NAME

Mail::SpamAssassin::Plugin - SpamAssassin plugin base class

SYNOPSIS

SpamAssassin configuration:

  loadplugin MyPlugin /path/to/myplugin.pm

Perl code:

  package MyPlugin;

  use Mail::SpamAssassin::Plugin;
  our @ISA = qw(Mail::SpamAssassin::Plugin);

  sub new {
    my ($class, $mailsa) = @_;
    
    # the usual perlobj boilerplate to create a subclass object
    $class = ref($class) || $class;
    my $self = $class->SUPER::new($mailsa);
    bless ($self, $class);
   
    # then register an eval rule, if desired...
    $self->register_eval_rule ("check_for_foo");

    # and return the new plugin object
    return $self;
  }

  ...methods...

1;

DESCRIPTION

This is the base class for SpamAssassin plugins; all plugins must be objects that implement this class.

This class provides no-op stub methods for all the callbacks that a plugin can receive. It is expected that your plugin will override one or more of these stubs to perform its actions.

SpamAssassin implements a plugin chain; each callback event is passed to each of the registered plugin objects in turn. Any plugin can call $self->inhibit_further_callbacks() to block delivery of that event to later plugins in the chain. This is useful if the plugin has handled the event, and there will be no need for later plugins to handle it as well.

If you're looking to write a simple eval rule, skip straight to register_eval_rule(), below.

INTERFACE

In all the plugin APIs below, options refers to a reference to a hash containing name-value pairs. This is used to ensure future-compatibility, in that we can add new options in future without affecting objects built to an earlier version of the API.

For example, here would be how to print out the line item in a parse_config() method:

  sub parse_config {
    my ($self, $opts) = @_;
    print "MyPlugin: parse_config got ".$opts->{line}."\n";
  }

METHODS

The following methods can be overridden by subclasses to handle events that SpamAssassin will call back to:

$plugin = MyPluginClass->new ($mailsaobject)

Constructor. Plugins that need to register themselves will need to define their own; the default super-class constructor will work fine for plugins that just override a method.

Note that subclasses must provide the $mailsaobject to the superclass constructor, like so:

  my $self = $class->SUPER::new($mailsaobject);

Lifecycle note: plugins that will need to store per-scan state should not store that on the Plugin object; see check_start() below. It is also likewise recommended that configuration settings be stored on the Conf object; see parse_config().

$plugin->parse_config ( { options ... } )

Parse a configuration line that hasn't already been handled. options is a reference to a hash containing these options:

line: The line of configuration text to parse. This has leading and trailing whitespace, and comments, removed.
key: The configuration key; ie. the first ``word'' on the line.
value: The configuration value; everything after the first ``word'' and any whitespace after that.
conf: The Mail::SpamAssassin::Conf object on which the configuration data should be stored.
user_config: A boolean: 1 if reading a user's configuration, 0 if reading the system-wide configuration files.

If the configuration line was a setting that is handled by this plugin, the method implementation should call $self->inhibit_further_callbacks().

If the setting is not handled by this plugin, the method should return 0 so that a later plugin may handle it, or so that SpamAssassin can output a warning message to the user if no plugin understands it.

Lifecycle note: it is suggested that configuration be stored on the Mail::SpamAssassin::Conf object in use, instead of the plugin object itself. That can be found as $plugin->{main}->{conf}. This allows per-user and system-wide configuration to be dealt with correctly, with per-user overriding system-wide.

$plugin->signal_user_changed ( { options ... } )

Signals that the current user has changed for a new one.

username: The new user's username.
user_dir: The new user's home directory. (equivalent to ~.)
userstate_dir: The new user's storage directory. (equivalent to ~/.spamassassin.)

$plugin->check_start ( { options ... } )

Signals that a message check operation is starting.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.; Lifecycle note: it is recommended that rules that need to track test state on a per-scan basis should store that state on this object, not on the plugin object itself, since the plugin object will be shared between all active scanners.; The message being scanned is accessible through the $permsgstatus->get_message() API; there are a number of other public APIs on that object, too. See Mail::SpamAssassin::PerMsgStatus perldoc.

$plugin->extract_metadata ( { options ... } )

Signals that a message is being mined for metadata. Some plugins may wish to add their own metadata as well.

msg: The Mail::SpamAssassin::Message object for this message.

$plugin->parsed_metadata ( { options ... } )

Signals that a message's metadata has been parsed, and can now be accessed by the plugin.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.

$plugin->check_tick ( { options ... } )

Called periodically during a message check operation. A callback set for this method is a good place to run through an event loop dealing with network events triggered in a parse_metadata method, for example.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.

$plugin->check_post_dnsbl ( { options ... } )

Called after the DNSBL results have been harvested. This is a good place to harvest your own asynchronously-started network lookups.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.

$plugin->check_post_learn ( { options ... } )

Called after auto-learning may (or may not) have taken place. If you wish to perform additional learning, whether or not auto-learning happens, this is the place to do it.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.

$plugin->check_end ( { options ... } )

Signals that a message check operation has just finished, and the results are about to be returned to the caller.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan. The current score, names of rules that hit, etc. can be retrieved using the public APIs on this object.

