Add routeback protection

Signed-off-by: Tom Eastep <teastep@shorewall.net>

Shorewall/Perl/Shorewall/Accounting.pm

@@ -158,7 +158,7 @@ sub process_accounting_rule( ) {
     our $disposition = '';
 
     sub reserved_chain_name($) {
-	$_[0] =~ /^acc(?:ount(?:fwd|in|ing|out)|ipsecin|ipsecout)$/;
+	$_[0] =~ /^acc(?:ount(?:fwd|in|ing|out|pre|post)|ipsecin|ipsecout)$/;
     }
 
     sub ipsec_chain_name($) {

Shorewall/Perl/Shorewall/Compiler.pm

@@ -763,6 +763,10 @@ sub compiler {
     #
     setup_mac_lists 1;
     #
+    # Prevent Hairpins on non-routeback interfaces 
+    #
+    prevent_hairpins;
+    #
     # Process the rules file.
     #
     process_rules;

Shorewall/Perl/Shorewall/Config.pm

@@ -447,6 +447,7 @@ sub initialize( $ ) {
 	  LOG_MARTIANS => undef,
 	  LOG_VERBOSITY => undef,
 	  STARTUP_LOG => undef,
+	  ROUTEBACK_LOG_LEVEL => undef,
 	  #
 	  # Location of Files
 	  #
@@ -550,6 +551,7 @@ sub initialize( $ ) {
 	  TCP_FLAGS_DISPOSITION => undef,
 	  BLACKLIST_DISPOSITION => undef,
 	  SMURF_DISPOSITION => undef,
+	  ROUTEBACK_DISPOSITION => undef,
 	  #
 	  # Mark Geometry
 	  #
@@ -3377,6 +3379,14 @@ sub get_configuration( $ ) {
     default_log_level 'SMURF_LOG_LEVEL',     '';
     default_log_level 'LOGALLNEW',           '';
 
+    default_log_level 'ROUTEBACK_LOG_LEVEL', 'info';
+    
+    if ( $val = $config{ROUTEBACK_DISPOSITION} ) {
+	fatal_error "Invalid ROUTEBACK_DISPOSITION setting ($val)" unless $val =~ /^(?:A_)?DROP$/;
+    } else {
+	$config{ROUTEBACK_DISPOSITION} = 'DROP';
+    }
+
     if ( $val = $config{MACLIST_DISPOSITION} ) {
 	if ( $val =~ /^(?:A_)?DROP$/ ) {
 	    $globals{MACLIST_TARGET} = $val;

Shorewall/Perl/Shorewall/Proc.pm

@@ -106,7 +106,7 @@ sub setup_route_filtering() {
 
 	my $val = '';
 
-	if ( $config{ROUTE_FILTER} ne '' ) {
+	if ( $config ne '' ) {
 	    $val = $config eq 'on' ? 1 : $config eq 'off' ? 0 : $config;
 
 	    emit ( 'for file in /proc/sys/net/ipv4/conf/*; do',

Shorewall/Perl/Shorewall/Rules.pm

@@ -49,6 +49,7 @@ our @EXPORT = qw(
 		  process_actions
 		  process_rules
 		  verify_audit
+		  prevent_hairpins
 	       );
 
 our @EXPORT_OK = qw( initialize );
@@ -650,6 +651,8 @@ sub complete_standard_chain ( $$$$ ) {
     policy_rules $stdchainref , $policy , $loglevel, $defaultaction, 0;
 }
 
+sub require_audit($$);
+
 #
 # Create and populate the synflood chains corresponding to entries in /etc/shorewall/policy
 #
@@ -1183,6 +1186,45 @@ sub require_audit($$) {
     return ensure_audit_chain $target, $action;
 }   
   
