Shuffle ciphers

shadowsocks/cipher_map.go

@@ -0,0 +1,37 @@
+// Copyright 2018 Jigsaw Operations LLC
+//
+// 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
+//
+//     https://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 shadowsocks
+
+import (
+	"math/rand"
+
+	"github.com/shadowsocks/go-shadowsocks2/shadowaead"
+)
+
+type cipherEntry struct {
+	id     string
+	cipher shadowaead.Cipher
+}
+
+func shuffleCipherMap(cipherMap map[string]shadowaead.Cipher) []cipherEntry {
+	cipherArray := make([]cipherEntry, len(cipherMap))
+	perm := rand.Perm(len(cipherMap))
+	i := 0
+	for id, cipher := range cipherMap {
+		cipherArray[perm[i]] = cipherEntry{id, cipher}
+		i++
+	}
+	return cipherArray
+}

shadowsocks/tcp.go

@@ -48,7 +48,7 @@ func ensureBytes(reader io.Reader, buf []byte, bytesNeeded int) ([]byte, error)
 	return buf, err
 }
 
-func findAccessKey(clientConn onet.DuplexConn, cipherList map[string]shadowaead.Cipher) (string, onet.DuplexConn, error) {
+func findAccessKey(clientConn onet.DuplexConn, cipherMap map[string]shadowaead.Cipher) (string, onet.DuplexConn, error) {
 	// This must have enough space to hold the salt + 2 bytes chunk length + AEAD tag (Oeverhead) for any cipher
 	replayBytes := make([]byte, 0, 32+2+16)
 	// Constant of zeroes to use as the start chunk count. This must be as big as the max NonceSize() across all ciphers.
@@ -57,11 +57,12 @@ func findAccessKey(clientConn onet.DuplexConn, cipherList map[string]shadowaead.
 	chunkLenBuf := [2]byte{}
 	var err error
 
-	// Try each cipher until we find one that authenticates successfully.
-	// This assumes that all ciphers are AEAD.
+	// Try each cipher until we find one that authenticates successfully. This assumes that all ciphers are AEAD.
+	// We shuffle the cipher map so that every connection has the same expected time.
 	// TODO: Reorder list to try previously successful ciphers first for the client IP.
 	// TODO: Ban and log client IPs with too many failures too quick to protect against DoS.
-	for id, cipher := range cipherList {
+	for _, entry := range shuffleCipherMap(cipherMap) {
+		id, cipher := entry.id, entry.cipher
 		replayBytes, err = ensureBytes(clientConn, replayBytes, cipher.SaltSize())
 		if err != nil {
 			if logger.IsEnabledFor(logging.DEBUG) {
@@ -114,6 +115,36 @@ type TCPService interface {
 	Stop() error
 }
 
+// proxyConnection will route the clientConn according to the address read from the connection.
+func proxyConnection(clientConn onet.DuplexConn, proxyMetrics *metrics.ProxyMetrics) *onet.ConnectionError {
+	tgtAddr, err := socks.ReadAddr(clientConn)
+	if err != nil {
+		return onet.NewConnectionError("ERR_READ_ADDRESS", "Failed to get target address", err)
+	}
+	tgtTCPAddr, err := net.ResolveTCPAddr("tcp", tgtAddr.String())
+	if err != nil {
+		return onet.NewConnectionError("ERR_RESOLVE_ADDRESS", fmt.Sprintf("Failed to resolve target address %v", tgtAddr.String()), err)
+	}
+	if !tgtTCPAddr.IP.IsGlobalUnicast() {
+		return onet.NewConnectionError("ERR_ADDRESS_INVALID", fmt.Sprintf("Target address is not global unicast: %v", tgtAddr.String()), err)
+	}
+
+	tgtTCPConn, err := net.DialTCP("tcp", nil, tgtTCPAddr)
+	if err != nil {
+		return onet.NewConnectionError("ERR_CONNECT", "Failed to connect to target", err)
+	}
+	defer tgtTCPConn.Close()
+	tgtTCPConn.SetKeepAlive(true)
+	tgtConn := metrics.MeasureConn(tgtTCPConn, &proxyMetrics.ProxyTarget, &proxyMetrics.TargetProxy)
+
+	logger.Debugf("proxy %s <-> %s", clientConn.RemoteAddr().String(), tgtConn.RemoteAddr().String())
+	_, _, err = onet.Relay(clientConn, tgtConn)
+	if err != nil {
+		return onet.NewConnectionError("ERR_RELAY", "Failed to relay traffic", err)
+	}
+	return nil
+}
+
 func (s *tcpService) Start() {
 	s.isRunning = true
 	for s.isRunning {
@@ -161,33 +192,7 @@ func (s *tcpService) Start() {
 				return onet.NewConnectionError("ERR_CIPHER", "Failed to find a valid cipher", err)
 			}
 
