/usr/share/gocode/src/github.com/twstrike/otr3/auth_state_machine.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 (
"bytes"
"time"
)
const minimumMessageLength = 3 // length of protocol version (SHORT) and message type (BYTE)
func (c *Conversation) generateNewDHKeyPair() error {
return c.keys.generateNewDHKeyPair(c.rand())
}
func (c *Conversation) akeHasFinished() error {
c.keys.wipe()
c.keys = c.ake.keys
c.ake.wipe(false)
previousMsgState := c.msgState
c.lastMessageStateChange = time.Now()
c.msgState = encrypted
defer c.signalSecurityEventIf(previousMsgState != encrypted, GoneSecure)
defer c.signalSecurityEventIf(previousMsgState == encrypted, StillSecure)
if c.ourCurrentKey.PublicKey().IsSame(c.theirKey) {
c.messageEvent(MessageEventMessageReflected)
}
return c.generateNewDHKeyPair()
}
func (c *Conversation) processAKE(msgType byte, msg []byte) (toSend []messageWithHeader, err error) {
c.ensureAKE()
var toSendSingle messageWithHeader
var toSendExtra []messageWithHeader
switch msgType {
case msgTypeDHCommit:
c.ake.state, toSendSingle, err = c.ake.state.receiveDHCommitMessage(c, msg)
case msgTypeDHKey:
c.ake.state, toSendSingle, err = c.ake.state.receiveDHKeyMessage(c, msg)
case msgTypeRevealSig:
c.ake.state, toSendSingle, err = c.ake.state.receiveRevealSigMessage(c, msg)
toSendExtra, _ = c.maybeRetransmit()
case msgTypeSig:
c.ake.state, toSendSingle, err = c.ake.state.receiveSigMessage(c, msg)
toSendExtra, _ = c.maybeRetransmit()
default:
err = newOtrErrorf("unknown message type 0x%X", msgType)
}
c.ake.lastStateChange = time.Now()
messages := append([]messageWithHeader{toSendSingle}, toSendExtra...)
toSend = compactMessagesWithHeader(messages...)
return
}
type authStateBase struct{}
type authStateNone struct{ authStateBase }
type authStateAwaitingDHKey struct{ authStateBase }
type authStateAwaitingRevealSig struct{ authStateBase }
type authStateAwaitingSig struct {
authStateBase
// revealSigMsg is only used to store the message so we can re-transmit it if needed
revealSigMsg messageWithHeader
}
type authState interface {
receiveDHCommitMessage(*Conversation, []byte) (authState, messageWithHeader, error)
receiveDHKeyMessage(*Conversation, []byte) (authState, messageWithHeader, error)
receiveRevealSigMessage(*Conversation, []byte) (authState, messageWithHeader, error)
receiveSigMessage(*Conversation, []byte) (authState, messageWithHeader, error)
identity() int
identityString() string
}
func (authStateBase) receiveDHCommitMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return authStateNone{}.receiveDHCommitMessage(c, msg)
}
func (s authStateNone) receiveDHCommitMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
c.ake.wipe(true)
dhKeyMsg, err := c.dhKeyMessage()
if err != nil {
return s, nil, err
}
dhKeyMsg, err = c.wrapMessageHeader(msgTypeDHKey, dhKeyMsg)
if err != nil {
return s, nil, err
}
if err = c.processDHCommit(msg); err != nil {
return s, nil, err
}
return authStateAwaitingRevealSig{}, dhKeyMsg, nil
}
func (s authStateAwaitingRevealSig) receiveDHCommitMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
//As per spec, we forget the old DH-commit (received before we sent the DH-Key)
//and use this one, so we forget all the keys
c.ake.keys = c.ake.keys.wipeAndKeepRevealKeys()
c.ake.wipeGX()
if err := c.processDHCommit(msg); err != nil {
return s, nil, err
}
dhKeyMsg, err := c.wrapMessageHeader(msgTypeDHKey, c.serializeDHKey())
if err != nil {
return s, nil, err
}
return authStateAwaitingRevealSig{}, dhKeyMsg, nil
}
func (s authStateAwaitingDHKey) receiveDHCommitMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
newMsg, _, ok1 := extractData(msg)
_, theirHashedGx, ok2 := extractData(newMsg)
if !ok1 || !ok2 {
return s, nil, errInvalidOTRMessage
}
gxMPI := appendMPI(nil, c.ake.ourPublicValue)
hashedGx := c.version.hash2(gxMPI)
//If yours is the higher hash value:
//Ignore the incoming D-H Commit message, but resend your D-H Commit message.
