8.0 KiB
Mail operations in Qubes OS.
Table of Contents
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:
- Receive mail via the
mail-fetcherand transfer mail tomail-reader. - Read and compose mail from
mail-readerand transfer tomail-sender. - Send queued mails from
mail-senderto 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