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link: rewrite height comparisons without subtraction

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Prevent the case where a uint32 wrap around could happen.
This commit is contained in:
Joost Jager 2019-04-05 10:50:00 +02:00
parent ab4da0f53d
commit 037913fd28
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GPG Key ID: A61B9D4C393C59C7
1 changed files with 7 additions and 6 deletions
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13
htlcswitch/link.go
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@ -2155,9 +2155,9 @@ func (l *channelLink) HtlcSatifiesPolicy(payHash [32]byte,
} }
// We want to avoid offering an HTLC which will expire in the near // We want to avoid offering an HTLC which will expire in the near
// future, so we'll reject an HTLC if the outgoing expiration time is too // future, so we'll reject an HTLC if the outgoing expiration time is
// close to the current height. // too close to the current height.
if outgoingTimeout-l.cfg.OutgoingCltvRejectDelta <= heightNow { if outgoingTimeout <= heightNow+l.cfg.OutgoingCltvRejectDelta {
l.errorf("htlc(%x) has an expiry that's too soon: "+ l.errorf("htlc(%x) has an expiry that's too soon: "+
"outgoing_expiry=%v, best_height=%v", payHash[:], "outgoing_expiry=%v, best_height=%v", payHash[:],
outgoingTimeout, heightNow) outgoingTimeout, heightNow)
@ -2175,7 +2175,8 @@ func (l *channelLink) HtlcSatifiesPolicy(payHash [32]byte,
return failure return failure
} }
if outgoingTimeout-heightNow > maxCltvExpiry { // Check absolute max delta.
if outgoingTimeout > maxCltvExpiry+heightNow {
l.errorf("outgoing htlc(%x) has a time lock too far in the "+ l.errorf("outgoing htlc(%x) has a time lock too far in the "+
"future: got %v, but maximum is %v", payHash[:], "future: got %v, but maximum is %v", payHash[:],
outgoingTimeout-heightNow, maxCltvExpiry) outgoingTimeout-heightNow, maxCltvExpiry)
@ -2188,7 +2189,7 @@ func (l *channelLink) HtlcSatifiesPolicy(payHash [32]byte,
// delta should equal the outgoing time lock. Otherwise, whether the // delta should equal the outgoing time lock. Otherwise, whether the
// sender messed up, or an intermediate node tampered with the HTLC. // sender messed up, or an intermediate node tampered with the HTLC.
timeDelta := policy.TimeLockDelta timeDelta := policy.TimeLockDelta
if incomingTimeout-timeDelta < outgoingTimeout { if incomingTimeout < outgoingTimeout+timeDelta {
l.errorf("Incoming htlc(%x) has incorrect time-lock value: "+ l.errorf("Incoming htlc(%x) has incorrect time-lock value: "+
"expected at least %v block delta, got %v block delta", "expected at least %v block delta, got %v block delta",
payHash[:], timeDelta, incomingTimeout-outgoingTimeout) payHash[:], timeDelta, incomingTimeout-outgoingTimeout)
@ -2680,7 +2681,7 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
// First, we'll check the expiry of the HTLC itself against, the current // First, we'll check the expiry of the HTLC itself against, the current
// block height. If the timeout is too soon, then we'll reject the HTLC. // block height. If the timeout is too soon, then we'll reject the HTLC.
if pd.Timeout-l.cfg.FinalCltvRejectDelta <= heightNow { if pd.Timeout <= heightNow+l.cfg.FinalCltvRejectDelta {
log.Errorf("htlc(%x) has an expiry that's too soon: expiry=%v"+ log.Errorf("htlc(%x) has an expiry that's too soon: expiry=%v"+
", best_height=%v", pd.RHash[:], pd.Timeout, heightNow) ", best_height=%v", pd.RHash[:], pd.Timeout, heightNow)