smallwebwaf/internal/bans/bans_test.go

package bans_test

import (
	"net/netip"
	"strings"
	"testing"
	"time"

	"sneak.berlin/go/smallwebwaf/internal/bans"
)

const day = 24 * time.Hour

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	now := midnight()

	// Each ban is followed by another as soon as it ends: 1, 3, 9, 27 and
	// 81 hours.
	for i, hours := range []int{1, 3, 9, 27, 81} {
		ban, _ := ledger.BanForLimit(netblock, now, bans.Notes{})

		length := time.Duration(hours) * time.Hour
		if !ban.Expires.Equal(now.Add(length)) ||
			ban.Notes.EarlierBans != (bans.EarlierBans{Limit: i}) {
			t.Fatalf("ban %d lasts %s with earlier bans %+v, want %d hours and %d for a limit",
				i+1, ban.Expires.Sub(now), ban.Notes.EarlierBans, hours, i)
		}

		now = ban.Expires
	}

	// The sixth would last 243 hours, more than seven days: it is
	// permanent, and never ends.
	ban, _ := ledger.BanForLimit(netblock, now, bans.Notes{})
	if !ban.Permanent() {
		t.Fatalf("sixth ban ends at %s, want a permanent one", ban.Expires)
	}

	_, banned, _ := ledger.Check(netblock.Addr(), now.Add(100*365*day))
	if !banned {
		t.Error("a permanent ban ended")
	}
}

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

	for _, tc := range []struct {
		name string
		// gap is the time between the end of the first ban and the second.
		gap  time.Duration
		want time.Duration
	}{
		{"broken again as the window ends", day, 3 * time.Hour},
		{"broken again after the window", day + time.Nanosecond, time.Hour},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			ledger := bans.New(defaultRules())
			netblock := netip.MustParsePrefix("203.0.113.9/32")

			first, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
			second, _ := ledger.BanForLimit(netblock, first.Expires.Add(tc.gap), bans.Notes{})

			if second.Expires.Sub(second.Start) != tc.want ||
				second.Notes.EarlierBans != (bans.EarlierBans{Limit: 1}) {
				t.Errorf("second ban lasts %s with earlier bans %+v, want %s and 1 for a limit",
					second.Expires.Sub(second.Start), second.Notes.EarlierBans, tc.want)
			}
		})
	}
}

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

	rules := defaultRules()
	rules.LimitBanDuration = rules.MaxBanDuration + time.Hour
	ledger := bans.New(rules)

	ban, _ := ledger.BanForLimit(netip.MustParsePrefix("203.0.113.9/32"), midnight(),
		bans.Notes{})
	if !ban.Permanent() {
		t.Errorf("first ban ends at %s, want a permanent one", ban.Expires)
	}
}

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

	// With bans of up to 100,000 days, the 14th ban in a row, of 3^13
	// hours, is within the maximum, and three times as long would not fit
	// in a time.Duration. The 15th is permanent.
	rules := defaultRules()
	rules.MaxBanDuration = 100000 * day
	ledger := bans.New(rules)
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	now := midnight()

	for i := range 14 {
		ban, _ := ledger.BanForLimit(netblock, now, bans.Notes{})
		if !ban.Expires.After(ban.Start) {
			t.Fatalf("ban %d starts at %s and ends at %s", i+1, ban.Start, ban.Expires)
		}

		now = ban.Expires
	}

	ban, _ := ledger.BanForLimit(netblock, now, bans.Notes{})
	if !ban.Permanent() {
		t.Errorf("15th ban ends at %s, want a permanent one", ban.Expires)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	first, made := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	if !made {
		t.Error("the first ban was not made")
	}

	again, made := ledger.BanForLimit(netblock, midnight().Add(time.Minute), bans.Notes{})

	if made || again != first || len(ledger.Bans(netblock)) != 1 {
		t.Errorf("a limit broken during a ban gave %+v, made %t, and %d bans, "+
			"want %+v, not made, and 1", again, made, len(ledger.Bans(netblock)), first)
	}

	again, made = ledger.BanForAttack(netblock, midnight().Add(time.Minute), bans.Notes{})
	if made || again != first {
		t.Errorf("an attack during a ban gave %+v, made %t, want %+v, not made",
			again, made, first)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	ban, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{Requests: 5})

	for range 3 {
		got, banned, _ := ledger.Check(netblock.Addr(), ban.Expires.Add(-time.Nanosecond))
		if !banned || got.Start != ban.Start {
			t.Fatalf("check during the ban gives %+v and %t", got, banned)
		}
	}

