docker-mailserver/target/postfix/main.cf
Brennan Kinney 76594c21c4
Add note about tls_ssl_options = NO_COMPRESSION
[Postfix docs](http://www.postfix.org/postconf.5.html#tls_ssl_options):

> Disable SSL compression even if supported by the OpenSSL library. Compression is CPU-intensive, and compression before encryption does not always improve security.

[Postfix mailing list discussion](http://postfix.1071664.n5.nabble.com/patch-mitigate-CRIME-attack-td57978.html):

> The CRIME attack does not apply to SMTP, because unlike SMTP, there is no javascript in SMTP clients that makes them send thousands of email messages with chosen plaintext compressed together in the same packet with SASL credentials or other sensitive data.
> The auditor completely failed to take the context into account.

[Mailing list discussion of potential compression CRIME-like attack](https://lists.cert.at/pipermail/ach/2014-December/001660.html)

> keeping compression disabled is a good idea.

If you need a good test score, PCI compliance will likely flag compression despite not having any known risk with non-HTTP TLS.
2020-04-29 19:41:08 +12:00

105 lines
4 KiB
CFEngine3

# See /usr/share/postfix/main.cf.dist for a commented, more complete version
smtpd_banner = $myhostname ESMTP $mail_name (Debian)
biff = no
append_dot_mydomain = no
readme_directory = no
# Basic configuration
# myhostname =
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = $myhostname, localhost.$mydomain, localhost
relayhost =
mynetworks = 127.0.0.0/8 [::1]/128 [fe80::]/64
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
#smtpd_tls_CAfile=
#smtp_tls_CAfile=
smtpd_tls_security_level = may
smtpd_tls_loglevel = 1
smtp_tls_security_level = may
smtp_tls_loglevel = 1
# Reduces CPU overhead with `NO_COMPRESSION`, SMTP not at risk of CRIME attack (see git blame for details)
tls_ssl_options = NO_COMPRESSION
tls_high_cipherlist = ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256
tls_preempt_cipherlist = yes
smtpd_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtp_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_mandatory_ciphers = high
smtpd_tls_mandatory_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_exclude_ciphers = aNULL, LOW, EXP, MEDIUM, ADH, AECDH, MD5, DSS, ECDSA, CAMELLIA128, 3DES, CAMELLIA256, RSA+AES, eNULL
smtpd_tls_dh1024_param_file = /etc/postfix/dhparams.pem
smtpd_tls_CApath = /etc/ssl/certs
smtp_tls_CApath = /etc/ssl/certs
# Settings to prevent SPAM early
smtpd_helo_required = yes
smtpd_delay_reject = yes
smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname, permit
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, check_policy_service unix:private/policyd-spf, reject_unauth_pipelining, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, reject_unknown_recipient_domain, reject_rbl_client zen.spamhaus.org, reject_rbl_client bl.spamcop.net
smtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, reject_unauth_pipelining
smtpd_sender_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unknown_sender_domain
disable_vrfy_command = yes
# Postscreen settings to drop zombies/open relays/spam early
postscreen_dnsbl_action = enforce
postscreen_dnsbl_sites = zen.spamhaus.org*3
bl.mailspike.net
b.barracudacentral.org*2
bl.spameatingmonkey.net
bl.spamcop.net
dnsbl.sorbs.net
psbl.surriel.com
list.dnswl.org=127.0.[0..255].0*-2
list.dnswl.org=127.0.[0..255].1*-3
list.dnswl.org=127.0.[0..255].[2..3]*-4
postscreen_dnsbl_threshold = 3
postscreen_dnsbl_whitelist_threshold = -1
postscreen_greet_action = enforce
postscreen_bare_newline_action = enforce
# SASL
smtpd_sasl_auth_enable = yes
smtpd_sasl_path = /var/spool/postfix/private/auth
smtpd_sasl_type = dovecot
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $mydomain
broken_sasl_auth_clients = yes
# Mail directory
virtual_transport = lmtp:unix:/var/run/dovecot/lmtp
virtual_mailbox_domains = /etc/postfix/vhost
virtual_mailbox_maps = texthash:/etc/postfix/vmailbox
virtual_alias_maps = texthash:/etc/postfix/virtual
# Additional option for filtering
content_filter = smtp-amavis:[127.0.0.1]:10024
# Milters used by DKIM
milter_protocol = 6
milter_default_action = accept
dkim_milter = inet:localhost:8891
dmarc_milter = inet:localhost:8893
smtpd_milters = $dkim_milter,$dmarc_milter
non_smtpd_milters = $dkim_milter
# SPF policy settings
policyd-spf_time_limit = 3600
# Header checks for content inspection on receiving
header_checks = pcre:/etc/postfix/maps/header_checks.pcre
# Remove unwanted headers that reveail our privacy
smtp_header_checks = pcre:/etc/postfix/maps/sender_header_filter.pcre