qpsmtpd/docs/hooks.pod

#
# This file is best read with ``perldoc plugins.pod''
#

### 
# Conventions:
#  plugin names:  F<myplugin>
#  constants:     I<LOGDEBUG>
#  smtp commands, answers: B<HELO>, B<250 Queued!>
#
# Notes: 
#  * due to restrictions of some POD parsers, no C<<$object->method()>>
#    are allowed, use C<$object-E<gt>method()> 
# 

=head1 SMTP hooks

This section covers the hooks, which are run in a normal SMTP connection. 
The order of these hooks is like you will (probably) see them, while a mail
is received. 

Every hook receives a C<Qpsmtpd::Plugin> object of the currently 
running plugin as the first argument. A C<Qpsmtpd::Transaction> object is 
the second argument of the current transaction in the most hooks, exceptions 
are noted in the description of the hook. If you need examples how the 
hook can be used, see the source of the plugins, which are given as 
example plugins.

B<NOTE>: for some hooks (post-fork, post-connection, disconnect, deny, ok) the
return values are ignored. This does B<not> mean you can return anything you
want. It just means the return value is discarded and you can not disconnect
a client with I<DENY_DISCONNECT>. The rule to return I<DECLINED> to run the
next plugin for this hook (or return I<OK> / I<DONE> to stop processing) 
still applies.

=head2 hook_pre_connection

Called by a controlling process (e.g. forkserver or prefork) after accepting 
the remote server, but before beginning a new instance (or handing the 
connection to the worker process).

Useful for load-management and rereading large config files at some
frequency less than once per session.

This hook is available in F<qpsmtpd-forkserver> and F<qpsmtpd-prefork> flavors.

=cut 

NOT FOR: apache, -server and inetd/pperl

=pod

B<NOTE:> You should not use this hook to do major work and / or use lookup 
methods which (I<may>) take some time, like DNS lookups. This will slow down
B<all> incoming connections, no other connection will be accepted while this
hook is running!

Arguments this hook receives are:

  my ($self,$transaction,%args) = @_;
  # %args is:
  # %args = ( remote_ip    => inet_ntoa($iaddr),
  #           remote_port  => $port,
  #           local_ip     => inet_ntoa($laddr),
  #           local_port   => $lport,
  #           max_conn_ip  => $MAXCONNIP,
  #           child_addrs  => [values %childstatus],
  #         );

B<NOTE:> the C<$transaction> is of course C<undef> at this time.

Allowed return codes are

=over 4

=item DENY / DENY_DISCONNECT

returns a B<550> to the client and ends the connection

=item DENYSOFT / DENYSOFT_DISCONNECT

returns a B<451> to the client and ends the connection

=back

Anything else is ignored.

Example plugins are F<hosts_allow> and F<connection_time>. 

=head2 hook_connect

It is called at the start of a connection before the greeting is sent to 
the connecting client.

Arguments for this hook are

  my $self = shift;

B<NOTE:> in fact you get passed two more arguments, which are C<undef> at this
early stage of the connection, so ignore them.

Allowed return codes are

=over 4

=item OK

Stop processing plugins, give the default response

=item DECLINED

Process the next plugin

=item DONE

Stop processing plugins and dont give the default response, i.e. the plugin 
gave the response

=item DENY

Return hard failure code and disconnect

=item DENYSOFT

Return soft failure code and disconnect

=back

Example plugin for this hook is the F<check_relay> plugin. 

=head2 hook_helo / hook_ehlo

It is called after the client sent B<EHLO> (hook_ehlo) or B<HELO> (hook_helo)
Allowed return codes are

=over 4

=item DENY

Return a 550 code

=item DENYSOFT

Return a B<450> code

=item DENY_DISCONNECT / DENYSOFT_DISCONNECT

as above but with disconnect

=item DONE

Qpsmtpd wont do anything, the plugin sent the message

=item DECLINED 

Qpsmtpd will send the standard B<EHLO>/B<HELO> answer, of course only 
if all plugins hooking I<helo/ehlo> return I<DECLINED>.

=back

Arguments of this hook are

  my ($self, $transaction, $host) = @_;
  # $host: the name the client sent in the 
  # (EH|HE)LO line

B<NOTE:> C<$transaction> is C<undef> at this point.

