Description

This role setups up a host so that it sends outgoing mails over a smarthost and optionally forwards email addressed to local system users. A secure alternative to ssmtp.

Why shouldn't I use ssmtp, isn't it easier to setup?

I actually believe that this role makes it even easier to setup postfix than ssmtp.

This is what I found out when I installed ssmtp myself:

I wanted to use ssmtp today too, but noticed that it does NOT verify the SSL/TLS certificate of the remote server on the current debian & ubuntu releases and also does NOT verify the hostname of the certificate. This is a major issue, as this effectively renders the encryption useless and your password is being transmitted alike to being plaintext and anyone can sniff it. This has also been reported in a debian bug, but there has not been any progress for years: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=662960

The ssmtp version in the Redhat packages has been patched to atleast verify the certificate, but the hostname is still NOT being verified and the encryption is therefore as insecure as on debian/ubuntu. There is a bug for this, but there is also no progress for years: https://bugzilla.redhat.com/show_bug.cgi?id=864894

So, if you care about the security of the email account you use for your servers outgoing emails, do NOT use ssmtp.

ssmtp has had no active development since atleast 2009: https://anonscm.debian.org/gitweb/?p=ssmtp/ssmtp.git

In addition to these points, any user that can send mails over ssmtp needs read-access to the ssmtp config file which includes the username and password used for smtp auth. In normal conditions, you would probably give read permission to 'other', which would mean that for every single user/service on that system could read your smtp credentials.

This is not the case with the security-focused design of postfix.

Requirements

This role works on all debian-based distributions and could easily be patched to work on any distribution which provides postfix.

Ansible version 2.4 or greater is required for this role.

Role Variables

• relaymail_smtp_host: hostname of the smtp server used for relaying email (required)
  • Example: smtp.example.org
• relaymail_smtp_port: port of the smtp server used for relaying email
  • Default: 587
• relaymail_smtp_user: username to authenticate with at the relaying mailserver (required)
  • Example: [email protected]
• relaymail_smtp_password: password to authenticate with at the rayling mailserver (required)
• relaymail_force_from_address: overwrite from address with relaymail_smtp_user (or relaymail_from_address if it is defined). all overwrites the from address for all emails, local overwrites it for all mail sent from a local user, none never overwrites the from address
  • Default: all
• relaymail_from_address: optional from address to be used by relaymail_force_from_address instead of relaymail_smtp_user
  • Example: user or [email protected]
• relaymail_overwrite_to: all overwrites the to address for all emails, local overwrites the to address for emails addressed to local users, none does never overwrite the to address
  • Default: all
• relaymail_overwrite_to_target: email address which mails with overwritten to should be sent to (required when relaymail_overwrite_to is not none)
  • Example: [email protected]
• relaymail_smtp_tls_security_level: See http://www.postfix.org/postconf.5.html#smtp_tls_security_level
  • Example: dane-only
  • Default: secure
• relaymail_smtp_tls_wrappermode: Connect using explicit SSL/TLS mode (instead of STARTSSL). Required when submitting mail on port 465 (SMTPS).
  • Example: "yes"
  • Default: "no"
• relaymail_authorized_submit_users: Only allow specified users to submit mail via sendmail command (see http://www.postfix.org/postconf.5.html#authorized_submit_users)
  • Example: root
  • Default: static:anyone
• relaymail_restrict_port_25: Restrict outbound traffic on port 25 to postfix user (via iptables).
  • Example: false
  • Default: true
• relaymail_enable_smtpd: Enable smtpd on port 25 for smtp-based mail submission
  • Example: true
  • Default: false
• relaymail_inet_interfaces: Interfaces to listen on when smtpd is enabled
  • Example: all
  • Default: loopback-only
• relaymail_mynetworks: Networks from which to accept and relay emails (only applicable when smtpd is enabled)
  • Example: 127.0.0.0/8 172.30.0.0/16
  • Default: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
• relaymail_authorized_smtp_users: Users allowed to submit mail via local smtp
  • Example: ['keepalived']
  • Default: []
• relaymail_install_rsyslog: Installs rsyslog which is responsible for writing postfix log messages to /var/log/mail.log
  • Example: false
  • Default: true
• relaymail_additional_options: dictionary of key/value pairs to append to main.cf.
  • Default: {}
• relaymail_additional_master_config: Additional config which is appended to master.cf
  • Default: ``

Note: Options set using relaymail_additional_options will override previous settings. Per the postfix manual, "When the same parameter is defined multiple times, only the last instance is remembered." So while overrides are valid, postfix will generate a warning message

Example Playbook

- hosts: all
  roles:
    - role: Yannik.relaymail
      relaymail_smtp_host: smtp.example.org
      relaymail_smtp_user: [email protected]
      relaymail_smtp_password: secret
      relaymail_overwrite_to: local
      relaymail_overwrite_to_target: [email protected]
      relaymail_additional_options:
        smtp_tls_wrappermode: "yes"

License

GPLv2

Author Information

Yannik Sembritzki