lazyj.mail.filters

Class DKIMSigner

java.lang.Object

lazyj.mail.filters.DKIMSigner

All Implemented Interfaces:

MailFilter

public class DKIMSigner
extends java.lang.Object
implements MailFilter

This class is used as a Sendmail filter to sign the mail with a private key.

Here is an example of how you can generate the keys:

• private key generation:
  openssl genrsa -out rsa.private 1024
• extract public key:
  openssl rsa -in rsa.private -out rsa.public -pubout -outform PEM
• convert private key to PKCS8 (to load in Java):
  openssl pkcs8 -topk8 -nocrypt -in rsa.private -inform PEM -out rsa.private.der -outform DER
• publish the contents of the public key in DNS by adding the following entries to your domain:
  _domainkey IN TXT "t=y; o=-;"
  dkim._domainkey IN TXT "k=rsa; t=y; h=sha256; v=DKIM1; p=[contents of rsa.public, only between BEGIN and END, on a single line]"
• once the testing phase is complete, remove "t=y" from the above, to signal the recipients that you are serious about using this method of verification

And then the code is simple:

 Mail mail = new Mail();
 //fill in the mail
 
 DKIMSigner signer = new DKIMSigner("domain.com", "dkim", "rsa.private.der");
 Sendmail sendmail = new Sendmail(m.sFrom);
 sendmail.registerFilter(signer);
 sendmail.send(mail);
 

References:

• http://dkim.org/specs/rfc4871-dkimbase.html
• http://testing.dkim.org/reflector.html

Since:

Sep 15, 2009, 1.0.6

Author:

costing

See Also:

Sendmail.registerFilter(MailFilter)

Constructor Summary

Constructors

Constructor and Description
DKIMSigner(java.lang.String sDomain, java.lang.String sDNSSelector, java.lang.String sKeyPath) DKIM signer

Method Summary

Methods

Modifier and Type	Method and Description
boolean	addHeader(java.lang.String sHeader) Add another header to the signature
void	clearHeader() Remove all headers, start clean
void	filter(java.util.Map<java.lang.String,java.lang.String> mailHeaders, java.lang.String sBody, Mail mail) Filter the mail contents and the headers.
static java.lang.String	relaxedHeader(java.lang.String key, java.lang.String value) Implement the "relaxed" method for headers
boolean	removeHeader(java.lang.String sHeader) Remove a header from the signature
static java.lang.String	simpleBody(java.lang.String body) Implement the "simple" method for body

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DKIMSigner

public DKIMSigner(java.lang.String sDomain,
          java.lang.String sDNSSelector,
          java.lang.String sKeyPath)
           throws java.io.IOException,
                  java.security.NoSuchAlgorithmException,
                  java.security.spec.InvalidKeySpecException,
                  java.security.InvalidKeyException

DKIM signer

Parameters:

sDomain -

sDNSSelector -

sKeyPath - path to the file containing the private RSA key

Throws:

java.io.IOException - when the key file cannot be read

java.security.NoSuchAlgorithmException - if the algorithm is unknown

java.security.spec.InvalidKeySpecException - if the contents of the private key file is not ok

java.security.InvalidKeyException - when the signature cannot make use of the given private key

Method Detail

addHeader

public boolean addHeader(java.lang.String sHeader)

Add another header to the signature

Parameters:

sHeader -

Returns:

true if it was really added, false if it was already in the list

removeHeader

public boolean removeHeader(java.lang.String sHeader)

Remove a header from the signature

Parameters:

sHeader -

Returns:

true if it was really removed, false if it was not defined

clearHeader

public void clearHeader()

Remove all headers, start clean

filter

public void filter(java.util.Map<java.lang.String,java.lang.String> mailHeaders,
          java.lang.String sBody,
          Mail mail)

Description copied from interface: MailFilter

Filter the mail contents and the headers. The filters are called just before sending the headers to the server so it's still ok to tamper with the headers and/or mail contents.

Specified by:

filter in interface MailFilter

Parameters:

mailHeaders - full set of headers, just before sending them to the server

sBody - full mail body

mail - the original mail

relaxedHeader

public static java.lang.String relaxedHeader(java.lang.String key,
                             java.lang.String value)

Implement the "relaxed" method for headers

Parameters:

key - header key

value - value

Returns:

canonical value

simpleBody

public static java.lang.String simpleBody(java.lang.String body)

Implement the "simple" method for body

Parameters:

body -

Returns:

canonical value