/usr/share/gocode/src/github.com/twstrike/otr3/data_message.go is in golang-github-twstrike-otr3-dev 0.0~git20161015.0.744856d-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import "encoding/binary"
type dataMessageExtra struct {
key []byte
}
func (c *Conversation) genDataMsg(message []byte, tlvs ...tlv) (dataMsg, dataMessageExtra, error) {
return c.genDataMsgWithFlag(message, messageFlagNormal, tlvs...)
}
func (c *Conversation) genDataMsgWithFlag(message []byte, flag byte, tlvs ...tlv) (dataMsg, dataMessageExtra, error) {
if c.msgState != encrypted {
return dataMsg{}, dataMessageExtra{}, newOtrConflictError("cannot send message in unencrypted state")
}
keys, err := c.keys.calculateDHSessionKeys(c.keys.ourKeyID-1, c.keys.theirKeyID, c.version)
if err != nil {
return dataMsg{}, dataMessageExtra{}, err
}
topHalfCtr := [8]byte{}
counter := c.keys.counterHistory.findCounterFor(c.keys.ourKeyID-1, c.keys.theirKeyID)
if counter.ourCounter == 0 {
counter.ourCounter = 1
}
binary.BigEndian.PutUint64(topHalfCtr[:], counter.ourCounter)
counter.ourCounter++
plain := plainDataMsg{
message: message,
tlvs: tlvs,
}
encrypted := plain.encrypt(keys.sendingAESKey[:], topHalfCtr)
header, err := c.messageHeader(msgTypeData)
if err != nil {
return dataMsg{}, dataMessageExtra{}, err
}
dataMessage := dataMsg{
flag: flag,
senderKeyID: c.keys.ourKeyID - 1,
recipientKeyID: c.keys.theirKeyID,
y: c.keys.ourCurrentDHKeys.pub,
topHalfCtr: topHalfCtr,
encryptedMsg: encrypted,
oldMACKeys: c.keys.revealMACKeys(),
}
// fmt.Printf("sendingMACKey: len: %d %X\n", len(keys.sendingMACKey), keys.sendingMACKey)
dataMessage.sign(keys.sendingMACKey, header, c.version)
c.updateMayRetransmitTo(noRetransmit)
c.lastMessage(message)
x := dataMessageExtra{keys.extraKey[:]}
return dataMessage, x, nil
}
func extractDataMessageFlag(msg []byte) byte {
if len(msg) == 0 {
return messageFlagNormal
}
return msg[0]
}
func (c *Conversation) createSerializedDataMessage(msg []byte, flag byte, tlvs []tlv) ([]ValidMessage, dataMessageExtra, error) {
dataMsg, x, err := c.genDataMsgWithFlag(msg, flag, tlvs...)
if err != nil {
return nil, dataMessageExtra{}, err
}
res, err := c.wrapMessageHeader(msgTypeData, dataMsg.serialize(c.version))
if err != nil {
return nil, dataMessageExtra{}, err
}
c.updateLastSent()
return c.fragEncode(res), x, nil
}
func (c *Conversation) fragEncode(msg messageWithHeader) []ValidMessage {
return c.fragment(c.encode(msg), c.fragmentSize)
}
func (c *Conversation) encode(msg messageWithHeader) encodedMessage {
return append(append(msgMarker, b64encode(msg)...), '.')
}
func (c *Conversation) processDataMessage(header, msg []byte) (plain MessagePlaintext, toSend messageWithHeader, err error) {
ignoreUnreadable := (extractDataMessageFlag(msg) & messageFlagIgnoreUnreadable) == messageFlagIgnoreUnreadable
plain, toSend, err = c.processDataMessageWithRawErrors(header, msg)
if err != nil && ignoreUnreadable {
err = nil
}
return
}
// processDataMessageWithRawErrors receives a decoded incoming message and returns the plain text inside that message
// and a data message (with header) generated in response to any TLV contained in the incoming message.
// The header and message compose the decoded incoming message.
func (c *Conversation) processDataMessageWithRawErrors(header, msg []byte) (plain MessagePlaintext, toSend messageWithHeader, err error) {
dataMessage := dataMsg{}
if c.msgState != encrypted {
err = errMessageNotInPrivate
c.messageEvent(MessageEventReceivedMessageNotInPrivate)
return
}
if err = dataMessage.deserialize(msg, c.version); err != nil {
return
}
if err = c.keys.checkMessageCounter(dataMessage); err != nil {
return
}
sessionKeys, err := c.keys.calculateDHSessionKeys(dataMessage.recipientKeyID, dataMessage.senderKeyID, c.version)
if err != nil {
return
}
if err = dataMessage.checkSign(sessionKeys.receivingMACKey, header, c.version); err != nil {
return
}
p := plainDataMsg{}
//this can't return an error since receivingAESKey is a AES-128 key
p.decrypt(sessionKeys.receivingAESKey[:], dataMessage.topHalfCtr, dataMessage.encryptedMsg)
plain = makeCopy(p.message)
if len(plain) == 0 {
plain = nil
c.messageEvent(MessageEventLogHeartbeatReceived)
}
err = c.rotateKeys(dataMessage)
if err != nil {
return
}
var tlvs []tlv
tlvs, err = c.processTLVs(p.tlvs, dataMessageExtra{sessionKeys.extraKey})
if err != nil {
return
}
if len(tlvs) > 0 {
var reply dataMsg
reply, _, err = c.genDataMsgWithFlag(nil, decideFlagFrom(tlvs), tlvs...)
if err != nil {
return
}
toSend, err = c.wrapMessageHeader(msgTypeData, reply.serialize(c.version))
if err != nil {
return
}
}
return
}
func decideFlagFrom(tlvs []tlv) byte {
flag := byte(0x00)
for _, t := range tlvs {
if t.tlvType >= tlvTypeSMP1 && t.tlvType <= tlvTypeSMP1WithQuestion {
flag = messageFlagIgnoreUnreadable
}
}
return flag
}
func (c *Conversation) processSMPTLV(t tlv, x dataMessageExtra) (toSend *tlv, err error) {
c.smp.ensureSMP()
smpMessage, ok := t.smpMessage()
if !ok {
return nil, newOtrError("corrupt data message")
}
return c.receiveSMP(smpMessage)
}
func (c *Conversation) processTLVs(tlvs []tlv, x dataMessageExtra) ([]tlv, error) {
var retTLVs []tlv
for _, t := range tlvs {
mh, e := messageHandlerForTLV(t)
if e != nil {
continue
}
toSend, err := mh(c, t, x)
if err != nil {
//We assume this will only happen if the message was sent by a
//malicious/broken client and it's reasonable to stop processing the
//remaining TLVs and consider the entire TLVs block as corrupted.
//Any valid SMP TLV processed before the error can potentially cause a side
//effect on the SMP state machine and we wont reply (take the bait).
return nil, err
}
if toSend != nil {
retTLVs = append(retTLVs, *toSend)
}
}
return retTLVs, nil
}
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