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p2p: make RLPx frame MAC 16 bytes as defined in the spec

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This commit is contained in:
Felix Lange 2015-02-27 14:08:57 +01:00
parent d084aed5e9
commit d344054e5a
2 changed files with 19 additions and 13 deletions
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31
p2p/rlpx.go
View File

@ -62,12 +62,15 @@ func (rw *rlpxFrameRW) WriteMsg(msg Msg) error {
putInt24(fsize, headbuf) // TODO: check overflow
copy(headbuf[3:], zeroHeader)
rw.enc.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now encrypted
copy(headbuf[16:], updateHeaderMAC(rw.egressMAC, rw.macCipher, headbuf[:16]))
// write header MAC
copy(headbuf[16:], updateMAC(rw.egressMAC, rw.macCipher, headbuf[:16]))
if _, err := rw.conn.Write(headbuf); err != nil {
return err
}
// write encrypted frame, updating the egress MAC while writing to conn.
// write encrypted frame, updating the egress MAC hash with
// the data written to conn.
tee := cipher.StreamWriter{S: rw.enc, W: io.MultiWriter(rw.conn, rw.egressMAC)}
if _, err := tee.Write(ptype); err != nil {
return err
@ -81,9 +84,10 @@ func (rw *rlpxFrameRW) WriteMsg(msg Msg) error {
}
}
// write packet-mac. egress MAC is up to date because
// write frame MAC. egress MAC hash is up to date because
// frame content was written to it as well.
mac := updateHeaderMAC(rw.egressMAC, rw.macCipher, rw.egressMAC.Sum(nil))
fmacseed := rw.egressMAC.Sum(nil)
mac := updateMAC(rw.egressMAC, rw.macCipher, fmacseed)
_, err := rw.conn.Write(mac)
return err
}
@ -95,8 +99,8 @@ func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
return msg, err
}
// verify header mac
shouldMAC := updateHeaderMAC(rw.ingressMAC, rw.macCipher, headbuf[:16])
if !hmac.Equal(shouldMAC[:16], headbuf[16:]) {
shouldMAC := updateMAC(rw.ingressMAC, rw.macCipher, headbuf[:16])
if !hmac.Equal(shouldMAC, headbuf[16:]) {
return msg, errors.New("bad header MAC")
}
rw.dec.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now decrypted
@ -115,11 +119,12 @@ func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
// read and validate frame MAC. we can re-use headbuf for that.
rw.ingressMAC.Write(framebuf)
if _, err := io.ReadFull(rw.conn, headbuf); err != nil {
fmacseed := rw.ingressMAC.Sum(nil)
if _, err := io.ReadFull(rw.conn, headbuf[:16]); err != nil {
return msg, err
}
shouldMAC = updateHeaderMAC(rw.ingressMAC, rw.macCipher, rw.ingressMAC.Sum(nil))
if !hmac.Equal(shouldMAC, headbuf) {
shouldMAC = updateMAC(rw.ingressMAC, rw.macCipher, fmacseed)
if !hmac.Equal(shouldMAC, headbuf[:16]) {
return msg, errors.New("bad frame MAC")
}
@ -136,14 +141,16 @@ func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
return msg, nil
}
func updateHeaderMAC(mac hash.Hash, block cipher.Block, header []byte) []byte {
// updateMAC reseeds the given hash with encrypted seed.
// it returns the first 16 bytes of the hash sum after seeding.
func updateMAC(mac hash.Hash, block cipher.Block, seed []byte) []byte {
aesbuf := make([]byte, aes.BlockSize)
block.Encrypt(aesbuf, mac.Sum(nil))
for i := range aesbuf {
aesbuf[i] ^= header[i]
aesbuf[i] ^= seed[i]
}
mac.Write(aesbuf)
return mac.Sum(nil)
return mac.Sum(nil)[:16]
}
func readInt24(b []byte) uint32 {

1
p2p/rlpx_test.go
View File

@ -29,7 +29,6 @@ func TestRlpxFrameFake(t *testing.T) {
01010101010101010101010101010101
ba628a4ba590cb43f7848f41c4382885
01010101010101010101010101010101
01010101010101010101010101010101
`)
// Check WriteMsg. This puts a message into the buffer.