forked from mutecomm/mute
/
clientmix.go
177 lines (165 loc) · 5.45 KB
/
clientmix.go
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// Copyright (c) 2015 Mute Communications Ltd.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package mixcrypt
import (
"crypto/sha256"
"encoding/asn1"
"encoding/binary"
"fmt"
"github.com/mutecomm/mute/mix/nymaddr"
)
// ClientMixHeader contains fields meant by the Client for the Mix
type ClientMixHeader struct {
MessageType int32 // The type of the message (forward/relay). Forward does not have NymAddress/RevokeID set
SenderMinDelay, SenderMaxDelay int32
Token []byte // Payment Token
Address []byte // NymAddress for relay, next mix for forward
RevokeID []byte // Revokation secret
}
// ReceiveStruct contains data gathered from receiving a message
type ReceiveStruct struct {
MixHeader *ClientMixHeader
NymAddress *nymaddr.Address
NymAddressPrivate *nymaddr.AddressPrivate
UniqueTest []UniquenessData
Message []byte
}
// UniquenessData contains the hash and expire time for a uniqueness-check
type UniquenessData struct {
Hash []byte
Expire int64
}
// Marshal a ClientMixHeader
func (cl ClientMixHeader) Marshal() []byte {
if cl.Token == nil {
cl.Token = []byte{0x00}
}
if cl.RevokeID == nil || cl.MessageType == MessageTypeForward {
cl.RevokeID = []byte{0x00}
}
d, err := asn1.Marshal(cl)
if err != nil {
panic(err) // Should never happen
}
ret := make([]byte, len(d)+2)
binary.BigEndian.PutUint16(ret[0:2], uint16(len(d)))
copy(ret[2:], d)
return ret
}
// Unmarshal a binary ClientMixHeader. Returns header length to allow working with full-message slices
func (cl *ClientMixHeader) Unmarshal(d []byte) (header *ClientMixHeader, headerlen uint16, err error) {
if len(d) < 3 {
return nil, 0, ErrTooShort
}
if cl == nil {
cl = new(ClientMixHeader)
}
lenB := binary.BigEndian.Uint16(d[0:2]) + 2
if len(d) < int(lenB) {
return nil, lenB, ErrTooShort
}
_, err = asn1.Unmarshal(d[2:lenB], cl)
if err != nil {
return nil, lenB, err
}
if cl.Token[0] == 0x00 && len(cl.Token) == 1 {
cl.Token = nil
}
if (cl.RevokeID[0] == 0x00 && len(cl.RevokeID) == 1) || cl.MessageType == MessageTypeForward {
cl.RevokeID = nil
}
return cl, lenB, nil
}
// NewForwardMessage creates a new message with type MessageTypeForward. Uses ClientMixHeader SenderMinDelay,SenderMaxDelay,Token
func (cl *ClientMixHeader) NewForwardMessage(NextHop string, NextHopKey *[KeySize]byte, msg []byte) (message []byte, deliverAddress string, err error) {
if cl == nil {
cl = new(ClientMixHeader)
}
cl.MessageType = MessageTypeForward
cl.Address = []byte(NextHop)
header := cl.Marshal()
messageC := make([]byte, len(header)+len(msg))
copy(messageC[0:len(header)], header)
copy(messageC[len(header):], msg)
msgEncrypted, err := Encrypt(NextHopKey, nil, messageC)
return msgEncrypted, NextHop, err
}
// NewRelayMessage creates a new message with type MessageTypeRelay. Uses ClientMixHeader SenderMinDelay,SenderMaxDelay,Token. Sets revokeID
func (cl *ClientMixHeader) NewRelayMessage(NymAddress []byte, msg []byte) (message []byte, deliverAddress string, err error) {
if cl == nil {
cl = new(ClientMixHeader)
}
address, err := nymaddr.ParseAddress(NymAddress)
if err != nil {
return nil, "", err
}
NextHopKey := new([KeySize]byte)
copy(NextHopKey[:], address.MixPubKey)
cl.MessageType = MessageTypeRelay
cl.Address = NymAddress
revokeID, _ := genNonce()
cl.RevokeID = revokeID[:]
header := cl.Marshal()
messageC := make([]byte, len(header)+len(msg))
copy(messageC[0:len(header)], header)
copy(messageC[len(header):], msg)
msgEncrypted, err := Encrypt(NextHopKey, nil, messageC)
return msgEncrypted, string(address.MixAddress), err
}
func mkHash(d []byte) []byte {
x := sha256.Sum256(d)
return x[:]
}
// ReceiveMessage receives a Client-Mix message
func ReceiveMessage(lookupKey KeyFunc, message []byte) (*ReceiveStruct, error) {
// var uniqueDat []UniquenessData
var rstr ReceiveStruct
var lenB uint16
decMessage, err := Decrypt(lookupKey, message)
if err != nil {
return nil, err
}
rstr.MixHeader, lenB, err = new(ClientMixHeader).Unmarshal(decMessage)
if err != nil {
return nil, err
}
// Test Size
msgLen := len(decMessage) - int(lenB)
if rstr.MixHeader.MessageType == MessageTypeRelay && (msgLen < RelayMinSize || msgLen > RelayMaxSize) {
fmt.Println(msgLen)
return nil, ErrSize
}
if rstr.MixHeader.MessageType == MessageTypeForward && (msgLen < ForwardMinSize || msgLen > ForwardMaxSize) {
return nil, ErrSize
}
// Uniqueness data collection
if rstr.MixHeader.MessageType == MessageTypeRelay {
rstr.NymAddress, err = nymaddr.ParseAddress(rstr.MixHeader.Address)
if err != nil {
return nil, err
}
rstr.NymAddressPrivate, err = rstr.NymAddress.GetMixData(nymaddr.KeyFunc(lookupKey))
if err != nil {
return nil, err
}
// First 256byte of message
rstr.UniqueTest = append(rstr.UniqueTest, UniquenessData{
Expire: rstr.NymAddressPrivate.Expire,
Hash: mkHash(decMessage[lenB : lenB+256]), // First 256 byte of message
})
if rstr.NymAddressPrivate.SingleUse {
rstr.UniqueTest = append(rstr.UniqueTest, UniquenessData{
Expire: rstr.NymAddressPrivate.Expire,
Hash: rstr.NymAddressPrivate.ReceiverPubKey,
})
}
} else {
rstr.UniqueTest = append(rstr.UniqueTest, UniquenessData{
Expire: timeNow() + ExpireReceive,
Hash: mkHash(decMessage[lenB : lenB+256]), // First 256 byte of message
})
}
rstr.Message = decMessage[lenB:]
return &rstr, nil
}