wg-quick: linux: filter bogus injected packets and don't disable rpfilter

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/wg-quick/linux.bash b/src/wg-quick/linux.bash
index cf72d41ef89a74919d54ecd6582fbd23739a119c..0764dc6ec09c504a907504d36f0c1b392741c50a 100755 (executable)
--- a/src/wg-quick/linux.bash
+++ b/src/wg-quick/linux.bash
@@ -95,6 +95,7 @@ add_if() {
 del_if() {
        local table
        [[ $HAVE_SET_DNS -eq 0 ]] || unset_dns
+       [[ $HAVE_SET_IPTABLES -eq 0 ]] || remove_iptables
        if [[ -z $TABLE || $TABLE == auto ]] && get_fwmark table && [[ $(wg show "$INTERFACE" allowed-ips) =~ /0(\ |$'\n'|$) ]]; then
                while [[ $(ip -4 rule show) == *"lookup $table"* ]]; do
                        cmd ip -4 rule delete table $table
@@ -180,8 +181,22 @@ get_fwmark() {
        return 0
 }
 
+remove_iptables() {
+       local line iptables found restore
+       for iptables in iptables ip6tables; do
+               restore="" found=0
+               while read -r line; do
+                       [[ $line == "*"* || $line == COMMIT || $line == "-A "*"-m comment --comment \"wg-quick(8) rule for $INTERFACE\""* ]] || continue
+                       [[ $line == "-A"* ]] && found=1
+                       printf -v restore '%s\n%s' "$restore" "${line/#-A/-D}"
+               done < <($iptables-save)
+               [[ $found -eq 1 ]] && echo "$restore" | cmd $iptables-restore -nw
+       done
+}
+
+HAVE_SET_IPTABLES=0
 add_default() {
-       local table proto key value
+       local table proto i iptables
        if ! get_fwmark table; then
                table=51820
                while [[ -n $(ip -4 route show table $table) || -n $(ip -6 route show table $table) ]]; do
@@ -189,16 +204,21 @@ add_default() {
                done
                cmd wg set "$INTERFACE" fwmark $table
        fi
-       proto=-4
-       [[ $1 == *:* ]] && proto=-6
+       proto=-4 iptables=iptables
+       [[ $1 == *:* ]] && proto=-6 iptables=ip6tables
        cmd ip $proto route add "$1" dev "$INTERFACE" table $table
        cmd ip $proto rule add not fwmark $table table $table
        cmd ip $proto rule add table main suppress_prefixlength 0
-       if [[ $proto == -4 ]]; then
-               while read -r key _ value; do
-                       [[ $value -eq 1 ]] && sysctl -q "$key=2"
-               done < <(sysctl -a -r '^net\.ipv4.conf\.[^ .=]+\.rp_filter$')
-       fi
+
+       local marker="-m comment --comment \"wg-quick(8) rule for $INTERFACE\"" restore="*raw"
+       for i in "${ADDRESSES[@]}"; do
+               [[ ( $proto == -4 && $i != *:* ) || ( $proto == -6 && $i == *:* ) ]] || continue
+               printf -v restore '%s\n-I PREROUTING ! -i %s -d %s -m addrtype ! --src-type LOCAL -j DROP %s\n' "$restore" "$INTERFACE" "${i%/*}" "$marker"
+       done
+       printf -v restore '%s\nCOMMIT\n*mangle\n-I POSTROUTING -m mark --mark %d -p udp -j CONNMARK --save-mark %s\n-I PREROUTING -p udp -j CONNMARK --restore-mark %s\nCOMMIT\n' "$restore" $table "$marker" "$marker"
+       [[ $proto == -4 ]] && cmd sysctl -q net.ipv4.conf.all.src_valid_mark=1
+       echo "$restore" | cmd $iptables-restore -nw
+       HAVE_SET_IPTABLES=1
        return 0
 }
 
@@ -303,6 +323,7 @@ cmd_down() {
        [[ $SAVE_CONFIG -eq 0 ]] || save_config
        del_if
        unset_dns
+       remove_iptables
        execute_hooks "${POST_DOWN[@]}"
 }