How to start TLS on an active connection in python

Question

The following is my current code for connecting to gmail's smtp server on port 587. After issuing the STARTTLS command how would I finish negotiating the TLS session and begin issuing commands such as AUTH LOGIN and MAIL FROM? I have ommitted my Base64 encoded gmail username and replaced it with xxxxxxxx near the bottom of my code.

My output from this program as it is, is:

220 mx.google.com ESMTP y10sm3296641yhd.6

250-mx.google.com at your service, [75.66.47.144]

250-SIZE 35882577

250-8BITMIME

250-STARTTLS

250 ENHANCEDSTATUSCODES

220 2.0.0 Ready to start TLS

from socket import *
import ssl
msg = "\r\n smtp.."
endmsg = "\r\n.\r\n"

# Mailserver hostname and port to be used.
mailserver = ("smtp.gmail.com", 587)


# Create a socket and create an active TCP connection with the mailserver
clientSocket = socket(AF_INET, SOCK_STREAM);
clientSocket.connect(mailserver)

# Read server response
recv = clientSocket.recv(1024)
print recv
if recv[:3] != '220':
    print '220 reply not received from server.'

# Send EHLO command and print server response.
ehloCommand = 'EHLO smtp.google.com\r\n'
clientSocket.send(ehloCommand)

recv1 = clientSocket.recv(1024)
print recv1
if recv1[:3] != '250':
    print '250 reply not received from server.'

# Send STARTTLS command to server and print server response
command = "STARTTLS\r\n"
clientSocket.send(command)

recv1 = clientSocket.recv(1024)
print recv1
if recv[:3] != '220':
    print '220 reply not received from server.'

# SEND AUTH LOGIN command and Base64 encoded username
command = "AUTH LOGIN xxxxxxxxxxxxx\r\n"
clientSocket.send(command)

recv1 = clientSocket.recv(1024)
print recv1

Answer 1

You can ssl wrap a connected socket. This will give you the idea:

import ssl
import base64
from socket import *


cc = socket(AF_INET, SOCK_STREAM)
cc.connect(("smtp.gmail.com", 587))
# cc.read(..)

cc.send('helo tester.com\r\n')
cc.send('starttls\r\n')
# cc.read(..) If the server responds ok to starttls
#             tls negotiation needs to happen and all
#             communication is then over the SSL socket 

scc = ssl.wrap_socket(cc, ssl_version=ssl.PROTOCOL_SSLv23)
scc.send('auth login\r\n')
# scc.read(..)

scc.send(base64.b64encode('username')+'\r\n')
scc.send(base64.b64encode('password')+'\r\n')

# css.send(
#  mail from:
#  rcpt to:
#  data
#  etc

look at the AUTH LOGIN section of this page for info about the username/password encoding: http://www.samlogic.net/articles/smtp-commands-reference-auth.htm

After that the AUTH LOGIN command has been sent to the server, the server asks for username and password by sending BASE64 encoded text (questions) to the client. “VXNlcm5hbWU6” is the BASE64 encoded text for the word "Username" and “UGFzc3dvcmQ6” is the BASE64 encoded text for the word "Password" in the example above. The client sends username and password also using BASE64 encoding. "adlxdkej", in the example above, is a BASE64 encoded username and "lkujsefxlj" is a BASE64 encoded password.