Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

executable file 632 lines (563 sloc) 21.105 kb
#!/usr/bin/perl -w
#
###############################################################################
#
# File: fwcheck_psad.pl (/usr/sbin/fwcheck_psad)
#
# Purpose: To parse the iptables ruleset on the underlying system to see if
# iptables has been configured to log and block unwanted packets by
# default. This program is called by psad, but can also be executed
# manually from the command line.
#
# Author: Michael Rash (mbr@cipherdyne.org)
#
# Credits: (see the CREDITS file bundled with the psad sources.)
#
# Copyright (C) 1999-2012 Michael Rash (mbr@cipherdyne.org)
#
# License (GNU Public License):
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
# USA
#
###############################################################################
#
use Getopt::Long 'GetOptions';
use strict;
### default psad config file.
my $config_file = '/etc/psad/psad.conf';
### config hash
my %config = ();
my $override_config_str = '';
### commands hash
my %cmds = ();
### fw search string array
my @fw_search = ();
my $help = 0;
my $test_mode = 0;
my $fw_analyze = 0;
my $fw_file = '';
my $fw_search_all = 1;
my $no_fw_search_all = 0;
my $log_and_drop_table = 'filter';
my $enable_ipv6 = 0;
my $psad_lib_dir = '';
&usage(1) unless (GetOptions(
'config=s' => \$config_file, # Specify path to configuration file.
'fw-file=s' => \$fw_file, # Analyze ruleset contained within
# $fw_file instead of a running
# policy.
'fw-analyze' => \$fw_analyze, # Analyze the local iptables ruleset
# and exit.
'no-fw-search-all' => \$no_fw_search_all, # looking for specific log
# prefixes
'Lib-dir=s' => \$psad_lib_dir,# Specify path to psad lib directory.
'Override-config=s' => \$override_config_str,
'test-mode' => \$test_mode, # Used by the test suite.
'help' => \$help, # Display help.
));
&usage(0) if $help;
$fw_search_all = 0 if $no_fw_search_all;
### Everthing after this point must be executed as root.
$< == 0 and $> == 0 or
die '[*] fwcheck_psad.pl: You must be root (or equivalent ',
"UID 0 account) to execute fwcheck_psad.pl! Exiting.\n";
if ($fw_file) {
die "[*] iptables dump file: $fw_file does not exist."
unless -e $fw_file;
}
### import any override config files first
&import_override_configs() if $override_config_str;
### import psad.conf
&import_config($config_file);
$enable_ipv6 = 1 if $config{'ENABLE_IPV6_DETECTION'} eq 'Y';
### import FW_MSG_SEARCH strings
&import_fw_search($config_file);
### expand any embedded vars within config values
&expand_vars();
### check to make sure the commands specified in the config section
### are in the right place, and attempt to correct automatically if not.
&check_commands({});
### import psad perl modules
&import_psad_perl_modules();
open FWCHECK, "> $config{'FW_CHECK_FILE'}" or die "[*] Could not ",
"open $config{'FW_CHECK_FILE'}: $!";
unless ($fw_search_all) {
print FWCHECK "[+] Available search strings in $config_file:\n\n";
print FWCHECK " $_\n" for @fw_search;
print FWCHECK
"\n[+] Additional search strings can be added be specifying more\n",
" FW_MSG_SEARCH lines in $config_file\n\n";
}
### check the iptables policy
my $rv = &fw_check();
close FWCHECK;
exit $rv;
#========================== end main =========================
sub fw_check() {
### only send a firewall config alert if we really need to.
my $send_alert = 0;
my $forward_chain_rv = 1;
my $input_chain_rv = &ipt_chk_chain('INPUT', $cmds{'iptables'});
unless ($input_chain_rv) {
&print_fw_help('INPUT', $cmds{'iptables'});
$send_alert = 1;
}
if ($enable_ipv6) {
my $tmp_rv = &ipt_chk_chain('INPUT', $cmds{'ip6tables'});
unless ($tmp_rv) {
&print_fw_help('INPUT', $cmds{'ip6tables'});
$send_alert = 1;
$input_chain_rv = 0;
