Bans an admin makes or lifts: the admin cause, a reason, lifted bans kept (closes #86)

A bans.json entry without a cause gets the cause admin, written back so. Bans whose cause is admin are never dropped and do not count toward SWWAF_MAX_BANS, so setting a ban's cause to admin keeps it. Bans smallwebwaf makes get a reason: the limit broken or the rule matched. A lifted ban refuses nothing, is kept, and makes no later ban longer. smallwebwaf_bans_made_total counts admin bans an edit adds while running; earlier_bans counts admin in place of without_cause. Judgement call: lifted lifts at once, whatever time it gives. Judgement call: a lifted ban still counts in earlier_bans. Known gap: a ban dropped from behind an admin's ban on its netblock leaves that netblock's later earlier_bans. Model: opus-5-5
2026-10-06 23:09:52 +02:00
parent 0797e5def2
commit ee9ba08a8a
11 changed files with 677 additions and 153 deletions
@@ -1,11 +1,13 @@
 // Package bans is the ban ledger: the bans smallwebwaf makes on the
 // netblocks of clients that break a rate limit or show a clear sign of
-// attack, with their notes, as the "Bans" section of SPEC.md describes.
-// The bans are kept in memory, and written to bans.json and read from it
-// by the state package.
+// attack, and those an admin makes, with their notes, as the "Bans"
+// section of SPEC.md describes. The bans are kept in memory, and written
+// to bans.json and read from it by the state package.
 package bans

 import (
+	"fmt"
+	"math"
 	"net/netip"
 	"slices"
 	"strings"
@@ -15,13 +17,15 @@ import (
 	"github.com/hashicorp/golang-lru/v2/simplelru"
 )

-// The causes of the bans smallwebwaf makes. A ban an admin adds to
-// bans.json may have no cause.
+// The causes of bans.
 const (
-	// CauseLimit is a ban for a broken limit.
+	// CauseLimit is a ban smallwebwaf made for a broken limit.
 	CauseLimit = "limit"
-	// CauseAttack is a ban for a clear sign of attack.
+	// CauseAttack is a ban smallwebwaf made for a clear sign of attack.
 	CauseAttack = "attack"
+	// CauseAdmin is a ban an admin made, or one smallwebwaf made that an
+	// admin keeps. It is never dropped.
+	CauseAdmin = "admin"
 )

 // repeatFactor is how many times as long as the netblock's last ban a ban
@@ -46,9 +50,10 @@ type Rules struct {
 	// AttackBanDuration is how long a first ban for a clear sign of attack
 	// lasts.
 	AttackBanDuration time.Duration
-	// MaxBans is the most bans held, at least one. Past it, the earliest
-	// ban of the netblock that has gone longest without a request is
-	// dropped.
+	// MaxBans is the most bans held whose cause is not CauseAdmin, at
+	// least one. Past it, the earliest such ban of the netblock that has
+	// gone longest without a request is dropped. Bans whose cause is
+	// CauseAdmin are held besides, and never dropped.
 	MaxBans int
 }

@@ -58,10 +63,16 @@ type Ban struct {
 	Start    time.Time
 	// Expires is when the ban ends, zero for a permanent ban.
 	Expires time.Time
-	// Cause is CauseLimit or CauseAttack, or "" for a ban an admin added
-	// without one.
+	// Cause is CauseLimit, CauseAttack or CauseAdmin.
 	Cause string
-	Notes Notes
+	// Reason is a short text: for a ban smallwebwaf made, the limit broken
+	// or the rule that matched; for an admin's, what the admin wrote.
+	Reason string
+	// Lifted is when an admin lifted the ban, zero while no admin has. A
+	// lifted ban refuses nothing, and does not make the netblock's next
+	// ban longer.
+	Lifted time.Time
+	Notes  Notes
 }

 // Permanent reports whether the ban never runs out.
@@ -69,9 +80,10 @@ func (b Ban) Permanent() bool {
 	return b.Expires.IsZero()
 }

-// ActiveAt reports whether the ban refuses requests at now.
+// ActiveAt reports whether the ban refuses requests at now: it has not
+// been lifted, and has not run out.
 func (b Ban) ActiveAt(now time.Time) bool {
-	return b.Permanent() || now.Before(b.Expires)
+	return b.Lifted.IsZero() && (b.Permanent() || now.Before(b.Expires))
 }

 // Notes are what an admin needs to decide whether to lift a ban. The
@@ -107,13 +119,10 @@ type Notes struct {
 }

 // EarlierBans counts a netblock's bans before a ban, by cause.
-//
-//nolint:tagliatelle // the state files use snake_case, as the request log does
 type EarlierBans struct {
 	Limit  int `json:"limit"`
 	Attack int `json:"attack"`
-	// WithoutCause counts the bans an admin added without a cause.
-	WithoutCause int `json:"without_cause"`
+	Admin  int `json:"admin"`
 }