=head2 hook_mail_pre

After the B<MAIL FROM: > line sent by the client is broken into 
pieces by the C<hook_mail_parse()>, this hook recieves the results.
This hook may be used to pre-accept adresses without the surrounding 
I<E<lt>E<gt>> (by adding them) or addresses like 
I<E<lt>user@example.com.E<gt>> or I<E<lt>user@example.com E<gt>> by 
removing the trailing I<"."> / C<" ">.

Expected return values are I<OK> and an address which must be parseable
by C<Qpsmtpd::Address-E<gt>parse()> on success or any other constant to
indicate failure.

Arguments are 

  my ($self, $transaction, $addr) = @_;

=head2 hook_mail

Called right after the envelope sender line is parsed (the B<MAIL FROM: >
command). The plugin gets passed a C<Qpsmtpd::Address> object, which means 
the parsing and verifying the syntax of the address (and just the syntax, 
no other checks) is already done. Default is to allow the sender address. 
The remaining arguments are the extensions defined in RFC 1869 (if sent by 
the client).

B<NOTE:> According to the SMTP protocol, you can not reject an invalid
sender until after the B<RCPT> stage (except for protocol errors, i.e.
syntax errors in address). So store it in an C<$transaction-E<gt>note()> and 
process it later in an rcpt hook.

Allowed return codes are

=over 4

=item OK

sender allowed

=item DENY

Return a hard failure code

=item DENYSOFT

Return a soft failure code

=item DENY_DISCONNECT / DENYSOFT_DISCONNECT

as above but with disconnect

=item DECLINED

next plugin (if any)

=item DONE

skip further processing, plugin sent response

=back

Arguments for this hook are 

  my ($self,$transaction, $sender, %args) = @_;
  # $sender: an Qpsmtpd::Address object for 
  # sender of the message

Example plugins for the C<hook_mail> are F<resolvable_fromhost>
and F<badmailfrom>.

=head2 hook_rcpt_pre

See C<hook_mail_pre>, s/MAIL FROM:/RCPT TO:/.

=head2 hook_rcpt

This hook is called after the client sent an I<RCPT TO: > command (after 
parsing the line). The given argument is parsed by C<Qpsmtpd::Address>, 
then this hook is called. Default is to deny the mail with a soft error 
code. The remaining arguments are the extensions defined in RFC 1869
(if sent by the client).

Allowed return codes

=over 4

=item OK

recipient allowed

=item DENY

Return a hard failure code, for example for an I<User does not exist here> 
message.

=item DENYSOFT

Return a soft failure code, for example if the connect to a user lookup 
database failed

=item DENY_DISCONNECT / DENYSOFT_DISCONNECT

as above but with disconnect

=item DONE

skip further processing, plugin sent response

=back

Arguments are

  my ($self, $transaction, $recipient, %args) = @_;
  # $rcpt = Qpsmtpd::Address object with 
  # the given recipient address

Example plugin is F<rcpt_ok>.

=head2 hook_data

After the client sent the B<DATA> command, before any data of the message
was sent, this hook is called. 

B<NOTE:> This hook, like B<EHLO>, B<VRFY>, B<QUIT>, B<NOOP>, is an 
endpoint of a pipelined command group (see RFC 1854) and may be used to 
detect ``early talkers''. Since svn revision 758 the F<earlytalker>
plugin may be configured to check at this hook for ``early talkers''.

Allowed return codes are

=over 4

=item DENY

Return a hard failure code

=item DENYSOFT

Return a soft failure code

=item DENY_DISCONNECT / DENYSOFT_DISCONNECT

as above but with disconnect

=item DONE

Plugin took care of receiving data and calling the queue (not recommended)

B<NOTE:> The only real use for I<DONE> is implementing other ways of
receiving the message, than the default... for example the CHUNKING SMTP
extension (RFC 1869, 1830/3030) ... a plugin for this exists at 
http://svn.perl.org/qpsmtpd/contrib/vetinari/experimental/chunking, but it
was never tested ``in the wild''.

=back

Arguments:

  my ($self, $transaction) = @_;

Example plugin is F<greylisting>.

=head2 hook_received_line

If you wish to provide your own Received header line, do it here. You can use
or discard any of the given arguments (see below).

Allowed return codes:

=over 4

=item OK, $string

use this string for the Received header.

