Skip to content
Snippets Groups Projects
Select Git revision
  • master default protected
  • tpa-rfc-80-merge-tor-and-tails-support-policies
  • puppet-merge-costs
  • rfc-77-improv
  • tails-merge-admin-mailing-lists
  • mkdocs
  • new-blog-doc
7 results
Blame Permalink
submission.md 26.58 KiB 
title: Email submission services

Email submission services consist of a server that accepts email using authenticated SMTP for LDAP users of the torproject.org domain.

Tutorial

In general, you can configure your email client with the following SMTP settings:

  • Server name: submission.torproject.org
  • Port: 587
  • Connection security: STARTTLS
  • Authentication method: Normal password
  • User Name: your LDAP username without the @torproject.org part, e.g. in my case it is anarcat
  • Password: LDAP email password set on the LDAP dashboard

TLS connection security, on port 465 is supported and encouraged.

Setting an email password

To use the email submission service, you first need to set a "mail password". For this, you need to update your account in LDAP:

  1. head towards https://db.torproject.org/update.cgi
  2. login with your LDAP credentials (here's how to do a password reset if you lost that)
  3. be careful to hit the "Update my info" button (not the "Full search")
  4. enter a new, strong password in the Change mail password: field (and save it in your password manager)
  5. hit the "Update..." button

What this will do is set a "mail password" in your LDAP account. Within a few minutes, this should propagate to the submission server, which will then be available to relay your mail to the world. Then the next step is to configure your email client, below.

Thunderbird configuration

In Thunderbird, you will need to add a new SMTP account in "Account settings", "Outgoing Server (SMTP)". Then click add and fill the form with:

  • Server name: submission.torproject.org
  • Port: 587
  • Connection security: STARTTLS
  • Authentication method: Normal password
  • User Name: (your LDAP username, e.g. in my case it is anarcat, without the @torproject.org part)

TLS connection security, on port 465 is supported and encouraged.

Then you can set that account as the default by hitting the "Set default" button, if only your torproject.org identity is configured on the server.

If not, you need to pick your torproject.org account from the "Account settings" page, then at the bottom pick the tor SMTP server you have just configured.

Then on first email send you will be prompted for your email password. You should NOT get a certificate warning, a real cert (signed by Let's Encrypt) should be presented by the server.

Apple Mail configuration

  1. Click On "Account Information"
  • User Name: (your LDAP username, e.g. in my case it is anarcat, without the @torproject.org part)
  • Password: the correct one.
  • Outgoing Mail Server (SMTP): submission.torproject.org

  1. Make sure that your SMTP server is set to submission.torproject.org

    Note for existing mail users: You will need to select “Add Server” from the SMTP pull-down menu.

  2. If it is, select “Server Settings”

  • For Server Port, put 587
  • Select Use Secure Socket Layer (SSL)
  • Set Authentication to Password
  • Now, enter your correct user name and your correct password.
  • Select OK.

TLS connection security, on port 465 is supported and encouraged.

Gmail configuration

NOTE: This section explains how to reconfigure a gmail account that is already configured to use a torproject.org address. If you need to add a new address from scratch, the process will be a little different.

  1. Click on "Settings". (That should be the big gear icon towards thetop right of your window.)

  2. A "quick settings" menu should open. Click on the "See all settings" button at the top of that menu.

  3. This will take you to a "Settings" page. Click on the "Accounts and Import" tab at the top of the page.

  4. Under "Send mail as", find the address for yourname@torproject.org, and lick the "edit info" link to the right of that account. (If the address isn't there, then your gmail account isn't set up to use your TPO account. You'll need to click "Add another email address" instead, and the process below will be slightly different.)

  5. A new "Edit email address" popup should open. Click "Next step" on it.

  6. Finally, you'll be at a window that says "Edit email address". Fill it out like this:

  • Select "Send through torproject.org SMTP servers".
  • Set "SMTP Server:" to "submission.torproject.org"
  • Set "Port:" to 587.
  • Set "Username:" to your username (without "@torproject.org").
  • Set "Password:" to the email submission password that you configured.
  • Select "Use TLS", not "Use SSL".

Double-check everything, then click "Save Changes". Gmail will try authenticating to the SMTP server; if it's successful, then the popup window will close and your account will be updated.

