ago)
- Last Synced: 2024-11-13T14:14:39.291Z (6 months ago)
- Topics: email, filter, mail, openbsd, opensmtpd, opensmtpd-filter
- Language: Perl
- Homepage:
- Size: 104 KB
- Stars: 6
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# NAME
OpenSMTPd::Filter - Easier filters for OpenSMTPd in perl
# VERSION
version v0.0.3
# SYNOPSIS
use OpenSMTPD::Filter;
use OpenBSD::Pledge;
pledge();
my $filter = OpenSMTPd::Filter->new(
on => {
report => \%report_callbacks,
filter => \%filter_callbacks,
},
);
$filter->ready; # Registers and starts listening for updates
# DESCRIPTION
This module is a helper to make writing [OpenSMTPd](https://opensmtpd.org)
filters in perl easier.
It should support smtpd API protocol version 0.7 and earlier.
# METHODS
## new
my $filter = OpenSMTPd::Filter->new(
input => \*STDIN, # the default
output => \*STDOUT, # the default
debug => 0, # the default,
on => \%callbacks,
);
Instantiates a new filter ready to start handling events.
- on
my $filter = OpenSMTPd::Filter->new(
...,
on => {
report => { 'smtp-in' => {
'link-connect' => \&lookup_spf_async,
} },
filter => { 'smtp-in' => {
helo => \&check_spf,
ehlo => \&check_spf,
} },
},
);
A hashref of events to add callbacks for.
The top level is the `stream` to listen on,
either `report` or `filter`.
The next level is the `subsystem` which must be `smtp-in`.
Finally the `event` or `phase` to to handle.
See ["REPORT AND FILTER STREAMS"](#report-and-filter-streams) for details on writing callbacks.
- input
The filehandle used to receive messages from smtpd.
Will be changed to `binmode(":raw")`.
Defaults to `STDIN`.
- output
The filehandle used to send messages to smtpd.
Will be changed to `binmode(":raw")`.
Defaults to `STDOUT`.
- debug
Set to a true value to enable debugging.
Primarily this means copying all lines
from ["input"](#input) and ["output"](#output) to `STDERR`.
## ready
$filter->ready;
Processes events on ["input"](#input) until it hits `eof`,
which should only happen when smtpd exits.
# REPORT AND FILTER STREAMS
my $callback = sub {
my ( $phase_or_event, $session, @extra ) = @_;
...;
};
Each stream triggers events and each event callback adds to a session
state as well as a list of events that have been received in that
session.
Each callback is called with the report event or filter phase
that triggered the callback as the first argument and a session datastructure
as the second argument.
The subsystem can be found in `$session->{state}->{subsystem}`.
Some callbacks will get additional arguments as documented below.
The `$session` hashref may contain up to three keys:
$session = {
state => \%state,
events => \@events,
messages => \@messages,
};
Nothing in this session hash is used by this module other than in
each message, the `data-line` arrayref is passed to the ["data-lines"](#data-lines)
filter and the `sent-dot` boolean is used to know whether to
continue sending [filter-dataline](https://metacpan.org/pod/filter-dataline) responses.
This means your filters can munge the contents or add additional
entries although care must be taken not to change the expected type
of an entry, but adding additional keys or changing values will not
cause issues.
- state
This is the state filled in by the fields for each received event.
Any `tx` events go into ["messages"](#messages) instead of this state.
A state might loook like this, however it only contains the fields
recieved at each point in the connection and will contain any fields
set by a ["REPORT EVENT"](#report-event):
my $state = {
version => '0.6',
timestamp => '1613356167.075372',
subsystem => 'smtp-in',
event => 'timeout',
phase => 'commit',
session => '3647ceea74a815de',
rdns => 'localhost',
fcrdns => 'pass',
src => '[::1]:37403',
dest => '[::1]:25',
hostname => 'mail.example.test',
method => 'HELO',
identity => 'mail.afresh1.test',
command => '.',
response => '250 2.0.0 5e170a6f Message accepted for delivery',
message => $session->{messages}->[-1],
};
See the rest of this section for which events fill in each field.
