[pve-devel] [PATCH v2 firewall] implement fail2ban backend & API

[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.

enable: whether fail2ban jail is enabled or not
maxretry: amount of login tries allowed
bantime: amount of minutes to ban suspicious host

the configuration file is derived from our wiki [0]

example API usage
-----
$ pvesh set /nodes/localhost/firewall/fail2ban --enable 1 --bantime 10 --maxretry 3

$ pvesh get /nodes/localhost/firewall/fail2ban
┌──────────┬───────┐
│ key      │ value │
╞══════════╪═══════╡
│ bantime  │ 10    │
├──────────┼───────┤
│ enable   │ 1     │
├──────────┼───────┤
│ maxretry │ 3     │
└──────────┴───────┘

$ pvesh set /nodes/localhost/firewall/fail2ban --bantime 100
$ pvesh get /nodes/localhost/firewall/fail2ban
┌──────────┬───────┐
│ key      │ value │
╞══════════╪═══════╡
│ bantime  │ 100   │
├──────────┼───────┤
│ enable   │ 1     │
├──────────┼───────┤
│ maxretry │ 3     │
└──────────┴───────┘

$ pvesh set /nodes/localhost/firewall/fail2ban --enable 0
$ pvesh get /nodes/localhost/firewall/fail2ban
┌──────────┬───────┐
│ key      │ value │
╞══════════╪═══════╡
│ bantime  │ 100   │
├──────────┼───────┤
│ enable   │ 0     │
├──────────┼───────┤
│ maxretry │ 3     │
└──────────┴───────┘
-----

[0]: https://pve.proxmox.com/wiki/Fail2ban

Signed-off-by: Oguz Bektas <o.bektas@proxmox.com>
---
 debian/control                |   1 +
 src/PVE/API2/Firewall/Host.pm |  95 ++++++++++++++++++++++++++++++++
 src/PVE/Firewall.pm           | 101 +++++++++++++++++++++++++++++++++-
 3 files changed, 196 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/API2/Firewall/Host.pm b/src/PVE/API2/Firewall/Host.pm
index b66ca55..22cec85 100644
--- a/src/PVE/API2/Firewall/Host.pm
+++ b/src/PVE/API2/Firewall/Host.pm
@@ -62,6 +62,46 @@ my $add_option_properties = sub {
     return $properties;
 };
 
+my $fail2ban_properties = $PVE::Firewall::fail2ban_option_properties;
+
+my $add_fail2ban_properties = sub {
+    my ($properties) = @_;
+
+    foreach my $k (keys %$fail2ban_properties) {
+	$properties->{$k} = $fail2ban_properties->{$k};
+    }
+
+    return $properties;
+};
+
+__PACKAGE__->register_method({
+    name => 'get_fail2ban',
+    path => 'fail2ban',
+    method => 'GET',
+    description => "Get host firewall fail2ban options.",
+    proxyto => 'node',
+    permissions => {
+	check => ['perm', '/nodes/{node}', [ 'Sys.Audit' ]],
+    },
+    parameters => {
+	additionalProperties => 0,
+	properties => {
+	    node => get_standard_option('pve-node'),
+	},
+    },
+    returns => {
+	type => "object",
+	properties => $fail2ban_properties,
+    },
+    code => sub {
+	my ($param) = @_;
+
+	my $cluster_conf = PVE::Firewall::load_clusterfw_conf();
+	my $hostfw_conf = PVE::Firewall::load_hostfw_conf($cluster_conf);
+
+	return PVE::Firewall::copy_opject_with_digest($hostfw_conf->{fail2ban});
+    }});
+
 
 __PACKAGE__->register_method({
     name => 'get_options',
@@ -148,6 +188,61 @@ __PACKAGE__->register_method({
 	return undef;
     }});
 
+__PACKAGE__->register_method({
+    name => 'set_fail2ban',
+    path => 'fail2ban',
+    method => 'PUT',
+    description => "Set host firewall fail2ban options.",
+    protected => 1,
+    proxyto => 'node',
+    permissions => {
+	check => ['perm', '/nodes/{node}', [ 'Sys.Modify' ]],
+    },
+    parameters => {
+	additionalProperties => 0,
+	properties => &$add_fail2ban_properties({
+	    node => get_standard_option('pve-node'),
+	    delete => {
+		type => 'string', format => 'pve-configid-list',
+		description => "A list of settings you want to delete.",
+		optional => 1,
+	    },
+	    digest => get_standard_option('pve-config-digest'),
+	}),
+    },
+    returns => { type => "null" },
+    code => sub {
+	my ($param) = @_;
+	PVE::Firewall::lock_hostfw_conf(10, sub {
+	    my $cluster_conf = PVE::Firewall::load_clusterfw_conf();
+	    my $hostfw_conf = PVE::Firewall::load_hostfw_conf($cluster_conf);
+
+	    my (undef, $digest) = PVE::Firewall::copy_opject_with_digest($hostfw_conf->{fail2ban});
+	    PVE::Tools::assert_if_modified($digest, $param->{digest});
+
+	    if ($param->{delete}) {
+		foreach my $opt (PVE::Tools::split_list($param->{delete})) {
+		    raise_param_exc({ delete => "no such option '$opt'" })
+			if !$fail2ban_properties->{$opt};
+		    delete $hostfw_conf->{fail2ban}->{$opt};
+		}
+	    }
+
+	    if (defined($param->{enable})) {
+		$param->{enable} = $param->{enable} ? 1 : 0;
+	    }
+
+	    foreach my $k (keys %$fail2ban_properties) {
+		next if !defined($param->{$k});
+		$hostfw_conf->{fail2ban}->{$k} = $param->{$k};
+	    }
+
+	    PVE::Firewall::save_hostfw_conf($hostfw_conf);
+	});
+
+	return undef;
+    }});
+
 __PACKAGE__->register_method({
     name => 'log',
     path => 'log',
diff --git a/src/PVE/Firewall.pm b/src/PVE/Firewall.pm
index edc5336..7e5856b 100644
--- a/src/PVE/Firewall.pm
+++ b/src/PVE/Firewall.pm
@@ -1347,6 +1347,29 @@ our $host_option_properties = {
     },
 };
 
