# 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 `Qpsmtpd::Plugin` object of the currently running plugin as the first argument. A `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. __NOTE__: for some hooks (post-fork, post-connection, disconnect, deny, ok) the return values are ignored. This does __not__ mean you can return anything you want. It just means the return value is discarded and you can not disconnect a client with `DENY_DISCONNECT`. The rule to return `DECLINED` to run the next plugin for this hook (or return `OK` / `DONE` to stop processing) still applies. ## 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 `qpsmtpd-forkserver` and `qpsmtpd-prefork` flavors. __NOTE:__ You should not use this hook to do major work and / or use lookup methods which (_may_) take some time, like DNS lookups. This will slow down __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 => $MAXCONNIP, # child_addrs => [values %childstatus], # ); __NOTE:__ the `$transaction` is of course `undef` at this time. Allowed return codes are - DENY / DENY\_DISCONNECT returns a __550__ to the client and ends the connection - DENYSOFT / DENYSOFT\_DISCONNECT returns a __451__ to the client and ends the connection Anything else is ignored. Example plugins are `hosts_allow` and `connection_time`. ## 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 $self = shift; __NOTE:__ in fact you get passed two more arguments, which are `undef` at this early stage of the connection, so ignore them. Allowed return codes are - OK Stop processing plugins, give the default response - DECLINED Process the next plugin - DONE Stop processing plugins and dont give the default response, i.e. the plugin gave the response - DENY Return hard failure code and disconnect - DENYSOFT Return soft failure code and disconnect Example plugin for this hook is the `check_relay` plugin. ## hook\_helo / hook\_ehlo It is called after the client sent __EHLO__ (hook\_ehlo) or __HELO__ (hook\_helo) Allowed return codes are - DENY Return a 550 code - DENYSOFT Return a __450__ code - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect - DONE Qpsmtpd wont do anything, the plugin sent the message - DECLINED Qpsmtpd will send the standard __EHLO__/__HELO__ answer, of course only if all plugins hooking _helo/ehlo_ return _DECLINED_. Arguments of this hook are my ($self, $transaction, $host) = @_; # $host: the name the client sent in the # (EH|HE)LO line __NOTE:__ `$transaction` is `undef` at this point. ## hook\_mail\_pre After the `MAIL FROM:` line sent by the client is broken into pieces by the `hook_mail_parse()`, this hook recieves the results. This hook may be used to pre-accept adresses without the surrounding `<>` (by adding them) or addresses like `` or `` by removing the trailing "." / " ". Expected return values are `OK` and an address which must be parseable by `Qpsmtpd::Address->parse()` on success or any other constant to indicate failure. Arguments are my ($self, $transaction, $addr) = @_; ## hook\_mail Called right after the envelope sender line is parsed (the `MAIL FROM:` command). The plugin gets passed a `Qpsmtpd::Address` object, which means the parsing and verifying the syntax of the address (and just the syntax, no other checks) is already done. Default is to allow the sender address. The remaining arguments are the extensions defined in RFC 1869 (if sent by the client). __NOTE:__ According to the SMTP protocol, you can not reject an invalid sender until after the __RCPT__ stage (except for protocol errors, i.e. syntax errors in address). So store it in an `$transaction->note()` and process it later in an rcpt hook. Allowed return codes are - OK sender allowed - DENY Return a hard failure code - DENYSOFT Return a soft failure code - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect - DECLINED next plugin (if any) - DONE skip further processing, plugin sent response Arguments for this hook are my ($self,$transaction, $sender, %args) = @_; # $sender: an Qpsmtpd::Address object for # sender of the message Example plugins for the `hook_mail` are `resolvable_fromhost` and `badmailfrom`. ## hook\_rcpt\_pre See `hook_mail_pre`, s/MAIL FROM:/RCPT TO:/. ## hook\_rcpt This hook is called after the client sent an `RCPT TO:` command (after parsing the line). The given argument is parsed by *Qpsmtpd::Address*, then this hook is called. Default is to deny the mail with a