How-to

Glossary

  • SMTP: Simple Mail Transfer Protocol. The email protocol spoken between servers to deliver email. Consists of two standards, RFC821 and RFC5321 which defined SMTP extensions, also known as ESMTP.
  • MTA: Mail Transport Agent. A generic SMTP server. Eugeni is such a server.
  • MUA: Mail User Agent. An "email client", a program used to receive, manage and send email for users.
  • MSA : Mail Submission Agent. An SMTP server specifically designed to only receive email.
  • MDA: Mail Delivery Agent. The email service actually writing the email to the user's mailbox. Out of scope.

This document describes the implementation of a MSA, although the service will most likely also include a MTA functionality in that it will actually deliver emails to targets.

More obscure clients configuration

This section regroups email client configurations that might be a little more exotic than commonly used software. The rule of thumb here is that if there's a GUI to configure things, then it's not obscure.

Also, if you know what an MTA is and are passionate about standards, you're in the obscure category, and are welcomed to this dark corner of the internet.

msmtp configuration

"msmtp is an SMTP client" which "transmits a mail to an SMTP server which takes care of further delivery". It is particularly interesting because it supports SOCKS proxies, so you can use it to send email over Tor.

This is how dgoulet configured his client:

# Defaults for all accounts.
defaults
auth on
protocol smtp
tls on
port 587

# Account: dgoulet@torproject.org
account torproject
host submission.torproject.org
from dgoulet@torproject.org
user dgoulet
passwordeval pass mail/dgoulet@torproject.org

Postfix client configuration

If you run Postfix as your local Mail Transport Agent (MTA), you'll need to do something special to route your emails through the submission server.

First, set the following configuration in main.cf, by running the following commands:

postconf -e smtp_sasl_auth_enable=yes
postconf -e smtp_sasl_password_maps=hash:/etc/postfix/sasl/passwd
postconf -e smtp_sasl_security_options=
postconf -e relayhost=submission.torproject.org:587
postconf -e smtp_tls_security_level=encrypt
postfix reload

The /etc/postfix/sasl/passwd file holds hostname user:pass configurations, one per line:

touch /etc/postfix/sasl/passwd
chown root:root /etc/postfix/sasl/passwd && chmod 600 /etc/postfix/sasl/passwd
echo "submission.torproject.org user:pass" >> /etc/postfix/sasl/passwd

Then rehash that map:

postmap /etc/postfix/sasl/passwd

Note that this method stores your plain text password on disk. Make sure permissions on the file are limited and that you use full disk encryption.

may can be used as a security_level if we are going to send mail to other hosts which may not support security, but make sure that mails are encrypted when talking to the relayhost, for example through a smtp_tls_policy_maps.

If you want to use Tor's submission server only for mail sent from a @torproject.org address, you'll need an extra step. This should be in main.cf:

postconf -e smtp_sender_dependent_authentication=yes
postconf -e sender_dependent_relayhost_maps=hash:/etc/postfix/sender_relay

Then in the /etc/postfix/sender_relay file:

# Per-sender provider; see also /etc/postfix/sasl_passwd.
anarcat@torproject.org               [submission.torproject.org]

Then rehash that map as well:

postmap /etc/postfix/sender_relay

Make sure you do not change the relahost (above), or reset it to its previous value. If you have changed your default_transport, you'll also need a sender_dependent_default_transport_maps as well:

postconf -e sender_dependent_transport_maps=hash:/etc/postfix/sender_transport

With /etc/postfix/sender_transport looking like:

anarcat@torproject.org               smtp:

For debugging, you can make SMTP client sessions verbose in Postfix:

smtp      unix  -       -       -       -       -       smtp -v

smtp_sasl_mechanism_filter is also very handy for debugging. For example, you can try to force the authentication mechanism to cram-md5 this way.

Pager playbook

No pager playbook has been built yet. See the Monitoring and testing section below for ideas on how to debug things.

Disaster recovery

N/A. The server should be rebuildable from scratch using the Puppet directive and does not have long-term user data. All user data is stored in DNS or LDAP.

If email delivery starts failing, users are encouraged to go back to the email providers they were using before this service was deployed.

Reference

Installation

To setup a new mail server, create a machine with the email::submission role in Puppet. Ideally, it should be on a network with a good IP reputation.