if bytes.Compare(hashedGx[:], theirHashedGx) == 1 {
dhCommitMsg, err := c.wrapMessageHeader(msgTypeDHCommit, c.serializeDHCommit(c.ake.ourPublicValue))
if err != nil {
return s, nil, err
}
return authStateAwaitingRevealSig{}, dhCommitMsg, nil
}
//Otherwise:
//Forget your old gx value that you sent (encrypted) earlier, and pretend you're in AUTHSTATE_NONE; i.e. reply with a D-H Key Message, and transition authstate to AUTHSTATE_AWAITING_REVEALSIG.
//This is done as part of receiving a DHCommit message in AUTHSTATE_NONE
return authStateNone{}.receiveDHCommitMessage(c, msg)
}
func (s authStateNone) receiveDHKeyMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingRevealSig) receiveDHKeyMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingDHKey) receiveDHKeyMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
_, err := c.processDHKey(msg)
if err != nil {
return s, nil, err
}
var revealSigMsg []byte
if revealSigMsg, err = c.revealSigMessage(); err != nil {
return s, nil, err
}
revealSigMsg, err = c.wrapMessageHeader(msgTypeRevealSig, revealSigMsg)
if err != nil {
return s, nil, err
}
c.ake.keys.setTheirCurrentDHPubKey(c.ake.theirPublicValue)
c.ake.keys.setOurCurrentDHKeys(c.ake.secretExponent, c.ake.ourPublicValue)
c.sentRevealSig = true
return authStateAwaitingSig{revealSigMsg: revealSigMsg}, revealSigMsg, nil
}
func (s authStateAwaitingSig) receiveDHKeyMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
isSame, err := c.processDHKey(msg)
if err != nil {
return s, nil, err
}
if isSame {
// Retransmit the Reveal Signature Message
return s, s.revealSigMsg, nil
}
return s, nil, nil
}
func (s authStateNone) receiveRevealSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingRevealSig) receiveRevealSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
err := c.processRevealSig(msg)
if err != nil {
return s, nil, err
}
sigMsg, err := c.sigMessage()
if err != nil {
return s, nil, err
}
sigMsg, err = c.wrapMessageHeader(msgTypeSig, sigMsg)
if err != nil {
return s, nil, err
}
c.ake.keys.setTheirCurrentDHPubKey(c.ake.theirPublicValue)
c.ake.keys.setOurCurrentDHKeys(c.ake.secretExponent, c.ake.ourPublicValue)
c.sentRevealSig = false
return authStateNone{}, sigMsg, c.akeHasFinished()
}
func (s authStateAwaitingDHKey) receiveRevealSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingSig) receiveRevealSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateNone) receiveSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingRevealSig) receiveSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingDHKey) receiveSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
return s, nil, nil
}
func (s authStateAwaitingSig) receiveSigMessage(c *Conversation, msg []byte) (authState, messageWithHeader, error) {
err := c.processSig(msg)
if err != nil {
return s, nil, err
}
//gy was stored when we receive DH-Key
c.ake.keys.setTheirCurrentDHPubKey(c.ake.theirPublicValue)
return authStateNone{}, nil, c.akeHasFinished()
}
func (authStateNone) String() string { return "AUTHSTATE_NONE" }
func (authStateAwaitingDHKey) String() string { return "AUTHSTATE_AWAITING_DHKEY" }
func (authStateAwaitingRevealSig) String() string { return "AUTHSTATE_AWAITING_REVEALSIG" }
func (authStateAwaitingSig) String() string { return "AUTHSTATE_AWAITING_SIG" }
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