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/**
* Standalone signaling server for the Nextcloud Spreed app.
* Copyright (C) 2024 struktur AG
*
* @author Joachim Bauch <bauch@struktur.de>
*
* @license GNU AGPL version 3 or any later version
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package signaling
import (
"encoding/base64"
"fmt"
"github.com/gorilla/securecookie"
"google.golang.org/protobuf/proto"
)
type protoSerializer struct {
}
func (s *protoSerializer) Serialize(src interface{}) ([]byte, error) {
msg, ok := src.(proto.Message)
if !ok {
return nil, fmt.Errorf("can't serialize type %T", src)
}
return proto.Marshal(msg)
}
func (s *protoSerializer) Deserialize(src []byte, dst interface{}) error {
msg, ok := dst.(proto.Message)
if !ok {
return fmt.Errorf("can't deserialize type %T", src)
}
return proto.Unmarshal(src, msg)
}
const (
privateSessionName = "private-session"
publicSessionName = "public-session"
)
type SessionIdCodec struct {
cookie *securecookie.SecureCookie
}
func NewSessionIdCodec(hashKey []byte, blockKey []byte) *SessionIdCodec {
cookie := securecookie.New(hashKey, blockKey).
MaxAge(0).
SetSerializer(&protoSerializer{})
return &SessionIdCodec{
cookie: cookie,
}
}
func (c *SessionIdCodec) EncodePrivate(sessionData *SessionIdData) (string, error) {
return c.cookie.Encode(privateSessionName, sessionData)
}
func reverseSessionId(s string) (string, error) {
// Note that we are assuming base64 encoded strings here.
decoded, err := base64.URLEncoding.DecodeString(s)
if err != nil {
return "", err
}
for i, j := 0, len(decoded)-1; i < j; i, j = i+1, j-1 {
decoded[i], decoded[j] = decoded[j], decoded[i]
}
return base64.URLEncoding.EncodeToString(decoded), nil
}
func (c *SessionIdCodec) EncodePublic(sessionData *SessionIdData) (string, error) {
encoded, err := c.cookie.Encode(publicSessionName, sessionData)
if err != nil {
return "", err
}
// We are reversing the public session ids because clients compare them
// to decide who calls whom. The prefix of the session id is increasing
// (a timestamp) but the suffix the (random) hash.
// By reversing we move the hash to the front, making the comparison of
// session ids "random".
return reverseSessionId(encoded)
}
func (c *SessionIdCodec) DecodePrivate(encodedData string) (*SessionIdData, error) {
var data SessionIdData
if err := c.cookie.Decode(privateSessionName, encodedData, &data); err != nil {
return nil, err
}
return &data, nil
}
func (c *SessionIdCodec) DecodePublic(encodedData string) (*SessionIdData, error) {
encodedData, err := reverseSessionId(encodedData)
if err != nil {
return nil, err
}
var data SessionIdData
if err := c.cookie.Decode(publicSessionName, encodedData, &data); err != nil {
return nil, err
}
return &data, nil
}
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