smallwebwaf/internal/proxy/alerts_test.go

package proxy_test

import (
	"maps"
	"net/http"
	"net/netip"
	"reflect"
	"testing"
	"time"

	"sneak.berlin/go/smallwebwaf/internal/alerts"
	"sneak.berlin/go/smallwebwaf/internal/bans"
	"sneak.berlin/go/smallwebwaf/internal/proxy"
	"sneak.berlin/go/smallwebwaf/internal/requestlog"
)

const (
	alertWebhookURL = "SWWAF_ALERT_WEBHOOK_URL"
	alertMaxPerHour = "SWWAF_ALERT_MAX_PER_HOUR"
	// alertInstance is the instance every alert of these tests gives.
	alertInstance = "fsn1app1/gitea"
)

func TestBanForABrokenLimitRaisesABanAlertWithItsNotes(t *testing.T) {
	t.Parallel()

	s, clk, server, queue := startWithAlerts(t, map[string]string{
		rateLimitPerMinute: "1",
		banScopeV4Prefix:   "24",
	})
	start := clk.Now()

	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)

	netblock := netip.MustParsePrefix("203.0.113.0/24")
	ban := server.Ledger.Bans(netblock)[0]

	// A request refused under the ban raises no other alert.
	clk.advance(time.Minute)
	s.get(client, http.StatusForbidden, requestlog.ActionBanned)

	wantAlerts(t, queue, banAlert(alerts.EventBan, start, client, bans.Ban{
		Netblock: netblock, Cause: bans.CauseLimit,
		Reason: "requests per minute over the limit of 1", Notes: ban.Notes,
	}, requestlog.FormatTime(start.Add(time.Hour))))

	if ban.Notes.Limit != 1 || ban.Notes.Request.Path != "/" {
		t.Errorf("the alert's notes are %+v, want those of the broken limit", ban.Notes)
	}
}

func TestAttackBanRaisesABanAlertThenAPermanentBanAlert(t *testing.T) {
	t.Parallel()

	s, clk, server, queue := startWithAlerts(t, map[string]string{
		rulesDir: writeRules(t, testRules),
	})
	start := clk.Now()
	netblock := netip.MustParsePrefix(client + "/32")
	other := netip.MustParsePrefix(otherClient + "/32")

	// The probe bans the client for seven days, and its next request makes
	// the ban permanent. The request after that changes nothing.
	s.request(client, "/.env", http.StatusForbidden, requestlog.ActionBanned)

	attackBan := server.Ledger.Bans(netblock)[0]

	clk.advance(time.Minute)
	s.get(client, http.StatusForbidden, requestlog.ActionBanned)

	permanentBan := server.Ledger.Bans(netblock)[0]

	s.get(client, http.StatusForbidden, requestlog.ActionBanned)

	// Another client's probe after its first ban has run out without a
	// request makes a permanent ban at once.
	s.request(otherClient, "/.env", http.StatusForbidden, requestlog.ActionBanned)
	clk.advance(7 * 24 * time.Hour)
	s.request(otherClient, "/.env", http.StatusForbidden, requestlog.ActionBanned)

	otherBans := server.Ledger.Bans(other)

	wantAlerts(t, queue,
		attackAlert(alerts.EventBan, start, client, attackBan,
			requestlog.FormatTime(start.Add(7*24*time.Hour))),
		attackAlert(alerts.EventPermanentBan, start.Add(time.Minute), client,
			permanentBan, "permanent"),
		attackAlert(alerts.EventBan, start.Add(time.Minute), otherClient, otherBans[0],
			requestlog.FormatTime(start.Add(time.Minute+7*24*time.Hour))),
		attackAlert(alerts.EventPermanentBan, start.Add(time.Minute+7*24*time.Hour),
			otherClient, otherBans[1], "permanent"),
	)
}

func TestObserveModeRaisesTheBanAlertsItWouldHave(t *testing.T) {
	t.Parallel()

	s, clk, server, queue := startWithAlerts(t, map[string]string{
		mode:               observe,
		rateLimitPerMinute: "2",
		rulesDir:           writeRules(t, testRules),
	})
	start := clk.Now()

	// A ban for a clear sign of attack, which a request under it would make
	// permanent.
	group := netip.MustParsePrefix(ipv6Group)
	attackBan, _ := server.Ledger.BanForAttack(group, start, bans.Notes{RuleID: "probe"})

	// The third request breaks the limit, and so does the fourth, within the
	// cooldown, which raises nothing. The probe is a clear sign of attack.
	for range 4 {
		s.get(client, http.StatusOK, requestlog.ActionForward)
	}

	s.request(otherClient, "/.env", http.StatusOK, requestlog.ActionForward)
	line := s.get(ipv6Client, http.StatusOK, requestlog.ActionForward)

	// No ban is made, and none made permanent.
	if held := server.Ledger.Snapshot(); len(held) != 1 || held[0] != attackBan ||
		line.BanExpires != requestlog.FormatTime(attackBan.Expires) {
		t.Errorf("the ledger holds %+v, and the log line gives %s, want the ban "+
			"for the attack alone, as it was", held, line.BanExpires)
	}

	waiting := queue.Snapshot().Waiting[alerts.DestinationWebhook]
	if len(waiting) != 3 || queue.Suppressed() != 0 {
		t.Fatalf("%d alerts wait and %d are held back, want 3 and 0: %+v",
			len(waiting), queue.Suppressed(), waiting)
	}

	limitNotes, _ := waiting[0].Detail["notes"].(bans.Notes)
	attackNotes, _ := waiting[1].Detail["notes"].(bans.Notes)

	if limitNotes.Limit != 2 || limitNotes.Request.Path != "/" ||
		attackNotes.Request.Path != "/.env" {
		t.Errorf("the notes are %+v and %+v, want those of the broken limit and "+
			"of the probe", limitNotes, attackNotes)
	}

