186 lines
6.1 KiB
Markdown
186 lines
6.1 KiB
Markdown
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<img width="800px" src="www/src/collage-top.png"/>
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# Chatmail services optimized for Delta Chat apps
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This repository helps to setup a ready-to-use chatmail server
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comprised of a minimal setup of the battle-tested
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[postfix smtp](https://www.postfix.org) and [dovecot imap](https://www.dovecot.org) services.
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The setup is designed and optimized for providing chatmail accounts
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for use by [Delta Chat apps](https://delta.chat).
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Chatmail accounts are automatically created by a first login,
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after which the initially specified password is required for using them.
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## Deploying your own chatmail server
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We use `chat.example.org` as the chatmail domain in the following steps.
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Please substitute it with your own domain.
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1. Install the `cmdeploy` command in a virtualenv
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```
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git clone https://github.com/deltachat/chatmail
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cd chatmail
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scripts/initenv.sh
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```
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2. Create chatmail configuration file `chatmail.ini`:
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```
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scripts/cmdeploy init chat.example.org # <-- use your domain
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```
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3. Setup first DNS records for your chatmail domain,
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according to the hints provided by `cmdeploy init`.
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Verify that SSH root login works:
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```
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ssh root@chat.example.org # <-- use your domain
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```
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4. Deploy to the remote chatmail server:
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```
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scripts/cmdeploy run
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```
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This script will also show you additional DNS records
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which you should configure at your DNS provider
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(it can take some time until they are public).
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### Other helpful commands:
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To check the status of your remotely running chatmail service:
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```
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scripts/cmdeploy status
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```
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To check whether your DNS records are correct:
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```
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scripts/cmdeploy dns
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```
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To test whether your chatmail service is working correctly:
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```
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scripts/cmdeploy test
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```
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To measure the performance of your chatmail service:
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```
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scripts/cmdeploy bench
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```
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## Overview of this repository
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This repository drives the development of chatmail services,
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comprised of minimal setups of
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- [postfix smtp server](https://www.postfix.org)
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- [dovecot imap server](https://www.dovecot.org)
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as well as custom services that are integrated with these two:
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- `chatmaild/src/chatmaild/doveauth.py` implements
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create-on-login account creation semantics and is used
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by Dovecot during login authentication and by Postfix
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which in turn uses [Dovecot SASL](https://doc.dovecot.org/configuration_manual/authentication/dict/#complete-example-for-authenticating-via-a-unix-socket)
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to authenticate users
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to send mails for them.
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- `chatmaild/src/chatmaild/filtermail.py` prevents
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unencrypted e-mail from leaving the chatmail service
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and is integrated into postfix's outbound mail pipelines.
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There is also the `cmdeploy/src/cmdeploy/cmdeploy.py` command line tool
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which helps with setting up and managing the chatmail service.
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`cmdeploy run` uses [pyinfra-based scripting](https://pyinfra.com/)
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in `cmdeploy/src/cmdeploy/__init__.py`
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to automatically install all chatmail components on a server.
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### Home page and getting started for users
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`cmdeploy run` also creates default static Web pages and deploys them
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to a nginx web server with:
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- a default `index.html` along with a QR code that users can click to
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create accounts on your chatmail provider,
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- a default `info.html` that is linked from the home page,
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- a default `policy.html` that is linked from the home page.
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All `.html` files are generated
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by the according markdown `.md` file in the `www/src` directory.
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### Refining the web pages
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```
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scripts/cmdeploy webdev
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```
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This starts a local live development cycle for chatmail Web pages:
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- uses the `www/src/page-layout.html` file for producing static
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HTML pages from `www/src/*.md` files
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- continously builds the web presence reading files from `www/src` directory
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and generating html files and copying assets to the `www/build` directory.
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- Starts a browser window automatically where you can "refresh" as needed.
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## Emergency Commands to disable automatic account creation
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If you need to stop account creation,
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e.g. because some script is wildly creating accounts,
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login to the server with ssh and run:
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```
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touch /etc/chatmail-nocreate
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```
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While this file is present, account creation will be blocked.
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### Ports
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[Postfix](http://www.postfix.org/) listens on ports 25 (smtp) and 587 (submission) and 465 (submissions).
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[Dovecot](https://www.dovecot.org/) listens on ports 143 (imap) and 993 (imaps).
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[nginx](https://www.nginx.com/) listens on port 443 (https).
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[acmetool](https://hlandau.github.io/acmetool/) listens on port 80 (http).
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Delta Chat apps will, however, discover all ports and configurations
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automatically by reading the [autoconfig XML file](https://www.ietf.org/archive/id/draft-bucksch-autoconfig-00.html) from the chatmail service.
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## Email authentication
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chatmail servers rely on [DKIM](https://www.rfc-editor.org/rfc/rfc6376)
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to authenticate incoming emails.
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Incoming emails must have a valid DKIM signature with
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Signing Domain Identifier (SDID, `d=` parameter in the DKIM-Signature header)
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equal to the `From:` header domain.
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This property is checked by OpenDKIM screen policy script
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before validating the signatures.
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This correpsonds to strict [DMARC](https://www.rfc-editor.org/rfc/rfc7489) alignment (`adkim=s`),
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but chatmail does not rely on DMARC and does not consult the sender policy published in DMARC records.
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Other legacy authentication mechanisms such as [iprev](https://www.rfc-editor.org/rfc/rfc8601#section-2.7.3)
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and [SPF](https://www.rfc-editor.org/rfc/rfc7208) are also not taken into account.
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If there is no valid DKIM signature on the incoming email,
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the sender receives a "5.7.1 No valid DKIM signature found" error.
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Outgoing emails must be sent over authenticated connection
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with envelope MAIL FROM (return path) corresponding to the login.
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This is ensured by Postfix which maps login username
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to MAIL FROM with
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[`smtpd_sender_login_maps`](https://www.postfix.org/postconf.5.html#smtpd_sender_login_maps)
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and rejects incorrectly authenticated emails with [`reject_sender_login_mismatch`](reject_sender_login_mismatch) policy.
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`From:` header must correspond to envelope MAIL FROM,
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this is ensured by `filtermail` proxy.
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