+our $fail2ban_option_properties = {
+	enable => {
+	    description => "Enable or disable fail2ban on a node.",
+	    type => 'boolean',
+	    optional => 1,
+	    default => 1,
+	},
+	maxretry => {
+	    description => "Amount of failed tries to ban after.",
+	    type => 'integer',
+	    optional => 1,
+	    minimum => 1,
+	    default => 3,
+	},
+	bantime => {
+	    description => "Minutes to ban suspicious IPs.",
+	    type => 'integer',
+	    optional => 1,
+	    minimum => 1,
+	    default => 5,
+	},
+};
+
 our $vm_option_properties = {
     enable => {
 	description => "Enable/disable firewall rules.",
@@ -2407,6 +2430,41 @@ sub ruleset_generate_vm_rules {
     }
 }
 
+sub generate_fail2ban_config {
+    my ($fail2ban_opts) = @_;
+
+    my $enable = $fail2ban_opts->{enable} ? 'true' : 'false';
+    my $maxretry = $fail2ban_opts->{maxretry};
+    my $bantime = $fail2ban_opts->{bantime} * 60; # convert minutes to seconds
+
+    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) if !-f $filter_path;
+
+
+    my $fail2ban_jail = <<CONFIG;
+[proxmox]
+enabled = $enable
+port = https,http,8006
+filter = proxmox
+logpath = /var/log/daemon.log
+maxretry = $maxretry
+bantime = $bantime
+CONFIG
+
+    my $jail_path = "/etc/fail2ban/jail.d/proxmox.conf";
+    my $current_fail2ban_jail = PVE::Tools::file_get_contents($jail_path) if -f $jail_path;
+
+    if ($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 +2995,16 @@ sub parse_alias {
     return undef;
 }
 
+sub parse_fail2ban_option {
+    my ($line) = @_;
+
+    if ($line =~ m/^(enable|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 +3033,11 @@ 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 +3119,13 @@ 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 = $@) {
+		warn "$err";
+		next;
+	    }
+	    $res->{fail2ban}->{$opt} = $value;
 	} elsif ($section eq 'rules') {
 	    my $rule;
 	    eval { $rule = parse_fw_rule($prefix, $line, $cluster_conf, $res, $rule_env); };
@@ -3251,6 +3331,21 @@ my $format_options = sub {
     return $raw;
 };
 
+my $format_fail2ban = sub {
+    my ($fail2ban_options) = @_;
+
+    my $raw = '';
+
+    $raw .= "[FAIL2BAN]\n\n";
+    foreach my $opt (keys %$fail2ban_options) {
+	$raw .= "$opt: $fail2ban_options->{$opt}\n";
+    }
+    $raw .= "\n";
+
+    return $raw;
+
+};
+
 my $format_aliases = sub {
     my ($aliases) = @_;
 
@@ -3620,7 +3715,7 @@ 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');
 }
 
@@ -3630,7 +3725,9 @@ sub save_hostfw_conf {
     my $raw = '';
 
     my $options = $hostfw_conf->{options};
+    my $fail2ban_options = $hostfw_conf->{fail2ban};
     $raw .= &$format_options($options) if $options && scalar(keys %$options);
+    $raw .= &$format_fail2ban($fail2ban_options) if $fail2ban_options && scalar(keys %$fail2ban_options);
 
     my $rules = $hostfw_conf->{rules};
     if ($rules && scalar(@$rules)) {
@@ -4590,6 +4687,8 @@ sub update {
 	}
 
 	my $hostfw_conf = load_hostfw_conf($cluster_conf);
+	my $fail2ban_opts = $hostfw_conf->{fail2ban};
+	generate_fail2ban_config($fail2ban_opts) if scalar(keys %$fail2ban_opts);
 
 	my ($ruleset, $ipset_ruleset, $rulesetv6, $ebtables_ruleset) = compile($cluster_conf, $hostfw_conf);
 
-- 
2.30.2