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decrypt in place

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This commit is contained in:
JackDoan
2026-07-15 09:16:40 -05:00
parent 41daff6538
commit f2b04d2e9d
15 changed files with 171 additions and 267 deletions
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outside.go
+36 -23
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@@ -23,7 +23,10 @@ const (
var ErrOutOfWindow = errors.New("out of window packet")
func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
// readOutsidePackets processes one received underlay packet.
// Message payloads are decrypted IN PLACE, so packet must stay untouched
// by the caller until the batcher for queue q has been flushed
func (f *Interface) readOutsidePackets(via ViaSender, scratch []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
err := h.Parse(packet)
if err != nil {
// Hole punch packets are 0 or 1 byte big, so lets ignore printing those errors
@@ -111,11 +114,11 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
// Relay packets are special
if isMessageRelay {
f.handleOutsideRelayPacket(hostinfo, via, out, packet, h, fwPacket, lhf, nb, q, localCache, meta)
f.handleOutsideRelayPacket(hostinfo, via, scratch, packet, h, fwPacket, lhf, nb, q, localCache, meta)
return
}
out, err = f.decrypt(hostinfo, h.MessageCounter, out, packet, h, nb)
out, err := f.decrypt(hostinfo, h.MessageCounter, packet, nb)
if err != nil {
if f.l.Enabled(context.Background(), slog.LevelDebug) {
hostinfo.logger(f.l).Debug("Failed to decrypt packet",
@@ -135,7 +138,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
case header.Message:
switch h.Subtype {
case header.MessageNone:
f.handleOutsideMessagePacket(hostinfo, out, packet, fwPacket, nb, q, localCache, meta)
f.handleOutsideMessagePacket(hostinfo, out, scratch, fwPacket, nb, q, localCache, meta)
default:
hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected message subtype seen", "from", via, "header", h)
return
@@ -150,8 +153,15 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
case header.TestReply:
// No-op, useful for the Roaming and connectionManager side-effects above
case header.TestRequest:
//recycle the input packet ciphertext as our output buffer
f.send(header.Test, header.TestReply, ci, hostinfo, out, nb, packet)
const maxCipherOverhead = 16 //todo we use this too often, needs a real importable const
const maxOverhead = header.Len + header.Len + maxCipherOverhead + maxCipherOverhead
if maxOverhead+len(out) <= len(scratch) {
f.send(header.Test, header.TestReply, ci, hostinfo, out, nb, scratch[:0])
return
} else if f.l.Enabled(context.Background(), slog.LevelDebug) {
hostinfo.logger(f.l).Debug("dropping oversized test request", "payloadLen", len(out), "from", via)
return
}
default:
hostinfo.logger(f.l).Error("IsValidSubType was true, but unexpected test subtype seen", "from", via, "header", h)
return
@@ -169,7 +179,7 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
}
}
func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender, out []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender, scratch []byte, packet []byte, h *header.H, fwPacket *firewall.Packet, lhf *LightHouseHandler, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
// The entire body is sent as AD, not encrypted.
// The packet consists of a 16-byte parsed Nebula header, Associated Data-protected payload, and a trailing 16-byte AEAD signature value.
// The packet is guaranteed to be at least 16 bytes at this point, b/c it got past the h.Parse() call above. If it's
@@ -177,9 +187,7 @@ func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender,
// which will gracefully fail in the DecryptDanger call.
signedPayload := packet[:len(packet)-hostinfo.ConnectionState.dKey.Overhead()]
signatureValue := packet[len(packet)-hostinfo.ConnectionState.dKey.Overhead():]
var err error
out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, signedPayload, signatureValue, h.MessageCounter, nb)
if err != nil {
if _, err := hostinfo.ConnectionState.dKey.DecryptDanger(nil, signedPayload, signatureValue, h.MessageCounter, nb); err != nil {
return
}
// Advance the replay window now that the frame is authenticated
@@ -217,7 +225,7 @@ func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender,
relay: relay,
IsRelayed: true,
}
f.readOutsidePackets(via, out[:0], signedPayload, h, fwPacket, lhf, nb, q, localCache, meta)
f.readOutsidePackets(via, scratch, signedPayload, h, fwPacket, lhf, nb, q, localCache, meta)
case ForwardingType:
// Find the target HostInfo relay object
targetHI, targetRelay, err := f.hostMap.QueryVpnAddrsRelayFor(hostinfo.vpnAddrs, relay.PeerAddr)
@@ -234,9 +242,11 @@ func (f *Interface) handleOutsideRelayPacket(hostinfo *HostInfo, via ViaSender,
if targetRelay.State == Established {
switch targetRelay.Type {
case ForwardingType:
// Forward this packet through the relay tunnel
// Find the target HostInfo //todo it would potentially be nice to batch these
f.SendVia(targetHI, targetRelay, signedPayload, nb, out, false)
// Forward this packet through the relay tunnel, rebuilding it in place.