soft error code. The remaining arguments are the extensions defined in RFC 1869 (if sent by the client). Allowed return codes - OK recipient allowed - DENY Return a hard failure code, for example for an _User does not exist here_ message. - DENYSOFT Return a soft failure code, for example if the connect to a user lookup database failed - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect - DONE skip further processing, plugin sent response Arguments are my ($self, $transaction, $recipient, %args) = @_; # $rcpt = Qpsmtpd::Address object with # the given recipient address Example plugin is `rcpt_ok`. ## hook\_data After the client sent the __DATA__ command, before any data of the message was sent, this hook is called. __NOTE:__ This hook, like __EHLO__, __VRFY__, __QUIT__, __NOOP__, is an endpoint of a pipelined command group (see RFC 1854) and may be used to detect \`\`early talkers''. Since svn revision 758 the `earlytalker` plugin may be configured to check at this hook for \`\`early talkers''. Allowed return codes are - DENY Return a hard failure code - DENYSOFT Return a soft failure code - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect - DONE Plugin took care of receiving data and calling the queue (not recommended) __NOTE:__ The only real use for _DONE_ is implementing other ways of receiving the message, than the default... for example the CHUNKING SMTP extension (RFC 1869, 1830/3030) ... a plugin for this exists at http://svn.perl.org/qpsmtpd/contrib/vetinari/experimental/chunking, but it was never tested \`\`in the wild''. Arguments: my ($self, $transaction) = @_; Example plugin is `greylisting`. ## 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: - OK, $string use this string for the Received header. - anything else use the default Received header Arguments are my ($self, $transaction, $smtp, $auth, $sslinfo) = @_; # $smtp - the SMTP type used (e.g. "SMTP" or "ESMTP"). # $auth - the Auth header additionals. # $sslinfo - information about SSL for the header. ## data\_headers\_end This hook fires after all header lines of the message data has been received. Defaults to doing nothing, just continue processing. At this step, the sender is not waiting for a reply, but we can try and prevent him from sending the entire message by disconnecting immediately. (Although it is likely the packets are already in flight due to buffering and pipelining). __NOTE:__ BE CAREFUL! If you drop the connection legal MTAs will retry again and again, spammers will probably not. This is not RFC compliant and can lead to an unpredictable mess. Use with caution. Why this hook may be useful for you, see [http://www.nntp.perl.org/group/perl.qpsmtpd/2009/02/msg8502.html](http://www.nntp.perl.org/group/perl.qpsmtpd/2009/02/msg8502.html), ff. Allowed return codes: - DENY\_DISCONNECT Return __554 Message denied__ and disconnect - DENYSOFT\_DISCONNECT Return __421 Message denied temporarily__ and disconnect - DECLINED Do nothing Arguments: my ($self, $transaction) = @_; __FIXME:__ check arguments ## hook\_data\_post\_headers The `data_post_headers` hook is called after the client sends the final .\r\n of a message and before the message is processed by `data_post`. This hook is primarily used by plugins that insert new headers (ex: Received-SPF) and/or modify headers such as appending to Authentication-Results (SPF, DKIM, DMARC). When it is desirable to have these header modifications evaluated by filtering software (spamassassin, dspam, etc.) running on `data_post`, this hook should be used instead of `data_post`. Allowed return codes are - DENY Return a hard failure code - DENYSOFT Return a soft failure code - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect ## hook\_data\_post The `data_post` hook is called after all headers has been added in `data_post_headers` above. This is meant for plugins that expect complete messages, such as content analyzing spam filters. Plugins can still add headers in this hook, however it is recommended only informational headers are added here. Allowed return codes are - DENY Return a hard failure code - DENYSOFT Return a soft failure code - DENY\_DISCONNECT / DENYSOFT\_DISCONNECT as above but with disconnect - DONE skip further processing (message will not be queued), plugin gave the response. __NOTE:__ just returning _OK_ from a special queue plugin does (nearly) the same (i.e. dropping the mail to `/dev/null`) and