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Mail::DKIM::ARC::Signer(3)



NAME

       Mail::DKIM::ARC::Signer - generates a DKIM signature for a message


SYNOPSIS

         use Mail::DKIM::ARC::Signer;
         use Mail::DKIM::TextWrap;  #recommended

         # create a signer object
         my $signer = Mail::DKIM::ARC::Signer->new(
                         Algorithm => 'rsa-sha256',
                         Chain => 'none',    # or pass|fail|ar
                         Domain => 'example.org',
                         SrvId => 'example.org',
                         Selector => 'selector1',
                         KeyFile => 'private.key',
                         Headers => 'x-header:x-header2',
                    );

         # read an email from a file handle
         $signer->load(*STDIN);

         # NOTE: any email being ARC signed must have an Authentication-Results
         # header so that the ARC seal can cover those results copied into
         # an ARC-Authentication-Results header.

         # or read an email and pass it into the signer, one line at a time
         while (<STDIN>)
         {
             # remove local line terminators
             chomp;
             s/\015$//;

             # use SMTP line terminators
             $signer->PRINT("$_\015\012");
         }
         $signer->CLOSE;

         die 'Failed' $signer->result_details() unless $signer->result() eq 'sealed';

         # Get all the signature headers to prepend to the message
         # ARC-Seal, ARC-Message-Signature and ARC-Authentication-Results
         # in that order.
         print $signer->as_string;


DESCRIPTION

       This class is the part of Mail::DKIM responsible for generating ARC
       Seals for a given message. You create an object of this class,
       specifying the parameters for the ARC-Message-Signature you wish to
       create.

       You also need to pass the 'Chain' value (pass or fail) from validation
       of the previous ARC-Seals on the message.

       Next, you feed it the entire message using "PRINT()", completing with
       "CLOSE()".

       Finally, use the "as_string()" method to get the new ARC headers.

       Note: you can only seal a message which has already had an
       Authentication-Results header added, either by using "PRINT()" to pre-
       feed it into this module, or by adding a message which has already been
       authenticated by your inbound scanning mechanisms.

       It is not necessary to ARC-Seal a message which already has DKIM
       signatures if you are not modifying the message and hence breaking the
       existing DKIM-Signature or top ARC-Message-Signature on the email.

   Pretty Signatures
       Mail::DKIM includes a signature-wrapping module (which inserts
       linebreaks into the generated signature so that it looks nicer in the
       resulting message. To enable this module, simply call

         use Mail::DKIM::TextWrap;

       in your program before generating the signature.


CONSTRUCTOR

   new()
       Construct an object-oriented signer.

         # create a signer using the default policy
         my $signer = Mail::DKIM::ARC::Signer->new(
                         Algorithm => 'rsa-sha256',
                         Chain => 'none',    # or pass|fail|ar
                         Domain => 'example.org',
                         SrvId => 'example.org',
                         Selector => 'selector1',
                         KeyFile => 'private.key',
                         Headers => 'x-header:x-header2',
                    );

       Key rather than using "KeyFile", use "Key" to use an already-loaded
           Mail::DKIM::PrivateKey object.

       Chain
           The cv= value for the Arc-Seal header.  "ar" means to copy it from
           an Authentication-Results header, or use none if there isn't one.

       SrvId
           The authserv-id in the Authentication-Results headers, defaults to
           Domain.

       Headers
           A colon separated list of headers to sign, this is added to the
           list of default headers as shown in in the DKIM specification.

           For each specified header all headers of that type which are
           present in the message will be signed, but we will not oversign or
           sign headers which are not present.

           If you require greater control over signed headers please use the
           extended_headers() method instead.

           The list of headers signed by default is as follows

               From Sender Reply-To Subject Date
               Message-ID To Cc MIME-Version
               Content-Type Content-Transfer-Encoding Content-ID Content-Description
               Resent-Date Resent-From Resent-Sender Resent-To Resent-cc
               Resent-Message-ID
               In-Reply-To References
               List-Id List-Help List-Unsubscribe List-Subscribe
               List-Post List-Owner List-Archive


METHODS

   PRINT()
       Feed part of the message to the signer.

         $signer->PRINT("a line of the message\015\012");

       Feeds content of the message being signed into the signer.  The API is
       designed this way so that the entire message does NOT need to be read
       into memory at once.

       Please note that although the PRINT() method expects you to use SMTP-
       style line termination characters, you should NOT use the SMTP-style
       dot-stuffing technique described in RFC 2821 section 4.5.2.  Nor should
       you use a <CR><LF>.<CR><LF> sequence to terminate the message.

