Fix handshake peer identification

[govpn.git] / src / cypherpunks.ru / govpn / identity.go

diff --git a/src/cypherpunks.ru/govpn/identity.go b/src/cypherpunks.ru/govpn/identity.go
index f85631b01839639b8bf981572f4c8b6db106c984..d738c5563e091179bd1e1fa287fb1bbcbd6ef1d9 100644 (file)
--- a/src/cypherpunks.ru/govpn/identity.go
+++ b/src/cypherpunks.ru/govpn/identity.go
@@ -1,6 +1,6 @@
 /*
 GoVPN -- simple secure free software virtual private network daemon
-Copyright (C) 2014-2016 Sergey Matveev <stargrave@stargrave.org>
+Copyright (C) 2014-2017 Sergey Matveev <stargrave@stargrave.org>
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -22,11 +22,12 @@ import (
        "crypto/subtle"
        "encoding/base64"
        "encoding/binary"
+       "hash"
        "log"
        "sync"
        "time"
 
-       "golang.org/x/crypto/xtea"
+       "golang.org/x/crypto/blake2b"
 )
 
 const (
@@ -43,42 +44,46 @@ func (id PeerId) MarshalJSON() ([]byte, error) {
        return []byte(`"` + id.String() + `"`), nil
 }
 
-type CipherAndTimeSync struct {
-       c *xtea.Cipher
-       t int
+type MACAndTimeSync struct {
+       mac hash.Hash
+       ts  int
+       l   sync.Mutex
 }
 
-type CipherCache struct {
-       c map[PeerId]*CipherAndTimeSync
-       l sync.RWMutex
+type MACCache struct {
+       cache map[PeerId]*MACAndTimeSync
+       l     sync.RWMutex
 }
 
-func NewCipherCache() *CipherCache {
-       return &CipherCache{c: make(map[PeerId]*CipherAndTimeSync)}
+func NewMACCache() *MACCache {
+       return &MACCache{cache: make(map[PeerId]*MACAndTimeSync)}
 }
 
-// Remove disappeared keys, add missing ones with initialized ciphers.
-func (cc *CipherCache) Update(peers *map[PeerId]*PeerConf) {
-       cc.l.Lock()
-       for pid, _ := range cc.c {
+// Remove disappeared keys, add missing ones with initialized MACs.
+func (mc *MACCache) Update(peers *map[PeerId]*PeerConf) {
+       mc.l.Lock()
+       for pid, _ := range mc.cache {
                if _, exists := (*peers)[pid]; !exists {
                        log.Println("Cleaning key:", pid)
-                       delete(cc.c, pid)
+                       delete(mc.cache, pid)
                }
        }
        for pid, pc := range *peers {
-               if _, exists := cc.c[pid]; exists {
-                       cc.c[pid].t = pc.TimeSync
+               if _, exists := mc.cache[pid]; exists {
+                       mc.cache[pid].ts = pc.TimeSync
                } else {
                        log.Println("Adding key", pid)
-                       cipher, err := xtea.NewCipher(pid[:])
+                       mac, err := blake2b.New256(pid[:])
                        if err != nil {
                                panic(err)
                        }
-                       cc.c[pid] = &CipherAndTimeSync{cipher, pc.TimeSync}
+                       mc.cache[pid] = &MACAndTimeSync{
+                               mac: mac,
+                               ts:  pc.TimeSync,
+                       }
                }
        }
-       cc.l.Unlock()
+       mc.l.Unlock()
 }
 
 // If timeSync > 0, then XOR timestamp with the data.
@@ -93,24 +98,29 @@ func AddTimeSync(ts int, data []byte) {
        }
 }
 
-// Try to find peer's identity (that equals to an encryption key)
+// Try to find peer's identity (that equals to MAC)
 // by taking first blocksize sized bytes from data at the beginning
 // as plaintext and last bytes as cyphertext.
-func (cc *CipherCache) Find(data []byte) *PeerId {
-       if len(data) < xtea.BlockSize*2 {
+func (mc *MACCache) Find(data []byte) *PeerId {
+       if len(data) < 8*2 {
                return nil
        }
-       buf := make([]byte, xtea.BlockSize)
-       cc.l.RLock()
-       for pid, ct := range cc.c {
-               ct.c.Decrypt(buf, data[len(data)-xtea.BlockSize:])
-               AddTimeSync(ct.t, buf)
-               if subtle.ConstantTimeCompare(buf, data[:xtea.BlockSize]) == 1 {
+       buf := make([]byte, 8)
+       mc.l.RLock()
+       for pid, mt := range mc.cache {
+               copy(buf, data)
+               AddTimeSync(mt.ts, buf)
+               mt.l.Lock()
+               mt.mac.Reset()
+               mt.mac.Write(buf)
+               sum := mt.mac.Sum(nil)
+               mt.l.Unlock()
+               if subtle.ConstantTimeCompare(sum[len(sum)-8:], data[len(data)-8:]) == 1 {
                        ppid := PeerId(pid)
-                       cc.l.RUnlock()
+                       mc.l.RUnlock()
                        return &ppid
                }
        }
-       cc.l.RUnlock()
+       mc.l.RUnlock()
        return nil
 }