-			tgtAddr, err := socks.ReadAddr(clientConn)
-			if err != nil {
-				return onet.NewConnectionError("ERR_READ_ADDRESS", "Failed to get target address", err)
-			}
-			tgtTCPAddr, err := net.ResolveTCPAddr("tcp", tgtAddr.String())
-			if err != nil {
-				return onet.NewConnectionError("ERR_RESOLVE_ADDRESS", fmt.Sprintf("Failed to resolve target address %v", tgtAddr.String()), err)
-			}
-			if !tgtTCPAddr.IP.IsGlobalUnicast() {
-				return onet.NewConnectionError("ERR_ADDRESS_INVALID", fmt.Sprintf("Target address is not global unicast: %v", tgtAddr.String()), err)
-			}
-
-			tgtTCPConn, err := net.DialTCP("tcp", nil, tgtTCPAddr)
-			if err != nil {
-				return onet.NewConnectionError("ERR_CONNECT", "Failed to connect to target", err)
-			}
-			defer tgtTCPConn.Close()
-			tgtTCPConn.SetKeepAlive(true)
-			tgtConn := metrics.MeasureConn(tgtTCPConn, &proxyMetrics.ProxyTarget, &proxyMetrics.TargetProxy)
-
-			// TODO: Disable logging in production. This is sensitive.
-			logger.Debugf("proxy %s <-> %s", clientConn.RemoteAddr().String(), tgtConn.RemoteAddr().String())
-			_, _, err = onet.Relay(clientConn, tgtConn)
-			if err != nil {
-				return onet.NewConnectionError("ERR_RELAY", "Failed to relay traffic", err)
-			}
-			return nil
+			return proxyConnection(clientConn, &proxyMetrics)
 		}()
 	}
 }

shadowsocks/udp.go

@@ -35,8 +35,11 @@ const udpBufSize = 64 * 1024
 
 // upack decrypts src into dst. It tries each cipher until it finds one that authenticates
 // correctly. dst and src must not overlap.
-func unpack(dst, src []byte, ciphers map[string]shadowaead.Cipher) ([]byte, string, shadowaead.Cipher, error) {
-	for id, cipher := range ciphers {
+func unpack(dst, src []byte, cipherMap map[string]shadowaead.Cipher) ([]byte, string, shadowaead.Cipher, error) {
+	// Try each cipher until we find one that authenticates successfully. This assumes that all ciphers are AEAD.
+	// We shuffle the cipher map so that every connection has the same expected time.
+	for _, entry := range shuffleCipherMap(cipherMap) {
+		id, cipher := entry.id, entry.cipher
 		buf, err := shadowaead.Unpack(dst, src, cipher)
 		if err != nil {
 			if logger.IsEnabledFor(logging.DEBUG) {
@@ -61,8 +64,8 @@ type udpService struct {
 }
 
 // NewUDPService creates a UDPService
-func NewUDPService(clientConn net.PacketConn, natTimeout time.Duration, ciphers *map[string]shadowaead.Cipher, m metrics.ShadowsocksMetrics) UDPService {
-	return &udpService{clientConn: clientConn, natTimeout: natTimeout, ciphers: ciphers, m: m}
+func NewUDPService(clientConn net.PacketConn, natTimeout time.Duration, cipherMap *map[string]shadowaead.Cipher, m metrics.ShadowsocksMetrics) UDPService {
+	return &udpService{clientConn: clientConn, natTimeout: natTimeout, ciphers: cipherMap, m: m}
 }
 
 // UDPService is a UDP shadowsocks service that can be started and stopped.