python aiosmtpd server with basic logging - python-3.x

Question

I've been made aware that aiosmtpd logs to the syslog. I'm using a Red Hat Linux distribution and can't find anything related to my SMTP server in the messages or maillog file. I'm trying to debug an issue with a device that can't connect to my SMTP server with basic authentication as I can't find any reason why the device is being rejected by my server. The only way I've been able to debug so far is by using the EHLO and MAIL handlers and printing a message when that stage of the connection is reached. Ideally, I'd like as much as possible to be logged out, like with smtplib that enables you to see each message between the client and server. Is it possible to do this or some basic logging at least and how do I do it if so? The code I'm using is:
import email
from email.header import decode_header
from email import message_from_bytes
from email.policy import default
from aiosmtpd.controller import Controller
from aiosmtpd.smtp import LoginPassword, AuthResult
import os
import json
import re
import sys
import time
import signal
import logging
from datetime import datetime
import configparser
##setting timezone
os.environ['TZ'] = "Europe/London"
time.tzset()
#wildlifeCameraHome = os.getenv('WILDLIFE_CAMERA_HOME')
wildlifeCameraHome = "/home/matthew_gale/smtp-server"
startupConfigURL = "{}/Config/Config.ini".format(wildlifeCameraHome)
validCameraList = "{}/Config/ValidCameraIDs.txt".format(wildlifeCameraHome)
ouboxBaseURL = "{}/outbox".format(wildlifeCameraHome)
spacer = "*"*100
# Get command line parameters
if len( sys.argv ) > 1 and str( sys.argv[1] ) == "DEBUG":
debugMode = True
else:
debugMode = False
if not debugMode:
logFileURL = "{}/Logging/EmailExtractorLog.out".format(wildlifeCameraHome)
sys.stdout = open(logFileURL, 'a', 1)
sys.stderr = sys.stdout
if os.environ.get('VA_LOG_LEVEL') is None:
envlevel = 3
else:
envlevel = int(os.environ.get('VA_LOG_LEVEL'))
def Lprint(logstring, loglevel):
detailedtimeStamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
if loglevel <= envlevel or debugMode:
print(detailedtimeStamp + ":" + logstring)
return True
else:
return None
def onExit( sig, func=None):
Lprint("*************Stopping program*****************",3)
controller.stop()
exit()
signal.signal(signal.SIGTERM, onExit)
# removes the spaces and replaces with _ so they're valid folder names
def clean(text):
return "".join(c if c.isalnum() else "_" for c in text)
#get the configs from the config file
config = configparser.ConfigParser()
config.read(startupConfigURL)
gmailConfig = config['EmailExtractor']
validEmail = gmailConfig['validSender']
# check at the end if there's any validation regarding who sends the email
with open(validCameraList, 'r', encoding='utf-8') as f:
validCameraIDs = f.readlines()
for rowNumber, content in enumerate(validCameraIDs):
validCameraIDs[rowNumber] = content.replace("\n","")
Lprint("Valid cameraIDs are",3)
print (validCameraIDs)
auth_db = {
b"TestCamera1#gmail.com": b"password1",
b"user2": b"password2",
b"TestCamera1": b"password1",
}
def authenticator_func(server, session, envelope, mechanism, auth_data):
# Simple auth - is only being used because of the reolink cam
assert isinstance(auth_data, LoginPassword)
username = auth_data.login
password = auth_data.password
if auth_db.get(username) == password:
return AuthResult(success=True)
else:
return AuthResult(success=False, handled=False)
def configure_logging():
file_handler = logging.FileHandler("aiosmtpd.log", "a")
stderr_handler = logging.StreamHandler(sys.stderr)
logger = logging.getLogger("mail.log")
fmt = "[%(asctime)s %(levelname)s] %(message)s"
datefmt = None
formatter = logging.Formatter(fmt, datefmt, "%")
stderr_handler.setFormatter(stderr_handler)
logger.addHandler(stderr_handler)
file_handler.setFormatter(file_handler)
logger.addHandler(file_handler)
logger.setLevel(logging.DEBUG)
class CustomHandler:
def handle_exception(self, error):
Lprint("exception occured",3)
print(error)
return '542 Internal Server Error'
async def handle_DATA(self, server, session, envelope):
peer = session.peer
data = envelope.content # type: bytes
msg = message_from_bytes(envelope.content, policy=default)
# decode the email subject
Lprint("Msg:{}".format(msg),3)
Lprint("Data:{}".format(data),3)
Lprint("All of the relevant data has been extracted from the email",3)
Lprint(spacer,3)
return '250 OK'
if __name__ == '__main__':
configure_logging()
handler = CustomHandler()
controller = Controller(handler, hostname='0.0.0.0', port=587, authenticator=authenticator_func, auth_required=True,auth_require_tls=False)
# Run the event loop in a separate thread.
controller.start()
#Confirmed that this is needed to keep the SMTP server running constantly
while True:
time.sleep(10)

