enable fail2ban for ssh and dovecot

Merge branch 'master' of https://github.com/h8h/mailinabox

see #353, #319

CHANGELOG.md

@@ -4,6 +4,10 @@ CHANGELOG
 In Development...
 -----------------
 
+System:
+
+* Brute-force SSH and IMAP login attempts are now prevented by properly configuring fail2ban.
+
 Control panel:
 
 * The new check that system services are running mistakenly checked that the Dovecot Managesieve service is publicly accessible. Although the service binds to the public network interface we don't open the port in ufw. On some machines it seems that ufw blocks the connection from the status checks (which seems correct) and on some machines (mine) it doesn't, which is why I didn't notice the problem.

conf/fail2ban/dovecotimap.conf

@@ -0,0 +1,22 @@
+# Fail2Ban filter Dovecot authentication and pop3/imap server
+# For Mail-in-a-Box
+
+[INCLUDES]
+
+before = common.conf
+
+[Definition]
+
+_daemon = (auth|dovecot(-auth)?|auth-worker)
+
+failregex = ^%(__prefix_line)s(pop3|imap)-login: (Info: )?(Aborted login|Disconnected)(: Inactivity)? \(((no auth attempts|auth failed, \d+ attempts)( in \d+ secs)?|tried to use (disabled|disallowed) \S+ auth)\):( user=<\S*>,)?( method=\S+,)? rip=<HOST>, lip=(\d{1,3}\.){3}\d{1,3}(, TLS( handshaking)?(: Disconnected)?)?(, session=<\S+>)?\s*$
+
+ignoreregex =
+
+# DEV Notes:
+# * the first regex is essentially a copy of pam-generic.conf
+# * Probably doesn't do dovecot sql/ldap backends properly
+#
+# Author: Martin Waschbuesch
+#         Daniel Black (rewrote with begin and end anchors)
+#         Mail-in-a-Box (swapped session=...)

conf/fail2ban/jail.local

@@ -0,0 +1,34 @@
+# Fail2Ban configuration file.
+# For Mail-in-a-Box
+[DEFAULT]
+
+# bantime in seconds
+bantime  = 60
+
+# This should ban dumb brute-force attacks, not oblivious users.
+findtime = 30
+maxretry = 20
+
+#
+# JAILS
+#
+
+[ssh]
+
+enabled  = true
+logpath  = /var/log/auth.log
+maxretry = 20
+
+[ssh-ddos]
+
+enabled  = true
+maxretry = 20
+
+[sasl]
+
+enabled  = true
+
+[dovecot]
+
+enabled = true
+filter  = dovecotimap

setup/system.sh

@@ -106,3 +106,11 @@ fi
 
 restart_service bind9
 restart_service resolvconf
+
+# ### Fail2Ban Service
+
+# Configure the Fail2Ban installation to prevent dumb bruce-force attacks against dovecot, postfix and ssh
+cp conf/fail2ban/jail.local /etc/fail2ban/jail.local
+cp conf/fail2ban/dovecotimap.conf /etc/fail2ban/filter.d/dovecotimap.conf
+
+restart_service fail2ban