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// Copyright 2024 New Vector Ltd.
// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
// Please see LICENSE files in the repository root for full details.
package acls
import (
"context"
"encoding/json"
"fmt"
"net"
"regexp"
"strings"
"sync"
"time"
"github.com/element-hq/dendrite/roomserver/storage/tables"
"github.com/matrix-org/gomatrixserverlib/spec"
"github.com/sirupsen/logrus"
)
const MRoomServerACL = "m.room.server_acl"
type ServerACLDatabase interface {
// RoomsWithACLs returns all room IDs for rooms with ACLs
RoomsWithACLs(ctx context.Context) ([]string, error)
// GetBulkStateACLs returns all server ACLs for the given rooms.
GetBulkStateACLs(ctx context.Context, roomIDs []string) ([]tables.StrippedEvent, error)
}
type ServerACLs struct {
acls map[string]*serverACL // room ID -> ACL
aclsMutex sync.RWMutex // protects the above
aclRegexCache map[string]**regexp.Regexp // Cache from "serverName" -> pointer to a regex
aclRegexCacheMutex sync.RWMutex // protects the above
}
func NewServerACLs(db ServerACLDatabase) *ServerACLs {
// Add some logging, as this can take a while on larger instances.
logrus.Infof("Loading server ACLs...")
start := time.Now()
aclCount := 0
defer func() {
logrus.WithFields(logrus.Fields{
"duration": time.Since(start),
"acls": aclCount,
}).Info("Finished loading server ACLs")
}()
ctx := context.TODO()
acls := &ServerACLs{
acls: make(map[string]*serverACL),
// Be generous when creating the cache, as in reality
// there are hundreds of servers in an ACL.
aclRegexCache: make(map[string]**regexp.Regexp, 100),
}
// Look up all rooms with ACLs.
rooms, err := db.RoomsWithACLs(ctx)
if err != nil {
logrus.WithError(err).Fatalf("Failed to get known rooms")
}
// No rooms with ACLs, don't bother hitting the DB again.
if len(rooms) == 0 {
return acls
}
// Get ACLs for the required rooms, bail if we are unable to get them.
events, err := db.GetBulkStateACLs(ctx, rooms)
if err != nil {
logrus.WithError(err).Fatal("Failed to get server ACLs for all rooms")
}
aclCount = len(events)
for _, event := range events {
acls.OnServerACLUpdate(event)
}
return acls
}
type ServerACL struct {
Allowed []string `json:"allow"`
Denied []string `json:"deny"`
AllowIPLiterals bool `json:"allow_ip_literals"`
}
type serverACL struct {
ServerACL
allowedRegexes []**regexp.Regexp
deniedRegexes []**regexp.Regexp
}
func compileACLRegex(orig string) (*regexp.Regexp, error) {
escaped := regexp.QuoteMeta(orig)
escaped = strings.Replace(escaped, "\\?", ".", -1)
escaped = strings.Replace(escaped, "\\*", ".*", -1)
return regexp.Compile(escaped)
}
// cachedCompileACLRegex is a wrapper around compileACLRegex with added caching
func (s *ServerACLs) cachedCompileACLRegex(orig string) (**regexp.Regexp, error) {
s.aclRegexCacheMutex.RLock()
re, ok := s.aclRegexCache[orig]
if ok {
s.aclRegexCacheMutex.RUnlock()
return re, nil
}
s.aclRegexCacheMutex.RUnlock()
compiled, err := compileACLRegex(orig)
if err != nil {
return nil, err
}
s.aclRegexCacheMutex.Lock()
defer s.aclRegexCacheMutex.Unlock()
s.aclRegexCache[orig] = &compiled
return &compiled, nil
}
func (s *ServerACLs) OnServerACLUpdate(strippedEvent tables.StrippedEvent) {
acls := &serverACL{}
if err := json.Unmarshal([]byte(strippedEvent.ContentValue), &acls.ServerACL); err != nil {
logrus.WithError(err).Errorf("Failed to unmarshal state content for server ACLs")
return
}
// The spec calls only for * (zero or more chars) and ? (exactly one char)
// to be supported as wildcard components, so we will escape all of the regex
// special characters and then replace * and ? with their regex counterparts.
// https://matrix.org/docs/spec/client_server/r0.6.1#m-room-server-acl
for _, orig := range acls.Allowed {
if expr, err := s.cachedCompileACLRegex(orig); err != nil {
logrus.WithError(err).Errorf("Failed to compile allowed regex")
} else {
acls.allowedRegexes = append(acls.allowedRegexes, expr)
}
}
for _, orig := range acls.Denied {
if expr, err := s.cachedCompileACLRegex(orig); err != nil {
logrus.WithError(err).Errorf("Failed to compile denied regex")
} else {
acls.deniedRegexes = append(acls.deniedRegexes, expr)
}
}
logrus.WithFields(logrus.Fields{
"allow_ip_literals": acls.AllowIPLiterals,
"num_allowed": len(acls.allowedRegexes),
"num_denied": len(acls.deniedRegexes),
}).Debugf("Updating server ACLs for %q", strippedEvent.RoomID)
// Clear out Denied and Allowed, now that we have the compiled regexes.
// They are not needed anymore from this point on.
acls.Denied = nil
acls.Allowed = nil
s.aclsMutex.Lock()
defer s.aclsMutex.Unlock()
s.acls[strippedEvent.RoomID] = acls
}
func (s *ServerACLs) IsServerBannedFromRoom(serverName spec.ServerName, roomID string) bool {
s.aclsMutex.RLock()
// First of all check if we have an ACL for this room. If we don't then
// no servers are banned from the room.
acls, ok := s.acls[roomID]
if !ok {
s.aclsMutex.RUnlock()
return false
}
s.aclsMutex.RUnlock()
// Split the host and port apart. This is because the spec calls on us to
// validate the hostname only in cases where the port is also present.
if serverNameOnly, _, err := net.SplitHostPort(string(serverName)); err == nil {
serverName = spec.ServerName(serverNameOnly)
}
// Check if the hostname is an IPv4 or IPv6 literal. We cheat here by adding
// a /0 prefix length just to trick ParseCIDR into working. If we find that
// the server is an IP literal and we don't allow those then stop straight
// away.
if _, _, err := net.ParseCIDR(fmt.Sprintf("%s/0", serverName)); err == nil {
if !acls.AllowIPLiterals {
return true
}
}
// Check if the hostname matches one of the denied regexes. If it does then
// the server is banned from the room.
for _, expr := range acls.deniedRegexes {
if (*expr).MatchString(string(serverName)) {
return true
}
}
// Check if the hostname matches one of the allowed regexes. If it does then
// the server is NOT banned from the room.
for _, expr := range acls.allowedRegexes {
if (*expr).MatchString(string(serverName)) {
return false
}
}
// If we've got to this point then we haven't matched any regexes or an IP
// hostname if disallowed. The spec calls for default-deny here.
return true
}
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