=item anything else

use the default Received header

=back

Arguments are

 my ($self, $transaction, $smtp, $auth, $sslinfo) = @_;
 # $smtp - the SMTP type used (e.g. "SMTP" or "ESMTP").
 # $auth - the Auth header additionals.
 # $sslinfo - information about SSL for the header.

=head2 data_headers_end

This hook fires after all header lines of the message data has been received.
Defaults to doing nothing, just continue processing. At this step,
the sender is not waiting for a reply, but we can try and prevent him from
sending the entire message by disconnecting immediately. (Although it is
likely the packets are already in flight due to buffering and pipelining).

B<NOTE:> BE CAREFUL! If you drop the connection legal MTAs will retry again 
and again, spammers will probably not. This is not RFC compliant and can lead
to an unpredictable mess. Use with caution.

Why this hook may be useful for you, see 
L<http://www.nntp.perl.org/group/perl.qpsmtpd/2009/02/msg8502.html>, ff.

Allowed return codes:

=over 4

=item DENY_DISCONNECT

Return B<554 Message denied> and disconnect

=item DENYSOFT_DISCONNECT

Return B<421 Message denied temporarily> and disconnect

=item DECLINED

Do nothing

=back

Arguments:

  my ($self, $transaction) = @_; 

B<FIXME:> check arguments

=head2 hook_data_post

The C<data_post> hook is called after the client sent the final C<.\r\n> 
of a message, before the mail is sent to the queue.

Allowed return codes are

=over 4

=item DENY

Return a hard failure code

=item DENYSOFT

Return a soft failure code

=item DENY_DISCONNECT / DENYSOFT_DISCONNECT

as above but with disconnect

=item DONE

skip further processing (message will not be queued), plugin gave the response.

B<NOTE:> just returning I<OK> from a special queue plugin does (nearly) 
the same (i.e. dropping the mail to F</dev/null>) and you don't have to 
send the response on your own.

If you want the mail to be queued, you have to queue it manually!

=back

Arguments:

  my ($self, $transaction) = @_;

Example plugins: F<spamassassin>, F<virus/clamdscan>

=head2 hook_queue_pre

This hook is run, just before the mail is queued to the ``backend''. You 
may modify the in-process transaction object (e.g. adding headers) or add 
something like a footer to the mail (the latter is not recommended).

Allowed return codes are 

=over 4

=item DONE

no queuing is done

=item OK / DECLINED

queue the mail

=back

=head2 hook_queue

When all C<data_post> hooks accepted the message, this hook is called. It 
is used to queue the message to the ``backend''.

Allowed return codes:

=over 4

=item DONE

skip further processing (plugin gave response code)

=item OK

Return success message, i.e. tell the client the message was queued (this
may be used to drop the message silently).

=item DENY

Return hard failure code

=item DENYSOFT

Return soft failure code, i.e. if disk full or other temporary queuing 
problems

=back

Arguments:

  my ($self, $transaction) = @_;

Example plugins: all F<queue/*> plugins

=head2 hook_queue_post

This hook is called always after C<hook_queue>. If the return code is 
B<not> I<OK>, a message (all remaining return values) with level I<LOGERROR> 
is written to the log.
Arguments are

 my $self = shift;

B<NOTE:> C<$transaction> is not valid at this point, therefore not mentioned.


=head2 hook_reset_transaction

This hook will be called several times. At the beginning of a transaction 
(i.e. when the client sends a B<MAIL FROM:> command the first time), 
after queueing the mail and every time a client sends a B<RSET> command.
Arguments are 

 my ($self, $transaction) = @_;

B<NOTE:> don't rely on C<$transaction> being valid at this point.

=head2 hook_quit

After the client sent a B<QUIT> command, this hook is called (before the
C<hook_disconnect>).

Allowed return codes

=over 4

=item DONE

plugin sent response

=item DECLINED

next plugin and / or qpsmtpd sends response

=back

Arguments: the only argument is C<$self>

=cut 

### XXX: FIXME pass the rest of the line to this hook?

=pod

Expample plugin is the F<quit_fortune> plugin.

=head2 hook_disconnect

This hook will be called from several places: After a plugin returned 
I<DENY(|SOFT)_DISCONNECT>, before connection is disconnected or after the 
client sent the B<QUIT> command, AFTER the quit hook and ONLY if no plugin 
hooking C<hook_quit> returned I<DONE>.

