214 lines
11 KiB
Bash
Executable File
214 lines
11 KiB
Bash
Executable File
#!/bin/bash
|
||
#
|
||
# Postfix (SMTP)
|
||
# --------------
|
||
#
|
||
# Postfix handles the transmission of email between servers
|
||
# using the SMTP protocol. It is a Mail Transfer Agent (MTA).
|
||
#
|
||
# Postfix listens on port 25 (SMTP) for incoming mail from
|
||
# other servers on the Internet. It is responsible for very
|
||
# basic email filtering such as by IP address and greylisting,
|
||
# it checks that the destination address is valid, rewrites
|
||
# destinations according to aliases, and passses email on to
|
||
# another service for local mail delivery.
|
||
#
|
||
# The first hop in local mail delivery is to Spamassassin via
|
||
# LMTP. Spamassassin then passes mail over to Dovecot for
|
||
# storage in the user's mailbox.
|
||
#
|
||
# Postfix also listens on port 587 (SMTP+STARTLS) for
|
||
# connections from users who can authenticate and then sends
|
||
# their email out to the outside world. Postfix queries Dovecot
|
||
# to authenticate users.
|
||
#
|
||
# Address validation, alias rewriting, and user authentication
|
||
# is configured in a separate setup script mail-users.sh
|
||
# because of the overlap of this part with the Dovecot
|
||
# configuration.
|
||
|
||
source setup/functions.sh # load our functions
|
||
source /etc/mailinabox.conf # load global vars
|
||
|
||
# ### Install packages.
|
||
|
||
# Install postfix's packages.
|
||
#
|
||
# * `postfix`: The SMTP server.
|
||
# * `postfix-pcre`: Enables header filtering.
|
||
# * `postgrey`: A mail policy service that soft-rejects mail the first time
|
||
# it is received. Spammers don't usually try agian. Legitimate mail
|
||
# always will.
|
||
# * `ca-certificates`: A trust store used to squelch postfix warnings about
|
||
# untrusted opportunistically-encrypted connections.
|
||
#
|
||
# postgrey is going to come in via the Mail-in-a-Box PPA, which publishes
|
||
# a modified version of postgrey that lets senders whitelisted by dnswl.org
|
||
# pass through without being greylisted. So please note [dnswl's license terms](https://www.dnswl.org/?page_id=9):
|
||
# > Every user with more than 100’000 queries per day on the public nameserver
|
||
# > infrastructure and every commercial vendor of dnswl.org data (eg through
|
||
# > anti-spam solutions) must register with dnswl.org and purchase a subscription.
|
||
|
||
echo "Installing Postfix (SMTP server)..."
|
||
apt_install postfix postfix-pcre postgrey ca-certificates
|
||
|
||
# ### Basic Settings
|
||
|
||
# Set some basic settings...
|
||
#
|
||
# * Have postfix listen on all network interfaces.
|
||
# * Make outgoing connections on a particular interface (if multihomed) so that SPF passes on the receiving side.
|
||
# * Set our name (the Debian default seems to be "localhost" but make it our hostname).
|
||
# * Set the name of the local machine to localhost, which means xxx@localhost is delivered locally, although we don't use it.
|
||
# * Set the SMTP banner (which must have the hostname first, then anything).
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
inet_interfaces=all \
|
||
smtp_bind_address=$PRIVATE_IP \
|
||
smtp_bind_address6=$PRIVATE_IPV6 \
|
||
myhostname=$PRIMARY_HOSTNAME\
|
||
smtpd_banner="\$myhostname ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)" \
|
||
mydestination=localhost
|
||
|
||
# ### Outgoing Mail
|
||
|
||
# Enable the 'submission' port 587 smtpd server and tweak its settings.
|
||
#
|
||
# * Do not add the OpenDMAC Authentication-Results header. That should only be added
|
||
# on incoming mail. Omit the OpenDMARC milter by re-setting smtpd_milters to the
|
||
# OpenDKIM milter only. See dkim.sh.
|
||
# * Even though we dont allow auth over non-TLS connections (smtpd_tls_auth_only below, and without auth the client cant
|
||
# send outbound mail), don't allow non-TLS mail submission on this port anyway to prevent accidental misconfiguration.
|
||
# * Require the best ciphers for incoming connections per http://baldric.net/2013/12/07/tls-ciphers-in-postfix-and-dovecot/.
|
||
# By putting this setting here we leave opportunistic TLS on incoming mail at default cipher settings (any cipher is better than none).