- events
This is an arrayref of hashrefs of the fields for each recieved
message, each hashref contains all fields supplied by that report
event or filter phase.
In addition, the event includes a `request` field indicating
whether the event was a report or a filter.
my $event = {
request => 'report',
version => '0.5',
timestamp => '1576146008.006099',
subsystem => 'smtp-in',
event => 'link-connect',
session => '7641df9771b4ed00',
rdns => 'mail.openbsd.org',
fcrdns => 'pass',
src => '199.185.178.25:33174',
dest => '45.77.67.80:25',
};
- messages
Message states collect the fields provided by each `tx-*`
["REPORT EVENT"](#report-event) for each `message-id` in a session.
my $message' = {
'message-id' => '48f59d87',
'envelope-id' => '48f59d87264c2287',
'mail-from', => 'andrew',
'rcpt-to', => ['afresh1'],
'data-line' => [
'Received: from mail (localhost [::1])',
' by mail.example.test (OpenSMTPD) with SMTP id 48f59d87',
' for ;',
' Sat, 27 Feb 2021 20:56:38 -0800 (PST)',
'From: andrew',
'To: afresh1',
'Subject: Hai!',
'',
'Hello There',
'.'
],
'result' => 'ok',
'sent-dot' => 1,
};
The ["tx-from"](#tx-from) and ["tx-rcpt"](#tx-rcpt) events are handled specially and
go into the `mail-from`, `rcpt-to`, and `result` fields.
The `rcpt-to` ends up in an arrayref as the message can be destined
for multiple recipients.
If a ["data-lines"](#data-lines) filter exists,
the `data-line` field is also an arrayref of each line that has been
recieved so far, with the `CR` and `LF` removed.
The `sent-dot` field is a boolen indicating whether this message
has sent the `.` indicating it is complete.
## REPORT EVENT
my $callback = sub {
my ( $event, $session ) = @_;
...;
return 'anything'; # ignored
};
All report events will provide these fields:
- version
- timestamp
- subsystem
- event
- session
- suffix
Events for the subsystem below may include additional fields.
- smtp-in
- link-connect
- rdns
- fcrdns
- src
- dest
- link-greeting
- hostname
- link-identify
- method
- identity
- link-tls
- tls-string
- link-disconnect
- link-auth
- result
- username
- protocol-client
- command
- protocol-server
- response
- filter-report
- filter-kind
- name
- message
- filter-response
- phase
- response
- param
- timeout
## MESSAGE REPORT EVENTS
my $callback = sub {
my ($event, $session) = @_
my $message = $session->{state}->{message};
...;
};
All filters that begin with `tx-` include a `message-id` field
and possibly other fields.
These events add to the last item in ["messages"](#messages),
which is also added as the `message` field in the `session` ["state"](#state).
- message-id
Message events for the `smtp-in` subsystem may include additional fields.
- tx-reset
- tx-begin
- tx-mail
- result
- mail-from
The `address` field for a `tx-mail` event is recorded as the
`mail-from` in the message.
- tx-rcpt
- result
- rcpt-to
The `address` field for a `tx-rcpt` events are recorded in the
`rcpt-to` arrayref in the message.
- tx-envelope
- envelope-id
- tx-data
- result
- tx-commit
- message-size
- tx-rollback
## FILTER REQUEST
my $callback = sub {
my ( $phase, $session, @data_lines ) = @_;
...;
return $response, @params;
};
See ["FILTER RESPONSE"](#filter-response) for details about what can be returned.
The ["data-line"](#data-line) and ["data-lines"](#data-lines) callbacks are special in that
they also recieve the current `data-line` or all lines recieved.
They should also return a list of ["dataline"](#dataline) responses instead of the
normal decision response.
All filter events have these fields:
- version
- timestamp
- subsystem
- phase
- session
- opaque-token
Specific filter events for each subsystem may include additional
fields.