// Encode overwrites the old outer header, and the new AEAD tag lands where the old one was
fwdBuf := packet[:0:len(packet)] // Cap to len(packet) to protect memory from a larger parent buffer
//todo it would potentially be nice to batch these
f.SendVia(targetHI, targetRelay, signedPayload, nb, fwdBuf, true)
case TerminalType:
hostinfo.logger(f.l).Error("Unexpected Relay Type of Terminal")
return
@@ -503,9 +513,16 @@ func parseV4(data []byte, incoming bool, fp *firewall.Packet) error {
return nil
}
func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, out []byte, packet []byte, h *header.H, nb []byte) ([]byte, error) {
var err error
out, err = hostinfo.ConnectionState.dKey.DecryptDanger(out, packet[:header.Len], packet[header.Len:], mc, nb)
// decrypt authenticates and decrypts a Message packet IN PLACE: the dst is
// packet[header.Len:header.Len], the exact-alias append pattern
// (ciphertext[:0]) that crypto/cipher.AEAD.Open documents, so the plaintext
// lands where the ciphertext sat and no separate plaintext buffer exists.
// On a failed auth the AEAD zeroes the would-be plaintext region (both
// AES-GCM and ChaCha20-Poly1305 do) but never writes outside it, so the
// other segments of a shared GRO receive row stay intact; nothing reads a
// packet after its decrypt fails. The returned slice aliases packet.
func (f *Interface) decrypt(hostinfo *HostInfo, mc uint64, packet []byte, nb []byte) ([]byte, error) {
out, err := hostinfo.ConnectionState.dKey.DecryptDanger(packet[header.Len:header.Len], packet[:header.Len], packet[header.Len:], mc, nb)
if err != nil {
return nil, err
}
@@ -580,7 +597,7 @@ func applyOuterECN(pkt []byte, outerECN byte, hostinfo *HostInfo, l *slog.Logger
}
}
func (f *Interface) handleOutsideMessagePacket(hostinfo *HostInfo, out []byte, packet []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
func (f *Interface) handleOutsideMessagePacket(hostinfo *HostInfo, out []byte, scratch []byte, fwPacket *firewall.Packet, nb []byte, q int, localCache firewall.ConntrackCache, meta udp.RxMeta) {
// RFC 6040 normal-mode combine: fold any outer CE mark stamped by the
// underlay into the inner header before firewall + TUN write. Other
// outer codepoints are advisory only — we keep the inner unchanged.
@@ -599,11 +616,7 @@ func (f *Interface) handleOutsideMessagePacket(hostinfo *HostInfo, out []byte, p
dropReason := f.firewall.Drop(*fwPacket, true, hostinfo, f.pki.GetCAPool(), localCache)
if dropReason != nil {
// NOTE: We give `packet` as the `out` here since we already decrypted from it and we don't need it anymore
// This gives us a buffer to build the reject packet in. With UDP GRO this is a single segment of a shared
// recvmmsg row whose capacity runs to the end of the whole row, so cap it to its own length (cap==len) to
// keep the reject builder from writing past this segment into the next, not-yet-processed coalesced segment.
f.rejectOutside(out, hostinfo.ConnectionState, hostinfo, nb, packet[:len(packet):len(packet)], q)
f.rejectOutside(out, hostinfo.ConnectionState, hostinfo, nb, scratch, q)
if f.l.Enabled(context.Background(), slog.LevelDebug) {
hostinfo.logger(f.l).Debug("dropping inbound packet",
"fwPacket", fwPacket,