feat: iplist2rule utility command

.github/actions/spelling/allow.txt

@@ -18,3 +18,7 @@
 pseudoprofound
 reimagining
 iocaine
+admins
+fout
+iplist
+NArg

docs/docs/CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Add iplist2rule tool that lets admins turn an IP address blocklist into an Anubis ruleset.
 - Add Polish locale ([#1292](https://github.com/TecharoHQ/anubis/pull/1309))
 
 <!-- This changes the project to: -->

utils/cmd/iplist2rule/blocklist.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net/http"
+	"net/netip"
+	"strings"
+)
+
+// FetchBlocklist reads the blocklist over HTTP and returns every non-commented
+// line parsed as an IP address in CIDR notation. IPv4 addresses are returned as
+// /32, IPv6 addresses as /128.
+//
+// This function was generated with GLM 4.7.
+func FetchBlocklist(url string) ([]string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP request failed with status: %s", resp.Status)
+	}
+
+	var lines []string
+	scanner := bufio.NewScanner(resp.Body)
+	for scanner.Scan() {
+		line := scanner.Text()
+		// Skip empty lines and comments (lines starting with #)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		addr, err := netip.ParseAddr(line)
+		if err != nil {
+			// Skip lines that aren't valid IP addresses
+			continue
+		}
+
+		var cidr string
+		if addr.Is4() {
+			cidr = fmt.Sprintf("%s/32", addr.String())
+		} else {
+			cidr = fmt.Sprintf("%s/128", addr.String())
+		}
+		lines = append(lines, cidr)
+	}
+
+	if err := scanner.Err(); err != nil && err != io.EOF {
+		return nil, err
+	}
+
+	return lines, nil
+}

utils/cmd/iplist2rule/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/TecharoHQ/anubis/lib/config"
+	"github.com/facebookgo/flagenv"
+	"sigs.k8s.io/yaml"
+)
+
+type Rule struct {
+	Name       string         `yaml:"name" json:"name"`
+	Action     config.Rule    `yaml:"action" json:"action"`
+	RemoteAddr []string       `json:"remote_addresses,omitempty" yaml:"remote_addresses,omitempty"`
+	Weight     *config.Weight `json:"weight,omitempty" yaml:"weight,omitempty"`
+}
+
+func init() {
+	flag.Usage = func() {
+		fmt.Printf(`Usage of %[1]s:
+
+	%[1]s [--action=DENY|ALLOW] [--rule-name=] <blocklist-url> <filename>
+
+Grabs the contents of the blocklist, converts it to an Anubis ruleset, and writes it to filename.
+`, filepath.Base(os.Args[0]))
+	}
+}
+
+var (
+	action         = flag.String("action", "DENY", "Anubis action to take (ALLOW / DENY)")
+	manualRuleName = flag.String("rule-name", "", "If set, prefer this name over inferring from filename")
+	weight         = flag.Int("weight", 0, "If set to any number, add/subtract this many weight points when --action=WEIGH")
+)
+
+func main() {
+	flagenv.Parse()
+	flag.Parse()
+
+	if flag.NArg() != 2 {
+		flag.Usage()
+		os.Exit(2)
+	}
+
+	blocklistURL := flag.Arg(0)
+	foutName := flag.Arg(1)
+	ruleName := strings.TrimSuffix(foutName, filepath.Ext(foutName))
+
+	if *manualRuleName != "" {
+		ruleName = *manualRuleName
+	}
+
+	ruleAction := config.Rule(*action)
+	if err := ruleAction.Valid(); err != nil {
+		log.Fatalf("--action=%q is invalid: %v", *action, err)
+	}
+
+	result := &Rule{
+		Name:   ruleName,
+		Action: ruleAction,
+	}
+
+	if *weight != 0 {
+		if ruleAction != config.RuleWeigh {
+			log.Fatalf("used --weight=%d but --action=%s", *weight, *action)
+		}
+
+		result.Weight = &config.Weight{
+			Adjust: *weight,
+		}
+	}
+
+	ips, err := FetchBlocklist(blocklistURL)
+	if err != nil {
+		log.Fatalf("can't fetch blocklist %s: %v", blocklistURL, err)
+	}
+
+	result.RemoteAddr = ips
+
+	fout, err := os.Create(foutName)
+	if err != nil {
+		log.Fatalf("can't create output file %q: %v", foutName, err)
+	}
+
+	defer fout.Close()
+
+	data, err := yaml.Marshal([]*Rule{result})
+	if err != nil {
+		log.Fatalf("can't marshal yaml")
+	}
+
+	fout.Write(data)
+}