- smtp-in
- connect
- rdns
- fcrdns
- src
- dest
- helo
- identity
- ehlo
- identity
- starttls
- tls-string
- auth
- auth
- mail-from
- address
- rcpt-to
- address
- data
- commit
- data-line
The `data-line` and `data-lines` callbacks are special in that
they return a list of ["dataline"](#dataline) responses and not a normal
["FILTER RESPONSE"](#filter-response).
The returned lines are split on `\n` so you can return a single
string that is the entire message and it will be split into individual
["dataline"](#dataline) responses.
You can return any number of lines from an individual `data-line`
callback until you recieve the single `.` indicating the end of
the message.
When you recieve the single `.` as the `line` you will need to
finish processing the message and return any lines that are still
pending.
- line
- data-lines
This is a wrapper around the ["data-line"](#data-line) callback
to make it easier to process the entire message instead
of dealing with it on a line-by-line basis and having to
store it yourself.
See the ["BUGS AND LIMITATIONS"](#bugs-and-limitations),
although this seemed like a good idea,
to better support `pledge` it might go away
and leave implementing data-line storage to the filter author.
- lines
The final argument is an arrayref of all lines in the message.
### FILTER RESPONSE
The return value from a ["FILTER REQUEST"](#filter-request) callback determines what
will be done with the message.
- dataline
This is the special response used by ["data-line"](#data-line) filters.
There is special processing that if the returned line contains
newlines it will be split into multiple responses.
- line
- proceed
my $callback = sub {
...;
return 'proceed';
};
This is the normal response, it means the message will continue to
additional filters and if all filters return `proceed` the message
will be accepted.
- junk
my $callback = sub {
...;
return 'junk';
};
Like ["proceed"](#proceed) but will add an `X-Spam` header to the message.
- reject
my $callback = sub {
...;
return reject => "400 Not Sure";
};
You must provide a valid SMTP error message as the second argument
to the return value including the status code, 5xx or 4xx.
A 421 status will ["disconnect"](#disconnect) the client.
- error
- disconnect
my $callback = sub {
...;
return disconnect => "550 Go Away";
};
As with ["reject"](#reject) the return from this callback must include a
valid SMTP error message including the status code.
However, like a `421` ["reject"](#reject) status, all messages will
disconnect the client.
- error
- rewrite
my $callback = sub {
my ($phase, $session) = @_;
...;
if ( $phase eq 'tx-rcpt' ) {
my $event = $session->{events}->[-1];
return rewrite => 'afresh1'
if $event->{address} eq 'andrew';
}
return 'proceed';
};
- parameter
- report
Generates a ["filter-report"](#filter-report) event with the `parameter` as the
message that will be reported.
I'm not entirely sure where they get reported to,
I assume maybe any later filters.
I believe you would do something like this,
and that you could generate any supported event,
but I haven't had good luck with it.
my $s = $_[1]->{state};
printf $output "%s|"%010.06f"|%s|%s|%s|%s\n";
'report', Time::HiRes::time,
$s->{subsystem}, 'filter-response', $s->{session},
$parameter
);
This is not a result response.
- parameter
# BUGS AND LIMITATIONS
The received ["data-line"](#data-line) are stored in a list in memory
if a ["data-lines"](#data-lines) filter exists,
which could easily be very large if the message is sizable.
These should instead be stored in a temporary file.
There is currently no way to stop listening for specific report events,
this module should provide a way to specify which events it should
listen for and gather state from.
# DEPENDENCIES
Perl 5.16 or higher.
# SEE ALSO
[smtpd-filters(7)](https://github.com/openbsd/src/blob/master/usr.sbin/smtpd/smtpd-filters.7)
[OpenBSD::Pledge](http://man.openbsd.org/OpenBSD::Pledge)
[OpenBSD::Unveil](http://man.openbsd.org/OpenBSD::Unveil)
# AUTHOR
Andrew Hewus Fresh
# COPYRIGHT AND LICENSE
This software is Copyright (c) 2021 by Andrew Hewus Fresh .
This is free software, licensed under:
The MIT (X11) License