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Mail::DKIM::Signer(3)                User Contributed Perl Documentation               Mail::DKIM::Signer(3)



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

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

         # create a signer object
         my $dkim = Mail::DKIM::Signer->new(
                         Algorithm => "rsa-sha1",
                         Method => "relaxed",
                         Domain => "example.org",
                         Selector => "selector1",
                         KeyFile => "private.key",
                    );

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

         # 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
             $dkim->PRINT("$_\015\012");
         }
         $dkim->CLOSE;

         # what is the signature result?
         my $signature = $dkim->signature;
         print $signature->as_string;

DESCRIPTION
       This class is the part of Mail::DKIM responsible for generating signatures for a given message. You
       create an object of this class, specifying the parameters of the signature you wish to create, or
       specifying a callback function so that the signature parameters can be determined later. Next, you
       feed it the entire message using "PRINT()", completing with "CLOSE()". Finally, use the
       "signatures()" method to access the generated signatures.

   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 $dkim = Mail::DKIM::Signer->new(
                         Algorithm => "rsa-sha1",
                         Method => "relaxed",
                         Domain => "example.org",
                         Selector => "selector1",
                         KeyFile => "private.key",
                    );

         # create a signer using a custom policy
         my $dkim = Mail::DKIM::Signer->new(
                         Policy => $policyfn,
                    );

       The "default policy" is to create a DKIM signature using the specified parameters, but only if the
       message's sender matches the domain.  The following parameters can be passed to this new() method to
       influence the resulting signature: Algorithm, Method, Domain, Selector, KeyFile, Identity, Timestamp.

       If you want different behavior, you can provide a "signer policy" instead. A signer policy is a
       subroutine or class that determines signature parameters after the message's headers have been
       parsed.  See the section "SIGNER POLICIES" below for more information.

       See Mail::DKIM::SignerPolicy for more information about policy objects.

       In addition to the parameters demonstrated above, the following are recognized:

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

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

         $dkim->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.

         $dkim->CLOSE;

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

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

         $dkim->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 = $dkim->algorithm;

         $dkim->algorithm("rsa-sha1");

   domain()
       Get or set the selected domain.

         $alg = $dkim->domain;

         $dkim->domain("example.org");

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

         $dkim->load($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 = $dkim->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 = $dkim->key;

         $dkim->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 = $dkim->key_file;

         $dkim->key_file("private.key");

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

   method()
       Get or set the selected canonicalization method.

         $alg = $dkim->method;

         $dkim->method("relaxed");

   message_originator()
       Access the "From" header.

         my $address = $dkim->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 = $dkim->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");

   signature()
       Access the generated signature object.

         my $signature = $dkim->signature;

       Returns the generated signature. The signature is an object of type Mail::DKIM::Signature. If
       multiple signatures were generated, this method returns the last one.

       The signature (as text) should be prepended to the message to make the resulting message. At the very
       least, it should precede any headers that were signed.

   signatures()
       Access list of generated signature objects.

         my @signatures = $dkim->signatures;

       Returns all generated signatures, as a list.

SIGNER POLICIES
       The new() constructor takes an optional Policy argument. This can be a Perl object or class with an
       apply() method, or just a simple subroutine reference. The method/subroutine will be called with the
       signer object as an argument. The policy is responsible for checking the message and specifying
       signature parameters. The policy must return a nonzero value to create the signature, otherwise no
       signature will be created. E.g.,

         my $policyfn = sub {
             my $dkim = shift;

             # specify signature parameters
             $dkim->algorithm("rsa-sha1");
             $dkim->method("relaxed");
             $dkim->domain("example.org");
             $dkim->selector("mx1");

             # return true value to create the signature
             return 1;
         };

       Or the policy object can actually create the signature, using the add_signature method within the
       policy object.  If you add a signature, you do not need to return a nonzero value.  This mechanism
       can be utilized to create multiple signatures, or to create the older DomainKey-style signatures.

         my $policyfn = sub {
             my $dkim = shift;
             $dkim->add_signature(
                     new Mail::DKIM::Signature(
                             Algorithm => "rsa-sha1",
                             Method => "relaxed",
                             Headers => $dkim->headers,
                             Domain => "example.org",
                             Selector => "mx1",
                     ));
             $dkim->add_signature(
                     new Mail::DKIM::DkSignature(
                             Algorithm => "rsa-sha1",
                             Method => "nofws",
                             Headers => $dkim->headers,
                             Domain => "example.org",
                             Selector => "mx1",
                     ));
             return;
         };

       If no policy is specified, the default policy is used. The default policy signs every message using
       the domain, algorithm, method, and selector specified in the new() constructor.

SEE ALSO
       Mail::DKIM::SignerPolicy

AUTHOR
       Jason Long, <jlong@messiah.edu>

COPYRIGHT AND LICENSE
       Copyright (C) 2006-2007 by Messiah College

       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 v5.16.2                                     2010-11-14                            Mail::DKIM::Signer(3)