housecarl/cmd/hc/firewall.go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"os/exec"
	"sort"
	"strings"
	"time"

	"github.com/spf13/cobra"

	"housecarl/internal/api"
	"housecarl/internal/model"
)

func jsonUnmarshal(b []byte, v any) error { return json.Unmarshal(b, v) }

// ---- status

func statusCmd() *cobra.Command {
	return &cobra.Command{
		Use: "status", Short: "Show the firewall's state: ruleset, probation, problems, interfaces", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			st, err := get[api.Status]("/status", nil)
			if err != nil {
				return err
			}
			return output(st, func(w io.Writer) {
				fmt.Fprintf(w, "Housecarl:\t%s, up since %s\n", st.Build.Label, st.Started.Local().Format("2006-01-02 15:04"))
				if st.Applied {
					fmt.Fprintln(w, "Ruleset:\tin force (table inet housecarl)")
				} else if st.Unconfigured {
					fmt.Fprintln(w, "Ruleset:\tnone yet: the configuration is empty (add rules, or 'hc import')")
				} else {
					fmt.Fprintf(w, "Ruleset:\tNOT in force: %s\n", st.ApplyError)
				}
				if len(st.Probation.Pending) > 0 {
					n := len(st.Probation.Pending)
					what := map[bool]string{true: "1 change rolls", false: fmt.Sprintf("%d changes roll", n)}[n == 1]
					fmt.Fprintf(w, "Probation:\t%s back in %ds unless confirmed ('hc confirm')\n", what, st.Probation.SecondsLeft)
				}
				if len(st.OtherTables) > 0 {
					fmt.Fprintf(w, "Other tables:\t%s (not Housecarl's; 'hc takeover' deletes them once replaced)\n", strings.Join(st.OtherTables, ", "))
				}
				var counts []string
				for _, k := range model.Kinds {
					counts = append(counts, fmt.Sprintf("%d %ss", st.Counts[k], k))
				}
				fmt.Fprintf(w, "Configuration:\t%s\n", strings.Join(counts, ", "))
				fmt.Fprintln(w, "Interfaces:")
				for _, i := range st.Interfaces {
					state := "down"
					if i.Up {
						state = "up"
					}
					fmt.Fprintf(w, "  %s\t%s\tzone %s\t%s\n", i.Name, state, orDash(i.Zone), strings.Join(i.Addresses, ", "))
				}
				if len(st.Problems) > 0 {
					fmt.Fprintln(w, "Problems:")
					for _, p := range st.Problems {
						fmt.Fprintf(w, "  %s:\t%s: %s [%s]\n", p.Severity, p.Object, p.Message, p.Code)
					}
				}
			})
		},
	}
}

func interfaceCmd() *cobra.Command {
	return &cobra.Command{
		Use: "interfaces", Aliases: []string{"interface"}, Short: "List the machine's interfaces and their zones", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			ifs, err := get[[]api.HostInterface]("/interfaces", nil)
			if err != nil {
				return err
			}
			return output(ifs, func(w io.Writer) {
				fmt.Fprintln(w, "INTERFACE\tSTATE\tZONE\tADDRESSES")
				for _, i := range ifs {
					state := "down"
					if i.Up {
						state = "up"
					}
					fmt.Fprintf(w, "%s\t%s\t%s\t%s\n", i.Name, state, orDash(i.Zone), orDash(strings.Join(i.Addresses, ", ")))
				}
			})
		},
	}
}