|
||
# * Give it a different name in syslog to distinguish it from the port 25 smtpd server.
|
||
# * Add a new cleanup service specific to the submission service ('authclean')
|
||
# that filters out privacy-sensitive headers on mail being sent out by
|
||
# authenticated users.
|
||
tools/editconf.py /etc/postfix/master.cf -s -w \
|
||
"submission=inet n - - - - smtpd
|
||
-o syslog_name=postfix/submission
|
||
-o smtpd_milters=inet:127.0.0.1:8891
|
||
-o smtpd_tls_security_level=encrypt
|
||
-o smtpd_tls_ciphers=high -o smtpd_tls_exclude_ciphers=aNULL,DES,3DES,MD5,DES+MD5,RC4 -o smtpd_tls_mandatory_protocols=!SSLv2,!SSLv3
|
||
-o cleanup_service_name=authclean" \
|
||
"authclean=unix n - - - 0 cleanup
|
||
-o header_checks=pcre:/etc/postfix/outgoing_mail_header_filters"
|
||
|
||
# Install the `outgoing_mail_header_filters` file required by the new 'authclean' service.
|
||
cp conf/postfix_outgoing_mail_header_filters /etc/postfix/outgoing_mail_header_filters
|
||
|
||
# Modify the `outgoing_mail_header_filters` file to use the local machine name and ip
|
||
# on the first received header line. This may help reduce the spam score of email by
|
||
# removing the 127.0.0.1 reference.
|
||
sed -i "s/PRIMARY_HOSTNAME/$PRIMARY_HOSTNAME/" /etc/postfix/outgoing_mail_header_filters
|
||
sed -i "s/PUBLIC_IP/$PUBLIC_IP/" /etc/postfix/outgoing_mail_header_filters
|
||
|
||
# Enable TLS on these and all other connections (i.e. ports 25 *and* 587) and
|
||
# require TLS before a user is allowed to authenticate. This also makes
|
||
# opportunistic TLS available on *incoming* mail.
|
||
# Set stronger DH parameters, which via openssl tend to default to 1024 bits
|
||
# (see ssl.sh).
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
smtpd_tls_security_level=may\
|
||
smtpd_tls_auth_only=yes \
|
||
smtpd_tls_cert_file=$STORAGE_ROOT/ssl/ssl_certificate.pem \
|
||
smtpd_tls_key_file=$STORAGE_ROOT/ssl/ssl_private_key.pem \
|
||
smtpd_tls_dh1024_param_file=$STORAGE_ROOT/ssl/dh2048.pem \
|
||
smtpd_tls_ciphers=medium \
|
||
smtpd_tls_exclude_ciphers=aNULL \
|
||
smtpd_tls_received_header=yes
|
||
|
||
# Prevent non-authenticated users from sending mail that requires being
|
||
# relayed elsewhere. We don't want to be an "open relay". On outbound
|
||
# mail, require one of:
|
||
#
|
||
# * `permit_sasl_authenticated`: Authenticated users (i.e. on port 587).
|
||
# * `permit_mynetworks`: Mail that originates locally.
|
||
# * `reject_unauth_destination`: No one else. (Permits mail whose destination is local and rejects other mail.)
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
smtpd_relay_restrictions=permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
