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header.go
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header.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 msg
import (
"encoding/binary"
"encoding/hex"
"encoding/json"
"io"
"github.com/mutecomm/mute/cipher"
"github.com/mutecomm/mute/encode/base64"
"github.com/mutecomm/mute/keyserver/hashchain"
"github.com/mutecomm/mute/log"
"github.com/mutecomm/mute/msg/padding"
"github.com/mutecomm/mute/uid"
"github.com/mutecomm/mute/uid/identity"
"github.com/mutecomm/mute/uid/length"
"github.com/mutecomm/mute/util/digits"
"golang.org/x/crypto/nacl/box"
)
// lengthEncryptedHeader defines the length of an encrypted header.
// This must always be the same in all messages! 5852 + 1316 = 7168.
const lengthEncryptedHeader = 7168
// Some wiggle room which can be taken out of padding if the need arises.
const wiggleRoom = 1316
// StatusCode is the type of header status codes.
type StatusCode uint8
// Possible header status codes.
const (
StatusOK = 0
StatusReset = 1
StatusError = 2
)
type header struct {
Ciphersuite string // ciphersuite to use (header encryption is always NaCL)
RecipientPubHash string // SHA512(RecipientIdentityPub)
RecipientTempHash string // SHA512(RecipientKeyInitPub) || SHA512(RecipientSessionPub)
SenderIdentity string // identity of sender
SenderSessionPub uid.KeyEntry // public key of sender session
SenderIdentityPubHash string // SHA512(SenderIdentityPub)
SenderIdentityPub uid.KeyEntry // duplicate from SenderUID for easy parsing
NextSenderSessionPub *uid.KeyEntry // optional
NextRecipientSessionPubSeen *uid.KeyEntry // only if seen
NymAddress string // address to receive future messages at
MaxDelay uint64 // TODO
SenderSessionCount uint64 // total number of messages sent in sessions before this SenderSessionPub was used
SenderMessageCount uint64 // total number of messages sent with this SenderSessionPub
SenderUID string // complete UID message in JSON
SenderLastKeychainHash string // last entry known to sender from keyserver hashchain
Status StatusCode // always a single digit in JSON!
Padding string // header padding
}
type headerPacket struct {
Nonce [24]byte // for NaCL
LengthEncryptedHeader uint16 // the length of the encrypted header
EncryptedHeader []byte // the actual encrypted header
}
func newHeader(
sender, recipient *uid.Message,
recipientTempHash string,
senderSessionPub, nextSenderSessionPub,
nextRecipientSessionPubSeen *uid.KeyEntry,
nymAddress string,
senderSessionCount, senderMessageCount uint64,
senderLastKeychainHash string,
rand io.Reader,
statusCode StatusCode,
) (*header, error) {
if len(senderLastKeychainHash) != hashchain.EntryBase64Len {
return nil, log.Errorf("msg: last hashchain entry '%s' does not have base64 length %d (but %d)",
senderLastKeychainHash, hashchain.EntryBase64Len, len(senderLastKeychainHash))
}
h := &header{
Ciphersuite: uid.DefaultCiphersuite, // at the moment we only support one ciphersuite
RecipientPubHash: recipient.PubHash(),
RecipientTempHash: recipientTempHash,
SenderIdentity: sender.Identity(),
SenderSessionPub: *senderSessionPub,
SenderIdentityPubHash: sender.PubHash(),
SenderIdentityPub: *sender.PubKey(),
NextSenderSessionPub: nextSenderSessionPub,
NextRecipientSessionPubSeen: nextRecipientSessionPubSeen,
NymAddress: nymAddress,
MaxDelay: 0, // TODO
SenderSessionCount: senderSessionCount,
SenderMessageCount: senderMessageCount,
SenderUID: string(sender.JSON()),
SenderLastKeychainHash: senderLastKeychainHash,
Status: statusCode,
Padding: "", // is set below
}
// calculate padding length
padLen := wiggleRoom
// pad sender identity
if len(h.SenderIdentity) > identity.MaxLen {
return nil, log.Error("msg: sender identity is too long")
}
padLen += identity.MaxLen - len(h.SenderIdentity)
// pad nextSenderSessionPub
if nextSenderSessionPub == nil {
padLen += length.KeyEntryECDHE25519 - length.Nil
}
// pad nextRecipientSessionPubSeen
if nextRecipientSessionPubSeen == nil {
padLen += length.KeyEntryECDHE25519 - length.Nil
}
// pad nym address
if len(h.NymAddress) > length.MaxNymAddress {
return nil, log.Error("msg: nym address is too long")
}
padLen += length.MaxNymAddress - len(h.NymAddress)
// pad integers
padLen += 20 - digits.Count(h.MaxDelay)