// ---- settings

func settingsCmd() *cobra.Command {
	cmd := &cobra.Command{Use: "settings", Short: "Policies, built-in rules and other firewall-wide settings"}
	cmd.AddCommand(&cobra.Command{
		Use: "show", Short: "Show the settings", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			s, err := get[model.Settings]("/settings", nil)
			if err != nil {
				return err
			}
			return output(s, func(w io.Writer) {
				fmt.Fprintf(w, "Policies:\tinput %s, forward %s, output %s\n", s.InputPolicy, s.ForwardPolicy, s.OutputPolicy)
				fmt.Fprintf(w, "Log policy drops:\t%s\n", yesNo(s.LogPolicyDrops))
				b, _ := json.Marshal(s.Builtins)
				var m map[string]bool
				json.Unmarshal(b, &m)
				var names []string
				for n := range m {
					names = append(names, n)
				}
				sort.Strings(names)
				for i, n := range names {
					label := ""
					if i == 0 {
						label = "Built-ins:"
					}
					fmt.Fprintf(w, "%s\t%s %s\n", label, n, map[bool]string{true: "on", false: "off"}[m[n]])
				}
				fmt.Fprintf(w, "Own prefixes:\t%s\n", list(s.OwnPrefixes))
				fmt.Fprintf(w, "Antispoof IPv4:\t%s\n", list(s.AntispoofV4))
				fmt.Fprintf(w, "Antispoof IPv6:\t%s\n", list(s.AntispoofV6))
				fmt.Fprintf(w, "Flowtable:\t%s\n", list(s.FlowtableDevices))
				fmt.Fprintf(w, "Probation:\t%s\n", fmtSeconds(s.Probation()))
			})
		},
	})
	var input, forward, output, logDrops, probation string
	var builtins, own, flowtable, spoof4, spoof6 []string
	set := &cobra.Command{
		Use: "set [flags]", Short: "Change settings (only the flags given)", Args: cobra.NoArgs,
		Long: `Changes the settings. Built-ins are rules Housecarl adds itself; each can be
turned off: loopback, established, drop_invalid, icmpv6, ping_internal,
dhcpv6_client, antispoof, mss_clamp.

  hc settings set --builtin mss_clamp=on --own-prefix 2a02:8013:7f3d::/48
  hc settings set --forward-policy drop --log-drops on
  hc settings set --flowtable wan --flowtable enp2s0`,
		RunE: func(cmd *cobra.Command, args []string) error {
			fl := cmd.Flags()
			p := patch{}
			for flag, field := range map[string]string{"input-policy": "input_policy", "forward-policy": "forward_policy", "output-policy": "output_policy"} {
				if fl.Changed(flag) {
					v, _ := fl.GetString(flag)
					p[field] = v
				}
			}
			if fl.Changed("log-drops") {
				on, err := onOff("log-drops", logDrops)
				if err != nil {
					return err
				}
				p["log_policy_drops"] = on
			}
			if len(builtins) > 0 {
				b := map[string]bool{}
				for _, x := range builtins {
					k, v, ok := strings.Cut(x, "=")
					on, err := onOff("builtin "+k, v)
					if !ok || err != nil {
						return fmt.Errorf("--builtin %q: write it as NAME=on or NAME=off", x)
					}
					b[strings.ReplaceAll(k, "-", "_")] = on
				}
				p["builtins"] = b
			}
			for flag, v := range map[string][]string{"own-prefix": own, "flowtable": flowtable, "antispoof-v4": spoof4, "antispoof-v6": spoof6} {
				if fl.Changed(flag) {
					p[map[string]string{"own-prefix": "own_prefixes", "flowtable": "flowtable_devices", "antispoof-v4": "antispoof_v4", "antispoof-v6": "antispoof_v6"}[flag]] = v
				}
			}
			if fl.Changed("probation") {
				n, err := parseSeconds(probation)
				if err != nil {
					return err
				}
				p["probation_seconds"] = n
			}
			return change("PATCH", "/settings", p)
		},
	}
	f := set.Flags()
	f.StringVar(&input, "input-policy", "", "accept or drop what no rule decided, to the firewall")
	f.StringVar(&forward, "forward-policy", "", "… through it")
	f.StringVar(&output, "output-policy", "", "… from it")
	f.StringVar(&logDrops, "log-drops", "", "log what the input and forward policies drop: on or off")
	f.StringArrayVar(&builtins, "builtin", nil, "turn a built-in on or off: NAME=on|off (repeat)")
	f.StringArrayVar(&own, "own-prefix", nil, "your public prefixes, for antispoofing (repeat; replaces)")
	f.StringArrayVar(&flowtable, "flowtable", nil, "fast-path devices (repeat; replaces; none: off)")
	f.StringArrayVar(&spoof4, "antispoof-v4", nil, "IPv4 sources dropped from the internet (replaces)")
	f.StringArrayVar(&spoof6, "antispoof-v6", nil, "IPv6 sources dropped from the internet (replaces)")
	f.StringVar(&probation, "probation", "", "how long a network change has to be confirmed (2m)")
	cmd.AddCommand(set)
	return cmd
}

func onOff(name, v string) (bool, error) {
	switch strings.ToLower(v) {
	case "on", "yes", "true":
		return true, nil
	case "off", "no", "false":
		return false, nil
	}
	return false, fmt.Errorf("--%s: use on or off", name)
}

