(Ruby) Add DomainKey-Signature Header to MIME / Email

Demonstrates how to add a DomainKey-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

dkim = Chilkat::CkDkim.new()

# To create a DomainKey signature for email (i.e. MIME),
# you'll need to provide the following:
# (1) An RSA private key in any common file format.
# (2) The domain name (typically the same domain
# as the sender of an email).
# (3) A selector for the domain name -- an arbitrary string
# to identify the matching public key in DNS.

# To allow an email recipient to verify the DomainKey signature via an
# external email client supporting DomainKey or using other software,
# you will need to create a DNS record with the selector
# and matching public key.  This example does not provide
# information about DomainKey DNS record creation.  
# (Chilkat does not provide an API for creating DNS records.  
# Creating the DomainKey DNS record is something you would do
# manually.)

# Set the domain and selector:
# You'll need to provide your own values here..
dkim.put_DomainKeyDomain("chilkatsoft.com")
dkim.put_DomainKeySelector("salmon")

# Load a private key from any common RSA private key
# format, such as DER, PKCS8, PEM, XML, etc.
# The LoadDomainKeyPkFile method automatically detects
# the file format and reads it appropriately.
# If a password is not required, you'll still need to provide
# a password string argument, but it is ignored.

password = "optionalPassword"
success = dkim.LoadDomainKeyPkFile("myPrivateKey.pem",password)
if (success != true)
    print dkim.lastErrorText() + "\n";
    exit
end

# Load a MIME file.
mimeData = Chilkat::CkByteData.new()

success = mimeData.loadFile("testMessage.eml")
if (success != true)
    print "Failed to load file." + "\n";
    exit
end

# Sign it.  This adds the DomainKey-Signature header and
# returns the new MIME with DomainKey-Signature added.
domainKeySignedMime = Chilkat::CkByteData.new()
success = dkim.AddDomainKeySignature(mimeData,domainKeySignedMime)
if (success != true)
    print dkim.lastErrorText() + "\n";
    exit
end

success = domainKeySignedMime.saveFile("domainKeySigned.eml")
if (success != true)
    print "Failed to save file." + "\n";
    exit
end

print "Success." + "\n";