	_, banned, _ := ledger.Check(netip.MustParseAddr("203.0.113.10"), midnight())
	if banned {
		t.Error("another netblock is banned")
	}

	_, banned, _ = ledger.Check(netblock.Addr(), ban.Expires)
	if banned {
		t.Error("the ban did not end")
	}

	// The netblock's requests went from 5 to 8 with the three refused.
	notes := ledger.Bans(netblock)[0].Notes
	if notes.Refused != 3 || notes.Requests != 8 {
		t.Errorf("the notes count %d refused requests of %d, want 3 of 8",
			notes.Refused, notes.Requests)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	ban, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{Requests: 5})

	got, banned, _ := ledger.Find(netblock.Addr(), ban.Expires.Add(-time.Nanosecond))
	if !banned || got != ban {
		t.Errorf("find during the ban gives %+v and %t, want %+v", got, banned, ban)
	}

	_, banned, _ = ledger.Find(netblock.Addr(), ban.Expires)
	if banned {
		t.Error("the ban did not end")
	}

	if notes := ledger.Bans(netblock)[0].Notes; notes != ban.Notes {
		t.Errorf("the notes are %+v, want them unchanged, %+v", notes, ban.Notes)
	}
}

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

	rules := defaultRules()
	rules.MaxBans = 3
	ledger := bans.New(rules)
	a := netip.MustParsePrefix("203.0.113.1/32")
	b := netip.MustParsePrefix("203.0.113.2/32")
	c := netip.MustParsePrefix("203.0.113.3/32")
	d := netip.MustParsePrefix("2001:db8::/64")
	now := midnight()

	first, _ := ledger.BanForLimit(a, now, bans.Notes{})
	ledger.BanForLimit(b, now, bans.Notes{})
	ledger.BanForLimit(c, now, bans.Notes{})

	// A request from a makes b the netblock seen longest ago, and its ban
	// goes to make room for d's.
	ledger.Check(a.Addr(), now)
	ledger.BanForLimit(d, now, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 1, b: 0, c: 1, d: 1})

	// a is banned again once its ban has ended; c, seen longest ago, goes.
	ledger.BanForLimit(a, first.Expires, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 2, c: 0, d: 1})

	// With d seen since, a is seen longest ago, and its earlier ban goes
	// first.
	ledger.Check(d.Addr(), first.Expires)
	ledger.BanForLimit(b, first.Expires, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 1, b: 1, d: 1})

	if !ledger.Bans(a)[0].Start.Equal(first.Expires) {
		t.Errorf("a kept its ban of %s, want the later one", ledger.Bans(a)[0].Start)
	}
}

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

	// With room for one ban, the netblock's ended ban goes to make room for
	// its new one, whose notes still count it.
	rules := defaultRules()
	rules.MaxBans = 1
	ledger := bans.New(rules)
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	first, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	second, _ := ledger.BanForLimit(netblock, first.Expires, bans.Notes{})

	held := ledger.Bans(netblock)
	if len(held) != 1 || held[0] != second ||
		held[0].Notes.EarlierBans != (bans.EarlierBans{Limit: 1}) {
		t.Errorf("the ledger holds %+v, want only the second ban, "+
			"with 1 earlier ban for a limit", held)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	notes := bans.Notes{RuleID: "env-file", Target: "path"}

	ban, _ := ledger.BanForAttack(netblock, midnight(), notes)
	if !ban.Expires.Equal(midnight().Add(7*day)) || ban.Cause != bans.CauseAttack ||
		ban.Notes.RuleID != "env-file" || ledger.Made(bans.CauseAttack) != 1 ||
		ledger.Made(bans.CauseLimit) != 0 {
		t.Fatalf("the ban is %+v, with %d made for an attack and %d for a limit, "+
			"want one for an attack, of seven days", ban,
			ledger.Made(bans.CauseAttack), ledger.Made(bans.CauseLimit))
	}

	wantChanged(t, ledger, true)