// ---- the ruleset, counters, the log

func rulesetCmd() *cobra.Command {
	return &cobra.Command{
		Use: "ruleset", Short: "Print the nftables ruleset Housecarl builds", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			var text string
			if err := c.Do(ctx(), "GET", "/ruleset", nil, nil, &text); err != nil {
				return err
			}
			fmt.Print(text)
			return nil
		},
	}
}

func countersCmd() *cobra.Command {
	return &cobra.Command{
		Use: "counters", Short: "Hits of every rule, NAT rule and built-in", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			cs, err := get[api.Counters]("/counters", nil)
			if err != nil {
				return err
			}
			return output(cs, func(w io.Writer) {
				fmt.Fprintf(w, "Since %s\n", cs.Since.Local().Format("2006-01-02 15:04"))
				fmt.Fprintln(w, "MARK\tPACKETS\tBYTES")
				var marks []string
				for m := range cs.Counters {
					marks = append(marks, m)
				}
				sort.Strings(marks)
				for _, m := range marks {
					c := cs.Counters[m]
					fmt.Fprintf(w, "%s\t%d\t%d\n", m, c.Packets, c.Bytes)
				}
			})
		},
	}
}

func logCmd() *cobra.Command {
	var follow bool
	var limit int
	var search string
	cmd := &cobra.Command{
		Use: "log", Short: "Packets the ruleset logged (dropped by a rule or a policy)", Args: cobra.NoArgs,
		Long: `Shows the packets rules with --log and the policies (settings
--log-drops) logged, newest last. -f keeps watching.`,
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			var last time.Time
			print := func(es []api.LogEntry) {
				sort.Slice(es, func(i, j int) bool { return es[i].Time.Before(es[j].Time) })
				for _, e := range es {
					last = e.Time
					src, dst := e.Source, e.Dest
					if e.SrcPort != 0 {
						src = joinPort(src, e.SrcPort)
					}
					if e.DestPort != 0 {
						dst = joinPort(dst, e.DestPort)
					}
					what := e.Protocol
					if e.ICMPType != "" {
						what += " " + e.ICMPType
					}
					if e.TCPFlags != "" {
						what += " " + e.TCPFlags
					}
					fmt.Printf("%s  %-28s %-6s %-6s %s -> %s  %s\n", e.Time.Local().Format("15:04:05"), strings.TrimSpace(e.Prefix), orDash(e.In), orDash(e.Out), src, dst, what)
				}
			}
			for {
				var es []api.LogEntry
				query := q("limit", fmt.Sprint(limit), "q", search)
				if !last.IsZero() {
					query.Set("after", last.Format(time.RFC3339Nano))
				}
				if err := c.Get(ctx(), "/log", query, &es); err != nil {
					return err
				}
				if flagOutput == "json" || flagOutput == "yaml" {
					return output(es, nil)
				}
				print(es)
				if !follow {
					if len(es) == 0 {
						fmt.Fprintln(os.Stderr, "nothing logged yet (log with 'hc rule update ID --log' or 'hc settings set --log-drops on')")
					}
					return nil
				}
				time.Sleep(2 * time.Second)
			}
		},
	}
	cmd.Flags().BoolVarP(&follow, "follow", "f", false, "keep watching")
	cmd.Flags().IntVar(&limit, "limit", 50, "at most this many")
	cmd.Flags().StringVar(&search, "search", "", "only entries containing this (address, interface, prefix)")
	return cmd
}

func joinPort(addr string, port int) string {
	if strings.Contains(addr, ":") {
		return fmt.Sprintf("[%s]:%d", addr, port)
	}
	return fmt.Sprintf("%s:%d", addr, port)
}

// ---- probation

func confirmCmd() *cobra.Command {
	return &cobra.Command{
		Use: "confirm", Short: "Keep the changes on probation (otherwise they roll back)", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			var out map[string]int
			if err := c.Do(ctx(), "POST", "/confirm", nil, nil, &out); err != nil {
				return err
			}
			if out["confirmed"] == 0 {
				fmt.Println("nothing was waiting to be confirmed")
			} else if out["confirmed"] == 1 {
				fmt.Println("confirmed 1 change; it is kept and loaded at boot")
			} else {
				fmt.Printf("confirmed %d changes; they are kept and loaded at boot\n", out["confirmed"])
			}
			return nil
		},
	}
}

func rollbackCmd() *cobra.Command {
	return &cobra.Command{
		Use: "rollback", Short: "Undo the changes on probation now", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			var out map[string]int
			if err := c.Do(ctx(), "POST", "/rollback", nil, nil, &out); err != nil {
				return err
			}
			fmt.Printf("rolled back %d changes\n", out["rolled_back"])
			return nil
		},
	}
}

