new()

  my $dkim = Mail::DKIM::Verifier->new();

  my $dkim = Mail::DKIM::Verifier->new(%options);

The only options supported at this time are:

Debug_Canonicalization

if specified, the canonicalized message for the first signature is written to the referenced string or file handle.

Strict

If true, rejects sha1 hashes and signing keys shorter than 1024 bits.

PRINT()

  $dkim->PRINT("a line of the message\015\012");
  $dkim->PRINT('more of');
  $dkim->PRINT(" the message\015\012bye\015\012");

Feeds content of the message being verified into the verifier. 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()

  $dkim->CLOSE;

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

fetch_author_domain_policies()

  my @policies = $dkim->fetch_author_domain_policies;
  foreach my $policy (@policies)
  {
      my $policy_result = $policy->apply($dkim);
  }

This method will retrieve all applicable "author-domain-signing-practices" published in DNS for this message. Author policies are keyed to the email address(es) in the From: header, i.e. the claimed author of the message.

This method returns a *list* of policy records, since there is allowed to be zero or multiple email addresses in the From: header.

The result of the apply() method is one of: "accept", "reject", "neutral".

See also: "policies()".

fetch_author_policy()

  my $policy = $dkim->fetch_author_policy;
  my $policy_result = $policy->apply($dkim);

This method retrieves the DKIM Sender Signing Practices record as described in Internet Draft draft-ietf-dkim-ssp-00-01dc. This Internet Draft is now obsolete; this method is only kept for backward-compatibility purposes.

Please use the "policies()" method instead.

fetch_sender_policy()

  my $policy = $dkim->fetch_sender_policy;
  my $policy_result = $policy->apply($dkim);

The "sender" policy is the sender signing policy as described by the DomainKeys specification, now available in RFC4870(historical). I call it the "sender" policy because it is keyed to the email address in the Sender: header, or the From: header if there is no Sender header. This is the person whom the message claims as the "transmitter" of the message (not necessarily the author).

If the email being verified has no From or Sender header from which to get an email address (which violates email standards), then this method will "die".

The result of the apply() method is one of: "accept", "reject", "neutral".

See also: "policies()".

load()

  $dkim->load($file_handle);

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

message_originator()

  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()

  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.

policies()

  my @policies = $dkim->policies;
  foreach my $policy (@policies)
  {
      $policy_result = $policy->apply($dkim);
      # $policy_result is one of "accept", "reject", "neutral"
  }

This method searches for and returns any signing policies that would apply to this message. Signing policies are selected based on the domain that the message *claims* to be from. So, for example, if a message claims to be from security@bank, and forwarded by trusted@listserv, when in reality the message came from foe@evilcorp, this method would check for signing policies for security@bank and trusted@listserv. The signing policies might tell whether foe@evilcorp (the real sender) is allowed to send mail claiming to be from your bank or your listserv.

I say "might tell", because in reality this is still really hard to specify with any accuracy. In addition, most senders do not publish useful policies.

result()

  my $result = $dkim->result;

Gives the result of the verification. The following values are possible:

pass

Returned if a valid DKIM-Signature header was found, and the signature contains a correct value for the message.

fail

Returned if a valid DKIM-Signature header was found, but the signature does not contain a correct value for the message.

invalid

Returned if a DKIM-Signature could not be checked because of a problem in the signature itself or the public key record. I.e. the signature could not be processed.

temperror

Returned if a DKIM-Signature could not be checked due to some error which is likely transient in nature, such as a temporary inability to retrieve a public key. A later attempt may produce a better result.

none

Returned if no DKIM-Signature headers (valid or invalid) were found.

In case of multiple signatures, the "best" result will be returned. Best is defined as "pass", followed by "fail", "invalid", and "none". To examine the results of individual signatures, use the "signatures()" method to retrieve the signature objects. See "result()" in Mail::DKIM::Signature.

result_detail()

  my $detail = $dkim->result_detail;

The detail is constructed by taking the result (e.g. "pass", "fail", "invalid" or "none") and appending any details provided by the verification process in parenthesis.

The following are possible results from the result_detail() method:

  pass
  fail (bad RSA signature)
  fail (OpenSSL error: ...)
  fail (message has been altered)
  fail (body has been altered)
  invalid (bad identity)
  invalid (invalid domain in d tag)
  invalid (missing q tag)
  invalid (missing d tag)
  invalid (missing s tag)
  invalid (unsupported version 0.1)
  invalid (unsupported algorithm ...)
  invalid (unsupported canonicalization ...)
  invalid (unsupported query protocol ...)
  invalid (signature is expired)
  invalid (public key: not available)
  invalid (public key: unknown query type ...)
  invalid (public key: syntax error)
  invalid (public key: unsupported version)
  invalid (public key: unsupported key type)
  invalid (public key: missing p= tag)
  invalid (public key: invalid data)
  invalid (public key: does not support email)
  invalid (public key: does not support hash algorithm 'sha1')
  invalid (public key: does not support signing subdomains)
  invalid (public key: revoked)
  invalid (public key: granularity mismatch)
  invalid (public key: granularity is empty)
  invalid (public key: OpenSSL error: ...)
  none

signature()

  my $sig = $dkim->signature;

Accesses the signature found and verified in this message. The returned object is of type Mail::DKIM::Signature.

In case of multiple signatures, the signature with the "best" result will be returned. Best is defined as "pass", followed by "fail", "invalid", and "none".

signatures()

  my @all_signatures = $dkim->signatures;

Use $signature->result or $signature->result_detail to access the verification results of each signature.