	// In observe mode the ban refuses nothing, and stays as it is, while
	// Find tells that the request would have made it permanent.
	got, _, wouldMakePermanent := ledger.Find(netblock.Addr(), midnight().Add(time.Hour))
	if got.Permanent() || ledger.Bans(netblock)[0].Permanent() || !wouldMakePermanent {
		t.Fatalf("a request found under the ban left it %+v, would have made it "+
			"permanent %t, want it as it was, and true", got, wouldMakePermanent)
	}

	wantChanged(t, ledger, false)

	// A request it refuses makes it permanent, says so, and makes
	// bans.json due.
	got, _, madePermanent := ledger.Check(netblock.Addr(), midnight().Add(time.Hour))
	if !madePermanent || !got.Permanent() || !ledger.Bans(netblock)[0].Permanent() {
		t.Fatalf("after a request during the ban, it is %+v, made permanent %t, "+
			"want it made permanent", got, madePermanent)
	}

	wantChanged(t, ledger, true)

	// The next request finds it permanent already.
	_, banned, madePermanent := ledger.Check(netblock.Addr(), midnight().Add(100*365*day))
	if !banned || madePermanent {
		t.Errorf("a later request is banned %t, and made the ban permanent %t, "+
			"want banned by the permanent ban", banned, madePermanent)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	// A ban for a broken limit before does not count.
	first, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	second, _ := ledger.BanForAttack(netblock, first.Expires, bans.Notes{})

	if second.Expires.Sub(second.Start) != 7*day {
		t.Fatalf("the first ban for an attack lasts %s, want 7 days",
			second.Expires.Sub(second.Start))
	}

	// Once that has run out without a request, the netblock is served, and
	// its next clear sign of attack bans it for good.
	_, banned, _ := ledger.Check(netblock.Addr(), second.Expires)
	if banned {
		t.Fatal("the ban did not end")
	}

	// Its notes show the earlier ban for an attack that makes it permanent,
	// beside the one for a limit.
	third, _ := ledger.BanForAttack(netblock, second.Expires.Add(30*day), bans.Notes{})
	if !third.Permanent() ||
		third.Notes.EarlierBans != (bans.EarlierBans{Limit: 1, Attack: 1}) {
		t.Errorf("the next ban for an attack is %+v, want a permanent one, "+
			"with 1 earlier ban for a limit and 1 for an attack", third)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	first, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	wantChanged(t, ledger, true)

	// While the first ban lasts, none would be made.
	during, would := ledger.WouldBanForAttack(netblock, midnight(), bans.Notes{})
	if would || during != first {
		t.Errorf("during the first ban, would ban %t with %+v, want false with %+v",
			would, during, first)
	}

	// As it ends, a clear sign of attack would ban for seven days, and a
	// limit broken again for three hours, but neither is made.
	limitNotes := bans.Notes{Limit: 1, Window: "minute"}
	attack, wouldAttack := ledger.WouldBanForAttack(netblock, first.Expires,
		bans.Notes{RuleID: "git-dir"})
	limit, wouldLimit := ledger.WouldBanForLimit(netblock, first.Expires, limitNotes)

	if !wouldAttack || !attack.Expires.Equal(first.Expires.Add(7*day)) ||
		attack.Reason != "matched the rule git-dir" || !wouldLimit ||
		!limit.Expires.Equal(first.Expires.Add(3*time.Hour)) ||
		limit.Reason != "requests per minute over the limit of 1" {
		t.Errorf("would ban with %+v and %+v, want seven days for the attack and "+
			"three hours for the limit", attack, limit)
	}

	if len(ledger.Bans(netblock)) != 1 || ledger.Made(bans.CauseLimit) != 1 ||
		ledger.Made(bans.CauseAttack) != 0 {
		t.Errorf("the ledger holds %+v, want the first ban alone", ledger.Bans(netblock))
	}

	wantChanged(t, ledger, false)