All return values are ignored, arguments are just C<$self>

Example plugin is F<logging/file>

=head2 hook_post_connection

This is the counter part of the C<pre-connection> hook, it is called 
directly before the connection is finished, for example, just before the 
qpsmtpd-forkserver instance exits or if the client drops the connection 
without notice (without a B<QUIT>). This hook is not called if the qpsmtpd
instance is killed.

=cut 

FIXME: we should run this hook on a ``SIGHUP'' or some other signal?

=pod 

The only argument is C<$self> and all return codes are ignored, it would 
be too late anyway :-).

Example: F<connection_time>

=head1 Parsing Hooks

Before the line from the client is parsed by 
C<Qpsmtpd::Command-E<gt>parse()> with the built in parser, these hooks 
are called. They can be used to supply a parsing function for the line,
which will be used instead of the built in parser.

The hook must return two arguments, the first is (currently) ignored,
the second argument must be a (CODE) reference to a sub routine. This sub 
routine receives three arguments:

=over 4

=item $self

the plugin object

=item $cmd

the command (i.e. the first word of the line) sent by the client

=item $line

the line sent by the client without the first word

=back

Expected return values from this sub are I<DENY> and a reason which is 
sent to the client or I<OK> and the C<$line> broken into pieces according
to the syntax rules for the command.

B<NOTE: ignore the example from C<Qpsmtpd::Command>, the C<unrecognized_command_parse> hook was never implemented,...>

=head2 hook_helo_parse / hook_ehlo_parse

The provided sub routine must return two or more values. The first is 
discarded, the second is the hostname (sent by the client as argument 
to the B<HELO> / B<EHLO> command). All other values are passed to the 
helo / ehlo hook. This hook may be used to change the hostname the client
sent... not recommended, but if your local policy says only to accept
I<HELO> hosts with FQDNs and you have a legal client which can not be 
changed to send his FQDN, this is the right place.

=head2 hook_mail_parse / hook_rcpt_parse

The provided sub routine must return two or more values. The first is 
either I<OK> to indicate that parsing of the line was successfull
or anything else to bail out with I<501 Syntax error in command>. In
case of failure the second argument is used as the error message for the 
client.

If parsing was successfull, the second argument is the sender's / 
recipient's address (this may be without the surrounding I<E<lt>> and 
I<E<gt>>, don't add them here, use the C<hook_mail_pre()> / 
C<hook_rcpt_pre()> methods for this). All other arguments are 
sent to the C<mail / rcpt> hook as B<MAIL> / B<RCPT> parameters (see 
RFC 1869 I<SMTP Service Extensions> for more info). Note that 
the mail and rcpt hooks expect a list of key/value pairs as the 
last arguments.

=head2 hook_auth_parse

B<FIXME...>

=head1 Special hooks

Now some special hooks follow. Some of these hooks are some internal hooks, 
which may be used to alter the logging or retrieving config values from 
other sources (other than flat files) like SQL databases.

=head2 hook_logging

This hook is called when a log message is written, for example in a plugin 
it fires if someone calls C<$self-E<gt>log($level, $msg);>. Allowed
return codes are

=over 4

=item DECLINED

next logging plugin

=item OK

(not I<DONE>, as some might expect!) ok, plugin logged the message

=back

Arguments are

  my ($self, $transaction, $trace, $hook, $plugin, @log) = @_;
  # $trace: level of message, for example 
  #          LOGWARN, LOGDEBUG, ...
  # $hook:  the hook in/for which this logging 
  #          was called
  # $plugin: the plugin calling this hook
  # @log:   the log message

B<NOTE:> C<$transaction> may be C<undef>, depending when / where this hook
is called. It's probably best not to try acessing it.

All F<logging/*> plugins can be used as example plugins.

=head2 hook_deny

This hook is called after a plugin returned I<DENY>, I<DENYSOFT>, 
I<DENY_DISCONNECT> or I<DENYSOFT_DISCONNECT>. All return codes are ignored, 
arguments are

  my ($self, $transaction, $prev_plugin, $return, $return_text) = @_;

B<NOTE:> C<$transaction> may be C<undef>, depending when / where this hook
is called. It's probably best not to try acessing it.

Example plugin for this hook is F<logging/adaptive>.

