[pve-devel] [PATCH firewall] implement fail2ban backend

[Oguz Bektas <o.bektas@proxmox.com>]

adds a section "[FAIL2BAN]" in the hostfw configuration, which allows
the properties 'maxretry' and 'bantime' (in minutes) for the GUI ports.

Signed-off-by: Oguz Bektas <o.bektas@proxmox.com>
---
RFC->PATCH:

* better parser regex to allow comments in hostfw
* use heredoc for multiline file contents
* check if filter file exists, and if the jail configuration has changed
before writing it out
* removed the unrelated empty lines that i forgot, and the debug print :D
* error out if we can't parse an option


 debian/control      |  1 +
 src/PVE/Firewall.pm | 79 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/debian/control b/debian/control
index 4684c5b..377c9ae 100644
--- a/debian/control
+++ b/debian/control
@@ -17,6 +17,7 @@ Package: pve-firewall
 Architecture: any
 Conflicts: ulogd,
 Depends: ebtables,
+         fail2ban,
          ipset,
          iptables,
          libpve-access-control,
diff --git a/src/PVE/Firewall.pm b/src/PVE/Firewall.pm
index edc5336..ed13ca5 100644
--- a/src/PVE/Firewall.pm
+++ b/src/PVE/Firewall.pm
@@ -1347,6 +1347,26 @@ our $host_option_properties = {
     },
 };
 
+our $fail2ban_option_properties = {
+	enable => {
+	    description => "Enable or disable fail2ban on a node.",
+	    type => 'boolean',
+	    default => 1,
+	},
+	maxretry => {
+	    description => "Amount of failed tries to ban after.",
+	    type => 'integer',
+	    minimum => 1,
+	    default => 3,
+	},
+	bantime => {
+	    description => "Minutes to ban suspicious IPs.",
+	    type => 'integer',
+	    minimum => 1,
+	    default => 5,
+	},
+};
+
 our $vm_option_properties = {
     enable => {
 	description => "Enable/disable firewall rules.",
@@ -2407,6 +2427,39 @@ sub ruleset_generate_vm_rules {
     }
 }
 
+sub generate_fail2ban_config {
+    my ($maxretry, $bantime) = @_;
+
+    my $bantime_seconds = $bantime * 60;
+
+    my $fail2ban_filter = <<CONFIG;
+[Definition]
+failregex = pvedaemon\\[.*authentication failure; rhost=<HOST> user=.* msg=.*
+ignoreregex =
+CONFIG
+    my $filter_path = '/etc/fail2ban/filter.d/proxmox.conf';
+    PVE::Tools::file_set_contents($filter_path, $fail2ban_filter) unless -f $filter_path;
+
+
+    my $fail2ban_jail = <<CONFIG;
+[proxmox]
+enabled = true
+port = https,http,8006
+filter = proxmox
+logpath = /var/log/daemon.log
+maxretry = $maxretry
+bantime = $bantime_seconds
+CONFIG
+
+    my $jail_path = "/etc/fail2ban/jail.d/proxmox.conf";
+    my $current_fail2ban_jail = PVE::Tools::file_get_contents($jail_path);
+
+    if ($current_fail2ban_jail ne $fail2ban_jail) {
+	PVE::Tools::file_set_contents($jail_path, $fail2ban_jail);
+	run_command([qw(systemctl try-reload-or-restart fail2ban.service)]);
+    }
+}
+
 sub generate_nfqueue {
     my ($options) = @_;
 
@@ -2937,6 +2990,16 @@ sub parse_alias {
     return undef;
 }
 
+sub parse_fail2ban_option {
+    my ($line) = @_;
+
+    if ($line =~ m/^(maxretry|bantime):\s+(\d+)\s*(?:#\s*(.*?)\s*)?$/) {
+	return ($1, $2 // $fail2ban_option_properties->{$1}->{default});
+    } else {
+	die "error parsing fail2ban options: $line";
+    }
+}
+
 sub generic_fw_config_parser {
     my ($filename, $cluster_conf, $empty_conf, $rule_env) = @_;
 
@@ -2965,6 +3028,11 @@ sub generic_fw_config_parser {
 
 	my $prefix = "$filename (line $linenr)";
 
+	if ($empty_conf->{fail2ban} && ($line =~ m/^\[fail2ban\]$/i)) {
+	    $section = 'fail2ban';
+	    next;
+	}
+
 	if ($empty_conf->{options} && ($line =~ m/^\[options\]$/i)) {
 	    $section = 'options';
 	    next;
@@ -3046,6 +3114,13 @@ sub generic_fw_config_parser {
 		$res->{aliases}->{lc($data->{name})} = $data;
 	    };
 	    warn "$prefix: $@" if $@;
+	} elsif ($section eq 'fail2ban') {
+	    my ($opt, $value) = eval { parse_fail2ban_option($line) };
+	    if (my $err = $@) {
+		warn "fail2ban parsing error: $err";
+		next;
+	    }
+	    $res->{fail2ban}->{$opt} = $value;
 	} elsif ($section eq 'rules') {
 	    my $rule;
 	    eval { $rule = parse_fw_rule($prefix, $line, $cluster_conf, $res, $rule_env); };
@@ -3620,7 +3695,7 @@ sub load_hostfw_conf {
 
     $filename = $hostfw_conf_filename if !defined($filename);
 
-    my $empty_conf = { rules => [], options => {}};
+    my $empty_conf = { rules => [], options => {}, fail2ban => {}};
     return generic_fw_config_parser($filename, $cluster_conf, $empty_conf, 'host');
 }
 
@@ -4590,6 +4665,8 @@ sub update {
 	}
 
 	my $hostfw_conf = load_hostfw_conf($cluster_conf);
+	my $fail2ban_opts = $hostfw_conf->{fail2ban};
+	generate_fail2ban_config($fail2ban_opts->{maxretry}, $fail2ban_opts->{bantime});
 
 	my ($ruleset, $ipset_ruleset, $rulesetv6, $ebtables_ruleset) = compile($cluster_conf, $hostfw_conf);
 
-- 
2.30.2