130 lines
3.1 KiB
Go
130 lines
3.1 KiB
Go
package p2p
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"errors"
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"hash"
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"io"
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"github.com/ethereum/go-ethereum/rlp"
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)
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var (
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zeroHeader = []byte{0xC2, 0x80, 0x80}
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zero16 = make([]byte, 16)
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)
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type rlpxFrameRW struct {
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conn io.ReadWriter
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macCipher cipher.Block
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egressMAC hash.Hash
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ingressMAC hash.Hash
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}
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func newRlpxFrameRW(conn io.ReadWriter, macSecret []byte, egressMAC, ingressMAC hash.Hash) *rlpxFrameRW {
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cipher, err := aes.NewCipher(macSecret)
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if err != nil {
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panic("invalid macSecret: " + err.Error())
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}
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return &rlpxFrameRW{conn: conn, macCipher: cipher, egressMAC: egressMAC, ingressMAC: ingressMAC}
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}
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func (rw *rlpxFrameRW) WriteMsg(msg Msg) error {
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ptype, _ := rlp.EncodeToBytes(msg.Code)
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// write header
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headbuf := make([]byte, 32)
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fsize := uint32(len(ptype)) + msg.Size
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putInt24(fsize, headbuf) // TODO: check overflow
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copy(headbuf[3:], zeroHeader)
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copy(headbuf[16:], updateHeaderMAC(rw.egressMAC, rw.macCipher, headbuf[:16]))
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if _, err := rw.conn.Write(headbuf); err != nil {
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return err
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}
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// write frame, updating the egress MAC while writing to conn.
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tee := io.MultiWriter(rw.conn, rw.egressMAC)
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if _, err := tee.Write(ptype); err != nil {
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return err
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}
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if _, err := io.Copy(tee, msg.Payload); err != nil {
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return err
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}
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if padding := fsize % 16; padding > 0 {
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if _, err := tee.Write(zero16[:16-padding]); err != nil {
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return err
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}
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}
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// write packet-mac. egress MAC is up to date because
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// frame content was written to it as well.
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_, err := rw.conn.Write(rw.egressMAC.Sum(nil))
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return err
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}
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func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
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// read the header
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headbuf := make([]byte, 32)
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if _, err := io.ReadFull(rw.conn, headbuf); err != nil {
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return msg, err
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}
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fsize := readInt24(headbuf)
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// ignore protocol type for now
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shouldMAC := updateHeaderMAC(rw.ingressMAC, rw.macCipher, headbuf[:16])
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if !hmac.Equal(shouldMAC[:16], headbuf[16:]) {
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return msg, errors.New("bad header MAC")
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}
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// read the frame content
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framebuf := make([]byte, fsize)
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if _, err := io.ReadFull(rw.conn, framebuf); err != nil {
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return msg, err
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}
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rw.ingressMAC.Write(framebuf)
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if padding := fsize % 16; padding > 0 {
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if _, err := io.CopyN(rw.ingressMAC, rw.conn, int64(16-padding)); err != nil {
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return msg, err
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}
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}
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// read and validate frame MAC. we can re-use headbuf for that.
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if _, err := io.ReadFull(rw.conn, headbuf); err != nil {
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return msg, err
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}
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if !hmac.Equal(rw.ingressMAC.Sum(nil), headbuf) {
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return msg, errors.New("bad frame MAC")
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}
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// decode message code
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content := bytes.NewReader(framebuf)
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if err := rlp.Decode(content, &msg.Code); err != nil {
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return msg, err
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}
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msg.Size = uint32(content.Len())
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msg.Payload = content
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return msg, nil
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}
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func updateHeaderMAC(mac hash.Hash, block cipher.Block, header []byte) []byte {
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aesbuf := make([]byte, aes.BlockSize)
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block.Encrypt(aesbuf, mac.Sum(nil))
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for i := range aesbuf {
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aesbuf[i] ^= header[i]
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}
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mac.Write(aesbuf)
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return mac.Sum(nil)
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}
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func readInt24(b []byte) uint32 {
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return uint32(b[2]) | uint32(b[1])<<8 | uint32(b[0])<<16
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}
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func putInt24(v uint32, b []byte) {
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b[0] = byte(v >> 16)
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b[1] = byte(v >> 8)
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b[2] = byte(v)
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}
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