In letsencrypt.git, add an entry for that host's specific TLS certificate. For example, the submit-01.torproject.org server has a line like this:

submit-01.torproject.org submit.torproject.org

Those domains are glued together in DNS with:

submission              IN      CNAME   submit-01
_submission._tcp        IN      SRV     0 1 587 submission

This implies there is only one submission.torproject.org, because one cannot have multiple CNAME records, of course. But it should make replacing the server transparent for end-users.

The latter SRV record is actually specified in RFC6186, but may not be sufficient for all automatic configuration. We do not go deeper into auto-discovery, because that typically implies IMAP servers and so on. But if we would, we could consider using this software which tries to support all of them (e.g. Microsoft, Mozilla, Apple). For now, we'll only stick with the SRV record.

SLA

There is no SLA specific to this service, but mail delivery is generally considered to be high priority. Complaints about delivery failure should be filed as issues in our ticket tracker and addressed.

Design

The submission email service allows users to submit mail as if they were on a torproject.org machine. Concretely, it is a Postfix server which relays email to anywhere once SASL authentication is passed.

Most of the code is glue code in Puppet, along with a small set of patches to ud-ldap which were sent (and mostly accepted) upstream.

Authentication

SASL authentication is delegated to a dummy Dovecot server which is only used for authentication (i.e. it doesn't provide IMAP or POP storage). Username/password pairs are deployed by ud-ldap into /etc/dovecot/private/mail-passwords.

The LDAP server stores those passwords in a mailPassword field and the web interface is used to modify those passwords. Passwords are (currently) encrypted with a salted MD5 hash because of compatibility problems between the Perl/ud-ldap implementation and Dovecot which haven't been resolved yet.

The "submission" port (587) is used in the documentation by default because it is typically less blocked by ISP firewalls than the "smtps" port (465), but both are supported. The TLS server is authenticated using the regular Let's Encrypt CA (see TLS documentation).

Issues

There is no issue tracker specifically for this project, File or search for issues in the team issue tracker.

When reporting email issues, do mind the reporting email problems documentation.

Project was coordinated and launched in ticket #30608.

Maintainer, users, and upstream

This service is mostly written as a set of Puppet manifests. It was built by anarcat, and is maintained by TPA. There is no upstream.

It depends on patches on userdir-ldap that were partially merged in the upstream, see LDAP docs for details.

Monitoring and testing

The Postfix server is monitored by Nagios, as with all servers in the publicmail group. This only checks that the SMTP port is open. We do not have end to end delivery monitoring just yet, that is part of the improve mail services milestone, specifically issue 40494.

To test delivery manually, make sure you have an emailPassword set (e.g. through update.cgi). Then you should be able to use the swaks to test delivery.

This will try to relay an email through server example.net to the example.com domain using TLS over the submission port (587) with user name anarcat and a prompted password (-ap -pp).

swaks -f anarcat@torproject.org -t anarcat@torproject.org -s submission.torproject.org -tls -p 587 -au anarcat -ap -pp

To set a new password by hand in LDAP, you can use doveadm to generate a salted password. This will create a bcrypt password, for example:

doveadm pw -s BLF-CRYPT

Then copy-paste the output (minus the {} prefix) into the mailPassword field in LDAP (if you want to bypass the web interface) or the /etc/dovecot/private/mail-passwords file on the submission server (if you want to bypass ud-replicate altogether, note that the change might be overwritten fairly quickly). Note that other schemes can be used as well.

Logs and metrics

The submission server is monitored like other mail servers that have mail_processing enabled, which is that it has the mtail exporter (profile::prometheus::postfix_mtail_exporter). The Grafana dashboard should provide shiny graphs.

Mail logs are in /var/log/mail.log and probably systemd journals. They contain PII like IP addresses and usernames and are regularly purged. Mails are scanned by fail2ban to ban IP addresses trying to bruteforce account passwords.

Backups

No special backup of this service is required.

Other documentation

This service was setup following some or all of those documents:

Discussion

Overview

The idea is to create a new server to deal with delivery problems torproject.org email users are currently seeing. While they can receive email through their user@torproject.org forwards without too much problem, their emails often get dropped to the floor when sending from that email address.

It is suspected that users are having those problems because the originating servers are not in the torproject.org domain. The hope is that setting up a new server inside that domain would help with delivery. There's anecdotal evidence (see this comment for example) that delivery emails from existing servers (over SSH to iranicum, in that example) improves reliability of email delivery significantly.

