# Firewall

ApisCP utilizes firewalld (opens new window) for its firewall. Rampart is a module that serves as a wrapper for fail2ban (opens new window), a brute-force deterrent that blocks threats through firewalld. These two components act in tandem to keep your server secure while exercising some intelligence. Rampart is for ephemeral blocks that automatically expire after a fixed duration (see network/setup-firewall (opens new window)) whereas a separate firewalld permanent whitelist/blacklist is provided.

During installation, ApisCP will detect the connected IP address and whitelist it to avoid triggering a block by fail2ban, for example if you forget your password multiple times. If your IP address changes or you setup ApisCP from behind a proxy, then you can easily update the whitelist with cpcmd

cpcmd scope:set rampart.fail2ban-whitelist '1.2.3.4'

To view active fail2ban whitelists use scope:get (opens new window):

cpcmd scope:get rampart.fail2ban-whitelist

Whitelists may be IP address (64.22.68.1) or CIDR range (64.22.68.1/24). rampart.fail2ban-whitelist is an append-only operation. Edit /etc/fail2ban/jail.conf by hand to remove old IP addresses.

Firewall overview

# Whitelisting

ApisCP restricts access to all ports except for well-known services (HTTP, FTP, mail, SSH) and optional services (CP, user daemons). A second whitelist, which allows access to blocked ports as well as overrides Rampart can be set using cpcmd rampart:whitelist:

cpcmd rampart:whitelist 192.168.0.1/24

These entries are permanent and supersede enforcement by fail2ban. A whitelist may be removed by specifying remove as the second parameter, e.g. rampart:whitelist '192.168.0.1/24' 'remove'

TIP

Single quotes are not compulsory, but help the shell (Bourne shell) discriminate between boundary arguments. Certain metacharacters, such as $, (, ), ;, and | have special meaning.

# Delegated Whitelisting

Site Administrators can whitelist a limited number of IP addresses by through Account > Whitelisting. This value can be toggled per-site by adjusting rampart,max. If set to DEFAULT it inherits rampart,max service value. A few specific values for rampart,max imply specific meanings:

  • -1: unlimited whitelisting entries (OS limit)
  • 0: disable whitelisting
  • > 0: up to n whitelist entries

A delegated whitelist entry permits access even if the IP would have been banned by brute-force protection. Delegated whitelisting uses the same API call, rampart:whitelist(), but is not equivalent to whitelisting as admin, which bypasses any firewall rules and allows absolute access. See Delegation precedence below for changing this behavior.

Entries are codified in rampart,whitelist as a list of IPv4/IPv6 addresses. When a site is deleted, the whitelist is not released until all sites that hold a reference to the whitelist have been removed.

# Permit 20 whitelisted IPs to domain.com
EditDomain -c rampart,max=20 domain.com
# Allow otherdomain.com unlimited access
EditDomain -c rampart,max=-1 otherdomain.com

Additionally, rampart:whitelist() (without arguments) allows the caller to whitelist its public IP if not previously whitelisted. rampart:temp($ip = null, $duration = 7200) works similarly with a temporary whitelisting that deauthorizes after the set interval (default: 7200 seconds). These features may be invoked with Beacon (opens new window) to simplify batch scripting with dhcp clients.

# Delegation precedence

New in 3.2.18

Delegation is placed in the ignorelist ipset. This takes precedence after administrative ingress rules, but before brute-force rejection rules. Thus a delegated whitelist entry is only protected from brute-force rejection. Delegated whitelisting may use the whitelist ipset, which takes precedence before any administrative rules are applied giving the IP address absolute permission. Likewise when rampart:whitelist() is called by admin, these entries are always added to the whitelist ipset.

# Put 1.2.3.4 in whitelist
cpcmd rampart:whitelist 1.2.3.4
# Put 2.3.4.5 in ignorelist
cpcmd -d domain.com rampart:whitelist 2.3.4.5

Delegation set name is controlled via [rampart] => delegation_set. delegation_set may be either ignorelist or whitelist. When converting over, manually rename the set.

cpcmd scope:set cp.config rampart delegation_set ignorelist
ipset swap whitelist ignorelist
systemctl restart apiscp

# Blacklisting

A blacklist exists to explicitly deny addresses that are not blocked by Rampart's adaptive firewall.

cpcmd rampart:blacklist 192.168.0.10

Blacklists are lower priority than whitelist and higher priority than fail2ban. CIDR ranges also work and can be fed lists for example from IPdeny (opens new window):

curl -o- http://www.ipdeny.com/ipblocks/data/countries/cn.zone | while read -r IP ; do cpcmd rampart:blacklist "$IP" ; done

All blacklist listings are permanent unless removed with cpcmd rampart:blacklist($ip, 'remove').