   CLOSE()
       Call this when finished feeding in the message.

         $signer->CLOSE;

       This method finishes the canonicalization process, computes a hash, and
       generates a signature.

   extended_headers()
       This method overrides the headers to be signed and allows more control
       than is possible with the Headers property in the constructor.

       The method expects a HashRef to be passed in.

       The Keys are the headers to sign, and the values are either the number
       of headers of that type to sign, or the special values '*' and '+'.

       * will sign ALL headers of that type present in the message.

       + will sign ALL + 1 headers of that type present in the message to
       prevent additional headers being added.

       You may override any of the default headers by including them in the
       hashref, and disable them by giving them a 0 value.

       Keys are case insensitive with the values being added upto the highest
       value.

           Headers => {
               'X-test'  => '*',
               'x-test'  => '1',
               'Subject' => '+',
               'Sender'  => 0,
           },

   add_signature()
       Used by signer policy to create a new signature.

         $signer->add_signature(new Mail::DKIM::Signature(...));

       Signer policies can use this method to specify complete parameters for
       the signature to add, including what type of signature. For more
       information, see Mail::DKIM::SignerPolicy.

   algorithm()
       Get or set the selected algorithm.

         $alg = $signer->algorithm;

         $signer->algorithm('rsa-sha256');

   domain()
       Get or set the selected domain.

         $alg = $signer->domain;

         $signer->domain('example.org');

   load()
       Load the entire message from a file handle.

         $signer->load($file_handle);

       Reads a complete message from the designated file handle, feeding it
       into the signer.  The message must use <CRLF> line terminators (same as
       the SMTP protocol).

   headers()
       Determine which headers to put in signature.

         my $headers = $signer->headers;

       This is a string containing the names of the header fields that will be
       signed, separated by colons.

   key()
       Get or set the private key object.

         my $key = $signer->key;

         $signer->key(Mail::DKIM::PrivateKey->load(File => 'private.key'));

       The key object can be any object that implements the sign_digest()
       method.  (Providing your own object can be useful if your actual keys
       are stored out-of-process.)

       If you use this method to specify a private key, do not use
       "key_file()".

   key_file()
       Get or set the filename containing the private key.

         my $filename = $signer->key_file;

         $signer->key_file('private.key');

       If you use this method to specify a private key file, do not use
       "key()".

   message_originator()
       Access the "From" header.

         my $address = $signer->message_originator;

       Returns the "originator address" found in the message, as a
       Mail::Address object.  This is typically the (first) name and email
       address found in the From: header. If there is no From: header, then an
       empty Mail::Address object is returned.

       To get just the email address part, do:

         my $email = $signer->message_originator->address;

       See also "message_sender()".

   message_sender()
       Access the "From" or "Sender" header.

         my $address = $dkim->message_sender;

       Returns the "sender" found in the message, as a Mail::Address object.
       This is typically the (first) name and email address found in the
       Sender: header. If there is no Sender: header, it is the first name and
       email address in the From: header. If neither header is present, then
       an empty Mail::Address object is returned.

       To get just the email address part, do:

         my $email = $dkim->message_sender->address;

       The "sender" is the mailbox of the agent responsible for the actual
       transmission of the message. For example, if a secretary were to send a
       message for another person, the "sender" would be the secretary and the
       "originator" would be the actual author.

   selector()
       Get or set the current key selector.

         $alg = $dkim->selector;

         $dkim->selector('alpha');

   signatures()
       Access list of generated signature objects.

         my @signatures = $dkim->signatures;

       Returns all generated signatures, as a list.

   as_string()
       Returns the new ARC headers

         my $pre_headers = $signer->as_string();

       The headers are separated by \015\012 (SMTP line separator) including a
       trailing separator, so can be directly injected in front of the raw
       message.

   as_strings()
       Returns the new ARC headers

         my @pre_headers = $signer->as_string();

       The headers are returned as a list so you can add whatever line ending
       your local MTA prefers.


AUTHOR

       Bron Gondwana, <brong@fastmailteam.com>


COPYRIGHT AND LICENSE

       Copyright (C) 2017 FastMail Pty Ltd

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself, either Perl version 5.8.6 or, at
       your option, any later version of Perl 5 you may have available.



perl v5.24.3                      2017-12-16        Mail::DKIM::ARC::Signer(3)

mail-dkim 0.500.0 - Generated Fri Jan 5 10:30:16 CST 2018
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