you don't have to send the response on your own. If you want the mail to be queued, you have to queue it manually! Arguments: my ($self, $transaction) = @_; Example plugins: `spamassassin`, `virus/clamdscan`, `dspam` ## hook\_queue\_pre This hook is run, just before the mail is queued to the \`\`backend''. You may modify the in-process transaction object (e.g. adding headers) or add something like a footer to the mail (the latter is not recommended). Allowed return codes are - DONE no queuing is done - OK / DECLINED queue the mail ## hook\_queue When all `data_post` hooks accepted the message, this hook is called. It is used to queue the message to the \`\`backend''. Allowed return codes: - DONE skip further processing (plugin gave response code) - OK Return success message, i.e. tell the client the message was queued (this may be used to drop the message silently). - DENY Return hard failure code - DENYSOFT Return soft failure code, i.e. if disk full or other temporary queuing problems Arguments: my ($self, $transaction) = @_; Example plugins: all `queue/*` plugins ## hook\_queue\_post This hook is called always after `hook_queue`. If the return code is __not__ _OK_, a message (all remaining return values) with level _LOGERROR_ is written to the log. Arguments are my $self = shift; __NOTE:__ `$transaction` is not valid at this point, therefore not mentioned. ## hook\_reset\_transaction This hook will be called several times. At the beginning of a transaction (i.e. when the client sends a __MAIL FROM:__ command the first time), after queueing the mail and every time a client sends a __RSET__ command. Arguments are my ($self, $transaction) = @_; __NOTE:__ don't rely on `$transaction` being valid at this point. ## hook\_quit After the client sent a __QUIT__ command, this hook is called (before the `hook_disconnect`). Allowed return codes - DONE plugin sent response - DECLINED next plugin and / or qpsmtpd sends response Arguments: the only argument is `$self` Expample plugin is the `quit_fortune` plugin. ## hook\_disconnect This hook will be called from several places: After a plugin returned `DENY(|SOFT)_DISCONNECT`, before connection is disconnected or after the client sent the `QUIT` command, AFTER the quit hook and ONLY if no plugin hooking `hook_quit` returned `DONE`. All return values are ignored, arguments are just `$self` Example plugin is `logging/file` ## hook\_post\_connection This is the counter part of the `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 __QUIT__). This hook is not called if the qpsmtpd instance is killed. The only argument is `$self` and all return codes are ignored, it would be too late anyway :-). Example: `connection_time` # Parsing Hooks Before the line from the client is parsed by `Qpsmtpd::Command->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: - $self the plugin object - $cmd the command (i.e. the first word of the line) sent by the client - $line the line sent by the client without the first word Expected return values from this sub are _DENY_ and a reason which is sent to the client or _OK_ and the `$line` broken into pieces according to the syntax rules for the command. __NOTE: ignore the example from `Qpsmtpd::Command`, the `unrecognized_command_parse` hook was never implemented,...__ ## `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 __HELO__ / __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 _HELO_ hosts with FQDNs and you have a legal client which can not be changed to send his FQDN, this is the right place. ## hook\_mail\_parse / hook\_rcpt\_parse The provided sub routine must return two or more values. The first is either _OK_ to indicate that parsing of the line was successfull or anything else to bail out with _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 _<_ and _>_, don't add them here, use the `hook_mail_pre()` / `hook_rcpt_pre()` methods for this). All other arguments are sent to the `mail / rcpt` hook as __MAIL__ / __RCPT__ parameters (see RFC 1869 _SMTP Service Extensions_ for more info). Note that the mail and rcpt hooks expect a list of key/value pairs as the last arguments. ## hook\_auth\_parse __FIXME...