}
}
### we don't always have more than one interface or forwarding
### turned on, so we only check the FORWARD iptables chain if we
### do and we have multiple interfaces on the box.
if (&check_forwarding()) {
$forward_chain_rv = &ipt_chk_chain('FORWARD', $cmds{'iptables'});
unless ($forward_chain_rv) {
&print_fw_help('FORWARD', $cmds{'iptables'});
$send_alert = 1;
}
}
if ($send_alert) {
unless ($fw_search_all) {
print FWCHECK
"\n[+] NOTE: IPTables::Parse does not yet parse user defined chains and so\n",
" it is possible your firewall config is compatible with psad anyway.\n";
}
unless ($config{'ALERTING_METHODS'} =~ /no.?e?mail/i or $test_mode) {
&send_mail("[psad-status] firewall setup warning on " .
"$config{'HOSTNAME'}!", $config{'FW_CHECK_FILE'},
$config{'EMAIL_ADDRESSES'},
$cmds{'mail'}
);
}
if ($fw_analyze and not $test_mode) {
print "[-] Errors found in firewall config.\n";
print " emailed to ",
"$config{'EMAIL_ADDRESSES'}\n";
}
} else {
print FWCHECK
"[+] The iptables ruleset on $config{'HOSTNAME'} will log and block unwanted\n",
" packets in both the INPUT and FORWARD chains. Firewall config success!\n";
if ($fw_analyze) {
print "[+] Firewall config looks good.\n",
"[+] Completed check of firewall ruleset.\n";
}
}
if ($fw_analyze) {
print "[+] Results in $config{'FW_CHECK_FILE'}\n",
"[+] Exiting.\n";
}
return $forward_chain_rv and $input_chain_rv;
}
sub print_fw_help() {
my ($chain, $ipt_bin) = @_;
print FWCHECK
"[-] You may just need to add a default logging rule to the $ipt_bin\n",
" '$log_and_drop_table' '$chain' chain on $config{'HOSTNAME'}. For more information,\n",
" see the file \"FW_HELP\" in the psad sources directory or visit:\n\n",
" http://www.cipherdyne.org/psad/docs/fwconfig.html\n\n";
return;
}
sub check_forwarding() {
### check to see if there are multiple interfaces on the
### machine and return false if not since the machine will
### not be able to forward packets anyway (e.g. desktop
### machines). Also return false if forwarding is turned
### off (we have to trust the machine config is as the
### admin wants it).
my $forwarding;
if (-e $config{'PROC_FORWARD_FILE'}) {
open F, "< $config{'PROC_FORWARD_FILE'}"
or die "[*] Could not open $config{'PROC_FORWARD_FILE'}: $!";
$forwarding = <F>;
close F;
chomp $forwarding;
return 0 if $forwarding == 0;
} else {
die "[*] Make sure the path to the IP forwarding file correct.\n",
" The PROC_FORWARD_FILE in $config_file points to\n",
" $config{'PROC_FORWARD_FILE'}";
}
if ($config{'IFCFGTYPE'} =~ /iproute2/i) {
open IFC, "$cmds{'ip'} addr |" or die "[*] Could not ",
"execute: $cmds{'ip'} addr: $!";
my @if_out = <IFC>;
close IFC;
my $intf_name = '';
my $intf_inet_count = 0;
my $num_intf = 0;
for my $line (@if_out) {
if ($line =~ /^\d+:\s+(\S+)\:\s</) {
$intf_name = $1;
if ($intf_inet_count > 0) {
$num_intf++;
}
$intf_inet_count = 0;
next;
}
next if $intf_name eq 'lo';
next if $intf_name =~ /dummy/i;
if ($line =~ /inet\s+/i) {
$intf_inet_count++;
}
}
if ($intf_inet_count > 0) {
