Merge pull request #285 from fancycode/reverse_sessionids

Reverse data in session ids.

go/channelling/tickets.go

@@ -34,6 +34,11 @@ import (
 	"github.com/gorilla/securecookie"
 )
 
+var (
+	// Can be set from tests to disable some log outputs.
+	silentOutput = false
+)
+
 type SessionValidator interface {
 	Realm() string
 	ValidateSession(string, string) bool
@@ -77,6 +82,27 @@ func (tickets *tickets) Realm() string {
 	return tickets.realm
 }
 
+func reverseBase64String(s string) (string, error) {
+	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 (tickets *tickets) reverseSessionId(id string) string {
+	reversedId, err := reverseBase64String(id)
+	if err != nil {
+		// This should never happen
+		panic("Could not reverse " + id)
+	}
+	return reversedId
+}
+
 func (tickets *tickets) DecodeSessionToken(token string) (st *SessionToken) {
 	var err error
 	if token != "" {
@@ -90,8 +116,11 @@ func (tickets *tickets) DecodeSessionToken(token string) (st *SessionToken) {
 	if st == nil || err != nil {
 		sid := randomstring.NewRandomString(32)
 		id, _ := tickets.Encode("id", sid)
+		id = tickets.reverseSessionId(id)
 		st = &SessionToken{Id: id, Sid: sid}
-		log.Println("Created new session id", id)
+		if !silentOutput {
+			log.Println("Created new session id", id)
+		}
 	}
 	return
 }
@@ -99,6 +128,7 @@ func (tickets *tickets) DecodeSessionToken(token string) (st *SessionToken) {
 func (tickets *tickets) FakeSessionToken(userid string) (st *SessionToken) {
 	sid := fmt.Sprintf("fake-%s", randomstring.NewRandomString(27))
 	id, _ := tickets.Encode("id", sid)
+	id = tickets.reverseSessionId(id)
 	st = &SessionToken{Id: id, Sid: sid, Userid: userid}
 	log.Println("Created new fake session id", st.Id)
 	return
@@ -106,12 +136,23 @@ func (tickets *tickets) FakeSessionToken(userid string) (st *SessionToken) {
 
 func (tickets *tickets) ValidateSession(id, sid string) bool {
 	var decoded string
-	if err := tickets.Decode("id", id, &decoded); err != nil {
-		log.Println("Session validation error", err, id, sid)
+	reversedId, err := reverseBase64String(id)
+	if err != nil {
+		if !silentOutput {
+			log.Println("Session format error", err, id, sid)
+		}
+		return false
+	}
+	if err := tickets.Decode("id", reversedId, &decoded); err != nil {
+		if !silentOutput {
+			log.Println("Session validation error", err, reversedId, sid)
+		}
 		return false
 	}
 	if decoded != sid {
-		log.Println("Session validation failed", id, sid)
+		if !silentOutput {
+			log.Println("Session validation failed", reversedId, sid)
+		}
 		return false
 	}
 	return true

go/channelling/tickets_test.go

@@ -0,0 +1,97 @@
+/*
+ * Spreed WebRTC.
+ * Copyright (C) 2016 struktur AG
+ *
+ * This file is part of Spreed WebRTC.
+ *
+ * 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 channelling
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"testing"
+)
+
+func getRandom(n int) ([]byte, error) {
+	result := make([]byte, n)
+	if _, err := rand.Read(result); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func Test_ReverseBase64(t *testing.T) {
+	for i := 0; i < 1000; i++ {
+		data, err := getRandom(64)
+		if err != nil {
+			t.Errorf("Could not get random data: %v", err)
+			continue
+		}
+
+		s := base64.URLEncoding.EncodeToString(data)
+		reversed, err := reverseBase64String(s)
+		if err != nil {
+			t.Errorf("Could not reverse %s: %v", s, err)
+			continue
+		}
+
+		if s == reversed {
+			t.Errorf("Reversing should be different for %s", s)
+		}
+
+		original, err := reverseBase64String(reversed)
+		if err != nil {
+			t.Errorf("Could not reverse back %s: %v", reversed, err)
+			continue
+		}
+
+		if s != original {
+			t.Errorf("Reversing back should have restored %s from %s but got %s", s, reversed, original)
+		}
+	}
+}
+
+func Test_Sessions(t *testing.T) {
+	sessionSecret, err := getRandom(64)
+	if err != nil {
+		t.Fatalf("Could not create session secret: %v", err)
+		return
+	}
+
+	encryptionSecret, err := getRandom(32)
+	if err != nil {
+		t.Fatalf("Could not create encryption secret: %v", err)
+		return
+	}
+
+	tickets := NewTickets(sessionSecret, encryptionSecret, "test")
+	silentOutput = true
+	for i := 0; i < 1000; i++ {
+		st := tickets.DecodeSessionToken("")
+		if st == nil {
+			t.Error("Could not create session")
+			continue
+		}
+
+		if !tickets.ValidateSession(st.Id, st.Sid) {
+			t.Errorf("Session is invalid: %v", st)
+			continue
+		}
+	}
+	silentOutput = false
+}