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Replace To or CC header when forward/reply

This commit is contained in:
Son NK 2020-03-28 19:16:55 +01:00
parent 5b9f3c2763
commit aa3a13c3ca
2 changed files with 151 additions and 28 deletions
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32
app/email_utils.py
View File

@ -3,7 +3,7 @@ from email.message import Message
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.utils import make_msgid, formatdate
from email.utils import make_msgid, formatdate, parseaddr, formataddr
from smtplib import SMTP
from typing import Optional
@ -363,3 +363,33 @@ def get_orig_message_from_bounce(msg: Message) -> Message:
# 7th is original message
if i == 7:
return part
def new_addr(old_addr, new_email) -> str:
"""replace First Last <first@example.com> by
first@example.com by SimpleLogin <new_email>
`new_email` is a special reply address
"""
name, old_email = parseaddr(old_addr)
new_name = f"{old_email} via SimpleLogin"
new_addr = formataddr((new_name, new_email)).strip()
return new_addr.strip()
def get_addrs_from_header(msg: Message, header) -> [str]:
"""Get all addresses contained in `header`
Used for To or CC header.
"""
ret = []
header_content = msg.get_all(header)
if not header_content:
return ret
for addrs in header_content:
for addr in addrs.split(","):
ret.append(addr.strip())
# do not return empty string
return [r for r in ret if r]