	// The ban made is the one that would have been.
	made, _ := ledger.BanForLimit(netblock, first.Expires, limitNotes)
	if made != limit {
		t.Errorf("the ban made is %+v, want %+v", made, limit)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	now := midnight()

	// Five bans for a limit in a row, of 1, 3, 9, 27 and 81 hours, are not
	// permanent. The sixth, of 243 hours, would be, while a first ban for
	// an attack would not.
	for i := range 5 {
		if ledger.WouldBePermanent(netblock, now, bans.CauseLimit) {
			t.Fatalf("ban %d for a limit would be permanent", i+1)
		}

		ban, _ := ledger.BanForLimit(netblock, now, bans.Notes{})
		now = ban.Expires
	}

	if !ledger.WouldBePermanent(netblock, now, bans.CauseLimit) {
		t.Error("the sixth ban for a limit would not be permanent")
	}

	if ledger.WouldBePermanent(netblock, now, bans.CauseAttack) {
		t.Error("a first ban for an attack would be permanent")
	}

	// Once a first ban for an attack has ended, the next would be permanent.
	attack, _ := ledger.BanForAttack(netblock, now, bans.Notes{})
	if !ledger.WouldBePermanent(netblock, attack.Expires, bans.CauseAttack) {
		t.Error("a second ban for an attack would not be permanent")
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	// Three times the seven days would be permanent; a limit broken as the
	// ban for an attack ends bans for an hour, as a first broken limit does.
	attack, _ := ledger.BanForAttack(netblock, midnight(), bans.Notes{})
	limit, _ := ledger.BanForLimit(netblock, attack.Expires, bans.Notes{})

	if limit.Expires.Sub(limit.Start) != time.Hour || limit.Cause != bans.CauseLimit {
		t.Errorf("the ban for a limit is %+v, want one of an hour", limit)
	}

	// And a request during the ban for a limit leaves it as it is.
	got, _, madePermanent := ledger.Check(netblock.Addr(), limit.Start)
	if got.Permanent() || madePermanent {
		t.Error("a request during a ban for a limit made it permanent")
	}
}

func TestRequestTextsAreCutTo256Bytes(t *testing.T) {
	t.Parallel()

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	long := strings.Repeat("a", 300)
	request := bans.Request{
		Time: midnight(), Method: long, Host: long, Path: long, Status: 403, UserAgent: long,
	}

	ban, _ := ledger.BanForLimit(netblock, midnight(), bans.Notes{Request: request})

	cut := long[:256]
	want := bans.Request{
		Time: midnight(), Method: cut, Host: cut, Path: cut, Status: 403, UserAgent: cut,
	}

	if ban.Notes.Request != want || ledger.Bans(netblock)[0].Notes.Request != want {
		t.Errorf("the notes keep %+v, want each text cut to 256 bytes", ban.Notes.Request)
	}
}

// defaultRules are the rules at the settings' defaults.
func defaultRules() bans.Rules {
	return bans.Rules{
		LimitBanDuration:     time.Hour,
		LimitBanRepeatWindow: day,
		MaxBanDuration:       7 * day,
		AttackBanDuration:    7 * day,
		MaxBans:              5000,
	}
}

// midnight is when the tests' first bans are made.
func midnight() time.Time {
	return time.Date(2026, 10, 6, 0, 0, 0, 0, time.UTC)
}

// wantBans checks how many bans the ledger holds on each netblock.
func wantBans(t *testing.T, ledger *bans.Ledger, want map[netip.Prefix]int) {
	t.Helper()

	for netblock, count := range want {
		got := len(ledger.Bans(netblock))
		if got != count {
			t.Errorf("%s has %d bans, want %d", netblock, got, count)
		}
	}
}