=head2 hook_ok

The counter part of C<hook_deny>, it is called after a plugin B<did not>
return I<DENY>, I<DENYSOFT>, I<DENY_DISCONNECT> or I<DENYSOFT_DISCONNECT>. 
All return codes are ignored, arguments are

  my ( $self, $transaction, $prev_plugin, $return, $return_text ) = @_;

B<NOTE:> C<$transaction> may be C<undef>, depending when / where this hook
is called. It's probably best not to try acessing it.

=head2 hook_config

Called when a config file is requested, for example in a plugin it fires 
if someone calls C<my @cfg = $self-E<gt>qp-E<gt>config($cfg_name);>. 
Allowed return codes are

=over 4

=item DECLINED

plugin didn't find the requested value

=item OK, @values

requested values as C<@list>, example:

  return (OK, @{$config{$key}})
    if exists $config{$key};
  return (DECLINED);

=back

Arguments:

  my ($self,$transaction,@keys) = @_;
  # @keys: the requested config item(s)

B<NOTE:> C<$transaction> may be C<undef>, depending when / where this hook
is called. It's probably best not to try acessing it.

Example plugin is F<http_config> from the qpsmtpd distribution.

=head2 hook_user_config

Called when a per-user configuration directive is requested, for example
if someone calls C<my @cfg = $rcpt-E<gt>config($cfg_name);>. 
Allowed return codes are

=over 4

=item DECLINED

plugin didn't find the requested value

=item OK, @values

requested values as C<@list>, example:

  return (OK, @{$config{$key}})
    if exists $config{$key};
  return (DECLINED);

=back

Arguments:

  my ($self,$transaction,$user,@keys) = @_;
  # @keys: the requested config item(s)

Example plugin is F<user_config> from the qpsmtpd distribution.

=head2 hook_unrecognized_command

This is called if the client sent a command unknown to the core of qpsmtpd.
This can be used to implement new SMTP commands or just count the number 
of unknown commands from the client, see below for examples.
Allowed return codes:

=over 4

=item DENY_DISCONNECT

Return B<521> and disconnect the client

=item DENY

Return B<500>

=item DONE

Qpsmtpd wont do anything; the plugin responded, this is what you want to 
return, if you are implementing new commands

=item Anything else...

Return B<500 Unrecognized command>

=back

Arguments:

  my ($self, $transaction, $cmd, @args) = @_;
  # $cmd  = the first "word" of the line 
  #         sent by the client
  # @args = all the other "words" of the 
  #         line sent by the client
  #         "word(s)": white space split() line

B<NOTE:> C<$transaction> may be C<undef>, depending when / where this hook
is called. It's probably best not to try acessing it.

Example plugin is F<tls>.

=head2 hook_help

This hook triggers if a client sends the B<HELP> command, allowed return
codes are:

=over 4

=item DONE

Plugin gave the answer.

=item DENY

The client will get a C<syntax error> message, probably not what you want, 
better use

  $self->qp->respond(502, "Not implemented.");
  return DONE;

=back

Anything else will be send as help answer.

Arguments are
   my ($self, $transaction, @args) = @_;

with C<@args> being the arguments from the client's command.

=head2 hook_vrfy

If the client sents the B<VRFY> command, this hook is called. Default is to 
return a message telling the user to just try sending the message.
Allowed return codes:

=over 4

=item OK

Recipient Exists

=item DENY

Return a hard failure code

=item DONE

Return nothing and move on

=item Anything Else...

Return a B<252>

=back

Arguments are:

 my ($self) = shift;

=cut 

FIXME: this sould be changed in Qpsmtpd::SMTP to pass the rest of the line
as arguments to the hook

=pod

=head2 hook_noop 

If the client sents the B<NOOP> command, this hook is called. Default is to
return C<250 OK>.

Allowed return codes are:

=over 4

=item DONE

Plugin gave the answer

=item DENY_DISCONNECT

Return error code and disconnect client

=item DENY

Return error code.

=item Anything Else...

Give the default answer of B<250 OK>.

=back

Arguments are

  my ($self,$transaction,@args) = @_;

=head1 Authentication hooks

=cut 

B<FIXME missing:> auth_parse

#=head2 auth

B<FIXME>

#=head2 auth-plain

B<FIXME>

#=head2 auth-login

B<FIXME>

#=head2 auth-cram-md5

B<FIXME>

=pod

See F<docs/authentication.pod>.

=cut

# vim: ts=2 sw=2 expandtab