This project came out of ticket #30608, which has the launch checklist.

Note: this article has a good overview of deliverability issues faced by autonomous providers, which we already face on eugeni, but might be accentuated by this project.

Goals

Must have

  • basic compatibility with major clients (Thunderbird, Mail.app, Outlook, Gmail?)
  • delivery over secure (TLS + password) SMTP
  • credentials stored in LDAP

Nice to have

  • automatic client configuration
  • improved delivery over current federated configuration
  • delivery reliability monitoring with major providers (e.g. hotmail, gmail, yahoo)
  • pretty graphs
  • formalized SSH-key delivery to avoid storing cleartext passwords on clients

Non-Goals

  • 100%, infaillable, universal delivery to all providers (ie. emails will still be lost)
  • mailbox management (ie. no incoming email, IMAP, POP, etc)
  • spam filtering (ie. we won't check outgoing emails)
  • no DKIM, SPF, DMARC, or ARC for now, although maybe a "null" SPF record if it helps with delivery

Approvals required

Approved by vegas, requested by network team, agreed with TPA at the Stockholm meeting.

Proposed Solution

The proposed design is to setup a new email server in the howto/ganeti cluster (currently gnt-fsn) with the user list synchronized from LDAP, using a new password field (named mailPassword). The access would therefore be granted only to LDAP users, and LDAP accounts would be created as needed. In the short term, LDAP can be used to modify that password but in the mid-term, it would be modifiable through the web interface like the webPassword or rtcPassword fields.

Current inventory

  • active LDAP accounts: 91
  • non-LDAP forwards (to real people): 24
  • role forwards (to other @torproject.org emails): 76

Forward targets:

  • riseup.net: 30
  • gmail.com: 21
  • other: 93 (only 4 domains have more than one forward)

Delivery rate: SMTP, on eugeni, is around 0.5qps, with a max of 8qps in the last 7 days (2019-06-06). But that includes mailing lists as well. During that period, around 27000 emails were delivered to @torproject.org aliases.

Cost

Labor and gnt-fsn VM costs. To be detailed.

Below is an evaluation of the various Alternatives that were considered.

External hosting cost evaluation

  • Google: 8$/mth/account? (to be verified?)
  • riseup.net: anarcat requested price quotation
  • koumbit.org: default pricing: 100/year on shared hosting and 50GB total, possibly no spam filter. 1TB disk: 500/year. disk encryption would need to be implemented, quoted 2000-4000$ setup fee to implement it in the AlternC opensource control panel.
  • self-hosting: ~4000-500EUR setup, 5000EUR-7500EUR/year, liberal estimate (will probably be less)
  • mailfence 1750 setup cost and 2.5 euros per user/year

Note that the self-hosting cost evaluation is for the fully-fledged service. Option 2, above, of relaying email, has overall negligible costs although that theory has been questioned by members of the sysadmin team.

Internal hosting cost evaluation

This is a back-of-the-napkin calculation of what it would cost to host actual email services at TPA infrastructure itself. We consider this to be a “liberal” estimate, ie. costs would probably be less and time estimates have been padded (doubled) to cover for errors.

Assumptions:

  • each mailbox is on average, a maximum of 10GB
  • 100 mailboxes maximum at first (so 1TB of storage required)
  • LUKS full disk encryption
  • IMAP and basic webmail (Roundcube or Rainloop)
  • “Trees” mailbox encryption out of scope for now

Hardware:

  • Hetzner px62nvme 2x1TB RAID-1 64GB RAM 75EUR/mth, 900EUR/yr
  • Hetzner px92 2x1TB SSD RAID-1 128GB RAM 115EUR/mth, 1380EUR/yr
  • Total hardware: 2280EUR/yr, ~200EUR setup fee

This assumes hosting the server on a dedicated server at Hetzner. It might be possible (and more reliable) to ensure further cost savings by hosting it on our shared virtualized infrastructure. Calculations for this haven’t been performed by the team, but I would guess we might save around 25 to 50% of the above costs, depending on the actual demand and occupancy on the mail servers.