__ # 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. ## hook\_logging This hook is called when a log message is written, for example in a plugin it fires if someone calls `$self->log($level, $msg);`. Allowed return codes are - DECLINED next logging plugin - OK (not _DONE_, as some might expect!) ok, plugin logged the message Arguments are my ($self, $transaction, $trace, $hook, $plugin, @log) = @_; # $trace: level of message, for example # LOGWARN, LOGDEBUG, ... # $hook: the hook in/for which this logging # was called # $plugin: the plugin calling this hook # @log: the log message __NOTE:__ `$transaction` may be `undef`, depending when / where this hook is called. It's probably best not to try acessing it. All `logging/*` plugins can be used as example plugins. ## hook\_deny This hook is called after a plugin returned _DENY_, _DENYSOFT_, _DENY\_DISCONNECT_ or _DENYSOFT\_DISCONNECT_. All return codes are ignored, arguments are my ($self, $transaction, $prev_plugin, $return, $return_text) = @_; __NOTE:__ `$transaction` may be `undef`, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin for this hook is `logging/adaptive`. ## hook\_ok The counter part of `hook_deny`, it is called after a plugin __did not__ return _DENY_, _DENYSOFT_, _DENY\_DISCONNECT_ or _DENYSOFT\_DISCONNECT_. All return codes are ignored, arguments are my ( $self, $transaction, $prev_plugin, $return, $return_text ) = @_; __NOTE:__ `$transaction` may be `undef`, depending when / where this hook is called. It's probably best not to try acessing it. ## hook\_config Called when a config file is requested, for example in a plugin it fires if someone calls `my @cfg = $self->qp->config($cfg_name);`. Allowed return codes are - DECLINED plugin didn't find the requested value - OK, @values requested values as `@list`, example: return (OK, @{$config{$key}}) if exists $config{$key}; return (DECLINED); Arguments: my ($self,$transaction,@keys) = @_; # @keys: the requested config item(s) __NOTE:__ `$transaction` may be `undef`, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin is `http_config` from the qpsmtpd distribution. ## hook\_user\_config Called when a per-user configuration directive is requested, for example if someone calls `my @cfg = $rcpt->config($cfg_name);`. Allowed return codes are - DECLINED plugin didn't find the requested value - OK, @values requested values as `@list`, example: return (OK, @{$config{$key}}) if exists $config{$key}; return (DECLINED); Arguments: my ($self,$transaction,$user,@keys) = @_; # @keys: the requested config item(s) Example plugin is `user_config` from the qpsmtpd distribution. ## hook\_unrecognized\_command This is called if the client sent a command unknown to the core of qpsmtpd. This can be used to implement new SMTP commands or just count the number of unknown commands from the client, see below for examples. Allowed return codes: - DENY\_DISCONNECT Return __521__ and disconnect the client - DENY Return __500__ - DONE Qpsmtpd wont do anything; the plugin responded, this is what you want to return, if you are implementing new commands - Anything else... Return __500 Unrecognized command__ Arguments: my ($self, $transaction, $cmd, @args) = @_; # $cmd = the first "word" of the line # sent by the client # @args = all the other "words" of the # line sent by the client # "word(s)": white space split() line __NOTE:__ `$transaction` may be `undef`, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin is `tls`. ## hook\_help This hook triggers if a client sends the __HELP__ command, allowed return codes are: - DONE Plugin gave the answer. - DENY The client will get a `syntax error` message, probably not what you want, better use $self->qp->respond(502, "Not implemented."); return DONE; Anything else will be send as help answer. Arguments are my ($self, $transaction, @args) = @\_; with `@args` being the arguments from the client's command. ## hook\_vrfy If the client sents the __VRFY__ command, this hook is called. Default is to return a message telling the user to just try sending the message. Allowed return codes: - OK Recipient Exists - DENY Return a hard failure code - DONE Return nothing and move on - Anything Else... Return a __252__ Arguments are: my ($self) = shift; ## hook\_noop If the client sents the __NOOP__ command, this hook is called. Default is to return `250 OK`. Allowed return codes are: - DONE Plugin gave the answer - DENY\_DISCONNECT Return error code and disconnect client - DENY Return error code. - Anything Else... Give the default answer of __250 OK__. Arguments are my ($self,$transaction,@args) = @_; # Authentication hooks See `docs/authentication.pod`.