padLen += 20 - digits.Count(h.SenderSessionCount)
padLen += 20 - digits.Count(h.SenderMessageCount)
// pad sender UIDMessage
if len(h.SenderUID) > length.MaxUIDMessage {
return nil, log.Error("msg: sender UIDMesssage is too long")
}
padLen += length.MaxUIDMessage - len(h.SenderUID)
// generate padding
randLen := padLen/2 + padLen%2
pad, err := padding.Generate(randLen, cipher.RandReader)
if err != nil {
return nil, err
}
// set padding
p := hex.EncodeToString(pad)
if padLen%2 == 1 {
p = p[:len(p)-1]
}
h.Padding = p
return h, nil
}
func newHeaderPacket(
h *header,
recipientIdentityPub, senderHeaderPriv *[32]byte,
rand io.Reader,
) (*headerPacket, error) {
var hp headerPacket
jsn, err := json.Marshal(h)
if err != nil {
return nil, err
}
if _, err := io.ReadFull(rand, hp.Nonce[:]); err != nil {
return nil, log.Error(err)
}
log.Debugf("recvPub=%s\n", base64.Encode(recipientIdentityPub[:]))
hp.EncryptedHeader = box.Seal(hp.EncryptedHeader, jsn, &hp.Nonce,
recipientIdentityPub, senderHeaderPriv)
hp.LengthEncryptedHeader = uint16(len(hp.EncryptedHeader))
if hp.LengthEncryptedHeader != lengthEncryptedHeader {
return nil,
log.Errorf("msg: encrypted header has wrong length (%d != %d)",
hp.LengthEncryptedHeader, lengthEncryptedHeader)
}
return &hp, nil
}
func (hp *headerPacket) write(w io.Writer) error {
//log.Debugf("hp.Nonce: %s", base64.Encode(hp.Nonce[:]))
if _, err := w.Write(hp.Nonce[:]); err != nil {
return log.Error(err)
}
//log.Debugf("hp.LengthEncryptedHeader: %d", hp.LengthEncryptedHeader)
if err := binary.Write(w, binary.BigEndian, hp.LengthEncryptedHeader); err != nil {
return log.Error(err)
}
if _, err := w.Write(hp.EncryptedHeader); err != nil {
return log.Error(err)
}
return nil
}
func readHeader(
senderHeaderPub *[32]byte,
identities []*uid.Message,
r io.Reader,
) (*uid.Message, *header, error) {
var hp headerPacket
// read nonce
if _, err := io.ReadFull(r, hp.Nonce[:]); err != nil {
return nil, nil, log.Error(err)
}
//log.Debugf("hp.Nonce: %s", base64.Encode(hp.Nonce[:]))
// read length of encrypted header
if err := binary.Read(r, binary.BigEndian, &hp.LengthEncryptedHeader); err != nil {
return nil, nil, log.Error(err)
}
//log.Debugf("hp.LengthEncryptedHeader: %d", hp.LengthEncryptedHeader)
// read encrypted header
hp.EncryptedHeader = make([]byte, hp.LengthEncryptedHeader)
if _, err := io.ReadFull(r, hp.EncryptedHeader); err != nil {
return nil, nil, log.Error(err)
}
// try to decrypt header
var jsn []byte
var suc bool
var identity *uid.Message
for _, uidMsg := range identities {
log.Debugf("try identity %s (#%d)", uidMsg.Identity(),
uidMsg.UIDContent.MSGCOUNT)
log.Debugf("recvPub=%s\n",
base64.Encode(uidMsg.PubKey().PublicKey32()[:]))
jsn, suc = box.Open(jsn, hp.EncryptedHeader, &hp.Nonce,
senderHeaderPub, uidMsg.PubKey().PrivateKey32())
if suc {
identity = uidMsg
break
}
}
if !suc {
return nil, nil, log.Error(ErrNoPreHeaderKey)
}
var h header
if err := json.Unmarshal(jsn, &h); err != nil {
return nil, nil, err
}
// verify header
if err := h.verify(); err != nil {
return nil, nil, err
}
return identity, &h, nil
}
// Verify KeyEntry messages in header.
func (h *header) verify() error {
// check h.SenderSessionPub
if err := h.SenderSessionPub.Verify(); err != nil {
return err
}
if h.SenderSessionPub.FUNCTION != "ECDHE25519" {
return log.Errorf("msg: wrong uid.SenderSessionPub.FUNCTION: %s",
h.SenderSessionPub.FUNCTION)
}
// check h.SenderIdentityPub
if err := h.SenderIdentityPub.Verify(); err != nil {
return err
}
if h.SenderIdentityPub.FUNCTION != "ECDHE25519" {
return log.Errorf("msg: wrong uid.SenderIdentityPub.FUNCTION: %s",
h.SenderIdentityPub.FUNCTION)
}
// check h.NextSenderSessionPub
if h.NextSenderSessionPub != nil {
if err := h.NextSenderSessionPub.Verify(); err != nil {
return err
}
if h.NextSenderSessionPub.FUNCTION != "ECDHE25519" {
return log.Errorf("msg: wrong uid.NextSenderSessionPub.FUNCTION: %s",
h.SenderSessionPub.FUNCTION)
}
}
// check h.NextRecipientSessionPubSeen
if h.NextRecipientSessionPubSeen != nil {
if err := h.NextRecipientSessionPubSeen.Verify(); err != nil {
return err
}
if h.NextRecipientSessionPubSeen.FUNCTION != "ECDHE25519" {
return log.Errorf("msg: wrong uid.NextRecipientSessionPubSeen.FUNCTION: %s",
h.NextRecipientSessionPubSeen.FUNCTION)
}
}
return nil
}