Mail::DKIM::Signer

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



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

SYNOPSIS
	 use Mail::DKIM::Signer;

	 # 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;

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 sig-
       nature 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.

       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"));

       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 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 subrou-
       tine reference. The method/subroutine will be called with the signer
       object as an argument. The policy is responsible for checking the mes-
       sage 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 signa-
       ture, 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 v5.8.8			  2009-05-22		Mail::DKIM::Signer(3)