Staff:

  • LDAP password segregation: 4 hours*
  • Dovecot deployment and LDAP integration: 8 hours
  • Dovecot storage optimization: 8 hours
  • Postfix mail delivery integration: 8 hours
  • Spam filter deployment: 8 hours
  • 100% cost overrun estimate: 36 hours
  • Total setup costs: 72 hours @ 50EUR/hr: 3600EUR one time

This is the most imprecise evaluation. Most email systems have been built incrementally. The biggest unknown is the extra labor associated with running the IMAP server and spam filter. A few hypothesis:

  • 1 hour a week: 52 hours @ 50EUR/hr: 2600EUR/yr
  • 2 hours a week: 5200EUR/yr

I would be surprised if the extra work goes beyond one hour a week, and will probably be less. This also does not include 24/7 response time, but no service provider evaluated provides that level of service anyways.

Total:

  • One-time setup: 3800EUR (200EUR hardware, 3600EUR staff)
  • Recurrent: roughly between 5000EUR and 7500EUR/year, majority in staff

Alternatives considered

There are three dimensions to our “decision tree”:

  1. Hosting mailboxes or only forwards: this means that instead of just forwarding emails to some other providers, we actually allow users to store emails on the server. Current situation is we only do forwards
  2. SMTP authentication: this means allowing users to submit email using a username and password over the standard SMTP (technically “submission”) port. This is currently not allowed also some have figured out they can do this over SSH already.
  3. Self-hosted or hosted elsewhere: if we host the email service ourselves right now or not. The current situation is we allow inbound messages but we do not store them. Mailbox storage is delegated to each individual choice of email provider, which also handles SMTP authentication.

Here are is the breakdown of pros and cons of each approach. Note that there are multiple combinations of those possible, for example we could continue not having mailboxes but allow SMTP authentication, and delegate this to a third party. Obviously, some combinations (like no SMTP authentication and mailboxes) are a little absurd and should be taken with a grain of salt.

TP full hosting: mailboxes, SMTP authentication

Pros:

  • Easier for TPA to diagnose email problems than if email is hosted by an undetermined third party
  • People’s personal email is not mixed up with Tor email.
  • Easier delegation between staff on rotations
  • Control over where data is stored and how
  • Full control of our infrastructure
  • Less trust issues

Cons:

  • probably the most expensive option
  • requires more skilled staff
  • high availability harder to achieve
  • high costs

TP not hosting mailboxes; TP hosting outgoing SMTP authentication server

Pros:

  • No data retention issues: TP not responsible for legal issues surrounding mailboxes contents
  • Solves delivery problem and nothing else (minimal solution)
  • We’re already running an SMTP server
  • SSH tunnels already let our lunatic-fringe do a version of this
  • Staff keeps using own mail readers (eg gmail UI) for receiving mail
  • Federated solution
  • probably the cheapest option
  • Work email cannot be accessed by TP staff

Cons:

  • SMTP-AUTH password management (admin effort and risk)
  • Possible legal requests to record outgoing mail? (SSH lunatic-fringe already at risk, though)
  • DKIM/SPF politics vs “slippery slope”
  • Forces people to figure out some good ISP to host their email
  • Shifts the support burden to individuals
  • Harder to diagnose email problems
  • Staff or “role” email accounts cannot be shared

TP pays third party (riseup, protonmail, mailfence, gmail??) for full service (mailboxes, delivery)

Pros:

  • Less admin effort
  • Less/no risk to TP infrastructure (legal or technical)
  • Third party does not hold email data hostage; only handles outgoing
  • We know where data is hosted instead of being spread around

Cons:

  • Not a federated solution
  • Implicitly accepts email cartel model of “trusted” ISPs
  • Varying levels of third party data management trust required
  • Some third parties require custom software (protonmail)
  • Single point of failure.
  • Might force our users to pick a provider they dislike
  • All eggs in the same basket

Status quo (no mailboxes, no authentication)

Pros:

  • Easy. Fast. Cheap. Pick three.

Cons:

  • Shifts burden of email debugging to users, lack of support

Details of the chosen alternative (SMTP authentication):

  • Postfix + offline LDAP authentication (current proposal)
  • Postfix + direct LDAP authentication: discarded because it might fail when the LDAP server goes down. LDAP server is currently not considered to be critical and can be restarted for maintenance without affecting the rest of the infrastructure.
  • reusing existing field like webPassword or rtcPassword in LDAP: considered a semantic violation.

See also internal Nextcloud document.

No benchmark considered necessary.