$num_intf++;
}
if ($num_intf < 2) {
return 0;
}
} else {
open IFC, "$cmds{'ifconfig'} -a |" or die "[*] Could not ",
"execute: $cmds{'ifconfig'} -a: $!";
my @if_out = <IFC>;
close IFC;
my $num_intf = 0;
for my $line (@if_out) {
if ($line =~ /inet\s+/i and $line !~ /127\.0\.0\.1/) {
$num_intf++;
}
}
if ($num_intf < 2) {
return 0;
}
}
return 1;
}
sub ipt_chk_chain() {
my ($chain, $ipt_bin) = @_;
my $rv = 1;
my $ipt = new IPTables::Parse 'iptables' => $ipt_bin
or die "[*] Could not acquire IPTables::Parse object: $!";
if ($fw_analyze) {
print "[+] Parsing $ipt_bin $chain chain rules.\n";
}
if ($fw_search_all) {
### we are not looking for specific log
### prefixes, but we need _some_ logging rule
my ($ipt_log, $ipt_rv) = $ipt->default_log($log_and_drop_table, $chain, $fw_file);
return 0 unless $ipt_rv;
if (defined $ipt_log->{'all'}) {
### found real default logging rule (assuming it is above a default
### drop rule, which we are not actually checking here).
return 1;
} else {
my $log_protos = '';
my $no_log_protos = '';
for my $proto (qw(tcp udp icmp)) {
if (defined $ipt_log->{$proto}) {
$log_protos .= "$proto/";
} else {
$no_log_protos .= "$proto/";
}
}
$log_protos =~ s|/$||;
$no_log_protos =~ s|/$||;
if ($log_protos) {
print FWCHECK
"[-] Your firewall config on $config{'HOSTNAME'} includes logging rules for\n",
" $log_protos but not for $no_log_protos in the $chain chain.\n\n";
return 0;
} else {
print FWCHECK
"[-] Could not determine whether the $ipt_bin $chain chain is configured with\n",
" a default logging rule on $config{'HOSTNAME'}.\n\n";
return 0;
}
}
} else {
### we are looking for specific log prefixes.
### for now we are only looking at the filter table, so if
### the iptables ruleset includes the log and drop rules in
### a user defined chain then psad will not see this.
my ($ld_hr, $ipt_rv) = $ipt->default_drop($log_and_drop_table,
$chain, $fw_file);
return 0 unless $ipt_rv;
my $num_keys = 0;
if (defined $ld_hr and keys %$ld_hr) {
$num_keys++;
my @protos;
if (defined $ld_hr->{'all'}) {
@protos = (qw(all));
} else {
@protos = (qw(tcp udp icmp));
}
for my $proto (@protos) {
my $str1;
my $str2;
if (! defined $ld_hr->{$proto}->{'LOG'}) {
if ($proto eq 'all') {
$str1 = 'for all protocols';
$str2 = 'scans';
} else {
$str1 = "for the $proto protocol";
$str2 = "$proto scans";
}
print FWCHECK
"[-] The $chain chain in the $ipt_bin ruleset on $config{'HOSTNAME'} does not\n",
" appear to include a default LOG rule $str1. psad will not be able to\n",
" detect $str2 without such a rule.\n\n";
$rv = 0;
}
if (defined $ld_hr->{$proto}->{'LOG'}->{'prefix'}) {
my $found = 0;
for my $fwstr (@fw_search) {
$found = 1
if $ld_hr->{$proto}->{'LOG'}->{'prefix'} =~ /$fwstr/;
}
unless ($found) {
if ($proto eq 'all') {
$str1 = "[-] The $chain chain in the $ipt_bin ruleset " .
"on $config{'HOSTNAME'} includes a default\n LOG rule for " .
"all protocols,";
$str2 = 'scans';
} else {
$str1 = "[-] The $chain chain in the $ipt_bin ruleset " .