Answer 1

If you search the aiosmtpd codebase for "logging.getLogger", you can find a few places where logging is being configured with Python's standard logging module.
In order to actually see these log messages, you need to configure the log level and add a log handler. Try calling the following "configure_logging" function early in your program. It will set up basic logging to stderr and to a file named "aiosmtpd.log". Complete example:
import logging
import sys
def configure_logging():
file_handler = logging.FileHandler("aiosmtpd.log", "a")
stderr_handler = logging.StreamHandler(sys.stderr)
logger = logging.getLogger("mail.log")
fmt = "[%(asctime)s %(levelname)s] %(message)s"
datefmt = None
formatter = logging.Formatter(fmt, datefmt, "%")
stderr_handler.setFormatter(formatter)
logger.addHandler(stderr_handler)
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
logger.setLevel(logging.DEBUG)
configure_logging()
# aiosmtpd example from https://stackoverflow.com/a/43904837/1570972
import aiosmtpd.controller
class CustomSMTPHandler:
async def handle_DATA(self, server, session, envelope):
print(len(envelope.content), repr(envelope.content[:50]))
return '250 OK'
handler = CustomSMTPHandler()
server = aiosmtpd.controller.Controller(handler, hostname="127.0.0.1")
server.start()
input("Server started. Press Return to quit.\n")
server.stop()
Running the above script in one terminal and then running swaks --server '127.0.0.1:8025' --to foo#example.com in another (the Swiss Army Knife for SMTP) to send a test email gives the following output on the terminal:
[2021-12-07 19:37:57,124 INFO] Available AUTH mechanisms: LOGIN(builtin) PLAIN(builtin)
[2021-12-07 19:37:57,124 INFO] Peer: ('127.0.0.1', 44126)
[2021-12-07 19:37:57,125 INFO] ('127.0.0.1', 44126) handling connection
[2021-12-07 19:37:57,125 DEBUG] ('127.0.0.1', 44126) << b'220 alcyone.localdomain Python SMTP 1.4.2'
Server started. Press Return to quit.
[2021-12-07 19:37:57,126 INFO] ('127.0.0.1', 44126) EOF received
[2021-12-07 19:37:57,126 INFO] ('127.0.0.1', 44126) Connection lost during _handle_client()
[2021-12-07 19:37:57,126 INFO] ('127.0.0.1', 44126) connection lost
[2021-12-07 19:38:02,012 INFO] Available AUTH mechanisms: LOGIN(builtin) PLAIN(builtin)
[2021-12-07 19:38:02,012 INFO] Peer: ('127.0.0.1', 44128)
[2021-12-07 19:38:02,013 INFO] ('127.0.0.1', 44128) handling connection
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'220 alcyone.localdomain Python SMTP 1.4.2'
[2021-12-07 19:38:02,013 DEBUG] _handle_client readline: b'EHLO alcyone.localdomain\r\n'
[2021-12-07 19:38:02,013 INFO] ('127.0.0.1', 44128) >> b'EHLO alcyone.localdomain'
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'250-alcyone.localdomain'
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'250-SIZE 33554432'
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'250-8BITMIME'
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'250-SMTPUTF8'
[2021-12-07 19:38:02,013 DEBUG] ('127.0.0.1', 44128) << b'250 HELP'
[2021-12-07 19:38:02,014 DEBUG] _handle_client readline: b'MAIL FROM:<rav#alcyone.localdomain>\r\n'
[2021-12-07 19:38:02,014 INFO] ('127.0.0.1', 44128) >> b'MAIL FROM:<rav#alcyone.localdomain>'
[2021-12-07 19:38:02,014 INFO] ('127.0.0.1', 44128) sender: rav#alcyone.localdomain
[2021-12-07 19:38:02,014 DEBUG] ('127.0.0.1', 44128) << b'250 OK'
[2021-12-07 19:38:02,014 DEBUG] _handle_client readline: b'RCPT TO:<foo#example.com>\r\n'
[2021-12-07 19:38:02,014 INFO] ('127.0.0.1', 44128) >> b'RCPT TO:<foo#example.com>'
[2021-12-07 19:38:02,014 INFO] ('127.0.0.1', 44128) recip: foo#example.com
[2021-12-07 19:38:02,014 DEBUG] ('127.0.0.1', 44128) << b'250 OK'
[2021-12-07 19:38:02,014 DEBUG] _handle_client readline: b'DATA\r\n'
[2021-12-07 19:38:02,014 INFO] ('127.0.0.1', 44128) >> b'DATA'
[2021-12-07 19:38:02,015 DEBUG] ('127.0.0.1', 44128) << b'354 End data with <CR><LF>.<CR><LF>'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'Date: Tue, 07 Dec 2021 19:38:02 +0100\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'To: foo#example.com\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'From: rav#alcyone.localdomain\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'Subject: test Tue, 07 Dec 2021 19:38:02 +0100\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'Message-Id: <20211207193802.024948#alcyone.localdomain>\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'X-Mailer: swaks vDEVRELEASE jetmore.org/john/code/swaks/\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'This is a test mailing\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'\r\n'
[2021-12-07 19:38:02,015 DEBUG] DATA readline: b'.\r\n'
283 b'Date: Tue, 07 Dec 2021 19:38:02 +0100\r\nTo: foo#exa'
[2021-12-07 19:38:02,015 DEBUG] ('127.0.0.1', 44128) << b'250 OK'
[2021-12-07 19:38:02,015 DEBUG] _handle_client readline: b'QUIT\r\n'
[2021-12-07 19:38:02,015 INFO] ('127.0.0.1', 44128) >> b'QUIT'
[2021-12-07 19:38:02,015 DEBUG] ('127.0.0.1', 44128) << b'221 Bye'
[2021-12-07 19:38:02,016 INFO] ('127.0.0.1', 44128) connection lost
[2021-12-07 19:38:02,016 INFO] ('127.0.0.1', 44128) Connection lost during _handle_client()