mirror of
https://github.com/fiatjaf/khatru.git
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111 lines
3.3 KiB
Go
111 lines
3.3 KiB
Go
package policies
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import (
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"context"
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"github.com/nbd-wtf/go-nostr"
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"golang.org/x/exp/slices"
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)
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// PreventTooManyIndexableTags returns a function that can be used as a RejectFilter that will reject
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// events with more indexable (single-character) tags than the specified number.
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//
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// If ignoreKinds is given this restriction will not apply to these kinds (useful for allowing a bigger).
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// If onlyKinds is given then all other kinds will be ignored.
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func PreventTooManyIndexableTags(max int, ignoreKinds []int, onlyKinds []int) func(context.Context, *nostr.Event) (bool, string) {
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ignore := func(kind int) bool { return false }
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if len(ignoreKinds) > 0 {
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ignore = func(kind int) bool {
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_, isIgnored := slices.BinarySearch(ignoreKinds, kind)
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return isIgnored
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}
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}
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if len(onlyKinds) > 0 {
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ignore = func(kind int) bool {
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_, isApplicable := slices.BinarySearch(onlyKinds, kind)
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return !isApplicable
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}
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}
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return func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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if ignore(event.Kind) {
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return false, ""
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}
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ntags := 0
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for _, tag := range event.Tags {
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if len(tag) > 0 && len(tag[0]) == 1 {
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ntags++
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}
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}
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if ntags > max {
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return true, "too many indexable tags"
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}
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return false, ""
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}
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}
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// PreventLargeTags rejects events that have indexable tag values greater than maxTagValueLen.
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func PreventLargeTags(maxTagValueLen int) func(context.Context, *nostr.Event) (bool, string) {
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return func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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for _, tag := range event.Tags {
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if len(tag) > 1 && len(tag[0]) == 1 {
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if len(tag[1]) > maxTagValueLen {
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return true, "event contains too large tags"
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}
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}
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}
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return false, ""
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}
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}
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// RestrictToSpecifiedKinds returns a function that can be used as a RejectFilter that will reject
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// any events with kinds different than the specified ones.
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func RestrictToSpecifiedKinds(kinds ...uint16) func(context.Context, *nostr.Event) (bool, string) {
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max := 0
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min := 0
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for _, kind := range kinds {
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if int(kind) > max {
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max = int(kind)
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}
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if int(kind) < min {
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min = int(kind)
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}
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}
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return func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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// these are cheap and very questionable optimizations, but they exist for a reason:
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// we would have to ensure that the kind number is within the bounds of a uint16 anyway
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if event.Kind > max {
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return true, "event kind not allowed"
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}
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if event.Kind < min {
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return true, "event kind not allowed"
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}
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// hopefully this map of uint16s is very fast
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if _, allowed := slices.BinarySearch(kinds, uint16(event.Kind)); allowed {
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return false, ""
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}
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return true, "event kind not allowed"
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}
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}
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func PreventTimestampsInThePast(thresholdSeconds nostr.Timestamp) func(context.Context, *nostr.Event) (bool, string) {
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return func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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if nostr.Now()-event.CreatedAt > thresholdSeconds {
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return true, "event too old"
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}
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return false, ""
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}
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}
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func PreventTimestampsInTheFuture(thresholdSeconds nostr.Timestamp) func(context.Context, *nostr.Event) (bool, string) {
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return func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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if event.CreatedAt-nostr.Now() > thresholdSeconds {
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return true, "event too much in the future"
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}
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return false, ""
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}
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}
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