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NAME

Mail::DMARC - Perl implementation of DMARC

VERSION

version 1.20240314

SYNOPSIS

DMARC: Domain-based Message Authentication, Reporting and Conformance

my $dmarc = Mail::DMARC::PurePerl->new(
  ... # see the documentation for the "new" method for required args
);

my $result = $dmarc->validate();

if ( $result->result eq 'pass' ) {
   ...continue normal processing...
   return;
};

# any result that did not pass is a fail. Now for disposition

if ( $result->evalated->disposition eq 'reject' ) {
   ...treat the sender to a 550 ...
};
if ( $result->evalated->disposition eq 'quarantine' ) {
   ...assign a bunch of spam points...
};
if ( $result->evalated->disposition eq 'none' ) {
   ...continue normal processing...
};

DESCRIPTION

This module is a suite of tools for implementing DMARC. It adheres to the 2013 DMARC draft, intending to implement every MUST and every SHOULD.

This module can be used by...

When a message arrives via SMTP, the MTA or filtering application can pass in a small amount of metadata about the connection (envelope details, SPF and DKIM results) to Mail::DMARC. When the validate method is called, Mail::DMARC will determine if:

a. the header_from domain exists
b. the header_from domain publishes a DMARC policy
c. if a policy is published...
d. does the message conform to the published policy?
e. did the policy request reporting? If so, save details.

The validation results are returned as a Mail::DMARC::Result object. If the author domain requested a report, it was saved to the Report Store. The Store class includes a SQL implementation that is tested with SQLite, MySQL and PostgreSQL.

There is more information available in the $result object. See Mail::DMARC::Result for complete details.

Reports are viewed with the dmarc_view_reports program or with a web browser and the dmarc_httpd program.

Aggregate reports are sent to their requestors with the dmarc_send_reports program.

For aggregate reports that you have been sent, the dmarc_receive program will parse the email messages (from IMAP, Mbox, or files) and save the report results into the Report Store.

The report store can use the same database to store reports you have received as well as reports you will send. There are several ways to identify the difference, including:

CLASSES

Mail::DMARC - the perl interface for DMARC

Mail::DMARC::Policy - a DMARC policy

Mail::DMARC::PurePerl - Pure Perl implementation of DMARC

Mail::DMARC::Result - the results of applying policy

Mail::DMARC::Report - Reporting: the R in DMARC

Mail::DMARC::Report::Send - send reports via SMTP & HTTP

Mail::DMARC::Report::Receive - receive and store reports from email, HTTP

Mail::DMARC::Report::Store - a persistent data store for aggregate reports

Mail::DMARC::Report::View - CLI and CGI methods for viewing reports

Mail::DMARC::libopendmarc - an XS implementation using libopendmarc

METHODS

new

Create a DMARC object.

my $dmarc = Mail::DMARC::PurePerl->new;

Populate it.

$dmarc->source_ip('192.0.1.1');
$dmarc->envelope_to('recipient.example.com');
$dmarc->envelope_from('sender.example.com');
$dmarc->header_from('sender.example.com');
$dmarc->dkim( $dkim_verifier );
$dmarc->spf([
    {   domain => 'example.com',
        scope  => 'mfrom',
        result => 'pass',
    },
    {
        scope  => 'helo',
        domain => 'mta.example.com',
        result => 'fail',
    },
]);

Run the request:

my $result = $dmarc->validate();

Alternatively, pass in all the required parameters in one shot:

my $dmarc = Mail::DMARC::PurePerl->new(
        source_ip     => '192.0.1.1',
        envelope_to   => 'example.com',
        envelope_from => 'cars4you.info',
        header_from   => 'yahoo.com',
        dkim          => $dkim_results,  # same format
        spf           => $spf_results,   # as previous example
        );
my $result = $dmarc->validate();

source_ip

The remote IP that attempted sending the message. DMARC only uses this data for reporting to domains that request DMARC reports.

envelope_to

The domain portion of the RFC5321.RcptTo, (aka, the envelope recipient), and the bold portion in the following example:

RCPT TO:<user@example.com>

envelope_from

The domain portion of the RFC5321.MailFrom, (aka, the envelope sender). That is the the bold portion in the following example:

MAIL FROM:<user@example.com>

header_from

The domain portion of the RFC5322.From, aka, the From message header.

