init

utils/packet_init.go

@@ -0,0 +1,79 @@
+package utils
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"encoding/binary"
+	"errors"
+	"hash/crc64"
+)
+
+type PacketInitType uint8
+
+const (
+	PacketInitTypeReq PacketInitType = iota // PacketInitTypeReq request RSA pubkey (by client)
+	PacketInitTypeAck                       // PacketInitTypeAck give the key
+	PacketInitTypeTop
+)
+
+// NewPacketInit x509rsapubkey = nil for req
+func NewPacketInit(aescipher cipher.Block, x509rsapubkey []byte) ([]byte, error) {
+	if len(x509rsapubkey) == 0 {
+		return []byte{byte(PacketInitTypeReq)}, nil
+	}
+	blksz := aescipher.BlockSize()
+	total := 2 + len(x509rsapubkey) + 8
+	n := total / blksz
+	if total%blksz > 0 {
+		n++
+	}
+	data := make([]byte, 1+blksz*n)
+	data[0] = byte(PacketInitTypeAck)
+	encdat := data[1:]
+	binary.LittleEndian.PutUint16(encdat[:2], uint16(len(x509rsapubkey)))
+	h := crc64.New(crc64.MakeTable(crc64.ECMA))
+	_, err := h.Write(x509rsapubkey)
+	if err != nil {
+		return nil, err
+	}
+	_ = h.Sum(encdat[2 : 2 : 2+8])
+	copy(encdat[2+8:], x509rsapubkey)
+	err = EncryptAESInplace(aescipher, encdat)
+	if err != nil {
+		return nil, err
+	}
+	return data, nil
+}
+
+// ParsePacketInit parse a init packet
+func ParsePacketInit(aescipher cipher.Block, d []byte) (x509rsapubkey []byte, err error) {
+	if len(d) == 0 {
+		err = errors.New("invalid init packet length")
+		return
+	}
+	if d[0] >= byte(PacketInitTypeTop) {
+		err = errors.New("invalid init packet type")
+		return
+	}
+	if d[0] == byte(PacketInitTypeReq) {
+		return
+	}
+	data := DecryptAES(aescipher, d[1:])
+	klen := binary.LittleEndian.Uint16(data[:2])
+	if int(klen) > len(data[10:]) {
+		err = errors.New("invalid init packet data length")
+		return
+	}
+	x509rsapubkey = data[10 : 10+klen]
+	h := crc64.New(crc64.MakeTable(crc64.ECMA))
+	_, err = h.Write(x509rsapubkey)
+	if err != nil {
+		return nil, err
+	}
+	var buf [8]byte
+	if !bytes.Equal(data[2:2+8], h.Sum(buf[:0])) {
+		err = errors.New("invalid init packet data")
+		return
+	}
+	return
+}