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allow the first key update immediately after handshake confirmation

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This commit is contained in:
Marten Seemann 2020-09-30 14:12:07 +07:00
parent b9090d71ae
commit 1c38acd8c9
3 changed files with 87 additions and 56 deletions
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56
internal/handshake/updatable_aead.go
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@ -22,9 +22,10 @@ var KeyUpdateInterval uint64 = protocol.KeyUpdateInterval
type updatableAEAD struct {
suite *qtls.CipherSuiteTLS13
keyPhase protocol.KeyPhase
largestAcked protocol.PacketNumber
firstPacketNumber protocol.PacketNumber
keyPhase protocol.KeyPhase
largestAcked protocol.PacketNumber
firstPacketNumber protocol.PacketNumber
handshakeConfirmed bool
keyUpdateInterval uint64
invalidPacketLimit uint64
@ -172,35 +173,24 @@ func (a *updatableAEAD) open(dst, src []byte, rcvTime time.Time, pn protocol.Pac
}
binary.BigEndian.PutUint64(a.nonceBuf[len(a.nonceBuf)-8:], uint64(pn))
if kp != a.keyPhase.Bit() {
var receivedWrongInitialKeyPhase bool
if a.firstRcvdWithCurrentKey == protocol.InvalidPacketNumber || pn < a.firstRcvdWithCurrentKey {
if a.keyPhase == 0 {
// This can only occur when the first packet received has key phase 1.
// This is an error, since the key phase starts at 0,
// and peers are only allowed to update keys after the handshake is confirmed.
// Proceed from here, and only return an error if decryption of the packet succeeds.
receivedWrongInitialKeyPhase = true
} else {
if a.prevRcvAEAD == nil {
return nil, ErrKeysDropped
}
// we updated the key, but the peer hasn't updated yet
dec, err := a.prevRcvAEAD.Open(dst, a.nonceBuf, src, ad)
if err != nil {
err = ErrDecryptionFailed
}
return dec, err
if a.keyPhase > 0 && a.firstRcvdWithCurrentKey == protocol.InvalidPacketNumber || pn < a.firstRcvdWithCurrentKey {
if a.prevRcvAEAD == nil {
return nil, ErrKeysDropped
}
// we updated the key, but the peer hasn't updated yet
dec, err := a.prevRcvAEAD.Open(dst, a.nonceBuf, src, ad)
if err != nil {
err = ErrDecryptionFailed
}
return dec, err
}
// try opening the packet with the next key phase
dec, err := a.nextRcvAEAD.Open(dst, a.nonceBuf, src, ad)
if err == nil && receivedWrongInitialKeyPhase {
return nil, qerr.NewError(qerr.KeyUpdateError, "wrong initial key phase")
} else if err != nil {
if err != nil {
return nil, ErrDecryptionFailed
}
// Opening succeeded. Check if the peer was allowed to update.
if a.firstSentWithCurrentKey == protocol.InvalidPacketNumber {
if a.keyPhase > 0 && a.firstSentWithCurrentKey == protocol.InvalidPacketNumber {
return nil, qerr.NewError(qerr.KeyUpdateError, "keys updated too quickly")
}
a.rollKeys()
@ -256,10 +246,20 @@ func (a *updatableAEAD) SetLargestAcked(pn protocol.PacketNumber) error {
return nil
}
func (a *updatableAEAD) SetHandshakeConfirmed() {
a.handshakeConfirmed = true
}
func (a *updatableAEAD) updateAllowed() bool {
return a.firstSentWithCurrentKey != protocol.InvalidPacketNumber &&
a.largestAcked != protocol.InvalidPacketNumber &&
a.largestAcked >= a.firstSentWithCurrentKey
if !a.handshakeConfirmed {
return false
}
// the first key update is allowed as soon as the handshake is confirmed
return a.keyPhase == 0 ||
// subsequent key updates as soon as a packet sent with that key phase has been acknowledged
(a.firstSentWithCurrentKey != protocol.InvalidPacketNumber &&
a.largestAcked != protocol.InvalidPacketNumber &&
a.largestAcked >= a.firstSentWithCurrentKey)
}
func (a *updatableAEAD) shouldInitiateKeyUpdate() bool {