From: Ultimate Vacation <sweepstakes@example.com>

You can instead pass in the entire From: header with header_from_raw.

header_from_raw

Retrieve the header_from domain by parsing it from a raw From field/header. The domain portion is extracted by get_dom_from_header, which is fast, generally effective, but also rather crude. It has limits, so read the description.

dkim

If Mail::DKIM::Verifier was used to validate the message, just pass in the Mail::DKIM::Verifier object that processed the message:

$dmarc->dkim( $dkim_verifier );

Otherwise, pass in an array reference. Each member of the DKIM array results represents a DKIM signature in the message and consists of the 4 keys shown in this example:

$dmarc->dkim( [
        {
            domain      => 'example.com',
            selector    => 'apr2013',
            result      => 'fail',
            human_result=> 'fail (body has been altered)',
        },
        {
            # 2nd signature, if present
        },
    ] );

The dkim results can also be build iteratively by passing in key value pairs or hash references for each signature in the message:

$dmarc->dkim( domain => 'sig1.com', result => 'fail' );
$dmarc->dkim( domain => 'sig2.com', result => 'pass' );
$dmarc->dkim( { domain => 'example.com', result => 'neutral' } );

Each hash or hashref is appended to the dkim array.

Finally, you can pass a coderef which won't be called until the dkim method is used to read the dkim results. It must return an array reference as described above.

The dkim result is an array reference.

domain

The d= parameter in the DKIM signature

selector

The s= parameter in the DKIM signature

result

The validation results of this signature. One of: none, pass, fail, policy, neutral, temperror, or permerror

human result

Additional information about the DKIM result. This is comparable to Mail::DKIM::Verifier->result_detail.

spf

The spf method works exactly the same as dkim. It accepts named arguments, a hashref, an arrayref, or a coderef:

$dmarc->spf(
    domain => 'example.com',
    scope  => 'mfrom',
    result => 'pass',
);

The SPF domain and result are required for DMARC validation and the scope is used for reporting.

domain

The SPF checked domain

scope

The scope of the checked domain: mfrom, helo

result

The SPF result code: none, neutral, pass, fail, softfail, temperror, or permerror.

DESIGN & GOALS

Correct

The DMARC spec is lengthy and evolving, making correctness a moving target. In cases where correctness is ambiguous, options are generally provided.

Easy to use

Providing an implementation of DMARC that SMTP utilities can utilize will aid DMARC adoption.

The list of dependencies appears long because of reporting. If this module is used without reporting, the number of dependencies not included with perl is about 5.

Maintainable

Since DMARC is evolving, this implementation aims to be straight forward and easy to alter and extend. The programming style is primarily OO, which carries a small performance penalty but dividends in maintainability.

When multiple options are available, such as when sending reports via SMTP or HTTP, calls should be made to the parent Send class to broker the request. When storing reports, calls are made to the Store class which dispatches to the SQL class. The idea is that if someone desired a data store other than those provided by perl's DBI class, they could easily implement their own. If you do, please fork it on GitHub and share.

Fast

If you deploy this in an environment where performance is insufficient, please profile the app and submit a report and preferably, patches.

SEE ALSO

Mail::DMARC on GitHub

2015-03 RFC 7489

DMARC Best Current Practices

HISTORY

The daddy of this perl module was a DMARC module for the qpsmtpd MTA.

AUTHORS

CONTRIBUTORS

COPYRIGHT AND LICENSE

This software is copyright (c) 2024 by Matt Simerson.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.