$plugin->autolearn ( { options ... } )

Signals that a message is about to be auto-learned as either ham or spam.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.
isspam: 1 if the message is spam, 0 if ham.

$plugin->per_msg_finish ( { options ... } )

Signals that a Mail::SpamAssassin::PerMsgStatus object is being destroyed, and any per-scan context held on that object by this plugin should be destroyed as well.

permsgstatus: The Mail::SpamAssassin::PerMsgStatus context object for this scan.

$plugin->bayes_learn ( { options ... } )

Called at the end of a bayes learn operation.

This phase is the best place to map the raw (original) token value to the SHA1 hashed value.

toksref

Reference to hash returned by call to tokenize. The hash takes the format of:

{

  'SHA1 Hash Value' => 'raw (original) value'

}

NOTE: This data structure has changed since it was originally introduced in version 3.0.0. The values are no longer perl anonymous hashes, they are a single string containing the raw token value. You can test for backwards compatability by checking to see if the value for a key is a reference to a perl HASH, for instance:

if (ref($toksref->{$sometokenkey}) eq 'HASH') {...

If it is, then you are using the old interface, otherwise you are using the current interface.

isspam

Boolean value stating what flavor of message the tokens represent, if true then message was specified as spam, false is nonspam. Note, when function is scan then isspam value is not valid.

msgid

Generated message id of the message just learned.

msgatime

Received date of the current message or current time if received date could not be determined. In addition, if the receive date is more than 24 hrs into the future it will be reset to current datetime.

$plugin->bayes_forget ( { options ... } )

Called at the end of a bayes forget operation.

toksref: Reference to hash returned by call to tokenize. See bayes_learn documentation for additional information on the format.
isspam: Boolean value stating what flavor of message the tokens represent, if true then message was specified as spam, false is nonspam. Note, when function is scan then isspam value is not valid.
msgid: Generated message id of the message just forgotten.

$plugin->bayes_scan ( { options ... } )

Called at the end of a bayes scan operation. NOTE: Will not be called in case of error or if the message is otherwise skipped.

toksref

Reference to hash returned by call to tokenize. See bayes_learn documentation for additional information on the format.

probsref

Reference to hash of calculated probabilities for tokens found in the database.

{

  'SHA1 Hash Value' => {

                         'prob' => 'calculated probability',

                         'spam_count' => 'Total number of spam msgs w/ token',

                         'ham_count' => 'Total number of ham msgs w/ token',

                         'atime' => 'Atime value for token in database'

}

score

Score calculated for this particular message.

msgatime

Calculated atime of the message just learned, note it may have been adjusted if it was determined to be too far into the future.

significant_tokens

Array ref of the tokens found to be significant in determining the score for this message.

$plugin->finish ()

Called when the Mail::SpamAssassin object is destroyed.

HELPER APIS

These methods provide an API for plugins to register themselves to receive specific events, or control the callback chain behaviour.

$plugin->register_eval_rule ($nameofevalsub): Plugins that implement an eval test will need to call this, so that SpamAssassin calls into the object when that eval test is encountered. See the REGISTERING EVAL RULES section for full details.
$plugin->inhibit_further_callbacks(): Tells the plugin handler to inhibit calling into other plugins in the plugin chain for the current callback. Frequently used when parsing configuration settings using parse_config().
dbg ($message): Output a debugging message $message, if the SpamAssassin object is running with debugging turned on.; NOTE: This function is not available in the package namespace of general plugins and can't be called via $self->dbg(). If a plugin wishes to output debug information, it should call Mail::SpamAssassin::Plugin::dbg($msg).

REGISTERING EVAL RULES

Plugins that implement an eval test must register the methods that can be called from rules in the configuration files, in the plugin class' constructor.

For example,

  $plugin->register_eval_rule ('check_for_foo')

will cause $plugin->check_for_foo() to be called for this SpamAssassin rule:

  header   FOO_RULE     eval:check_for_foo()

Note that eval rules are passed the following arguments:

The plugin object itself
The Mail::SpamAssassin::PerMsgStatus object calling the rule
standard arguments for the rule type in use
any and all arguments as specified in the configuration file

In other words, the eval test method should look something like this:

  sub check_for_foo {
    my ($self, $permsgstatus, ...arguments...) = @_;
    ...code returning 0 or 1
  }

Note that the headers can be accessed using the get() method on the Mail::SpamAssassin::PerMsgStatus object, and the body by get_decoded_stripped_body_text_array() and other similar methods. Similarly, the Mail::SpamAssassin::Conf object holding the current configuration may be accessed through $permsgstatus->{main}->{conf}.

The eval rule should return 1 for a hit, or 0 if the rule is not hit.

State for a single message being scanned should be stored on the $checker object, not on the $self object, since $self persists between scan operations. See the 'lifecycle note' on the check_start() method above.

STANDARD ARGUMENTS FOR RULE TYPES

Plugins will be called with the same arguments as a standard EvalTest. Different rule types receive different information by default:

header tests, no extra arguments
body tests, fully rendered message as array reference
rawbody tests, fully decoded message as array reference
full tests, pristine message as scalar reference

The configuration file arguments will be passed in after the standard arguments.