 // Request is a request in a ban's notes. Each text is cut to 256 bytes.
@@ -141,9 +150,11 @@ type Ledger struct {
 	// netblocks holds each banned netblock's bans, oldest first. Check and
 	// Find make each netblock they find the most recently seen.
 	netblocks *simplelru.LRU[netip.Prefix, *[]Ban]
-	// held is how many bans netblocks holds, at most rules.MaxBans.
+	// held is how many bans netblocks holds whose cause is not CauseAdmin,
+	// at most rules.MaxBans.
 	held int
-	// made is how many bans the ledger has made since the start, by cause.
+	// made is how many bans have been made since the start, by cause: by
+	// the ledger, and by an admin in an edit of bans.json.
 	made map[string]int
 	// v4Lengths and v6Lengths are the lengths of the IPv4 and IPv6
 	// netblocks that have been banned. Check looks for a ban at each of
@@ -155,9 +166,10 @@ type Ledger struct {

 // New returns a Ledger with no ban yet.
 func New(rules Rules) *Ledger {
-	// Every netblock held has a ban, so there are never more netblocks
-	// than rules.MaxBans, and the LRU never drops one itself.
-	netblocks, err := simplelru.NewLRU[netip.Prefix, *[]Ban](rules.MaxBans, nil)
+	// The ledger drops bans itself, and never those whose cause is
+	// CauseAdmin, however many there are, so the LRU has no limit of its
+	// own: it keeps the netblocks in the order they were last seen.
+	netblocks, err := simplelru.NewLRU[netip.Prefix, *[]Ban](math.MaxInt, nil)
 	if err != nil {
 		panic(err) // NewLRU fails only for a size below one
 	}
@@ -233,21 +245,26 @@ func activeBan(bans []Ban, now time.Time) *Ban {
 // BanForLimit bans netblock at now for a broken limit, with notes, and
 // returns the ban. A first ban lasts LimitBanDuration. A ban made within
 // LimitBanRepeatWindow after the netblock's ban that ended last, other
-// than one for a clear sign of attack, lasts repeatFactor times as long as
-// that one. A ban that would be longer than MaxBanDuration is permanent
-// instead. If a ban on netblock is still active, as when two of its
-// requests break a limit at once, that ban is returned and no other is
-// made. The ledger fills in the notes' Refused and EarlierBans itself.
+// than one for a clear sign of attack or a lifted one, lasts repeatFactor
+// times as long as that one. A ban that would be longer than
+// MaxBanDuration is permanent instead. If a ban on netblock is still
+// active, as when two of its requests break a limit at once, that ban is
+// returned and no other is made. The ledger fills in the notes' Refused
+// and EarlierBans itself, and gives the ban the reason "requests per
+// <Window> over the limit of <Limit>", from the notes.
 func (l *Ledger) BanForLimit(netblock netip.Prefix, now time.Time, notes Notes) Ban {
-	return l.ban(netblock, now, CauseLimit, notes)
+	reason := fmt.Sprintf("requests per %s over the limit of %d",
+		notes.Window, notes.Limit)
+
+	return l.ban(netblock, now, CauseLimit, reason, notes)
 }

 // BanForAttack bans netblock at now for a clear sign of attack, with
 // notes, and returns the ban, as BanForLimit does. A first ban lasts
-// AttackBanDuration; once the netblock has had one, the next is
-// permanent.
+// AttackBanDuration; once the netblock has had one that was not lifted,
+// the next is permanent. Its reason is "matched the rule <RuleID>".
 func (l *Ledger) BanForAttack(netblock netip.Prefix, now time.Time, notes Notes) Ban {
-	return l.ban(netblock, now, CauseAttack, notes)
+	return l.ban(netblock, now, CauseAttack, "matched the rule "+notes.RuleID, notes)
 }

 // Bans returns the bans held on netblock, oldest first. It is not a
@@ -264,8 +281,10 @@ func (l *Ledger) Bans(netblock netip.Prefix) []Ban {
 	return slices.Clone(*bans)
 }

-// Made returns how many bans for cause the ledger has made since the
-// start; bans read from bans.json are not among them.
+// Made returns how many bans for cause have been made since the start:
+// for CauseLimit and CauseAttack, by the ledger; for CauseAdmin, by an
+// admin in an edit of bans.json, as LoadEdit counts them. The bans read
+// from bans.json at the start are not among them.
 func (l *Ledger) Made(cause string) int {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -274,7 +293,7 @@ func (l *Ledger) Made(cause string) int {
 }