|
||
|
||
|
||
# ### DANE
|
||
|
||
# When connecting to remote SMTP servers, prefer TLS and use DANE if available.
|
||
#
|
||
# Prefering ("opportunistic") TLS means Postfix will use TLS if the remote end
|
||
# offers it, otherwise it will transmit the message in the clear. Postfix will
|
||
# accept whatever SSL certificate the remote end provides. Opportunistic TLS
|
||
# protects against passive easvesdropping (but not man-in-the-middle attacks).
|
||
# DANE takes this a step further:
|
||
#
|
||
# Postfix queries DNS for the TLSA record on the destination MX host. If no TLSA records are found,
|
||
# then opportunistic TLS is used. Otherwise the server certificate must match the TLSA records
|
||
# or else the mail bounces. TLSA also requires DNSSEC on the MX host. Postfix doesn't do DNSSEC
|
||
# itself but assumes the system's nameserver does and reports DNSSEC status. Thus this also
|
||
# relies on our local bind9 server being present and `smtp_dns_support_level=dnssec`.
|
||
#
|
||
# The `smtp_tls_CAfile` is superflous, but it eliminates warnings in the logs about untrusted certs,
|
||
# which we don't care about seeing because Postfix is doing opportunistic TLS anyway. Better to encrypt,
|
||
# even if we don't know if it's to the right party, than to not encrypt at all. Instead we'll
|
||
# now see notices about trusted certs. The CA file is provided by the package `ca-certificates`.
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
smtp_tls_security_level=dane \
|
||
smtp_dns_support_level=dnssec \
|
||
smtp_tls_CAfile=/etc/ssl/certs/ca-certificates.crt \
|
||
smtp_tls_loglevel=2
|
||
|
||
# ### Incoming Mail
|
||
|
||
# Pass any incoming mail over to a local delivery agent. Spamassassin
|
||
# will act as the LDA agent at first. It is listening on port 10025
|
||
# with LMTP. Spamassassin will pass the mail over to Dovecot after.
|
||
#
|
||
# In a basic setup we would pass mail directly to Dovecot by setting
|
||
# virtual_transport to `lmtp:unix:private/dovecot-lmtp`.
|
||
#
|
||
tools/editconf.py /etc/postfix/main.cf virtual_transport=lmtp:[127.0.0.1]:10025
|
||
|
||
# Who can send mail to us? Some basic filters.
|
||
#
|
||
# * `reject_non_fqdn_sender`: Reject not-nice-looking return paths.
|
||
# * `reject_unknown_sender_domain`: Reject return paths with invalid domains.
|
||
# * `reject_authenticated_sender_login_mismatch`: Reject if mail FROM address does not match the client SASL login
|
||
# * `reject_rhsbl_sender`: Reject return paths that use blacklisted domains.
|
||
# * `permit_sasl_authenticated`: Authenticated users (i.e. on port 587) can skip further checks.
|
||
# * `permit_mynetworks`: Mail that originates locally can skip further checks.
|
||
# * `reject_rbl_client`: Reject connections from IP addresses blacklisted in zen.spamhaus.org
|
||
# * `reject_unlisted_recipient`: Although Postfix will reject mail to unknown recipients, it's nicer to reject such mail ahead of greylisting rather than after.
|
||
# * `check_policy_service`: Apply greylisting using postgrey.
|
||
#
|
||
# Notes: #NODOC
|
||
# permit_dnswl_client can pass through mail from whitelisted IP addresses, which would be good to put before greylisting #NODOC
|
||
# so these IPs get mail delivered quickly. But when an IP is not listed in the permit_dnswl_client list (i.e. it is not #NODOC
|
||
# whitelisted) then postfix does a DEFER_IF_REJECT, which results in all "unknown user" sorts of messages turning into #NODOC
|
||
# "450 4.7.1 Client host rejected: Service unavailable". This is a retry code, so the mail doesn't properly bounce. #NODOC
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
smtpd_sender_restrictions="reject_non_fqdn_sender,reject_unknown_sender_domain,reject_authenticated_sender_login_mismatch,reject_rhsbl_sender dbl.spamhaus.org" \
|
||
smtpd_recipient_restrictions=permit_sasl_authenticated,permit_mynetworks,"reject_rbl_client zen.spamhaus.org",reject_unlisted_recipient,"check_policy_service inet:127.0.0.1:10023"
|
||
|
||
# Postfix connects to Postgrey on the 127.0.0.1 interface specifically. Ensure that
|
||
# Postgrey listens on the same interface (and not IPv6, for instance).
|
||
# A lot of legit mail servers try to resend before 300 seconds.
|
||
# As a matter of fact RFC is not strict about retry timer so postfix and
|
||
# other MTA have their own intervals. To fix the problem of receiving
|
||
# e-mails really latter, delay of greylisting has been set to
|
||
# 180 seconds (default is 300 seconds).
|
||
tools/editconf.py /etc/default/postgrey \
|
||
POSTGREY_OPTS=\"'--inet=127.0.0.1:10023 --delay=180'\"
|
||
|
||
# Increase the message size limit from 10MB to 128MB.
|
||
# The same limit is specified in nginx.conf for mail submitted via webmail and Z-Push.
|
||
tools/editconf.py /etc/postfix/main.cf \
|
||
message_size_limit=134217728
|
||
|
||
# Allow the two SMTP ports in the firewall.
|
||
|
||
ufw_allow smtp
|
||
ufw_allow submission
|
||
|
||
# Restart services
|
||
|
||
restart_service postfix
|
||
restart_service postgrey
|