"on $config{'HOSTNAME'} inclues a default\n LOG rule for " .
"the $proto protocol,";
$str2 = "$proto scans";
}
print FWCHECK
"$str1\n",
" but the rule does not include one of the log prefixes mentioned above.\n",
" It appears as though the log prefix is set to \"$ld_hr->{$proto}->{'LOG'}->{'prefix'}\"\n",
" psad will not be able to detect $str2 without adding one of the above\n",
" logging prefixes to the rule.\n\n";
$rv = 0;
}
}
if (! defined $ld_hr->{$proto}->{'DROP'}) {
if ($proto eq 'all') {
$str1 = "for all protocols";
} else {
$str1 = "for the $proto protocol";
}
print FWCHECK
"[-] The $chain chain in the $ipt_bin ruleset on $config{'HOSTNAME'} does not\n",
" appear to include a default DROP rule $str1.\n\n";
$rv = 0;
}
}
}
### make sure there was _something_ returned from the IPTables::Parse
### module.
return 0 unless $num_keys > 0;
}
return $rv;
}
sub import_psad_perl_modules() {
my $mod_paths_ar = &get_psad_mod_paths();
if ($#$mod_paths_ar > -1) { ### /usr/lib/psad/ exists
push @$mod_paths_ar, @INC;
splice @INC, 0, $#$mod_paths_ar+1, @$mod_paths_ar;
}
require IPTables::Parse;
return;
}
sub get_psad_mod_paths() {
my @paths = ();
$config{'PSAD_LIBS_DIR'} = $psad_lib_dir if $psad_lib_dir;
unless (-d $config{'PSAD_LIBS_DIR'}) {
my $dir_tmp = $config{'PSAD_LIBS_DIR'};
$dir_tmp =~ s|lib/|lib64/|;
if (-d $dir_tmp) {
$config{'PSAD_LIBS_DIR'} = $dir_tmp;
} else {
return [];
}
}
opendir D, $config{'PSAD_LIBS_DIR'}
or die "[*] Could not open $config{'PSAD_LIBS_DIR'}: $!";
my @dirs = readdir D;
closedir D;
push @paths, $config{'PSAD_LIBS_DIR'};
for my $dir (@dirs) {
### get directories like "/usr/lib/psad/x86_64-linux"
next unless -d "$config{'PSAD_LIBS_DIR'}/$dir";
push @paths, "$config{'PSAD_LIBS_DIR'}/$dir"
if $dir =~ m|linux| or $dir =~ m|thread|
or (-d "$config{'PSAD_LIBS_DIR'}/$dir/auto");
}
return \@paths;
}
sub import_fw_search() {
my $config_file = shift;
open F, "< $config_file" or die "[*] Could not open fw search ",
"string file $config_file: $!";
my @lines = <F>;
close F;
for my $line (@lines) {
next unless $line =~ /\S/;
next if $line =~ /^\s*#/;
if ($line =~ /^\s*FW_MSG_SEARCH\s+(.*?);/) {
push @fw_search, $1;
}
}
return;
}
### send mail message to all addresses contained in the
### EMAIL_ADDRESSES variable within psad.conf ($addr_str).
### TODO: Would it be better to use Net::SMTP here?
sub send_mail() {
my ($subject, $body_file, $addr_str, $mailCmd) = @_;
open MAIL, "| $mailCmd -s \"$subject\" $addr_str > /dev/null" or die
"[*] Could not send mail: $mailCmd -s \"$subject\" $addr_str: $!";
if ($body_file) {
open F, "< $body_file" or die "[*] Could not open mail file: ",
"$body_file: $!";
my @lines = <F>;
close F;
print MAIL for @lines;
}
close MAIL;
return;
}
sub import_override_configs() {
my @override_configs = split /,/, $override_config_str;
for my $file (@override_configs) {
die "[*] Override config file $file does not exist"
unless -e $file;
&import_config($file);
}
return;
}
sub import_config() {
my $conf_file = shift;
open C, "< $conf_file" or die "[*] Could not open " .
