# SPDX-License-Identifier: AGPL-3.0-or-later
# todo: sandbox / harden exim:
-# 1. stop it from running as root. how?
-# https://www.exim.org/exim-html-current/doc/html/spec_html/ch-security_considerations.html
-# * avoid using .forward files, remove that router
-# * set deliver_drop_privilege
-# * set user to run as Debian-exim in systemd
-# * set port to something like 2500, and forward 25 to 2500 with iptables. same for 587.
-# https://superuser.com/questions/710253/allow-non-root-process-to-bind-to-port-80-and-443/1334552#1334552
-# * consider whether other routers like postmaster need modification / removal.
-# 2. restrict its filesystem access from within systemd
+# restrict its filesystem access from within systemd
# todo: harden dovecot. need to do some research. one way is for it to only listen on a wireguard vpn interface, so only clients that are on the vpn can access it.
# todo: consider hardening cups listening on 0.0.0.0
# todo: emailing info@amnimal.ninja produces a bounce, user doesn't exist
# instead of a simple rejection like it should.
-# todo: auto restart of je on checkrestart
-
# todo: run mailping test after running, or otherwise
# clear out terminal alert
# * Install universal packages
-# installs epanicclean
+# installs epanicclean iptables-exim ip6tables-exim
/a/bin/ds/install-my-scripts
if [[ $(debian-codename-compat) == bionic ]]; then
# note: pyzor debian readme says you need to run some initialization command
# but its outdated.
-pi spf-tools-perl p0f postgrey pyzor razor jq moreutils certbot
+pi spf-tools-perl p0f postgrey pyzor razor jq moreutils certbot fail2ban
# bad packages that sometimes get automatically installed
pu openresolv resolvconf
--deploy-hook /a/bin/ds/le-exim-deploy -d $wghost
fi
+# * fail2ban
+
+# todo: test that these configs actually work, eg run
+# s iptables-exim -S
+# and see someone is banned.
+
+sed 's/^ *before *= *iptables-common.conf/before = iptables-common-exim.conf/' \
+ /etc/fail2ban/action.d/iptables-multiport.conf| i /etc/fail2ban/action.d/iptables-exim.conf
+i /etc/fail2ban/action.d/iptables-common-exim.conf <<'EOF'
+# iank: same as iptables-common, except iptables is iptables-exim, ip6tables is ip6tables-exim
+
+# Fail2Ban configuration file
+#
+# Author: Daniel Black
+#
+# This is a included configuration file and includes the definitions for the iptables
+# used in all iptables based actions by default.
+#
+# The user can override the defaults in iptables-common.local
+#
+# Modified: Alexander Koeppe <format_c@online.de>, Serg G. Brester <serg.brester@sebres.de>
+# made config file IPv6 capable (see new section Init?family=inet6)
+
+[INCLUDES]
+
+after = iptables-blocktype.local
+ iptables-common.local
+# iptables-blocktype.local is obsolete
+
+[Definition]
+
+# Option: actionflush
+# Notes.: command executed once to flush IPS, by shutdown (resp. by stop of the jail or this action)
+# Values: CMD
+#
+actionflush = <iptables> -F f2b-<name>
+
+
+[Init]
+
+# Option: chain
+# Notes specifies the iptables chain to which the Fail2Ban rules should be
+# added
+# Values: STRING Default: INPUT
+chain = INPUT
+
+# Default name of the chain
+#
+name = default
+
+# Option: port
+# Notes.: specifies port to monitor
+# Values: [ NUM | STRING ] Default:
+#
+port = ssh
+
+# Option: protocol
+# Notes.: internally used by config reader for interpolations.
+# Values: [ tcp | udp | icmp | all ] Default: tcp
+#
+protocol = tcp
+
+# Option: blocktype
+# Note: This is what the action does with rules. This can be any jump target
+# as per the iptables man page (section 8). Common values are DROP
+# REJECT, REJECT --reject-with icmp-port-unreachable
+# Values: STRING
+blocktype = REJECT --reject-with icmp-port-unreachable
+
+# Option: returntype
+# Note: This is the default rule on "actionstart". This should be RETURN
+# in all (blocking) actions, except REJECT in allowing actions.