# Components

A service filter inspects a log for offending activity. A service accumulator is a counter internal to fail2ban that keeps track of offending activity per IP and filter over a duration. Once this threshold is reached, a ban is placed on the IP for all ports configured for that filter.

Service accumulators by default permit 3 attempts (f2b_maxretry) in a 5 minute period (f2b_findtime). Additional failures result in a 10 minute ban (f2b_bantime). These values may be altered in Bootstrapper.

# Change monitoring interval to 15 minutes for Dovecot
cpcmd scope:set cp.bootstrapper f2b_dovecot_findtime 900
# Change bantime for SSH to 1 hour
cpcmd scope:set cp.bootstrapper f2b_sshd_bantime 3600
# Change malware trigger threshold to 5 hits
cpcmd scope:set cp.bootstrapper f2b_malware_maxretry 5
# Apply settings
upcp -sb fail2ban/configure-jails

Per-service accumulators may be set specifying f2b_ + filter name + _ + accumulator var. For example, to change the bantime setting for "dovecot" filter to 300 seconds:

cpcmd scope:set cp.bootstrapper f2b_dovecot_bantime 300
upcp -sb fail2ban/configure-jails

Service filters are available in /etc/fail2ban/filter.d. Each jail in the next section uses a single filter to monitor for bad activity.

# Jails

A variety of jails provide granular protection over public services. The following table summarizes these jails. This may also be used as a reference for inbound ports.

Jail Port protection Role
dovecot 110, 995, 143, 995 IMAP/POP3 failures
evasive 80, 443 HTTP brute-force
malware 80, 443 HTTP uploads containing malware
mysqld 3306 Remote MySQL failures
pgsql 5432 Remote PostgreSQL failures
postfix 25, 587, 465 Anomalous SMTP traffic
postfix-sasl 25, 587, 465 SMTP (SASL auth) failures
recidive ALL PORTS Recurrent failures
spambots 25, 587 Known bad SMTP fingerprints
sshd 22 (or sshd_port) SSH failures
vsftpd 20, 21, 989, 990 FTP failures

# Recidivism

"Recidivism" is a specific term derived from fail2ban's recidive jail (opens new window) for repeat offenders. If a user repeats a ban across any monitored service 5 times (f2b_recidive_maxretry) in 12 hours (f2b_recidive_findtime), then a 10-day ban (f2b_recidive_bantime) is applied. Values may be altered by changing the parenthesized value with a Scope.

# Ban recidive offenders for 1 month
cpcmd scope:set cp.bootstrapper f2b_recidive_bantime $((86400*30))
upcp -sb fail2ban/configure-jails

# Unbanning IP addresses

All IP addresses automatically unban from Rampart after a fixed duration. To manually unban an address from Rampart use cpcmd:

# Ban 192.168.0.4 in recidive, which is a long-term ban > 1 week
cpcmd rampart:ban 192.168.0.4 recidive
# Validate which jails 192.168.0.4 is present in
cpcmd rampart:is-banned 192.168.0.4
# Unban 192.168.0.4 from all jails
cpcmd rampart:unban 192.168.0.4

Permanent blacklist and whitelist entries can be removed with firewall-cmd

# Add 192.168.0.4 to the permanent whitelist
cpcmd rampart:whitelist 192.168.0.4
# Show all whitelist entries
ipset list whitelist
# Remove 192.168.0.4 from whitelist
cpcmd rampart:whitelist 192.168.0.4 remove

# Public backdoor

ApisCP provides many means to unban an IP address for a legitimate user:

  1. Delegated Whitelisting as described above
  2. cp-proxy (opens new window), if the proxy is installed on non-hosting server
  3. Automatic expiry as discussed in Service filters
  4. Whitelisted access to ApisCP on 2083 when always_permit_panel_login is True (disabled by default). A Scope, cp.whitelist-access exists to facilitate this. See SECURITY.md for security implications, specifically the Rampart subsystem of ApisCP that guards panel access.