	// Each alert is the one enforce mode would have raised, with mode
	// observe in its detail.
	want := []alerts.Alert{
		banAlert(alerts.EventBan, start, client, bans.Ban{
			Netblock: netip.MustParsePrefix(client + "/32"), Cause: bans.CauseLimit,
			Reason: "requests per minute over the limit of 2", Notes: limitNotes,
		}, requestlog.FormatTime(start.Add(time.Hour))),
		attackAlert(alerts.EventBan, start, otherClient, bans.Ban{
			Netblock: netip.MustParsePrefix(otherClient + "/32"), Notes: attackNotes,
		}, requestlog.FormatTime(start.Add(7*24*time.Hour))),
		attackAlert(alerts.EventPermanentBan, start, ipv6Client, attackBan, permanent),
	}
	for _, alert := range want {
		alert.Detail["mode"] = observe
	}

	wantAlerts(t, queue, want...)
}

func TestObserveModeWorksOutABanOnlyWhenItsAlertWouldBeSent(t *testing.T) {
	t.Parallel()

	s, _, _, queue := startWithAlerts(t, map[string]string{
		mode:               observe,
		rateLimitPerMinute: "2",
		rulesDir:           writeRules(t, testRules),
		alertMaxPerHour:    "2",
	})

	// The client's third request breaks the limit, and raises the first
	// alert of the hour. Its fourth is within the cooldown.
	for range 4 {
		s.get(client, http.StatusOK, requestlog.ActionForward)
	}

	// The other client's first probe raises the second. Its second probe is
	// within the cooldown.
	for range 2 {
		s.request(otherClient, "/.env", http.StatusOK, requestlog.ActionForward)
	}

	// The IPv6 client's third request breaks the limit past the two alerts
	// an hour.
	for range 3 {
		s.get(ipv6Client, http.StatusOK, requestlog.ActionForward)
	}

	// Had the ban been worked out for any of the requests within the
	// cooldown or past the two an hour, its alert would have been raised,
	// held back and counted.
	waiting := queue.Snapshot().Waiting[alerts.DestinationWebhook]
	if len(waiting) != 2 || queue.Suppressed() != 0 {
		t.Errorf("%d alerts wait and %d are held back, want 2 and 0: %+v",
			len(waiting), queue.Suppressed(), waiting)
	}
}

// startWithAlerts is startWithClock with alerts to a webhook, which is
// never sent them, and returns the queue they wait in as well.
func startWithAlerts(
	t *testing.T, env map[string]string,
) (*sender, *clock, *proxy.Server, *alerts.Queue) {
	t.Helper()

	return startAppWithAlerts(t, func(http.ResponseWriter, *http.Request) {}, env)
}

// startAppWithAlerts is startWithAlerts in front of the app handler.
func startAppWithAlerts(
	t *testing.T, handler http.HandlerFunc, env map[string]string,
) (*sender, *clock, *proxy.Server, *alerts.Queue) {
	t.Helper()

	app := startApp(t, handler)
	clk := &clock{now: time.Date(2026, 10, 6, 0, 0, 0, 0, time.UTC)}
	settings := map[string]string{
		trustedProxies:  trustLocalhost,
		alertWebhookURL: "https://alerts.example/smallwebwaf",
		instanceName:    alertInstance,
	}
	maps.Copy(settings, env)

	addr, out, server, queue := startProxyWithAlerts(t, app.URL, "", clk.Now, settings)

	return &sender{t: t, addr: addr, out: out}, clk, server, queue
}

// banAlert returns the alert for event, raised by a request from client at
// the time raised, for ban, with its netblock, cause, reason and notes,
// which ends at expires, as the log line gives it.
func banAlert(
	event string, raised time.Time, client string, ban bans.Ban, expires string,
) alerts.Alert {
	return alerts.Alert{
		Instance: alertInstance,
		Time:     raised,
		Event:    event,
		Client:   netip.MustParseAddr(client),
		Netblock: ban.Netblock,
		Reason:   ban.Reason,
		Detail: map[string]any{
			"cause": ban.Cause, "ban_expires": expires, "notes": ban.Notes,
		},
	}
}

// attackAlert is banAlert for a ban for the probe rule of testRules, with
// the netblock and the notes of ban.
func attackAlert(
	event string, raised time.Time, client string, ban bans.Ban, expires string,
) alerts.Alert {
	return banAlert(event, raised, client, bans.Ban{
		Netblock: ban.Netblock, Cause: bans.CauseAttack, Reason: "matched the rule probe",
		Notes: ban.Notes,
	}, expires)
}

// wantAlerts checks the alerts waiting in queue, in order.
func wantAlerts(t *testing.T, queue *alerts.Queue, want ...alerts.Alert) {
	t.Helper()

	got := queue.Snapshot().Waiting[alerts.DestinationWebhook]
	if len(got) != len(want) {
		t.Fatalf("%d alerts wait, want %d: %+v", len(got), len(want), got)
	}

	for i := range want {
		if !reflect.DeepEqual(got[i], want[i]) {
			t.Errorf("alert %d is\n%+v\nwant\n%+v", i, got[i], want[i])
		}
	}
}