run with least privilege, support pf

* run the service as a low privilege user and use sudo/doas to add
      the block rules
    * add support for pf firewall
    * write documentation for the above
    * add abort function for handling error logging and exit cleanup

README.md

@@ -7,9 +7,35 @@ To deploy:
 
 * modify the configuration variables in the scripts
 * copy the scripts to `/usr/local/bin`
+* create the user
+
+        useradd -s /sbin/nologin _forumspam
+
+* if using `pf`:
+    * create appropriate permissions for the file:
+
+        install -m 640 -o _forumspam -g wheel /dev/null /etc/pf-forumspam.txt
+
+    * add the following to `/etc/pf.conf`, preferably high up in the ruleset:
+
+        table <forumspam> persist file "/etc/pf-forumspam.txt"
+        block in quick on egress from <forumspam>
+        block out quick on egress to <forumspam>
+
+* set up sudo or doas:
+    * for doas:
+        * add the following to `/etc/doas.conf`:
+
+        permit nopass _forumspam cmd pfctl args -nf /etc/pf.conf
+        permit nopass _forumspam cmd pfctl args -t forumspam -T replace -f /etc/pf-forumspam.txt
+
+    * for sudo:
+        * add to your sudo config file:
+          `Cmnd_Alias FIREWALL = /usr/sbin/ufw, /sbin/iptables`
+          and `_forumspam ALL = NOPASSWD: FIREWALL`
+
 * register `q2a_usercheck.sh` as a systemd unit or rc script
 
 TODO:
 * also check against [botscout](http://botscout.com/api.htm)
-* add support for pf
-* add support for iptables
+* give the scripts more sensible names

forumspam.sh

@@ -2,31 +2,53 @@
 
 # API reference: https://www.stopforumspam.com/usage
 
+# user configuration area - change as needed
+ostype="bsd" # allowed options are bsd, linux
+logf=/var/log/forumspam.log
+limit=0 # number of violations allowed before blocking the ip
+
+case "$ostype" in
+    bsd)
+        getroot="doas"
+        fw_cmd="pfctl"
+        ;;
+    linux)
+        getroot="sudo"
+        fw_cmd="ufw"
+        ;;
+esac
+
+abort() {
+    echo `date` 'error:' $* >> $logf
+	rm $repl
+    exit 1
+}
+block_ip() {
+    case "$fw_cmd" in
+        ufw)
+            if [ "$getroot" ufw deny from $ip >/dev/null 2>>$logf ]; then
+                echo `date` blocked ip $ip with freq $freq >> $logf
+            else
+                abort "failed to block ip $ip"
+            fi
+            ;;
+        pfctl)
+            "$getroot" pfctl -nf /etc/pf.conf || abort "pf config check failed"   # Ensure proposed changes are valid before reloading table
+            "$getroot" pfctl -t forumspam -T replace -f /etc/pf-forumspam.txt
+            ;;
+    esac
+}
+
+# we ignore all arguments except the first
 ip=$1
 repl=`mktemp`
-logf=/var/log/forumspam.log
-
 curl 'http://api.stopforumspam.org/api?ip='$ip 2>/dev/null > $repl
 
 if ! grep -q '<response success="true">' $repl; then
-	echo error failed to query stopforumspam api >> $logf
-	rm $repl
-	exit 1
-fi
-if ! grep -q '<appears>yes</appears>' $repl; then
-	rm $repl
-	exit 0
+	abort 'error failed to query stopforumspam api'
 fi
 freq=`grep '<frequency>' $repl | sed 's/<frequency>//; s!</frequency>!!'`
-if [ "$freq" -ge 1 ]; then
-	if ufw deny from $ip >/dev/null 2>>$logf; then
-		echo `date` blocked ip $ip with freq $freq >> $logf
-		rm $repl
-		exit 0
-	else
-		echo `date` "error failed to block ip $ip" >> $logf
-		rm $repl
-		exit 2
-	fi
+if grep -q '<appears>yes</appears>' $repl && [ "$freq" -gt "$limit" ]; then
+    block_ip "$ip"
 fi
 rm $repl