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// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package acls
import (
"context"
"encoding/json"
"fmt"
"net"
"regexp"
"strings"
"sync"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/gomatrixserverlib/spec"
"github.com/sirupsen/logrus"
)
type ServerACLDatabase interface {
// GetKnownRooms returns a list of all rooms we know about.
GetKnownRooms(ctx context.Context) ([]string, error)
// GetStateEvent returns the state event of a given type for a given room with a given state key
// If no event could be found, returns nil
// If there was an issue during the retrieval, returns an error
GetStateEvent(ctx context.Context, roomID, evType, stateKey string) (*gomatrixserverlib.HeaderedEvent, error)
}
type ServerACLs struct {
acls map[string]*serverACL // room ID -> ACL
aclsMutex sync.RWMutex // protects the above
}
func NewServerACLs(db ServerACLDatabase) *ServerACLs {
ctx := context.TODO()
acls := &ServerACLs{
acls: make(map[string]*serverACL),
}
// Look up all of the rooms that the current state server knows about.
rooms, err := db.GetKnownRooms(ctx)
if err != nil {
logrus.WithError(err).Fatalf("Failed to get known rooms")
}
// For each room, let's see if we have a server ACL state event. If we
// do then we'll process it into memory so that we have the regexes to
// hand.
for _, room := range rooms {
state, err := db.GetStateEvent(ctx, room, "m.room.server_acl", "")
if err != nil {
logrus.WithError(err).Errorf("Failed to get server ACLs for room %q", room)
continue
}
if state != nil {
acls.OnServerACLUpdate(state.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)
}
func (s *ServerACLs) OnServerACLUpdate(state *gomatrixserverlib.Event) {
acls := &serverACL{}
if err := json.Unmarshal(state.Content(), &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 := compileACLRegex(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 := compileACLRegex(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", state.RoomID())
s.aclsMutex.Lock()
defer s.aclsMutex.Unlock()
s.acls[state.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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