(CkPython) Add DKIM-Signature Header to MIME / Email

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

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

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

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

dkim = chilkat.CkDkim()

# To create a DKIM 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 DKIM signature via an
# external email client supporting DKIM 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 DKIM DNS record creation.  
# (Chilkat does not provide an API for creating DNS records.  
# Creating the DKIM DNS record is something you would do
# manually.)

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

# Load a private key from any common RSA private key
# format, such as DER, PKCS8, PEM, XML, etc.
# The LoadDkimPkFile 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"
privKey = chilkat.CkPrivateKey()
success = privKey.LoadAnyFormatFile("myPrivateKey.pem",password)
if (success != True):
    print(privKey.lastErrorText())
    sys.exit()

success = dkim.SetDkimPrivateKey(privKey)
if (success != True):
    print(dkim.lastErrorText())
    sys.exit()

# Load a MIME file.
mimeData = chilkat.CkByteData()
success = mimeData.loadFile("testMessage.eml")
if (success != True):
    print("Failed to load file.")
    sys.exit()

# Sign it.  This adds the DKIM-Signature header and
# returns the new MIME with DKIM-Signature added.
dkimSignedMime = chilkat.CkByteData()
success = dkim.AddDkimSignature(mimeData,dkimSignedMime)
if (success != True):
    print(dkim.lastErrorText())
    sys.exit()

success = dkimSignedMime.saveFile("dkimSigned.eml")
if (success != True):
    print("Failed to save file.")
    sys.exit()

print("Success.")