+# Values: STRING
+returntype = RETURN
+
+# Option: lockingopt
+# Notes.: Option was introduced to iptables to prevent multiple instances from
+# running concurrently and causing irratic behavior. -w was introduced
+# in iptables 1.4.20, so might be absent on older systems
+# See https://github.com/fail2ban/fail2ban/issues/1122
+# Values: STRING
+lockingopt = -w
+
+# Option: iptables
+# Notes.: Actual command to be executed, including common to all calls options
+# Values: STRING
+iptables = /usr/local/bin/iptables-exim <lockingopt>
+
+
+[Init?family=inet6]
+
+# Option: blocktype (ipv6)
+# Note: This is what the action does with rules. This can be any jump target
+# as per the iptables man page (section 8). Common values are DROP
+# REJECT, REJECT --reject-with icmp6-port-unreachable
+# Values: STRING
+blocktype = REJECT --reject-with icmp6-port-unreachable
+
+# Option: iptables (ipv6)
+# Notes.: Actual command to be executed, including common to all calls options
+# Values: STRING
+iptables = /usr/local/bin/ip6tables-exim <lockingopt>
+EOF
+
+i /etc/fail2ban/jail.d/exim.local <<'EOF'
+[exim]
+enabled = true
+port = 25,587
+filter = exim
+banaction = iptables-exim
+EOF
+if $ir; then
+ m systemctl restart fail2ban
+fi
+
# * common exim4 config
m sed -ri 's/^(\s*rotate\s).*/\11000/' /etc/logrotate.d/exim4-base
-## https://blog.dhampir.no/content/make-exim4-on-debian-respect-forward-and-etcaliases-when-using-a-smarthost
-# i only need .forwards, so just doing that one.
-cd /etc/exim4/conf.d/router
-b=userforward_higher_priority
-# replace the router name so it is unique
-sed -r s/^\\S+:/$b:/ 600_exim4-config_userforward >175_$b
+## disabled. not using .forward files, but this is still interesting
+## for reference.
+# ## https://blog.dhampir.no/content/make-exim4-on-debian-respect-forward-and-etcaliases-when-using-a-smarthost
+# # i only need .forwards, so just doing that one.
+# cd /etc/exim4/conf.d/router
+# b=userforward_higher_priority
+# # replace the router name so it is unique
+# sed -r s/^\\S+:/$b:/ 600_exim4-config_userforward >175_$b
# todo, consider 'separate' in etc/exim4.conf, could it help on busy systems?
m chown -R www-data.www-data $rctmpdir /m/rc
m chmod 750 $rctmpdir
# Ensure the log file monitored by fail2ban exists, or else fail2ban can't start.
- # todo: setup fail2ban
# todo: check for other mailinabox things
m sudo -u www-data touch $rclogdir/errors.log
fi
-# ** auth
+# ** exim: auth
case $HOSTNAME in
bk|je)
EOF
fi
-# ** main daemon use non-default config file
+# ** exim: main daemon use non-default config file
case $HOSTNAME in
bk|$MAIL_HOST)
# to see the default comments in /etc/default/exim4:
QUEUEINTERVAL='30m'
COMMONOPTIONS='-C /etc/exim4/my.conf'
UPEX4OPTS='-o /etc/exim4/my.conf'
-#E4BCD_PANICLOG_NOISE='malware acl condition: clamd /var/run/clamav/clamd\.ctl : unable to connect to UNIX socket'
+#E4BCD_PANICLOG_NOISE='exim user lost privilege for using -C option'
EOF
+ chown Debian-exim:Debian-exim /usr/sbin/exim4
+ # needs guid set in order to become Debian-exim
+ chmod g+s,u+s /usr/sbin/exim4
i /etc/exim4/trusted_configs <<'EOF'
/etc/exim4/my.conf
EOF
;;
esac
+# ** exim non-root
+
+case $HOSTNAME in
+ bk|je|li)
+ # no reason to expect it to ever be there.
+ rm -fv /etc/systemd/system/exim4.service.d/nonroot.conf
+ ;;
+ *)
+ i /etc/systemd/system/exim4.service.d/nonroot.conf <<'EOF'
+[Service]
+# see 56.2 Root privilege in exim spec
+AmbientCapabilities=CAP_NET_BIND_SERVICE
+EOF
+ i /etc/exim4/conf.d/main/000_local-noroot <<'EOF'
+# see 56.2 Root privilege in exim spec
+deliver_drop_privilege = true
+EOF
+ # Note: there are other routers that would also fail due to not running as root,
+ # but afaik, the main router will catch all mail. If not, we will see
+ # something in the queue.
+ rm -fv /etc/exim4/conf.d/router/600_exim4-config_userforward
+ ;;
+esac
+
case $HOSTNAME in
+
# ** $MAIL_HOST|bk|je)
$MAIL_HOST|bk|je)
iankelling.org / git / distro-setup / commitdiff