// ---- import and takeover

func importCmd() *cobra.Command {
	var replace bool
	var table, defines, textFile string
	cmd := &cobra.Command{
		Use:   "import [FILE|-]",
		Short: "Import an nftables ruleset (nft -j JSON) as Housecarl's configuration",
		Long: `Turns an existing nftables ruleset into zones, sets, services, rules, port
forwards and NAT. The input is nft's JSON; on the firewall:

  sudo hc import --defines /etc/nftables.conf -n

Without a FILE, hc runs 'nft -j list ruleset' and 'nft -a list ruleset'
itself (root on the firewall); from elsewhere, give the JSON as FILE and
the text with --text. --defines reads the ruleset file's define lines, to
name the sets as you did (trusted_ips, wg0_net, …). -n shows the result without
saving; what can't be expressed becomes raw rules, listed with notes.
Once it looks right, import without -n, check it with 'hc ruleset', and
'hc takeover inet main' deletes the old table.`,
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			var data, text []byte
			var err error
			switch {
			case len(args) == 0:
				data, err = exec.Command("nft", "-j", "list", "ruleset").Output()
				if err != nil {
					return fmt.Errorf("running 'nft -j list ruleset': %v (give a FILE, or run as root on the firewall)", err)
				}
				text, _ = exec.Command("nft", "-a", "list", "ruleset").Output()
			case args[0] == "-":
				data, err = io.ReadAll(os.Stdin)
			default:
				data, err = os.ReadFile(args[0])
			}
			if err != nil {
				return err
			}
			if textFile != "" {
				if text, err = os.ReadFile(textFile); err != nil {
					return err
				}
			}
			in := api.ImportInput{JSON: data, Text: string(text), Table: table, Replace: replace}
			if defines != "" {
				b, err := os.ReadFile(defines)
				if err != nil {
					return err
				}
				in.Defines = string(b)
			}
			c, err := newClient()
			if err != nil {
				return err
			}
			var res api.ImportResult
			if err := c.Do(ctx(), "POST", "/import/nft", nil, in, &res); err != nil {
				return err
			}
			if flagOutput == "json" || flagOutput == "yaml" {
				return output(res, nil)
			}
			st := res.State
			fmt.Printf("%d zones, %d sets, %d services, %d rules, %d port forwards, %d source NAT rules, %d redirects\n",
				len(st.Zones), len(st.Sets), len(st.Services), len(st.Rules), len(st.Forwards), len(st.SNATs), len(st.Redirects))
			for _, n := range res.Notes {
				fmt.Println("note:", n)
			}
			for _, r := range res.Raw {
				fmt.Println("raw rule:", r)
			}
			return report(&res.MutationResponse)
		},
	}
	cmd.Flags().BoolVar(&replace, "replace", false, "replace Housecarl's configuration (needed when it has one)")
	cmd.Flags().StringVar(&table, "table", "", "import only this table (\"inet main\"; default: all but Housecarl's)")
	cmd.Flags().StringVar(&defines, "defines", "", "the ruleset file, whose defines name the sets")
	cmd.Flags().StringVar(&textFile, "text", "", "'nft -a list ruleset' output, to keep what can't be expressed as raw rules")
	return cmd
}

func takeoverCmd() *cobra.Command {
	var yes bool
	cmd := &cobra.Command{
		Use:   "takeover TABLE...",
		Short: "Delete the tables Housecarl replaces (\"inet main\"), on probation",
		Long: `Deletes other nftables tables once Housecarl's ruleset replaces them (after
'hc import'). Until then both apply: a packet must get past both. Over the
network this is on probation like a change: unless confirmed, the tables
come back. Don't forget the boot: disable nftables.service, or empty
/etc/nftables.conf, or it brings the old ruleset back.

  hc takeover "inet main"`,
		Args: cobra.MinimumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			if !confirm("Delete "+strings.Join(args, ", ")+"?", yes) {
				return fmt.Errorf("nothing deleted")
			}
			c, err := newClient()
			if err != nil {
				return err
			}
			var out map[string]any
			if err := c.Do(ctx(), "POST", "/takeover", nil, api.TakeoverInput{Tables: args}, &out); err != nil {
				return err
			}
			fmt.Println(out["message"])
			return nil
		},
	}
	cmd.Flags().BoolVarP(&yes, "yes", "y", false, "don't ask")
	return cmd
}