+#
+# Generate rules to prevent hairpins
+#
+sub prevent_hairpins() {
+    my $loglevel = $config{ROUTEBACK_LOG_LEVEL};
+    my $target   = $config{ROUTEBACK_DISPOSITION};
+    my $audit    = $target eq 'A_DROP';
+
+    require_capability 'AUDIT_TARGET' , 'ROUTEBACK_DISPOSITION=A_DROP', 's' if $audit;
+    
+    if ( $loglevel ) {
+	my $chainref = new_standard_chain 'routeback';
+	log_rule $loglevel , $chainref , $target, '';
+
+	if ( $audit ) {
+	    if ( $config{FAKE_AUDIT} ) {
+		add_jump( $chainref, 'AUDIT', 0, '-m comment --comment "--type drop"' , 0 );
+	    } else {
+		add_rule $chainref, 'AUDIT --type drop';
+	    }
+	}
+	
+	add_jump $chainref, $target, 1;
+	$target = $chainref;
+    } else {
+	$target = require_audit( 'DROP', $audit ? 'audit' : '' );
+    }
+
+    for my $interface (all_interfaces) {
+	my $interfaceref = find_interface( $interface );
+       
+	add_jump( $filter_table->{forward_chain $interface},
+		  $target,
+		  1,
+		  match_dest_dev( $interface ) )
+	    unless $interfaceref->{routefilter} || $interfaceref->{options}{routeback} || $interfaceref->{options}{ignore};
+    }
+}
+
 #
 # The following small functions generate rules for the builtin actions of the same name
 #

Shorewall/changelog.txt

@@ -4,6 +4,8 @@ Changes in Shorewall 4.4.20 Beta 5
 
 2)  Add -T option to compile and check
 
+3)  Implement ROUTEBACK_LOG_LEVEL and ROUTEBACK_AUDIT
+
 Changes in Shorewall 4.4.20 Beta 4
 
 1)  Smarten up the tc devnum algorithm.

Shorewall/configfiles/shorewall.conf

@@ -45,6 +45,8 @@ SMURF_LOG_LEVEL=info
 
 LOG_MARTIANS=Yes
 
+ROUTEBACK_LOG_LEVEL=info
+
 ###############################################################################
 #	L O C A T I O N	  O F	F I L E S   A N D   D I R E C T O R I E S
 ###############################################################################
@@ -212,4 +214,6 @@ TCP_FLAGS_DISPOSITION=DROP
 
 SMURF_DISPOSITION=DROP
 
+ROUTEBACK_DISPOSITION=DROP
+
 #LAST LINE -- DO NOT REMOVE

Shorewall/releasenotes.txt

@@ -19,6 +19,33 @@ VI.   PROBLEMS CORRECTED AND NEW FEATURES IN PRIOR RELEASES
     did not specify a number. Now, the compiler selects the lowest
     unallocated number when no device number is explicitly allocated.
 
+2)  Eric Leblond, creator of NuFW, has discovered an exploit that
+    allows locally-connected hosts to poke holes in the firewall. The
+    known ways to protect against the exploit are:
+
+    a)  rt_filter (Shorewall's routefilter). Only applicable to IPv4.
+    b)  Insert a DROP rule that prevents hairpinning (routeback). The rule
+        must be inserted before any RELATED firewall rules.  This 
+        approach is not appropriate for bridges.
+
+    To deal with this issue, Shorewall will insert a hairpin-prevention
+    rule for each interface that has none of these options:
+
+    - ignore
+    - routeback
+    - routefilter
+         
+    To control logging and auditing of these DROP operations, two new
+    options are added to shorewall.conf (shorewall6.conf):
+
+    - ROUTEBACK_LOG_LEVEL - Default is 'info'. If you don't want these
+                            DROPs logged, set ROUTEBACK_LOG_LEVEL=none
+
+    - ROUTEBACK_AUDIT     - Defaults to 'No'; 'Yes' causes auditing.
+
+    This leaves IPv6 bridges still unprotected unless each of its ports 
+    is described as bridge ports in /etc/shorewall/interfaces.
+
 ----------------------------------------------------------------------------
            I I.  K N O W N   P R O B L E M S   R E M A I N I N G
 ----------------------------------------------------------------------------

Shorewall6/shorewall6.conf

@@ -42,6 +42,8 @@ TCP_FLAGS_LOG_LEVEL=info
 
 SMURF_LOG_LEVEL=info
 
+ROUTEBACK_LOG_LEVEL=info
+
 ###############################################################################
 #	L O C A T I O N	  O F	F I L E S   A N D   D I R E C T O R I E S
 ###############################################################################
@@ -173,4 +175,6 @@ TCP_FLAGS_DISPOSITION=DROP
 
 SMURF_DISPOSITION=DROP
 
+ROUTEBACK_DISPOSITION=DROP
+
 #LAST LINE -- DO NOT REMOVE