package client import ( "encoding/binary" "github.com/cbeuw/Cloak/internal/util" "net" log "github.com/sirupsen/logrus" ) type browser interface { composeClientHello(chHiddenData) []byte } func makeServerName(serverName string) []byte { serverNameListLength := make([]byte, 2) binary.BigEndian.PutUint16(serverNameListLength, uint16(len(serverName)+3)) serverNameType := []byte{0x00} // host_name serverNameLength := make([]byte, 2) binary.BigEndian.PutUint16(serverNameLength, uint16(len(serverName))) ret := make([]byte, 2+1+2+len(serverName)) copy(ret[0:2], serverNameListLength) copy(ret[2:3], serverNameType) copy(ret[3:5], serverNameLength) copy(ret[5:], serverName) return ret } // addExtensionRecord, add type, length to extension data func addExtRec(typ []byte, data []byte) []byte { length := make([]byte, 2) binary.BigEndian.PutUint16(length, uint16(len(data))) ret := make([]byte, 2+2+len(data)) copy(ret[0:2], typ) copy(ret[2:4], length) copy(ret[4:], data) return ret } func PrepareConnection(sta *State, conn net.Conn) (sessionKey []byte, err error) { hd, sharedSecret := makeHiddenData(sta) chOnly := sta.browser.composeClientHello(hd) chWithRecordLayer := util.AddRecordLayer(chOnly, []byte{0x16}, []byte{0x03, 0x01}) _, err = conn.Write(chWithRecordLayer) if err != nil { return } log.Trace("client hello sent successfully") buf := make([]byte, 1024) log.Trace("waiting for ServerHello") _, err = util.ReadTLS(conn, buf) if err != nil { return } encrypted := append(buf[11:43], buf[89:121]...) nonce := encrypted[0:12] ciphertext := encrypted[12:60] sessionKey, err = util.AESGCMDecrypt(nonce, sharedSecret, ciphertext) if err != nil { return } for i := 0; i < 2; i++ { // ChangeCipherSpec and EncryptedCert (in the format of application data) _, err = util.ReadTLS(conn, buf) if err != nil { return } } return sessionKey, nil }