 // Count returns how many of the bans held are active at now, and how many
-// are permanent.
+// of those are permanent. A lifted ban is neither.
 func (l *Ledger) Count(now time.Time) (int, int) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -283,10 +302,12 @@ func (l *Ledger) Count(now time.Time) (int, int) {

 	for _, bans := range l.netblocks.Values() {
 		for _, ban := range *bans {
-			if ban.ActiveAt(now) {
-				active++
+			if !ban.ActiveAt(now) {
+				continue
 			}

+			active++
+
 			if ban.Permanent() {
 				permanent++
 			}
@@ -314,36 +335,81 @@ func (l *Ledger) Snapshot() []Ban {
 	return held
 }

-// Load puts bans read from bans.json into the ledger, in place of the
-// bans it holds, in the order they started, so that a netblock whose last
-// ban started latest counts as the most recently seen. Each netblock is
-// masked to its length, so that 203.0.113.9/24 is 203.0.113.0/24, and
-// each text in the notes is cut to 256 bytes. Past MaxBans the earliest
-// bans are dropped, as when they are made.
+// Load puts bans read from bans.json at the start into the ledger, in
+// place of the bans it holds, in the order they started, so that a
+// netblock whose last ban started latest counts as the most recently
+// seen. A ban without a cause is an admin's, and gets CauseAdmin. Each
+// netblock is masked to its length, so that 203.0.113.9/24 is
+// 203.0.113.0/24, and each text in the notes is cut to 256 bytes. Past
+// MaxBans the earliest bans whose cause is not CauseAdmin are dropped, as
+// when they are made.
 func (l *Ledger) Load(bans []Ban) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.load(bans)
+}
+
+// LoadEdit is Load for an admin's edit of bans.json, taken in while
+// smallwebwaf runs. Each ban in it whose cause is CauseAdmin, and which
+// the ledger did not hold, with the same netblock and start, is one the
+// admin made, and is counted among the bans made.
+func (l *Ledger) LoadEdit(bans []Ban) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.made[CauseAdmin] += l.load(bans)
+}
+
+// load does what Load describes, and returns how many of bans are bans
+// whose cause is CauseAdmin that the ledger did not hold before.
+func (l *Ledger) load(bans []Ban) int {
 	bans = slices.Clone(bans)
+	added := 0
+
+	for i := range bans {
+		ban := &bans[i]
+		ban.Netblock = ban.Netblock.Masked()
+		ban.Notes.Request = ban.Notes.Request.cut()
+
+		if ban.Cause == "" {
+			ban.Cause = CauseAdmin
+		}
+
+		if ban.Cause == CauseAdmin && !l.holds(ban.Netblock, ban.Start) {
+			added++
+		}
+	}
+
 	slices.SortStableFunc(bans, func(a, b Ban) int {
 		return a.Start.Compare(b.Start)
 	})

-	l.mu.Lock()
-	defer l.mu.Unlock()
-
 	l.netblocks.Purge()
 	l.held = 0
 	l.v4Lengths, l.v6Lengths = nil, nil

 	for _, ban := range bans {
-		ban.Netblock = ban.Netblock.Masked()
-		ban.Notes.Request = ban.Notes.Request.cut()
 		l.add(ban)
 	}
+
+	return added
 }

-// ban bans netblock at now for cause, with notes, as BanForLimit and
-// BanForAttack describe, and returns the ban.
+// holds reports whether the ledger holds a ban on netblock that started
+// at start.
+func (l *Ledger) holds(netblock netip.Prefix, start time.Time) bool {
+	bans, found := l.netblocks.Peek(netblock)
+
+	return found && slices.ContainsFunc(*bans, func(ban Ban) bool {
+		return ban.Start.Equal(start)
+	})
+}
+
+// ban bans netblock at now for cause, with reason and notes, as
+// BanForLimit and BanForAttack describe, and returns the ban.
 func (l *Ledger) ban(
-	netblock netip.Prefix, now time.Time, cause string, notes Notes,
+	netblock netip.Prefix, now time.Time, cause, reason string, notes Notes,
 ) Ban {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -363,7 +429,7 @@ func (l *Ledger) ban(
 	}

 	notes.Request = notes.Request.cut()
-	ban := Ban{Netblock: netblock, Start: now, Cause: cause, Notes: notes}
+	ban := Ban{Netblock: netblock, Start: now, Cause: cause, Reason: reason, Notes: notes}

 	if cause == CauseAttack {
 		ban.Expires = l.attackExpiry(held, now)
@@ -391,8 +457,8 @@ func earlierBans(held []Ban) EarlierBans {
 			earlier.Limit++
 		case CauseAttack:
 			earlier.Attack++
-		default:
-			earlier.WithoutCause++
+		case CauseAdmin:
+			earlier.Admin++
 		}
 	}

