c3lf-system-3/core/mail/protocol.py

import logging

import aiosmtplib
from asgiref.sync import sync_to_async
from channels.layers import get_channel_layer

from mail.models import Email, EventAddress
from notify_sessions.models import SystemEvent
from tickets.models import IssueThread, StateChange


def find_quoted_printable(s, marker):
    positions = [i for i in range(len(s)) if s.lower().startswith('=?utf-8?' + marker + '?', i)]
    for pos in positions:
        end = s.find('?=', pos + 10)
        if end == -1:
            continue
        yield pos, end + 3


def unescape_and_decode_quoted_printable(s):
    import quopri
    decoded = ''
    last_end = 0
    for start, end in find_quoted_printable(s, 'q'):
        decoded += s[last_end:start]
        decoded += quopri.decodestring(s[start + 10:end - 3]).decode('utf-8')
        last_end = end
    decoded += s[last_end:]
    return decoded


def unescape_and_decode_base64(s):
    import base64
    decoded = ''
    last_end = 0
    for start, end in find_quoted_printable(s, 'b'):
        decoded += s[last_end:start]
        decoded += base64.b64decode(s[start + 10:end - 3]).decode('utf-8')
        last_end = end
    decoded += s[last_end:]
    return decoded


def collect_references(issue_thread):
    mails = issue_thread.emails.order_by('timestamp')
    references = []
    for mail in mails:
        if mail.reference:
            references.append(mail.reference)
    return references


def make_reply(reply_email, references=None, event=None, issue_thread=None):
    from email.message import EmailMessage
    from core.settings import MAIL_DOMAIN
    event = event or "noreply"
    reply = EmailMessage()
    reply["From"] = reply_email.sender
    reply["To"] = reply_email.recipient
    reply["Subject"] = reply_email.subject
    reply["Reply-To"] = f"{event}+{issue_thread}@{MAIL_DOMAIN}"
    if reply_email.in_reply_to:
        reply["In-Reply-To"] = reply_email.in_reply_to
    if reply_email.reference:
        reply["Message-ID"] = reply_email.reference
    else:
        reply["Message-ID"] = reply_email.id + "@" + MAIL_DOMAIN
        reply_email.reference = reply["Message-ID"]
        reply_email.save()
    if references:
        reply["References"] = " ".join(references)

    reply.set_content(reply_email.body)

    return reply


async def send_smtp(message, log):
    log.info('Sending message to %s' % message['To'])
    await aiosmtplib.send(message, hostname="127.0.0.1", port=25, use_tls=False, start_tls=False)


def find_active_issue_thread(in_reply_to, subject=None):
    reply_to = Email.objects.filter(reference=in_reply_to)
    if reply_to.exists():
        return reply_to.first().issue_thread, False
    else:
        issue = IssueThread.objects.create(name=subject)
        return issue, True


def find_target_event(address):
    try:
        address_map = EventAddress.objects.get(address=address)
        if address_map.event:
            return address_map.event
    except EventAddress.DoesNotExist:
        pass
    return None

class LMTPHandler:
    async def handle_RCPT(self, server, session, envelope, address, rcpt_options):
        from core.settings import MAIL_DOMAIN
        address = address.lower()
        if not address.endswith('@' + MAIL_DOMAIN):
            return '550 not relaying to that domain'
        envelope.rcpt_tos.append(address)
        return '250 OK'

    async def handle_DATA(self, server, session, envelope):
        import email
        log = logging.getLogger('mail.log')
        log.setLevel(logging.DEBUG)
        log.info('Message from %s' % envelope.mail_from)
        log.info('Message for %s' % envelope.rcpt_tos)
        log.info('Message data:\n')

        try:
            parsed = email.message_from_bytes(envelope.content)
            body = ""
            if parsed.is_multipart():
                for part in parsed.walk():
                    ctype = part.get_content_type()
                    cdispo = str(part.get('Content-Disposition'))

                    # skip any text/plain (txt) attachments
                    if ctype == 'text/plain' and 'attachment' not in cdispo:
                        body = part.get_payload(decode=True)
                    else:
                        log.info("Attachment", ctype, cdispo)
            else:
                body = parsed.get_payload(decode=True)
            log.info(body)

            header_from = parsed.get('From')
            header_to = parsed.get('To')
            header_in_reply_to = parsed.get('In-Reply-To')
            header_message_id = parsed.get('Message-ID')

            if header_from != envelope.mail_from:
                log.warning("Header from does not match envelope from")
                log.info(f"Header from: {header_from}, envelope from: {envelope.mail_from}")

            if header_to != envelope.rcpt_tos[0]:
                log.warning("Header to does not match envelope to")
                log.info(f"Header to: {header_to}, envelope to: {envelope.rcpt_tos[0]}")

            recipient = envelope.rcpt_tos[0].lower()
            sender = envelope.mail_from
            subject = parsed.get('Subject')
            subject = unescape_and_decode_quoted_printable(subject)
            subject = unescape_and_decode_base64(subject)
            target_event = await sync_to_async(find_target_event)(recipient)

            active_issue_thread, new = await sync_to_async(find_active_issue_thread)(header_in_reply_to, subject)
            body_decoded = body.decode('utf-8')
            body_decoded = unescape_and_decode_quoted_printable(body_decoded)
            body_decoded = unescape_and_decode_base64(body_decoded)

            email = await sync_to_async(Email.objects.create)(
                sender=sender, recipient=recipient, body=body_decoded, subject=subject, reference=header_message_id,
                in_reply_to=header_in_reply_to, raw=envelope.content.decode('utf-8'), event=target_event,
                issue_thread=active_issue_thread)
            log.info(f"Created email {email.id}")
            systemevent = await sync_to_async(SystemEvent.objects.create)(type='email received', reference=email.id)
            log.info(f"Created system event {systemevent.id}")
            channel_layer = get_channel_layer()
            await channel_layer.group_send(
                'general', {"type": "generic.event", "name": "send_message_to_frontend", "event_id": systemevent.id,
                            "message": "email received"}
            )
            log.info(f"Sent message to frontend")
            if new:
                references = await sync_to_async(collect_references)(active_issue_thread)

                reply_email = await sync_to_async(Email.objects.create)(
                    sender=recipient, recipient=sender, body="Thank you for your message.", subject="Message received",
                    in_reply_to=header_message_id, event=target_event, issue_thread=active_issue_thread)
                await send_smtp(make_reply(reply_email, references), log)
                log.info("Sent auto reply")

            return '250 Message accepted for delivery'
        except Exception as e:
            log.error(e)
            return '550 Message rejected'