Generating DKIM Signatures VIA Python For Custom MTA
Ok, so I am not completely lost with DKIM. I know the general rules of encoding and setting DNS records with your public key, etc. What I am having issues with is incorporating the
Solution 1:
I would like to thank Georg Zimmer for the above answer. I ran into some difficulties running this on Python 3.6.2 as some of the "byte" / "string" items have changed since 2.x versions. Below is code to make a MIMEMultipart (text/HTML) and signed with DKIM. I used dkimpy-0.6.2.
My very first StackOverflow post. Hope it helps you...
import smtplib, dkim, time, os
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
print('Content-Type: text/plain')
print('')
msg = MIMEMultipart('alternative')
msg['From'] = 'test@example.com'
msg['To'] = 'person@anotherexample.com'
msg['Subject'] = ' Test Subject'
msg['Message-ID'] = "<" + str(time.time()) + "-1234567890@example.com" + ">"
# Create the body of the message (a plain-text and an HTML version).
text = """\
Test email displayed as text only
"""
html = """\
<!doctype html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office">
<head>
<title>Test DKMI Email</title>
</head>
<body>
HTML Body of Test DKIM
</body>
</html>
"""
# Record the MIME types of both parts - text/plain and text/html.
part1 = MIMEText(text, 'plain')
part2 = MIMEText(html, 'html')
msg.attach(part1)
msg.attach(part2)
# DKIM Private Key for example.com RSA-2048bit
privateKey = open(os.path.join('C:\\dev\\python\\', '2048.example.com.priv')).read()
# Specify headers in "byte" form
headers=[b'from', b'to', b'subject', b'message-id']
# Generate message signature
sig = dkim.sign(msg.as_bytes(), b'introduction', b'example.com', privateKey.encode(), include_headers=headers)
sig = sig.decode()
# Add the DKIM-Signature
msg['DKIM-Signature'] = sig[len("DKIM-Signature: "):]
# Send the message via local SMTP server.
s = smtplib.SMTP('localhost')
# sendmail function takes 3 arguments: sender's address, recipient's address
# and message to send - here it is sent as one string.
s.sendmail(msg['From'], msg['To'], msg.as_string())
s.quit()
Solution 2:
To build on the previous two answers, I have a few additional tips.
- Be sure you run
pip install dkimpy
- Generate the private key. On Unix:
openssl genrsa -out dkimprivatekey.pem 1024- Generate the public. On Unix:
openssl rsa -in dkimprivatekey.pem -out public.pem -pubout- Add the public key to your DNS with the selector "introduction" (which is what the example above uses.
- Provide the path and filename to your private key in the code above (the example above uses
C:\dev\python\and2048.example.com.priv)
Solution 3:
This should help.
I looked at the tests and the command line tools included in the project to learn how to use it.
Here is a code fragment which will give you an idea of how to use it. Sorry I can't provide more.
self.dkim_private = open(os.path.join(settings.PROJECT_DIR, 'private_key.pem')).read()
... snip ...
msg = MIMEMultipart('alternative')
msg['From'] = "{0} <{1}>".format(self.sendfrom_name, self.sendfrom)
msg['To'] = self.sendto
msg['Date'] = formatdate(localtime=True)
msg['Message-ID'] = self.message_id
msg['Subject'] = self.subject
msg.attach(MIMEText(unicodedata.normalize('NFKD', self.body_text), 'plain'))
msg.attach(MIMEText(self.body, 'html'))
sig = dkim.sign(msg.as_string(), 'myselector',
from_domain, self.dkim_private,
include_headers=['from', 'to', 'subject', 'message-id'])
msg['DKIM-Signature'] = sig[len("DKIM-Signature: "):]
Then you use can use smtplib to send the email.
The private and public keys can be generated easily here:
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