@@ -431,9 +497,11 @@ func (l *Ledger) active(client netip.Addr, now time.Time) *Ban {
 }

 // add adds ban to its netblock's bans, after the last, and makes its
-// netblock the most recently seen. With MaxBans held, it drops one first.
+// netblock the most recently seen. With MaxBans held, it drops one first,
+// unless ban's cause is CauseAdmin, which does not count toward MaxBans.
 func (l *Ledger) add(ban Ban) {
-	if l.held == l.rules.MaxBans {
+	counted := ban.Cause != CauseAdmin
+	if counted && l.held == l.rules.MaxBans {
 		l.dropOne()
 	}

@@ -446,7 +514,10 @@ func (l *Ledger) add(ban Ban) {
 	}

 	*bans = append(*bans, ban)
-	l.held++
+
+	if counted {
+		l.held++
+	}

 	lengths := &l.v6Lengths
 	if ban.Netblock.Addr().Is4() {
@@ -461,16 +532,17 @@ func (l *Ledger) add(ban Ban) {
 // limitExpiry returns when a ban for a broken limit made at now ends, or
 // zero when it is permanent. held are the netblock's bans, none of them
 // active, of which the one that ended last, other than a ban for a clear
-// sign of attack, can make the new ban longer. A ban an admin adds to
-// bans.json can start after another and end before it, so that one is
-// looked for among them all.
+// sign of attack or a lifted one, can make the new ban longer. A ban an
+// admin adds to bans.json can start after another and end before it, so
+// that one is looked for among them all.
 func (l *Ledger) limitExpiry(held []Ban, now time.Time) time.Time {
 	length := l.rules.LimitBanDuration

 	var last *Ban

 	for i, ban := range held {
-		if ban.Cause != CauseAttack && (last == nil || ban.Expires.After(last.Expires)) {
+		if ban.Cause != CauseAttack && ban.Lifted.IsZero() &&
+			(last == nil || ban.Expires.After(last.Expires)) {
 			last = &held[i]
 		}
 	}
@@ -495,11 +567,11 @@ func (l *Ledger) limitExpiry(held []Ban, now time.Time) time.Time {

 // attackExpiry returns when a ban for a clear sign of attack made at now
 // ends. held are the netblock's bans, none of them active: if one of them
-// is for a clear sign of attack too, the new ban is permanent, and its
-// end zero; otherwise it ends AttackBanDuration later.
+// is for a clear sign of attack too, and was not lifted, the new ban is
+// permanent, and its end zero; otherwise it ends AttackBanDuration later.
 func (l *Ledger) attackExpiry(held []Ban, now time.Time) time.Time {
 	for _, ban := range held {
-		if ban.Cause == CauseAttack {
+		if ban.Cause == CauseAttack && ban.Lifted.IsZero() {
 			return time.Time{}
 		}
 	}
@@ -507,17 +579,39 @@ func (l *Ledger) attackExpiry(held []Ban, now time.Time) time.Time {
 	return now.Add(l.rules.AttackBanDuration)
 }

-// dropOne drops the earliest ban of the netblock that has gone longest
-// without a request, and the netblock with it if that was its only ban.
+// dropOne drops the earliest ban whose cause is not CauseAdmin of the
+// netblock that has gone longest without a request, of those that hold
+// such a ban, and the netblock with it if that was its only ban. It is
+// called with at least one such ban held. It looks at each netblock once
+// at most, and drops nothing when none holds such a ban.
 func (l *Ledger) dropOne() {
-	netblock, bans, _ := l.netblocks.GetOldest()
-	if len(*bans) == 1 {
-		l.netblocks.Remove(netblock)
-	} else {
-		*bans = slices.Delete(*bans, 0, 1)
-	}
+	for range l.netblocks.Len() {
+		netblock, bans, _ := l.netblocks.GetOldest()

-	l.held--
+		i := slices.IndexFunc(*bans, func(ban Ban) bool {
+			return ban.Cause != CauseAdmin
+		})
+		if i < 0 {
+			// Its bans are all an admin's, and never dropped. Get makes
+			// it the most recently seen, so that the next netblock is
+			// looked at; when it was seen matters only for dropping a
+			// ban, and a ban added to it makes it the most recently seen
+			// anyway.
+			l.netblocks.Get(netblock)
+
+			continue
+		}
+
+		if len(*bans) == 1 {
+			l.netblocks.Remove(netblock)
+		} else {
+			*bans = slices.Delete(*bans, i, i+1)
+		}
+
+		l.held--
+
+		return
+	}
 }

 // cut returns r with each text cut to maxTextBytes and copied, so that