qusal/salt/mail

mail

Mail operations in Qubes OS.

Table of Contents

• Description
• Security
• Installation
• Usage
  • Fetcher
    • fdm Configuration
    • mpop Configuration
    • OfflineIMAP Configuration
    • Send Inbox to Reader Qube
  • Reader
    • Mutt Configuration
    • Send Queue to Sender Qube
  • Sender
    • msmtp Configuration
    • Send emails to SMTP server
• Credits

Description

Create a mail fetcher qube named "mail-fetcher", a mail reader qube names "mail-reader" and a mail sender qube named "mail-sender".

The online "mail-fetcher" qube will fetch messages with POP3. After being fetched, you can copy them to the offline "mail-reader" qube, where you will be reading emails. After composing a message, the "mail-reader" qube will save the messages to a queue, which can be forwarded to the online "mail-sender" qube. You can review messages to be sent from the "mail-sender" qube and them send them via SMTP.

By default, the protocols used required SSL, POP3 on port 995, IMAP on port 995 and SMTP on port 587. You can always override any configuration via included files.

This formula is based on Unman's SplitMutt guide, using POP3 and/or IMAP to get mail, not considering SSH access to the mail server. We are using qfile-agent and not Rsync to synchronize mails between qubes to avoid a higher attack surface, but Rsync may be considered in the future in case qfile-agent causes problems.

Security

Mail is insecure per nature and users depend on archaic Unix tools that receive little to no maintenance.

The qubes connected to the internet mail-fetcher and mail-sender hold the account password to connect to the remote servers. If any of those are compromised, your mail account can also be. Network firewall can help, to some extent, if you consider the attacker doesn't have an account on the same mail server you have, or sends a message from you mail account to an attacker controlled mail and then delete from your sent messages.

The reader qube mail-reader also has a high attack surface. Although offline, it can access PGP keys via split-gpg2 and also read all your mails, in case an especially crafted message exploits the parsing of the message. We are using Mutt, but if you know how to choose local folders in Mozilla Thunderbird, you can adapt the formula. Neither MUA have great security records, but Mutt has less and is more minimal. The reader should be a secure mail client, but there are none. Mutt will open text/html and text/plain files, while every other type of file is opened in a disposable qube. See reader for offline disposables that can open some kinds of files.

If you want to read the mail in the sender qube mail-sender, you may want to do this before sending to the mail server, you should open the file in a disposable to avoid a parsing bug in the editor to extract information such as the password from the sender qube. This method doesn't prevent all kinds of exploitation, as msmtp still needs to parse the mail to be sent.

Installation

• Top:

sudo qubesctl top.enable mail reader
sudo qubesctl --targets=tpl-mail-fetcher,tpl-mail-reader,tpl-mail-sender,dvm-mail-fetcher,mail-reader,dvm-mail-sender,tpl-reader state.apply
sudo qubesctl top.disable mail reader
sudo qubesctl state.apply mail.appmenus,reader.appmenus

• State:

sudo qubesctl state.apply mail.create
sudo qubesctl --skip-dom0 --targets=tpl-reader state.apply reader.install
sudo qubesctl --skip-dom0 --targets=tpl-mail-fetcher state.apply mail.install-fetcher
sudo qubesctl --skip-dom0 --targets=tpl-mail-reader state.apply mail.install-reader
sudo qubesctl --skip-dom0 --targets=tpl-mail-sender state.apply mail.install-sender
sudo qubesctl --skip-dom0 --targets=dvm-mail-fetcher state.apply mail.configure-fetcher
sudo qubesctl --skip-dom0 --targets=mail-reader state.apply mail.configure-reader
sudo qubesctl --skip-dom0 --targets=dvm-mail-sender state.apply mail.configure-sender
sudo qubesctl state.apply mail.appmenus,reader.appmenus

Usage

You will use local files to override the ones provided by this package. Few options must be set. Do not change the directories in the configuration files, they need to stay the same.

You should firewall the mail-fetcher and mail-sender to the POP3 server or/and IMAP server and SMTP server, respectively.

Steps overview:

1. Receive mail via the mail-fetcher and transfer mail to mail-reader.
2. Read and compose mail from mail-reader and transfer to mail-sender.
3. Send queued mails from mail-sender to remote mail server.

Fetcher

The fetcher fetches e-mails with fdm or mpop via the POP3 protocol or even offlineimap via the IMAP protocol, you only need to choose one program for this task, depending on your needs.

The configuration must be done in dvm-mail-fetcher, while the fetching of mails will be done in disp-mail-fetcher.

fdm Configuration

Copy example configuration file to where the program can read automatically:

cp ~/.fdm.conf.example ~/.fdm.conf

Edit the configuration according to your needs:

editor ~/.fdm.conf

Check the connection is working:

fdm -kv poll

Fetch mail:

fdm -kv fetch

If the fetch was successful, enable the fetch scheduler:

systemctl --user enable fdm.timer
systemctl --user start  fdm.timer

mpop Configuration

Copy ~/.mpoprc.example to ~/.mpoprc and edit the configuration according to your needs.

Copy example configuration file to where the program can read automatically:

cp ~/.mporc.example ~/.mpoprc

Edit the configuration according to your needs:

editor ~/.mpoprc

Check the connection is working:

mpop --debug --auth-only

Fetch mail:

mpop

If the fetch was successful, enable the fetch scheduler:

systemctl --user enable mpop.timer
systemctl --user start  mpop.timer

OfflineIMAP Configuration

TODO: difficult to exemplify as the folders are user and provider specific.

Send Inbox to Reader Qube

Send the inbox to the reader:

qusal-send-inbox

Reader

The reader renders e-mails with mutt.

The configuration as well as the reading and composing of mails are done in mail-reader.

Mutt Configuration

You must place your credentials in ~/.muttrc-credentials.local, definitions in this file will be used by scripts sourced at a later time.

You should define aliases only in ~/.muttrc-aliases.local, as the aliases file can be edited by Mutt.

You can define extra options in ~/.muttrc.local, as this is the last file to be sourced, it can override previous options.

If you want to have your e-mail signature (not PGP) at the end of every mail you send, place it in ~/.signature.

Samples for the aforementioned files can be found at ~/.config/mutt/sample.

Send Queue to Sender Qube

Send the queued mail to the sender:

qusal-send-mail

Sender

The sender sends e-mails with msmtp via the SMTP protocol.

The configuration must be done in dvm-mail-sender, while the sending of mails are done in disp-mail-sender.

msmtp Configuration

Copy example configuration file to where the program can read automatically:

cp ~/.msmtprc.example ~/.msmtprc

Edit the configuration according to your needs:

editor ~/.msmtprc

Test the connection to the SMTP server:

msmtp --serverinfo

Send emails to SMTP server

List the queued mails:

msmtp-queue -d

Send selected mails from the queue to the SMTP server:

msmtp-queue -R

Credits

• Unman