147
email_handler.py
View File

@ -38,7 +38,7 @@ from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.parser import Parser
from email.policy import SMTPUTF8
from email.utils import parseaddr, formataddr
from email.utils import parseaddr, formataddr, getaddresses
from io import BytesIO
from smtplib import SMTP
from typing import Optional
@ -65,6 +65,8 @@ from app.email_utils import (
render,
get_orig_message_from_bounce,
delete_all_headers_except,
new_addr,
get_addrs_from_header,
)
from app.extensions import db
from app.log import LOG
@ -240,6 +242,104 @@ def get_or_create_contact(website_from_header: str, alias: Alias) -> Contact:
return contact
def replace_header_when_forward(msg: Message, alias: Alias, header: str):
"""
Replace CC or To header by Reply emails in forward phase
"""
addrs = get_addrs_from_header(msg, header)
# Nothing to do
if not addrs:
return
new_addrs: [str] = []
need_replace = False
for addr in addrs:
name, email = parseaddr(addr)
# no transformation when alias is already in the header
if email == alias.email:
new_addrs.append(addr)
continue
contact = Contact.get_by(alias_id=alias.id, website_email=email)
if contact:
# update the website_from if needed
if contact.website_from != addr:
LOG.d("Update website_from for %s to %s", contact, addr)
contact.website_from = addr
db.session.commit()
else:
LOG.debug(
"create contact for alias %s and email %s, header %s",
alias,
email,
header,
)
reply_email = generate_reply_email()
contact = Contact.create(
user_id=alias.user_id,
alias_id=alias.id,
website_email=email,
website_from=addr,
reply_email=reply_email,
is_cc=header.lower() == "cc",
)
db.session.commit()
new_addrs.append(new_addr(contact.website_from, contact.reply_email))
need_replace = True
if need_replace:
new_header = ",".join(new_addrs)
LOG.d("Replace %s header, old: %s, new: %s", header, msg[header], new_header)
add_or_replace_header(msg, header, new_header)
else:
LOG.d("No need to replace %s header", header)
def replace_header_when_reply(msg: Message, alias: Alias, header: str):
"""
Replace CC or To Reply emails by original emails
"""
addrs = get_addrs_from_header(msg, header)
# Nothing to do
if not addrs:
return
new_addrs: [str] = []
need_replace = False
for addr in addrs:
name, email = parseaddr(addr)
# no transformation when alias is already in the header
if email == alias.email:
new_addrs.append(addr)
continue
contact = Contact.get_by(reply_email=email)
if not contact:
LOG.warning("CC email in reply phase %s must be reply emails", email)
# still keep this email in header
new_addrs.append(addr)
continue
new_addrs.append(contact.website_from or contact.website_email)
need_replace = True
if need_replace:
new_header = ",".join(new_addrs)
LOG.d("Replace %s header, old: %s, new: %s", header, msg[header], new_header)
add_or_replace_header(msg, header, new_header)
else:
LOG.d("No need to replace %s header", header)
def generate_reply_email():
# generate a reply_email, make sure it is unique
# not use while loop to avoid infinite loop
@ -254,7 +354,7 @@ def generate_reply_email():
def should_append_alias(msg: Message, address: str):
"""whether an alias should be appened to TO header in message"""
"""whether an alias should be appended to TO header in message"""
if msg["To"] and address in msg["To"]:
return False
@ -337,15 +437,13 @@ def handle_forward(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
# replace the email part in from: header
contact_from_header = msg["From"]
contact_name, contact_email = parseaddr(contact_from_header)
new_contact_name = f"{contact_email} via SimpleLogin"
new_from_header = formataddr((new_contact_name, contact.reply_email)).strip()
new_from_header = new_addr(contact_from_header, contact.reply_email)
add_or_replace_header(msg, "From", new_from_header)
LOG.d(
"new from header:%s, contact_name %s, contact_email %s",
new_from_header,
contact_name,
contact_email,
)
LOG.d("new_from_header:%s, old header %s", new_from_header, contact_from_header)
# replace CC & To emails by reply-email for all emails that are not alias
replace_header_when_forward(msg, alias, "Cc")
replace_header_when_forward(msg, alias, "To")
# append alias into the TO header if it's not present in To or CC
if should_append_alias(msg, alias.email):
@ -405,15 +503,15 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
LOG.warning(f"No such forward-email with {reply_email} as reply-email")
return "550 SL wrong reply email"
alias = contact.alias
address: str = contact.alias.email
alias_domain = address[address.find("@") + 1 :]
# alias must end with one of the ALIAS_DOMAINS or custom-domain
if not email_belongs_to_alias_domains(address):
if not email_belongs_to_alias_domains(alias.email):
if not CustomDomain.get_by(domain=alias_domain):
return "550 SL alias unknown by SimpleLogin"
alias = contact.alias
user = alias.user
mailbox_email = alias.mailbox_email()
@ -424,7 +522,7 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
if envelope.mail_from == "<>":
LOG.error(
"Bounce when sending to alias %s from %s, user %s",
address,
alias,
contact.website_from,
alias.user,
)
@ -443,21 +541,20 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
reply_email,
)
user = alias.user
send_email(
mailbox_email,
f"Reply from your alias {address} only works from your mailbox",
f"Reply from your alias {alias.email} only works from your mailbox",
render(
"transactional/reply-must-use-personal-email.txt",
name=user.name,
alias=address,
alias=alias.email,
sender=envelope.mail_from,
mailbox_email=mailbox_email,
),
render(
"transactional/reply-must-use-personal-email.html",
name=user.name,
alias=address,
alias=alias.email,
sender=envelope.mail_from,
mailbox_email=mailbox_email,
),
@ -479,8 +576,8 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
delete_header(msg, "DKIM-Signature")
# the email comes from alias
add_or_replace_header(msg, "From", address)
# make the email comes from alias
add_or_replace_header(msg, "From", alias.email)
# some email providers like ProtonMail adds automatically the Reply-To field
# make sure to delete it
@ -489,19 +586,15 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
# remove sender header if present as this could reveal user real email
delete_header(msg, "Sender")
add_or_replace_header(msg, "To", contact.website_email)
# add List-Unsubscribe header
unsubscribe_link = f"{URL}/dashboard/unsubscribe/{contact.alias_id}"
add_or_replace_header(msg, "List-Unsubscribe", f"<{unsubscribe_link}>")
add_or_replace_header(msg, "List-Unsubscribe-Post", "List-Unsubscribe=One-Click")
replace_header_when_reply(msg, alias, "To")
replace_header_when_reply(msg, alias, "Cc")
# Received-SPF is injected by postfix-policyd-spf-python can reveal user original email
delete_header(msg, "Received-SPF")
LOG.d(
"send email from %s to %s, mail_options:%s,rcpt_options:%s",
address,
alias.email,
contact.website_email,
envelope.mail_options,
envelope.rcpt_options,
@ -517,7 +610,7 @@ def handle_reply(envelope, smtp: SMTP, msg: Message, rcpt_to: str) -> str:
msg_raw = msg.as_string().encode()
smtp.sendmail(
address,
alias.email,
contact.website_email,
msg_raw,
envelope.mail_options,