"config file $conf_file: $!";
my @lines = <C>;
close C;
for my $line (@lines) {
chomp $line;
next if ($line =~ /^\s*#/);
if ($line =~ /^\s*(\S+)\s+(.*?)\;/) {
my $varname = $1;
my $val = $2;
if ($val =~ m|/.+| and $varname =~ /^\s*(\S+)Cmd$/) {
### found a command
$cmds{$1} = $val unless defined $cmds{$1};
} else {
$config{$varname} = $val unless defined $config{$varname};
}
}
}
return;
}
sub expand_vars() {
my $has_sub_var = 1;
my $resolve_ctr = 0;
while ($has_sub_var) {
$resolve_ctr++;
$has_sub_var = 0;
if ($resolve_ctr >= 20) {
die "[*] Exceeded maximum variable resolution counter.";
}
for my $hr (\%config, \%cmds) {
for my $var (keys %$hr) {
my $val = $hr->{$var};
if ($val =~ m|\$(\w+)|) {
my $sub_var = $1;
die "[*] sub-ver $sub_var not allowed within same ",
"variable $var" if $sub_var eq $var;
if (defined $config{$sub_var}) {
if ($sub_var eq 'INSTALL_ROOT'
and $config{$sub_var} eq '/') {
$val =~ s|\$$sub_var||;
} else {
$val =~ s|\$$sub_var|$config{$sub_var}|;
}
$hr->{$var} = $val;
} else {
die "[*] sub-var \"$sub_var\" not defined in ",
"config for var: $var."
}
$has_sub_var = 1;
}
}
}
}
return;
}
### check paths to commands and attempt to correct if any are wrong.
sub check_commands() {
my $exceptions_hr = shift;
my $caller = $0;
my @path = (qw(
/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin
));
CMD: for my $cmd (keys %cmds) {
### both mail and sendmail are special cases, mail is not required
### if "nomail" is set in REPORT_METHOD, and sendmail is only
### required if DShield alerting is enabled and a DShield user
### email is set.
if ($cmd eq 'mail') {
next CMD if $config{'ALERTING_METHODS'} =~ /no.?e?mail/i;
} elsif ($cmd eq 'sendmail') {
next CMD unless ($config{'ENABLE_DSHIELD_ALERTS'} eq 'Y'
and $config{'DSHIELD_ALERT_EMAIL'} ne 'NONE');
}
next if $cmd eq 'wget'; ### only used in --sig-update mode
unless (-x $cmds{$cmd}) {
my $found = 0;
PATH: for my $dir (@path) {
if (-x "${dir}/${cmd}") {
$cmds{$cmd} = "${dir}/${cmd}";
$found = 1;
last PATH;
}
}
unless ($found) {
unless (defined $exceptions_hr->{$cmd}) {
die "[*] ($caller): Could not find $cmd ",
"anywhere!!!\n Please edit the config section ",
"to include the path to $cmd.";
}
}
}
unless (-x $cmds{$cmd}) {
unless (defined $exceptions_hr->{$cmd}) {
die "[*] ($caller): $cmd is located at ",
"$cmds{$cmd}, but is not executable\n",
" by uid: $<";
}
}
}
return;
}
sub usage() {
my $exitcode = shift;
print <<_HELP_;
Options:
--config <config_file> - Specify path to configuration
file.
--fw-file <fw_file> - Analyze ruleset contained within
fw_file instead of a running
policy.
--fw-analyze - Analyze the local iptables
ruleset and exit.
--no-fw-search-all - looking for specific log
prefixes.
--Lib-dir <dir> - Path to the psad lib directory.
--test-mode - Enable test mode (used by the
test suite).
--help - Display help.
_HELP_
exit $exitcode;
}
Jump to Line
Something went wrong with that request. Please try again.